# Any opinions / reviews on Gemtune APPJ PA1502A



## Mortus

hello 
  
 I am searching any opinion about this: Gemtune APPJ PA1502A  tube amp ,probably it is based on Miniwatt N3  APPJ PA0901A speaker amp
 and if so miniwatt has good review ,has anybody hear of it ? is it worth any attention ?
   

 Description


 Class-A single-ended triode  and 100% tube amplification.  Designed for resolution of fine musical details, expansive soundstage presentation, and lush tonal quality.
 6P6P Replaceable Tube: 6V6
 6N4 Replaceable Tubes: 12AX7, ECC83, ECC803
 Specifications:
 • Tube: 6N4+6P6PX2
 • Input: RCA Jacks
 • Input Impedance: 10K ohms
 • Input Sensitivity: 800mV
 • Output: 6.3mm Jacks
 • Output Impedance: 8 to 600 (Japan Z11-EI48*24 Output Transformers)
 • Output voltage: 18Vp-p
 • Frequency Response: 30-30Khz (+-1db)
 • Input AC Voltage: 100-250V AC
 • Power Consumption: 27W
 • AC: Standard IEC Jack with Fuse protection (2A Fuse)
 • Weight: 2.5kg
 • Dimensions: 160mm (w) x 134mm (d) x 125mm (h)
 • 0.13W/600 ohms   0.26W/300 ohms   0.5W/100 ohms   1W/32ohms


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## pr0ggy

Bump, would also like to hear some reviews.


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## yangian

Yes. Wondering about this:
 https://www.massdrop.com/buy/appj-1502a-tube-headphone-amplifier


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## ges11t

A review in Amazon is all I could find so far. Anyone else had any experiences with this?
  
http://www.amazon.com/gp/product/B00WSMIJBA?keywords=APPJ%201502A&qid=1444020203&ref_=sr_1_2&sr=8-2#customerReviews


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## kazcou

I bought this amp recently. The first think coming to your mind is : the amp is small and not heavy. But do not worry, it is working very well. You can turn to the max, the sound still remain very clean. And it have enough power for mostly all headphones on market.
  
 The first think you have to do is change the preamp tube. It a really bad tube ! Any 12AX7 will do a better job.
  
 The power tubes is ok. But you can swap them for cheap, I got a pair of nos mazda 6V6GT for 30€ and moderns tubes are also selling for the same price. With the Mazda, I got a little more detail and the music is a little more sweet also.
 You can also change the inter-stage coupling capacitors, put a 0,47uf 400v insteat of 0,1uf 400v, that make the amp more alive, with more deeper bass.
  
 The isound signature is neutral, so the general signature is more depending on you DAC.


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## yangian

kazcou said:


> I bought this amp recently. The first think coming to your mind is : the amp is small and not heavy. But do not worry, it is working very well. You can turn to the max, the sound still remain very clean. And it have enough power for mostly all headphones on market.
> 
> The first think you have to do is change the preamp tube. It a really bad tube ! Any 12AX7 will do a better job.
> 
> ...


 
 How is this compared to your other amplifiers? Thanks!


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## kazcou

yangian said:


> How is this compared to your other amplifiers? Thanks!


 
 For the price is not a bad amplifier, but you have plenty of chinese amplifiers for that price.
 the bass is ok
 the treble is missing the typical warmth of tube sound,
 the high is not enough airy
 the spacialisation is ok
 not enough details
 I think, I need a better preamp tube, currentlly I have only some NOS Balwind and they are not very good.
 I was thinking to use some NOS E188CC, but too bad the preamp tube heather is on 12,6V.
  
 Now I have to read thousand of pages for looking a good 12ax7.


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## yangian

kazcou said:


> For the price is not a bad amplifier, but you have plenty of chinese amplifiers for that price.
> the bass is ok
> the treble is missing the typical warmth of tube sound,
> the high is not enough airy
> ...


 

 Understand. Thank you!


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## yangian

kazcou said:


> For the price is not a bad amplifier, but you have plenty of chinese amplifiers for that price.
> the bass is ok
> the treble is missing the typical warmth of tube sound,
> the high is not enough airy
> ...


 

 Any new impression of this? Thanks!


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## CZ4A

This amp is on Massdrop right now. I'm seriously considering it as a second amp, especially for the price. I have plenty of 12A(whatever)7s and a few 6V6GTs to roll. I've read the stock tubes are underwhelming at best and the 6P6P tubes look bad, with the glue peeking above the base.
  
 Quote:


kazcou said:


> I think, I need a better preamp tube, currentlly I have only some NOS Balwind and they are not very good.
> I was thinking to use some NOS E188CC, but too bad the preamp tube heather is on 12,6V.
> 
> Now I have to read thousand of pages for looking a good 12ax7.


 
 You can probably roll some ECC81s or ECC82s if you have some. Less gain, though.
  
 Also, do you happen how many amperes the preamp tube heater puts out?


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## kazcou

I want to use some E188CC because I have somesiemens, valvo, telfunkun, tesla, amperex, sylvania in stock

I think i need to rebias the heather.






It will be hard since there is no trimpot, so you have to change add a resistor.

I am amazed of that my tubes are still alive


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## CZ4A

Ok, I understand better now about the tubes. 

I am not sure what you mean by "rebias the heather." By "heather" do you mean "heater?" Which contacts were you measuring? From the first picture it looks like the no. 4 or 5 pin contact but I can't see on the second picture.

In any case, I've put down my ducats for a 1502a on Massdrop. Should be interesting to compare with my Sunrise III.


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## braaam

Here are some impressions by E8ArmyDiver from different threads. He's comparing it with a Schiit Vali 2 amp and driving the HE-400i. 
  
post #6416
post #273
post #385
  
 I decided to go for this same combo. Both 400i and appJ are on the way.
  
 For fellow european's: the appJ's are sold on amazon.de for very reasonable prices at the moment and in stock (+ free shipping in the EU). I got mine for 175 euro's.


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## braaam

APPJ is here! It's been breaking in for about 7 hours.

the original pre-amp tube isn't that terrible IMO, but lacks in definition and has a bit muddy bass. It is holding back the potential of the amp.

I've been rolling some oldies. Some first impressions

Mazda ecc82: lean bass, narrow soundstage, warm mids

Dario/Philips miniwatt ecc82: well balanced sound, open and detailed, much bigger soundstage, very enjoyable. 

The miniwatt is the clear winner for now. Makes for a good match with the HE-400i.


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## canthearyou

braaam said:


> APPJ is here! It's been breaking in for about 7 hours.
> 
> the original pre-amp tube isn't that terrible IMO, but lacks in definition and has a bit muddy bass. It is holding back the potential of the amp.
> 
> ...


 
 Cool! Will try to find one.


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## braaam

canthearyou said:


> Cool! Will try to find one.




The philips miniwatt 12ax7's are also nice. I have a Made in India one and it has similar properties as the 12au7 Dario. It seems Philips had great quality control for the miniwatt's


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## a44100Hz

braaam said:


> The philips miniwatt 12ax7's are also nice. I have a Made in India one and it has similar properties as the 12au7 Dario. It seems Philips had great quality control for the miniwatt's




Any volume issues with your amp? My volume pot only changes the right channel volume most of the time (with left channel at max).


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## braaam

a44100hz said:


> Any volume issues with your amp? My volume pot only changes the right channel volume most of the time (with left channel at max).




No, no problems here.. That's annoying to say the least.


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## canthearyou

Just received mine. No power cord. The tubes have seen better days. The sound with stock tubes and zero burn-in is very surprising. Very clear and maybe a slight bump in mid-bass compared to Gustard H10. I had a new tube on order but it was cancelled due to stock issues. 

Listening through 400i.


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## CZ4A

canthearyou said:


> Just received mine. No power cord. The tubes have seen better days. The sound with stock tubes and zero burn-in is very surprising. Very clear and maybe a slight bump in mid-bass compared to Gustard H10. I had a new tube on order but it was cancelled due to stock issues.
> 
> Listening through 400i.


 
 I've read elsewhere that the stock 6P6P (6V6) tubes are poorly-made from the factory.
  
 Anyways, the Massdrop group buy failed, so I didn't end up getting the APPJ. I'm still interested in it.


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## canthearyou

cz4a said:


> I've read elsewhere that the stock 6P6P (6V6) tubes are poorly-made from the factory.
> 
> Anyways, the Massdrop group buy failed, so I didn't end up getting the APPJ. I'm still interested in it.


 
 I paid $216 from Amazon. As of this very moment I am very pleased with the amp. I can't wait to try some different tubes.


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## kazcou

a44100hz said:


> Any volume issues with your amp? My volume pot only changes the right channel volume most of the time (with left channel at max).


 
 No issue here, maybe a defective potentiometer.


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## braaam

canthearyou said:


> I paid $216 from Amazon. As of this very moment I am very pleased with the amp. I can't wait to try some different tubes.




Good to hear! Can you compare the sound to the H10?

The Miniwatt vintage tubes are quite nice with it. Good resolution, revealing with a good soundstage. Not the warmest, more towards natural.


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## kazcou

Full reissue Tung sol 6V6GT + 5751 is also a good choice for those who is looking for something more neutral with a very good soundstage.


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## a44100Hz

I'm using these tubes: http://www.ebay.com/itm/150471341660 and http://www.ebay.com/itm/301233066989
  
 Love them with the 400i. It's nice to be able to purchase new tubes and not roll the dice with NOS.


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## braaam

a44100hz said:


> I'm using these tubes: http://www.ebay.com/itm/150471341660 and http://www.ebay.com/itm/301233066989
> 
> Love them with the 400i. It's nice to be able to purchase new tubes and not roll the dice with NOS.




It is. But the thrill of discovering a vintage gem gets my adrenaline going.. financially this doesn't make any sense though 

Anyone tried the current Tung-Sol? They get very favourable reviews, see also this comparison table.


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## chellity

I actually made an account for this amp  like many others it seems, I tried the vali 2 with the 400i but found myself wanting something a little different.  can't wait to compare these two amps side by side...i'm rooting for the 1502a, and already have a vintage miniwatt headed my way.  the vali 2 was like the equivalent of putting an instagram filter over an image....not quite as tubey as I'd like, but also with none of the side effects that I was ready for.  now, about those 6v6gts...


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## braaam

chellity said:


> I actually made an account for this amp  like many others it seems, I tried the vali 2 with the 400i but found myself wanting something a little different.  can't wait to compare these two amps side by side...i'm rooting for the 1502a, and already have a vintage miniwatt headed my way.  the vali 2 was like the equivalent of putting an instagram filter over an image....not quite as tubey as I'd like, but also with none of the side effects that I was ready for.




Welcome to the club chellity! I hope you'll like the combo - keep us posted about your experience!

I've been rolling some more tubes. The Miniwatt holds up very well. Especially the imaging and soundstage is the best of the tubes that I tested.

There is another gem that I got my hands on, but it is a lot harder (and more expensive) to find. It's the Mazda belvu 5 star triple mica 6201/12at7wa from the 60s.

This Mazda is a bit more forward sounding than the Miniwatt and has the deepest bass extension/response that I've heard. The mids are smooth and lush and the highs are sparkling without being harsh or sibilant. It suits many different music styles and keeps me hooked to my music for hours and hours. It's addictive.

Some other great performers which you can find for reasonable prices (all tested with the 400i):

- Raytheon 12at7wa triple mica black plates from the late 50s or early 60s (these are very special for certain music, they have a beautiful warmth. great for jazz, brass instruments, female vocals).
- RCA conn 12au7a clear top (well balanced, smooth mids, good dynamics. Very enjoyable for different types of music)
- Sylvania 12at7wa triple mica gold lettering (good soundstage, lush mids and highs)




> now, about those 6v6gts




I have tried some vintage RCA's which showed a slight impovement in the bass but introduced harshness and sibilance in the treble. Overall the stock chinese tubes are holding up well to these. Going to try some different ones soon.


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## a44100Hz

chellity said:


> I actually made an account for this amp  like many others it seems, I tried the vali 2 with the 400i but found myself wanting something a little different.  can't wait to compare these two amps side by side...i'm rooting for the 1502a, and already have a vintage miniwatt headed my way.  the vali 2 was like the equivalent of putting an instagram filter over an image....not quite as tubey as I'd like, but also with none of the side effects that I was ready for.  now, about those 6v6gts...


 
  
 I'm using that same setup (400i and 1502A) and I recommend the tubes I mentioned a few posts up, though I won't say I haven't been curious about something like a Gold Lion. But for the price you can't go wrong with those (relatively inexpensive) new JJ and Mullard tubes, the soundstage is wider and the sound more "real" sounding than any tubes I've tried with the Vali 2 so far. I have not ordered from this site yet but it has some brief descriptors if you are new to 12AX7 tubes like I am: http://www.tubesforamps.com/best-12ax7-review


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## canthearyou

Installed the new tubes I ordered the other day. Electro Harmonix 6V6GT and Reissue Mullard 12AX7. With about 6hrs of burn in this is my opinion: slightly larger soundstage, BUT highs are very harsh, to the point of sibilance. Gonna power down and let it cool off and try the original power tubes.


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## braaam

canthearyou said:


> Installed the new tubes I ordered the other day. Electro Harmonix 6V6GT and Reissue Mullard 12AX7. With about 6hrs of burn in this is my opinion: slightly larger soundstage, BUT highs are very harsh, to the point of sibilance. Gonna power down and let it cool off and try the original power tubes.




Had a similar experience with vintage RCA 6v6's. Very shrill highs compared to stock. Maybe yours need more burn in?


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## a44100Hz

canthearyou said:


> Installed the new tubes I ordered the other day. Electro Harmonix 6V6GT and Reissue Mullard 12AX7. With about 6hrs of burn in this is my opinion: slightly larger soundstage, BUT highs are very harsh, to the point of sibilance. Gonna power down and let it cool off and try the original power tubes.


 

 Hmm, I'm using JJ 6v6 tubes with that same Mullard and I am not having trouble with harsh highs. Which headphones?


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## canthearyou

a44100hz said:


> Hmm, I'm using JJ 6v6 tubes with that same Mullard and I am not having trouble with harsh highs. Which headphones?




Both 400i and K7XX. I swapped the 6V6 back to stock and it's warming up now. Gonna give it a listen tonight.


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## a44100Hz

canthearyou said:


> Both 400i and K7XX. I swapped the 6V6 back to stock and it's warming up now. Gonna give it a listen tonight.


 

 Give me an example track of that harshness? I'm curious. I'm listening on the 400i right now.


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## canthearyou

a44100hz said:


> Give me an example track of that harshness? I'm curious. I'm listening on the 400i right now.




It was every single song I threw at it. I'm now running the stock power tubes and new reissue Mullard 12AX7 and it sounds pretty good. 

This is a really bright tube amp IMO.


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## chellity

well, I just got mine in a few hours ago and I'm very happy with it already  definitely better than the vali 2, with a he-400i at least.  the vali had like a really full sound, at the cost of instrument separation and soundstage.  it was also more sterile than I hoped for...   even with the stock tubes in this, I can already hear a similar clarity, but with a much improved soundstage and a tubier tone.  can't wait to get to tube rolling on this thing!  
  
      I had ordered a miniwatt ecc83, but apparently I won the tube lottery, and the seller broke it...so he's sending me a west german telefunken (dyanco branded) ecc83 from the early 60s, and a vintage amperex (fisher branded) ecc83 for the price of one miniwatt ecc83!  both tested/balanced and with the factory markings.   not a bad deal, I hope.  I also snagged some rca 6v6gts at a good price, so I hope those will work too.  couldn't be happier with my first real headphone set up!


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## Terrynj

I've had my 1502a for about a week now. I have a HE400s and a 400i, and a Soundblaster E5 DAC/AMP. I stream TIDAL out of my laptop USB into my E5. I couldn't resist getting the tube amp because I was having so much fun with my new planar headphones. Believe it or not, but I prefer my modded 400s over the 400i. The 400s has focus pads A and running no grills right now. Ive tried the grill mods on the 400i, but didn't think it made enough difference, so Ive got the stock grills back on.
 The 400s's are very open and airy and has a much more "live" feel to it. The 400i's are very detailed and smooth, but not as open as the 400s, so I always end up with the 400s's on my head...
  
 The Soundblaster E5 is a little jewel. It has an app for my phone Galaxy s6 EDGE and laptop, so I can do OTG, it will do Blue Tooth, dual HP jacks, and plenty of power for either HP...the 400i take about 10% more volume. I think it sounds very very good.With the app I can control their SBX feature which is basically a loudness button with full control. I use for bass adjustment where it even has a frequency crossover where I can bring out the sub-bass in both HPs...I dont see much difference in the bass between the two HPs now. There is also an Equalizer....I dont use a whole lot of adjusting on these phones because they are already so accurate, they don't take much.
  
 So I am running my 1502a out of the Line Level feed out of the E5. The initial impression was the 1502 was rather veiled and not as open compared to the E5. After running the 1502 for a week now, it has gotten much better and is closer to the E5, but still not quite as airy and still a little muffled. I do enjoy the overall sound from the 1502 though.
  
 So I know nothing on tubes and I have been studying quite a bit. I found and ordered a NOS Sylvania JHS 5751 for my pre-amp, I am very excited to see what this does...should get it around Friday. I am  also studying up on the power tubes, but that seems to be a little scarier because I am looking a little deeper than the standard 6V6GT re-issue. I love the look of some old 6V6G ST coke bottle tubes, but dont know poop about making sure the voltages match up with the amp or any other unknowns. The 1502 does Auto-Biasing, so I dont know if that will solve any issues. Now I have found the 7408 tubes that seems to be an Industrial version of the 6V6GT, but I have read some very cool things about them from the Guitar guys..this a cut from a guy rolling a Harmon Kardon amp..
  
_"Hey folks, I have been messing with my new HK a300 tube amp. It is a 6v6 PP amp. Sound very good. I thought I would give it a try with several of the different tube sets I have. So far I have only tested three different sets. _
  
_Ist up was a set of magnavox 6v6gt's made in japan. The clarity is very good. The highs and moids are very pronuonced. The lows are tight, but lacking. 

2nd up was a set of wesinghouse 6v6gt's. They were similar to the magnavox. They had a l;ittle better mids, a little less on the highs, and bas was about the same.

3rd up was a set of HK 7408 tubes - WOW! The highs are very good, the mids are rich and warm, but the bass is very powerfull. The first two sets would not push the woofer to its ecursion limit. The hk's do so with ease."_
  
So I have no idea how these would react in the 1502, from everything I've read, the 7408 is the same as a 6V6GT, but I dont want to stick a $100 worth of tubes and watch them go up in smoke (or the amp). 
  
Any suggestions for a tuber nuber....Should I just buy a $40 set of re-issue 6V6GT's and be happy, or do you think it would be OK to experiment?
  
Thanks in advance for any suggestions


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## a44100Hz

Can anyone attest to how much the 6V6 power tubes influence the sound compared to the 12AX7 tube?


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## canthearyou

a44100hz said:


> Can anyone attest to how much the 6V6 power tubes influence the sound compared to the 12AX7 tube?




Greatly in my experience.


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## a44100Hz

canthearyou said:


> Greatly in my experience.




I would expect the opposite but I don't know why I had that preconception. Which have you tried?


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## canthearyou

a44100hz said:


> I would expect the opposite but I don't know why I had that preconception. Which have you tried?




Electro Harmonix 6V6GT. It made the highs very harsh. I haven't done a full burn in yet, but it is tough to listen to.


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## braaam

terrynj said:


> So I know nothing on tubes and I have been studying quite a bit. I found and ordered a NOS Sylvania JHS 5751 for my pre-amp, I am very excited to see what this does...should get it around Friday. I am  also studying up on the power tubes, but that seems to be a little scarier because I am looking a little deeper than the standard 6V6GT re-issue. I love the look of some old 6V6G ST coke bottle tubes, but dont know poop about making sure the voltages match up with the amp or any other unknowns. The 1502 does Auto-Biasing, so I dont know if that will solve any issues. Now I have found the 7408 tubes that seems to be an Industrial version of the 6V6GT, but I have read some very cool things about them from the Guitar guys..




I've tested that Sylvania with my 400i. Very smooth and warm. Great for vocals, piano's, acoustic music. Definitely a nice upgrade to the stock tube IMO. Compared to the Mazda 5 star they are a bit less resolving/articulate.

I think it's a bit tricky to follow the advice of guitar guys since the tubes are driven harder usually which will distort the sound intentionally and their setups can differ massively from one amp/speaker to the other.

Here's some more info on the 7408 from http://www.audiotubes.com/6v6.htm



> 7408 This is the industrial version of the 6V6. As far as I have seen, only glass versions were made, but it is possible there are some metal jacket types out there, but their appearant rarity leaves them out of consideration here. I have seen both clearglass and greyglass versions. They should perform on par with the military spec types, and are absolutely interchangeable with any 6V6 type. They were never plentiful, and today are rather hard to find. If you are replacing a 7408 and I am out of stock, any of the military spec tubes will work nicely as a substitute.


 

I have some NOS Russian 6V6's and Visseaux (these should be very nice) on the way.


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## braaam

chellity said:


> well, I just got mine in a few hours ago and I'm very happy with it already  definitely better than the vali 2, with a he-400i at least.  the vali had like a really full sound, at the cost of instrument separation and soundstage.  it was also more sterile than I hoped for...   even with the stock tubes in this, I can already hear a similar clarity, but with a much improved soundstage and a tubier tone.  can't wait to get to tube rolling on this thing!
> 
> I had ordered a miniwatt ecc83, but apparently I won the tube lottery, and the seller broke it...so he's sending me a west german telefunken (dyanco branded) ecc83 from the early 60s, and a vintage amperex (fisher branded) ecc83 for the price of one miniwatt ecc83!  both tested/balanced and with the factory markings.   not a bad deal, I hope.  I also snagged some rca 6v6gts at a good price, so I hope those will work too.  couldn't be happier with my first real headphone set up!




You are very very lucky! That Amperex is probably made in Holland so you'll get something comparable to the miniwatt AND the German analytical sound to try.

I tried some second hand 50s RCA's but didn't like them - very harsh and sibilant. Maybe I got some bad ones..


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## Terrynj

braaam said:


> I've tested that Sylvania with my 400i. Very smooth and warm. Great for vocals, piano's, acoustic music. Definitely a nice upgrade to the stock tube IMO. Compared to the Mazda 5 star they are a bit less resolving/articulate.
> 
> I think it's a bit tricky to follow the advice of guitar guys since the tubes are driven harder usually which will distort the sound intentionally and their setups can differ massively from one amp/speaker to the other.
> 
> ...


 
 I actually mis-spoke on the thread being from a guitar forum, he was re-building a Harmon Kardon a300 integrated Tube amp. The tubes he was speaking of were the Harmon Kardon own brand of 7408/6V6GT tubes and evidently made by RCA. I have found a 2 matched RCA HARMON KARDON 7408 Tubes, so I was just very interested in them. I am very familiar with HK and seems if they were using them in the home audio amps, I figured they should be worth a look.
	

	
	
		
		

		
			




  
 I am glad to see you have some experience with the 5751 and appreciate the input, what the full number on the Mazda?
  
 Thanks for the info Braam!


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## braaam

terrynj said:


> I actually mis-spoke on the thread being from a guitar forum, he was re-building a Harmon Kardon a300 integrated Tube amp. The tubes he was speaking of were the Harmon Kardon own brand of 7408/6V6GT tubes and evidently made by RCA. I have found a 2 matched RCA HARMON KARDON 7408 Tubes, so I was just very interested in them. I am very familiar with HK and seems if they were using them in the home audio amps, I figured they should be worth a look.:bigsmile_face:
> 
> I am glad to see you have some experience with the 5751 and appreciate the input, what the full number on the Mazda?
> 
> Thanks for the info Braam!




It's the Mazda Belvu 5 star triple mica 12at7wa. Fairly neutral, great resolution, pace and bass response. Very addictive. 

Seems the 6v6gty is similar to those 7408s. I found a NOS set of those for around €40 here in Europe.


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## Terrynj

braaam said:


> It's the Mazda Belvu 5 star triple mica 12at7wa. Fairly neutral, great resolution, pace and bass response. Very addictive.
> 
> Seems the 6v6gty is similar to those 7408s. I found a NOS set of those for around €40 here in Europe.


 
 Thanks Bram! I am a tweak at heart, so I love having all the options and the research involved in finding our "Diamonds in the rough" .... it is really fun!
 Thank you for all your sharing! It is hard when your a Nube and you just dont have any practical experience....having experience shared with you helps so much!


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## braaam

terrynj said:


> Thanks Bram! I am a tweak at heart, so I love having all the options and the research involved in finding our "Diamonds in the rough" .... it is really fun!
> Thank you for all your sharing! It is hard when your a Nube and you just dont have any practical experience....having experience shared with you helps so much!


 

 Glad I found a kindred soul around here! Let's make sure we find the very best tubes for the Appj/400i/s combi


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## canthearyou

braaam said:


> Glad I found a kindred soul around here! Let's make sure we find the very best tubes for the Appj/400i/s combi


 
 Don't leave me out. I'll be testing a few more tubes very soon. The next ones I think I'm gonna try are the Genalex Gold Lions for the power tubes.


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## braaam

canthearyou said:


> Don't leave me out. I'll be testing a few more tubes very soon. The next ones I think I'm gonna try are the Genalex Gold Lions for the power tubes.




Interesting. I'll be checking out some new issue Tung Sol 6V6s. Will be nice to know how they perform against the Genalex (and vintage tubes).


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## a44100Hz

Right now I am using the following:

JJ 6V6 (new, matched)
Reissued Mullard 12AX7 (new)

Which sounds great, is readily available, and was relatively inexpensive. 

I'll be getting the following soon:
Genalex Gold Lion 12AX7 (new)
RCA JRC-5751 (NOS)

After I've tried keeping the power tubes the same and changing out the preamp tube, I'll try a new pair of power tubes based on what you guys recommend.


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## Terrynj

braaam said:


> Had a similar experience with vintage RCA 6v6's. Very shrill highs compared to stock. Maybe yours need more burn in?


 
 Now I'm really confused...looking at NOS tubes at the Audiotubes.com website, Brent Jessee gives a thorough description of all 6V6 versions. In the description of the 1950's RCA GreyGlass 6v6gt's he has for sale at the bottom of the page, he makes this statement..
 http://www.audiotubes.com/6v6.htm
  
  
 "* Used tested good White Box. Very popular vintage tube. Difficult to keep in stock as supplies dwindle and demand soars. Even used ones are much better than the junk being made today. Matched pairs are just $50.00"*
  
 So to me, that is what makes this process so hard, is the different opinions you will find as you search. You read a definitive statement on a commercial web-site that deals with these tubes everyday, and then you have a trusted source like Braaam that has tried some OLD RCA's and it was a bad experience. Maybe the tubes were bad? If they were tried on the 1502A, then are there compatibility issues with some makes of tubes?
  
 He says none of the new tubes are any good, but I also had looked at the Genalex- Gold Lion 6v6gt and still see them as an option... a44100hz has the new JJ 6v6gt's and he's happy with them??
  
 I am also still looking at what power tubes I want to try. I am currently looking at the 1950's RCA....found some pairs on ebay that I am watching. E8armydiver recommended NOS RCA 6v6gt's, 1950's era to me, so that is why it concerns me Bram had an issue with them?
  
 I am also still considering the Harmon Kardon 7408 tubes. HK has a decent reputation of making quality amplifiers, so i would think a tube made for their more serious equipment, would be a good performer.
  
 I really would like to try the 6V6G ST coke bottle tubes...but those go back to the 1930's, and that may be tougher to have success with because of their age (construction and design)...but they look awesome!
 http://www.tubemonger.com/MARCONI_CANADA_1950s_JAN_6V6G_Smoke_Glass_ST_NIB_p/935.htm
  
 I re-read this before I sent it out, and it sounds more like a rant than a question or a statement! lol    
	

	
	
		
		

		
			





 I think sometimes you just have to let things soak before you answer become more clear. It may be Tuesday before I get my preamp tube I ordered (Sylvania JHS 5751), so I may just wait till then and see where I am at.


----------



## braaam

It's possible the RCA's where past their prime although the seller stated that they tested good. It's a bit of a lottery, and they are used tubes (not NOS). Also, I will do some more testing with different pre-amp tubes.

I'll be testing some vintage brown base RCA 6V6GTY's soon to find out if they perform better.

Those coke bottles look awesome!


----------



## Terrynj

braaam said:


> It's possible the RCA's where past their prime although the seller stated that they tested good. It's a bit of a lottery, and they are used tubes (not NOS). Also, I will do some more testing with different pre-amp tubes.
> 
> I'll be testing some vintage brown base RCA 6V6GTY's soon to find out if they perform better.
> 
> Those coke bottles look awesome!


 
 Yeah, I am sure with the age of these tubes, I am surprised at how well they still seem to be performing, so I am sure there are some that may test good, but have other issues.
 The GTY's are supposed to be very good...I have been checking those out too. I am excited to see how they work for you..... I'm not sure if I like the brown base, but it is very retro looking. 
 One of the things I am still trying to find out is the biasing on this amp. The 1502A does "Auto-biasing"?? So does that mean I can stick a 6v6g ST coke bottle tube in it from the 1930's and not have to adjust anything?? I love the coke bottles too, but dont want to redesign the whole amp with resistors because there are no bias pots on the motherboard. I think is the biggest challenge for me with the 1502A, is what our liberties are with this amp.what are the restrictions?


----------



## canthearyou

terrynj said:


> Yeah, I am sure with the age of these tubes, I am surprised at how well they still seem to be performing, so I am sure there are some that may test good, but have other issues.
> The GTY's are supposed to be very good...I have been checking those out too. I am excited to see how they work for you..... I'm not sure if I like the brown base, but it is very retro looking.
> One of the things I am still trying to find out is the biasing on this amp. The 1502A does "Auto-biasing"?? So does that mean I can stick a 6v6g ST coke bottle tube in it from the 1930's and not have to adjust anything?? I love the coke bottles too, but dont want to redesign the whole amp with resistors because there are no bias pots on the motherboard. I think is the biggest challenge for me with the 1502A, is what our liberties are with this amp.what are the restrictions?




Very good question. I'm eagerly awaiting the answer.


----------



## a44100Hz

From Army's review: "This is an Auto Biasing, Solid State Rectified,Class A Single Ended Triode(12AX7) driving a pair of Triode Strapped 6V6 Power Tubes."

 http://www.head-fi.org/products/appj-pa1502a-6n4-6p6px2-tube-headphone-amplifier-black/reviews/14901


----------



## Terrynj

a44100hz said:


> From Army's review: "This is an Auto Biasing, Solid State Rectified,Class A Single Ended Triode(12AX7) driving a pair of Triode Strapped 6V6 Power Tubes."
> 
> http://www.head-fi.org/products/appj-pa1502a-6n4-6p6px2-tube-headphone-amplifier-black/reviews/14901


 
 Hi a44100hz!   Yes, I read that, but I just wanted to find out for sure before I start sticking some of these "variations" in my new amp...smoking $80 set of tubes or my amp would be a crusher. Ive been chatting with E8armydiver since I bought my amp, I asked him these questions a few days ago, but I haven't heard back from him yet...but he's working nights right now...so I'll just wait. I guess Im being overly cautious, but I find it better to ask now, then after Ive smoked my new toy!
	

	
	
		
		

		
		
	


	



  
 Have you gotten in your Genalex Gold Lion tubes yet? I looked at those hard and would be my fall back to ...those look like pretty solid tubes!
 Post up when you get them! Anxious to hear!


----------



## a44100Hz

I'll have a gold lion 12AX7 on Monday, most likely. I've never gain-adjusted a tube amp so if you're supposed to do it, I didn't have to. Like the Vali 2, I've just been swapping tubes in without changing any internals.


----------



## Terrynj

a44100hz said:


> I'll have a gold lion 12AX7 on Monday, most likely. I've never gain-adjusted a tube amp so if you're supposed to do it, I didn't have to. Like the Vali 2, I've just been swapping tubes in without changing any internals.


 
 OK, that's good to know...I'm a newbie... I just got my amp a week ago, and never even looked at a tube until 2 weeks ago. I have a technical background.... I maintained IT rooms for hospitals in the 80's, and sold corporate servers, networks...also did Home Audio Video...Home theaters etc up till the early 2000's, but I'm not a build my own pre-amp kinda guy...dont know component level stuff so much...just being cautious. I dont know this new stuff at all...but I love it!
  
 Thanks a44100hz!


----------



## a44100Hz

Haha sure; I've only been using tubes for a few weeks. The sound is so good though!

 Try this: www.audiotubes.com/12ax7.htm

 Scroll down to "*OK, SO TELL ME HOW THEY SOUND!!*"


----------



## Terrynj

a44100hz said:


> Haha sure; I've only been using tubes for a few weeks. The sound is so good though!
> 
> Try this: www.audiotubes.com/12ax7.htm
> 
> Scroll down to "*OK, SO TELL ME HOW THEY SOUND!!*"


 
 You know, when you posted this website, I thought..I've seen this before, but I saw the 6V6 side, which is what I'm looking at now, but this is an awesome Pre-amp write up I wished I had noticed this before...I really appreciate you pointing me this way...really good info.
  
 Not sure if you were kidding about the 2 week thing, but yeah..about 2 weeks. I've been listening to music since the 60's...I love music......I went to all the concerts back in the 70's... like I said before, I did Custom Home Audio Video for 15 years .....I've never heard anything like what I heard when I got my HE400s's on December 10th...my life changed! I wanted some new BT HPs and couldn't decide between 2 -$150 Blue tooth HP's...really was a hard decision. I told my wife that what I really wanted was some good headphones and found Head-fi.org, and made the leap and bought the HE400s headphones..omg....omg..I have never heard anything like the sound I heard from those.....
  
 So now my budget expanded...I bought a new DAC/AMP, the soundblaster E5 to replace my Fiio E11 (my hp's were VMODA M80's), the HE400i's went on sale..I bought those too..then I start getting drawn in by the tubers. I read E8armydivers stuff on the 1502a...bought that and got it on January 14.....24 hours in the day is not enough for me to sit here and search through all my music...I've modded both headphones and it is unbelievable the sound I am getting. Dont take this the wrong way, but young people do not understand how valuable the FLAC files are we have access to. I stream TIDAL and it is incredible when you add the Planar HPs. 
  
 Back in the day, manufactures would not release  high resolutions versions of their music, movies, etc... for fear of people copying and re-selling..now with the the world turning to streaming....we have access to stuff that i never imagined. Even on TV, I have a large 4k tv and I HAVE NEVER seen anything like what I see now. I stream HD movies and the details are riduclous... I mean ridiculous...we are watching old movies...the Empire Strikes Back. Back to the Future 1..and you can see the eyelashes on the actors...friggin stunning and this is on a 75" TV... 
  
 So now I have this same resolution in audio!!!!! I am sorry, but I can not contain myself about this world which is now the norm. The tube world is now a way of tweaking and enjoying what we have before us. We have the highest resolution sources, the best DAC/AMP scenarios, and the best display devices in these HP's .....which duplicating with Speakers and Amps is Mondo expensive..and probably still wont be as goods as my HE400s's. Plus too, Large sound systems are very intrusive and quiet HPs's lets us enjoy without offending the neighbors.
  
 Heres a change of pace...anytime I get into a subject i always look at the best, and see what I can afford from there. One product I always remembered from the past was McIntosh amps...so i thought..what tubes do they use? I found some interesting pages....this is a company that refurbishes antique high end amps...they list the tubes they use...guess what! 12AX7A, 12AU7, and on down, then their power tubes..6L6...heres some links....look at the tubes they use...
  
 http://vintagevacuumaudio.com/product/1-pair-of-mc30-mcintosh-tube-amps-newly-restored-one-year-warranty/
  
 Look down the list, this is a historic website for Mac Amps, you will see tubes used in McIntosh tube amps
 http://www.roger-russell.com/amplif2.htm#mc2155
  
 This is a great article on how bands used McIntosh amps
 http://www.positive-feedback.com/Issue77/vintage_mcintosh_experience.htm
  
 And this is fun to watch...the making of a McIntosh 275 amp...gorgeous!
 https://www.youtube.com/watch?v=2HgS6gvokEI
  
 Sorry to get off topic, but to me ....this is on topic for the big picture on what we are doing!
  
 Bon 'Appetit my friends, the eating has never been better!


----------



## a44100Hz

Your enthusiasm is infectious  and I agree. I had a really fun evening of just listening to music. I can finally appreciate the improvement in immersion that FLAC brings, so I've been trying to collect lossless files wherever I can. The difference from 192 (YouTube HD) or even 320 to FLAC is noticable now for albums I'm familiar with. Not sure if it's my ears adapting or if the audio chain is finally up to snuff or a bit of both. Lossless adds that extra touch of realism to voices, for example, that makes some records sound better than I ever expected their recordings were. I just listened to Thriller. Felt like I was sinking into the music. I felt giddy the entire time. Today was a good audio day.


----------



## Terrynj

a44100hz said:


> Your enthusiasm is infectious
> 
> 
> 
> ...


 
 No, you are correct about the FLAC being better. I see MP3 people saying there is no difference between MP3 and FLAC which is ridiculous. MP3's are compressed..game over. I do photography and I shoot RAW...uncompressed..I can do anything with the file uncompressed..jpegs you cant do anything...color temps aren't correct? Your screwed.
  
 Here is what people miss..any transfer medium is only as good as the source. I can make a Blu-ray copy of a Polaroid picture and the quality will never be any better than the polaroid..So A FLAC copy of a not so good original will not be good. A MP3 copy of a high resolution original, will be very good...but FLACs will be master copies of the original...which is the best you can get. (or as close as you can easily get)
  
 Yes to the music.. I listened to Maniac Mechanic and La grange from ZZ top and my mouth was agape...I'm from Texas and I have listened to this my whole life...it was like I never heard it before!
 I listened to thriller too....awesome
  
 Heres a couple that I have picked as best of show..Amos Lee ..."Sweet Pea" and Keb'mo..."Move" off the Bluesamerica album...Alice In Chains, Unplugged is an awesome recording..any song..
  
 EDIT: I will add a caveat about MP3 files...I have heard some that are very close to FLAC doing A/B'ing... i was speaking of when space is not a concern..or bandwidth. I am speaking to what I play for serious listening. Disc space is cheap and external 1 Tb hard drives can be had for $60...but dont stream FLAC on your Data plan unless its unlimited, the files are big. But to pick up some of the nuances we are talking about with this gear and tubes, you need the best sources you can get...I know I am preaching to the choir here...especially on this forum/this site. This statement is just for those that think there's no difference...


----------



## braaam

I think what people say is they don't _hear _a difference between well encoded mp3's and lossless files. And they are right - most people can't reliably tell the difference in blind tests.
  
 When conversions are done throughout the audio chain it could matter if the original was uncompressed or already compressed, especially for up/downscaling. Apple TV upscales 16/44 sources to 16/48. The effect is very substantial with compressed music (bad). 
  
 Personally, in my audio chain, I haven't yet noticed differences between compressed 256kb AAC and uncompressed/high resolution audio. I've tried Tidal and I didn't hear a difference compared to the same songs in Apple Music. That, off course, could also be attributed to the chain itself which consists of an iPhone that streams music through airPlay directly to a Pioneer Elite receiver that i use as a DAC, then into a 5 meter interconnect that connects to the APPJ, which outputs to the stock 400i cable/headphones. 
  
 About the 6V6G vs 6V6GT, they have the same characteristics electronically. The only difference is the glass tubular (GT) vs glass (G) vs glass tubular yellow (GTY) etc. In other words, all tubes that start with "6V6" should be fine. (source: http://www.fenderforum.com/forum.html?db=&topic_number=489146)
  
 The only possible issue off course is the shape of the "G". It won't fit everywhere.


----------



## Terrynj

braaam said:


> I think what people say is they don't _hear _a difference between well encoded mp3's and lossless files. And they are right - almost no one is able to dell the difference in most of the cases. I think what you mean is that when there are conversions done throughout the audio chain it could matter if the original was uncompressed or already compressed. Apple TV resamples 16/44 sources because it upscales to 16/48. The effect is very substantial (bad) there.
> 
> Personally, in my audio chain, I haven't yet noticed differences between compressed 256kb AAC and uncompressed/high resolution audio. I've tried tidal and I didn't hear a difference compared to the same songs in Apple Music. That, off course, could also be attributed to the chain itself which consists of an iPhone that streams music through airPlay directly to a Pioneer Elite receiver that i use as a DAC, then into a 5 meter interconnect that connects to the APPJ, which outputs to the stock 400i cable/headphones.
> 
> ...


 
 I traded in my iphone for a samsung, so I 've not heard itune music in quite some time , so i'll stand corrected on that. I have always used Spotify to stream, and with the gear I used then, it was great. But since I got my planars, the difference between the two are plain to me. I will still go back and forth between Tidal and Spotify, listening to the same song, and I dont mind paying the extra money for Tidal.
  
 When I was using itunes i had the iphone 4s, which had line level out through the charging connector....that I could go into a DAC which was great...the newers ones (iphone 5) went to the small charging connector, which I could no longer get LL audio ( they want you to use the Blue Tooth), had to use the HP jack which doesn't work for what I was doing since the phones DAC was being used....On my Samsung, I can use the USB OTG feature of my E5 DAC/AMP which sounds very close to what I get our of my laptop. Going through my HP jack on my phone, into my E5, to my 400s or 400i, removes the gain I get from Tidal... both Spotify and Tidal sound the same to me then.
  
 the newer Samsung s7 coming out, supposedly has a completely overhauled DAC/AMP setup in for people like us that are using better than $30 ear buds... I think that will be a trend from here on out with manufactures.
  
 thanks for the info on the tubes, I am just being cautious...so I appreciate your reassurance...I think the 6V6G's will fit though...
	

	
	
		
		

		
		
	


	



  
 Sorry too for being so passionate, I am just very excited and it is spilling out! lol


----------



## braaam

terrynj said:


> the newer Samsung s7 coming out, supposedly has a completely overhauled DAC/AMP setup in for people like us that are using better than $30 ear buds... I think that will be a trend from here on out with manufactures.
> 
> thanks for the info on the tubes, I am just being cautious...so I appreciate your reassurance...I think the 6V6G's will fit though...
> 
> ...


 
  
 The iPhone does support most audio interfaces through the OTG interface, but it's not well documented. I've had success using a cheap chinese lightning to USB cable, a powered USB hub and the Schiit Fulla. Pretty clumsy setup though - I vastly prefer airPlay for the convenience. The DAC/Amp in the iPhone 6s is very good IMO. It's a bit analytical and lacks some energy in the lows, but other than that it drives my 400i very well. As you mentioned, it does not sound good when using the line out - a lot of resolution is lost when I plug it directly into the APPJ.


----------



## canthearyou

UPDATE: After about 24 hours of continuous playback it sounds as if the EH tubes may have calmed the highs a bit. It sounds much better than when first installed. I must say the clarity of this amp is surprising. I was expecting a super warm, vintage* sound. The only other tube amp I've owned was the Anne T1 mk2 and never really liked the sound. It sounded bland and lifeless.


----------



## braaam

canthearyou said:


> UPDATE: After about 24 hours of continuous playback it sounds as if the EH tubes may have calmed the highs a bit. It sounds much better than when first installed. I must say the clarity of this amp is surprising. I was expecting a super warm, vintage* sound. The only other tube amp I've owned was the Anne T1 mk2 and never really liked the sound. It sounded bland and lifeless.




I think that's the reason that I found my RCA's a bit harsh sounding. The amp is already bright and the RCA's combined with relatively neutral preamp tubes magnified this. 

The stock 6V6 tubes have been chosen well IMO.


----------



## squirrelman

I got one of these guys from Amazon the other day, and sent it back the same day.  The audio was only playing through the right channel on the headphones.  It was the strangest thing, I did the windows audio test where it gives you a chime in each ear.  The left channel played very faintly in the right ear and then the right channel chimed as normal.  Then the price went up by about $10 when I sent it back so I figured i'll hold off for now.  I was excited to give this one a try since my speaker amp also takes 6V6s, so I have a lovely pair of Pope 6V6GT which are heavenly on there.


----------



## braaam

squirrelman said:


> I got one of these guys from Amazon the other day, and sent it back the same day.  The audio was only playing through the right channel on the headphones.  It was the strangest thing, I did the windows audio test where it gives you a chime in each ear.  The left channel played very faintly in the right ear and then the right channel chimed as normal.  Then the price went up by about $10 when I sent it back so I figured i'll hold off for now.  I was excited to give this one a try since my speaker amp also takes 6V6s, so I have a lovely pair of Pope 6V6GT which are heavenly on there.




The APPJ QC seems very lacking. Would love to know how those pope's would work their magic on the APPJ


----------



## a44100Hz

squirrelman said:


> I got one of these guys from Amazon the other day, and sent it back the same day.  The audio was only playing through the right channel on the headphones.  It was the strangest thing, I did the windows audio test where it gives you a chime in each ear.  The left channel played very faintly in the right ear and then the right channel chimed as normal.  Then the price went up by about $10 when I sent it back so I figured i'll hold off for now.  I was excited to give this one a try since my speaker amp also takes 6V6s, so I have a lovely pair of Pope 6V6GT which are heavenly on there.


 
  
 Mine has also had some quirks. The left channel was always at full volume. The problem seems to have gone away but I have no idea what changed.


----------



## squirrelman

a44100hz said:


> Mine has also had some quirks. The left channel was always at full volume. The problem seems to have gone away but I have no idea what changed.


 
 I'm thinking that there might have been a problem with the headphone jack on the amp, when I jiggled the plug I could head it changing.  I wasn't about to test good NOS tubes in there to see if it was just a tube problem.  I figure good NOS tubes only go into an amp after its proven itself working for a fair amount of time, especially cheap Chinese made ones.


----------



## canthearyou

squirrelman said:


> I got one of these guys from Amazon the other day, and sent it back the same day.  The audio was only playing through the right channel on the headphones.  It was the strangest thing, I did the windows audio test where it gives you a chime in each ear.  The left channel played very faintly in the right ear and then the right channel chimed as normal.  Then the price went up by about $10 when I sent it back so I figured i'll hold off for now.  I was excited to give this one a try since my speaker amp also takes 6V6s, so I have a lovely pair of Pope 6V6GT which are heavenly on there.




You should've tried for a replacement from Amazon. They probably would've sent you a new one even before you returned the bad unit.


----------



## a44100Hz

canthearyou said:


> You should've tried for a replacement from Amazon. They probably would've sent you a new one even before you returned the bad unit.




I tried. It was only "return for refund and buy another one ", no swapsies.


----------



## canthearyou

a44100hz said:


> I tried. It was only "return for refund and buy another one ", no swapsies.



Bummer


----------



## canthearyou

I've been giving this all the eartime. Barely listened to my full Burson Gustard H10. 

The tubes have settled very, very nicely. Very detailed, yet not fatiguing at all.

With that said I just placed an order for a Genalex Gold Lion 12AX7.


----------



## Aradea

canthearyou said:


> I've been giving this all the eartime. Barely listened to my full Burson Gustard H10.
> 
> The tubes have settled very, very nicely. Very detailed, yet not fatiguing at all.
> 
> With that said I just placed an order for a Genalex Gold Lion 12AX7.



Wow your setting aside your H10! That says something about the AAPJ..

Guys, I've noticed that most of you use this to drive the HE-400 line. Do you guys normally use low or high gain? Do you think that this amp could drive the HE-560??

I am trying to judge how powerful this amp is

Thanks


----------



## canthearyou

aradea said:


> Wow your setting aside your H10! That says something about the AAPJ..
> 
> Guys, I've noticed that most of you use this to drive the HE-400 line. Do you guys normally use low or high gain? Do you think that this amp could drive the HE-560??
> 
> ...




It will be fine. I'm using low gain and the volume is at 50% for normal listening.


----------



## a44100Hz

I use hi gain because... no reason. Just like it.


----------



## braaam

a44100hz said:


> I use hi gain because... no reason. Just like it.




I noticed with the 400i the sound had less clarity when using low gain, slightly muffled so I'm always at high gain.


----------



## canthearyou

braaam said:


> I noticed with the 400i the sound had less clarity when using low gain, slightly muffled so I'm always at high gain.




Now I'll have to give it a listen on high gain. The reason I never really used high was that I could only use about 25% of the available volume. I can attenuate the output from the X12 which allows greater control of the volume. 

Does it make any difference in sound quality if I attenuate the DAC?


----------



## Terrynj

canthearyou said:


> Now I'll have to give it a listen on high gain. The reason I never really used high was that I could only use about 25% of the available volume. I can attenuate the output from the X12 which allows greater control of the volume.
> 
> Does it make any difference in sound quality if I attenuate the DAC?


 
 I use the Hi-gain on mine ...I agree with Braam, it doesn't sound as good in low gain. My DAC also allows me to use the volume on it, so I turn my appj up to 75%, and run my DAC around 10%-20%...everything seems to work pretty good that way! I think you get more headroom from the amp.


----------



## Aradea

What DAC that you guys use?


----------



## Terrynj

aradea said:


> What DAC that you guys use?


 
 Mine is a little off the beaten path, the Sound Blaster E5..
 http://www.amazon.com/Creative-High-Resolution-Headphone-Amplifier-Bluetooth/dp/B00MXJYDUO/ref=sr_1_1?ie=UTF8&qid=1454026194&sr=8-1&keywords=sound+blaster+e5
  
 I do a lot of portable use on my headphones and this thing is great. It has Blue Tooth, so I can leave my phone on the counter if I'm cooking and just walk around with my 400s plugged into my E5 in my pocket. It has its own amp, has 2 headphone jacks and it would drive my 400s and the 400i at the same time (except the 400s would be louder) and it took nothing away from either one. It will do USB OTG out of my Samsung phone or usb out of my laptop, into the E5, 3.5 mm out to my Appj . The 3.5 mm out is also fiber optic. The E5 has microphones on it so if someone calls while I'm listening to music on my phone, I can answer and talk to them and hear them on the 400s.
 My TV has bluetooth, so I watched a Well recorded Willie Nelson show on PBS, bluetooth to my E5 out the Appj, to my 400s. I told my wife there probably wasn't very many people listening to that show with a tube amp and Planar Magnetic headphones! 
	

	
	
		
		

		
			




  
 It is just a really nice, fun unit that is very flexible and works really well. How does the sound compare to a Schitt or anything else? I have no idea...I never heard another Hp DAC/AMP...all I can say is it outperforms the appj with stock tubes. It made the appj sound very veiled and recessed. I got a new preamp tube this week (Sylvania JHS 5751WA) which helps a lot, the 1502A really sounds good now, but the E5 is right there with it...not far behind. I still get a VERY good sound through BT and the E5 amp.
  
 Also, on the E5, there is an App for your phone and on the laptop to control the DSP features (SBX) and an EQ... It also works a little bit when its DAC only, but it still works...Good clean adjustments without a lot of coloration.
  
  I get my power tubes tomorrow! (Tung Sol 6V6GTA, 1950's)  for my Appj....I am hoping that really lights it up.


----------



## canthearyou

braaam said:


> I noticed with the 400i the sound had less clarity when using low gain, slightly muffled so I'm always at high gain.







terrynj said:


> I use the Hi-gain on mine ...I agree with Braam, it doesn't sound as good in low gain. My DAC also allows me to use the volume on it, so I turn my appj up to 75%, and run my DAC around 10%-20%...everything seems to work pretty good that way! I think it leaves more headroom for the amp.




Ok. I just had a couple hours of listening in high gain. I have to agree with you two. It does sound better. I did go -10 on the DAC which allowed me go get to 12 o'clock on the volume dial.


----------



## CZ4A

canthearyou said:


> I paid $216 from Amazon. As of this very moment I am very pleased with the amp. I can't wait to try some different tubes.


 

 I just bought the 1502A off of Amazon after reading all these good reviews. Can't wait for it to arrive!


----------



## braaam

cz4a said:


> I just bought the 1502A off of Amazon after reading all these good reviews. Can't wait for it to arrive!




Welcome to the club, CZ4A! You may want to look for a nice pre-amp tube to replace the stock one


----------



## CZ4A

braaam said:


> Welcome to the club, CZ4A! You may want to look for a nice pre-amp tube to replace the stock one


 
 Got plenty of those! My other amp is a Project Sunrise, one of the most versatile tube-rollers out there. I also have two matched pairs of 6V6s to try (Tung-Sol and Sylvania).


----------



## yangian

Any comparison with like DV336SE, V2, etc.
 I read from massdrop someone claimed it's better than LD3, any other idea?


----------



## canthearyou

I received the 12AX7 Gold Lion tube today and it's been running for a few hours now. With just that short of time it's already better than the reissue Mullard. Very smooth yet detailed sound. Seems to make the vocals even more lifelike. Very much worth the $30 IMO


----------



## Aradea

cz4a said:


> Got plenty of those! My other amp is a Project Sunrise, one of the most versatile tube-rollers out there. I also have two matched pairs of 6V6s to try (Tung-Sol and Sylvania).



How is it when compared to the Sunrise?


----------



## braaam

cz4a said:


> Got plenty of those! My other amp is a Project Sunrise, one of the most versatile tube-rollers out there. I also have two matched pairs of 6V6s to try (Tung-Sol and Sylvania).




Nice! Coke bottle Sylvania's or the straight ones? And those Tung-Sol: vintage or reissues?

I've been running a matched pair of reissues but haven't been impressed with them. Too much roll off at the highs for my taste, the sound was a bit dark because of it. This was with a Philips 6201 gold pin as pre. 

Currently I'm hooked on the 6201 gold pin together with a set of vintage Visseaux. It's a very resolving, but pleasant sound. Good soundstage, tight (but not exaggerated) bass and great seperation. A perfect balance that matches a wide range of music.

If anyone wants to dive a little deeper into the world of 6V6 and 12ax7 tubes, here are some great specials with reviews and background: 

6V6: https://web.archive.org/web/20130805141923/http://www.jumpjet.info/Pioneering-Wireless/eMagazines/VTV/VTV10.pdf
12ax7: https://web.archive.org/web/20130805141923/http://www.jumpjet.info/Pioneering-Wireless/eMagazines/VTV/VTV14.pdf
How to spot good NOS tubes: https://web.archive.org/web/20130805141923/http://www.jumpjet.info/Pioneering-Wireless/eMagazines/VTV/VTV01.pdf

Instead of 12ax7 it's also possible to use different types like 12at7, 12au7 and european equivalents (ecc83, ecc82, ecc81). I've had great results with 12at7/ecc81 tubes which are generally cheaper too.

The same goes for 6V6. It should be possible to use 6F6, 6Y6 and 6L6 with the APPJ (warning: on your own risk, this hasn't been tested). The advantage is that some of these are in lower demand and thus a lot cheaper. 

I've asked APPJ about the use of 6y6 tubes and they comfirmed: 



> Thank you for your email once again.
> Please don't worry,i have asked our technicians again,they told me that this is not a problem,you can use 6y6 tubes replace the 6p6p tubes.Thanks.




Note that the 6Y6 draw a lot more current than 6V6, but apparantly the APPJ is build to spec for them as well.


----------



## BenWaB3

I've been back & forth between buying either the APPJ or the Schiit Vali 2. The advantage of the Vali is that it has both headphone & line outs. Is maxing the volume on the APPJ & running a line to a preamp equivalent to a line out level? Thanks


----------



## CZ4A

aradea said:


> How is it when compared to the Sunrise?


 
 I'll let you know when it arrives and I have a good listen. 
	

	
	
		
		

		
			





 The Sunrise III will be a _very_ hard act to follow, especially with my current favorite tube in it (Ken-Rad 6C8G). I do have the JJ 12AU7 the Sunrise came with kicking around somewhere so I can do a stock vs. stock test.
  


braaam said:


> Nice! Coke bottle Sylvania's or the straight ones? And those Tung-Sol: vintage or reissues?


   
 The Sylvanias are straight bottles. The T-S are vintage. They look like these, though labeled for a different company:
  

  
 I have a few singleton 6V6s and other low-powered pentodes like 6W6 and 6K6. I'd like to find some close matches before trying those, otherwise I'd be having a very odd listening experience.
  
 Quote:


braaam said:


> Instead of 12ax7 it's also possible to use different types like 12at7, 12au7 and european equivalents (ecc83, ecc82, ecc81). I've had great results with 12at7/ecc81 tubes which are generally cheaper too.
> 
> The same goes for 6V6. It should be possible to use 6F6, 6Y6 and 6L6 with the APPJ (warning: on your own risk, this hasn't been tested). The advantage is that some of these are in lower demand and thus a lot cheaper.
> 
> ...


 
 Good to know about the power stage. I wonder what the output current is for the preamp stage, as well as whether or not it runs the 12AX7 in parallel (6.3V) or series (12.6V) mode. That info will have a big effect on those of us who get more adventurous with our rolling than the usual 12A#7 suspects.


----------



## Terrynj

I've had my 1502 for almost 3 weeks now. It took me awhile to pick tubes because I had never even looked at, or considered a tube amp until about a week before I got my appj... Braaam and E8armydiver helped me alot to learn the basics...my thanks to both of them!
  
 I picked my preamp first, I relied a lot on Joe's Tube Lore to help with my final decision and was lucky enough to find a Sylvania JHS 5751WA (1958, black plates). Very pleased with this guy. The 5751 is a lower gain 12AX7, Braaam likes lower gain tubes and I agree. The 5751 made the soundstage more focused, better bass, and more delicate detail.

  
  
 I just received my power tubes on Friday. I found some vintage Tung Sol 6V6GTA's (1950's, black plates).  At this point, I think I've ruined my rolling plans.....I AM VERY HAPPY with my setup. As much as I loved my 5751, things still felt a little loose. The images were there, but the stock tubes struggled to reproduce them....now....that is not an issue! It is hard to explain the sound I am getting, for one, I am not as versed in the terminology to produce the flowing reviews I've read, with descriptions that float in the air like the music they describe.

  
  
  
 My Headphones are modded HE400s's with Focus Pads A and new grills. I love the 400s and these too are new for me (12/15). I've had HP's and IEM's for years, but this planar is something else. I also bought the 400I, but I really preferred the bigger soundstage on my 400s and the open airy sound it has, so I sent the 400I back and kept my S.
  
 My DAC/AMP is the Creative Soundblaster E5. I've written about it in other threads, so check back through my other post for more detail. I like to go portable which is why I went that direction. But I am very pleased with it and the sound. If you like your appj stock, the sound on my E5 is much better IMO. The appj felt subdued and veiled. Not near as open and airy, but I could see the promise of the tube sound (plus I'm a tweak and I like to mess with things!
	

	
	
		
		

		
		
	


	




)
  
 When I got the 5751, the sound immediately became on par with the E5...different, but on par. With the Tung Sol tubes, the appj has now surpassed the E5. I always felt the E5 sound was pretty solid, the sound stage was very wide on the 400s, but to me, it felt the images lost something being spread out so much...sorta like you painted 10 foot of wall ...then took the same amount of paint and painted 14 feet of wall...The 5751 and Tung sols fixed all that and actually did something weird to the sound stage. It still feels open and airy, but the images now blend better as a complete image...still separate, but instead of a separate image here, the drums over there, the singer here, lead guitar over there...now they are all the same image, no air between them, but still wide, layered, and detailed. The 400I had this kinda of imaging....unfortunately I had to send them back before I got all my tubes in.
  
 My preference to my 400S is the wide, open, airy, live feel to them. The DAC on the E5 has DSP, so I can adjust the bass, EQ things, and really tailor the sound to my liking. I get a rich, creamy bass that has detail and no bloat.... especially at low volumes. I am very happy with where I am at now and cant think of how I would want to improve it. I have some Sylvania 6Y6G's coming in because I like the look of the coke bottles...I'll try them, but not expecting much. I really like the look of my new tubes, but the Tung Sol label went to the back towards the transformers, so you cant see the labels!


----------



## a44100Hz

Massdrop is offering these again, in black.


----------



## Aradea

a44100hz said:


> Massdrop is offering these again, in black.



Checking


----------



## a44100Hz

For the price (~165 shipped; maybe cheaper) it's definitely worth it. I'm considering buying a second one in black. (I have a silver one. It's been a little buggy. I worry about it failing. I think I'm the only one here with this specific issue though.)


----------



## Aradea

Wow the shipping cost is $63 to Indonesia!

Guys, I've never join a drop before. So how's the shipping/shipping cost works btw? Will it go down along with the increasing number of people who joins the drop??


----------



## a44100Hz

aradea said:


> Wow the shipping cost is $63 to Indonesia!
> 
> Guys, I've never join a drop before. So how's the shipping/shipping cost works btw? Will it go down along with the increasing number of people who joins the drop??




I don't think so; massdrop is meant for the U.S. mainly. You could try eBay. They ship from China.


----------



## canthearyou

a44100hz said:


> For the price (~165 shipped; maybe cheaper) it's definitely worth it. I'm considering buying a second one in black. (I have a silver one. It's been a little buggy. I worry about it failing. I think I'm the only one here with this specific issue though.)




Damn! That's a helluva deal!


----------



## Aradea

a44100hz said:


> I don't think so; massdrop is meant for the U.S. mainly. You could try eBay. They ship from China.



Hmmm with the massdrop price, even with that shipping cost, its still cheaper than the MSRP


----------



## CZ4A

canthearyou said:


> Damn! That's a helluva deal!


 

 Figures, MD has another drop for it only 3 days after I ordered mine from Amazon, lol! Still, the last time I joined the drop, it failed to garner enough people. I hope it goes better for everyone else this time. My 1502A is already in the mail so I can't return it.
  
/Why are these grapes so sour?


----------



## Kramertc

I joined the drop. $165 shipped (US) is quite a bit lower than anywhere right now.  I have been eyeing this amp for some time.
 Only 4 more needed...


----------



## braaam

a44100hz said:


> I don't think so; massdrop is meant for the U.S. mainly. You could try eBay. They ship from China.




How is that? Most drops have very fair shipping costs to mainland Europe. The Appj is probably just uneconomical because of it's square size.


----------



## a44100Hz

braaam said:


> How is that? Most drops have very fair shipping costs to mainland Europe. The Appj is probably just uneconomical because of it's square size.




The site is based in the U.S. as far as I know. They list prices in USD, have a "physical nexus" in California and NJ (and thus charge sales tax there), products like amps always have U.S. voltage options, the drops I've seen base shipping costs on U.S. delivery, and certain products cannot be shipped directly outside of the U.S. by massdrop due to their manufacturing agreements.


----------



## braaam

cz4a said:


> Good to know about the power stage. I wonder what the output current is for the preamp stage, as well as whether or not it runs the 12AX7 in parallel (6.3V) or series (12.6V) mode. That info will have a big effect on those of us who get more adventurous with our rolling than the usual 12A#7 suspects.




I asked the people at APPJ and they answered promptly:



> This tube amp output current is 0.6A，and the appj run the 12AX7 is in series (12.6V) mode.




Now I don't have much knowledge about the workings of electrical components. What does this mean for tube rolling?


----------



## braaam

a44100hz said:


> The site is based in the U.S. as far as I know. They list prices in USD, have a "physical nexus" in California and NJ (and thus charge sales tax there), products like amps always have U.S. voltage options, the drops I've seen base shipping costs on U.S. delivery, and certain products cannot be shipped directly outside of the U.S. by massdrop due to their manufacturing agreements.




This doesn't hold true in my experience. As a Gustard H10 massdrop customer from the EU I can tell you that:

- no sales tax was added to the price (obviously when the thing passes EU borders there will be import tax to take into account)
- there is a eu voltage option (and that goes for many of the products on offer). 
- shipping price is shown for my specific location, and it is suprisingly low for many of the products on offer. For the H10 (which is a heft amp) it was about 30 euros. I've seen lower for many products.

I've checked dozens of drops in the audiophile community and more than 90% was available at reasonable shipping cost. The APPJ is the exception here.


----------



## a44100Hz

Has some consensus been reached on which 6V6 tubes are producing the best bang for the buck results with this amp?


----------



## CZ4A

braaam said:


> I asked the people at APPJ and they answered promptly:





> > This tube amp output current is 0.6A，and the appj run the 12AX7 is in series (12.6V) mode.





> Now I don't have much knowledge about the workings of electrical components. What does this mean for tube rolling?


 

 Interesting. I would have thought the preamp tube would have run in 6.3V mode since the 6V6s have to. The thick plottens...
  
 As for what this means for rolling the preamp tube, first of all 6.3V tubes like the 6DJ8, 6CG7, 6BZ7, etc. are NOT compatible with the 1502A. If the 12AX7 were running in 6.3V mode, then the above tubes would have been electrically compatible. An adapter would be needed because the pin-outs are different, but they most likely would have worked.
  
 Secondly, the 0.6A output current means the 12BH7 and its variants will most likely work. In 12.6V mode, the 12AX7 draws 0.15A of current. The 12BH7 is a nicer-sounding alternative to many 12AU7s. It draws 0.3A when running off of 12.6V, so it needs a beefier current supply- and the APPJ appears to have it.
  
 There are other implications here but I want to get my grubby hands on my 1502A first and try them before I go any wilder with my ideas. Also, if I've put any ideas into YOUR heads, please remember I am not responsible if your amp, your tubes, and/or you go up in smoke.


----------



## yangian

I saw the power from massdrop discusisoion:
 1W @ 32ohms
 500mw @ 100ohms
 260mw @ 300ohms
 130mw @ 600ohms
  
  
 Anyone knows the data of power are totally or for each channel?
 Thanks!


----------



## FoxyGrandpa

This or the vali 2. For the fidelio x2s . Listen to hip hop and alternative


----------



## kazcou

yangian said:


> I saw the power from massdrop discusisoion:
> 
> 
> 1W @ 32ohms
> ...



 


Is for each channel.

This amp have enough power to drive a HE-6 when the gain is set to high and the result is not to bad.


----------



## Aradea

Can this amp safely drive an IEM?


----------



## utee05

Looks like I'll join in on this drop. Was  going to get a vali2 but this looks like a good one to pair with my HE400


----------



## DarthTater

I use a PA1501A to drive my Stax SR-40s and I really like it, so I'm in for this one.


----------



## braaam

CZ4A thanks for sharing the knowledge.

We have some more exploration to do now 

I have some 6F6's on the way. Will share how that goes. And I'm sure that Terrynj will let us know how the 6Y6es behave.

I'm also experimenting with 5755, e180cc and a 13d9 (warning: one of these types will make the APPJ go up in fumes if not used with a converter )


----------



## i20bot

If the RCA's work as INs and OUTs then how does it work as OUTs if there's no other IN?


----------



## canthearyou

i20bot said:


> If the RCA's work as INs and OUTs then how does it work as OUTs if there's no other IN?



I believe that's a typo.


----------



## yangian

kazcou said:


> yangian said:
> 
> 
> > I saw the power from massdrop discusisoion:
> ...


 
 Ok. Thanks. That's a reasonable power, not impressive at all.


----------



## Socratease

cz4a said:


> Interesting. I would have thought the preamp tube would have run in 6.3V mode since the 6V6s have to. The thick plottens...


 
 They could have wired the two 6V6 filaments in series, that's a pretty common tube technique.


----------



## utee05

yangian said:


> Ok. Thanks. That's a reasonable power, not impressive at all.


 
 Seems to be on par with the Vali 2. Makes sense why people compare the 2.


----------



## CZ4A

socratease said:


> They could have wired the two 6V6 filaments in series, that's a pretty common tube technique.


 
 Yeah, that makes sense. I think I forgot my Electricity 101 there.


----------



## Socratease

The old table-top AM receivers would wire all the tube filaments in series and then connect them across the 110VAC line, no transformer.  As long as all the filament voltages added up to 110 AND the rated filament currents were the same, it worked.


----------



## Preludio

Hi!!! does anyone tried the amp with the AKG 7xx? i'm searching for a good pairing. Can someone compare this to the Vali 2 -that was my first choice- with the AKG 7xx? i´m interested in the drop.
  
 My DAC is the Bifrost Uber Analog (from Schiit). I listen to classical music, jazz, and some prog/experimental rock... so maybe i prefer the so called "analytical sound"...
  
 Thanks!


----------



## CZ4A

preludio said:


> Hi!!! does anyone tried the amp with the AKG 7xx? i'm searching for a good pairing. Can someone compare this to the Vali 2 -that was my first choice- with the AKG 7xx? i´m interested in the drop.
> 
> My DAC is the Bifrost Uber Analog (from Schiit). I listen to classical music, jazz, and some prog/experimental rock... so maybe i prefer the so called "analytical sound"...


 
   
 I have a K7XX and my 1502A is coming in soon. I will let you know my impressions. I also have to plug Garage1217's amps as another Vali 2 alternative - I've been very pleased with my Sunrise. In fact, you really can't go wrong with anything from their line-up, tube or solid state.


----------



## canthearyou

preludio said:


> Hi!!! does anyone tried the amp with the AKG 7xx? i'm searching for a good pairing. Can someone compare this to the Vali 2 -that was my first choice- with the AKG 7xx? i´m interested in the drop.
> 
> My DAC is the Bifrost Uber Analog (from Schiit). I listen to classical music, jazz, and some prog/experimental rock... so maybe i prefer the so called "analytical sound"...
> 
> Thanks!


I have them. I'll give it a listen tonight.


**they sound great! I'm not really hip to the terminology of describing the sound. But it's something that I could listen to all the time.

I am not running stock tubes, though. 

This little amp is a great deal!

*** I'm always surprised at the soundstage size of the K7XX after mainly listening to the 400i.

I will say I do prefer the K7XX being powered by my full Burson H10.


----------



## Preludio

Oh great!, thanks for the answer!, and what tubes did you used for the 7xx?


----------



## CZ4A

preludio said:


> Hi!!! does anyone tried the amp with the AKG 7xx? i'm searching for a good pairing. Can someone compare this to the Vali 2 -that was my first choice- with the AKG 7xx? i´m interested in the drop.
> 
> My DAC is the Bifrost Uber Analog (from Schiit). I listen to classical music, jazz, and some prog/experimental rock... so maybe i prefer the so called "analytical sound"...
> 
> Thanks!


 

 Agreed with @canthearyou. I need to listen to it a little more with the stock tubes to get a better feel and description, but the 1502A works well with the K7XX. I listened mostly to metal and some video game soundtracks after I ran some pink noise through the amp at first. I used the stock 6N4-J + 6P6Ps and a low-testing Telefunken smooth plate 12AX7 with the 6P6Ps. It biased fine with the T-Funk, BTW.
  
 Next up I want to try a 12BH7, then start rolling the 6P6Ps. I don't know if my Sylvanias or NOS Tung-Sol 6V6s will make the amp sound better or worse, but one thing's for sure- The 6P6Ps are UUUUUUGGGGG-LY!


----------



## braaam

cz4a said:


> Agreed with @canthearyou
> . I need to listen to it a little more with the stock tubes to get a better feel and description, but the 1502A works well with the K7XX. I listened mostly to metal and some video game soundtracks after I ran some pink noise through the amp at first. I used the stock 6N4-J + 6P6Ps and a low-testing Telefunken smooth plate 12AX7 with the 6P6Ps. It biased fine with the T-Funk, BTW.
> 
> Next up I want to try a 12BH7, then start rolling the 6P6Ps. I don't know if my Sylvanias or NOS Tung-Sol 6V6s will make the amp sound better or worse, but one thing's for sure- The 6P6Ps are UUUUUUGGGGG-LY!




Terrynj is very happy with his NOS Tung-Sol's. Big improvement from the 6P6P's in his opinion. 

Curious about the 12BH7. Did you get one yet?


----------



## CZ4A

braaam said:


> @Terrynj is very happy with his NOS Tung-Sol's. Big improvement from the 6P6P's in his opinion.
> 
> Curious about the 12BH7. Did you get one yet?


 
 I've got a few 12BH7s I can try. Just haven't gotten to them yet. 
	

	
	
		
		

		
			




  
 I am currently listening with my K7XXs and a Telefunken smooth plate 12AX7 paired with a matched pair of Sylvania gray glass 6V6GTs. The sound signature has all the excellent detail one would expect from the smooth plate T-Funk. It's got a great soundstage for a smaller tube. Highs like cymbal crashes are nice and sparkly, but can get a bit crashy when the drummer goes all Animal on them. However, while the bass is present, it's slightly lacking in oomph.
  
 While I did listen to the T-Funk with the stock 6P6Ps it wasn't a very critical listen, so I don't yet have a handle on how the power tubes are affecting the tone. I also want to give the T-S 6V6GTs a go and see if they add a little bit of the lows back.
  
 One other thing I have to add that relates more to build quality than sound- when I was removing one of the 6P6Ps to swap in the Sylvania, the bottom of the central locating pin actually chipped a little of the ceramic from the socket! I wasn't using excessive force or anything either. The chip only caused superficial damage to the socket, but be careful anyways when removing the power tubes!


----------



## Preludio

Uhh great, thanks for the impressions, so i guess the match may come with some tube rolling... And you feel them (the 7xx) better than with the vali 2 ? SS, detail, bass impact, mids...?


----------



## CZ4A

preludio said:


> Uhh great, thanks for the impressions, so i guess the match may come with some tube rolling... And you feel them (the 7xx) better than with the vali 2 ? SS, detail, bass impact, mids...?


 
 I wouldn't know because I don't own a Vali 2.


----------



## Terrynj

Got my Coke Bottles in! Sylvania 6Y6G 1952
  

  
 I wasn't sure if they would even fit, so I didnt want to spend much. Bram confered with Gemtune and they said the 6Y6G would work fine in the 1502, so I crossed my fingers, turned it on and stepped back about 10 feet...no problems!
	

	
	
		
		

		
		
	


	



  
 Heres a pic of size difference...the right tube is a 1958 Tung Sol 6V6GTA..
  

  
 They burn pretty hot.....
  

  
  
  

  
 I was not really sure how they would sound. As I had stated, these are not near as expensive as 6V6G's ( I paid $20 for the pair with free shipping) so I was not expecting much for sound...just wanted to see if I liked the looks, then could maybe pursue a nice set of Sylvies or Marconi's if I liked them
  
 Started out with a couple of my regular test tracks and was shocked...they sounded good, very good!
 Started to really go through my playlist and realized the details were there, the bass IMO was a little better than the TS, the midrange was more forward. My rock stuff really came forward with the crunching guitars...couldn't be more shocked and pleased.
 I listened for a couple of hours and picked the the differences in these and the TS..I don't think they sound good on everything like the TS's do, the forward midrange started to sound a tad harsh on some songs...I will have to go back to the TS's to verify, but I certainly think the TS's are still my mains, but I am stunned how good these sound.
 I am running the Sylvania JHS 5751WA preamp tube.....
  
 this is Friday morning and giving them the morning test drive  ... Megadeth's new album Dystopia...man his driving guitars are awesome..these are great rock tubes!
  
 SInce the work good for that, I am trying some classical...which is usually hard the bring out the strings. I ve have always tried to get more out of the violins, but its been hard. I am listening to very forward violins driving like a rock song. They dont have the creamier sound of the TS's,, still a little sweet. but the best I've ever heard classical (for the way I like)...doesnt seem harsh this morning either. 
 Gotta go to work right now, tonight cant come quick enough!


----------



## canthearyou

Nice! Glad to know they fit. I've been eyeing a couple pairs and was worried they wouldn't fit.


----------



## braaam

Wow, those coke bottles are huge!!

I got some 6F6 Visseaux lined up - these are pretty similar to 6V6 but less efficient and very affordable!



Unfortunately I had to return my APPJ, it started to produce noise in the left channel after rolling a pre-tube. I suspect one of the pin sockets failed. 

Will be using a socket saver from now on:


----------



## 1800yolk

braaam said:


> Unfortunately I had to return my APPJ, it started to produce noise in the left channel after rolling a pre-tube. I suspect one of the pin sockets failed.


 
  
 damn, how often were you switching tubes out? I suppose I should get some, I just joined the massdrop, can't wait to join the small 400i tube swapping club in this thread. Definitely give an update on how easy working with them was on swapping the unit tho, thanks


----------



## CZ4A

braaam said:


> Wow, those coke bottles are huge!!
> 
> I got some 6F6 Visseaux lined up - these are pretty similar to 6V6 but less efficient and very affordable!
> 
> ...


 
 Nice. The Project Ember folks have been gaga for Visseaux 6J5 tubes. Hope they work well for you if you get a replacement 1502A. As I noted earlier, I chipped a little porcelain off of one of the power tube sockets so it appears to me they are not good quality. If I open mine up to do the Wima capacitor swap, I will probably replace the tube sockets too.
  
 I can happily confirm the 12BH7 works fine. I've tried a Realistic 12BH7A (Japanese made, probably Toshiba) and a Westinghouse US-made 12BH7. The Realistic is a pretty lifeless tube. The Westinghouse is much better. Highs are a bit rolled off, but the bass has returned to the party!


----------



## yangian

utee05 said:


> Seems to be on par with the Vali 2. Makes sense why people compare the 2.


 
 Really? On on par the Vali 2?! That's not impressive at all! But you mean power or SQ? If SQ, that's not a good value.


----------



## i20bot

yangian said:


> Really? On on par the Vali 2?! That's not impressive at all! But you mean power or SQ? If SQ, that's not a good value.


 

 Yeah, you'd think it'd be better since it's Class A.  The only thing stopping me from getting one is it has no outs.


----------



## canthearyou

Being very satisfied with the sound of the Gold Lion pre-amp tube, I decided to try the power tubes. They had two models, one being cryogenic treated?. I wasn't sure if that was worth the additional $30, or something that actually makes a difference, so I opted for the standard version.


----------



## utee05

yangian said:


> Really? On on par the Vali 2?! That's not impressive at all! But you mean power or SQ? If SQ, that's not a good value.


I meant in regards to power. Since the tubes can be rolled a bit more it should provide a better SQ


----------



## braaam

1800yolk said:


> damn, how often were you switching tubes out? I suppose I should get some, I just joined the massdrop, can't wait to join the small 400i tube swapping club in this thread. Definitely give an update on how easy working with them was on swapping the unit tho, thanks




Probably about 30/40 times for the pre. I got my unit from amazon and was lucky that it was still within the 30 days return time so I simply returned it and ordered another one.


----------



## braaam

cz4a said:


> Nice. The Project Ember folks have been gaga for Visseaux 6J5 tubes. Hope they work well for you if you get a replacement 1502A.



I'd love to get my hands on some Mazda's as well, as they should be similar (possibly even better) but haven't spotted any of those. Should have another APPJ in 2 days. Life is different without it!



> As I noted earlier, I chipped a little porcelain off of one of the power tube sockets so it appears to me they are not good quality. If I open mine up to do the Wima capacitor swap, I will probably replace the tube sockets too.


 Would be nice if you could document your endeavors with some pics here 



> I can happily confirm the 12BH7 works fine. I've tried a Realistic 12BH7A (Japanese made, probably Toshiba) and a Westinghouse US-made 12BH7. The Realistic is a pretty lifeless tube. The Westinghouse is much better. Highs are a bit rolled off, but the bass has returned to the party!




Good to know. do you know who made the Westinghouse?


----------



## CZ4A

braaam said:


> Would be nice if you could document your endeavors with some pics here
> 
> 
> 
> ...


 
 Sure thing re: opening up the amp.
  
 I believe my Westinghouse 12BH7 was made by... Westinghouse. The plate construction doesn't appear to have been used in other brands. Westinghouse did make some of their own tubes, but later on sold relabeled RCAs or Japanese tubes.


----------



## Preludio

I recently join the drop for this little monster. It´s all your fault! :') jaja, the AKG 7xx are also on their way to Perú from massdrop O.O. Can´t wait!!
  
 Only a few questions: A preamp tube not too expensive  can you recommend eyes closed? (I prefer a clean and open sound...)
  the power stock tubes are too bad or can i live with them for some months?


----------



## Saillaw

I also joined the massdrop for this amp.  I'm going to let it be my introduction to the world of tube amps.  I've also ordered a few replacement tubes as mentioned in this thread.  But, as CZ4A mentioned he "chipped a little porcelain off of one of the power tube sockets", I'm wondering if there is something I can do to help prevent that.  Are the "socket savers" that someone mentioned earlier worth considering?  If so do you guys have any recommendations of where I can find some?


----------



## braaam

cz4a said:


> Sure thing re: opening up the amp.
> 
> I believe my Westinghouse 12BH7 was made by... Westinghouse. The plate construction doesn't appear to have been used in other brands. Westinghouse did make some of their own tubes, but later on sold relabeled RCAs or Japanese tubes.




Ah, didn't know they made 12BH7 tubes. That's one to look for then.



preludio said:


> I recently join the drop for this little monster. It´s all your fault! :') jaja, the AKG 7xx are also on their way to Perú from massdrop O.O. Can´t wait!!
> 
> Only a few questions: A preamp tube not too expensive  can you recommend eyes closed? (I prefer a clean and open sound...)
> the power stock tubes are too bad or can i live with them for some months?




Congrats and welcome to the club!

Stock power tubes are decent enough. There are better ones but stock is adequate to start rolling the pre's.

A clean, tight and airy tube is the valvo/philips/amperex 6201. It does also have a nice smooth midrange. The best balance I've heard. Now these don't come exactly cheap. 

An alternative is the Siemens e81cc triple mica (a bit more analytical, a bit less smooth in the mids).

I also enjoyed the Philips/Dario Miniwatts 12ax7 and 12au7. Made in France/India/Holland are all similar. They have a big soundstage and are open and dynamic. You should be able to find them at lower prices than the above.


----------



## braaam

saillaw said:


> I also joined the massdrop for this amp.  I'm going to let it be my introduction to the world of tube amps.  I've also ordered a few replacement tubes as mentioned in this thread.  But, as CZ4A mentioned he "chipped a little porcelain off of one of the power tube sockets", I'm wondering if there is something I can do to help prevent that.  Are the "socket savers" that someone mentioned earlier worth considering?  If so do you guys have any recommendations of where I can find some?




I haven't received them yet. I think you shouldn't be too worried if you're only going to roll a few tubes though. 

http://www.ebay.nl/ulk/itm/161256246187


----------



## 1800yolk

anyone know the specific output impedance of this amp? Or is it not even static, and fluctuates depending on the tubes you use? i feel like this is an incredibly noobish question but.. thanks!


----------



## imelofi

Nice... Price? What's the best pairing?


----------



## 1800yolk

imelofi said:


> Nice... Price? What's the best pairing?


 
 https://www.massdrop.com/buy/appj-1502a-tube-headphone-amplifier
  
 you've got 50 minutes!
  
 also, people say it pairs well with lower impedance headphones, and a few on here are fans of using it with the 400i, which is what i'm going to do :V


----------



## BenWaB3

The mass drop is over & they reached the amount of commitments they needed (actually I think they had reached it a while ago). So those who participated (myself included) should be enjoying this amp in about a month!


----------



## canthearyou

I was thinking about a 2nd one at that price. You know, just in case.


----------



## canthearyou

Received my Genalex Gold Lion power tubes today. Very much worth the $50. First thing that becomes apparent is an even quieter background. Next I noticed greater separation and clarity of instruments. This is with only 10 mins on the new tubes. I will update after a few days.

*Didn't even make it a few days. After the tubes got some heat to them the combo became to warm and soft for my taste. I swapped the pre-amp tube to Mullard 12AX7. Now I have that sparkle and crispness back with a black background. 

If you have rather bright, detailed power tubes ie: Electro Harmonix, the Gold Lion pre-amp makes a nice combo. On the other hand, if you have warm power tubes, the bright, detailed Mullard makes a nice combo.

I know these are my opinions. But one thing I can say for sure is the Gold Lion power tubes have a much quieter background.


----------



## CZ4A

I have a very interesting vacuum tube to test that's currently in shipping:
  

  
 This is an Amperex 8416. It's a rare, premium-quality tube originally intended for use in oscilloscopes. Electrically it's a 12v 6DJ8 (12DJ8). The Amperex (Holland-made) orange globe 6DJ8 is one of my favorite 9-pin tubes but isn't compatible with the 1502A. I'm interested to see if this lives up to the "premium-quality" billing.


----------



## canthearyou

Cool. Waiting for your impressions.


----------



## braaam

Interesting, didn't know these types could be used as well. 

I went all French today: RT 6189 with the Visseaux 6F6. The RT is a military 12au7 screened for low noise. Very transparant and resolving with tight bass. A bit rolled off in the highs and a bit of sweetness in the mids. A great tube that fits a lot of styles.







Edit: update on the RT 6189

Listened to Bach's Concerto in E Major for Violin, Radiohead, Daft Punk, Patricia Barber. The RT 6189 is doing a lot (read: everything) right. Dynamic and alive with Daft Punk, intimate and never harsh with Patricia Barber and always in control with Radioheads "15 step". With Bach you can pick up every note from the different instruments but it all sounds coherent at the same time. 

It may be resolving too much for things like black metal but that's not really a fault of the tube itself and could be fixed by using warmer power tubes I'm sure 

It is close to perfection for what I'm looking for.


----------



## CZ4A

braaam said:


> Interesting, didn't know these types could be used as well.
> 
> I went all French today: RT 6189 with the Visseaux 6F6. The RT is a military 12au7 screened for low noise. Very transparant and resolving with tight bass. A bit rolled off in the highs and a bit of sweetness in the mids. A great tube that fits a lot of styles.


 
 The heater requirements (12.6V, 0.15A) and pinouts of the 12AX7 and 8416 are identical except for the #9 pin- on the 12AX7 its the center tap for 6.3V operation and for the 8416 (and 6DJ8, 6922, Cca, etc.) it connects to the internal shield. Since the #9 pin is not used in 12V operation, the 8416 should work (biasing notwithstanding).
  
 That RT looks interesting. Never heard of that company. Nice to hear some positive impressions of it.


----------



## braaam

cz4a said:


> The heater requirements (12.6V, 0.15A) and pinouts of the 12AX7 and 8416 are identical except for the #9 pin- on the 12AX7 its the center tap for 6.3V operation and for the 8416 (and 6DJ8, 6922, Cca, etc.) it connects to the internal shield. Since the #9 pin is not used in 12V operation, the 8416 should work (biasing notwithstanding).
> 
> That RT looks interesting. Never heard of that company. Nice to hear some positive impressions of it.




Thanks for the explanation. What would the internal shield be used for? 

The full name is La Radiotechnique. They were a subsidiairy of Philips but had their own production line. The sound has similarities to miniwatt tubes (great soundstage and smoothness) but it's more revealing, towards the Valvo's (which are probably a bit dryer overall). Comparisons are from memory, I'll do direct comparisons later. 

In the meantime I'm also waiting for delivery of some rebranded Telefunken 5965 tubes to see how they compare.


----------



## CZ4A

braaam said:


> Thanks for the explanation. What would the internal shield be used for?


 
 To keep the electrons on their sides of the playground, of course! It's situated between the triodes. I don't think the shield is necessary for audio use- for example from what I've read there isn't any sonic difference between the 6CG7 and 6FQ7, which are identical aside from the 6CG7 having a shield between the triodes and the 6FQ7 lacking that shield. For more sensitive equipment like oscilloscopes. the shield might have been more essential.
  


braaam said:


> The full name is La Radiotechnique. They were a subsidiairy of Philips but had their own production line. The sound has similarities to miniwatt tubes (great soundstage and smoothness) but it's more revealing, towards the Valvo's (which are probably a bit dryer overall). Comparisons are from memory, I'll do direct comparisons later.


 
 Radiotechnique rings a bell. Thanks for the clarification.


----------



## braaam

cz4a said:


> To keep the electrons on their sides of the playground, of course! It's situated between the triodes. I don't think the shield is necessary for audio use- for example from what I've read there isn't any sonic difference between the 6CG7 and 6FQ7, which are identical aside from the 6CG7 having a shield between the triodes and the 6FQ7 lacking that shield. For more sensitive equipment like oscilloscopes. the shield might have been more essential.
> 
> Radiotechnique rings a bell. Thanks for the clarification.




That makes good sense 

I was wondering: do you have experience with 6G6 power tubes? Seems they are similar in spec but accept only max around 190v on the plates. Would that be ok with the APPJ?


----------



## CZ4A

braaam said:


> I was wondering: do you have experience with 6G6 power tubes? Seems they are similar in spec but accept only max around 190v on the plates. Would that be ok with the APPJ?


 
 I don't know. It depends on the amp's plate voltage - if it's too high the 6G6s won't last very long.
  
 I have a similar dilemma with a matched pair of 6W6GTs that I found- the max screen voltage is only 150v. Without those stats from APPJ all I can say is cross your fingers!


----------



## braaam

cz4a said:


> I don't know. It depends on the amp's plate voltage - if it's too high the 6G6s won't last very long.
> 
> I have a similar dilemma with a matched pair of 6W6GTs that I found- the max screen voltage is only 150v. Without those stats from APPJ all I can say is cross your fingers!




The question is out to APPJ, lets hope we'll get our answer before we start burning some fine tubes


----------



## chellity

I've been using this amp for a few weeks now, and it still blows me away everytime I turn it on.  it truly is an experience...I love showing my set up to people and watching their reactions.   here are my impressions as a newbie with my first headphone/amp set up, period.  a set up like this made me devote so much time just to critical listening, because now I have to relisten to all my old favorites.  this amp and the 400i really did breathe new life into old music, for me.
  

  
  
      I tried out the vali 2 like others, and found it a little lacking.  I eventually found this amp and was surprised I could even get a full tube amp that would work with my 400i in this price range.  I bought a miniwatt ecc83, but the seller broke it so he sent me two equivalent quality tubes for the price of one  I got pretty lucky..ended up with a fisher/amperex ecc83 and a dyanco/telefunken that I haven't even tried yet.  the amperex sounds so amazing that I don't even feel the need to pop in the telefunken yet.   I do find some microphonics on a few extreme songs, but i'm guessing its mostly because amperex ecc83s can be prone to ringing at times?  (neon indian, im looking at you)  I also tried some rca power tubes, but I'm not sure if they had a positive effect on the bass.  I might be interested in trying some newer power tubes, later.  
  

  
  
      keep in mind i'm a newbie, but i'm loving this mid-fi sound.  the soundstage on my 400i feels more than acceptable,even coming from a modi2/lsr 305.  the sound is rich, and compelling.  distorted vocals sound amazing, sometimes syrupy, and even ethereal at times.  electric guitars, chimes, metallic noises, seem to sound glittering (passion pit, beach house) I swear fender guitars seem to have that same bell-like quality that they have in real life, now. things just seem to sound more organic and a bit warmer, and maybe even less forced on some tones (obvs- jamie xx).  all those positives combined with the very low tube noises, surprisingly good build quality, and more than enough headroom for me makes this a really good beginner tube amp for me.  also...somehow I feel like I can notice the difference between flacs and high quality mp3s with this set up compared to my speakers (mostly just clarity).  any downsides I notice are probably more due to the nature of tube amps (since they might affect instrument separation, right?)  I couldn't really ask for more for a first time tube amp in this price range.
  


  
  
 thanks to everyone that seemed to fight so passionately trying to get people to notice this amp!   and to those that helped with their input earlier.   I'm very happy with my first set up.


----------



## braaam

Hi, @chellity, great post! Glad you like the Amperex, taking from your photo it's the same tube as the Holland-style miniwatt's. They are still among my favourites after trying many others. 

 To me the RCA 6V6's can get a bit too hot in the treble department (slightly harsh) together with the European pre-tubes. They may sound better with different headsets (the 400i is a bit aggressive sounding).
  
 And you didn't even try the Telefunken yet - that should be one of the top 12ax7 tubes! I suspect (from research) it will be less smooth and more analytical than the Amperex.


----------



## braaam

Update about the plate voltage CZ4A:



> The plate voltage is 210V, and both 6G6 & 6W6 are good to use.




Now that's interesting since it seems a bit above spec for those types?


----------



## CZ4A

> Originally Posted by *chellity* /img/forum/go_quote.gif
> 
> I tried out the vali 2 like others, and found it a little lacking.  I eventually found this amp and was surprised I could even get a full tube amp that would work with my 400i in this price range.  I bought a miniwatt ecc83, but the seller broke it so he sent me two equivalent quality tubes for the price of one  I got pretty lucky..ended up with a fisher/amperex ecc83 and a dyanco/telefunken that I haven't even tried yet.  the amperex sounds so amazing that I don't even feel the need to pop in the telefunken yet.   I do find some microphonics on a few extreme songs, but i'm guessing its mostly because amperex ecc83s can be prone to ringing at times?  (neon indian, im looking at you)  I also tried some rca power tubes, but I'm not sure if they had a positive effect on the bass.  I might be interested in trying some newer power tubes, later.


 
  
 I can't quite tell from the picture, are the plates smooth or ribbed? Either way, you're in for a treat if you like a dryer sound. I have four T-Funk smooth plate 12AX7 (three of them_ very_ used up) and have tried them in the 1502A with my Sylvania 6V6GTs. braaam is right about them being analytical - the level of detail is impressive. The T-F smooth plates do lean bright, though, so take that into account with your power tubes - before my Sylvania 6V6GTs burned it the combination was almost painfully bright. I might try rolling some different power tubes soon, but for now I'm going to leave the T-Fs for my other amp. I'm currently using a gray plate GE 5-Star 5751 that does a good job of balancing out the highs with the lows.


braaam said:


> Update about the plate voltage @CZ4A:
> Now that's interesting since it seems a bit above spec for those types?


 
 The 6W6 has a max plate voltage of 300V, so that isn't a problem (I was more concerned about the max screen voltage, but after re-reading the datasheet it may not be a problem after all). The 1502A's plate voltage is above spec for the 6G6 (180V) but that maybe not enough to cause huge problems- plus it may automatically bias the power tubes too.
  
 If the manufacturer says they're OK to use it may be worth the ol' college try. I'll let you know how my 6W6GTs fare. The labels on the bases are gone so I don't know who made them but I suspect CBS Hytron. The type label is still present on the top of the glass, just like their 6SN7s.


----------



## CZ4A

I've tried my CBS(?) 6W6GTs in the 1502A and they work. I didn't see or hear anything troubling. I only had them on in for about an hour, so I'm not ready to give an impression yet. The 6W6 might make for a cheap rolling option if they sound good. They're much cheaper than most other power tubes on eBay. My Google-fu tells me they have limited uses, mostly in TVs. Sometimes they find their way into 6V6 guitar amps but they are not ideal.
  
 http://www.antiqueradios.com/forums/viewtopic.php?f=6&t=91062 (just watch out for the shade they throw at us audioph00ls).
  
 We might be coursing some uncharted territory with rolling the power tubes. Most of the discussions I've found about replacing 6V6s, 6W6s, 6L6s, etc. seem to apply to guitar amps or restoring vintage electronics. The only other modern, mass-produced amps I've seen that uses these octal power tubes are all-in-one Chi-Fi designs like this one, and I've seen no rolling discussions about them:
  
 http://www.china-hifi-audio.com/en/yaqin-tube-amp-audio-c-14/yaqin-ms-6v6-hi-fi-vacuum-tube-integrated-amplifier-new-p-154


----------



## CZ4A

I hate to triple-post, but I have some more info for all you tube rollers out there.
  
 First, my quartet of NOS Amperex 8416s I won from eBay arrived today. I've plugged one in with my CBS 6W6s.
  

  
 Not only am I happy to report that the 8416 works in this amp, it sounds great! I'm still new at describing sound and there aren't any other 8416 reviews out there to glean from (on the other hand, I have to bias my opinion with), so bear with me. This is easily one of the most detailed tubes I've rolled. Highs are crisp without being piercing, has a good grip on bass, good attack. The 8416 is pricey and rare, but if you have the means, I highly recommend giving one a try!
  
 Second, I've been on the hunt for another type of power tube to roll besides my 6W6GTs and 6V6GTs. Something in a shape other than a plain-Jane GT bottle, maybe. I sent out an e-mail to Gemtune and this was their answer:


> Yes,it may can supply for 6W6 tube,but it can't handle kt66,el34 and 6550 tubes.Thanks.


 
 I wasn't able to get an actual amperage number, but based on the 6W6's amp draw, it look like 1.2A per power tube is the upper limit of the transformers. Someone earlier said Gemtune told them 6Y6 would work- that draws 1.25A, so that _maybe_ might work. Goes to show that it's important to read the datasheets before rolling.
  
 Unless anyone here wants to put their PA1502A on the line with a KT66 (1.3A) or above. For science. You monster.


----------



## 1800yolk

cz4a said:


> I hate to triple-post, but I have some more info for all you tube rollers out there.
> 
> First, my quartet of NOS Amperex 8416s I won from eBay arrived today. I've plugged one in with my CBS 6W6s.
> 
> ...




are you sure it's 1.2 amps and not 0.012 amps? I'm still learning about tubes in general and could be wrong, but if the tube can only handle about 2 watts..? I will do more reading though


----------



## CZ4A

1800yolk said:


> are you sure it's 1.2 amps and not 0.012 amps? I'm still learning about tubes in general and could be wrong, but if the tube can only handle about 2 watts..? I will do more reading though


 

 When I talk about amps, I'm talking about how much current a particular tube's heater (filament) draws from the amplifier in either amperes (1.2A) or milliamperes (1200mA). If a tube's heater current rating is too high, it will damage the transformer or other power supply.


----------



## JordiMB

Is this little amplifier a better value than the Little Dot Mk II, or similar? Don't know if you have any experience with both, to compare. Thanks.


----------



## Wantat Chin

hi all, i am decided to purchase this mini tube amp as my first tube amp, and i saw there is a 6v6>el84 socket, does it make improvement to use el84 instead of 6v6?


----------



## canthearyou

FYI I just listed mine for sale with a few extra tubes. It is a great amp, but I recently purchased a HE-500 and need to move some stuff to get a more powerful amp.


----------



## 1800yolk

canthearyou said:


> FYI I just listed mine for sale with a few extra tubes. It is a great amp, but I recently purchased a HE-500 and need to move some stuff to get a more powerful amp.


 
  
 3 ohms extra resistance over the 400i's, i hope i don't have this issue as well. People on this thread like this amp with the 400i's, but until i listen myself.. some of my vinyl rips are on the quiet end, so we'll see D:


----------



## canthearyou

1800yolk said:


> 3 ohms extra resistance over the 400i's, i hope i don't have this issue as well. People on this thread like this amp with the 400i's, but until i listen myself.. some of my vinyl rips are on the quiet end, so we'll see D:




But it has -6db sensitivity.


----------



## 1800yolk

canthearyou said:


> But it has -6db sensitivity.


 

 oh good point. i am considerably less worried now ha


----------



## canthearyou

1800yolk said:


> oh good point. i am considerably less worried now ha




It sounds amazing with the 400i IMO and gets plenty loud on low gain.


----------



## CZ4A

Question for the current and prospective PA1502A owners reading this thread: Would you prefer it if I made a separate tube rolling thread? That way I can gather all of the info in from Gemtune and from my own research into the first post instead of it being scattered around.


----------



## a44100Hz

If someone wants a silver one of these with some tubes drop me a line. (It's good; just don't need it anymore.)


----------



## 1800yolk

cz4a said:


> Question for the current and prospective PA1502A owners reading this thread: Would you prefer it if I made a separate tube rolling thread? That way I can gather all of the info in from Gemtune and from my own research into the first post instead of it being scattered around.


 

 i like that you are posting your findings here, since it relates directly to the amp we are all interested in. You could always do both though! But my vote would be to put the focus here mostly. As our tube rolling adventures continue, this forum will grow and more people will pay attention to this little-known amp, and more will get it, tube roll.. and then talk about it here! it's like an investment if you think about it. appreciate the info you've provided so far, should be getting my amp soon and will be going over posts again to figure out what tubes i'll shoot for first.


----------



## chellity

cz4a said:


> Question for the current and prospective PA1502A owners reading this thread: Would you prefer it if I made a separate tube rolling thread? That way I can gather all of the info in from Gemtune and from my own research into the first post instead of it being scattered around.


 
  
 i'm down  would make it easier to see all the tube related info.


----------



## Preludio

.


----------



## Preludio

braaam said:


> Interesting, didn't know these types could be used as well.
> 
> I went all French today: RT 6189 with the Visseaux 6F6. The RT is a military 12au7 screened for low noise. Very transparant and resolving with tight bass. A bit rolled off in the highs and a bit of sweetness in the mids. A great tube that fits a lot of styles.
> 
> ...


 
 Hi, how was the soundstage imaging performance? compared to amperex dario philips?...


----------



## Preludio

High guys!, any opinions about this tubes?
  
 12at7 RCA grey plate, aprox 22 USD. They're in my country so no extra shipping cost...
  
 http://articulo.mercadolibre.com.pe/MPE-418158370-tubo-valvula-rca-12at7-grey-plate-nos-new-old-stock-_JM


----------



## yangian

How about this compared with LDIII or DV336? And how about it for HD600?


----------



## canthearyou

This little amp keeps surprising me. It does pretty well with the HE-500.


----------



## CZ4A

chellity said:


> i'm down  would make it easier to see all the tube related info.


 
  


1800yolk said:


> i like that you are posting your findings here, since it relates directly to the amp we are all interested in. You could always do both though! But my vote would be to put the focus here mostly. As our tube rolling adventures continue, this forum will grow and more people will pay attention to this little-known amp, and more will get it, tube roll.. and then talk about it here! it's like an investment if you think about it. appreciate the info you've provided so far, should be getting my amp soon and will be going over posts again to figure out what tubes i'll shoot for first.


 
  
 I think what I'll do is compile all the technical information we have here and put it in a separate thread. That way we have a one-stop shop for rolling info instead of leaving it all scattered.
  
 Of course, I've been busy rolling new stuff too...


----------



## 1800yolk

anybody know what this stuff is?


 i don't have headphones to even test this out with, definitely doesn't look right though.
  
 EDIT: I'm a dum dum. ignore this post!


----------



## InAndOut

Got this little baby on the last MassDrop and am loving it! Looking at some new tubes on Amazon. I think I'm going to go with a JJ 12AU7 Long Plate. And to the poster above, my left tube was a little unseated when it first arrived. I think the black covers around the Power tubes are just for show. I do like how the stock tubes have a tint to them.


----------



## 1800yolk

anybody know what wattage this pumps out at any given impedance? Thanks
  
 EDIT:
 according to a rando user in the massdrop discussion:
  
 Afterman:
  Seems to be pretty good with power. Thinking of getting it. I like how it looks.
 1W @ 32ohms
 500mw @ 100ohms
 260mw @ 300ohms
 130mw @ 600ohms

  
 so my calculation of 2.5W matches up close enough i guess, 2-2.5W
  
 EDIT 2:
 those numbers are probably on high gain, dunno what low gain would look like.
  
 EDIT 3:
 I think ultimately those numbers don't matter, what matters is whether or not we can get the volume we want without distortion, and as soon as i get some cans hooked up to this amp i will report back. still waiting on my dac to ship too. it being a transformer coupled amp, i think it will pair well with any low impedance cans, as many people have stated before me.


----------



## 1800yolk

also, this was an interesting read. It clearly isn't the same app, but it definitely has to be made by appj. it consumes more power and is meant to drive speakers, but a few points that were interesting to me were:
  
 "It also gives better performance, with the same regulated outputs regardless of inputs, brownouts or poor house wiring, and it drives the heaters with DC, not AC, so there's much less room for any hum. I tested it from 100 ~ 135 VAC, and saw no difference in heater brightness, power consumption, distortion or power output. This little jewel is completely immune to power supply variance, which few if any audio power amplifiers are."
  
 and
  
 It's microphonic: when tested into dummy loads in the lab, the transformers make sound, and playing test tones through speakers you may hear the innards of the tubes rattling.
  
 also, he includes instructions on how to turn that amp into a monoblock amp. might be useful if you know what you're doing
  
 also, my guess is that because peak to peak voltage is 18V, that should mean total output is 2.5 Watts. What I'm unsure of is whether or not each channel attains that peak to peak, or if that is combined. shows how much i know about electronics.


----------



## DarthTater

I've been listening to mine for several days.  With a pair of Beyerdynamic DT880s (250 ohms, I think) on high gain, it sounded pretty pedestrian.  I don't mean that in a bad way, just that it didn't particularly move me.  On low gain, it seemed kind of "closed up" to me; that is, it felt a little compressed, without a lot of dynamic punch.
  
 Today I replaced the tubes with new manufacture Gold Lion ECC82 and a matched paiar of Electro-Harmonix 6V6GTs.  That made a pretty huge difference in terms of dynamic range, openness and soundstage.  I don't mean to imply that it turned a relatively bargain basement amp into an audiophile triumph, but I think that it's fighting above its weight at this point.
  
 I find that the amplifier complements my Grado SR-225e's as well.  The bottom end is a bit rolled off, as you might expect, but on small group jazz recordings, particularly live ones, man, this thing really sounds great.  A lot of detail is there.

 I think that even with the extra expense of replacing the tubes, this was a good deal through Massdrop.
  
 The amp that 1800yolk described in the previous post sounds like the 1501A.  I use one of those to drive an old set of Stax SR-40s.  I replaced the stock tubes with some Zenith 6AD10s on the cheap and I really like it.  Other than running hotter than the dickens, it's a fun little micro amp.


----------



## Halazzi

A few quick observations after a week of office use, my apologies for being somewhat new to this and not having the full vernacular.
 
I had already picked up a NOS RCA preamp tube and a pair of 6V6G 1940s Westinghouse power tubes before the amp arrived so this is based only on using the NOS tubes, not the supplied ones. The 6V6G tubes are a little taller than the towers on the amp, I thought it made for a nice visual pairing (sorry no picture rights yet).
 
Having tried it with a few headphones, for whatever reason it seems to play better with orthos on high gain (400i, Mad Dog 3.2) than my Nighthawk on either gain setting. I do not have any other dynamics so I am not sure if it is just better with orthos or something specific with the Nighthawk.
 
In terms of sound quality, running ODAC -> 1502A -> 400i or Mad Dog was shockingly close (given the price disparity) to my home setup of Herus -> Valhalla 2. Not quite there, but much closer than I would have expected.


----------



## CZ4A

So I said I would post some more tube rolling results here. First of all, I got two new pairs of power output tubes - a pair of matched, nearly-new Tung-Sol Reissue KT66s (seller said they only had about 2 hours of use on them) and a used pair of 50's Soviet 6P3S tubes. "Wait," you say, "didn't you post earlier that KT66s draw too much current?" Well, the T-S KT66 is essentially the guts of their 6L6GC stuffed into a KT88 bottle, which also means the heaters draw only 0.9A, well within the PA1502A's capabilities. All of the other KT66s I looked at, both new and vintage, draw 1.3A, so they can't be used in this amp. Unfortunately, I lost the pictures I took of them. I will post them up later.
  
 The 6P3S tubes are the Soviet copy of the 6L6G. Most are the straight-glass type, but there are still a few Coke bottle types around. Like these:
  

  
 The 6P3S-E is a military version with extended life and higher plate/screen voltages like a 6L6GA. Electrically, the extra headroom isn't necessary in the APPJ because it isn't going to push its power tubes like a guitar amp. I don't know if there is any sonic difference between the 6P3S and 6P3S-E though. I can say these open up the soundstage a lot. And they're cheap. They may not be as good as some NOS American and European tubes, but they definitely are an improvement over the stock 6P6Ps and certainly hold their own.
  
 I've collected up a few 12SN7GTs from various sources. The 12SN7 is the same as the famous 6SN7 except for the heater voltage, and since there are fewer applications for the 12V tubes, they tend to be cheaper. A 12SN7 to 12AU7 adapter is needed, but I'm stoked to say the 12SN7GT works in the APPJ!
  

 T00bheads will recognize the power tube as the famous Tung-Sol Round Plate Black Glass. It fits with the 6P3Ss, too!
  

  
 There's not a lot of space between the 12SN7 and the 6P3Ss, but that's because I went for the ST bottles. Straight bottle tubes will leave more space. Maybe the extra heat will lessen the 12SN7's life, but frankly I'm not that worried since the amp is open everywhere except for the transformer covers. If this were a closed amp I'd be more concerned. Plus, the 12SN7 + 6P3S combo just sounds awesome.


----------



## 1800yolk

i just got my 400i in the mail and all i have to say for now is that there's a sssssssnake in my boot! and i hope changing tubes helps with that. either that, or maybe stop wearing earplugs at concerts..
  
 EDIT:
 what i meant to say here is the sibilance is monstrously bad at times. gotta find some tubes that mitigate this.


----------



## Qurzo

cz4a said:


> So I said I would post some more tube rolling results here. First of all, I got two new pairs of power output tubes - a pair of matched, nearly-new Tung-Sol Reissue KT66s (seller said they only had about 2 hours of use on them) and a used pair of 50's Soviet 6P3S tubes. "Wait," you say, "didn't you post earlier that KT66s draw too much current?" Well, the T-S KT66 is essentially the guts of their 6L6GC stuffed into a KT88 bottle, which also means the heaters draw only 0.9A, well within the PA1502A's capabilities. All of the other KT66s I looked at, both new and vintage, draw 1.3A, so they can't be used in this amp. Unfortunately, I lost the pictures I took of them. I will post them up later.


 
  
 How did it work with the Tung-Sol KT66's?


----------



## AzraelDarkangel

Anyone compare this amp to a Little Dot 1+?


----------



## wirewizard

I purchased one from massdrop and the left channel had very loud static. I replaced all the tubes...still static on the left channel...sent back for refund.


----------



## canthearyou

wirewizard said:


> I purchased one from massdrop and the left channel had very loud static. I replaced all the tubes...still static on the left channel...sent back for refund.




How come you didn't get a replacement?


----------



## wirewizard

I did not get a replacement because I already waited a month for the massdrop order/delivery process and massdrop said a replacement could take several weeks to arrive and I did not want to wait.


----------



## canthearyou

wirewizard said:


> I did not get a replacement because I already waited a month for the massdrop order/delivery process and massdrop said a replacement could take several weeks to arrive and I did not want to wait.




Bummer.


----------



## AzraelDarkangel

I have a Little Dot 1+ now, just curious about the Gemtune. Ultimately I want a balanced tube amp, but those start around $1000.


----------



## canthearyou

The soundstage of this amp with the Gold Lion power tubes and Mullard pre-amp tube is amazing! It sounds fantastic with the HE-500. I am still enjoying this amp more than the H10. The H10 may* sound a little cleaner, but the sound is flat, without much depth.


----------



## wirewizard

I own the Little Dot 1+ and it sounds better than the APPJ especially at the frequency extremes. Also the Little Dot 1+ is dead quiet.


----------



## 1800yolk

wirewizard said:


> I own the Little Dot 1+ and it sounds better than the APPJ especially at the frequency extremes. Also the Little Dot 1+ is dead quiet.


 

 the appj seems to be dead quiet, at least on low gain. Both amps are designed for low impedance, high current cans (so planar headphones are ideal matches)
  
 also, taking advice from one of the few people that got a faulty unit isn't a great idea, with the exception of taking into account the product reliability. The rest of us are enjoying our APPJs, but I couldn't say whether it is better than the Little Dot.


----------



## wirewizard

The static was intermittent and when there was no static in the left channel it still was not as silent as the Little Dot 1+. Also when there was no static the APPJ did sound good, but it did not sound as good as the Little Dot 1+. This is my 3rd APPJ product and 2/3 have been defective.


----------



## 1800yolk

wirewizard said:


> The static was intermittent and when there was no static in the left channel it still was not as silent as the Little Dot 1+. Also when there was no static the APPJ did sound good, but it did not sound as good as the Little Dot 1+. This is my 3rd APPJ product and 2/3 have been defective.


 

 oh ok, fair assessments then. it's a bummer that happened, maybe you have a really angry UPS guy, or maybe the APPJ needs some quality control.


----------



## wirewizard

I wish it was not defective as it had a nice easy on the ear sound;perfect for long listening sessions. I think APPJ has quality control issues.


----------



## AzraelDarkangel

Both products are low cost Chinese tube amps so quality control is not always the best. Also so many factors have to do with hum issues, I can induce more hum in my Little Dot just waving my hand near it. Power conditioning and better power cord would probably help, also mine is near a telephone, may be causing minor interference. It doesn't hum bad but I can hear a low level hum all the time if nothing is playing. Different tubes have no effect.
  
 Also in saying one is better sounding than the other would be difficult anyway since tubes have such a profound effect on the sound and op amp too in the Little Dot. You would have to find the best tubes for each and have a shoot out. Also, I believe the Gemtune is a full tube amp but the Little Dot is a hybrid with tubed preamp. So the Little Dot may just be better at frequency extremes.


----------



## Kramertc

I own both (APPJ and Little Dot I+) and in my case the APPJ is dead quiet while the Little Dot has a faint buzz that comes and goes.  This buzz isn't present all the time.
 I've even swapped places/power cords but the buzz is still there.  Even swapped tubes on the LD to no effect.
  
 While I haven't been able to eliminate the faint buzz I still like them both a lot.  The buzz from the LD doesn't bother me as it's not always present and when it comes its so faint it's only audible if no music is playing. 
  
 At this stage of my early ownership of both I prefer the APPJ. The sound is slightly less congested than the LD but I also suspect that it's the tubes in the APPJ that are making the difference.
 I have an Amperex Bugle Boy in the APPJ while the LD has the cheapest russian tubes I could buy (Voskhod but not the "-EV" model that's everyone raves about).


----------



## CZ4A

Quote:


qurzo said:


> How did it work with the Tung-Sol KT66's?


 
 I have to give them another listen since I haven't in a while. What I do remember is the soundstage is massive, but some mid or mid-lows sounded distant, almost like they were being played farther away than the rest of the music (recessed I think is the correct term?). The preamp tube probably has an effect on this too- IIRC I was using the 8416 most of the time and another type of tube may compensate for this. SECOND EDIT: May have been the recording? I listened with the 8416 and a GE black plate 5751 and didn't get that recessed feeling on some mids I thought I had heard.
  
 Physically, the T-S KT66s are very wide- you can't use 12SN7-types in the preamp socket as the KT66s will foul against the 12SN7's base.
  
 EDIT: Here's a picture.


----------



## 1800yolk

terrynj said:


> I use the Hi-gain on mine ...I agree with Braam, it doesn't sound as good in low gain. My DAC also allows me to use the volume on it, so I turn my appj up to 75%, and run my DAC around 10%-20%...everything seems to work pretty good that way! I think you get more headroom from the amp.


 

 i'm in the same boat, high gain w/ 400is = less sibilance and more balanced sound. Planars need all the juice they can get!


----------



## Preludio

It finally arrived! i'm really happy with the sound of my set . Thanks for the great advice! The RCA NOS Grey Plate works fine, maybe i'll roll the power tubes soon . Those big Tung sol's looks awesome o.o!


----------



## 1800yolk

this is already on massdrop again if anyone missed it before
 https://www.massdrop.com/buy/appj-1502a-tube-headphone-amplifier
  
 still researching tubes. I have seen a few people mention that the tubes this comes with are pretty ok. maybe mine still need burn in, but i can't stand having stock. Sibilance is a huge issue, and distortion happens pretty frequently w/ my 400i. But it is silent, I can attest to that.


----------



## stolikat

Just got in on the drop. I have some RCA clear tops that I hope will sound awesome with this. Now what power tubes to buy....


----------



## stolikat

RCA clear tops for the preamp for sure.


----------



## Zulkr9

cz4a said:


> I have to give them another listen since I haven't in a while. What I do remember is the soundstage is massive, but some mid or mid-lows sounded distant, almost like they were being played farther away than the rest of the music (recessed I think is the correct term?). The preamp tube probably has an effect on this too- IIRC I was using the 8416 most of the time and another type of tube may compensate for this. SECOND EDIT: May have been the recording? I listened with the 8416 and a GE black plate 5751 and didn't get that recessed feeling on some mids I thought I had heard.
> 
> Physically, the T-S KT66s are very wide- you can't use 12SN7-types in the preamp socket as the KT66s will foul against the 12SN7's base.
> 
> EDIT: Here's a picture.


 
 Does the KT66 work without any problems ? someone said that it draws too much current and the transformers of the little amp can't handle it. 

 TIA


----------



## Kryl0071

Hi! 
I got one. This is really good amplifier. I was skeptical, but decided to try it. You must take several steps to improve the sound. First - replace the two coupling capacitors to wima mkp4 0.47 µf pitch of 15 mm. Secondly, to replace two electrolytic capacitors in the cathode of the tubes at Slimic ELNA 220uF 25V. The third is to replace all the tubes in accordance with your choice.


----------



## Terrynj

zulkr9 said:


> Does the KT66 work without any problems ? someone said that it draws too much current and the transformers of the little amp can't handle it.
> 
> TIA


 
 I never would have thought you could run those in the 1502a? The big McIntosh AMPs run KT88's in them... I am very new to tube rolling, and have played it fairly safe, but I would love to try these!


----------



## CZ4A

zulkr9 said:


> Does the KT66 work without any problems ? someone said that it draws too much current and the transformers of the little amp can't handle it.
> 
> 
> TIA







terrynj said:


> I never would have thought you could run those in the 1502a? The big McIntosh AMPs run KT88's in them... I am very new to tube rolling, and have played it fairly safe, but I would love to try these!




Only the Tung-Sol Reissue KT66s will work on the PA1502A. Please read my reply for an explanation.



cz4a said:


> So I said I would post some more tube rolling results here. First of all, I got two new pairs of power output tubes - a pair of matched, nearly-new Tung-Sol Reissue KT66s (seller said they only had about 2 hours of use on them) and a used pair of 50's Soviet 6P3S tubes. "Wait," you say, "didn't you post earlier that KT66s draw too much current?" Well, *the T-S KT66 is essentially the guts of their 6L6GC stuffed into a KT88 bottle, which also means the heaters draw only 0.9A, well within the PA1502A's capabilities. All of the other KT66s I looked at, both new and vintage, draw 1.3A, so they can't be used in this amp.*


----------



## stolikat

So massdrop is shipping my amp on 4/22 and I am sure that there will be more people poking around here in the coming days. I see that people are in to those E/H KT66's but what would be a good value tube to try? I already have some 12UA7 RCA clear tops but I am unsure what budget 6V6 I should try...


----------



## Kryl0071

I put RCA 5751 and RCA 6V6GT. Sound superb!!! But I have changed capacitors also.


----------



## CZ4A

kryl0071 said:


> I put RCA 5751 and RCA 6V6GT. Sound superb!!! But I have changed capacitors also.




What caps did you use?


----------



## Kryl0071

Post#219


----------



## CZ4A

kryl0071 said:


> Post#219




Derp, I should have looked for that post first! :blink:


----------



## stolikat

Well this next massdrop buy is hitting. Friday I should have my amp. Excited!


----------



## RoyT

Friend, can you please be more specific?
 can you show the coupling capacitors and the electrolytic capacitors that need to be change on the pcb?
 and maybe explain how to change them? do you need to weld them? not sure how this works and how complicated it will be..
  

  

  
  
  
  
 this is the capacitors needed right?
  
 http://www.ebay.com/itm/10pcs-WIMA-MKP4-0-47uF-0-47-F-250V-5-pitch-15mm-Capacitor-MKP4F034704D00JSSD-/151467637676?hash=item23442cbbac:g:RrUAAOSw54xUXJBQ
 +
 http://www.ebay.com/itm/2pcs-Japan-ELNA-SILMIC-II-RFS-Silk-Audio-Capacitor-Hi-Fi-/131210031524?var=&hash=item1e8cba31a4m6gW9gn3bdPvB97gb9a7IMA
  
 Any help with this would be greatly appreciated, and i'm sure not only to me..
  
 Thanks!


----------



## Kryl0071

Yes, you find right WIMA but I not recommend to buy Elna in China. It could be a fake. You have to change 2 electrolytic capacitors and 2 coupling cap. up front of the pcb.


----------



## RoyT

You mean the one's i marked in red?
 i can only see one electrolytic capacitors in front, where is the other one?
 this things need to be weld right?


----------



## Kryl0071

No, it's not these. Electrolytic capacitors is two brown barrel next to the vacuum tubes and coupling capacitors two white next to them.


----------



## RoyT

Okay i think i got it now:
  

 right?
  
 How do you connect them? do you need a welding machine for this? or you just unplug the old one's and plug the new one's?
 sorry for all the questions, it's not my strong suit..


----------



## Kryl0071

Gotcha! Now is correct!
I think you have to ask somebody who is DIY person to help you desolder old ones and solder in a new caps.


----------



## Qurzo

Anybody knows if these 6V6GT's ('58&'59) are any good? They are matched en tested.
  
https://www.dropbox.com/s/gm9bf9v0i6qi1i7/20160428_211249.jpg?dl=0


----------



## RoyT

Great, I'll manage somehow with the installation, thanks!
 i see you have the X2's, can you clearly hear a difference between the tube and a solid state on them?


----------



## Kryl0071

I do not have solid state amp.


----------



## RoyT

Yet...


----------



## stolikat

I got my amp today a day late. I have it burning in now. I have the stock tubes in to see how they sound but I will roll the 12au7 to an RCA clear top I have. I am still on the fence with regards to 6v6 tubes. Any massdrop guys out there?
  
 Update
  
 So using my RCA preamp tube the mids and highs are nice. Seems like the bass is a little lacking but maybe that is just Iron Maiden. So far so good but I know now that I must decide what 6v6 tubes to get.


----------



## Kryl0071

No, to get better bass you have to change capacitors. This is only the way how you can improve the bass.


----------



## CZ4A

kryl0071 said:


> No, to get better bass you have to change capacitors. This is only the way how you can improve the bass.




+1. I've tried many different combinations of tubes and while they do have some effect, none of them truly compensate for the lack of bass.

Upgrading the capacitors is definitely on my to-do list, I just need the time to get around to it.


----------



## Kryl0071

Do it ASAP and after you will done, you will need to burn up 1502 for about 48-72 hours with music on.


----------



## stolikat

Well I just have to say that the tubes that come with this amp are not bad at all. They are made by Shuguang and the 12ax7 actually gets good reviews. It is definitely harder hitting on the low end than my 12au7 RCA clear top. I clearly have no point of reference with regards to the 6v6's as I have yet to order any. I keep going back and forth between those two tubes and the more I burn in the Shuguang the more I am liking it.
  
 Update. I just went back to my indeed G3. These power tubes are definitely holding back the sound stage presence.


----------



## stolikat

Sad to see that this thread has gone dead even though massdrop keeps selling this amp. I just grabbed some JJ Tesla 6V6's and this sweet Sylvania 12ax7. Cant wait!


----------



## 1800yolk

royt said:


> Great, I'll manage somehow with the installation, thanks!
> i see you have the X2's, can you clearly hear a difference between the tube and a solid state on them?


 

 from your comments it appears you have never done electronics work like this? if this is the case, I would recommend you find someone who already has, since you wouldn't want to goof up your motherboard. Also, working with capacitors is dangerous because they need to be grounded first, and I'm unaware of how long it takes to slowly ground itself when left unplugged for a period of time. If you do try grounding them, electrically insulated gloves might be a good thing to have. Possibly a tad overkill given the size of the capacitors, but still not a bad idea.


----------



## alexandertm8

cz4a said:


> ...
> I've collected up a few 12SN7GTs from various sources. The 12SN7 is the same as the famous 6SN7 except for the heater voltage, and since there are fewer applications for the 12V tubes, they tend to be cheaper. A 12SN7 to 12AU7 adapter is needed, but I'm stoked to say the 12SN7GT works in the APPJ!
> 
> ...


 

 Did you do any modification in the circuit or just plug-n-play?
 I can't locate any of the famous 12sn7gt Tung-Sols in Europe and I'm reading that the rest 12sn7 aren't any good, do you have a opinion on that matter? Would you trust/place a 12sn7gt/a JAN General Electric on the appj?


----------



## AzraelDarkangel

cz4a said:


> I have to give them another listen since I haven't in a while. What I do remember is the soundstage is massive, but some mid or mid-lows sounded distant, almost like they were being played farther away than the rest of the music (recessed I think is the correct term?). The preamp tube probably has an effect on this too- IIRC I was using the 8416 most of the time and another type of tube may compensate for this. SECOND EDIT: May have been the recording? I listened with the 8416 and a GE black plate 5751 and didn't get that recessed feeling on some mids I thought I had heard.
> 
> Physically, the T-S KT66s are very wide- you can't use 12SN7-types in the preamp socket as the KT66s will foul against the 12SN7's base.
> 
> EDIT: Here's a picture.


 
  
 There is something mildly erotic about such a cute little amp with such massive tubes....or I might just have an issue.


----------



## CZ4A

alexandertm8 said:


> Did you do any modification in the circuit or just plug-n-play?
> 
> I can't locate any of the famous 12sn7gt Tung-Sols in Europe and I'm reading that the rest 12sn7 aren't any good, do you have a opinion on that matter? Would you trust/place a 12sn7gt/a JAN General Electric on the appj?




No circuit modifications required, just the adapter.

12SN7s are identical to their 6SN7 equivalents except for the heater voltage and current draw. That GE 12SN7GTA you mention should have the same sonic qualities as a GE 6SN7GTA, a Sylvania "Bad Boy" 12SN7 will sound like a "Bad Boy" 6SN7, etc. My Tung-Sol round plate 6SN7 and 12SN7 definitely sound similar given they are used in two different amps (Sunrise III and APPJ).

Will the GE work? With the correct adapter, sure. Will it sound good? I don't know. I've never listened to a GE 6/12SN7 but Googling reviews for the 6SN7GTA should bring up something.


----------



## alexandertm8

cz4a said:


> No circuit modifications required, just the adapter.
> 
> ...
> 
> Will the GE work? With the correct adapter, sure. Will it sound good? I don't know. I've never listened to a GE 6/12SN7 but Googling reviews for the 6SN7GTA should bring up something.


 
 Thanks for the reply! What kind of adapter should I be looking for? I 've found a few 12SN7 to 12AU7 on ebay but the specify "...Cautions: Do not use 12V adapter on 6V circuit!".


----------



## CZ4A

alexandertm8 said:


> Thanks for the reply! What kind of adapter should I be looking for? I 've found a few 12SN7 to 12AU7 on ebay but the specify "...Cautions: Do not use 12V adapter on 6V circuit!".




This is the adapter I have:

http://www.ebay.com/itm/1pc-12SN7-12SL7-TO-12AU7-12AX7-tube-adapter-for-you-amp-12-6V-heat-/200943948306

Remember, the preamp (12AX7/6N4-P) tube runs on a 12V circuit, while the power tubes (6V6GT/6P6P) tubes run on a 6V circuit.


----------



## Zulkr9

Just wondering if the transformers are modified can it handle KT88/KT66 the ones with the 1.3A heater current ?


----------



## alexandertm8

Just received mine, left channel dead. Pretty disappointing, was expecting it with high hopes. Low volume output too!

 P.S. Its a bad tube, already order another couple.


----------



## Josh-Fi

cz4a said:


> No circuit modifications required, just the adapter.
> 
> 12SN7s are identical to their 6SN7 equivalents except for the heater voltage and current draw. That GE 12SN7GTA you mention should have the same sonic qualities as a GE 6SN7GTA, a Sylvania "Bad Boy" 12SN7 will sound like a "Bad Boy" 6SN7, etc. My Tung-Sol round plate 6SN7 and 12SN7 definitely sound similar given they are used in two different amps (Sunrise III and APPJ).
> 
> Will the GE work? With the correct adapter, sure. Will it sound good? I don't know. I've never listened to a GE 6/12SN7 but Googling reviews for the 6SN7GTA should bring up something.




Hey you mentioned early in the thread that you'd compare the sound quality with the Sunrise. Can you give an honest comparison please? I wonder how the otl mosfet output compares to the transformers of the appj 

I'd assume the transfoemer would have more purity to the sound instead of a high frequency switcher.


----------



## kazcou

I ordered this converter on ebay (6SN7 > 12AX7 12,6V)
http://www.ebay.com/itm/1pcs-6SN7-Replace-12AU7-Tube-Amplifier-Socket-Adapter-12-6V-Suzier-A4/281951474478?_trksid=p2054502.c100229.m3211&_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20140505115423%26meid%3Db0c9127746164f709a59239de1f4eadd%26pid%3D100229%26rk%3D1%26rkt%3D15%26sd%3D281951474478
  
 hope it will work and not kill the tube or the amp


----------



## Saillaw

royt said:


> Okay i think i got it now:
> 
> 
> right?
> ...


 
  
 Hello RoyT,
  
 Did you ever give this a try?   I'm curious about the removal/installation difficulty, how did it go?  I'm not the best at small soldering, but have a neighbor who is a wiz I can bribe to help if the sound is improved enough to merit the effort?


----------



## CZ4A

kazcou said:


> I ordered this converter on ebay (6SN7 > 12AX7 12,6V)
> http://www.ebay.com/itm/1pcs-6SN7-Replace-12AU7-Tube-Amplifier-Socket-Adapter-12-6V-Suzier-A4/281951474478?_trksid=p2054502.c100229.m3211&_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20140505115423%26meid%3Db0c9127746164f709a59239de1f4eadd%26pid%3D100229%26rk%3D1%26rkt%3D15%26sd%3D281951474478
> 
> hope it will work and not kill the tube or the amp




Interesting. I didn't know there was a 6SN7 to 12AX7 adapter that runs on 12.6V. That would open things up immensely for tube options because now you can run 6SN7s and any other types that could be adapted to work in a 6SN7 circuit.




josh-fi said:


> Hey you mentioned early in the thread that you'd compare the sound quality with the Sunrise. Can you give an honest comparison please? I wonder how the otl mosfet output compares to the transformers of the appj
> 
> I'd assume the transfoemer would have more purity to the sound instead of a high frequency switcher.




My Sunrise is at work. I will try to bring it home on a open weekend and do a back-to-back comparison.


----------



## 1800yolk

kryl0071 said:


> Hi!
> I got one. This is really good amplifier. I was skeptical, but decided to try it. You must take several steps to improve the sound. First - replace the two coupling capacitors to wima mkp4 0.47 µf pitch of 15 mm. Secondly, to replace two electrolytic capacitors in the cathode of the tubes at Slimic ELNA 220uF 25V. The third is to replace all the tubes in accordance with your choice.


 
  
 for the First item, what should the nominal voltage of the coupling capacitors be? Thanks!


----------



## Kryl0071

60v in this point so use wima mkp 0,47uF 250V


----------



## eluslve

could you use muse caps instead of elnas??


----------



## Kryl0071

Yes, of course! It is better to take 470uF 25V Nichicon KZ 470uF or Elna Slimic.


----------



## eluslve

if 470 muse caps are used, what voltage coupling caps should I consider?


----------



## Kryl0071

Coupling caps WIMA MKP 0,45uF 250v only. Do not use electrolytic caps!!!!!


----------



## stolikat

Static. Do any of you get a fair amount?


----------



## sealykojac

I recently bought one of these off Amazon and really liked the sound but it's going back. I've been experiencing issues with the left channel dropping out after an extended period of use. Everything would work great for two hours then the left channel would just go silent. I switched tubes and still would lose the left side. Turn it off, let it sit for 10 minutes, turn it back on and once again good for a few hours then it would drop again. Might try a Project amp instead of gambling on another one of these.


----------



## Maxx134

stolikat said:


> Sad to see that this thread has gone dead even though massdrop keeps selling this amp. I just grabbed some JJ Tesla 6V6's and this sweet Sylvania 12ax7. Cant wait!




I was looking into maybe a Vali2 for a low cost second amp, to use as a "burn-in" amp for headphones and maybe tubes...
Then was looking at project ember hybrid, which I already knew..
I have the "O2" amp which I already rolled opamps but wanted better.

In stumbled upon this unit and it is perfect suited to my needs while giving maximum tube rolling for a small amp..












The stock WIMA coupling caps are very nice , soft , neutral .
The stock sound is also very good.
The Tung-sol reissue newn stock KT88 in picture is alsl a cryset pair..
It is better but not as good as NOS National Union 6L6 ..

The sockets are hard to swap so I would get socket savers.

For driver tube a Valvo e180cc pinch waist preferred over all.

The sonic level is more juicy and almost surpassing level of a "project ember" in some traits, notably the liveliness.

I know very well the sonic traits of the WIMA coupling caps from my past amp mods, so I full expect that doing the Cap upgrade suggested by "Kryl0071" should send this unit into seriously good sound territory.

This tiny amp once upgraded will put to shame many mid grade tube amps...


----------



## Kryl0071

+100%


----------



## Maxx134

I very curious as to why they used surface mount parts on socket side of board, 
And what are those solid state devices doing by the output tubes,
And what are the heater current limits for driver tube...

I will eventually open to install some nice coupling caps first...


----------



## Kryl0071

Coupling caps and cathode caps in same time.


----------



## Maxx134

kryl0071 said:


> Coupling caps and cathode caps in same time.




Agree..
 But I will do a bit more and post pics...


Round two with stock amp( w/nos tubes) versus Project Ember( w/nos tube)...

 This time ember wins in soundstage "distance" and elevated treble presence...
Edit: 
Change to the New Production Tung-sol KT-66 would make very similar as it also had more distance and treble, but was not burned in.
The point is tube rolling will make one or the other seem nicer.


Soundstage size still deeper on this amp.
Also more linear tonality whereas Ember have a bit pronounced bass & a slight distant mids.

 I am fairly certain the stock configuration is holding this baby back..


----------



## Kryl0071

Very interesting. Let us know what you done.


----------



## Keeter

Hello,
 I'm a newb to Head-Fi. I'm wondering if anyone has any experiences using Sennheiser HD600s with the APPJ PM1502A. I'm intrigued by this amp and encouraged by what I've read in the few reviews that I could find. Right now I'm using a Bravo Ocean with a NOS GE 12AU7 and it sounds quite nice but the sound stage is pretty flat. I had a Schiit Magni 2 Uber for a while and really didn't like it with my HD600s. It sounded too clinical and thin. I find that the Ocean provides a bigger, more organic sound but the sonic landscape seems kind of one dimensional. What I'm looking for out of the APPJ PM1502A is maybe a deeper, more three dimensional soundstage with some additional clarity in the mids. Of course, let's face it, part of what I'm looking for is also the fun of rolling different tubes through the amp. I guess I should also mention that I'm not interested in doing any surgery or replacing any of the innards - my experimentation will end at tubes swaps.
  
 I realize this is a fairly inexpensive amp and might not have the refinement of something higher on the food chain but it would be great to be able to fire it up and add a little more space to Steely Dan, Steven Wilson, or Miles Davis. 
  
 Thanks!


----------



## Maxx134

Even in Stock mode, it has abundant soundstage potential with so much tube rolling possibility. 
To me this is the nicest design because of being tube only, triode wired, and Japan output transformer for most headphone compatability. 




kryl0071 said:


> Very interesting. Let us know what you done.




For Cathode caps, 
I ordered some Elna silmic caps as they is best brand for quality and and also cheap price. 

I also will be adding a second cap in parallel to help these electrolyctic caps, as explained in the first page of Little Dot SuperMod thread, 
Quote:
*
Bypass : in order to help the Lytic cap in the areas it is weakest (treble, microdynamics, ...), we add in parallel an another cap of a different techno, smaller and faster.
After having tested various caps (Teflon, Polypro, PIO, Styroflex, ...) the best "musical" match was with some (multilayer metallized paper) PME271 used as "electromagnetic interference suppressor... *

 

For coupling cap: 
 I will pick a nice coupling cap.
 I like the PIO vitamin Q caps as best value for natural treble sound.. 
I don't like any plastic type film caps, as they can add artificial sweetness (like mundorf) to the very top end of their sound, and WIMA caps tend to be slightly too soft sounding unless you get the real huge performance type . 
There is a cap review link in the SuperMod thread mentioned above. 

So that's my plan, just waiting on the cathode Electrolytics costing maybe 3dollar, as I bought 3 in case I mess one up!, lol


----------



## a44100Hz

If anyone else in the States wants one of these, I have one for sale that's not in use; drop me a line. 

One thing to note about this amp is that the volume pot has a bit of a channel imbalance at low volumes (as do a lot of pots, unfortunately) so it wouldn't be suitable for low level listening to something like IEMs. But that's IMO and YMMV.


----------



## Maxx134

Upon Tube rolling different tube types, 
I have noticed differences usually noted with different bias changes. 
Most likely because the tubes are dependent upon the amp pre selected bias points. 

So, Although I did like the huge 6L6 type better than stock, 
And also the fat bottle New production KT66, 
I am finding that the amp seems to sound most natural with the 6V6 type, most notably these 6V6G Fivre (made in Italy, CV509 military spec) :



Link;
http://www.ebay.co.uk/itm/311574587793
Great price. 


Edit: I have not tried my 6Y6 type yet..

Edit 2:
So I am in agreement with the product description stating 6V6 type as replacement...


----------



## Kryl0071

Best result for my ears Sylvania Baldwin 12AX7 and NOS Russian 6Ф6С (6F6S) "Cobra".


----------



## Kryl0071




----------



## Maxx134

kryl0071 said:


>



Public thanks to member "Kryl0071" for helping me mod this beauty of a little amp.

This is a highly underrated beauty that I will put up against any amp once done upgrading it.
I have already tested it against my main amp and it only needed more bottom end punch and a bit more Soundstage.
The shockingly promising clue that this amp has potential,
Was both the resolution and the very quiet background.

On my amp, I see they quietly upgraded the PSU with two small caps where there was one in older designs.
Look:
Old:

Circled in red is the area of original design, along with a blue circuit board.

Now mine:

You see there are two caps now in same area, 
Along with slightly different green circuit board.

Those are the only noted changes as I do not have a schematic or know if I can get one.

So, to increase both low end authority and punch, I first will change the coupling cap yet again
Stock .1uf is dismal,
And I am currently using only .2uf which is not enough for low end response.
I was able to achieve much more clarity and musicality with the change of stock coupling cap.

So if I use a "boutique" cap, I should notably increase the soundstage.
It already has resolution from tube upgrades .
I am still almost done with tube rolling , just a few more tries.
I tried alot so far.

What should be noted as to why I decided to put my efforts into this little amp,
Is because of the usage of very very heavy quality output transformers being used.
I would say 95% of the total weight of this mini amp is due to the output transformers, 
Which , to me, are better than most top mid-grade amps.

So this little amp has huge potential if the upgradeling works out.
This amp has made a great and wise achievement to invest the money on output transformers, and eliminate the traditional PSU Transformer.

You don't see this in any other tube designs.
This is also how the new electrostatic amp , the " Sonoma Acoustics Model One Electrostatic Headphone System", 
achieves it's high voltage for the headphones, as well as portable tube amps boost voltage,

So it is a relatively new idea usage in the tube area.
With ALmost all major tube designs being much more traditional or even excessive with tube as rectifiers.

Anyways, moving on:
The Electrolytics I also upgraded, but was still not enough punch to them.
I believe due to the type of PSU being used, and the tube bias settings.

For this "switching" PSU to be effective, I am finding out what memeber "Kryl0071" already knows, and showed me,
That it is more reliant on the caps.

So we need to boost the cathode Electrolytics more.
It's already good at 470uf, but not jaw dropping good.

Once I am done I hope to achieve a quality close to my main heavily modded amp.

The question is to be able to achieve this without much expense.
This will rely on choice of coupling cap, as other cathode caps won't cost much..

I already have it at a level where it can either **
Edit: this comment is both subjective and debatable,
But in my opinion,
 it **can** match or surpass a crack or Torpedo or woo wa7 in terms of clarity, as they are all units I were familiar with or owned or borrowed.
Again, my subjective impression.

Other aspects of sound, such as dynamics or Soundstage will vary with tubes and caps upgrade.

I totally expect my own finished results to definitely do so (surpass), 
So it will be fun to compare as I love tube gear in general regardless of how good it is.

So it is surprising because I only wanted a small amp like a vali2 to burn my headphones in, 
So I won't burn my main amp,
 but I fell in love with this little amp.


Here is it now and next to my reference amp:
.

Update , I edited this post for clarification.


----------



## Maxx134

Here is how my amp currently is,
using only .2uf as coupling, and 470uf as cathode, and a .047 as a bypass on the Electrolytic:

This was initial mod test.
Super easy upgrade.

Once I found out it actually improved significantly, 
I decided to see if it could climb more.
I decided to give it the end game level boutique caps test.

So I should have it upgraded over weekend with some larger capacitance top level caps.
It will be interesting to see how good this baby can get.


----------



## Maxx134

OK, my mistake for being lazy:

I used two parallel caps in coupling cap position to boost the capacitance...
Big no-no.
The result was a thickness in the bass area which was a loss of focus in that specific area.
I mistakingly thought it was the driver tube choice.

AFTER I completed my coupling cap upgrade to a single HUGE copper foil cap,
I was quite surprised the driver tube now sounded MUCH more focused an clear.
I was quite shocked as I really thought it was the tube.


----------



## Maxx134

OK so I have finished upgrading my mini amp..

The result forced me to have to extend the bottom plate.

I had to go buy some longer metric screws and spacers for them, to extend the bottom about ALmost one inch.

The only reason was for the coupling cap.

I should have just used .48uf as recomended as the largest, as it not need more,
But instead I bought HUGE .68uf "Audyn True Copper" which were on sale almost same price.

So now I am using monster copper foil caps,
Arguably one of the best for the money as well.

I feel Audyn True Copper can achieve sonic quality on par with the other best copper foil caps.


----------



## Maxx134

Although the caps upgrades was a major improvement,
The system seems more dependent on matching driver tube with power tube.
Tube rolling is more noticable.


----------



## stolikat

I need to up my soldering skills so I can do this mod.


----------



## jekjek

I ordered my gemtune appj 1502

Another idea for the power tubes is EL33 with different heater current

Cheers


----------



## Maxx134 (Jul 22, 2018)

kryl0071 said:


> Best result for my ears Sylvania Baldwin 12AX7 and NOS Russian 6Ф6С (6F6S) "Cobra".



Thank you for suggestions as I ordered and will have the 6F6S"Cobra" coming in soon.
Great deal these Russian tubes!

Also,
I am finally satisfied with the outcome of my mini amp modding.

*Coupling cap*:
.68uf Audyn True Copper

*Cathode cap*:
1000uf Audio Note KAISEI Electrolytic Capacitor

* Bypass cap on the Electrolytic*:
.1uf Audyn True Copper

Now this baby is impressive!
Only Problem , like I said, was that I had to extend the bottom plate with long screws and spacers to make sure the pressure was in the chassis and not the board.

Will post pics soon.


So although I was excessive with my mod,
It seems the general consensus / recommended values are:


*Coupling cap*:
.47uf film (any preferred type)

*Cathode Electrolytic*:
1000uf Audio Note KAISEI

*Bypass cap on Electrolytic*:
.047uf-.1uf cap (film)

Cheers


----------



## Maxx134 (Jul 22, 2018)

OK here are some pics of my internal/external mod:

...

...

...

...

...

...


I can safely say I can place this baby next to any good quality amp and it will hold it's own in quality sound.
All areas of sound are now top notch.(detailing/depth/dimensionality/realism/micro&macro dynamics)

The only weakness was in blasting.
Like my 20ohm HEKV2, it did so, but did run out of gas at a earbleed levels of end game power.
I was still able to shake them good and with other cans it did have authoritive power.
I atribute this to the 1000uf cathode caps as suggested by member "Kryl0071".



impressive considering this amp is less than $200,
and the upgrade was around $135 in parts..

So for about $330 total plus some soldering you get upper mid-tier  level sound!


----------



## Maxx134

jekjek said:


> I ordered my gemtune appj 1502
> 
> Another idea for the power tubes is EL33 with different heater current
> 
> Cheers




What I noticed is that the tube interaction with the output transformers have effect as well as the bias setting.
So although we can place in various tubes, 
It is guess work unless you take these two parameters into consideration.

I will post soon on my various tube trials and most optimal suggestions for the power tubes..
Good news is I believe I found the m
Best tube type for our amp,
 from member "*Kryl0071*"...

So big thanks to him for his help, which made the amp climb to new heights.

For the driver tube, it does have more choices that do not affect power so I'd a better place to have preference.

I still believe an 9 pin to 8 pin adapter is my preferred choice of tube type for driver,
But I will give the 9 pins another shot.

I have boxes of different tubes to try over weekend.


I will post tube review soon.


----------



## jekjek

maxx134 said:


> OK here are some pics of my internal/external mod:
> 
> ...
> 
> ...


 
 Hi Max,
 Can you show us the soldering points you did on the other side of the board please?
 I am trying to do the same mod as you
 Below is the pictures of my board. Looks like i have version 1 board


----------



## Maxx134

Yes they are the same exact points posted in thread by others,
but I will post again:



I am trying to find the top​side pics..


----------



## Maxx134

Here is a close up of the Electrolytics and the film caps soldered on the leads.

For the square coupling cap replacement,
I used silver wire in the holes to bring wires to that area for big coupling caps..

Edit:
Go here for clear pics on the solder points on the topside / surface mount side of board:

https://www.aradiogurl.net/hhjournal/2016/06/01/gemtune-pa1502a-appj-headphone-tube-amp-mod/


----------



## jekjek

Below us my modified appj 1502
  
 I would like to say thank you to @Maxx134 for his support

  
 My modification is:
 - wima 0.47 uf 400v
 - panasonic fr 1500uf
 - solen 0.1 uf
  
 I have completed the modification but there is no sound on the right channel
 I will need to resolder it again tonight


----------



## Maxx134

Wow that is excellent work!
Now onto your "no sound" issue.

The board is double sided.
It is also easy to rip the trace ads: were the leads go into hole.

Although you should check the right side coupling cap first,
My guess is the right side electrolytic cap not have ground connection.

That is where my trace broke when I pulled out old one,
 and then it was essentially an open circuit.


So, on those holes that I pulled up the trace, I had to scrape the board to expose the copper trace.


----------



## jekjek

maxx134 said:


> Wow that is excellent work!
> Now onto your "no sound" issue.
> 
> The board is double sided.
> ...




Thanks Max
Its working now


I'm using EL33 with old Philips ECC83
Sounds awesome. Very smooth

EL33 is basically octal version of EL3N.


----------



## Maxx134

I never tried that ...
EL33 Hugh?
Ok now I wanna try!
Also caps need burn in..
Edit**
I just checked and EL33 is not as optimal as it will give lower output performance over 6v6 in this amp.

EL33 may still sound very good as those tube number are usually designated from Europe.


----------



## jekjek

maxx134 said:


> I never tried that ...
> EL33 Hugh?
> Ok now I wanna try!
> Also caps need burn in..
> ...




Agree about the lower output however people from the felix audio elise gang loves it

Let me try and compare the EL33 vs rca 6v6 this weekend


----------



## baronbeehive

maxx134 said:


> .........
> That is where my trace broke when I pulled out old one,
> and then it was essentially an open circuit.
> 
> ...


 
  
 He, he...... I've been there, tell me about it!
  
 I just wondered if you guys would be interested in the _*other*_ .....!!! APPJ ...... the Miniwatt, or APPJ PA0901A speaker amp. This amp is just so good I don't want anything else, but having already modded my LD I'm interested in pushing it to see how far it will go. I'm from the Little Dot Supermods thread along with Maxx134. I'm planning on doing the coupling and cathode caps mod to this amp also.
  
 I've had the little Miniwatt for 5 years or so and am pretty awestruck with it, I can say. I'm using it with only 87db speakers yet it sure rocks. I'm planning on adding the highly rated Jupiter copper foil, paper and wax caps, and the Audio Note Kaisei's that Maxx134 has used. My alternative plan if the Jupiters produce too much bass for my set up is to use Audyn True Copper caps with a lower capacitance than Maxx134 used because the amp as it is produces plenty of bass for me and the 0.47uF Jupiters might just be too much of a good thing! While increasing capacitance for headphone amps is the thing to do to get better bass I'm not sure about doing that for a speaker amp.
  
 Anyway if you are interested I will report back when I've done the mods.
  
 I didn't know about this sister amp until recently, great thread guys 
	

	
	
		
		

		
		
	


	




.
  
 Edit:
 Thanks to Maxx134 for the info on the mods.


----------



## jekjek

baronbeehive said:


> He, he...... I've been there, tell me about it!
> 
> I just wondered if you guys would be interested in the _*other*_ .....!!! APPJ ...... the Miniwatt, or APPJ PA0901A speaker amp. This amp is just so good I don't want anything else, but having already modded my LD I'm interested in pushing it to see how far it will go. I'm from the Little Dot Supermods thread along with Maxx134. I'm planning on doing the coupling and cathode caps mod to this amp also.
> 
> ...




Dig it. Show us what you have done


----------



## baronbeehive

OK, thanks. I'll let you know how the mods went when I've done them, I've got to order the parts first, the fun comes later!!
  
 Forgot to say my APPJ has EL84's for power tubes instead of your 6V6's, I have Amperex Bugle Boy type power tubes and Tungsol 5751 for the 12AX7.
  
 Edit:
 Parts on order.


----------



## Maxx134

Caps upgrade give increase in resolution (coupling cap) and power(cathode cap).

Frequency "extension" (lower freq, not an increase in amplitude) from cap size seems optimal at .047uf on coupling cap.
As for voltage rating, there is only about 60v across it (I only measured 55v),
So any voltage 250v or higher is fine.


Transients, bass punch, and power sustain is optimized with larger Cathode Electrolytic of 1000uf.
This is due to the "larger" cathode cap value causing the effect of holding the cathode voltage constant, which keeps it at optimal gain.

As for voltage, 25v or higher is fine here,
And the Audio Note Kasie caps are recommended first, 
Or also Panasonic or Elna silmic2. 

WARNING:
Do not confuse the cathode caps with the PSU caps Wich actually do need high voltage ratings.
It is suggested to not alter and not modify the PSU section.


The preset autobias settings of the circuit will still be optimal with either designed tube choice, or your preferred choice,
And the point is this will not change with the cap upgrades.

For the 1502A amp, I have tried most tube types available,
 and will post about them soon.
Cheers


----------



## baronbeehive

This is my PCB, very similar to yours, very neat and tidy inside:
  
     
  
 And these are the finished mods:
 1 - Coupling caps: Jupiter copper foil paper and wax caps, 0.47uF, 600V
 2 - Cathode caps: Audio Note Kaisei , 1000uF, 25V
  

  
  
 I'm also going to put in a new AMR Audio 90% Silver Alloy Fuse Tube 5x20mm (Slow Blow).
 Unfortunately I can't say anything about the sound due to an ear infection but if it's even slightly better then it will be pretty amazing.
 Also doing some cosmetic mods. Pics to follow....
  
 Had one  scary moment,  I plugged in the power cord without realising it had switched itself on, and there were no tubes in, I quickly switched off and no harm done 
	

	
	
		
		

		
		
	


	




.
  
 Edit: Looking  forward to your tubes post Maxx134!


----------



## jekjek

baronbeehive said:


> This is my PCB, very similar to yours, very neat and tidy inside:
> 
> 
> 
> ...


 
 Nice job in a very tiny case!


----------



## baronbeehive

jekjek said:


> Nice job in a very tiny case!


 
  
 Thanks! Fortunately the Jupiters are smaller than the Audyns by a lot. The caps would have fitted better if I had removed one of the posts but they just squeeze in atm. Also I didn't use bypass caps for the cathode caps because the Kaisei's are supposed to be that good anyway. I will try to look out for any missing treble when I've done the listening test.


----------



## Maxx134

baronbeehive said:


> jekjek said:
> 
> 
> > Nice job in a very tiny case!
> ...



I would imagine the whole top end (treble region) getting allot more natural with the copper foils, and more soundstage and air.

Those electrolyctics are good,
all great choices made.

The caps do need plenty of burn in time. 
I believe mine seemed to settle in after 90hrs.

This amp achieves really really top quality sound now,
yet I believe it is so small in size,
It looks hard to take seriously , lol


----------



## baronbeehive

These are only my initial impressions now because I've only had limited listening time due to my ear problem, but immediately the sense of realism is evident especially in voices, and the sound is full bodied and the textural details in the music appear to be very striking. I don't want to say too much before I've had the chance to have more listening time.....
  
 I really think though that this is a very worthwhile mod on an incredible value amp.


----------



## jekjek

baronbeehive said:


> These are only my initial impressions now because I've only had limited listening time due to my ear problem, but immediately the sense of realism is evident especially in voices, and the sound is full bodied and the textural details in the music appear to be very striking. I don't want to say too much before I've had the chance to have more listening time.....
> 
> I really think though that this is a very worthwhile mod on an incredible value amp.




I think the next upgrade is the output transformer.
Which will cost more than the amp itself....

On the other hand. My itchy hands is testing the appj with Philips 6L6G



I will report my findings


----------



## baronbeehive

jekjek said:


> I think the next upgrade is the output transformer.
> Which will cost more than the amp itself....
> 
> On the other hand. My itchy hands is testing the appj with Philips 6L6G
> ...


 
  
 Look forward to hearing them!
  
 I've already doubled the cost of the amp thanks to the Jupiter caps, but they're the best thing I could have done, the sound is headbangingly good now, everything's gone up a level and I've very happy. I know coupling caps are supposed to be a weak link in amp design but I don't know how they've done it but they appear to have actually increased the transparency by a large measure!
  
 Interested to hear your experiences with the transformers, I think that you might have a job finding better ones, they're already quite good I think, but good luck!


----------



## jekjek

baronbeehive said:


> Look forward to hearing them!
> 
> I've already doubled the cost of the amp thanks to the Jupiter caps, but they're the best thing I could have done, the sound is headbangingly good now, everything's gone up a level and I've very happy. I know coupling caps are supposed to be a weak link in amp design but I don't know how they've done it but they appear to have actually increased the transparency by a large measure!
> 
> ...



Report on the Philips 6L6G
Music presentation is very clear but too forward for my liking

To get the best output transformer meaning more money.
For myself the goal for me is to have fun with my tubes. So I won't be changing output transformer anytime soon unless i got it for free.


----------



## jekjek

Look at what the postman bring today
And i end up with EL3n adapter


12sn7 driving the EL3N
Its very tight in there


----------



## Maxx134

jekjek said:


> baronbeehive said:
> 
> 
> > Look forward to hearing them!
> ...



I would not think of transformers because these are quite good already, and are not the simple type.
They have many secondaries which I was not able to follow. The board trace is covered (as the transformer itself) with a super thick layer of glue covering half the insides of the covers...
So its not going anywhere. .
I am not sure what is the purpose of this transformer being so different than te other mini amp, and including many taps to it:



Also, 
The 6L6 is an excellent tube,
But in this aml, it was not optimal for me either.
This is due to the amp bias points and plate voltage.





jekjek said:


> Look at what the postman bring today
> And i end up with EL3n adapter
> 
> 
> ...



I tried the 6k6, nice and seemed good overall,
but not as strong or good as 6v6 which "was" my top choice.

I just aquired the Russian 6Ф6С / 6F6C Cobra..
They are a bit more powerful so are another top choice as they give the most powerful output while also giving clarity.
It doesnt hurt that they are such a great low cost value..

I have a "42" tube coming with adapters. .


----------



## baronbeehive

maxx134 said:


> ......
> 
> 
> Also,
> ...


 
  
 So the bias presets allow the amp to autobias to the tube type?
  
 You mention the NOS National Union 6L6, and the Valvo e180cc pinch waist, are these still your favourites? What about the 6V6G Fivre?
  
 I think any driver tube which is very lively like the Valvo, for example would be a no no for my speaker amp. The reason being the punch and sheer visceral power of the lowly 3.5 amps is shocking, I'm finding now that a sudden bass drum can almost crash me off my chair if I'm not expecting it! Clearly the Kaisei caps you recommend are providing more than enough power......... and also there's my neighbours to consider......
  
 Also I'm not finding any lack of treble resolution without the bypass caps. The balance of the frequency spectrum is shifted from my headphone amp though as there's much more emphasis on bass with this amp.
  
 Although I am happy with my tubes, would I be able to try the same tubes with my EL84 amp as you?


----------



## jekjek

baronbeehive said:


> So the bias presets allow the amp to autobias to the tube type?
> 
> You mention the NOS National Union 6L6, and the Valvo e180cc pinch waist, are these still your favourites? What about the 6V6G Fivre?
> 
> ...




If you like dynamic bass, you can try GE 12sn7 short bottle
The bass is awesome


----------



## baronbeehive

Hey... this cute little amp just got even cuter ....
 I've shamelessly stolen the front bar idea from Maxx134, It needed some bling, the amp's gotta have that front bar! I think it now rivals his amp, (but he has better looking tubes).


----------



## baronbeehive

jekjek said:


> If you like dynamic bass, you can try GE 12sn7 short bottle
> The bass is awesome


 
  
 No thanks I've heard about the bass on those! I've got all the bass I can handle. You using the 12SN7's in place of the 12AX7? I had a few TungSol 12SN7's which I used on my other amp which I've sold now thinking I wouldn't need them again! I really liked them and use the 6 volt version on my other amp now.


----------



## jekjek

baronbeehive said:


> No thanks I've heard about the bass on those! I've got all the bass I can handle. You using the 12SN7's in place of the 12AX7? I had a few TungSol 12SN7's which I used on my other amp which I've sold now thinking I wouldn't need them again! I really liked them and use the 6 volt version on my other amp now.




I'm using tungsol 12sn7 now and hv 1 spare
Its definitely sweeter than GE 12SN7


----------



## baronbeehive

jekjek said:


> I'm using tungsol 12sn7 now and hv 1 spare
> Its definitely sweeter than GE 12SN7


 
  
 Yes, they are very liquid sounding, I imagine they will have a similar sound to the TS 5751 I'm using now. I may PM you to find out how much you want for it, but really ATM after a house move I don't have a lot of spare cash so it might have to wait. Then, sometime, I just have to find some similar, sized, or coke bottle shaped, power tubes to replace my Amperex EL84's, which I'm reluctant to do because I really like them.


----------



## jekjek

baronbeehive said:


> Yes, they are very liquid sounding, I imagine they will have a similar sound to the TS 5751 I'm using now. I may PM you to find out how much you want for it, but really ATM after a house move I don't have a lot of spare cash so it might have to wait. Then, sometime, I just have to find some similar, sized, or coke bottle shaped, power tubes to replace my Amperex EL84's, which I'm reluctant to do because I really like them.




Try valvo EL84
They sound good!


----------



## TheBIGKill1998

Hello,
  
 i am planing on getting this amp soon. I am not very good at soldering and i saw that some of you guys made some upgrades on the caps.
  
 The tubes will be of course rolled later! 
 I currently have a nobsound ns08e amp and i plan to buy this one as a sort of upgrade.
  
 So my question would be now.... is it worth getting this amp as a "upgrade" for my current one for what it costs (175 euro on amazon)? 
  
 thank you!


----------



## baronbeehive

thebigkill1998 said:


> Hello,
> 
> i am planing on getting this amp soon. I am not very good at soldering and i saw that some of you guys made some upgrades on the caps.
> 
> ...


 

 I see the nobsound ns080e is entry level, for those curious about the tube sound, though I don't have any experience of it. Regardless of that I can say that far from being simply an upgrade, the APPJ could be an amp you keep with you because it's so good you will never need anything else. It has several features that push it up to the top level, others on this thread will be able to tell you about. I won't go on because I have the speaker version of the amp but right from the start I was impressed with the amp. The caps upgrade just made it TOTL, and is a very easy mod that someone could do for you if you don't want to.
  
 For the money you can't go wrong. Hope that helps!
  
 Edit: My speaker amp has had good reviews from 6Moons amongst others!


----------



## TheBIGKill1998

Ah alright, thank you for your answer! 
  
 What you said about this amp sounds pretty darn good so far. So it looks like this amp is a very good purchase then! 
 And its pretty good if those upgrades are relatively easy. all i would need to do is searching for someone who can implement them for me. 
  
 How expensive are those capacitor upgrades if i may ask? 
  
 And i really would like to know more about those "features" which you stated this amp has. 
 So, can anyone tell me more about them?


----------



## baronbeehive

thebigkill1998 said:


> Ah alright, thank you for your answer!
> 
> What you said about this amp sounds pretty darn good so far. So it looks like this amp is a very good purchase then!
> And its pretty good if those upgrades are relatively easy. all i would need to do is searching for someone who can implement them for me.
> ...


 

 I'm not an expert on this so if you want to know more ask some of the others but for example it has an advanced Switch Mode PSU which means quiet background, advanced DC tube heaters, reliable surface mount parts, top quality transformers. In sum, the hybrid design of the amp means that you get the benefit of tube amplification with some solid state features as well which means that you get all the realism and holography of tubes and also good tight bass and sharp transients etc.
  
 For the upgrades it depends on what you want to spend:  the Audio Note Kaisei 1000uF 25v electrolytic cathode caps are quite cheap at £13.40 for 2, the Jupiter copper foil paper and wax .47uF 600vdc coupling caps are £135.24 for 2, the Audyn True Copper .22uFcoupling caps are a lot cheaper, £32.74 for 2, or .47uF are £50 for 2. The disadvantage of the Audyns is their size, you would have to extend the bottom of the case to fit these, otherwise they are good. You will need 2 coupling caps and for best results also 2 cathode caps.


----------



## TheBIGKill1998

Ah alright! Thanks a lot for your answer!
  
 The benefits you named are really damm good! 
  
  
 But is the solid state part of the amp directly a part of the amplification like in the nobsound (there are opamp chips in it) or is it just for the surrounding, other electronic functions of the amp? 
  
 I would go with the Audio Note Kaisei 1000uF 25v electrolytic cathode caps then for certain. 
  
 Hmmm, but the coupling caps seem to be quite pricey. 
 Is there another good alternative for the coupling caps which arent that pricey and also not very big?


----------



## baronbeehive

thebigkill1998 said:


> Ah alright! Thanks a lot for your answer!
> 
> The benefits you named are really damm good!
> 
> ...


 
  
 I'm pretty certain that all the amplification is done by the tubes.
  
 Re: the caps, I can only suggest you look at reviews here: http://www.humblehomemadehifi.com/Cap.html and check out the ones that look good and check their dimensions on the datasheets first. If they are the same size as the Jupiter caps, 21mm x 52mm, I mentioned then they should fit ok.


----------



## TheBIGKill1998

Alright! again, thanks a lot! 
 Good to hear that the amplification is all done by the tubes.
  
 i will look at that website as soon as i order the amp. 
 I really hope to find some good and not too expensice caps there.
  
  
 for now i really wanna wait for other opinions on this amp before i buy it.


----------



## baronbeehive

Great,  I think this thread is still alive.... just!
  
 Don't forget the sound quality depends enormously on the coupling caps so it's not really worth getting the cheapo ones. Personally I would still go for the Audyns for the realism factor, they are not expensive and it wouldn't be too difficult to extend the case.
  
 Good luck!


----------



## TheBIGKill1998

well, i will look at how i can expand the case as soon as i get it, if i am going to get it of course. 
  
 what's the difference between the .47uF and the .22uF audyns ones, by the way? 
 (i know that the uF stands for the capacity of them. Im asking for the difference sound wise)


----------



## baronbeehive

thebigkill1998 said:


> well, i will look at how i can expand the case as soon as i get it, if i am going to get it of course.
> 
> what's the difference between the .47uF and the .22uF audyns ones, by the way?
> (i know that the uF stands for the capacity of them. Im asking for the difference sound wise)


 
  
 The higher the capacitance up to a point, about 1uF the better the bass response, I would expect that .22uF would be the minimum likely to improve bass frequencies. However the stock cap is a miniscule .12uF I believe on the headphone amp so anything would be better!


----------



## jekjek

I spent usd 15 for my capacitor mod and it still sound awesome. Exactly same mod but easy to find capacitor like wima and solen


----------



## TheBIGKill1998

I know you all recommend the capacitor upgrade.... but does it sound bad without it?


----------



## Maxx134

Hey guys I been away. 

For main coupling caps, I only recommend the Jupiter copper(best) or the mundorf silver/gold, simply because they will fit and are well regarded. 
The Audyn True copper is just too big, but dam good. 

Get the cathode caps already mentioned. 

For tube rolling, I tried so many, I will make a list soon. 

To get to the end result, the 
6v6 tube may be most recommended overall, 
But the best tube sonically matched with those output transformers it has, 
Are the 6F6 tube! 

Most power and clarity with that tube for the APPJ PA1502A.. 
The "42" tube with adapters is just as good if not most optimal. 

So.. 
My tube rolling has come to an end. 

Best tubes for this model:
Power tubes = 6F6 / 42 / Russian 6Ф6С / 6F6C Cobra..

Driver tube:
12SL7GT


----------



## Maxx134

thebigkill1998 said:


> I know you all recommend the capacitor upgrade.... but does it sound bad without it?



No it sounds quite nice stock. 
Coupling cap replacement improves everything. 
Cathode cap replacement improves dynamics and bass sustain. 

End result is shockingly good. 
Think of a tube Jotunheim with the added soundstage holography that was missing.


----------



## benjisun

Thanks for all the usefull informations on this topic,
  
 Here is my board initial mods, I am with a V2 board (green with two caps instead of one on the alim circuit) 
  

  
 Here is mine, Only replaced the Coupling cap by Audyn Qs6 for now and the sound already improved with the tubes I use. Less V shaped than with stock. 
  

 Here compared to the original one. Fitting the Audyn is not so easy as they are bigger. 
  


  
  
 Here my amp, I use Tungsol 6L6G and a JJ12AX7 that will be replaced by JJ gold long plate soon.


----------



## baronbeehive

benjisun said:


> Thanks for all the usefull informations on this topic,
> 
> .............
> 
> Here my amp, I use Tungsol 6L6G and a JJ12AX7 that will be replaced by JJ gold long plate soon.


 
  
 I've tried the JJ ECC83S in my speaker APPJ, it is probably the only new issue tube I would use, powerful well defined bass, good details and soundstage, and quite nice tone for new issue but lacking the warmth for me.


----------



## baronbeehive

maxx134 said:


> ...................
> 
> So..
> My tube rolling has come to an end.
> ...


 
  
 Good work!
  
 What is the 42 tube exactly?
  
 You used adapters for your tube rolling, but were they also converters, as in voltage converters. I have lots of 6sl7's but no 12sl7's.
  
 Could I use the 6F6's as a replacement for the EL84's my amp uses? I just love the way it looks with the big tubes lol!
  
 BTW, how did you get your volume knob off?


----------



## Maxx134

baronbeehive said:


> maxx134 said:
> 
> 
> > ...................
> ...




VOLTAGE ADAPTERS ARE NOT RECOMMENDED!!!
DO NOT USE ADAPTER WHICH DROP 12V TO 6V BECAUSE THEY ARE ALL CHEAPLY MADE IN CHINA USING LOW WATT RESISTOR WICH WILL BURN. 
THEY HAVE BEEN KNOWN TO FAIL AND DESTROY YOUR AMP. 

I myself tried one (for driver tube on this amp) , 
 and although I loved using my 6v tubes, the adapter did get very hot very fast, 
So after 4-5min use it was too hot Touch. 
BOTTOM LINE IS DON'T USE THEM... 

ALSO, 
For tube equivalent EL84, check here :
http://www.radiomuseum.org/tubes/tube_el34.html


----------



## TheBIGKill1998

Thank you to everyone who answered my questions on this thread! 
  
  
 but i think i should get proper headphones before i get this amp...
 also all the tube rolling and the mods would kinda blow my current budget.


----------



## benjisun

baronbeehive said:


> BTW, how did you get your volume knob off?


 
  
 Also interested, I tried to pull mine off but dont want to break the Knob


----------



## baronbeehive

maxx134 said:


> VOLTAGE ADAPTERS ARE NOT RECOMMENDED!!!
> DO NOT USE ADAPTER WHICH DROP 12V TO 6V BECAUSE THEY ARE ALL CHEAPLY MADE IN CHINA USING LOW WATT RESISTOR WICH WILL BURN.
> THEY HAVE BEEN KNOWN TO FAIL AND DESTROY YOUR AMP.
> 
> ...


 
  
 OK, thanks. I have have 6v to 12v adapters made by Glenn but not the other way around! I'll search out some 12SL7's.
  


thebigkill1998 said:


> Thank you to everyone who answered my questions on this thread!
> 
> 
> but i think i should get proper headphones before i get this amp...
> also all the tube rolling and the mods would kinda blow my current budget.


 
  
 No worries, but just remember, this amp is an absolute bargain in stock form!


----------



## TheBIGKill1998

I will remember, and as soon as i decide to upgrade my headphone amp, this one will be my choice!


----------



## CZ4A

It's cool to see how far this thread has come since I last posted in here. I like seeing what folks are doing with recaps. I've still yet to install the WIMA coupling caps I ordered months ago!

Anyways, I'm still using the APPJ as my home headphone amp. I have done a little more rolling too - right now I'm burning in a Raytheon 2C52 preamp tube. Power tubes are Mullard EL33s. I also have a FDD20 and adapter on the way.


----------



## baronbeehive

CZ4A said:


> It's cool to see how far this thread has come since I last posted in here. I like seeing what folks are doing with recaps. I've still yet to install the WIMA coupling caps I ordered months ago!
> 
> Anyways, I'm still using the APPJ as my home headphone amp. I have done a little more rolling too - right now I'm burning in a Raytheon 2C52 preamp tube. Power tubes are Mullard EL33s. I also have a FDD20 and adapter on the way.



Well, what are you waiting for lol!
This amp is that good it's a keeper for me now. It's proven by the fact that it's on a par with my headphone amp which has been heavily modded, and if a speaker amp can do that then I know it must be good. Frankly I haven't heard anything better.
Re: the tubes, I've decided to stick with my Amperex bugle boy EL84's and TS 5751. The EL84's are all small tubes, not the larger coke bottle type which I would have tried, and the TS's sound similar to the TS12SN7's that I had a while back so I see no reason to change now.
I shouldn't really be posting on this thread but I feel it's an APPJ so why not, the Miniwatt threads are dead now but this one is still going.....


----------



## wendyKL

Hi what is the recommended load impedance on this? I have 18 Ohm headphones (IEM) would they be okay?


----------



## CZ4A

baronbeehive said:


> Well, what are you waiting for lol!



I wish I hadn't waited! I installed the WIMA coupling caps over the weekend - yowza, what an improvement all around! 



wendyKL said:


> Hi what is the recommended load impedance on this? I have 18 Ohm headphones (IEM) would they be okay?



- Output Impedance: 8 to 600 Ohms


----------



## wendyKL

CZ4A said:


> I wish I hadn't waited! I installed the WIMA coupling caps over the weekend - yowza, what an improvement all around!
> 
> 
> 
> - Output Impedance: 8 to 600 Ohms


Thank you, I'll be purchasing one. Black or Silver? hmmm.


----------



## baronbeehive

CZ4A said:


> I wish I hadn't waited! I installed the WIMA coupling caps over the weekend - yowza, what an improvement all around!
> 
> .............
> 
> ...


----------



## jekjek

Hi Guys,

I tried RCA 1633 also known as 25SN7 on the Gemtune amp with 12SN7 adapter and I can tell you that the amp still works properly with a pair of EL33 power tubes!

Imagine the possibility of tube rolling with this cute amp


----------



## Maxx134 (May 3, 2017)

jekjek said:


> Hi Guys,
> 
> I tried RCA 1633 also known as 25SN7 on the Gemtune amp with 12SN7 adapter and I can tell you that the amp still works properly with a pair of EL33 power tubes!
> 
> Imagine the possibility of tube rolling with this cute amp



Wow,  that tube still work when it rated to need double the heater voltage at 25v.!
That 1633 tube is supposed to be a 6sn7 type with just a higher voltage heater:
http://www.radiomuseum.org/tubes/tube_1633.html

Sometimes tube numbers just don't make sense.
It should have been labeled a "25sn7" of the was such a thing..
Probably already used number at the time lol


----------



## CZ4A (May 3, 2017)

baronbeehive said:


> Ha, ha, goodwork!
> 
> What capacitance wima's did you use? They should be excellent.
> 
> I know the Jupiter caps I put In are expensive but the level of realism you get with them is incredible. I only used them because I had one left over from my previous mods so I only had to get one more. Because of them I now have a band playing in my own living room..... btw how do you get rid of them.... they can get a bit rowdy lol .



I used 0.47uf WIMA MKP4 caps per Kryl0071's suggestion. I have some Jantzen Z-Superior 0.1uf caps on hand for my Eico HF81 project. I may try some cap rolling to see if its the caps or the capacitance that have the largest effect on the SQ.

On a side note, I'm glad the designers used actual Rubycon and Nichicon caps in this amp, although they aren't audio-rated.



Maxx134 said:


> Wow,  that tube still work when it rated to need double the heater voltage at 25v.!
> That 1633 tube is supposed to be a 6sn7 type with just a higher voltage heater:
> http://www.radiomuseum.org/tubes/tube_1633.html
> 
> ...



Those four-number tube codes (1633, 7308, 8416, etc.) often mean the tube is industrial-rated. Not always though - like you said the tube designations don't make sense sometimes! However, just because the 1633 works in the APPJ doesn't mean it's working properly. When you run a tube's filaments (heaters) below their rated voltage, it reduces the tube's life by causing cathode poisoning.



> https://www.w8ji.com/vacuum_tubes_and_vaccum_tube_failures.htm
> We must *NEVER *operate  the 3CX1500A7/ 8877, 3CX800A7, or other oxide-cathode tubes at reduced heater voltage! This would allow the cathode's protective electron cloud to be depleted, and nothing would prevent positive ions from striking and poisoning the cathode.



Tube heaters have a operational tolerance of ±7%-±10% (depending on manufacturer suggestions). The APPJ's preamp section supplies 12.6V for the heater, so you're running the 1633 at 50% lower than what is is rated for. It probably won't last too long.


----------



## jekjek

CZ4A said:


> I used 0.47uf WIMA MKP4 caps per Kryl0071's suggestion. I have some Jantzen Z-Superior 0.1uf caps on hand for my Eico HF81 project. I may try some cap rolling to see if its the caps or the capacitance that have the largest effect on the SQ.
> 
> On a side note, I'm glad the designers used actual Rubycon and Nichicon caps in this amp, although they aren't audio-rated.
> 
> ...



My bad. Sorry
I'm now using Raytheon 6414 as driver with a pair of EL3N
Result is good!


----------



## CZ4A

jekjek said:


> My bad. Sorry
> I'm now using Raytheon 6414 as driver with a pair of EL3N
> Result is good!



No need to apologize, it's your amp. I just wanted to warn you that the 1633's lifespan will be drastically reduced in the APPJ. If it was cheap enough and sounds good enough to you, use it.


----------



## Pratt99 (May 8, 2017)

Heads up. This amp is now available at Massdrop.(3 Days Left)
https://www.massdrop.com/buy/appj-1502a-tube-headphone-amplifier


----------



## Minbeo

Just want to ask how good this amp with HD800, how is it compared to Schiit Valhalla 2 or Ember???
Thanks alot.


----------



## benjisun

It sounds very good with my HD800. I would like the soundstage even wider but regarding tonality and details everything is ok. 

However my amp have some mods : tube replaced : JJ 12A7x and Tungsol 6l6g + Capacitors replaced (audyn 0.47 mkp and 1000 uf electrolytic mundorf cap. 

I think the 1000 uf electrolytic as mentionned earlier in the thread doesnt work for me: Imho it somehow bring more control but make the amp loose some dynamic. 
I'm thinking to change again to a value close to original cap (220uf) Maybe 330 or something just a little bit higher than original.


----------



## pvico (May 11, 2017)

For those interested, here is the schematic of the amplifier.
https://www.dropbox.com/s/ggm7a0la2era3n3/PA1502A APPJ Schematic.png?dl=0
Here is the LtSpice simulation package:
https://www.dropbox.com/s/rk5oukakn2bzwzg/PA1502A APPJ.zip?dl=0
Note:

I did not dig into the switched power supply and only the left amplifier section is included
I could not measure the value of capacitor E05, I just set it to 100nF. For E03, I measured 20uF with my LCR meter but this is affected by C09 through R27 and E03 is certainly much smaller than that. Anyway, it's just there to prevent Q2/IC3 from oscillating.
I did not find any data for the "Japan Z11-EI48*24" output transformer, I measured the serial resistance of both loops and set reasonable values for the inductances and turn ratio

I used 80 ohm for the headphone impedance (I use a Beyerdynamic DT770 PRO 80 ohm headset)
Only the high impedance switch position is simulated. Setting the switch to "L" connects the output to an intermediate tap on the output transformer
In the simulation, I used a 12AX7 model for the 6N4, a 6V6GT model for the 6P6P and  a BUZ90 model for the 4N60 MOSFET
_Whatever power tube you use, its quiescent current is set to 25mA by the combination of Q2/IC3/R29/R30
_
EDIT: I measured HT (179V), the heater voltage (11.7V, a bit low), the cathode voltage (9V) and the output transformer inductances. The schematic and LtSpice packages have been updated accordingly


----------



## Maxx134 (May 10, 2017)

Pratt99 said:


> Heads up. This amp is now available at Massdrop.(3 Days Left)
> https://www.massdrop.com/buy/appj-1502a-tube-headphone-amplifier


Wow dam thats a killer pricetag!






Minbeo said:


> Just want to ask how good this amp with HD800, how is it compared to Schiit Valhalla 2 or Ember???
> Thanks alot.


Ember is more bassy compared to the APPJ anemic stock unit.
Changing output  tubes to 6V6 and 6F6 solve that.
Upgrading caps gives massive upgrade in resolving nature to  trounce most other  amps.
Cannot say about Valhalla2.



benjisun said:


> Imho it somehow bring more control but make the amp loose some dynamic


Check the voltage rating of those caps.
I paralleled mine with an "Audyn" cap of smaller capacitance,  but higher voltage to not have any transient problem. 






pvico said:


> BUZ90 model for the 4N60 MOSFE



Sk the BUX90 is better spec than the 4N60?
If so,  I would assume better current capability?

Wow,  how did you get the schematic thats great!
I could not even find  link to the designer,  much less any info...
This is great info...


----------



## pvico (May 10, 2017)

_Sk the BUX90 is better spec than the 4N60?
If so,  I would assume better current capability?

Wow,  how did you get the schematic thats great!
I could not even find  link to the designer,  much less any info...
This is great info..._


No, but 4N60 is a chinese MOSFET for which no SPICE model could be found (but there is a datasheet somewhere). BUZ90 is close enough. Any MOSFET with similar ratings would fit the job. It has no impact on sound. The only important fact is that the quiescent current is fixed at 25mA.

As for the schematic, I used my iPhone camera, my USB microscope and my continuity tester...


----------



## pvico (May 11, 2017)

I must say that I was surprised to see that the cathode capacitor was rated 200V. I just received my new capacitors: Mundorf .47uF EVO silver gold oil for the coupling capacitor and Nichicon 1000uF 50V for the power tube cathode capacitor. I measured the voltage at the power tube cathode at 9V. So the 50V electrolytic should be fine, but why did they put a 200V capacitor there?


----------



## baronbeehive

benjisun said:


> It sounds very good with my HD800. I would like the soundstage even wider but regarding tonality and details everything is ok.
> 
> However my amp have some mods : tube replaced : JJ 12A7x and Tungsol 6l6g + Capacitors replaced (audyn 0.47 mkp and 1000 uf electrolytic mundorf cap.
> 
> ...



I'm using Kaisei 1000uF, 25v caps and for me the dynamics have improved enormously. The only thing concerning me was whether I have lost any higher frequency response due to not using bypass caps but I don't think I have and I won't be able to check properly until I can compare it with my headphone amp which is currently out of order.


----------



## Maxx134 (Jan 6, 2019)

pvico said:


> but why did they put a 200V capacitor there?


I have found and realized that manufacturers try to get away with whatever they have available to fit the  job.
Most likely either the shipment of that spec cap was cheaper,  or they are using cap for more than one location,  so it work out cheaper for ordering parts if yoh can get away with whatever you already have...




baronbeehive said:


> The only thing concerning me was whether I have lost any higher frequency response due to not using bypass caps but I don't think I have and I won't be able to check properly until I can compare it with my headphone amp which is currently out of order.


The increase in Cathode cap is to stabilize that voltage drop for bass sustain and bass punch,
Which is optimized with larger Cathode Electrolytic value of 1000uf.

This is due to the "larger" cathode cap value causing the effect of holding the cathode voltage constant, in relation to current demands,
So the tube  is kept at optimal gain.


Also,  at such large capacitance of  1000uf,  it should compensate for any performance or noise issues of  the combo of Q2&IC3 wich,  as "pvico" noted, are china parts which set  the tube bias at 25ma.


Most good electrolytic caps perform similarly,
 but the one we used is the "Audio Note KAISEI",
Which is supposed to be the best as it closest to the "blackgate" caps,
 which were highly regarded but not made anymore.
So Audio Note Kasie caps are recommended first, then Panasonic or Elna silmic2.


Anyways,  adding the second paralleled cathode cap(bypass) is for:
Quoted from member "Ridge78" :

*"Bypass : in order to help the Lytic cap in the areas it is weakest (treble, microdynamics, ...), we add in parallel an another cap of a different techno, smaller and faster."*

Since the KAISEI caps are already good enough,
my reason for adding bypass was to offset any tonality changes of the Cathode cap (KAISEI, have a slight darker tonality) compared to the coupling cap.

So my coupling cap and bypass cap are same exact brand &  model.
But just using the Audio Note KAISEI is just fine as it is "supposed"  to be the best..



I editing this post a year later because I have tried various caps since in different amps and in these types of circuits where there's a cathode cap, it will play a factor to the sound, and Kaisei caps in tbis situation will provide a darker richer tonality, while a Nichion KZ will be more neutral, and I prefer them over any Silmic2.

Remember the caps are in a situation to affect tonality *only* because they are in a position of being a "cathode cap".


----------



## baronbeehive

.............

The increase in Cathode cap is to stabilize that voltage drop for bass sustain and bass punch,
Which is optimized with larger Cathode Electrolytic value of 1000uf.

This is due to the "larger" cathode cap value causing the effect of holding the cathode voltage constant, in relation to current demands,
So the tube  is kept at optimal gain.

...........



.........

Yes, and that is what I have found, the gain is now very strong, it almost seems higher, but I realise it must be more stable, and recovery from transient peaks and troughs is at a very high level now. As you say the transients are very sharp now and this is what is so shocking, as I said it knocks me off my chair. The volume doesn't have to be high but these leading edges are now very prominent, and they have so much more textural detail, so I have no doubt that the cathode caps are doing their job. It all goes to add realism to the music and I'm pretty sure that applies to the high frequencies as well.


----------



## pvico (May 11, 2017)

Additional considerations, as a reply to some private messages:

R35 sets the feedback level and E05 increases the feedback at higher frequencies. I have no idea of the value of E05, .1uF is just an arbitrary value used to run the simulation.
Removing E05 would reduce the feedback at higher frequencies and increase the treble output. It would modify the phase shift of the feedback and this could cause some stability issues (oscillations).

As there is no audio signal through them, I don't think that IC3 & Q2 contribute significantly to the noise of the amp.

If you want to increase the bias current, you can add a resistor in parallel to R29/R30. Let's say you want to increase the bias current to 50mA, IC3 controls Q2 current to have 2.5V at its ref input, so it needs 50 ohm between ref input and GND. You need a 100 ohm resistor in parallel to R29/R30.

The 4N60 is rated at 4A & 106W, well above the default parameters of the amp. Out of the box, Q2 dissipates about 240mW according to the LtSpice simulation.

Running the simulation with a 6L6 instead of the 6V6 and with 100 ohm in parallel with R29/R30, the power dissipation of Q2 is now 450mW. You should probably put it on a heatsink.

Another factor may be the power limitation of the switching power supply. Out of the box, it provides 16W:

Heaters (the power tubes heaters are connected in series): 450mA + 150mA at 11.7V = 7W
HT: 2 x 25mA + 2 x 0.5mA at 179V = 9.1W
According to other users of this forum, it can accept tubes requiring 0.9A of heater current. Heater power is then 12.3W (11.7 x 1050mA) for a total power of 21.4W.

Increasing the bias current is most likely wanted when using bigger tubes like 6L6's. Increasing the bias current to 50 mA will increase the HT power to:
(2 x 50mA + 2 x 0.5mA) x 179V = 18.1W
For a total of 12.3 + 18.1 = 30.4W
This probably exceeds the power supply capability

EDIT: the power calculations have been updated with the measured voltages


----------



## Maxx134 (May 10, 2017)

Yeah,
I am very tempted to increase PSU capacitance (by C07&C08), 
 but do not know what is the capability of the PSU to handle increased initial surge current from such increased capacitance.
Oh well..


----------



## pvico

Maxx134 said:


> Yeah,
> I am very tempted to increase PSU capacitance (by C07&C08),
> but do not know what is the capability of the PSU to handle increased initial surge current from such increased capacitance.
> Oh well..


There is not much space to put bigger capacitors there. Moreover, my schematic is incomplete on the power supply side. There is another 4N60 MOSFET between those 2 caps adding either some kind of regulation or just an enable/disable function. I don't know what drives the gate of that MOSFET


----------



## pvico (May 11, 2017)

pvico said:


> There is not much space to put bigger capacitors there. Moreover, my schematic is incomplete on the power supply side. There is another 4N60 MOSFET between those 2 caps adding either some kind of regulation or just an enable/disable function. I don't know what drives the gate of that MOSFET


And there is a signal from the 12.6V (11.7V measured) through an optocoupler (IC2) back to the switching controller IC.

EDIT: on power up, HT rises to 250V and within seconds drops to 179V, probably after the tubes have heated and conduction takes place.


----------



## CZ4A

Maxx134 said:


> The increase in Cathode cap is to stabilize that voltage drop for bass sustain and bass punch,
> Which is optimized with larger Cathode Electrolytic value of 1000uf.
> 
> This is due to the "larger" cathode cap value causing the effect of holding the cathode voltage constant, in relation to current demands,
> ...



Interesting, that probably explains why I didn't hear any difference when I replaced the stock Nichicon cathode caps with Elna Silmics of the same capacitance (after I replaced the coupling caps w/ WIMA 0.47uf caps).

@pvico Awesome to see all of the investigation and schematics you have made of this amp! Quick question, what does "HT" stand for?


----------



## pvico

CZ4A said:


> Quick question, what does "HT" stand for?


HT is commonly used to designate a DC high voltage supply. You sometimes see B+ as well


----------



## CZ4A

pvico said:


> HT is commonly used to designate a DC high voltage supply. You sometimes see B+ as well



Ah, thanks. I'm familiar with B+ but haven't seen HT used to mean the same thing before.


----------



## jekjek

I have one thing to add
The amp sounds finer with 12ax7 tubes 
When i use 12sn7, i lost some small background details


----------



## Ctritical Bill (May 11, 2017)

Thanks pvico for the schematic.
I measured the B+ and it was 185v not 210v. Also, the heater voltage was 11.9v so I don't know if that affects your calculation of the bias current.


----------



## pvico (May 11, 2017)

Ctritical Bill said:


> I measured the B+ and it was 185v not 210v. I don't know if that affects your calculation of the bias current.


Yes, I just measured HT (B+) at 179V and the heater voltage at 11.7V (with the original tubes). I have updated the schematic accordingly. Here (Belgium), the mains voltage is 230V. If you're in the UK, it's more likely 240V which can explain the difference.


> I don't know if that affects your calculation of the bias current.


 No, the bias current is set by R29, R30 and IC3 which has a fixed 2.5V reference. So, the bias current is independent of HT.
Look at it this way: IC3 will do whatever it can on the gate of Q2 so that its ref input is at 2.5V. R29 and R30 in parallel have a value of 100 ohm. 2.5V / 100 ohm = 25mA


----------



## Maxx134 (May 11, 2017)

This is all excellent info,  thanks pvico.
 As for the bias,  this is important to know so we can pick optimal tube for that bias point..

Anyways,  from my testing,  the 6V6 were the most optimal,
Until I found out about the 6F6...

*Its output is roughly similar to that of the more well-known type 6V6, 
but it is considerably more sensitive(!), 
So it is even better at micro detailing from my own observations. 
*
Also,  the "42" tube with adapters was also a close choice for best tube,
But for now,  the *best tube choice  I like are the 6F6, specifically the  Russian  6Ф6С / 6F6C Cobra... 
Thanks to member "Kryl007" for that recommendation. 
*
Before the Russian tubes came in,
My best choice I was using was the Tung-Sol 6F6.
Tung-sol had great juicy overall sound, 
But the treble detailing of the Russian tubes pushed it into the lead and made my amp more resolving so it overcome any losses anywhere else,
Like the output transformers, as we know all transformers have some loss and that's why the good ones are expensive.

So far I am really almost dumbfounded how good this little amp is sounding ..


----------



## pvico (May 11, 2017)

pvico said:


> Look at it this way: IC3 will do whatever it can on the gate of Q2 so that its ref input is at 2.5V. R29 and R30 in parallel have a value of 100 ohm. 2.5V / 100 ohm = 25mA


Q2 with the help of IC3 and R29/R30 is a _constant current sink._
The bias current will be 25mA independently of HT or of the tube used.
It will also actively counteract the current variations, mostly in the bass frequencies, this probably explains the original poor bass.
Bass dramatically improved (almost too much...) since I replaced the cathode caps by Nichicon Muse 1000uF and the coupling caps by Mundorf silver gold oil .47uF.

My 6F6's are on their way from Ukraine


----------



## pvico (May 12, 2017)

When I used the Tung Sol KT66 Reissue's, the right tube glowed noticeably brighter than the left one. Intrigued, I measured the voltages at the heater pins of both tubes: the left one had 5.50V and the right one 6.09V.
While 6.09V is within specs (6.3V +- 10%), 5.50V is too low and this can lead to _cathode poisoning_, degrading the tube over time. However, I did not notice a significant difference in audio output between the left and right sides (but I'm not an expert audiophile).

I removed the tubes and powered their heaters from my bench power supply set on a stable 6.3V. One tube had .890A, the other .918A, so there is a slight imbalance between the 2 tube heaters.

Because the heaters are connected in series, that imbalance is exacerbated: the more they heat up, the more the heater resistance increases which further increases the imbalance (the TS KT66 heater has a resistance of 2 ohm when cold increasing to 7 ohm when at temperature, all tubes react in a similar way).

If you have the possibility to do so (if you have more than 2 tubes of the same model), try different combinations of them so that they glow in a similar way.

*WARNING*​*If you want to measure the heater voltages while the amp is powered, do that only if you know what you are doing. The HT voltage can kill you!*


----------



## Maxx134 (May 13, 2017)

pvico said:


> Q2 with the help of IC3 and R29/R30 is a _constant current sink._


Excellent..
I always Iike to share info so that others may learn whats going on in a circuit so to try understand the choices these designers make in thier circuits..

This was done in the Little Dot Supermod thread,
so others can learn instead of being in the dark as to whats going on.




pvico said:


> If you have the possibility to do so (if you have more than 2 tubes of the same model), try different combinations of them so that they glow in a similar way



Yes this seems common to tubes.
The heater coil will light up different pace on every tube.

Plus,  if the heaters of the tubes are in series like you say on this amp,


pvico said:


> Because the heaters are connected in series, that imbalance is exacerbated


 then for sure they will never light up same time,  hehe. 

The heaters are mini coils by nature not even.
Sometimes the cold resistance of the heater will be the issue,  as it will be  lower than the hot resistance,
Which is the case if the ends of the heater is sticking out of the cathode sleeve and or visible.

Cold heater resistance  causes short term inrush current and localised heating creating quick flash or bright glow.
You sometimes see the difference lighting up faster,  as there is a short current 'burst' creating a "heater flash".
I have one set of Mullard tubes that scared crap out of me when they did this on every startup lol. 

So, Once the coil heats up the resistance increases and the current falls and heating becomes uniform over the whole length of the heater wire.
Anyways, "heater flash" is not an issue.
Instead,  it is an  indication of NOS and old, very early production years,
which are usually considered as tubes of a higher quality than New stock current production types .


----------



## Maxx134 (May 13, 2017)

pvico said:


> When I used the Tung Sol KT66 Reissue's


I also still have the same reissue tubes, they look dam pretty.
I also have the big 6L6 and others I rolled into this amp... 
I need to make a list..
The 6F6 sounds better still.


----------



## baronbeehive (May 13, 2017)

Maxx134 said:


> Excellent..
> .............
> 
> Yes this seems common to tubes.
> ...



I always wondered about this since seeing a friends tubes flash on startup, then my Amperex 12AX7's did the same thing but not the Amperex EL84's. It's fun when you get used to it but the first time it happens you freak out.

That's also useful to know about the heater glow. I've always swopped around the tubes to find the right combination but something puzzled me lately. I was trying to equalize the sound output from each power tube by ear and by the glow and I didn't realize that although I had a stronger glowing tube on one channel it sounded weaker. So that explains that, now I understand I was going by the heater glow not tube trandsconductance.

Edit:
When I said in a previous post that the transients were sharper I really meant faster, clearer and more detailed, because they do not sound sharp.
And in that respect it is better than my headphone amp - the modded Little Dot MKVI+.

Damn I really want one of these babies now to go with my PA0901A APPJ!


----------



## jekjek

Thank you Maxx134 and pvico for your contribution to this thread
I learn a lot more about this amp and cancel my plan to measure the heater voltage


----------



## Maxx134

baronbeehive said:


> Edit:
> When I said in a previous post that the transients were sharper I really meant faster, clearer and more detailed, because they do not sound sharp.
> And in that respect it is better than my headphone amp - the modded Little Dot MKVI+.



From what I have learned about those amps,  is their clarity and detailing is mostly attributing to the tubes and bias points,  once the amp is sufficiently moded,  as the circuit design is very good. 

Especially the issue of soundstage and detailing is dependent on bias. 
In Your specific case,  the driver tube bias need to be boosted and you will be shocked how much more it can go....


----------



## baronbeehive

Maxx134 said:


> From what I have learned about those amps,  is their clarity and detailing is mostly attributing to the tubes and bias points,  once the amp is sufficiently moded,  as the circuit design is very good.
> 
> Especially the issue of soundstage and detailing is dependent on bias.
> In Your specific case,  the driver tube bias need to be boosted and you will be shocked how much more it can go....



Right! I won't hijack this thread but you are right I haven't tested, or finished all the mods completely yet so I look forward to confirming that. But the speed of the these SET amps is second to none. I'm glad though that the APPJ's sound is rich as well as fast because I think if it goes too fast and transparent without any contribution from the tube sound then the sound is going dangerously close to SS sound which I don't want. That would put me off going for a decware amp for example although they are outstanding amps by all account.

Anyway I'm very happy with both my headphone amp, and the little APPJ of course! The thought just crossed my mind that the 2 APPJ's side by side would be a great
talking point and it would be interesting to compare their sounds although comparing headphones with speakers would make that difficult it would be interesting to hear from someone who had them both, or maybe I'm just fantasizing, probably!


----------



## Maxx134 (May 14, 2017)

baronbeehive said:


> going for a decware amp for example although they are outstanding amps by all account


From learning about apps and the moding threads,
You can get a feel of an amp just by looking at the insides...

I am hoping ZMF creator Zack gets his suggestions implemented on the designs Decware is doing for him.

Many designs have same issue of having to rely on a coupling device between stages,  and most time it is a coupling  cap over an interstage transformer...
So the quality of this device is the pivot point of the whole amp.
That's why,  for this amp,  I specifically suggest best caps you can get...

My suggestion will always be a copper foil as best for that specific scenario...





baronbeehive said:


> 2 APPJ's side by side would be a great
> talking point


I think the short period of the  mass drop sale may be over...
It was just posted a few page back..


----------



## benjisun

This topic is getting very interesting; 

For me it's end of the mod game,  (after trying 1000 uf mundorf)
Stock 220 uf/220V replaced by Nichicon FG fine gold 330 uf/50v
Stock 0,1 uf ceramic replaced by Audyn Qs6 0,47 uf 

Did some of you tried to replace the fuze ? It"s by default a poor 1,6 amp model. I added a ceramic 2,5 a instead. 

I'm very hapy with the sound of this little amp.


----------



## Maxx134 (May 22, 2017)

This non-traditional switching PSU,  probably have different  sensitivities of normal PSU when it comes to noise or fuse or current capabilities.

Another thing to consider is that too large a coupling cap may introduce unwanted low frequency oscillation or changes to the global feedback.

I am currently using .68uf wich  I do not recommend,  as I encountered  detectable oscillation with use of the "42" tube with adapter,
but only at zero volume...

So adverse effects can happen and  with splice or oscilloscope would have known if we had all the detailed circuit values.

Another point about the coupling cap in this circuit,
 is that when I tried .2uf it was not optimal,
 yet once I went up to .3uf,  it  sounded optimal,
as no benefit/gains was observed going bigger.

So my recommended max value for the coupling cap here,  would be .47uf, with around .33uf being optimal.

Yet on another note,
The  quality" or type of the coupling cap,
 did have effect with treble tonality and soundstage.

Same observation with my big amp.

Edit**
Had a zero by mistake in my cap values.

Only in my additional bypass cap, ( that is paralleled to the main electrolytic cathode cap) ,
Did I use a small value of .047uf,
And recommend no higher than .1uf additional bypass value is necessary to help that area.


----------



## baronbeehive (May 15, 2017)

Maxx134 said:


> .......
> 
> Many designs have same issue of having to rely on a coupling device between stages,  and most time it is a coupling  cap over an interstage transformer...
> So the quality of this device is the pivot point of the whole amp.
> ...



I really don't want to go on about this but the Jupiter caps have transformed this amp from a good one to a great one, and I really don't know how this has happened, it is after all just a coupling cap and therefore cannot change the nature of the circuit, only optimize what is already there!



benjisun said:


> This topic is getting very interesting;
> ....
> 
> Did some of you tried to replace the fuze ? It"s by default a poor 1,6 amp model. I added a ceramic 2,5 a instead.



Yes I replaced it with a similar one to yours, not because I'm hopeful of it transformig sound quality but just it was easy to do, and you ever know.....




Maxx134 said:


> ..........
> 
> Another thing to consider is that too large a coupling cap may introduce unwanted low frequency oscillation or changes to the global feedback.
> 
> ...



Yes I would not have gone higher than 1uF for that reason, also it's debateable that anything higher could be heard anyway.

What did these oscillations sound like?

Edit:
Silly me, obviously you can't hear them at zero volume, I assume you picked them up using an oscilloscope.


----------



## CZ4A

pvico said:


> Yes, I just measured HT (B+) at 179V and the heater voltage at 11.7V (with the original tubes). I have updated the schematic accordingly. Here (Belgium), the mains voltage is 230V. If you're in the UK, it's more likely 240V which can explain the difference.





pvico said:


> When I used the Tung Sol KT66 Reissue's, the right tube glowed noticeably brighter than the left one. Intrigued, I measured the voltages at the heater pins of both tubes: the left one had 5.50V and the right one 6.09V.



I will try to get some heater and HT measurements and see if there's any difference between your measurements on Belgian 230V mains and mine on US 120V mains. FWIW I haven't noticed a visual difference in the heater glow on any of my power tubes, but that doesn't meant they aren't running at different voltages of course.



Maxx134 said:


> I also still have the same reissue tubes, they look dam pretty.
> I also have the big 6L6 and others I rolled into this amp...
> I need to make a list..
> The 6F6 sounds better still.



I've yet to try any 6F6s. My coworker is giving me the tuner/amp section of an old Admiral console radio that uses them. So once I have that radio's guts I can test the 6F6s and roll them in the APPJ if they're still good.


----------



## Maxx134 (May 16, 2017)

baronbeehive said:


> What did these oscillations sound like?


Nothing major,  just a few audible tiny quick  clicks while unit starts up,  audible only on one side, with volume all the way down.(!)

Its not the tubes,  as it happens to a few that not have it before,
And doesn't happen all the time on startup,
And also can be simulated with using two different output tubes at same  time,  NOT RECOMMEND,  Lol.
Also I could not detect any low frequency oscillation on output but would need to test the transformer primary to but since it only sometimes at startup,  I not worried about it.




CZ4A said:


> I can test the 6F6s and roll them in the APPJ if they're still good


Looks like I  will have to reevaluate all the  tubes I tried, with notes about tonality of each tube,
Because now after upgrades done and burned in,  the 6L6 is now performing nicely.
Specifically,  It does not distort at max volume and I cannot even turn it up that loud.



The 6F6 does  go a bit louder but  a slight distorted encountered at max vol .
I can only briefly turn up because it just to loud.

So looks like this amp can now handle planars nicely without strain.


----------



## Minbeo (May 20, 2017)

First i  wanna thanks Max and other people for sharing. I've done replaced the amp's capacitors with these:
- 0.47uf/800v Jantzen superior z-cap
- 1000uf/50v Elna Silmic II
The result is generally good, fuller sound, better resolution, less sibilance_, _well worth the money and hassle(struggle with soldering ). But somehow i feel the amp sound quite a bit slower, the bass doesn't sound as snappy as before. Do you guys have any insight on this? caps value? better caps? thanks alot.


----------



## pvico (May 20, 2017)

Just tested with the Russian military 6F6's and I must say it is great, much more balanced than the TS KT66's.
Current setup:

Preamp tube: JJ 5751
Power tubes: 6F6 (Ebay seller from Ukraine)
Coupling caps: Mundorf MCAP EVO Silver Gold Oil 0.47µF
Bypass caps: Nichicon KZ Muse 1000µF
Beyer DT770 PRO 80 ohm


----------



## pvico

CZ4A said:


> I will try to get some heater and HT measurements and see if there's any difference between your measurements on Belgian 230V mains and mine on US 120V mains. FWIW I haven't noticed a visual difference in the heater glow on any of my power tubes, but that doesn't meant they aren't running at different voltages of course.


Yes, the US switching PSU is obviously different from the EU one (230V with 10% tolerance, UK was traditionally 240V and my country was 220V. I measured 230V at the mains outlet).
With the KT66's, the glow was noticeably different _on a steady state, _not just on startup. Seems OK with the 6F6's. YMMV.


----------



## Maxx134

Minbeo said:


> But somehow i feel the amp sound quite a bit slower, the bass doesn't sound as snappy as before.



Those Jantzen caps are actually  supposed to be better than the Mundorf,
So  It is quite possible a few things going on.
The caps need break in period and the power tubes are responding differently to the change in parameters.
So you can also be hearing true sound of your tube selection. 

To offset any initial slowness or other effects of replacement cathode caps,
I added a Second small paralleled decoupling cap to the electrolytics (cathode bypass cap). ..
It is same or similar quality & brand as the coupling cap.
Look back in thread to note some others have done also
That should solve your issue. 
 



pvico said:


> Just tested with the Russian military 6F6's and I must say it is great, much more balanced than the TS KT66's.


Yes I find them very detailed and a touch brighter/closer than the other 6F6 I have.
So you have more options to match it with a preamp tube of your choice.

These russian tubes are low cost and old stock tubes,  so they are just a dam great option.
I like them over my best juicy sounding Tung-sol because of the slight edge they have in treble air and detail.
Many thanks to member *"Kryl007" *for the suggestion.


----------



## baronbeehive (May 20, 2017)

Minbeo said:


> First i  wanna thanks Max and other people for sharing. I've done replaced the amp's capacitors with these:
> - 0.47uf/800v Jantzen superior z-cap
> - 1000uf/50v Elna Silmic II
> The result is generally good, fuller sound, better resolution, less sibilance_, _well worth the money and hassle(struggle with soldering ). But somehow i feel the amp sound quite a bit slower, the bass doesn't sound as snappy as before. Do you guys have any insight on this? caps value? better caps? thanks alot.



I'm not finding this with similar mods on my speaker amp. The frequencies on the transients are better, both low and high as far as I can ascertain leading to the  greater detail and dynamics I mentioned before.
If it seems you are lacking the higher frequencies, it could be that you have a better frequency range now, low and high which is causing you to think that you have  lost the higher frequencies you had before. The caps are good so no problems there.
What tubes are you using atm?
Edit: With 0.47 caps your amp should be bassier but any perceived loss of higher frequency response could be helped by crisper sounding tubes.
For example you could try JJ 12AX7's which are very quick and detailed sounding with snappy bass.
I might try some cathode bypass caps myself to see if this makes much difference but for the moment I'm happy with the sound.

Maxx, do you think a 470uF 25v cathode cap would work roughly the same as a 1000uF cap with a bypass cap linked?


----------



## Minbeo

Maxx134 said:


> Those Jantzen caps are actually  supposed to be better than the Mundorf,
> So  It is quite possible a few things going on.
> The caps need break in period and the power tubes are responding differently to the change in parameters.
> So you can also be hearing true sound of your tube selection.
> ...


Thanks Maxx , the sound does open up after a while, or maybe my ears are getting used to the fuller & more textured sound of the new caps. I like the caps upgrade enough to order a pair of  0.1uf Jantzen superior just for fun.



baronbeehive said:


> I'm not finding this with similar mods on my speaker amp. The frequencies on the transients are better, both low and high as far as I can ascertain leading to the  greater detail and dynamics I mentioned before.
> If it seems you are lacking the higher frequencies, it could be that you have a better frequency range now, low and high which is causing you to think that you have  lost the higher frequencies you had before. The caps are good so no problems there.
> What tubes are you using atm?
> Edit: With 0.47 caps your amp should be bassier but any perceived loss of higher frequency response could be helped by crisper sounding tubes.
> ...


Thanks Baron, actually i'm using a very similar amp from APPJ(with Voshkod 6j1p + Sylvania 6005 tubs) https://www.massdrop.com/buy/appj-mini2013-6j1-6p1
And yes, those upgrade caps add some serious slams to the amp's bass  love it!. I also agree that better frequency range make you feel the treble is not as stand out as before, i'd bypass those huge 1000uf Silmic II(seriously they're the same size of Jantzen film caps) with 0.1uf Jantzen superior to see what happens.


----------



## baronbeehive (May 21, 2017)

Minbeo said:


> Thanks Maxx , the sound does open up after a while, or maybe my ears are getting used to the fuller & more textured sound of the new caps. I like the caps upgrade enough to order a pair of  0.1uf Jantzen superior just for fun.
> 
> 
> Thanks Baron, actually i'm using a very similar amp from APPJ(with Voshkod 6j1p + Sylvania 6005 tubs) https://www.massdrop.com/buy/appj-mini2013-6j1-6p1
> And yes, those upgrade caps add some serious slams to the amp's bass  love it!. I also agree that better frequency range make you feel the treble is not as stand out as before, i'd bypass those huge 1000uf Silmic II(seriously they're the same size of Jantzen film caps) with 0.1uf Jantzen superior to see what happens.



Excellent! I would be very interested to hear what you think. I don't want to disturb my cathode caps yet, they will have to come out to put in bypass caps and I can't be bothered atm, besides I'm enjoying it as it is too much .

Edit: Those large capacitance caps should make the amp quicker but the values may need to be in a suitable range for the circuitry so as not to cause, for example, the oscillations that Maxx mentioned. Also the types of caps used can have certain properties such that, for example a bypass cap of a certain type helps out the main cap in certain areas, such as in treble.


----------



## Minbeo

Maxx134 said:


> Another point about the coupling cap in this circuit,
> is that when I tried .02uf it was not optimal,
> yet once I went up to .03uf,  it  sounded optimal,
> as no benefit/gains was observed going bigger.
> So my recommended max value for the coupling cap here,  would be .047uf, with around .033uf being optimal.


Hi Maxx, i've just wanted to ask: is there any disadvantage of using 0.47uf coupling cap instead optimally 0.33uf, they're almost the same price. Is 0.33uf-0.47uf good values for bypassing cathode caps too? thankss


----------



## Minbeo (May 22, 2017)

baronbeehive said:


> Excellent! I would be very interested to hear what you think. I don't want to disturb my cathode caps yet, they will have to come out to put in bypass caps and I can't be bothered atm, besides I'm enjoying it as it is too much .
> 
> Edit: Those large capacitance caps should make the amp quicker but the values may need to be in a suitable range for the circuitry so as not to cause, for example, the oscillations that Maxx mentioned. Also the types of caps used can have certain properties such that, for example a bypass cap of a certain type helps out the main cap in certain areas, such as in treble.


So i bypassed 1000uf Silmic II with 2 cheap Jantzen Cross-cap 0.1uf my friend gave me. Just based on memory: It sound much more to my liking: The bass tidy up, before it was powerfull but a bit messy and overwhelm the mid, now the vocals are bit more forward and clearer, treble detail is backkk! cymbals are sparkling again . Ofcourse my experience might much differ than yours (I'm using a modded HD800 & my prefered sound's clear, fast, airy sound)


----------



## baronbeehive (May 22, 2017)

Minbeo said:


> So i bypassed 1000uf Silmic II with 2 cheap Jantzen Cross-cap 0.1uf my friend gave me. Just based on memory: It sound much more to my liking: The bass tidy up, before it was powerfull but a bit messy and overwhelm the mid, now the vocals are bit more forward and clearer, treble detail is backkk! cymbals are sparkling again . Ofcourse my experience might much differ than yours (I'm using a modded HD800 & my prefered sound's clear, fast, airy sound)



Thanks Minbeo! Very interesting, looks like it makes a difference.

You want to go small and fast for the bypass caps for treble detail, no more than 0.1uF, Maxx will confirm and let you know about the coupling caps as well.

Edit: The step up from .1uF to .47uF would explain your rich bass sound. The difference between .47uF and .33uF is small and I would think that if you really like the fast airy sound then you could consider going down to .22uF. That would be nearer the stock sound but with better quality caps and much better gain and power delivery with the uprated cathode caps.


----------



## Maxx134 (May 22, 2017)

baronbeehive said:


> For example you could try JJ 12AX7's which are very quick and detailed sounding with snappy bass.


For your specific case,   for certain,  that you will have greater resolve with an adapter to an Octal tube and use an old 12SL7 with round plates.
I guarantee you will hear more improvement... (!!!)





baronbeehive said:


> I might try some cathode bypass caps myself to see if this makes much difference but for the moment I'm happy with the sound.
> 
> Maxx, do you think a 470uF 25v cathode cap would work roughly the same as a 1000uF cap with a bypass cap linked?


NOOoooowwaaahhh!!..  Lol

I already tried myself and the improvement was like 30% compared to the 1000uf,  and I am not exaggerating.

With my version using larger tubes, the chances of power drain and voltage fluctuation of cathode was noticable.
For optimal improvement,  use 1000uf.

I also have dicussed trying larger values in PMs,
 and it was concluded that any larger than 1000uf is unnecessary,
 as the stability of voltage drop at cathode is already accomolished,  so no more gains especially when using  tubes with less demands.




Minbeo said:


> i'd bypass those huge 1000uf Silmic II(seriously they're the same size of Jantzen film caps) with 0.1uf Jantzen superior to see what happens.


This was the most wise decision,
As your scenario needed more clarity,
 and the .1uf bypass value  effectively takes care (of helping response of the electrolytic),
From the treble freq range all way down to the upper bass area,
With the cutoff freq depending on the power tube stage impedance at that cathode area,  so we can only generalize/estimated based on the tube data.



Minbeo said:


> Hi Maxx, i've just wanted to ask: is there any disadvantage of using 0.47uf coupling cap instead optimally 0.33uf, they're almost the same price. Is 0.33uf-0.47uf good values for bypassing cathode caps too? thankss


Sure,  get the . 47uf!
No problem as long as dont go higher in capacitance value for the"coupling cap" area...(to avoid any feedback oscillaton)

Also, Voltage values of these film caps will generally be high,  (which is excellent)...

Remember...
  the higher the cap voltage rating,
 The better for "transients" and lower capacitor "ESR" value,  wich equates to better response time.
Which is a very good thing..

That's why your cheapo stock coupling caps had such high voltage ratings..


----------



## Minbeo

baronbeehive said:


> Edit: The step up from .1uF to .47uF would explain your rich bass sound. The difference between .47uF and .33uF is small and I would think that if you really like the fast airy sound then you could consider going down to .22uF. That would be nearer the stock sound but with better quality caps and much better gain and power delivery with the uprated cathode caps.


Thanks Baron, After bypassing the cathode caps, i'm now very happy with the sound, the sound is rich, textured, fast enough & crazy dynamic, i odered a few more caps just for playing around anyway



Maxx134 said:


> Also, Voltage values of these film caps will generally be high,  (which is excellent)...
> 
> Remember...
> the higher the cap voltage rating,
> ...


Thanks Maxx for your detail explanation,
Those Jantzen Superiror 0.1-0.33uf are rated 1200v! must be a good thing right? 
I admit i surprised with recapping result, not dramatic tonality change like re-tube but like the amp stopped holding back, everything improve, especially in dynamic.
Maybe i just really like SET sound but i own a Schiit vali2 & tried Schiit Valhalla 2 for a few days but never impressed by them. Kudos to APPJ, for the prices even unmodded these things are really hard to beat.


----------



## Maxx134 (May 23, 2017)

Minbeo said:


> Maybe i just really like SET sound but i own a Schiit vali2 & tried Schiit Valhalla 2 for a few days but never impressed by them. Kudos to APPJ, for the prices even unmodded these things are really hard to beat.


I owned the original Vali and it was a sweet toy.
The Valhalla2 is an extremely good design and tube selection for sound,  but not power.

It is weakened by using an similar  coupling cap like this stock one on these amps.

Remember the need to be competitive in the market,  outweighs the need for any  expense.
It hard to get a better coupling cap without raising the price substantially.

So yeah,  you would achieve a similar level quality by getting  a valhalla2 and replacing its caps as well,
But you still have less power on a  more expensive amp.
Too bad they didn't double up on those power tubes,  like in the LittleDot MK6 & MK8..

They should have chosen a pentiode (triode strapped)  or a more powerful output tube.


----------



## CZ4A

pvico said:


> Yes, the US switching PSU is obviously different from the EU one (230V with 10% tolerance, UK was traditionally 240V and my country was 220V. I measured 230V at the mains outlet).
> With the KT66's, the glow was noticeably different _on a steady state, _not just on startup. Seems OK with the 6F6's. YMMV.



I got some measurements of the heater voltages when connected to US mains power. I still need to get the HT/B+ readings and also perhaps cathode to plate voltage on the power tubes. I used the original 6P6P tubes and a 12AT7 (same heater ratings as 12AX7) when measuring.

Wall socket: 122.2V
12AT7: 12.21V
Left 6V6: 6.2V
Right 6V6: 5.95V

As I suspected the two power tubes are running at different voltages, but both are within 10% of 6.3V. The preamp tube is also within tolerance. That being said, the wall socket I plugged the APPJ into is a bit more powerful than nominal 120V. When I measure HT I will plug the amp into my Variac that I just bought and get measurements at exactly 120V.


----------



## baronbeehive

I decided to fit cathode bypass caps after what a couple of members have said after fitting their cathode caps. They felt something might not be quite right at the higher frequencies possibly, and I have a suspicion they might be right. That's why the big 1000uF caps need the bypass to compensate for lack of treble. So Audyn True Copper 0.1uF's have gone in. I've had to extend the bottom much as Maxx had to do with his.

The whole operation was a bit more tricky than I expected mainly due to the small board, confined space and relatively large parts, and I had to make a couple of repairs to it as I went along due to a couple of the tiny pads breaking off, so try to be careful lol!

I've only just started listening, but first impressions are that indeed the treble is back, as Minbeo said, and the sound is fantastic, but I now need a whole lot more listening time to enjoy it.

Next up, I'm going to replace my favourite tungsol 5751's with another favourite, the 12v version of the 6SL7 Tungsol that I use on my headphone amp so should be interesting.

... oh and then there's the Russian cobras together with an adapter......

Pics to follow.


----------



## Minbeo

pvico said:


> For those interested, here is the schematic of the amplifier.
> https://www.dropbox.com/s/ggm7a0la2era3n3/PA1502A APPJ Schematic.png?dl=0
> Here is the LtSpice simulation package:
> https://www.dropbox.com/s/rk5oukakn2bzwzg/PA1502A APPJ.zip?dl=0


Thanks Pvico for the schematic, i replaced C04+C05 with 1800uf/40V Epcos Sikorel125, the result is very nice so now i want to replace C07+C08 with Sikorel125 47uf/270V(3 in parallel). I wonder is that safe cause as you said HT voltage rise up above 270V on startup?Tks


----------



## Peter Guo

This little amp can be used for speakers too, I have a monitor Audio I-deck at office and I used its speakers, this amp can drive the speaker up to 8 volts in high gain mode, which is about 5 watts. The second harmonic is about -37dB down at around 1 watts, at 4 Watts, the third harmonic is -36dB and the second  is about -30dB. Very impressive numbers, I think because it uses NFB.


----------



## baronbeehive

....so maybe I ought to get rid of my speaker APPJ and just get one of these!

I also have monitor audio speakers and its the perfect system for me.

So how do you change the gain. My speaker APPJ has 3 choices of output, 4ohm, 6ohm and 8ohm, makes for a very custom system.


----------



## Maxx134 (Jun 14, 2017)

baronbeehive said:


> My speaker APPJ has 3 choices of output, 4ohm, 6ohm and 8ohm, makes for a very custom system.



My model does not give such output options, and opening inside did not help.

So I believe you can drive headphones with just an adapter from the speaker terminals to a headphone jack.
The you can try all three outputs for different headphones matching.
The output will decrease but "should" still be stronger than mine.
Edit:
How many watts is your model?


----------



## jekjek

Or you can use the  APPJ headphone adapter.

Review is as below

https://www.head-fi.org/f/threads/h...p-emotiva-mini-x-a-100-project.629352/page-24

It is 99 dlr a piece. Not cheap


----------



## baronbeehive

Maxx134 said:


> My model does not give such output options, and opening inside did not help.
> 
> So I believe you can drive headphones with just an adapter from the speaker terminals to a headphone jack.
> The you can try all three outputs for different headphones matching.
> ...



I didn't know about this, thanks.

My APPJ is 3.5 watts.



jekjek said:


> Or you can use the  APPJ headphone adapter.
> 
> Review is as below
> 
> ...



Thanks, I didn't know about this either, looks interesting!

BTW I said that my first impressions were that the treble is back, well as an update to that, after longer listening time, I can confirm that is the case. The transient leading edge is now even more detailed, yet it is not sibilant or harsh, and the trailing edges are very natural.

I am so stunned that I don't see how this can be bettered without spending thousands lol!


----------



## Peter Guo

Peter Guo said:


> This little amp can be used for speakers too, I have a monitor Audio I-deck at office and I used its speakers, this amp can drive the speaker up to 8 volts in high gain mode, which is about 5 watts. The second harmonic is about -37dB down at around 1 watts, at 4 Watts, the third harmonic is -36dB and the second  is about -30dB. Very impressive numbers, I think because it uses NFB.


Forgot to mention the frequency is +/-1dB from 20-30kHz for my 7.5 Ohm resistor load.


----------



## Maxx134

baronbeehive said:


> I am so stunned that I don't see how this can be bettered without spending thousands lol



This also was nagging question just how the H*ll is this little thing able to do such a nice job in clarity.

I then realized it is using modern designs to keep the tubes performing at more ideal conditions.

That type topology/design thinking is similar to the  DIY amp (MrCurwen design)  that member SonicTrance posted in the Little Dot super mod thread.

So yeah, to go higher,  you either go into & over $1k range..
Or choose modern DIY designs .

Going higher should give the larger Soundstage and more separation.


----------



## baronbeehive (Jun 15, 2017)

Maxx134 said:


> This also was nagging question just how the H*ll is this little thing able to do such a nice job in clarity.
> 
> ............
> 
> Going higher should give the larger Soundstage and more separation.



Yes, but these Jupiter coupling caps have already upped that considerably, you can now hear musicians clearly performing in their own space and singers separated nicely. For example 2 or 3 girl backing singers can be easily heard separately, and together, and also I've heard things like very faint bell chimes in the background which I never heard before. And the whole thing is very clearly resolved, I won't go on.... but I'm very happy now .

Edit: I noticed a similar thing with the headphone amp mods and that's nowhere near full volume.... that would be antisocial with this amp now!!

Got the 12SL7 TS and adapter, just waiting for the Cobras now! Hoping to extend the bottom case in next few days.


----------



## CZ4A

So I tried a more "exotic" type of preamp tube in this amp recently, an FDD20. For tubeheads, it is the electrical equivalent of the 6N7 except for a 12V heater and the European side-contact base (like the EL3N some here are using for power tubes).







I used an eBay FDD20-to-12AU7 adapter (http://www.ebay.com/itm/1pc-Philips-FDD20-TO-12AU7-ECC82-Tube-converter-adapter-12-6V-/191678650030) to install it. I had to cut the socket mounting tabs off the adapter with my Dremel tool. I could only use GT-style power tubes as the big adapter makes for a tight fit.

Verdict- it sounds terrible in the APPJ. The bass is nearly silent and vocals and mids are severely recessed. The channels sound slightly out of phase as well. The FDD20 in the APPJ reminds me of listening to an economy car stereo with at lease one blown-out speaker. After speaking to someone in the Feliks Elise thread it's likely the sound won't improve with a break-in period. So there's either something wrong with the tube, the adapter, or most likely, the FDD20 isn't entirely compatible with the PA1502A. I'm guessing something with bias or the way the cathode circuit is configured in the amp. The 6N7 can be used as a preamp tube in spite of the common cathode (and I have an Mullard ECC31 (6N7G) that sounds excellent in my Project Sunrise), but the triode circuits have to be in parallel. I haven't had a chance to look at the schematic again.


----------



## baronbeehive (Jun 27, 2017)

This little amp just got a bit bigger:















Now going to try out the TS 12SL7. Still waiting for the adapters for the Russian cobras.

This amp does nothing badly, and everything really well.

So glad I got it about 5 years ago.


----------



## jekjek

Let us know the first impression after the upgrade


----------



## baronbeehive (Jun 28, 2017)

jekjek said:


> Let us know the first impression after the upgrade



OK, I haven't gone into detail because I don't like too much analysis, and as I've already said the sound is now fantastic and you know when it just sounds right! I've already given my first impressions and since then only completed the work on extending the chassis to fit the bypass caps so all much as I've said.

Bear in mind that this applies to the speaker APPJ. Also my tubes have already upgraded the stock sound a lot. I've settled on my favourites: Amperex EL84 - warm clear sound, and Tungsol 5751 - liquid detailed sound. The stock sound with NOS tubes was already good but after the caps upgrade the main differences were: richer, more powerful, sound, the bass is tight and visceral and definitely does not need a woofer for example, more accentuated transients, more realism, due mainly I believe to the quality of replacement caps, of course anything better than stock would be good. Finally the whole sound is more resolved, ie good separation of layers in the music, each layer having greater clarity.

That's really as much as I want to say, I just want to enjoy it  now, which I am doing lol! I will give brief impressions when I've tried the TS 12SL7 which I expect to be similar sounding to the 5751, and the Russian cobras after Maxx's and others research into different tubes which I just wanted to try, but I'm very happy with this amp .

Also I wanted to say to anyone interested in doing these mods that if you are fitting the large capacitance 1000uF cathode caps to get the increased reservoir of power for recovery from momentary power dips then you should also fit some good lower capacity bypass caps to help out the treble, otherwise you will lack this, which some members who have done this have found.


----------



## Maxx134

CZ4A said:


> The 6N7 can be used as a preamp tube in spite of the common cathode


I believe your issue is that the driver tube in this amp is not supposed to have a common cathode.

They're are two separate channels per triode,
and you just joined them at the Cathode by using that tube...

Your probably hearing cancelations of frequencies and possible circuit distortions caused by joining them.


----------



## Maxx134

baronbeehive said:


> This little amp just got a bit bigger:


Hey buddy!
Yours looking better than mine!
The advantage I see in your amp is the  different impedance outputs,
And I bet you can get an adapter to try plug your headphones to it which should end up with about same wattage power into headphones that I have.


----------



## baronbeehive (Jul 5, 2017)

Maxx134 said:


> Hey buddy!
> Yours looking better than mine!
> The advantage I see in your amp is the  different impedance outputs,
> And I bet you can get an adapter to try plug your headphones to it which should end up with about same wattage power into headphones that I have.



Ha ha....and it's gold plated, at least the door handle is (brass, actually)!!
I've tried the different outputs and can't tell much difference at least with my speakers. The speakers are 6 ohm so they fall right in the middle of the 4, 6 and 8 ohm outputs.
I've looked into the headphone adapter and atm there seem to be connection issues so I'm a bit dubious about using it so that's for later maybe.
The chassis extension was a nightmare trying not to ruin the heatsink fins boring the screw holes lol!

The sound just gets better and better! Glad I got the Audyn True Copper bypass caps like you have, they go seamlessly with the others soundwise.


----------



## CZ4A

Maxx134 said:


> I believe your issue is that the driver tube in this amp is not supposed to have a common cathode.
> 
> They're are two separate channels per triode,
> and you just joined them at the Cathode by using that tube...
> ...



Thanks for the confirmation. I suspected as much. Here's where I read about using the 6N7 in a class A amp circuit that inspired me to try the FDD20: https://vinylsavor.blogspot.com/2011/02/tube-of-month-6n7.html.


----------



## baronbeehive

My little speaker amp just got a bit more like your baby headphone amp:





Adapters arrived today, looking forward to trying new tubes!


----------



## baronbeehive (Jul 11, 2017)

Hey Maxx you were right about the 12SL7's my friend! You know I don't like to exaggerate but I can only say I've just spent the last hour or so on another planet from the moment I switched on the amp. I really don't want to say more but the tube is staying for sure.

Only one snag, the higher gain is fantastic on this amp but I can hear static now on the right channel when turning the volume knob, once adjusted everything's fine.

The other thing, I tried the Russian Kobra's and... nothing! I can only assume there is an impedance or power mismatch, not really a problem, I liked the look of them but the Amperexes are fine anyway.

Edit:
The static could be down to the tube, or adapter, there is no trace of it with the 5751 tubes. Despite that the sound of this little amp is now very special!

I can say a bit more about the TS12SL7 tube now I've listened to it. It is so gloriously liquid and effortless sounding with a wide soundstage, you just feel totally immersed. It has no rough edges at all.


----------



## DavidK35

Gemtune Amp Part 1

Got my amp last week & been burning in tubes & auditioning. Still waiting for adaaptor & 12SL7/12SN7 tubes but in the meantime have hooked up the power tubes with different miniature driver tubes consisting of:

12AX7 Tung Sol new issue
12AT7 WA Sylvania triple mica
6211 RCA black plate triple mica

Although I expect the bigger 12SN7 series to outperform these tubes, I thought it would be interesting while I wait, to try these out. 
The 12AX7 turned out to be dissapointing, with a raggedy top end & average elswhere.
The 12AT7 was good with great soundstage, vibrant sound great bass but slightly coarse & emphasised top end.
The 6211 was the pick of the bunch & has been my favourite 12AT7 type tube for a long time after having tried almost all the different types. This tube is dark by comparison with a slightly rolled off top end, which I really like, great sounstage, good well defined bass & sweet top end. Also had the highest clarity defining individual instruments the best but very cohesively.

I think I am the first in this thread to use the 6BG6 G series tubes that have the external wire & cap with suitable adaptor. So far I think this is the best sounding head amp I have tied so far (#6) so cannot wait to roll some other tubes. Coming are the 6SN7 & 6SL7 drivers + 6AG6G/EL33 power tubes. From the picture you see all 3 tubes have risers/socket protectors giving the very totem pole look (top to bottom 9"). I ordered my amp without tubes for $159.00 + $30 fedex 5 day. Time will tell if the 6BG6 proves better or not than the 6AG6G types & I may also try the 6L6G types but they are a bit pricey.

To be continued.


----------



## baronbeehive

DavidK35 said:


> Gemtune Amp Part 1
> 
> Got my amp last week & been burning in tubes & auditioning. Still waiting for adaaptor & 12SL7/12SN7 tubes but in the meantime have hooked up the power tubes with different miniature driver tubes consisting of:
> 
> ...



Hi DavidK35, welcome!

I agree with you about the TS and Sylvanias, I don't like new issues at all, except for possibly the JJ's. I've also tried the Sylvania JHS 5751 triple mica which sounds similar to what you say about the 12AT7, although a little light. The TS 5751, my favourite tube, rounds off that treble nicely btw!  Interesting what you say about the 6211 RCA - sounds characteristically RCA - except for the clarity.  I also love RCA's!

The 12SN7's and 12SL7's I find identical sounding but for my amp which is the speaker version of the APPJ the SL7 is best due to the higher gain.

If you think 6L6G's pricey what about trying the Russian 6F6C's that others on this thread recommend, they are very cheap!


----------



## DavidK35

Interesting you mention 6F6C tubes, I missed that one. I can source some NOS 6F6GT (straight glass) at a reasonable price & note it is 0.7aH, well within specs for amp. Will have to wait on that though, broke right now

Does anyone have any comment/problem with the 6AG6G? wrt higher current draw. Seems a bit borderline, dont want to damage the transformers.
Here is the link for my original inspiration to get this amp:   https://www.aradiogurl.net/hhjournal/2016/06/01/gemtune-pa1502a-appj-headphone-tube-amp-mod/
And my grandaughter chilling to the Gemtune

And my grandaughter chilling to the Gemtune:


----------



## baronbeehive (Jul 12, 2017)

DavidK35 said:


> Interesting you mention 6F6C tubes, I missed that one........
> 
> ....



If you do want to get them I have a NOS matched pair, PM me if you want. I just found out they don't work on my EL84 amp. The base is loose on one, only because they adapters I used are so stiff it went loose putting it in place, otherwise fine.




DavidK35 said:


> ....
> 
> And my grandaughter chilling to the Gemtune
> 
> ....



Lovely, I think she approves of your choice!

Edit:
Yes that link was the inspiration for this thread I believe.


----------



## DavidK35

Anyone tried the 6K6G/GT? Dirt cheap, especially the G. Same pinout & only 0.4 heater amp draw (similar to the 6V6).


----------



## CZ4A

DavidK35 said:


> Anyone tried the 6K6G/GT? Dirt cheap, especially the G. Same pinout & only 0.4 heater amp draw (similar to the 6V6).



I've tried a couple of different pairs 6K6s a while ago (Sylvania 6K6G and GE 6K6GT) and I don't remember being that impressed with them. I can give 'em another listen compared to my NOS Tung-Sol 6V6GTs tonight or tomorrow.

I think the best budget NOS power tube for the APPJ is the 6W6GT. They're cheap, plentiful, linear, and pretty darn nice-sounding. They do have a whopping 1.2A power draw but that's just within spec.


----------



## DavidK35

That's good to know, thanks for that, I will order them next week. Please let me know how your listening tests go.


----------



## CZ4A

I I had a quick listing test between the vintage black glass Tung-Sol 6V6GT and the Sylvania 6K6G. The headphones were HE-500 and the preamp tube was a Raytheon 12DT7. The coupling caps are WIMA MKP4 0.47uf.

I'm no good at describing sound but I found the 6K6G tubes to be too smooth for my liking. The bass lacked punch and overall I felt they weren't as lively or detailed as the 6V6GT tubes.


----------



## Maxx134

DavidK35 said:


> Anyone tried the 6K6G/GT?


Yep they cheap and not bad, but they started to spark with demanding passages so I pulled them out quick.

Average sound no where as good as a 6V6 type..


----------



## Maxx134 (Jul 21, 2017)

My top most transparent combo is:

Driver tube:
*12SL7 SILVER ROUND PLATE *
No matter the brand they same construction used with various brand.

Get the adapter as it is really worth upgrading to the larger bottle 12SL7 type tube.

Power tubes:
*the 6F6, specifically the Russian 6Ф6С / 6F6C Cobra... 
(Thanks to member "Kryl007" for that recommendation.)
Best transparency of 6F6 type and cheaper too..

*


----------



## Hippocamp

Picked up this amp used. First impressions are very positive! Black background. Nice soundstage. Excellent clarity.

It came with a set of extra tubes (a pair of JJs and a Mullard). 

My plan is to use this mostly with my Beyer DT1990 pros, which are fantastic (great bass, soundstage, and awesome detail retrieval) but just a little dry in the treble.

Any suggestions for a tube combination that would bring some liquidity to the highs?


----------



## baronbeehive (Jul 21, 2017)

Hippocamp said:


> Picked up this amp used. First impressions are very positive! Black background. Nice soundstage. Excellent clarity.
> 
> It came with a set of extra tubes (a pair of JJs and a Mullard).
> 
> ...



I can only comment on the driver tube, as I have the other, speaker APPJ which has EL84 power tubes, but for liquid highs the Tungsol 12SL7 is amazing as I said a few posts ago. You would need a 12Ax7 to 12SL7 adapter though. Alternatively you could try the 12AX7 substitute, the TS 5751 which is slightly earthier and more live sounding but just as liquid in the trebles, and fits straight in. Also it's easier to get hold of. The thing with the TS's is that they are very liquid sounding but some people don't like them because of their sweetness, others love them however! The other thing is that for some the treble is slightly rolled off, I don't find this but then I don't like very sharp sounding treble.

Also any silver plate 12SL7 as Maxx134 said a few posts ago would be good, such as a GE.

Incidently I find the JJ ECC83S driver tube to be very smooth sounding as well for a new issue tube, great soundstage and very lively bass.


----------



## Maxx134

DavidK35 said:


> Gemtune Amp Part 1
> 
> Got my amp last week & been burning in tubes & auditioning. Still waiting for adaaptor & 12SL7/12SN7 tubes...


 seemed to have overlooked your post.. 
Very nice!
Yes best driver tubes are *12*SL7




DavidK35 said:


> I think I am the first in this thread to use the 6BG6 G series tubes that have the external wire & cap with suitable adaptor....


Wow big monster tubes!!
Haha nice!




DavidK35 said:


> So far I think this is the best sounding head amp I have tied so far (#6) so cannot wait to roll some other tubes. .


Wow you tried 6 other amps, care to say which?
This amp modded is pretty high up in level so understandable .




DavidK35 said:


> Coming are the 6SN7 & 6SL7 drivers + 6AG6G/EL33 power tubes.


*DO NOT USE 6SN7 & 6SL7 tubes for driver.!!!
They require adapter which gets hot due to cheap resistor inside...
*
Use the 12V versions:
12SL7 & 12SN7.





DavidK35 said:


> I ordered my amp without tubes for $159.00 + $30 fedex 5 day.


Wow dirt cheap!




DavidK35 said:


> Time will tell if the 6BG6 proves better or not than the 6AG6G types & I may also try the 6L6G types but they are a bit pricey.


Do not bother with the 6L6 type.
Since the bias is not optimal for them,
they end sounding a bitt vague and distant, and not as vivid as the 6F6 type.




DavidK35 said:


>


Intimidating power tubes!
Ha


----------



## DavidK35

To answer your questions:

1) post was a mistake should have read 12SL/N7 not 6SL/N7

2) 6 amps in total, the other 5 were:

    INDEED 12v tube type (open frame) with 6211A tube. Failed after 2 years. Ran very hot too.
    CTH (compact tube hybrid) various tubes. Too dry & sibilant for me.
    CIVILIAN 6N2 + FU32 (6AX7 + 32 NOS tubes). Ran extremely hot. OK but heat was issue for me
    LITTLE BEAR P8 (1 x 6AS7G + 2 x 6SN7 NOS with adaptors). Very good with the 6SN7's (new issue Tung Sol). 
    BREEZE E200 (2 x 6C8G + adaptors, 1 x 7F7 + adaptor or 6211A, all NOS.) Still have it but definitely not as good as
    the Gemtune even though the transformers are much bigger, + size & weight much more. The circuit design must be
    superior IMO. The LB P8 ranks #2 but is bested by the Gemtune.


----------



## Maxx134

Wait untill you do the upgrades to your unit...


----------



## Hippocamp

Maxx134 said:


> Yes best driver tubes are *12*SL7



Will 12SN7 tubes perform similarly? Seem to be a lot more of that type available than 12SL7.


----------



## Maxx134

No,
 the original circuit cost for an 12 ax7 output type ,
and so you need an 12SL7 type for the similar mu gain.
 you don't want a tube that sounds duller or not as Lively


----------



## baronbeehive

Maxx134 said:


> Wait untill you do the upgrades to your unit...



He he.... why would anyone not want to do that.....!!
Easy to do on this unit, only problem the pads are tiny and easily disturbed, these are the repairs I had to make:



 



Hippocamp said:


> Will 12SN7 tubes perform similarly? Seem to be a lot more of that type available than 12SL7.



Did you manage to pick up any TS5751's, it's a matter of luck if you can find any 12SL7's atm! I have the 5751's in mine and don't really need anything else.


----------



## Maxx134 (Aug 3, 2017)

5751 type is prob the best 9pin i ever tried...
Edit or at least the most resolving.
There is always a stand out tube in every type like the 180cc and e80cc types which had a bit more Soundstage at trade off of liveiness..

For a driver stage, better to have the most resolving tube, like the resolving 5751.
Best for me yet was the 12SL7 8pin with adapter.

You can gain back any Soundstage lost with power tubes choice anyways.
The 6L6 on this amp does it with largest Soundstage while sounding refined,
But at a trade off of sounding more laid back.

The 6v6 are most balanced ,
but for me the 6f6 was most resolving.


----------



## Hippocamp

baronbeehive said:


> He he.... why would anyone not want to do that.....!!
> Easy to do on this unit, only problem the pads are tiny and easily disturbed, these are the repairs I had to make:
> 
> 
> ...



Yep. Just my TS 5751 arrived a few days ago. Haven't had a chance yet to give it a long listen but initial impressions are good.


----------



## Pratt99 (Aug 4, 2017)

baronbeehive said:


> I can only comment on the driver tube, as I have the other, speaker APPJ which has EL84 power tubes, but for liquid highs the Tungsol 12SL7 is amazing as I said a few posts ago. You would need a 12Ax7 to 12SL7 adapter though. Alternatively you could try the 12AX7 substitute, the TS 5751 which is slightly earthier and more live sounding but just as liquid in the trebles, and fits straight in. Also it's easier to get hold of. The thing with the TS's is that they are very liquid sounding but some people don't like them because of their sweetness, others love them however! The other thing is that for some the treble is slightly rolled off, I don't find this but then I don't like very sharp sounding treble.
> 
> Also any silver plate 12SL7 as Maxx134 said a few posts ago would be good, such as a GE.
> 
> Incidently I find the JJ ECC83S driver tube to be very smooth sounding as well for a new issue tube, great soundstage and very lively bass.



My setup is Bifrost 4490 + APPJPA1502a(with Jantzen Superior Z-cap)+HD600. The only power tube I have is JJ 6v6s. Initially I tried 12AT7 mullard, JJ 12au7 and 12au7 RCA clear top and was not happy. Thanks to @Maxx and @baronbeehive suggestions, I purchased GE 12SL7(silver round plate) , Tungsol 12SL7, Tungsol 5751(vintage) and JJ 12AX7. With my setup, IMO the GE 12SL7 treble sounds just a tiny bit harsh(probably due to HD600s sound signature), however the Tungsol 12SL7 is perfect, followed by Tungsol 5751. Also as @baronbeehive said the JJ12ax7(still burning in) sounds fantastic with this setup.


----------



## baronbeehive

Pratt99 said:


> My setup is Bifrost 4490 + APPJPA1502a(with Jantzen Superior Z-cap)+HD600. The only power tube I have is JJ 6v6s. Initially I tried 12AT7 mullard, JJ 12au7 and 12au7 RCA clear top and was not happy. Thanks to @Maxx and @baronbeehive suggestions, I purchased GE 12SL7(silver round plate) , Tungsol 12SL7, Tungsol 5751(vintage) and JJ 12AX7. With my setup, IMO the GE 12SL7 treble sounds just a tiny bit harsh(probably due to HD600s sound signature), however the Tungsol 12SL7 is perfect, followed by Tungsol 5751. Also as @baronbeehive said the JJ12ax7(still burning in) sounds fantastic with this setup.



That's great info! You're probably right about the HD600 sound signature, I know because I had one. Yes, I was quite surprised at how good the JJ new issue ECC83S's are.
Sounds like you have a great set up there.
Now you need good power tubes, so follow Maxx134's suggestions there.


----------



## Hippocamp

Another novice modding question...

The original electrolytic and coupling caps are quite securely attached to the board, with no gap at the bottom. What is the technique for desoldering and removing them? Is it necessary to remove the board entirely?

Thanks!


----------



## baronbeehive

Hippocamp said:


> Another novice modding question...
> 
> The original electrolytic and coupling caps are quite securely attached to the board, with no gap at the bottom. What is the technique for desoldering and removing them? Is it necessary to remove the board entirely?
> 
> Thanks!



Simple! Remove the top of the chassis, you have removed the bottom, then find the ends of the relevant caps and desolder.
If you haven't done any soldering you could look at a basic soldering video on YouTube of which there are many. The technique is to add solder to the tip of the soldering iron , then touch the solder joint and add a bit more solder. This transfers the heat to the joint. As you are doing this, very gently pull the component out from the other side. If you don't follow this fairly precisely you could pull the tiny silver pads off which make electrical contact, which several of us have done, including me lol, then you have to repair it which you don't really want to do!!Don't touch the joint for more than 2 or 3 seconds because it will overheat and the pad will come off, similarly don't pull too hard without enough heat or the pad will again come off, simple really.

*Finally always allow 5 minutes or so after switching off the amp for the current to discharge before touching anything inside because if you don't you could be electricuted....and...killed! That's very important so please make sure you know what you are doing .*

Hope that helps.


----------



## DavidK35

Gemtunes amp part 2.

The Good the Bad and the Unexpected

First with the bad. I lost one channel & through a process of elimination concluded its a fault
with the amp. This is a quality control issue & am not happy about it & letting you know if you buy one
it could develop the same problem. But this amp sounds so good I decided to persevere with it & kill 2 birds with one stone. So it is away for repair atm & I am having fitted the 2 capacitors. I selected 2 x Russian  matched pair
0.47uF 400v K40Y-9 PIO.


 Before the amp defaulted I did some listening tests with:

12SL7, 12SN7 & 6211A drivers (westinghouse, rca, rca)
EL33, 6BG6GA power tubes (2 x mullard, 1 x westinghouse, 1 x rca) all NOS
In essence I found my expectation bias was totally contradicted by the unexpected results.
After all tubes were burnt in  I found the best driver to be the little 6211A. It pretty much wiped the floor
with the 12SL7 and although the 12SN7 performed better, the treble was distinctly inferior. Words that came to 
mind at the time were splashy/tizzy/smudgy sss's sibilant. The 6211A was however crystal clear. 
The EL33's suprised me too, rich full bass & mids but inferior treble as above, compared to the 6BG6GA's.
Not the result I was expecting, far from it, but that's what my hearing told me.

As a side note comparing the 6211 with the 7F7 as drivers in another amp the 7F7 outperformed (better treble) the 6211A (same tube). I am guessing with the Gemtunes its to do with bias and/or circuit design?. Not my expertise.
In light of this I have ordered a 14F7 adaptor to be included in my 3rd & last set of listening tests.
Part 3 will include: 14F7/14AF7/14N7 & 6211A drivers & 6BG6G, 6F6GT, 6K6G, 6V6GT power tubes.
All these are 0.9a or less & not going to try any of the 1.2a tubes even though I bought some because I dont want to risk any further problems.


----------



## baronbeehive (Aug 18, 2017)

DavidK35 said:


> Gemtunes amp part 2.
> 
> The Good the Bad and the Unexpected
> 
> ...



All interesting information!

Your caps choice also looks interesting, should be good, you will notice a definite improvement there.

Re: your tube experiments, I agree with Maxx, the 12SL7 is the best tube I have, along with the 5751. I think the type of 12SL7 will make a difference, I know they are difficult to come by but I managed recently to acquire another TS 12SL7 branded as Hytron which has been on ebay for some time and ignored. This time there is no static noise it is very quiet and does not sound anything like you have found with your choice of 12SL7. I actually like the 6V version of the RCA 12SL7 but I can see some might not, and the circuit will definitely affect the sound, for one thing the specific distortion generated by the Gemtune circuit will create a different sound with a given cap to another circuit with different distortion levels.

Interested to hear the results of your final listening tests, and also if you can let us know the cause of the problem with your amp, such a cheap amp probably doesn't have exhaustive quality control checks and the components, and especially the board which is not very sturdy, can be a problem such as when modding as people have found.

Edit:
You made a good choice keeping your amp, mine is going nowhere either lol !


----------



## DavidK35

Update: 
There was a connection problem with the driver socket & has been resoldered, so that kinda
nullifies my earlier results for the drivers. When I get it back I will redo the driver tube tests.
Also there was insufficient room for the PIO caps & going ahead with Auricaps instead.

Here is a very interesting link reviewing the different caps:

http://www.laventure.net/tourist/caps.htm


----------



## hackstu

Does the pa1502a, needed moddeing due to bad build quality???

The 'green' circuit board version, is this the 2015 version as being sold by doukmail on ebay??


----------



## Makiah S (Aug 23, 2017)

Thinking about grabbing this for some modding experience, Oh this is the Headphone amp...

Is it better to purchase this model or the Speaker Model?


----------



## Maxx134

I am going to take a guess that the output would be very similar on either amp,
But the tube rolling may be more with the headphones model, which is the newer model.

I therefore would choose the amp Based on what output tubes you like.


----------



## MrSlim

baronbeehive said:


> Simple! Remove the top of the chassis, you have removed the bottom, then find the ends of the relevant caps and desolder.
> If you haven't done any soldering you could look at a basic soldering video on YouTube of which there are many. The technique is to add solder to the tip of the soldering iron , then touch the solder joint and add a bit more solder. This transfers the heat to the joint. As you are doing this, very gently pull the component out from the other side. If you don't follow this fairly precisely you could pull the tiny silver pads off which make electrical contact, which several of us have done, including me lol, then you have to repair it which you don't really want to do!!Don't touch the joint for more than 2 or 3 seconds because it will overheat and the pad will come off, similarly don't pull too hard without enough heat or the pad will again come off, simple really.
> 
> *Finally always allow 5 minutes or so after switching off the amp for the current to discharge before touching anything inside because if you don't you could be electricuted....and...killed! That's very important so please make sure you know what you are doing .*
> ...



A "Solder Vac" is your friend. I would  never  attempt any component replacements without it. https://www.amazon.com/High-Vacuum-...?srs=4905462011&ie=UTF8&qid=1503758304&sr=8-3 is my favorite as far as manual options are concerned  (and I've  used a few). 
Here are a few more tips:
Heat the joint until the solder is fluid and then while the iron is still on the joint, suck up the solder with the solder vac. If the hole doesn't look completely  clean,  add solder and repeat the process.
Once the hole is clear, the lead may still be connected to the through-hole metal (unless it is a single sided board) due to the capillary effect. At this point, apply heat to the joint again and use the tip of the iron to push the lead away. You should feel the lead pull away from the side  of the hole. Repeat this step until the lead is loose in the hole and you can wiggle the component you are removing. 
I have used this technique many times and have not had a damaged pad in a very long time.


----------



## baronbeehive (Aug 26, 2017)

hackstu said:


> Does the pa1502a, needed moddeing due to bad build quality???
> 
> The 'green' circuit board version, is this the 2015 version as being sold by doukmail on ebay??



No, it needs modding to bring out it's fantastic sound quality, actually it is very good without the mods!



Mshenay said:


> Thinking about grabbing this for some modding experience, Oh this is the Headphone amp...
> 
> Is it better to purchase this model or the Speaker Model?



It's easy to mod but care is necessary. I agree with Maxx that either is good and both probably have similarities in sound, we have been in communication over this and our findings on sound seem similar, and we have done the mods using similar components.



MrSlim said:


> A "Solder Vac" is your friend. I would  never  attempt any component replacements without it. https://www.amazon.com/High-Vacuum-...?srs=4905462011&ie=UTF8&qid=1503758304&sr=8-3 is my favorite as far as manual options are concerned  (and I've  used a few).
> Here are a few more tips:
> Heat the joint until the solder is fluid and then while the iron is still on the joint, suck up the solder with the solder vac. If the hole doesn't look completely  clean,  add solder and repeat the process.
> Once the hole is clear, the lead may still be connected to the through-hole metal (unless it is a single sided board) due to the capillary effect. At this point, apply heat to the joint again and use the tip of the iron to push the lead away. You should feel the lead pull away from the side  of the hole. Repeat this step until the lead is loose in the hole and you can wiggle the component you are removing.
> I have used this technique many times and have not had a damaged pad in a very long time.



Yes, I completely agree with you about this and was trying to obtain one myself for modding because it simplifies a quite complicated process, I would definitely use one if I was modding again!!

Thanks for the useful information.


----------



## MrSlim

Mshenay said:


> Thinking about grabbing this for some modding experience, Oh this is the Headphone amp...
> 
> Is it better to purchase this model or the Speaker Model?



I did the work on David's amp(headphone), and it is a nicely designed unit. If you want it for Modding experience, I might suggest something else, since the Modding you can do on it is really limited to the coupling and cathode capacitors. The rest of the amp circuit is Surface Mount, and the Power supply is Switched mode which I wouldn't touch.  Also, there isn't a lot of space for adding boutique caps, unless you are willing to modify the case as well (as several posters have done)..


----------



## Makiah S

MrSlim said:


> I did the work on David's amp(headphone), and it is a nicely designed unit. If you want it for Modding experience, I might suggest something else, since the Modding you can do on it is really limited to the coupling and cathode capacitors. The rest of the amp circuit is Surface Mount, and the Power supply is Switched mode which I wouldn't touch.  Also, there isn't a lot of space for adding boutique caps, unless you are willing to modify the case as well (as several posters have done)..



Well @Maxx134 recommend putting in larger boutique caps, so those plus the Coupling and Cathod Capacitors should be a good place to start! I have 0 soddering experience, and this won't be in any way my primary driver, I'll most likely do a lot of listening with my SuperLUX HD 668B... just in case I screw something up I'm only out a $40 pair of headphones, for getting my feet wet I'm hoping if I can successfully perform the upgrades it'll be worth while improvement over what I have now, 

I think when I reach the point where the chassis needs to be modded, I may just build my first kit. This amp is really for perspective and to serve as a starting point

That said, I did copy the JJ 6v6 an TungSol 12sn7 Tube recommendation I saw posted on here earlier! Going to do my BEST not to upgrade the tubes till I've completed my internal modification!


----------



## baronbeehive (Aug 27, 2017)

MrSlim said:


> I did the work on David's amp(headphone), and it is a nicely designed unit. If you want it for Modding experience, I might suggest something else, since the Modding you can do on it is really limited to the coupling and cathode capacitors. The rest of the amp circuit is Surface Mount, and the Power supply is Switched mode which I wouldn't touch.  Also, there isn't a lot of space for adding boutique caps, unless you are willing to modify the case as well (as several posters have done)..



I misunderstood your earlier post about desolder vacs, I  thought you were referring to the electric continuous vacuum desoldering gear which heats up and desolders all in one continuous operation. I found it difficult to get the hang of heating up the joint with the iron and using the manual vac at one and the same time! Have you used the electric one, it looks so easy this way, and I would get one of these if I had to do a whole lot of desoldering again.


----------



## Makiah S

Maxx134 said:


> 5751 type is prob the best 9pin i ever tried...
> Edit or at least the most resolving.
> There is always a stand out tube in every type like the 180cc and e80cc types which had a bit more Soundstage at trade off of liveiness..
> 
> ...



I couldn't resist... I went ahead and grabbed the Slyvania 6w6GTs an bid on two of the *6F6's I'm curious to see how they compare to the JJs I got from Amazon. Pairing with a TungSol 12sn7 *


----------



## MrSlim

baronbeehive said:


> I misunderstood your earlier post about desolder vacs, I  thought you were referring to the electric continuous vacuum desoldering gear which heats up and desolders all in one continuous operation. I found it difficult to get the hang of heating up the joint with the iron and using the manual vac at one and the same time! Have you used the electric one, it looks so easy this way, and I would get one of these if I had to do a whole lot of desoldering again.



No, I haven't used one of the electric ones.  I learned how to use the manual "solder sucker" years ago, and have just stuck with it.  I don't do a lot of "rework" so the manual one has been good enough for me. I've been debating buying a hot air SMD station to make it easier to do SMD work, but I'm not sure if I can justify it yet.


----------



## Maxx134

MrSlim said:


> I did the work on David's amp(headphone), and it is a nicely designed unit. If you want it for Modding experience, I might suggest something else, since the Modding you can do on it is really limited to the coupling and cathode capacitors


This is precisely why I would recommend this amp for beginners,
Because of so little to do, and so little needs to he done.

I specifically DO NOT recomended ANYONE wasting their hard earned money on any kit like a crack amp.
You get alot of headaches and waste alot of money that way..


Reverse engineering and upgrading on already well designed units is optimal, IMHO.

ALL commercial tube amps, no matter how expensive,
In order to be competitive, they will ALWAYS have non-optimal coupling of stages.
Simply because most will not use interstage Transformers,
And high quality caps for coupling are expensive.

The cheap alternative for most, is to get away with high voltage wima caps or other cheap caps as long as they high voltage rated they will sound better.
It's just smart business for them.

So no matter how expensive the "tube"  amp is, it will be compromised in same key areas of coupling,
 and also tube supply demands, with newer Solid state solutions like implementation of CCS . (Speedball lingo for crack amp)

The only time you are forced to learn is either when something breaks, or something you want to change.



baronbeehive said:


> I found it difficult to get the hang of heating up the joint with the iron and using the manual vac at one and the same time


Yeah I have a real cheap one from ebay does the trick, but not really need it most time.



Mshenay said:


> Pairing with a TungSol 12sn7


You will need a 9pin to 6pin adapter for that, and it has to be a 12v, not a 6v one.


----------



## Makiah S

Maxx134 said:


> This is precisely why I would recommend this amp for beginners,
> Because of so little to do, and so little needs to he done.
> 
> I specifically DO NOT recomended ANYONE wasting their hard earned money on any kit like a crack amp.
> ...



Yea modding this little guy with some basic upgrades seemed like a smart idea to me too! I'll eventually waste my money building some other kits, just not now 

Hmm well I got this
http://www.ebay.com/itm/1pc-Gold-12...e=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

and this

http://www.ebay.com/itm/Tung-Sol-12...e=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

The adapter is an Octal 12SL7/SN7 to 9 Pin 12AX7 and it's rated for 12.6V

the Tube is a 12SL7 and it's an octal... for Drivers I'm just hoping the 6F6, 6W6GT and 6V6 plug into the power sockets without the need for an adapter. I should have everything I need or am I missing an adapter?


----------



## Maxx134

Mshenay said:


> the Tube is a 12SL7 and it's an octal... for Drivers I'm just hoping the 6F6, 6W6GT and 6V6 plug into the power sockets without the need for an adapter. I should have everything I need or am I missing an adapter?


That is perfect.
Also the unit takes many tube variants , 

 
but just need to be gentle with sockets.


----------



## Maxx134

Really was alot of fun trying different power tubes.

Its quite amazing looking at such a tiny amp with big tubes!


----------



## Makiah S (Aug 27, 2017)

OOOH Yea I forget I wanted to get some Socket Savers!!! Thank you!

I heard they've cracked on some people so I might as well anticipate and prevent that early on, any recommendations? Also what are some better sockets to upgrade to

These seem to be 8pin to 8pin, and the 6V6 seem to be 4pin sockets, would it work

http://www.ebay.com/itm/1-Octal-Gol...d=282369339088&_trksid=p2047675.c100011.m1850


----------



## Maxx134

I tried socket savers but the one i got on ebay was just too cheap and too tight.

You don't want to have to place so much pressure on socket yet the socket savers didn't work for me.

Once I  settle on the big power tubes I only roll the center driver tube.

I would not worry about socket savers for the power tubes as also it looks too tall.


----------



## baronbeehive

Maxx134 said:


> I tried socket savers but the one i got on ebay was just too cheap and too tight.
> 
> You don't want to have to place so much pressure on socket yet the socket savers didn't work for me.
> 
> ...



I also don't think socket savers are a good idea, if you keep changing tubes in the socket saver it is so tight that you have to keep a firm grip to stop it moving about in the socket as you remove the tube so I think it is best  to gently remove the tubes in the original socket.


----------



## Makiah S

Good to know! Input from you both has been duly noted


----------



## CZ4A

hackstu said:


> Does the pa1502a, needed moddeing due to bad build quality???



All the modding I've seen of this amp have been to improve the sound signature, not for repair or reliability reasons.

For PA1502A users who've experienced failures, do you happen to know what failed and/or have any pictures of obviously failed components, like bad caps?


----------



## Hippocamp

MrSlim said:


> A "Solder Vac" is your friend. I would  never  attempt any component replacements without it. https://www.amazon.com/High-Vacuum-...?srs=4905462011&ie=UTF8&qid=1503758304&sr=8-3 is my favorite as far as manual options are concerned  (and I've  used a few).
> Here are a few more tips:
> Heat the joint until the solder is fluid and then while the iron is still on the joint, suck up the solder with the solder vac. If the hole doesn't look completely  clean,  add solder and repeat the process.
> Once the hole is clear, the lead may still be connected to the through-hole metal (unless it is a single sided board) due to the capillary effect. At this point, apply heat to the joint again and use the tip of the iron to push the lead away. You should feel the lead pull away from the side  of the hole. Repeat this step until the lead is loose in the hole and you can wiggle the component you are removing.
> I have used this technique many times and have not had a damaged pad in a very long time.



Great tip, thanks.  Still waiting on my caps -- backordered.

Have been practicing on some old, dead equipment. I found that "chipquick" helps a lot. Keeps the solder molten long enough to get the solder sucker tip in place.


----------



## Makiah S

Hippocamp said:


> Great tip, thanks.  Still waiting on my caps -- backordered.
> 
> Have been *practicing on some old, dead equipment*. I found that "chipquick" helps a lot. Keeps the solder molten long enough to get the solder sucker tip in place.



that's an excellent idea, thank you for that tip


----------



## Makiah S

@Maxx134 and others

I got two 6w6GT Sylvania's but the pin out's are different? Which should I keep and which do I need to exchange or should I not use either one


----------



## CZ4A

Mshenay said:


> @Maxx134 and others
> 
> I got two 6w6GT Sylvania's but the pin out's are different? Which should I keep and which do I need to exchange or should I not use either one



6W6GT has the same pin-out as the 6V6GT. There's actually only 6 active pins on a 6V6GT/6W6GT (7 on a metal can 6V6, the #1 pin attaches to the shell for grounding). The extra pin on the right tube is not connected to anything. You should be good to go.


----------



## Makiah S

Cool Beans! That's great to know. I might try them out today if I have time at work. My amp is stationed there until my move is completed. I should update this thread with a picture so far, but my DM actually swang into my store yesterday and found my APPJ PA1502A in the back room running and asked me what it was... her response was "sounds better than beats" so there's that. I thankfully was not attending to the system at the time and didn't get fired for having it running unattended either xD


----------



## baronbeehive (Sep 2, 2017)

Mshenay said:


> @Maxx134 and others
> 
> I got two 6w6GT Sylvania's but the pin out's are different? Which should I keep and which do I need to exchange or should I not use either one



That's strange, according to the datasheet: http://www.nj7p.info/Tubes/PDFs/Frank/093-GE/6W6GT.pdf

the pin that is missing, pin 3, should be plugged in to the plate, so that tube appears to be the wrong tube.

Edit: Sorry I didn't see CZ4A's post, forget what I said I was reading the diagram upside down lol.


----------



## Makiah S

Maxx134 said:


> Yes they are the same exact points posted in thread by others,
> but I will post again:
> 
> 
> ...





Maxx134 said:


> Here is a close up of the Electrolytics and the film caps soldered on the leads.
> 
> For the square coupling cap replacement,
> I used silver wire in the holes to bring wires to that area for big coupling caps..
> ...



Couple more questions, can I use a ECC88 or 6922 Tube? I've got an extra I oringally purchased for my Ember and the MCTH... but I opt'd again'st the MCTH and got this instead, I'm hoping I can still use the ECC88 6022 Simens I bought lol! As it'll be the only tube I have 2 of, 

Secondly I'm trying to finalize a part's list for this bad boi, I'm thinking of just starting with Nichicon FW caps 1000uF 25vdc and wima 0.47 uf 400v, to replace what's highlighted in Red on that first pic and depicted in the second 

My other question is what's the difference between the 250v and 400v Wima .47 uF's?


----------



## CZ4A

Mshenay said:


> Couple more questions, can I use a ECC88 or 6922 Tube? I've got an extra I oringally purchased for my Ember and the MCTH... but I opt'd again'st the MCTH and got this instead, I'm hoping I can still use the ECC88 6022 Simens I bought lol! As it'll be the only tube I have 2 of



The APPJ's preamp socket supplies 12.6V, which will severely reduce the lifespan of a 6.3V tube like the 6DJ8 because its heaters will run way past spec. In the APPJ you have to use either a dual voltage tube like the 12AT7/12AU7/12AX7 or a 12V version of a 6V tube in the preamp socket. If you have your heart set on a 6DJ8-type for the APPJ your options are limited to the extremely rare Sylvania 12DJ8 or the less rare Amperex USA 8416 (which is their 7308 with 12V heaters).


----------



## Makiah S

Yea I'm ok without running a 6v tube like the 6992, good info too thank you!


----------



## baronbeehive (Sep 3, 2017)

CZ4A said:


> All the modding I've seen of this amp have been to improve the sound signature, not for repair or reliability reasons.
> 
> For PA1502A users who've experienced failures, do you happen to know what failed and/or have any pictures of obviously failed components, like bad caps?



Good idea, I've had mine though for 5 years with no problems so I don't think we need assume that there is a problem with the APPJ. I would think the most likely source of problems would be the tube sockets,  DavidK35 found this out, but they appear well soldered, however the board would not be able to put up with too much mis-treatment. I had one of the wires break off but this was due to opening and closing the top, so be aware of this if you are modding.



Mshenay said:


> ....
> 
> Secondly I'm trying to finalize a part's list for this bad boi, I'm thinking of just starting with Nichicon FW caps 1000uF 25vdc and wima 0.47 uf 400v, to replace what's highlighted in Red on that first pic and depicted in the second
> 
> My other question is what's the difference between the 250v and 400v Wima .47 uF's?



....150v....sorry, what you should aim for is to match up voltage of the caps with the PSU voltage, in this case 250v should be alright however you can go higher, indeed often it is a good idea to apply a 3x rule so that if, for example the PSU supplies 100v, then the Caps can go to 300v for an adequate safety margin. The problem is that manufacturers often use what they have lying around and if, for example there are 1000uF 100v caps      inside, the circuit may not be using all this extra capacity, it may only require, say 50uF and 25v.

Edit:
BTW, Cardas solder is very good to use ad easy to work with for your mods.


----------



## Makiah S

Yea I know to be careful with stuff, I've destroyed a fair amount of electronics over the years and I've had to have friends solder stuff back together 

Here's my question, if I destroy a Trace on the board how do I fix it and number 2 what is a good soldering iron to start with?


----------



## baronbeehive (Sep 3, 2017)

Mshenay said:


> Yea I know to be careful with stuff, I've destroyed a fair amount of electronics over the years and I've had to have friends solder stuff back together
> 
> Here's my question, if I destroy a Trace on the board how do I fix it and number 2 what is a good soldering iron to start with?



Ha ha, I know the feeling!

If you trash a pad, the proper way is to repair it, either glue it back with epoxy or make another pad from copper  and solder that back, but frankly that's tricky so plan B is to find a way of making electrical contact with the the solder joint where the pad was and the rest of the trace which that pad belongs to, either by using wire or by scraping back to expose the trace. If you trash a trace that's tricky, so don't do it lol!

You need a 30-40 watt iron, enough to provide the heat to solder whatever components you will be dealing with but not too hot for the job you are doing, as the components of the APPJ are tiny I would use no more than 30 watts.

Good luck!


----------



## Makiah S

baronbeehive said:


> Ha ha, I know the feeling!
> 
> If you trash a pad, the proper way is to repair it, either glue it back with epoxy or make another pad from copper  and solder that back, but frankly that's tricky so plan B is to find a way of making electrical contact with the the solder joint where the pad was and the rest of the trace which that pad belongs to,* either by using wire or by scraping back to expose the trace.* If you trash a trace that's tricky, so don't do it lol!
> 
> ...



That's what I figured, Should I purchase two solderings irons then? one for bigger projects another for smaller, I guess for now I can just start with a little one

I've also got a wood desk I intend to work on, what would be a nice cheap material to put on the floor so I can avoid shorts/shocks or should I have something metal near by to ground my self


----------



## baronbeehive

Mshenay said:


> That's what I figured, Should I purchase two solderings irons then? one for bigger projects another for smaller, I guess for now I can just start with a little one
> 
> I've also got a wood desk I intend to work on, what would be a nice cheap material to put on the floor so I can avoid shorts/shocks or should I have something metal near by to ground my self



30 watt is the standard for circuit board work but some people prefer 40 watt. Normally 30 watts is right and then you adjust the heat going to the board components with the tip, small tip for small components, bigger for bigger components otherwise it will be difficult to heat the component correctly, the solder flow should work well in 2-3 seconds, no more.

For the actual work you can get an anti static grounding matt like this: https://www.amazon.co.uk/Desktop-St...id=1447780704&sr=8-3&keywords=anti+static+mat

And for yourself an anti static wrist band such as this: https://www.amazon.co.uk/eBoot-Anti...4478008&sr=1-1&keywords=anti+static+wristband

Also surgeons gloves or something like this are a good idea: https://www.amazon.co.uk/Anti-Stati...1504478104&sr=1-2&keywords=anti+static+gloves


----------



## Makiah S

Well I have a HUGE Stash of rubber latex gloves I used in the past for repairs and gaming, I've also added those two products to my cart! I like the anti static mat and wrist band


----------



## baronbeehive

Mshenay said:


> Well I have a HUGE Stash of rubber latex gloves I used in the past for repairs and gaming, I've also added those two products to my cart! I like the anti static mat and wrist band



So just one soldering iron, and  you're away........... oh and don't forget safety precautions mentioned earlier, allow time for your caps to discharge after switching off and before you start working on it. I usually switch off and leave it off overnight and then don't switch it on again until I've finished working on the amp, that way there can be no danger.


----------



## Makiah S (Sep 6, 2017)

baronbeehive said:


> So just one soldering iron, and  you're away........... oh and don't forget safety precautions mentioned earlier, allow time for your caps to discharge after switching off and before you start working on it. I usually switch off and leave it off overnight and then don't switch it on again until I've finished working on the amp, that way there can be no danger.



Excellent idea! Let me ask though, what temperature is best to work with on an amp this small, are there any additional tips for the Weller that would simplify this job for me? I've actually decided to save $2 and grab a Hakko 888D-23BY but the original question remains, A few of you recommend a solder or de solder pump? Any recommendations on what to use for modding the APPJ pa1502a, is there a desoldering pump/tip I can use with the Hakko or Weller units??

I figured it out, I can just use the Soldering Pencil tip to thin or melt the solder, and wick/pump it away, got a toss away PCB from my instructor today with some stuff I can desolder for pratice

NEXT question, the 12SN7 to 12AX7 Adapter I have is TO big to fit! Which means I need a 9pin Socket Save, any idea on what to use? Is there a specific voltage rating or will it just conduct what ever is plugged in up top, as the adapter won't fit as is. The 9pin socket is too recessed 

I think I'm just going to get one of these and see how it sounds 
http://www.ebay.com/itm/2pc-GOLD-Vi...008249?hash=item2cc03128f9:g:gzMAAOSwH09ZLj0p

Plus an extra just in case


----------



## CZ4A

I noticed an issue with my amp, that sometimes the left channel would not work or play loud static unless the preamp tube was cocked a little bit to the right. It was also more microphonic than I remembered, no matter what tubes I used. I discovered the #8 pin socket needed retensioning, and now the static and weird microphony are gone. I also changed the cathode bypass caps again, this time from Elna Silmic 220uf 25v to Wurth WCAP-PT5H 1000uf 6.3V aluminum polymer caps. The top end came back and clarity is also better, without killing the bass boost the 0.47uf coupling caps provide.



Mshenay said:


> NEXT question, the 12SN7 to 12AX7 Adapter I have is TO big to fit! Which means I need a 9pin Socket Save, any idea on what to use? Is there a specific voltage rating or will it just conduct what ever is plugged in up top, as the adapter won't fit as is. The 9pin socket is too recessed



Can you post a link to the adapter you bought? Even with the 9-pin socket being recessed, I don't have a problem using this adapter as-is:

http://www.ebay.com/itm/1pc-12SN7-1...948306?hash=item2ec9315212:g:BZgAAOSwwbdWLixO


----------



## baronbeehive (Sep 8, 2017)

CZ4A said:


> I noticed an issue with my amp, that sometimes the left channel would not work or play loud static unless the preamp tube was cocked a little bit to the right. It was also more microphonic than I remembered, no matter what tubes I used. I discovered the #8 pin socket needed retensioning, and now the static and weird microphony are gone............



Did you do a continuity check from the newly soldered cap leg on the left channel to the trace and wiggle the leg to see if there is a break in the circuit? If so the soldering needs fixing. The board is quite flexible, not very rigid, and any movement in the socket could affect other points on the board. Also you could find out what each pin is connected to on the right channel socket and check the continuity of the left had socket to see if the contacts are the same on that side, if it is the socket then there will be a poor connection on one of the pins indicated by a break in continuity.

Edit: I don't really see a problem with the amp or its components, surface mount components should not fail, and the amp doesn't get hot so overheating is not a problem, so the mechanical force of changing tubes on the sockets is the most likely cause of failure I would have thought.


----------



## Makiah S

CZ4A said:


> I noticed an issue with my amp, that sometimes the left channel would not work or play loud static unless the preamp tube was cocked a little bit to the right. It was also more microphonic than I remembered, no matter what tubes I used. I discovered the #8 pin socket needed retensioning, and now the static and weird microphony are gone. I also changed the cathode bypass caps again, this time from Elna Silmic 220uf 25v to Wurth WCAP-PT5H 1000uf 6.3V aluminum polymer caps. The top end came back and clarity is also better, without killing the bass boost the 0.47uf coupling caps provide.
> 
> 
> 
> ...




The one I got is much wider than the one you've posted. I guess I'll just get both and see if there's a difference sonic ally [I doub't there will be but I always like to have doubles of everything anyways]


----------



## Miguel Dominguez

I tried the cap upgrade for this amp and got myself into bit of a bind...

Long story short... four gold washers fell out of the bottom of the amp while I was removing screws. I was unable to find the correct places for them (the bottom plate would not sit flush) so I left them out and then reassembled. I blew the fuse when trying to power it back up. Any idea where these washers go and if they would somehow cause a short if not installed? I'm pretty confident that the caps were installed correctly as I've built a few bottlehead kits. Any help would be appreciated!!


----------



## Maxx134

Pics would help, and I myself don't remember any washers...
Also, if you extended the bottom you have to be careful that overtightening the screws will bend the board.


----------



## Miguel Dominguez (Sep 9, 2017)

Ok, figured it out. The 4 gold washers belong between the metal plate on the top side and the pcb. This keeps the metal plate from shorting out the circuit... One would not normally need to remove this metal plate to do the cap mod, it turns out. I fixed that, but wound up blowing another fuse. There is a short somewhere... I'll post some pics in a few.

EDIT:

Pics: https://imgur.com/a/dt2Xt


----------



## baronbeehive (Sep 10, 2017)

Miguel Dominguez said:


> Ok, figured it out. The 4 gold washers belong between the metal plate on the top side and the pcb. This keeps the metal plate from shorting out the circuit... One would not normally need to remove this metal plate to do the cap mod, it turns out. I fixed that, but wound up blowing another fuse. There is a short somewhere... I'll post some pics in a few.
> 
> EDIT:
> 
> Pics: https://imgur.com/a/dt2Xt



Maxx, he could just check one of two things before you come back....

Check:
1 - the ends of the cap legs between R24 and R26, are they touching the top plate when reassembled, if so trim off the ends.
2 - the wires to the transformers have not broken off
3 - I don't know why the bottom plate is not flush,  find out why.

One of the reasons it's quite an easy amp to mod is all the components are easily accessible on the board and it's fairly clear by looking if anything does not look right, for example poor soldering joints or bits of solder left lying around.

Edit: Have you got a pic of the bottom showing your new caps?


----------



## Miguel Dominguez

baronbeehive said:


> Maxx, he could just check one of two things before you come back....
> 
> Check:
> 1 - the ends of the cap legs between R24 and R26, are they touching the top plate when reassembled, if so trim off the ends.
> ...



Yep. See the imgur gallery in post #486. The cap leads are a bit long. I'll go ahead and snip them a bit more, but there seems to be ample space between the top plate and the board once it's screwed on. Not sure if the leads are long enough to have caused a short. The metal plate (the one that covers half the board when viewed from the top) shorting out the entire circuit makes sense since I did not reinstall the washers/risers after turning on the amp after the mod. My question would be... could the amp be dead? Would the blown fuse have prevented any critical damage to the components?


----------



## baronbeehive (Sep 10, 2017)

You may be alright, also there may be a safety cut out but I don't know if there is on this amp.

I would do a continuity check first on the new components you fitted to eliminate this, then also find out the most likely thing the metal plate may have shorted underneath it and go from there. I haven't seen any pics of the topside so can't tell what it might be. I'm a bit surprised that washers would have made much difference to the height of the plate though, I think most likely your mods!

Do you have a multimeter? As you may know I had to rectify a couple of problems on the amp after modding but I checked continuity before I switched everything back on again because I knew that there were 2 suspect connections.

I can't see a pic of the new caps unless this is it:






Oh  sorry I see this is it, it looked like the original caps before the pic was blown up! It all looks fine, the only way you will find out is by testing the circuit as I said unless Maxx can help.


----------



## DavidK35

Gemtunes Amp part 3

Thanks to Mr Slim for repairing & modifying amp with the Auricap capacitors, he does excellent work.
I have to agree with everyone here the change of caps definitely add to the bass without any detriment.
Difference is not night & day but noticable & well worth doing, very happy with this amp.

First I went back to the 12SL7 drivers & gave them another 24 hrs burn in on top of the 3 days they
already received and no change. Do not know what others see in this tube, but for me this came a very long
last in choice of driver. All other testing was done with 6211/14F7/14AF7/14N7. 
4 of these drivers were very very close in performance, the only one that I did not like too much was the 14F7
which I found to be a bit too much in your face & a hair coarser. The other 4 were much closer with the loctals having a very slight edge on the 6211, but would be hard to pick in say a blind test.
I am not going to go into great technical detail but just list my order of preference based on the listening impact
each had.
1) 14AF7
2) 14N7
3) 6211A (GE 5 star black plate, double mica)
4) 6211A (RCA black plate, triple mica)
5) 14F7
Wow the much cheaper GE 5 star slightly outdid the fancy RCA tube. Very suprised.
Unfortunately the 14AF7 died on me after a short time & had no spare. Have ordered more and will retest some
more because it was not long enough of a test. But really any one of those would be fine & dirt cheap too.
Although the branding can vary, as I understand it these loctals are all made by Sylvania.

Power tubes test with above drivers in order of lowest to highest (opposite to above).

6V6GT Weak bass & over emphasized treble. Not my cup of tea at all.
6K6G Very smooth good for long listening session, a touch less detail.
6F6GT Great tube, good in all departments, good soundstage, forward presence
6BG6GA Same as 6F6 but more soundstage. "surround" sound comes to mind, more enveloping.
6BG6G As above but seemed like the singer was right in front of me up close & personal, nose to nose, LOL.

Really all except the 6V6 were all enjoyable listening experiences, differences were not great but 
I do think the 6BG6's are something special, certainly the best tubes I have come across. It is well worth the small
extra cost for the adaptors to experience the best (IMO) this amp has to offer. Unfortunately something I did not take into account is the G coke tube is even taller than the tall straight tube, so there is a real problem with the adaptors that had to be stretched (external wire) really tight (not good or recommended) so I cut that test short & ordered a new set of custom adaptors with longer wires (same price).
IMO the straight tubes look pretty cool but they do not have to have risers like mine (adds another 11/4"), but the coke ones look a bit on the ridiculous side, however I am just looking for the best sound so I dont care about that.

The conclusion will be when I get the new 6BG6G adaptors & 14AF7's for more listening tests, but at the moment this is my personal best combination.


----------



## baronbeehive

DavidK35 said:


> Gemtunes Amp part 3
> .....
> 
> First I went back to the 12SL7 drivers & gave them another 24 hrs burn in on top of the 3 days they
> ...



I see from your previous post that you list the 12SL7's you tried as Westinghouse and RCA, did you try the Tungsol 12SL7? My only criticism of the 12SL7's is the opposite to your experience, I find them a little too soft if anything, apart from that they sound fantastic, but I keep going back to my 5751's though. I'm waiting for some silver plate GE12SL7's to see if the treble is anymore exciting sounding to see if I agree with what others have said, I think as I have more bass in my speaker APPJ that enhanced treble might sound good, but frankly I am very happy with the set up as it is.

I haven't come across the others you list at all so all very interesting.


----------



## DavidK35

baronbeehive said:


> I see from your previous post that you list the 12SL7's you tried as Westinghouse and RCA, did you try the Tungsol 12SL7? My only criticism of the 12SL7's is the opposite to your experience, I find them a little too soft if anything, apart from that they sound fantastic, but I keep going back to my 5751's though. I'm waiting for some silver plate GE12SL7's to see if the treble is anymore exciting sounding to see if I agree with what others have said, I think as I have more bass in my speaker APPJ that enhanced treble might sound good, but frankly I am very happy with the set up as it is.
> 
> I haven't come across the others you list at all so all very interesting.



Well I wonder then that since you have a different amp to the rest of us, that might be the reason the 12SL's work better for you?.
Previous experience with other amps I have found the 7/14 loctals perform better than the 6/12SL's. All the 14's have metal bases
so do not know if this is a factor. Mostly I have read that the metal based 6SL/N7 tubes are highly sought after.14/7 adaptors are inexpensive & the tubes will only set you back $7 or $8 a piece.
Just burning in my nos 14AF7 atm  & waiting on the new adaptors for the 6BG6G's. The 6211 (12AT7 type) IMO is a totally underated/ignored tube
and deserves more respect (you can get GE 5 star 6211A's for  $3 a piece). I did extensive tests over a long period of time in the past & these tubes outperformed all other 12AT7 types.
Of course we all like different types of sound but this one stood out for me personally.


----------



## Maxx134 (Sep 16, 2017)

DavidK35 said:


> I do think the 6BG6's are something special, certainly the best tubes I have come across. It is well worth the small


I have these and waiting for the adapters to try.

I also found some  6Q5G tubes and wondering if anybody knows or tried them.
I will make sure the pinout is ok to put them in and try them over weekend.

The 14AF7 will also take a while for my adapter to come in from china so its a waiting game but am already happy with my selection.



Miguel Dominguez said:


> My question would be... could the amp be dead? Would the blown fuse have prevented any critical damage to the components?


Try using different tubes, otherwise unknown how the PSU handled your shorting as this unit has some tiny surface mount parts that may have been damaged.
Try with new fuse first and leave open to make any note of anything getting hot or abnormal.
You will need tester to measure voltage as well for repairs, but for now just observe and try not to touch anything and try turn on unit upside down so you can see bottom.

Good luck


----------



## Maxx134

I updated my post to check that broken amp


----------



## Maxx134

DavidK35 said:


> Thanks to Mr Slim for repairing & modifying amp with the Auricap capacitors


So you only upgraded the coupling caps?

More gains to be had with upgrade of the cathode caps.


----------



## DavidK35

Maxx134 said:


> So you only upgraded the coupling caps?
> 
> More gains to be had with upgrade of the cathode caps.



Yes that's right, after reading the whole thread I decided that the changes indicated from the other mod were not for me.

If you have ordered adaptors for the 6BG6 "G"s then I hope you have ordered them with longer external wires than normal.
The ones I got initially were only suitable for 6BG6 "GA"s. The ones I have on order now are 20mm longer.

p.s. if your 14AF7's are NOS I recommend at least 3 days burn in, they take a while.


----------



## Makiah S

Maxx134 said:


> So you only upgraded the coupling caps?
> 
> More gains to be had with upgrade of the cathode caps.


 
What are the difference that upgrading each introduces? Just to recap ;3


----------



## Maxx134 (Sep 20, 2017)

Mshenay said:


> What are the difference that upgrading each introduces? Just to recap ;3



Since the Coupling cap is in between and "couples" the two stages (driver to power stage) then it is unavoildable that it is "in the middle"  ...

So it is usually the bottleneck or most sonically affecting part of the amp overall,
Involving every aspect and signature of the amp,
So it is most critical...

The higher the cap voltage rating,
The better for "transients" and lower capacitor "ESR" value, wich equates to better response time.
Anything 600v or more here is excellent.
As for capacitance, any value .33uf - .47uf is excellent.

******


Cathode cap increase output and all else cathode caps do, like increased gain, lower output impedance, but also add some nonlinearity.
This is done by stabilizing the voltage drop there.
It is usually minimally applied (for cost cutting and other reasons).

But for the output stage, increasing this cap to a larger value provides greatly needed benifit here with this tiny PSU,
by holding the cathode voltage constant, in relation to current demands, so the bias (in relation to the Cathode volt drop)  is not dynamically changed by the music.
So the tube is kept at optimal gain.

So under more heavy dynamic loads, with its increased reserve capacity, it will not weaken so will sound stronger for more sustained power when needed like bass impacts and transients.

Unfortunately there is still sonic changes to be improved here as electrolytics are not sonically perfect, and thus have an indirect impact to sound im upper frequencies.

This is why many instances the cathode cap is paralleled with a smaller film cap for the higher frequencies.

I recommend the "Audio Note KAISEI" electrolytics,
As they supposed to be the best or closest to the legendary "blackgate" caps, which were highly regarded but not made anymore.

Then I use a paralleled bypass cap for the electrolytic,
A film cap of the exact same type/model/sonic signature cap as the coupling cap,
at an arbitrary low value anywhere from .047uf - .1uf max,
( from my experience with this amp and my bigger amp.)
To help the electrolytics with the upper end spectrum.

This is all only my suggestion, as there are obviously other opinions,
So hope this general info help clarify things.


----------



## Maxx134 (Sep 20, 2017)

DavidK35 said:


> 6F6GT Great tube, good in all departments, good soundstage, forward presence
> 6BG6GA Same as 6F6 but more soundstage.


I have just compared my best tubes for this amp (the russian tubes) with the 6BG6G (not the smaller narrow 6BG6GA) mm..
I have come to the exact same conclusion!



DavidK35 said:


> Really all except the 6V6 were all enjoyable listening experiences, differences were not great but
> I do think the 6BG6's are something special, certainly the best tubes I have come across


I must now agree this tube has just "dethroned" my best Russian tubes(!),
As they have the same level of liveliness, with slightly more depth and Soundstage,
Without sounding duller in the process which all the past larger sounding tubes did in comparison.

I am not sure which tube brand you have,
But after looking at the internals,
Amd based on my (weak ) experience,
I would go for the RCA triple Mica first,
Then the NU
Then the Tung-sol.
The newer RCA seem as the rest of them.

Who knows if they all sound as good, but the RCA & Acturus I have definitely sound above all the past powertubes I tried on this amp.
I do have a tung-sol trying next.
*Edit*
Yes the Tung-sol is tied with the pre1950 RCA (triple mica)
Those are the best although Haven't tried the NU or Ken-rad yet.

So Basically you just can't go wrong with any these old 6BG6G tubes...
They big yet gorgeous sound for this amp, 
With similar strong output as the other best.

This is excellent news.
I didn't think it could get better in tube selection.





DavidK35 said:


> If you have ordered adaptors for the 6BG6 "G"s then I hope you have ordered them with longer external wires than normal.
> The ones I got initially were only suitable for 6BG6 "GA"s. The ones I have on order now are 20mm



Yes mine have just enough length thanks.






Oh, and as for the Dumont 6Q5G,
One died upon turn on so they were a bust.


----------



## CZ4A

Maxx134 said:


> Oh, and as for the Dumont 6Q5G,
> One died upon turn on so they were a bust.



6Q5 is listed as a Thyratron tube, not a pentode or kinkless tetrode. I don't think they would have worked anyways- a quick Googling shows thyratrons aren't suitable for amplification, being more of a switch. Unfortunately, they appear to have little use in modern tube circuits.



Maxx134 said:


> Cathode cap increase output and all else cathode caps do, like increased gain, lower output impedance, but also add some nonlinearity.
> This is done by stabilizing the voltage drop there.
> It is usually minimally applied (for cost cutting and other reasons).
> 
> ...



To throw in my two cents for the cathode bypass cap, aluminum polymer caps are also worth a look and are what I'm using now. Polymer caps have very low ESR, high ripple current ratings, and excellent temperature and life ratings. The Sanyo OS-CON (which I think are made by Panasonic now) have been used in tube circuits with good results on other websites. I'm enjoying how my amp sounds now with the Wurth polymer caps- very quiet and even more detailed than before. Of course, you can also bypass the polymer caps with film caps if you so desire.


----------



## Makiah S

oooooh No I can't be hearing about BETTER tubes!!! I just got the Russians! NO MORE I say NO MORE lol, I'm upgrading first THEN going back and rolling MORE tubes xD


----------



## DavidK35

Maxx134 said:


> I have just compared my best tubes for this amp (the russian tubes) with the 6BG6G (not the smaller narrow 6BG6GA) mm..
> I have come to the exact same conclusion!
> 
> 
> ...


I am glad you like them, I knew you would, LOL.
What this hobby/pastime is all about, enjoying better & better sound.
I have the RCA NOS tubes atm, will be getting some more but may be different brands, dont know until they arrive.
Mine are twin mica only.


----------



## baronbeehive (Sep 23, 2017)

Maxx134 said:


> ******
> 
> Cathode cap increase output and all else cathode caps do, like increased gain,
> 
> .....



Yes, there is definitely an increased perception of gain in output, the 3.5W is now more than enough power.



Maxx134 said:


> .....
> 
> So under more heavy dynamic loads, with its increased reserve capacity, it will not weaken so will sound stronger for more sustained power when needed like bass impacts and transients.



Yes, this explains the powerful bass response now, no need of a woofer in my system, (or a pre as far as I can see), and also explains the increased dynamics which, as I said before suddenly began to almost knock me off my chair with surprise after the mods, the transients now are crystal clear and powerful giving a most realistic sense of being at a live performance. Before the mods, the amp was extremely pleasant to listen to but didn't have quite the fullness of tone or the ability to handle sudden changes in dynamics that it does now.



Maxx134 said:


> ....
> 
> Unfortunately there is still sonic changes to be improved here as electrolytics are not sonically perfect, and thus have an indirect impact to sound im upper frequencies.
> 
> ...



You are quite right again, and all the research that went into this on another thread obviously paid off. As I said previously, the bypass caps were necessary to put back the treble response which was somewhat lacking with the bigger Kaisei caps in place. I thought that just using the Kaisei's would be enough but I now believe that anyone using such large capacitance caps will need to complement them with the appropriate bypass caps as well. I've used Audyn copper foil polypropelene bypasses for the Kaisei caps, and the Jupiter copper foil wax and paper coupling caps, therefore the bypass caps are the same type but not the same model as the coupling caps but I couldn't be happier with the sound frankly.



DavidK35 said:


> Well I wonder then that since you have a different amp to the rest of us, that might be the reason the 12SL's work better for you?.
> Previous experience with other amps I have found the 7/14 loctals perform better than the 6/12SL's. All the 14's have metal bases
> so do not know if this is a factor. Mostly I have read that the metal based 6SL/N7 tubes are highly sought after.14/7 adaptors are inexpensive & the tubes will only set you back $7 or $8 a piece.
> Just burning in my nos 14AF7 atm  & waiting on the new adaptors for the 6BG6G's. The 6211 (12AT7 type) IMO is a totally underated/ignored tube
> ...



Yes, quite right, they will be different on this amp, also the combination of power/driver tubes will affect it as well obviously. My experience of headphone amps is that the treble will sound clearer because there is not the bass impact that you get on speaker amps, so the treble is allowed to come through clearly so therefore any treble might sound more accentuated with a treble heavy tube.

Edit:
Incidently, I don't know if others have noticed but I think I experienced a difference in sound between a TS5751 with a "D" getter and one with an "O" getter, although I haven't gone into this, so tube construction is a factor.


----------



## Makiah S

So how would we introduce or solder in a smaller film cap in parallel bigger Kaisei's


----------



## baronbeehive

Maxx134 said:


> I have just compared my best tubes for this amp (the russian tubes) with the 6BG6G (not the smaller narrow 6BG6GA) mm..
> I have come to the exact same conclusion!
> 
> 
> ...



Maxx.you're slipping..... I thought you had already tried every tube lol !!

.


----------



## Maxx134 (Sep 23, 2017)

DavidK35 said:


> I am glad you like them, I knew you would, LOL.
> What this hobby/pastime is all about, enjoying better & better sound.
> I have the RCA NOS tubes atm, will be getting some more but may be different brands, dont know until they arrive.
> Mine are twin mica only.


Usually I don't have any opinions about RCA as they were always a normal bit unexceptionable tube in other types...
But the older (1940s) triple mica 6BG6G RCA has the best internal structure of all of them and is different than the  newer (1950s) RCA.
They perform on par with the Tung-Sol, which to me sound the best out of the 3 names I have in that type.
It was no surprise the Tung-Sol would be up there as one of best, but the old RCA is so impressive for RCA.
Also, I do not expect the NU to surpass either of those two,
But it looks really nice inside at bottom so I may get one to try.
I don't like how the Tung-Sol has a getter at the side of tube and like how the old RCA has double getters at the bottom and two contacts going to its top instead of one.
All other 6BG6G tubes have only one wire going up to top...

Edit:
Also these tubes look very tall and intimidating with the adapters and top connectors.


----------



## Maxx134

I should add that the differences between the various 6BG6G tubes that I tried ,
were the most uniform & minor , or smallest variation I have seen.
I would say the sonic  differences are quite even and probably less than 5% sonic differences.


----------



## baronbeehive (Sep 23, 2017)

Mshenay said:


> So how would we introduce or solder in a smaller film cap in parallel bigger Kaisei's



You connect them as follows: negative to negative, positive to positive.........obviously.



Maxx134 said:


> Usually I don't have any opinions about RCA as they were always a normal bit unexceptionable tube in other types...
> But the older (1940s) triple mica 6BG6G RCA has the best internal structure of all of them and is different than the  newer (1950s) RCA.
> They perform on par with the Tung-Sol, which to me sound the best out of the 3 names I have in that type.
> It was no surprise the Tung-Sol would be up there as one of best, but the old RCA is so impressive for RCA.
> ......



Its seems I'm the only one that likes RCA's.
Although they may be slightly lacking, I find the musical balance to be perfect on the 6SN7's for example.


----------



## Maxx134

Yeah well for our other larger amp,
 the RCA had nice thickness,
But for this 6BG6G, they are top of the heap in construction,  and I still haven't fully decided which I find better yet ,as its so close.

Also, the Russian tubes are still great,
 just not as dimensional.


----------



## baronbeehive (Sep 25, 2017)

Pratt99 said:


> My setup is Bifrost 4490 + APPJPA1502a(with Jantzen Superior Z-cap)+HD600. The only power tube I have is JJ 6v6s. Initially I tried 12AT7 mullard, JJ 12au7 and 12au7 RCA clear top and was not happy. Thanks to @Maxx and @baronbeehive suggestions, I purchased GE 12SL7(silver round plate) , Tungsol 12SL7, Tungsol 5751(vintage) and JJ 12AX7. With my setup, IMO the GE 12SL7 treble sounds just a tiny bit harsh(probably due to HD600s sound signature), however the Tungsol 12SL7 is perfect, followed by Tungsol 5751. Also as @baronbeehive said the JJ12ax7(still burning in) sounds fantastic with this setup.





DavidK35 said:


> ......
> 
> In essence I found my expectation bias was totally contradicted by the unexpected results.
> After all tubes were burnt in  I found the best driver to be the little 6211A. It pretty much wiped the floor
> ...



Just tried the GE12SL7 silver round plates, to see if indeed they do sound a tad harsh in the treble as some have said, or whether they sound more realistic on my system....

Now that I've had initial listening impressions I completely agree with the above 2 posts regarding the 12SL7 GE, but not the Tungsol, the sibilance is especially prominent because I haven't heard that on this amp before, so again I'm back with my TS5751, I don't think it can be beaten!

Just out of interest when the Miniwatt, or speaker APPJ came out several people posted about a diode mod and a pot mod but I haven't been able to find out anyone who can tell what was the effect of these mods. Just to be clear I'm not thinking of doing any more mods but I just thought I would throw this open to discussion to see what other members thought. I have no idea what a  diode mod would do, and even if the pot could be changed there would not be room inside for it probably, but if the stock pot is suspect, and I don't think it is, a stepped attenuator would bump up the sound another notch. I'm sure it could easily be checked to see how well the 2 channels are matched but I'm not sure how to do this, so if anyone is interested let them try it......

I'm assuming that these mods could be done interchangeably on either APPJ.

Edit:
I've finished the listening session and I might have been a little hasty, I'm going to spend a bit more time with this damn tube, it seems to have got better as I've been listening and if it could be less sibilant and more open and resolving like the TS 12SL7 then it could be a good tube, it already has a nice wide soundstage. I'll report back when I've decided on it, and it's had more burn in.


----------



## baronbeehive

Re: the GE12SL7's I've had more time with them and revised my opinions of them somewhat. I still think they're slightly sibilant but I no longer think they're unclear, and as I said before the soundstage is good. Usually my first impressions are what I go by but I've had to go through the proper procedure and test them against my usual familiar test tracks because I wanted to be sure that the sibilance was not just really good detailing over and above what I've heard before. I can confirm though that this is not the case the detailing is good but not more so than say the Tungsols, moreover they are not as liquid as the Tungsols and that would be enough for me to stop using them but I think I will stick with them for a little while longer to see if they get any better. They are certainly good.

I think there is another reason why there is disagreement over some tubes and that is that there is another interaction with the mods we have done, and some mods would give a different sound signature and obviously the ones I have done do not affect these tubes negatively whereas some other mods using perhaps different component makes would have different affects on sound, if this is so then it makes comparisons between tubes difficult and probably members should try for themselves and just use what others have said as a rough guide.


----------



## baronbeehive (Oct 1, 2017)

Re: my comment about the pot mod on the miniwatt, I have just seen a comment by someone that carried out this mod and they said that it further improved the sound quite a lot. Of course anyone who has a preamp  could hook it up and use the volume control of the pre to bypass their APPJ's volume pot to see what effect this has.
I haven't got a preamp but if anyone has it would be interesting to see what happens to the already fantastic sound! The only drawback would be that you are adding in another stage to the system which might adversely affect it soundwise. A review on tnt-audio said about using a pre on the main system_...."there is a slight trade-off inserting another stage but I would say that it is worth a very slight loss of transparency for the extra 'weight' and scale that is gained."_ On the second smaller system they said....._ "Now things were getting really serious. There was a real kick to the bass and it sounded deep too (deeper than the claimed response of 30Hz to 20kHz within 1 db). The sound was ' fuller' and that lean sound on some tracks was gone too. The speed which was already good got even better...."_ I've already said that I don't need a pre on the modded amp as the mods have increased the weight of the sound output anyway.

BTW does anyone know if the APPJ uses negative feedback, because if it doesn't that could explain the clarity of this amp.

Edit:
Re: my suggestion to try using an active volume controller, ie a preamp to see what the effects on sound are by bypassing the pot on the APPJ, the other way might be to try a passive volume controller which would not introduce any further gain stage and so should be sonically purer. However I don't think I will explore this any further because although it would bypass the APPJ's pot, it could just as easily degrade SQ as improve it because of all the additional factors that need to be taken into consideration. As usual nothing is easy!


----------



## Maxx134 (Oct 5, 2017)

DavidK35 said:


> I am not going to go into great technical detail but just list my order of preference based on the listening impact
> each had.
> 1) 14AF7





DavidK35 said:


> p.s. if your 14AF7's are NOS I recommend at least 3 days burn in, they take a while



I just tried a tung-sol 14AF7 and I have to agree that this is just a top notch sounding tube....



 

That makes me interested to try the 14F7 as well.


So I am finding the 14AF7 to a have top notch realism/clarity with a bit more depth or Soundstage,
Which is great because it is still clear.
I find my 12SL7 silver plates a bit more forward and brighter and less dimensional.

Looks like I have a new favorite with the 14AF7, although I like my trebels, they now seem more neutral.
Very good tube!
I may try an RCA next, but I doubt I would surpass the Tung-Sol.
Actually what I cannot find is a Sylvania which would be desirable.

I am also finding the 14AF7 does not run as hot as any of the others,
So I checked and the heater only use 0.15ampere..


----------



## DavidK35

Glad I could help you get closer to Nirvana LOL!
Years back I read that all the loctals were mae by Sylvania but just badged differently,
dont know if thats true or not.


----------



## Maxx134 (Oct 3, 2017)

DavidK35 said:


> Glad I could help you get closer to Nirvana LOL!
> Years back I read that all the loctals were mae by Sylvania but just badged differently,
> dont know if thats true or not.


Yes I heard that about some loctals made by Sylvania for other companies, but not sure about these as there are a lot of philco ones out and these are older tubes in general.


----------



## baronbeehive (Oct 6, 2017)

OK, so it looks like I will have to try the 14AF7 on my amp...... one 14AF7 duly ordered! I still can't see it replacing my 5751 though, we will see.

May be the last tube I try, I've tried examples of the main types, although there are always different versions: 12AX7: RCA - OK, does  the basics well, Amperex - good, nice warm sound, Telefunken - not my favourite type of sound, cold and accurate but boring, 5751: Sylvania JHS, quite good, bright, not my type of sound, JJ  ECC83S, good new issue tube, smooth, open sound, like Raytheon 6SN7 that I tried on my other amp and similar to the Raytheon 5751 according to some reviews, Tungsol, my choice, clear, detailed, open, beautifully smooth yet dynamic, 12SL7,  Tungsol, good, lovely flowing sound but not very dynamic, GE, good but bright, quite harsh, flat, accurate  frequency response, like Sylvanias.

One tube that gets good reviews is the Mullard ECC33, I'm quite curious about this one, don't think I will try though.


----------



## CZ4A

baronbeehive said:


> OK, so it looks like I will have to try the 14AF7 on my amp...... one 14AF7 duly ordered! I still can't see it replacing my 5751 though, we will see.
> 
> One tube that gets good reviews is the Mullard ECC33, I'm quite curious about this one, don't think I will try though.



Not sure if it's been discussed here already, but the octal base equivalent of the 14AF7 is the 12AH7GT. It will need its own adapter because the plate and cathode pins are flipped compared to a 12SN7. Probably better going with a 14AF7 and loctal-to-octal adapter, since you can also try 14F7 (loctal 12SL7) and 14N7 (loctal 12SN7), which have the same pin out.

ECC33 is only available with 6V heater. You won't want to use it in the PA1502A since the filaments will prematurely wear out from overheating.


----------



## baronbeehive (Oct 7, 2017)

CZ4A said:


> Not sure if it's been discussed here already, but the octal base equivalent of the 14AF7 is the 12AH7GT. It will need its own adapter because the plate and cathode pins are flipped compared to a 12SN7. Probably better going with a 14AF7 and loctal-to-octal adapter, since you can also try 14F7 (loctal 12SL7) and 14N7 (loctal 12SN7), which have the same pin out.
> 
> ECC33 is only available with 6V heater. You won't want to use it in the PA1502A since the filaments will prematurely wear out from overheating.



Re: ECC33, my mistake, I meant ECC83!

Yes, thanks, I have a 14AF7/14F7 adapter on order.

Edit: Of the 2 versions I decided to go for the adapter with enclosed pin sockets rather than the exposed ones, (I would rather only the tube lights up, not myself).


----------



## baronbeehive

Incidently of the tube types I've tried above they were all the top versions apart from the RCA and GE. If anyone is interested who doesn't already know, the RCA type have a version which is quite different and better than the common one, very open with great soundstage but it's supposed to be slightly fatiguing to listen to, and the GE version of the 5751 is also done in a cryoed version by watfordvalves which is supposed to improve every aspect of the sound, detail and soundstage, but as I'm not into that type of bright sound I won't be trying it.


----------



## Maxx134 (Oct 20, 2017)

CZ4A said:


> Not sure if it's been discussed here already, but the octal base equivalent of the 14AF7 is the 12AH7GT


I did also see that and was disappointed about the pin order being switched,
Because I could not find an adapter for it,
Which means one would have to make one
Edit found one but didn't bother. 



baronbeehive said:


> Edit: Of the 2 versions I decided to go for the adapter with enclosed pin sockets rather than the exposed ones, (I would rather only the tube lights up, not myself).


Haha yes I went for the exposed  cheaper adapter just in case, as I didn't believe the tube would be better than what I already had,
But the slight increase in Soundstage with more neutral trebles makes them a top choice.
Now I will have to cover the exposed adapter with something nice and pretty lol.


----------



## Pratt99

baronbeehive said:


> OK, so it looks like I will have to try the 14AF7 on my amp...... one 14AF7 duly ordered! I still can't see it replacing my 5751 though, we will see.
> 
> May be the last tube I try, I've tried examples of the main types, although there are always different versions: 12AX7: RCA - OK, does  the basics well, Amperex - good, nice warm sound, Telefunken - not my favourite type of sound, cold and accurate but boring, 5751: Sylvania JHS, quite good, bright, not my type of sound, JJ  ECC83S, good new issue tube, smooth, open sound, like Raytheon 6SN7 that I tried on my other amp and similar to the Raytheon 5751 according to some reviews, Tungsol, my choice, clear, detailed, open, beautifully smooth yet dynamic, 12SL7,  Tungsol, good, lovely flowing sound but not very dynamic, GE, good but bright, quite harsh, flat, accurate  frequency response, like Sylvanias.
> 
> One tube that gets good reviews is the Mullard ECC33, I'm quite curious about this one, don't think I will try though.



@baronbeehive  My favorite pre-amp tube for this amp is TS 5751 as well, so will be looking forward for your impressions. Have ordered the 6BG6G RCA tubes based on @DavidK35 and @Maxx134 reports, upgrading from JJ 6v6 tubes.


----------



## Maxx134 (Oct 9, 2017)

baronbeehive said:


> the 2 versions I decided to go for the adapter with enclosed pin sockets rather than the exposed ones, (I would rather only the tube lights up, not myself



Ok so as you can see I have the cheapo adapter that is all exposed in middle here:



So you can have a shockingly good time touching it to pull it out...


So I improvise with some special tape :




Easy peasy.


----------



## baronbeehive (Oct 9, 2017)

Maxx134 said:


> Ok so as you can see I have the cheapo adapter that is all exposed in middle here:
> 
> So you can have a shockingly good time touching it to pull it out...
> 
> ...



.....clever stuff!! I imagine it revolves round and lights up disco ball fashion with multi colours in time to the music lol.

The alternative version is a funny shape anyway, I don't know why they've made it like that.


----------



## Maxx134 (Oct 20, 2017)

CZ4A said:


> Not sure if it's been discussed here already, but the octal base equivalent of the 14AF7 is the 12AH7GT. It will need its own adapter because the plate and cathode pins are flipped compared to a 12SN7. Probably better going with a 14AF7 and loctal-to-octal adapter, since you can also try 14F7 (loctal 12SL7) and 14N7 (loctal 12SN7), which have the same pin out.
> 
> ECC33 is only available with 6V heater. You won't want to use it in the PA1502A since the filaments will prematurely wear out from overheating.


Good info,
So based on this, I went for a 14F7, as being an "SL" equivalent, it should have more gain like my 12SL7 type .

Looking over the 12AH7 types, I determine they are post war period and so not as old and so not as good, and they have very clear glass and little getter flash which to me is more newer and so at a time when more mass produced (possibly less quality)
I have not looked in thier specs yet but not interested anyways.
Edit:
They are a few year older (3-4) but not made as rigid quality of metal base. 
Odd to see so little flash inside. 





DavidK35 said:


> the only one that I did not like too much was the 14F7
> which I found to be a bit too much in your face & a hair coarser.



Ok,
So I just tried a Sylvania 14F7,
And I did get back more gain.
I am not sure which manufacturer you tried, but I am getting a more lively presentation over the "AF" type, and it sounds great.
I seem to have replaced the slight relaxed nature of the "14AF7" tube, with a bit more "live" factor, while hearing more depth.
So now *these* 14F7 are my favorites! Lol
I probably need to try a Sylvania in the 14AF7 type..


----------



## Makiah S

So I'm having some sound stage issues with my Stock Pair... I finally worked out the freaking 6v6 Tubes I had and Adapters for those sockets are a must... those stock ones are hell to get in and out. I think my tubes weren't even situated correctly for one! 

sound wise I might get a 14AF7 for schiit's and giggles what adapter do I need? Price on it seems pretty good, $15 for two, an extra is always nice 

I'm also having a small issue with the Middle Socket as well... as it's lop sidded...  how would I go about replacing that middle Tube Socket, I've yet to mod this but I'm getting there... got a ton of Product's to review but I've also got some PTO in November... so I figured while I'm modding for improved sound quality maybe I should fix that lopsided socket too... maybe even do what @Maxx134 has done and have it situated completely atop the amp... don't plan on using anything OTHER than Octal/Loctal tubes anyways


----------



## baronbeehive

Mshenay said:


> So I'm having some sound stage issues with my Stock Pair... I finally worked out the freaking 6v6 Tubes I had and Adapters for those sockets are a must... those stock ones are hell to get in and out. I think my tubes weren't even situated correctly for one!
> 
> sound wise I might get a 14AF7 for schiit's and giggles what adapter do I need? Price on it seems pretty good, $15 for two, an extra is always nice
> 
> I'm also having a small issue with the Middle Socket as well... as it's lop sidded...  how would I go about replacing that middle Tube Socket, I've yet to mod this but I'm getting there... got a ton of Product's to review but I've also got some PTO in November... so I figured while I'm modding for improved sound quality maybe I should fix that lopsided socket too... maybe even do what @Maxx134 has done and have it situated completely atop the amp... don't plan on using anything OTHER than Octal/Loctal tubes anyways



For the adapter you need one of these:  http://www.ebay.co.uk/itm/1pc-14N7-...593023?hash=item2ed22bf9ff:g:g0cAAOSwNSxVDj6A
or: http://www.ebay.co.uk/itm/1pc-14N7-...997792&hash=item2ecce7915d:g:JA0AAMXQVT9SsbA4
The last one is what you saw on Maxx's amp but I wouldn't advise it as it could be dangerous!

To resolder the middle tube socket would be tricky to do, I haven't attempted it because a special tool might be needed to solder all the pins at once, so expert help may be needed there.


----------



## DavidK35

baronbeehive said:


> For the adapter you need one of these:  http://www.ebay.co.uk/itm/1pc-14N7-...593023?hash=item2ed22bf9ff:g:g0cAAOSwNSxVDj6A
> or: http://www.ebay.co.uk/itm/1pc-14N7-...997792&hash=item2ecce7915d:g:JA0AAMXQVT9SsbA4
> The last one is what you saw on Maxx's amp but I wouldn't advise it as it could be dangerous!
> 
> To resolder the middle tube socket would be tricky to do, I haven't attempted it because a special tool might be needed to solder all the pins at once, so expert help may be needed there.



That 2nd adaptor you link I bought also but I did not like the open structure, so i emailed  xulingmrs. He suggested to put heat shrink on it but i did not like that either, so I ordered a custom one with solid cover like all the others. Cost $15.90 + shipping, looks great. Should have pics shortly with custom base I made of solid Padauk wood + mounting feet to beef up its appearance.


----------



## DavidK35 (Oct 18, 2017)

Ok,
So I just tried a Sylvania 14F7,
And I did get back more gain.
I am not sure which manufacturer you tried, but I am getting a more lively presentation over the "AF" type, and it sounds great.
I seem to have replaced the slight relaxed nature of the "14AF7" tube, with a bit more "live" factor, while hearing more depth.
So now *these* 14F7 are my favorites! Lol
I probably need to try a Sylvania in the 14AF7[/QUOTE]


Thats the great thing about tubes, there is a flavor to suit everyones taste.


----------



## baronbeehive

DavidK35 said:


> That 2nd adaptor you link I bought also but I did not like the open structure, so i emailed  xulingmrs. He suggested to put heat shrink on it but i did not like that either, so I ordered a custom one with solid cover like all the others. Cost $15.90 + shipping, looks great. Should have pics shortly with custom base I made of solid Padauk wood + mounting feet to beef up its appearance.



I bought the adapter from the first link and its ok but looks a bit odd due to its shape.

Just received my Tungsol 14AF7, and first impressions are very favourable, I will report back after a bit more listening. I took a bit of a chance with it buying it with no test data but it looks and sounds NOS so I think I got away with it. I also have bought an RCA 14F7 to see if it is indeed more forward sounding, if that's the case it should be OK because the RCA sound should smooth over that.

I don't know how you came across these tubes but it looks like you are on to something here, I would never have thought of them as a 12AX7 substitute. I'm not sure about them all being rebranded Sylvanias though, the one I've got looks typical Tungsol construction, I've never seen a Sylvania like this before. If it was Sylvania it would have to be made in their factories and so I don't see how it could look like a Tungsol. I know that manufacturers used to get bulk orders to satisfy and often had to buy up other suppliers stock when they couldn't meet demand.

I read somewhere that the loctals were produced when they needed a tube with shorter pins because the longer pin variety were picking up interference, so maybe they are actually an improvement.

I've been finding that my system seems to be getting even better and more open sounding lately and wondered if it was because of the longer burn in time for the caps I put in, this is possible because I don't bother burning in now and just note any differences over time.


----------



## DavidK35

baronbeehive said:


> I bought the adapter from the first link and its ok but looks a bit odd due to its shape.
> 
> Just received my Tungsol 14AF7, and first impressions are very favourable, I will report back after a bit more listening. I took a bit of a chance with it buying it with no test data but it looks and sounds NOS so I think I got away with it. I also have bought an RCA 14F7 to see if it is indeed more forward sounding, if that's the case it should be OK because the RCA sound should smooth over that.
> 
> ...




Read about them years ago in Head-Fi & been using them ever since. The only thing you have to remember is, what heater voltage your amp is wired for. This will determine wether you use a 14AF7 or 7AF7. Sometimes the driver tube is 6v & power tubes 12v etc, you have to confirm with amp manuf. first. Part of the impetus with these was for airplanes in WWII, they were developed to prevent them from falling out during difficult manouvers that could happen with octals. But it required a new line to be set up for manufacture, so some, maybe not all would just re brand them but were made in the Sylvania factory. The only drawback if you can call it that is there is 3 basic flavors, however since IMO they are all better than any 6/12/SN/SL7 anyway, the problem is mute.


----------



## DavidK35

baronbeehive said:


> I bought the adapter from the first link and its ok but looks a bit odd due to its shape.
> 
> Just received my Tungsol 14AF7, and first impressions are very favourable, I will report back after a bit more listening. I took a bit of a chance with it buying it with no test data but it looks and sounds NOS so I think I got away with it. I also have bought an RCA 14F7 to see if it is indeed more forward sounding, if that's the case it should be OK because the RCA sound should smooth over that.
> 
> ...





baronbeehive said:


> I bought the adapter from the first link and its ok but looks a bit odd due to its shape.
> 
> Just received my Tungsol 14AF7, and first impressions are very favourable, I will report back after a bit more listening. I took a bit of a chance with it buying it with no test data but it looks and sounds NOS so I think I got away with it. I also have bought an RCA 14F7 to see if it is indeed more forward sounding, if that's the case it should be OK because the RCA sound should smooth over that.
> 
> ...



p.s. I just replaced the 5670 tube in my dac to a 7AF7 with adaptor and WOW the Gemtunes is really amazing now. I informed the DAC manuf of my mod & he says I am the first to try this LOL.


----------



## Maxx134

DavidK35 said:


> Part of the impetus with these was for airplanes in WWII, they were developed to prevent them from falling out during difficult manouvers that could happen with octals.


OMG can you imagine the  poor sap that did a fancy maneuver and had his tubes fall out!  lol. 



DavidK35 said:


> however since IMO they are all better than any 6/12/SN/SL7 anyway,


This is quite an eye opener for me to experience. 
Dam, now I wondering now how the 7af7 would sound on my bigger Amp which now using a 6SL7 type.


----------



## baronbeehive (Oct 20, 2017)

Maxx134 said:


> OMG can you imagine the  poor sap that did a fancy maneuver and had his tubes fall out!  lol.
> 
> .......



Ha ha..... that's the last thing you want to happen in the middle of a tricky manoeuver lol.



Maxx134 said:


> ....
> 
> This is quite an eye opener for me to experience.
> Dam, now I wondering now how the 7af7 would sound on my bigger Amp which now using a 6SL7 type.



Looks like the entire mods thread will have to be rewritten.......!!
There are many more tubes that could be used that have been ignored also.  I remember John in the LD thread tried tubes similar to this which were also very good and cheap, but without re-reading the entire thread I can't remember what the tubes were.

Edit: I think they were 6f6's. I remember trying the Raytheons.


----------



## DavidK35

A couple of pics for you.


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## baronbeehive (Oct 24, 2017)

DavidK35 said:


> p.s. I just replaced the 5670 tube in my dac to a 7AF7 with adaptor and WOW the Gemtunes is really amazing now. I informed the DAC manuf of my mod & he says I am the first to try this LOL.



I know how you feel now, I've had the TS 14AF7's for a  couple of days now and I can confirm what you guys are saying, it is a great tube. On a head to head with the TS5751 I would say that it is marginally less silky and more realistic and live sounding, the treble is marginally more extended and neutral sounding, and the soundstage is marginally more realistic and equally open sounding as the 5751. It is really great, I can't make up my mind however if it is better than the 5751 because I really love that silky sound, but I can vary this with a more live sound if I want to now so I will keep them both and I think I will rank them first equal for different reasons. I would say you couldn't go wrong with either tube but which one you go for depends on whether you like silky smooth, or live sound.

This system is sounding fantastic.... and could get even better... I don't know if the tube is NOS but if it is then it has had no burn in yet!

Your amp looks great with its wood base now btw!

Edit: RCA 14F7 arrived today, plates are the same but matt colour instead of shiny, RCA has an extra rod from top to bottom, bottom mica slightly different, glass tube slightly smaller, looks in good condition, but no test results again.


----------



## Maxx134 (Oct 24, 2017)

I tried a Sylvania 14n7 the other day and it was very good,
But not as impressive as the (Tung-Sol) 14AF7,
or the (Silvania) 14F7 type.

Then I took a look and saw inside the 14n7 was not using round plates,
 but the newer angled type you see in later/newer tubes..
So that confirms to me my past experience that I prefer round plates as having an edge in realism.

I just received a Tung-Sol 14F7 that I will try next.


----------



## Makiah S

I hate to ask this, but some things have come up in my life that have put a restriction on my time... I don't think I will be in a position to mod this unit my self this year. An I'd like to not have to wait till 2018 to start listening to it! That said I may need to reach out to some one to perform the mods in my place, which may be better. I might try my hand at building a cMoy BB as my first project rather than soldering and modding this tube amp...


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## baronbeehive (Oct 24, 2017)

Maxx134 said:


> I tried a Sylvania 14n7 the other day and it was very good,
> But not as impressive as the (Tung-Sol) 14AF7,
> or the (Silvania) 14F7 type.
> 
> ...



I think you're in for a treat my friend!

Re: the RCA 14F7 which I got today, it is another wonderful tube, so it goes into my top 3: TS5751, TS14AF7 and now RCA14F7.

I had a moment on another planet agin when I first tried it.... to do with the ambient music I had on as well as the tube, so to try to retain objectivity I went through my test tracks again. I expected it to have a nice musical balance being an RCA, but I didn't expect it to have great detail and soundstage, like the other 2 tubes. On that first piece of music I tried, the soundstage was wide, deep, and all enveloping, but this depends on the music and I think that the other 2 tubes are fairly similar. It gets more and more difficult to separate the small details between tubes when they are at this top level. As a 14F7 rather than a 14AF7 it has more gain as expected which makes it better for me but I didn't find it any more forward or harsh which I suspect is more down to the type of 14F7. Once again the realism is there, also I found it going down to really deep bass which is something that I hadn't noticed before, I may have just missed that before, but the bass was more of the type you feel rather than hear, it was that deep, and that makes the music very full sounding. The thing that made it difficult was knowing the construction was pretty identical to the TS14AF7, I didn't know if the RCA was really a Tungsol in disguise lol.

So to sum up:
1 - TS5751, treble has a silky sheen to it, very liquid, but still has the dynamics when needed, detailed, controlled, open soundstage
2 - TS14AF7, still smooth, more neutral and extended treble, more live sounding, detailed, open soundstage
3 - RCA12F7, this was the surprise. Smooth, detailed, fairly neutral, live sounding, open soundstage, I found it enveloping but mainly down to the music being played, extended bass.

I would rate them equal, but my preference is for the TS5751, followed by the TS14AF7, then the RCA14F7, but they were all very close.

Looking forward to your impressions of the TS14F7 Maxx!


----------



## wantech

baronbeehive said:


> I think you're in for a treat my friend!
> 
> Re: the RCA 14F7 which I got today, it is another wonderful tube, so it goes into my top 3: TS5751, TS14AF7 and now RCA14F7.
> 
> ...




I am new,
can I hook up speakers on pa1502a ? how ?


----------



## baronbeehive

wantech said:


> I am new,
> can I hook up speakers on pa1502a ? how ?



No, I'm the only one on this thread that has the PA0901A speaker amp.


----------



## benjisun

Here is Mine with TungSol 6L6GC and JJ long plate 12AX7 gold


----------



## Maxx134

baronbeehive said:


> Looking forward to your impressions of the TS14F7 Maxx!


The Sylvania had a touch more "air", 
Otherwise identical performance. 



benjisun said:


> Here is Mine with TungSol 6L6GC and JJ long plate 12AX7 gold


Nice!
The 6L6 should give great Soundstage and the 12ax7 should give you very lively performance to offset the 6L6 distant. 
I can see that as a nice combination. 
So just depending on your dac aggressiveness, it probability sounds sweet for you... 

The advantage of this amp is the ability to fine tune and match with  any gear thru such a wide range of tubes... 
It's all about the synergy of your system. 

That's why tube Amps have advantage to "tune", and especially this one!
The list in this thread of tubes tried is already so much already. 

Since I have yggy as dac I went for most clarity in tube Choice, and the latest choices work nice.

I would suggest everyone try the 14AF7 type(&14F7), and feel the metal base is better quality than most.


----------



## DavidK35

Been enjoying the music so much with the latest set up I have lost all desire for any upgraditus.
Changing the Canary DAC to a 7N7 instead of 7AF7, now the combination of  7N7 DAC & 
Gemtunes 14AF7 + 6BG6G is perfect. Seems to give the exact right balance.
Now I know some of the purists out there will say that is too many tubes in the chain but I always
let my ears be the judge, and I find it faultless.

Klaus Schultze - Ballet 3 & 4 has been a revelation, especially My Ty She/Mellowtrone/Soft n Groovy.
Thats 2 hours of heaven right there.

Sometimes you dont have to spend the big bucks to get the best sound.


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## baronbeehive (Nov 3, 2017)

Maxx134 said:


> The Sylvania had a touch more "air",
> Otherwise identical performance.
> ....
> I would suggest everyone try the 14AF7 type(&14F7), and feel the metal base is better quality than most.



Yes, agreed!They are the best tubes so far....both the 14AF7 and 14F7's seem to have a similar sound, apart from the gain. Did you look at the internal construction. I've just checked the TS14AF7 and the RCA14F7 and they are both round plates but the RCA's are larger diameter, more typical RCA. I believe the Sylanias are different again.



DavidK35 said:


> Been enjoying the music so much with the latest set up I have lost all desire for any upgraditus.
> Changing the Canary DAC to a 7N7 instead of 7AF7, now the combination of  7N7 DAC &
> Gemtunes 14AF7 + 6BG6G is perfect. Seems to give the exact right balance.
> Now I know some of the purists out there will say that is too many tubes in the chain but I always
> ...



Absolutely! I too am happy with the amp and not looking to change anything lol.
I was wondering about the tube combination you have there with the DAC in the mix, so it looks and sounds good. That's great!
Been listening to some HD tracks, (24bit 96kh), and it's awesome...lacks for nothing, can almost feel the singers breath!!


----------



## baronbeehive (Nov 5, 2017)

DavidK35 said:


> .......
> 
> Klaus Schultze - Ballet 3 & 4 has been a revelation, especially My Ty She/Mellowtrone/Soft n Groovy.
> Thats 2 hours of heaven right there.
> ...



My gosh, just listening to this now, wonderful! So much better than the usual techno. The nearest I've got to this would be Vangelis, the Blade Runner Theme, or Heaven and Hell for example, or some of his other stuff. Thanks for bringing this music to our attention, maybe we should start a music appreciation thread lol! I'm always on the lookout for new music.


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## Maxx134 (Nov 5, 2017)

DavidK35 said:


> Now I know some of the purists out there will say that is too many tubes in the chain but I always
> let my ears be the judge, and I find it faultless.


You can never have too many tubes components in your  gear/chain. .
There's Just too many examples that Tubes portray music better in every way.
Once you go tubes on a good design setup, it's hard to turn back.
You get spoiled,  and in need of higher end Solid State gear to try match it.




baronbeehive said:


> I've just checked the TS14AF7 and the RCA14F7 and they are both round plates but the RCA's are larger diameter, more typical RCA. I believe the Sylanias are different again.


TOO bad Sylvania changed from round plate to that ribbed angled plates on the 14N7 I tried.
It's good still, but Just not at the same level.
The 14AF7 is nice, but lower MU gain and so it is a touch laid back as well.
I prefer the more immediate 14F7 which still has great Soundstage above my past driver tube choices.
This driver also pushes the power tubes to their maximum power abilities when needed.

Also,
The 6BG6G is just an amazingly excellent power tube for this particular amp.
It just matches the amp bias points so well that is sounds best here.
It is also so  visually impressive and large as well.

I have compared this combo to my larger tube amp and can say it holds its own at normal levels which is a huge huge feat.
It's not perfect at maximum or minimum levels,
But I bet I can drop Jaws in disbelief with this amp in this configuration.
My Sweet baby amp lol.


----------



## DavidK35

baronbeehive said:


> My gosh, just listening to this now, wonderful! So much better than the usual techno. The nearest I've got to this would be Vangelis, the Blade Runner Theme, or Heaven and Hell for example, or some of his other stuff. Thanks for bringing this music to our attention, maybe we should start a music appreciation thread lol! I'm always on the lookout for new music.


Glad you liked it, only found it by accident recently, although I have known Tangerine dream for the longest time. 2 other CD's of his I really like are:

Contempory Works II #4 Androgyn (particularly tracks 3,4,5,6 which is basically one 35min track) &
Contempory Works II #1 Virtual Outback (track 1, 65mins)

Sounds so good on the Gemtunes & the recording quality really helps here.


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## baronbeehive (Nov 9, 2017)

Maxx134 said:


> ...
> 
> I have compared this combo to my larger tube amp and can say it holds its own at normal levels which is a huge huge feat.
> It's not perfect at maximum or minimum levels,
> ...



That's pretty amazing! Not surprised it doesn't have the brute power for the highest volume levels.

I just compared my baby amp to a friends setup at the weekend, he has £1500 speakers, four times more expensive than mine and frankly I preferred mine, although I didn't tell him! I think the sound is more refined and warmer on the APPJ/Monitor Audio combo with the 14Af7 tubes. The only thing that is inferior is the amount of sub bass which is powerful on his floormounts whereas my standmounts do not register this low, but frankly the balance is still very good for me.



DavidK35 said:


> Glad you liked it, only found it by accident recently, although I have known Tangerine dream for the longest time. 2 other CD's of his I really like are:
> 
> Contempory Works II #4 Androgyn (particularly tracks 3,4,5,6 which is basically one 35min track) &
> Contempory Works II #1 Virtual Outback (track 1, 65mins)
> ...



Thanks, I'll check those out. Funny you should mention Tangerine Dream, that's the other name that sprung to mind after Vangelis, but I didn't know of the connection. You should check out "Heaven and Hell" if you haven't already. I've heard practically all of Tangerine Dream quite a while ago at Uni, a friend was into them, the favourite of mine that I still have is "Exit", I find after a while all of theirs begin to sound the same though.

Edit: I've been thinking about why my system sounds so open, even with mp3's whereas my friend's system with £1500 speakers sounds so closed with mp3's, although it sounded superb when high res tracks were being played, and I think it must be down to the Jupiter coupling caps, I would also think that Audyn's would sound similarly spacious and airy.


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## baronbeehive (Nov 7, 2017)

Just looking through some old tubes and I noticed that the Tungsol 12SL7GT that I was using that was causing a lot of static noise was in fact a 6SL7GT....... no wonder!!! I think I must have ordered a 6SL7 by mistake.

That's the trouble with having another amp that uses the 6SL7's, confusing lol !


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## baronbeehive (Nov 12, 2017)

Guys, I mentioned recently that I've been listening to some high res, 24bit 96kh music. I don't know if anyone has tried high res music here but I would urge you to try it because the amp has just gone up to yet another level in performance! For example you can download some free sampler tracks here: http://www.hdtracks.co.uk/landing. One of the tracks is by Diana Krall, I also have the album on ordinary res and so I can compare them and the difference is very noticeable, for example the bass notes tighten up considerably and lose any trace of bloat, and the soundstage opens up very markedly. If anyone is wondering where an extra 5% of audio excellence would come from this is it! The clarity is quite astonishing. The only drawback is the supply is fairly limited but if you can get some of your favourite albums in high res, I guarantee you will not want to stop playing them.

I tried high res music some time ago and didn't notice it to this extent, possibly because I only tried the SACD standard not the very high res we now have so I was quite surprised to hear the difference. I would be interested what others thought about this.


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## baronbeehive (Dec 21, 2017)

I just wanted to come on again guys because lately I've revised my opinion about the 12SL7GE which I rather dismissed before although I did actually say it was a good tube at the time. I've been listening to it quite a bit lately and now I would put it right at the top with the TS 5751 and the 14AF7 TS. The thing is I couldn't get used to the slight harshness at the top end having been used to a much smoother tube but I must say I really like the sound now, I agree with Maxx who also liked this variety of tube, with a good recording it sounds wonderfully transparent with a superb bell like ring to the treble. I also agree with DavidK35 though because on some recordings it can sound slightly thin. On your headphone APPJ it might sound thin due to having less bass output, I get quite a lot now out of the speakers. Because of this change of mind I'm now saving up to try the cryo GE5751 from Watford Valves that I mentioned before. I was curious about this tube and it could be really good when I can afford it.

Edit:

Update on the 14F7 RCA, glorious tube! Wide soundstage with everything in perfect balance, fatter sound than the GE 12SL7 yet the treble rings out almost GE like. I think I like this tube better than the 14AF7 TS which is more neutral sounding. It's everything you like about RCA's, I love them. Does no tube sound bad on this amp? The bass is probably the biggest of the 4 tubes I mentioned. So far my favourites: TS5751 for its silky sound, GE for its clean sound, RCA for its balanced sound and TS 14AF7 for its neutral sound. I like all 4 for different reasons.


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## davidland

cool！


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## baronbeehive (Dec 24, 2017)

Just ordered a Mazda 12AX7 to satisfy my curiousity, it's supposed to be very Mullard like with the same plate construction very high gain and with forward mids. Many people think mullards are the best 12AX7 and I haven't tried any of the ECC83 type tubes apart from the JJ ECC83S. Then finally to complete my tube rolling experiments I've ordered a GE 14AF7. Having liked the shiny plate GE 12SL7 I wanted to try another GE to see how it compares. The shiny plate is rarer than the black or grey plate GE.

I noticed that the 6SN7 GE's get rather bad reviews, but the 12SN7's are grey, flat or box type plates, whereas the 12SL7's are the shiny round plates, perhaps this has a bearing on sound. Bearing in mind the 12SL7's that I tried are 12 volt versions of 6SN7's with higher gain I wanted to see what other GE's were like. Also the 14AF7's that I've tried have  been very good. I liked the forward treble and the transparency of the GE's. The 5751-12AX7 GE's are said to be the best clean sounding tubes of that type so it will be interesting to see what the 14AF7's are like.


----------



## baronbeehive

Wow, this Mazda 12ax7 is something else, it really grabs you by the throat, and then kicks you when you're down.... By that I mean it packs a punch for sure. I don't really know what to say, it's different to anything I've heard, it's the polar opposite of the GE for example. Instead of being light, airy, fast and treble centric it's dynamic, punchy, powerful, tubey, warm rich midrange, biggest bass of all, outstanding detail, 3d soundstage. The tube is very Mullard like as I expected.

These are my intial impressions having just received the tube today, I might update on this later if there is anybody out there, I think I might be the only person alive here now, maybe the aliens have abducted the rest of the forum members and taken them away from all this madness, shame they are not here to hear this fantastic tube, oh well never mind....


----------



## braaam

baronbeehive said:


> Wow, this Mazda 12ax7 is something else, it really grabs you by the throat, and then kicks you when you're down.... By that I mean it packs a punch for sure. I don't really know what to say, it's different to anything I've heard, it's the polar opposite of the GE for example. Instead of being light, airy, fast and treble centric it's dynamic, punchy, powerful, tubey, warm rich midrange, biggest bass of all, outstanding detail, 3d soundstage. The tube is very Mullard like as I expected.
> 
> These are my intial impressions having just received the tube today, I might update on this later if there is anybody out there, I think I might be the only person alive here now, maybe the aliens have abducted the rest of the forum members and taken them away from all this madness, shame they are not here to hear this fantastic tube, oh well never mind....



You’re not alone! Which Mazda did you get - as there are several version depending on age. Most common are the silver anode ones (which come in triple/two mica versions). These are very nice IMO - I started to hoard them at some point (as I did with triple mica 12at7 Mazda’s as wel, but they sound very different again - massively punchy, but much more compressed).


----------



## baronbeehive

braaam said:


> You’re not alone! Which Mazda did you get - as there are several version depending on age. Most common are the silver anode ones (which come in triple/two mica versions). These are very nice IMO - I started to hoard them at some point (as I did with triple mica 12at7 Mazda’s as wel, but they sound very different again - massively punchy, but much more compressed).



Ah, greetings to another life form, human I assume!

I got the Mullard type grey ladder plate because I wanted to check on the Mullard sound as a side issue to the Mazda itself, they're supposed to be quite similar sounding. Having noticed the silver anode version I would really like to try that as well though now..... I recently found that I liked very much the very transparent sound of the GE's, again different to my usual favourites, and I wondered if the silver plate would be an advance on the GE or very similar, I don't know. So I'm not sure whether it's worth trying. The Mazda is double mica with "o" getter.


----------



## braaam

baronbeehive said:


> Ah, greetings to another life form, human I assume!
> 
> I got the Mullard type grey ladder plate because I wanted to check on the Mullard sound as a side issue to the Mazda itself, they're supposed to be quite similar sounding. Having noticed the silver anode version I would really like to try that as well though now..... I recently found that I liked very much the very transparent sound of the GE's, again different to my usual favourites, and I wondered if the silver plate would be an advance on the GE or very similar, I don't know. So I'm not sure whether it's worth trying. The Mazda is double mica with "o" getter.



Nah, just a bot to keep some level of activity around here 

The Mazda’s are sometimes hard to identify. Interesting enough, Mazda never really manufactored its own tubes, but instead rebranded them. 

Mazda France started in the early 50s and Mazda was used as a brandname in the UK a lot later. They were only losely related through Thomson, the parent company. The Mazda tubes from the UK, which mostly originate from the late 60’, are often rebadged Brimars, and sound close to the Mullards and Philips tubes of that time! 

Going from your description, I suspect yours may be relabelled Brimars. Do you have a picture of them? The UK Mazda’s mosty come in blue packaging and labeling. The Mazda tubes from France, which came earlier, have different characteristics and often carry a white or golden label. 

If you look at the French silver plate versions, and compare them to the early GE 5751 design, you will see that they are almost identical. In the 50s, GE owned part of Mazda France. They also owned the Mazda trademark which was used for premium quality incandescant bulbs in the 30s.

To me, the silver plate Mazda sounds more open than Mullards, with a more even balance and better extension at the top and less emphasis on the mids. They have their own unique sound signature, but if you like the GE’s you may want to give it a go if you can get a hold of one! They do share the openness and transparancy with the early 50s/60s GE tubes.


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## baronbeehive (Dec 31, 2017)

Ha ha, from one bot to another programmed to keep this thread alive....

thanks for the info, that's cleared up one or two things. I didn't really go into it but I was wondering what I got, a Mullard with Mazda brand or Mazda made in England, whatever, anyway I'm not too concerned, either way I wanted to try the Mullard/Mazda type sound. I thought it might be a Mullard but what you say is interesting, I have heard a Brimar in my 6SN7 amp and the sound is remarkably similar despite this one being a 12AX7, very dynamic, vivid  sound. I said that I didn't know what to think and that was because I didn't really like the Brimar/Mullard type sound first time round, or at least it was too overpowering for easy listening, nevertheless it is amazing. I think it might be good on the headphone amp, mine is the speaker amp.

I think I would prefer the silver plate Mazda. I didn't know about that until recently. I hadn't noticed the likeness to the GE's but you're right, it does resemble them, except for the silver colour plates, also the slots.

I have tried the 12SL7 GE's on my speaker amp and these are a bit unusual in that they have round sections in the middle of the plates where it is normally box construction, and silver plates so I don't know how representative they are of GE's in general. That's why I was interested in trying another type such as the 14F7 which I have on order, or a cryo GE 5751 from watford Valves. I really love the transparency but was put off by the slightly thin, slightly harsh sound but it's  not that pronounced and works really well in my amp.


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## baronbeehive (Dec 31, 2017)

These are a couple of pics, not brilliant but you get the idea:

The tube has a code: 40D near the bottom, which I could not decipher, has got the Mullard designation: BVA, without the shield, depite saying Made In Holland, and has the 4 seams on the top of the glass that Amperex's have got and appears to be made for export. My feeling is that it is a late 1950's - early 1960's Mullard with Mazda brand or Mazda made by Mullard. It sounds Mullard like, and quite like Brimar also, but is quite aggressive and tubey sounding which is why my guess is Mullard. Bit complicated: A french Mazda, with British made code, and made in Holland label, and difficult to tell from looking at them!! At least the silver anode is fairly straightforward! What do you think?


----------



## braaam

baronbeehive said:


> These are a couple of pics, not brilliant but you get the idea:
> 
> The tube has a code: 40D near the bottom, which I could not decipher, has got the Mullard designation: BVA, without the shield, depite saying Made In Holland, and has the 4 seams on the top of the glass that Amperex's have got and appears to be made for export. My feeling is that it is a late 1950's - early 1960's Mullard with Mazda brand or Mazda made by Mullard. It sounds Mullard like, and quite like Brimar also, but is quite aggressive and tubey sounding which is why my guess is Mullard. Bit complicated: A french Mazda, with British made code, and made in Holland label, and difficult to tell from looking at them!! At least the silver anode is fairly straightforward! What do you think?



These are great tubes! The first etched character is most likely not a 4, but a triangle, which is the factory code for Philips Heerlen. The 2nd character, the zero, stands for the year. This type with the shorter plates was made from around 1959 untill end 70s. The earlier ones did have the 4 seems on top, and a bigger halo getter. Yours then looks to be from 1960, a very good vintage! 

BVA was used by multiple British tube manufactorers - Brimar as well - it was a stamp for good quality products. 

The Philips tubes in general are more lively then Mullards, have a bit less mid emphasis but are still very smooth in sound. A favourite of many - personally I prefer them to most Mullards. The earlier long plate variants can sound even better, but yours should be close to these in sound.


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## baronbeehive (Jan 23, 2018)

braaam said:


> These are great tubes! The first etched character is most likely not a 4, but a triangle, which is the factory code for Philips Heerlen. The 2nd character, the zero, stands for the year. This type with the shorter plates was made from around 1959 untill end 70s. The earlier ones did have the 4 seems on top, and a bigger halo getter. Yours then looks to be from 1960, a very good vintage!
> 
> BVA was used by multiple British tube manufactorers - Brimar as well - it was a stamp for good quality products.
> 
> The Philips tubes in general are more lively then Mullards, have a bit less mid emphasis but are still very smooth in sound. A favourite of many - personally I prefer them to most Mullards. The earlier long plate variants can sound even better, but yours should be close to these in sound.



Thanks braaam for that valuable information! I had difficulty with those codes, they kept changing them. I'm glad I finally tried these tubes, but am really thinking that I would like to check out those silver anode Mazdas, as that is more my type of sound...... but I will keep the Mullards/Philips for curiousity value!

Edit: Quick update. I'm loving this tube, I'm completely won over, the 3d soundstage and the detail in the midrange, voices, for example, are wonderful.

Edit2: Just tried the 14AF7 GE's and they're pretty crap, especially after the Mullard's. Thin, flat, and boring sounding, I don't think I will be spending any more time with them. The plates are different to the 12SL7 GE's which I like, they seem to be much more musical sounding than the 14AF7's.

That's the end of my tube rolling, hope that's been of interest, it's been fun seeing how different this amp can sound!

I don't like keeping lots of superfluous tubes lying around as I've settled on my favourites and it's not worth putting them on ebay so if anyone is having any difficulty getting anything they could PM me you can have them for a nominal sum, they're all good and pretty cheap. I have a few different types: Amperex 12AX7, Philips Miniwatt 12AX7, TJ Full Music 12AX7 (new issue), Tungsol 12AX7 (new issue), GE 14AF7, Tungsol 14AF7, RCA 14F7, GE 12SL7 and a matched pair of nos Russian 6F6C Kobra's. I just want to de-clutter!


----------



## Maxx134

braaam said:


> The Philips tubes in general are more lively then Mullards, have a bit less mid emphasis but are still very smooth in sound. A favourite of many - personally I prefer them to most Mullards. The earlier long plate variants can sound even better, but yours should be close to these in sound


I agree totally.
I have an old Millard 12au7 that has a bit too much euphoric mids and is supposed to be more neutral than the 12ax7 type.
I will have to compare them again.



baronbeehive said:


> Edit2: Just tried the 14AF7 GE's and they're pretty crap, especially after the Mullard's. Thin, flat, and boring sounding, I don't think I will be spending any more time with them. The plates are different to the 12SL7 GE's which I like, they seem to be much more musical sounding than the 14AF7's.


Looks like I have to try them haha


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## Makiah S (Jan 19, 2018)

Yea I've not listened to this bad boi since October! Hooked everything back up today and I'm kinda impressed how well it does with my AKG K240 Sextett, though I am driving High gain out of my DAC and High Gain from the amp it self. Not sure if this is rated for a 600Ohm but it's doing pretty good.  JJ 6V6s Power Tubes and a Sylvania 12SL7GT Jan CHS vt289

The previous channel imbalances issues I had seem to be gone! In fact I'm really impressed with how well this handles stereo music, my K240 has a really nice cohesive sound stage! Quite impressive really. I've also reached out to a member here to have some Mods performed at a later date. I might just enjoy it stock for now since it seems to be working nicely! An check back in once said mods are complete'd.

As for parts I'm kinda set on the

*ANKECAP-81784 Audio Note Kasie's that every one talks about 1000 uF an 25VDC*

*For the Coupling Film Caps I like what I heard from David on the 
AURIXO-75911
 Auricap XO .47 400VDC 

My only question is about the Film Caps you guys have recommend installing in Parallel with the Electrolytic Cathodes, I saw the .047 recommendation. But I don't see film caps with the same 1000 uF 25VDC rating as the Electro's that they'd be in parallel with *


----------



## baronbeehive

Mshenay said:


> Yea I've not listened to this bad boi since October! Hooked everything back up today and I'm kinda impressed how well it does with my AKG K240 Sextett, though I am driving High gain out of my DAC and High Gain from the amp it self. Not sure if this is rated for a 600Ohm but it's doing pretty good.  JJ 6V6s Power Tubes and a Sylvania 12SL7GT Jan CHS vt289
> 
> The previous channel imbalances issues I had seem to be gone! In fact I'm really impressed with how well this handles stereo music, my K240 has a really nice cohesive sound stage! Quite impressive really. I've also reached out to a member here to have some Mods performed at a later date. I might just enjoy it stock for now since it seems to be working nicely! An check back in once said mods are complete'd.
> 
> ...



Higher voltage is not a problem, so I would go with the Auricap.047, or .1uF 400v for the cathode bypasses. They will then compliment the sound of your Auricap coupling caps and should sound great!

I don't think they will fit though without extending the chassis which you could do by adding some aluminium heatsink sheets like Maxx and I did. But you mustn't shirk from bypassing your cathode caps, if you don't use bypasses the sound will suffer as a result as members here have found.


----------



## baronbeehive (Jan 20, 2018)

braaam said:


> ......
> 
> To me, the silver plate Mazda sounds more open than Mullards, with a more even balance and better extension at the top and less emphasis on the mids. They have their own unique sound signature, but if you like the GE’s you may want to give it a go if you can get a hold of one! They do share the openness and transparancy with the early 50s/60s GE tubes.



Well, my final, final tube rolling experiment has finished with trying the silver anode Mazda, and.... I have nothing more to say, I have no more need of tube rolling, audio nirvana is at hand, with the 2 Mazdas I recently got, this one and the Philiips-Mazda branded tube!!!


----------



## Makiah S

baronbeehive said:


> Higher voltage is not a problem, so I would go with the Auricap.047, or .1uF 400v for the cathode bypasses. They will then compliment the sound of your Auricap coupling caps and should sound great!
> 
> I don't think they will fit though without extending the chassis which you could do by adding some aluminium heatsink sheets like Maxx and I did. But you mustn't shirk from bypassing your cathode caps, if you don't use bypasses the sound will suffer as a result as members here have found.



What would you recommend for upgrades without extending the Chassis?


----------



## baronbeehive

Mshenay said:


> What would you recommend for upgrades without extending the Chassis?



I've just had a look at the dimensions of the .47uF Auricaps which are 17x20mm, as against the Jupiters in my APPJ which are 21x52mm, and the .047uF Auricap bypasses would be 11x14mm, therefore it's possible you could locate your bypasses somewhere by the end of the Auricaps because 20+14=34mm which is still less than the length of my Jupiters. Otherwise you could try something like these: https://www.hificollective.co.uk/catalog/0-1uf-275vdc-evox-rifa-pme271m.html
which are 7mm deep and may therefore fit over the Auricaps.

The best thing would be to open up the bottom and measure yourself to see what would fit and then get that.


----------



## Makiah S

What about the 


baronbeehive said:


> I've just had a look at the dimensions of the .47uF Auricaps which are 17x20mm, as against the Jupiters in my APPJ which are 21x52mm, and the .047uF Auricap bypasses would be 11x14mm, therefore it's possible you could locate your bypasses somewhere by the end of the Auricaps because 20+14=34mm which is still less than the length of my Jupiters. Otherwise you could try something like these: https://www.hificollective.co.uk/catalog/0-1uf-275vdc-evox-rifa-pme271m.html
> which are 7mm deep and may therefore fit over the Auricaps.
> 
> The best thing would be to open up the bottom and measure yourself to see what would fit and then get that.



What about the solen 0.1 ufs?


----------



## baronbeehive

Mshenay said:


> What about the
> 
> 
> What about the solen 0.1 ufs?



I don't know about that but I definitely think you could do what I said with the Auricaps, it might need a bit of jiggery pokery but should work going by the dimensions, but it's up to you to check before you go ahead and order.


----------



## Makiah S

baronbeehive said:


> I don't know about that but I definitely think you could do what I said with the Auricaps, it might need a bit of jiggery pokery but should work going by the dimensions, but it's up to you to check before you go ahead and order.



Good to know! At this point I'm trying to get the soldering done by some one else! I'm a little too busy right now and my soldering skills aren't quite up to par.

I'm hoping to have this little guy modded and show ready by February!


----------



## baronbeehive

Mshenay said:


> Good to know! At this point I'm trying to get the soldering done by some one else! I'm a little too busy right now and my soldering skills aren't quite up to par.
> 
> I'm hoping to have this little guy modded and show ready by February!



Do not delay.... this is worth it!!

The pic shows that the length of the Jupiter caps should allow for your Auricap/bypass cap end to end and you could take out one of those posts to make more room.


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## Makiah S (Jan 20, 2018)

baronbeehive said:


> Do not delay.... this is worth it!!
> 
> The pic shows that the length of the Jupiter caps should allow for your Auricap/bypass cap end to end and you could take out one of those posts to make more room.




Is that a single bypass cap in parallel with Both Cathode Electrolytics?

And "worth it" is moot, lol I'm more curious than "excited" I'm speaking with my... craftsman? I'll call him, or the Electrician maybe is the better word...

Anyways, getting a quote for a set of the panasonic 1500 uF with the WIMA .47uFs 400v with Solen .1 uF bypass, as well as for the Kasai's 1000 uF 25v with the Auricap .47 and .047s

Did some digging, and I think they AuriCap XOs are the way to go. If I'm going to go with "nicer" boutique stuff, though I'm not sure what really qualifies as "boutique" for caps

Either way, the work shouldn't take long so now it's just time to wait!

Well it's done! Parts have been ordered, came to $102 q.q half the cost of the amp, but I went with AuriCaps .47 400VDC with .047 400VDC Bypasses and the Audio Note KAISEI Non-Polarized 1000 uF 25VDCs. Hopefully I'll have it back by the first/second week of Febuary.

I've also asked the guy I'm working with about addressing the socket Tension/aggravation. He's actually a restoration guy from what I can see!


----------



## baronbeehive

Mshenay said:


> Is that a single bypass cap in parallel with Both Cathode Electrolytics?
> 
> And "worth it" is moot, lol I'm more curious than "excited" I'm speaking with my... craftsman? I'll call him, or the Electrician maybe is the better word...
> 
> ...



Yes go for the Auricaps! An hours work, no more.
The Kaisei's need to be the polarized version as that is what is already in the stock version
This is how I see it could work, auricaps where I've got the Jupiters with the 2 bypasses on end connected to the Kaisei cathode caps, simple!


----------



## baronbeehive (Jan 21, 2018)

For the connections you need to connect the negative terminal, or outer foil lead of the bypasses to the negative terminal of the Kaisei caps. I've show you the negative terminal of the Kaisei's, You will have to find out which is the negative, or outer foil lead on the Auricaps because they keep changing them and I don't know.
Also you need to connect the terminals of the Kaisei's to the correct points on the board, your connections are different to mine so you could go back and check Maxx134's pics to see how he did it.
The coupling caps can go in any way.
Let us know how it went!


----------



## Pratt99

Mshenay said:


> Yea I've not listened to this bad boi since October! Hooked everything back up today and I'm kinda impressed how well it does with my AKG K240 Sextett, though I am driving High gain out of my DAC and High Gain from the amp it self. Not sure if this is rated for a 600Ohm but it's doing pretty good.  JJ 6V6s Power Tubes and a Sylvania 12SL7GT Jan CHS vt289
> 
> The previous channel imbalances issues I had seem to be gone! In fact I'm really impressed with how well this handles stereo music, my K240 has a really nice cohesive sound stage! Quite impressive really. I've also reached out to a member here to have some Mods performed at a later date. I might just enjoy it stock for now since it seems to be working nicely! An check back in once said mods are complete'd.
> 
> ...


 Hi ,

Just saw your earlier post. Hope your caps upgrade went well! I saw that you are using JJ 6v6 power tubes and it alerted me. They made my GE12SL7GTs and TS5751 sound harsh, which I reported earlier in this thread. I thought the culprit was my HD600 initially. I upgraded them to RCA 6bg6 tubes and it made a massive difference. I do suggest you change them.


----------



## Makiah S

Pratt99 said:


> Hi ,
> 
> Just saw your earlier post. Hope your caps upgrade went well! I saw that you are using JJ 6v6 power tubes and it alerted me. They made my GE12SL7GTs and TS5751 sound harsh, which I reported earlier in this thread. I thought the culprit was my HD600 initially. I upgraded them to RCA 6bg6 tubes and it made a massive difference. I do suggest you change them.



Oh thank you! The JJ 6v6 are not permanent. Rather they are my messing around tubes, I have a set of Russian tubes that @Maxx134 recommended. An I have not  yet received my amp back from the cap upgrade! Though I may have the gentle re capping and modding the amp also address those nasty tube sockets as well while he has it


----------



## Makiah S

Just got my unit back today! Arrived cold so I let it sit un powered in my office while I finish my shift at work, don't want to start it cold



 

So I also installed my Russian Power Tubes [the previous Flavor of the Month lol] an I'll fire up my 12sn7 along with it here in the next 2 hours or so!
Other wise Cliff the gentleman who performed the mods did an excellent job! An I'm excited to hear it, I also just got a silver cable for my HD 800 so it should be a pretty big improvement over the last time I listened


----------



## Makiah S (Feb 5, 2018)

Sound is excellent, but the staging is a little shallow. Any recommendations for some clear power tubes with a deeper staging? I've got those russian 6f6c(s)   or what have you


----------



## Makiah S

Mshenay said:


> Sound is excellent, but the staging is a little shallow. Any recommendations for some clear power tubes with a deeper staging? I've got those russian 6f6c(s)   or what have you



I'm actually going to try another 12SL7GT, this time a 194X white Label without the nasty deposit on the top that mine has and a better matching, when I was rolling 6sn7s into my Ember that's what opened it up the most, a white Label 1940 Sylvania GT


----------



## baronbeehive (Feb 10, 2018)

Hey, good to see you've got the job done, looking great, those caps fitted perfectly!

For best sound the cable, especially if it's silver needs to be good quality, I would go for OCC silver, otherwise it can sound thin, or OCC copper if you like copper.

The power tubes are some of the best so I don't think you will get much better for soundstage. I don't know which 12SN7's you have but for driver tubes the one that stood out for me by a mile was the Philips/Mullard 12AX7 that I posted about recently, The stage was massive and incredibly detailed, and dynamic, and the most holographic I've heard. The sound may not be to everybody's taste, it is ultra powerful and realistic in the bass and mid regions and so might be a little dark sounding compared to some. I love it and it's one of my 3 top tubes now, the others being the TS5751, for well balanced smooth sound, and Mazda 12AX7 silver anode, for some of the best treble sound and open staging. I don't know about your Sylvanias, I've found them a little shallow but I know some love them, it might not be the best match with your HD800s, I don't know.

I know both Maxx and I have done comparisons of this amp to our heavily modded top performing headphone amps and we both love the APPJ, I found in some respects that the APPJ is even slightly better in some respects so there can be no doubt that the APPJ is top level post mods.

Edit: I got the Philips from here if you're interested, he's still selling them: https://www.ebay.com/itm/MAZDA-ECC8...=item590715e876:g:ef4AAOSw9idZ~bpq&rmvSB=true


----------



## Makiah S

I'll check out the Philips, I usually like Octals and find them to be pretty open especially compared to smaller 9pin, but I'll give a 9pin a shot for sure 

An yes! With mods it really opens up, I'm pretty impressed. My little Ember II is no longer on HD 800 duty, it's been left with my LCD 2.


----------



## Makiah S

baronbeehive said:


> Hey, good to see you've got the job done, looking great, those caps fitted perfectly!
> 
> For best sound the cable, especially if it's silver needs to be good quality, I would go for OCC silver, otherwise it can sound thin, or OCC copper if you like copper.
> 
> ...



As for my silver, yes it is indeed OCC Silver 



Mshenay said:


> I'll check out the Philips, I usually like Octals and find them to be pretty open especially compared to smaller 9pin, but I'll give a 9pin a shot for sure
> 
> An yes! With mods it really opens up, I'm pretty impressed. My little Ember II is no longer on HD 800 duty, it's been left with my LCD 2.



Speaking of driver tubes, I just got my replacement 12SL7GT Sylvania, and holy smokes I think this is genuinely New old stock, the silk screen print is phenomenally clear there's even the little anchor on the rear of the base, no grey deposits up top either! An holy MOLY does this thing scream!!! I'm giving mile's davis a listen an WHOA mamma... the horns really reach out an grab you... everything I like about a 40s white label Sylvania Octal lol, going to let it warm up a little more then swap back into my previous driver tube to see if there's any real difference


----------



## Maxx134

Mshenay said:


> Other wise Cliff the gentleman who performed the mods did an excellent job!


Yeah that is a really nice neat job!



baronbeehive said:


> The power tubes are some of the best so I don't think you will get much better for soundstage.


I agree and settled on my choice of power tube.
But if you want a larger Soundstage which is also very refined and excellent, go for the huge 6L6 type .
I found them good but a bit too laid back for me.


----------



## CZ4A

I've discovered another reason I like this amp - it can bias and operate with some very weak preamp tubes. I have an authentic Telefunken ECC803S in my tube stash that tests extremely weak for emissions on my tube tester. Like, almost dead. It works great in the APPJ and sounds just as sweet as its reputation suggests!


----------



## CZ4A (Mar 3, 2018)

I've hopped onto the 6BG6 bandwagon. I bought and finished building a pair of 6BG6 to 6L6 adapter kits from SND Tube Sales, then scrounged up a pair of strong-testing Tung-Sol 6BG6Gs from my stash. One is relabeled for Emerson and the numbers don't match, but after a couple of listening sessions swapping the tubes from side to side I'm not hearing a difference between the two. But wow, do they sound good with the Telefunken ECC803S driver! This combination is extremely detailed with some nice bass punch. The 6BG6s are quiet too, which hasn't always been my experience with Coke bottle shaped and top cap tubes. Some of my Coke bottle tubes are rather microphonic, and the plate wire on the 6F8G to 6DJ8 adapter for my Project Sunrise acts like an EMI antenna. Not the case with the Tung-Sols.






I have the parts to make an Loctal-to-octal adapter, so that will likely be my next project for this amp. However, I need to start selling off tubes first; I have waaaay too many!


----------



## baronbeehive

CZ4A said:


> I've hopped onto the 6BG6 bandwagon. I bought and finished building a pair of 6BG6 to 6L6 adapter kits from SND Tube Sales, then scrounged up a pair of strong-testing Tung-Sol 6BG6Gs from my stash. One is relabeled for Emerson and the numbers don't match, but after a couple of listening sessions swapping the tubes from side to side I'm not hearing a difference between the two. But wow, do they sound good with the Telefunken ECC803S driver! This combination is extremely detailed with some nice bass punch. The 6BG6s are quiet too, which hasn't always been my experience with Coke bottle shaped and top cap tubes. Some of my Coke bottle tubes are rather microphonic, and the plate wire on the 6F8G to 6DJ8 adapter for my Project Sunrise acts like an EMI antenna. Not the case with the Tung-Sols.
> 
> 
> 
> ...




Me too! I had no takers for my tubes which is a pity because they're only lying round here and not worth putting on ebay for what I would get for them. Never mind.

Glad to see people here still enjoying this little miracle! Mine is here for keeps. Why spend big bucks when you've got this!

I like the look of your amp, the fact that the 2 tubes are slightly different size gives it character lol.


----------



## CZ4A

baronbeehive said:


> Me too! I had no takers for my tubes which is a pity because they're only lying round here and not worth putting on ebay for what I would get for them. Never mind.



I have some that will sell for decent money on the auction site and am posting time when I have time. However, I've many more, mostly TV, tubes that are nearly worthless nowadays. I have an e-mail out to a local electronics recycler to see if they will take them for disposal if I decide to go that route. I also know of a couple of tube resellers that _may_ take them, but I don't expect much if they do.


----------



## Maxx134

There is a huge gapping hole in this website because there is no "tubes for sale" thread..
Many resort to ebay because of this


----------



## Maxx134 (Mar 14, 2018)

Pratt99 said:


> ...saw that you are using JJ 6v6 power tubes and it alerted me. They made my GE12SL7GTs and TS5751 sound harsh, which I reported earlier in this thread. I thought the culprit was my HD600 initially. I upgraded them to RCA 6bg6 tubes and it made a massive difference. I do suggest you change them.


The older RCA 6bg6  with double bottom getters and double wire/filament going to top pin,
 they are the best Ive tried.

They not easy to find either as most other tubes have a single filament going up to top pin.



Mshenay said:


> Sound is excellent, but the staging is a little shallow. Any recommendations for some clear power tubes with a deeper staging? I've got those russian 6f6c(s)   or what have you


I know you resolved this, but the 6bg6 are still better,
And one powertube that had the biggest Soundstage.
It was the 6L6 type tube.
Just a touch too distant so I put them away.
Lucky I did as now  switched back to them for specific reasons.



baronbeehive said:


> I know both Maxx and I have done comparisons of this amp to our heavily modded top performing headphone amps and we both love the APPJ


The APPJ only lacked in a bit of holography and Soundstage.
I recently aquired the Abyss Diana, which has an unreal resolve but also a more intimate presentation.
In combination with the naturally lively tube setup on the APPJ it was amazing but closer...

So I popped in my 6L6 power tubes again,
and now I have a correct soundstage presentation, with "more" holographic Soundstage than before (!) And with enough power to push the Diana.

So the bit distant 6L6 balanced out the bit forward headphone into a larger Soundstage...

Rediculous using a $200 APPJ on a $3K Headphone right?
Lol, no of you using a yggy,
 And if you heard it your brain would have serious conflict how can this little amp sound so good!


So now I must compare the APPJ to my main amp.

The point is that you can roll so many tube combination,
that you can adjust this amp to fit your needs for "system synergy".
Not many amps can roll both driver and power stages.


----------



## baronbeehive (Mar 17, 2018)

Maxx134 said:


> The APPJ only lacked in a bit of holography and Soundstage.



Yes, my speaker APPJ is excellent, but the Little Dot excels in this. I don't have the choice of power tubes you have but no matter the Amperexe's are excellent. But I had a problem with soundstage because of the shape of my room all the sound appeared to be coming from one corner of the room so I adjusted the power tubes so that I had a stronger one on one side and that has greatly extended the soundstage to room width, and also excellent depth with the Philips tubes!



Maxx134 said:


> I recently aquired the Abyss Diana, which has an unreal resolve but also a more intimate presentation.
> In combination with the naturally lively tube setup on the APPJ it was amazing but closer...
> 
> So I popped in my 6L6 power tubes again,
> ...



As a side issue to this amp, I had a similar problem with the HE-500's which have a small soundstage and it is close up and intimate like yours however not the resolve of yours. I like the close presentation because you feel intimately involved with the music but the heaphones are musical but do not have the resolve which is a side note as to why they don't quite perform with the other amp



Maxx134 said:


> So now I must compare the APPJ to my main amp.



Look forward to hearing your impressions. As I've said the APPJ outperforms the Little Dot in respect of articulation - leading edges and musical liveliness atm, (there are other things I will be able to do to the other amp yet to change this though). But as you say who in their right mind would pair such a lowly amp as the APPJ with other components costing thousands.... more fool them lol.

Re: tubes I see no reason to change, I have my perfect setup with the Philips, wonderful soundstage, and the Mazdas, incredibly musical treble and taughtness, top notch sound.... amazing. The other tubes I tried all had their good points, for example the 12SL7 GE's, excellent transparency but just a little thin on this amp, other tubes were also good but nothing matches up to what I have now.

Oh BTW can I have your HEK's now that you've finished with them LOL.


----------



## Maxx134 (Jun 6, 2018)

I have compaired the baby Appj amp to my moded Little Dot Mk8, the Edddie Current Aficionado, and the Cayin HA-300...

Those are all end game level amps.

They all have larger, more 3D soundstage,
And a slight increase in resolve.
To be honest, I was quite shocked the mini Appj amp did so dam well.
It has almost as good a resolve, but way less soundfield.

So now I am re-evaluating my tube selections, to try gain a similar soundStage.

If i had choice, I would not get the audyn cooper for coupling caps, but instead the clarity cap CMR.
Cheaper and more natural/balanced than all mundorf and more soundstage over the Audyn copper,
 although the Audyn prob has more immediate mids.

Anyways, I will see if a Kt66 or 6L6 can get the soundStage back up.

So The issue with the other tubes was they were impressing us with details, while sacrificing sounstage for more closer presentation,
And thats something not as noticable with speakers or without comparisons.


----------



## baronbeehive (Jun 9, 2018)

Maxx134 said:


> I have compaired the baby Appj amp to my moded Little Dot Mk8, the Edddie Current Aficionado, and the Cayin HA-300...
> 
> ….
> So The issue with the other tubes was they were impressing us with details, while sacrificing sounstage for more closer presentation,
> And thats something not as noticable with speakers or without comparisons.



Very interesting Maxx! The soundstage issue is difficult with headphones, you want enough distance to get in the soundstage realism but not too much that you lose contact with the musical impact.

I don't know how the Jupiter caps compare with the Audyns for soundstage, all I know is that it is excellent but as you say difficult to compare with my speaker setup. I do know that with the Jupiters though the soundstage is nice and airy sounding with great resolve.

It's that good I have stopped listening to the amp and now only listen to music. When I have done direct comparisons to the LD MkVI the impressive soundstage of the LD is always immediately noticeable, separation second to none, but the APPJ is very good, extending to room width and good depth too. I haven't compared lately because I'm still waiting on a few parts for the LD which is out of action atm.

I can't give suggestions for power tubes as I still use my Amperex EL84's but I mentioned before the driver tubes I use now all the time: Philips ECC83, most 3d soundstage I've heard, and Mazda 12AX7 silver anode, very open soundstage. They're in a different league to the others IMO.

Maybe worth a try, I don't know if they increase the actual soundstage though.

I know I've said this before but what I love about the APPJ, as well as the sound, is that the transients have a tactile quality that jumps out at you that makes the presentation incredibly realistic sounding.

Edit: I wonder what those other amps have inside them regarding quality components?


----------



## Maxx134 (Jun 9, 2018)

baronbeehive said:


> the impressive soundstage of the LD is always immediately noticeable, separation second to none,


Mine is second to those two other amps I mentioned because I am using some old "vitamin Q" caps which I need to update.
They do sound nice but its time to move onto top sounding caps like Jupiter.




baronbeehive said:


> : I wonder what those other amps have inside them regarding quality components?


They have good quality.
One Using russian caps and other using Mundorf,
So although not top boutique level caps (no amp does) they both good enough to instead worry more about the tube selection, which is more important overall.

Like this amp as well, basically matching the tube to the amp according to how you want it to sound..

I recently got a Holo Spring Dac and it is super life-like & lively with larger soundstage which matches all these  tube amps very well...


----------



## Peekeesh

hello! got in on the massdrop deal for this amp. for $140, i think that's a good price. i'm excited and couldn't wait to get it and start modding. ETA is mid-august. Anyway, I have already bought the following:

ELNA CAP ALUM 1000UF 20% 25V RADIAL SILMIC II
Mundorf .47uf M cap supreme

I plan to listen to it for a couple of days with the stock caps then will replace them. For the tubes, i might get the tungsol KT66. 

You guys still have this amp or have ya'll upgraded to something more high end?


----------



## DavidK35

Peekeesh said:


> hello! got in on the massdrop deal for this amp. for $140, i think that's a good price. i'm excited and couldn't wait to get it and start modding. ETA is mid-august. Anyway, I have already bought the following:
> 
> ELNA CAP ALUM 1000UF 20% 25V RADIAL SILMIC II
> Mundorf .47uf M cap supreme
> ...



It's already high end (with some mods/tube rolling), only those with upgraditus would want to move on to something else.


----------



## Peekeesh

DavidK35 said:


> It's already high end (with some mods/tube rolling), only those with upgraditus would want to move on to something else.



Gotcha.. would you recommend a tube that will pair nicely with the kt66? 12ax7 Or a valvo e180cc? Or should i get a different set of tubes?

I'll be using hifiman he560.


----------



## DavidK35

Peekeesh said:


> Gotcha.. would you recommend a tube that will pair nicely with the kt66? 12ax7 Or a valvo e180cc? Or should i get a different set of tubes?
> 
> I'll be using hifiman he560.




Personally I don't rate the 12AX7 very highly. I prefer the 12AT7 series, my preferred one is the little known 6211A which has a lower AF (price is cheap too, no hype attached). However after extensive trials & listening sessions I have found the 14 locktal series to be the best (adaptor required) finally settling on the 14N7 as it suits my tastes best (smooth, detailed etc). You will find a lot of different opinions though, we all have different tastes & this amp accomodates them well. Best to go back in the thread  & check it out, a lot of tubes have been tried.


----------



## Maxx134 (Jul 28, 2018)

Peekeesh said:


> hello! got in on the massdrop deal for this amp. for $140, i think that's a good price. i'm excited and couldn't wait to get it and start modding. ETA is mid-august. Anyway, I have already bought the following:
> 
> ELNA CAP ALUM 1000UF 20% 25V RADIAL SILMIC II
> Mundorf .47uf M cap supreme
> ...


Your cap choices will pit it's signature on the sweet, detailed side.
Very nice.



Peekeesh said:


> Gotcha.. would you recommend a tube that will pair nicely with the kt66? 12ax7 Or a valvo e180cc? Or should i get a different set of tubes?
> 
> I'll be using hifiman he560.


The HE560 was a great well rounded headphone when I owned it.
This amp should power it nicely, especially once moded brings out the bass from stock which is a bit lean.

I keep my APPJ amp as a backup amp,
 and to burn in a new tube..

As its great for a small sized amp with above average performance.

Also don't buy the tung-sol KT66 bottle,
I have them and can be a tad "soft", but good soundstage.

Instead,
 I have settled on the gold-lion.


Name sounds extravagant,
but it is a great reissue remake of the famous  Genalex tube:

https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.com/ulk/itm/161982192487

And has the lower heater specs of the new tubes,
Rather than the old stock kt66 with higher heater draw.

Regardless, those tubes run hotter than most all the others I have tried.
They have the largest soundstage while also retaining the clarity,
Which is hard to do without loosing presence.
My best NU 6L6 had biggest stage but suffered a touch of distance, and some  "presence" loss.

The Tung-sol kt66 had as big a sounstage but suffered more in presence.

The gold-lion not only beats them out in stage, but does not suffer in presence or detailing,
But it does "add" a very slight touch of extra flavor to its sound, so it is not a neutral lean tube.


For driver tube, I am in agreement with "DavidK35" .
Although I also like some  9-pin as well for euphony.
But for resolution, I pick same driver tube 14n7 type with adapter.
Just barely fits together with those big KT66 bottles...


----------



## Maxx134

Added more info to tube sound above,
My other fav tubes are the very highly detailed, very old RCA 6bg6 type.
Incredibly resolving but I wanted to increase soundstage to catch up to the best amps.
I will need to upgrade my coupling caps as the audyn copper does not have end-game level soundstage. It does have a really natural and resolving sound  though.


----------



## Peekeesh (Jul 26, 2018)

@Maxx134  i was backreading and CZ4A said that for kt66 tube, tungsol is recommended just  because the draw is .9 a. Other kt66 tubes pull 1.3a.

https://www.head-fi.org/threads/any...une-appj-pa1502a.780178/page-15#post-12521319

If those genalex kt66 work great and won't damage the amp, then im down to try them. 

By the way, would you mind posting a link to where i can purchase the adapter to make the 14n7 fit? Also which 14n7 tube will you recommend?

I'm new to all this. I actually got the he560 v2 that was on sale a couple of days ago. I love how it sounds. Currenty pairing it with a topping d10 and a nobsound ns08. Hehe.. underpowered but i like what i hear so far.


----------



## Peekeesh

Is this the adapter?

https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.com/ulk/itm/201006223709

And the tube?

https://tubedepot.com/products/14n7


----------



## DavidK35

Peekeesh said:


> Is this the adapter?
> 
> https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.com/ulk/itm/201006223709
> 
> ...



That is the right adaptor but it looks ugly without the outer sleeve IMO. The same supplier will do one for you with a gold outer sleeve for an extra $5. (xulingmrs,china, on ebay) just ask him.


----------



## baronbeehive (Jul 26, 2018)

Peekeesh said:


> hello! got in on the massdrop deal for this amp. for $140, i think that's a good price. i'm excited and couldn't wait to get it and start modding. ETA is mid-august. Anyway, I have already bought the following:
> 
> ELNA CAP ALUM 1000UF 20% 25V RADIAL SILMIC II
> Mundorf .47uf M cap supreme
> ...



Is your APPJ the same version as the one on this thread, there have been newer versions of some models.

You will need bypass caps for your Elna cathode caps, otherwise you will be disappointed as we have been without them. Look back in the thread.



DavidK35 said:


> It's already high end (with some mods/tube rolling), only those with upgraditus would want to move on to something else.



Correct. I've been cured of that for some time now!


----------



## baronbeehive

Maxx134 said:


> The gold-lion not only beats them out in stage, but does not suffer in presence or detailing,
> But it does "add" a very slight touch of extra flavor to its sound, so it is not a neutral lean tube.



I've been interested in the Gold Lions but not tried them.


----------



## Peekeesh (Jul 26, 2018)

baronbeehive said:


> Is your APPJ the same version as the one on this thread, there have been newer versions of some models.
> 
> You will need bypass caps for your Elna cathode caps, otherwise you will be disappointed as we have been without them. Look back in the thread.



I joined this drop. I haven't gotten it yet but massdrop says it will ship mid august.

https://www.massdrop.com/buy/appj-1502a-tube-headphone-amplifier/talk#discussions

How do i determine if I'm going to need bypass caps? what bypass caps would you recommend? Thanks!!




DavidK35 said:


> That is the right adaptor but it looks ugly without the outer sleeve IMO. The same supplier will do one for you with a gold outer sleeve for an extra $5. (xulingmrs,china, on ebay) just ask him.



Thanks. I sent the seller a message.


----------



## baronbeehive (Jul 26, 2018)

Peekeesh said:


> I joined this drop. I haven't gotten it yet but massdrop says it will ship mid august.
> 
> https://www.massdrop.com/buy/appj-1502a-tube-headphone-amplifier/talk#discussions
> 
> How do i determine if I'm going to need bypass caps? what bypass caps would you recommend? Thanks!!



Maxx and I used Audyn True Copper MKP 0.1uF film cap to speed up response times and cover the frequencies lost with the electrolytic cap. The problem is that with the 1000uF electrolytic cathode caps they do provide efficient recovery time from power drains …. BUT … you lose top end sparkle which is why you need the lower capacitance bypass caps.

However they won't fit in the chassis unfortunately so we had to extend the bottom to accommodate them. You can see how we did it around page 19 on this thread. However for sound it was well worth it.


----------



## Peekeesh

Thanks @baronbeehive I saw the post.  to be sure, the bypass caps are polarized and needs to be soldered to board the same way the cathode caps are?


----------



## baronbeehive (Jul 26, 2018)

Peekeesh said:


> Thanks @baronbeehive I saw the post.  to be sure, the bypass caps are polarized and needs to be soldered to board the same way the cathode caps are?



The Audyn film caps have a little arrow on one side and this needs to be connected to the negative terminal of your cathode cap, the other terminal from the Audyn cap to the other terminal of the cathode cap so that it is bypassing the cathode cap. The end of the cathode cap terminals are then soldered to the board as shown in the pics in the thread.

Edit: You could of course use other film bypass caps such as PME-080: 0.1uF 275Vdc Evox Rifa PME271M Metallized paper which may or may not fit without extending the bottom.

Good luck with your mods!


----------



## Peekeesh

I purchased 2 solen caps .1uf 630v, gonna use them as bypass caps, 14n7 NOS from tube depot and the adapter from ebay. I'll get the kt66 golden lion later once I determined it's safe to run them.


----------



## baronbeehive

Peekeesh said:


> I purchased 2 solen caps .1uf 630v, gonna use them as bypass caps, 14n7 NOS from tube depot and the adapter from ebay. I'll get the kt66 golden lion later once I determined it's safe to run them.



Sounds good, as long as the solen's are film caps for that extra fast response over the electrolytics.


----------



## Maxx134 (Jul 28, 2018)

Peekeesh said:


> How do i determine if I'm going to need bypass caps? what bypass caps would you recommend? Thanks!!


Since the cathode caps are cheap, it makes betybe sense to get electrolytics that are either known or meant to be  "audio quality"...

So ditch those electrolytics you memtiment,
 for either "Kaisie" caps, or other known Better ones,
like  Jensen "audio grade" caps...

Cheaper than trying to fix with bypass.

Still with a size of 1000uf,
I would still add a bypass.

If it were 330uf or less, I wouldnt bother.

Yet, Since we trying to push this amp performance,
A bypass cap of small size is still recommended.

Even smaller than .1uf is good for bypassing with  the better "audiofile" electrolytics, like even half value of that.
We just helping the top end transients..

Just ballpark figures are ok,
wich are usually same with many similar designs..

I have to redo my other main amp like this to try boost its performance more...


----------



## baronbeehive (Jul 29, 2018)

Maxx134 said:


> I have to redo my other main amp like this to try boost its performance more...



Me too! I have 2 spare Kaisei caps which I could use on the other amp although they're only 25v, as compared to the 63v Ecap I have in now, I think they might be ok.



Maxx134 said:


> Even smaller than .1uf is good for bypassing with  the better "audiofile" electrolytics, like even half value of that.
> We just helping the top end transients..



The top end transients on this amp, just right, they have an edge that is palpable but I feel that anything sharper than this would be borderline sybillant on my speaker APPJ, (APPJ PA0901A), I don't know about yours, so I wouldn't go less than 0.1uF on mine. But those bypasses have to be there, without them the top end transients don't exist at all which you don't want because the sound is lifeless.

The transients are helped by my tube choice, with my previous favourite the TS 5751 the details were good but the transients were somewhat rounded off in that fabulous Tungsol liquid sounding way which made for great listening and they had a magical quality to the sound which no other tube had. But after hearing my latest fav tubes, the Philips 12ax7 and Mazda 12ax7, actually ECC83 since they are European made, the transients are that much sharper and more real anyway without any detriment overall SQ, and they have other qualities which raise them above others I tried IMO. I'm completely sold on these now although I've tried many good tubes on this amp.

I continue to be shocked by this little baby! Frankly I wouldn't change anything, it has reached top level for me.


----------



## baronbeehive (Jul 29, 2018)

Peekeesh said:


> hello! got in on the massdrop deal for this amp. for $140, i think that's a good price. i'm excited and couldn't wait to get it and start modding.



Just a thought, but to anyone intent on modding the amp it is a good idea to check over the solder connections and wires after you've finished your mods, including the existing wires that can break off, before you start on the listening fun. If you can't do that then get someone who is experienced in electrononics to check it over.

If I hadn't done that mine would have gone up in smoke LOL. One or 2 on this thread lost their amp because of this, and the amp can be damaged on the PCB if you are not careful. But take care and you should be fine.


----------



## baronbeehive

baronbeehive said:


> Me too! I have 2 spare Kaisei caps which I could use on the other amp although they're only 25v, as compared to the 63v ECaps I have in now, I think they might be ok.
> 
> 
> 
> ...


----------



## baronbeehive (Jul 29, 2018)

baronbeehive said:


> Me too! I have 2 spare Kaisei caps which I could use on the other amp although they're only 25v, as compared to the 63v Ecaps I have in now, I think they might be ok.
> 
> 
> 
> ...



Sorry for the double-triple post!


----------



## Pratt99

baronbeehive said:


> Me too! I have 2 spare Kaisei caps which I could use on the other amp although they're only 25v, as compared to the 63v Ecap I have in now, I think they might be ok.
> 
> 
> 
> ...



@baronbeehive  For the Philips 12ax7 and Mazda 12ax7, what would be a fair price to pay? I see they command a premium price, but I am interested in trying one. Thanks.


----------



## baronbeehive

Pratt99 said:


> @baronbeehive  For the Philips 12ax7 and Mazda 12ax7, what would be a fair price to pay? I see they command a premium price, but I am interested in trying one. Thanks.



For the Philips I was lucky to pay about £30 from a UK seller so no customs charge or VAT, I would try and find something around $60. For the Mazda silver anode I think I paid around $65. I have seen them going for around $75 on Ebay by Brent Jesse who is a reputable seller and sells them on his own website for much more than this. I wouldn't pay silly money, I'm talking hundreds of dollars, just wait for one to come up at a reasonable price and NOS testing.

I would be happy to go for either of these:
https://www.ebay.com/itm/2x-ECC83-1...357459?hash=item41dff6a4d3:g:lUUAAOSwmuVaX6pz

https://www.ebay.com/itm/ECC83-12AX...916737?hash=item2143a6aa01:g:1ZsAAOSw7mpbS3XB

The Philips is one of the better earlier versions from the 1950's and 1960's, with the larger ring getter and has the delta symbol indicating Philips Herleen factory Holland, and is branded Valvo which is the Philips brand for Germany. Mine is branded Mazda.

The Mazda silver anode is the same as the one I've got, there are several versions with different plate construction but I imagine they sound similar.

The Mazda has a wonderful light airy musical sounding treble to die for and a nice tight bass.

The Philips is richer sounding but with incredible extended bass and treble, both very balanced sounding.

They are quite expensive but don't forget if you don't like them you can always resell them.

Let us know how you get on, I would be interested in how they sound on your amp in comparison to mine!


----------



## Maxx134 (Jul 30, 2018)

According to him, he  could save money going for the adapter plus 14n..


Peekeesh said:


> Is this the adapter?
> 
> https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.com/ulk/itm/201006223709
> 
> ...






DavidK35 said:


> Personally I don't rate the 12AX7 very highly. I prefer the 12AT7 series, my preferred one is the little known 6211A which has a lower AF (price is cheap too, no hype attached). However after extensive trials & listening sessions I have found the 14 locktal series to be the best (adaptor required) finally settling on the 14N7 as it suits my tastes best (smooth, detailed etc). You will find a lot of different opinions though, we all have different tastes & this amp accomodates them well. Best to go back in the thread  & check it out, a lot of tubes have been tried.


I personally am in  agreement with everything said in this post.

Also, I do like some 9pin tubes regardless for signature, but for resolution I still believe the 14type loctals are a bit above and way cheaper.


----------



## baronbeehive (Jul 31, 2018)

Oh no..... here we go again….. maybe I should try the 14N7's, I haven't tried them. I am in partial agreement with you about the 14F7's, great details, great tubes but slightly neutral for me as I remember. They didn't have the punch and rich sound of the Philips or the sweet addictive treble of the Mazdas.

I am still in shock over the 2 12AX7's I have, like the rest of you I rejected these tube types a while ago - some like these European ECC83 types better than the 12AX7's though - but frankly I can't see anything replacing them in my system now!

Lets see what Pratt99 thinks, in the meantime I might have to acquire those 14N7's....

.

Edit: Hmmmm…. might have to put off the purchase, not many 14N7's around....


----------



## Maxx134

baronbeehive said:


> The transients are helped by my tube choice, with my previous favourite the TS 5751 the details were good but the transients were somewhat rounded off in that fabulous Tungsol liquid sounding way which made for great listening and they had a magical quality to the sound which no other tube had. But after hearing my latest fav tubes, the Philips 12ax7 and Mazda 12ax7, actually ECC83 since they are European made, the transients are that much sharper and more real anyway without any detriment overall SQ, and they have other qualities which raise them above others I tried IMO. I'm completely sold on these now although I've tried many good tubes on this amp.


I probably will have to check these out as you previously liked the same 5751 that I also liked.
Your different type of  output tubes probably also play a part in your tube choice.
Yep its mix & match with any combo.


----------



## Maxx134

baronbeehive said:


> They didn't have the punch and rich sound of the Philips or the sweet addictive treble of the Mazdas.


I agree as I think most all 12*** 9pins have more harmonics over the more neutral 14loctals.



baronbeehive said:


> Edit: Hmmmm…. might have to put off the purchase, not many 14N7's around....


Actually I bought that one but still on my 14F7.


----------



## baronbeehive (Jul 31, 2018)

Maxx134 said:


> I probably will have to check these out as you previously liked the same 5751 that I also liked.
> Your different type of  output tubes probably also play a part in your tube choice.
> Yep its mix & match with any combo.



Yes, the EL84's are said to be a bright tube, probably explains why the 12SL7 GE's were a tad sharp on this amp, but not on the other one.

Re: the Philips and Mazda 12ax7's, I think there are probably exceptions to any rule, the Amperex 12ax7 is also said to be better than most.


----------



## DavidK35

baronbeehive said:


> Oh no..... here we go again….. maybe I should try the 14N7's, I haven't tried them. I am in partial agreement with you about the 14F7's, great details, great tubes but slightly neutral for me as I remember. They didn't have the punch and rich sound of the Philips or the sweet addictive treble of the Mazdas.
> 
> I am still in shock over the 2 12AX7's I have, like the rest of you I rejected these tube types a while ago - some like these European ECC83 types better than the 12AX7's though - but frankly I can't see anything replacing them in my system now!
> 
> ...




14N7 @ $5.90ea

14AF7 @ $7.90ea

https://www.tubesandmore.com/search/node/14n7?in=body

14F7 @ $4.25ea

https://vacuumtubesinc.com/index.php/catalogsearch/result/?cat=17&q=14F7


----------



## baronbeehive (Jul 31, 2018)

DavidK35 said:


> 14N7 @ $5.90ea
> 
> 14AF7 @ $7.90ea
> 
> ...



Thanks!

When I looked on ebay there were only 2 there, both RCA's.

You're not helping me with my addiction, which I thought was cured LOL.

Just one more possibility now we are on the subject, I might get some Mullard EL84's, not  that I'm not completely happy with  my existing  setup you  understand! Just that I may push boundaries, like Maxx134 is doing. The Mullards are said to give a big soundstage, might  be worth considering... but I can't  really see how this could get any better.


----------



## DavidK35

baronbeehive said:


> Thanks!
> 
> When I looked on ebay there were only 2 there, both RCA's.
> 
> ...




I am a big fan of NOS Mullard tubes, but that one has a different pin out, do you have adaptors?
If you go that way let us know how it compares.


----------



## Mecii

Maxx134 said:


> OK here are some pics of my internal/external mod:
> 
> ...
> 
> ...


Trying to track down a place to purchase the Audio Note caps. Can you tell me where you purchased yours from or where I might be able to purchase these?
Thank you.


----------



## Mecii

Mecii said:


> Trying to track down a place to purchase the Audio Note caps. Can you tell me where you purchased yours from or where I might be able to purchase these?
> 
> Parts Connection is out of stock and will not have them in for a least 3 weeks. Hoping to find another source.
> Thank you.


----------



## baronbeehive (Jul 31, 2018)

DavidK35 said:


> I am a big fan of NOS Mullard tubes, but that one has a different pin out, do you have adaptors?
> If you go that way let us know how it compares.



I will!

It's a power tube on my amp, not for the driver, I don't know if it would work there, I know the Russian Kobra's don't work for the power stage on my amp for example. Funnily enough the Mullard 12ax7's - ECC83's - I tried a while back weren't very good! Trouble is there are so many different Mullards, I should have tried them all.... especially the long plates, more difficult to get hold of though.

Anyway I'm happy with the Philips which braaam said he liked better than most Mullards, and Philips UK brand is Mullard anyway. There are some differences between the 2 types which mostly break down to overdriven sounds for guitarists.

Really though the soundstage is already good on my amp, it's just looking at small tweaks now which I don't know if I will bother with atm, I really am happy with it now!!

Edit: I will see if there is an adapter.


----------



## baronbeehive

Mecii said:


> Trying to track down a place to purchase the Audio Note caps. Can you tell me where you purchased yours from or where I might be able to purchase these?
> Thank you.



Where are you based?


----------



## Mecii

baronbeehive said:


> Where are you based?


USA - Wisconsin


----------



## baronbeehive

Mecii said:


> USA - Wisconsin



Maybe the others will know for the US, in Europe we usually use HiFiCollective.


----------



## baronbeehive

DavidK35 said:


> I am a big fan of NOS Mullard tubes, but that one has a different pin out, do you have adaptors?
> If you go that way let us know how it compares.



There don't appear to be adapters. Just as well I don't know if pentodes and twin triodes are compatible, so unless anyone knows differently I won't be using the EL84's as drivers. I'm still debating whether to try the Mullards in the power stage, not sure about their sound as power tubes.


----------



## Mecii

Mshenay said:


> Just got my unit back today! Arrived cold so I let it sit un powered in my office while I finish my shift at work, don't want to start it cold
> 
> 
> 
> ...





Mecii said:


> Trying to track down a place to purchase the Audio Note caps. Can you tell me where you purchased yours from or where I might be able to purchase these?
> Thank you.





baronbeehive said:


> Maybe the others will know for the US, in Europe we usually use HiFiCollective.


Well it seem this is a popular little cap since so far every place that carries these are on back order. Is there a substitute cap that would work in place of the KAISEI that is the same or better quality?


----------



## Peekeesh

Just curious, if you replace the power tubes with something bigger and more powerful, will that give you more juice to drive some power hungry headphones?


----------



## DavidK35

Peekeesh said:


> Just curious, if you replace the power tubes with something bigger and more powerful, will that give you more juice to drive some power hungry headphones?




There is a limit to what you can run. Personally I would not go over 0.9A current draw. That still leaves a lot of choices,
6L6G or 6BG6G for example. Seriously you would not want to go bigger than that, not practical,the amplifier is the limiting factor.


----------



## Peekeesh (Aug 1, 2018)

DavidK35 said:


> There is a limit to what you can run. Personally I would not go over 0.9A current draw. That still leaves a lot of choices,
> 6L6G or 6BG6G for example. Seriously you would not want to go bigger than that, not practical,the amplifier is the limiting factor.



Is this good?

https://tubedepot.com/products/6bg6g-ga

Or do i have to find a specific brand?

also, do i need some sort of adapter for the 6bg6g?


----------



## baronbeehive

I'm not sure but it looks like your amp has been discontinued, my speaker version has been upgraded a while ago, don't know what you guys think about that.


----------



## DavidK35

baronbeehive said:


> I'm not sure but it looks like your amp has been discontinued, my speaker version has been upgraded a while ago, don't know what you guys think about that.



Sad, but nothing lasts forever. Don't know but looks like the replacement is this with usb & some obscure 7 & 9 pin tubes:

https://www.aliexpress.com/item/GD-...r-Smart-Desktop-Wifi-SD-Card/32811062445.html

Amazon & some dealers on e-bay still have the original. Better hurry if anyone is thinking about buying it.


----------



## DavidK35

Peekeesh said:


> Is this good?
> 
> https://tubedepot.com/products/6bg6g-ga
> 
> ...



Yes, those tubes are fine. You will need to go to e-bay & look up tube adaptors for 6BG6G. The G version tubes are worth seeking out
over the GA type.


----------



## baronbeehive (Aug 2, 2018)

DavidK35 said:


> Sad, but nothing lasts forever. Don't know but looks like the replacement is this with usb & some obscure 7 & 9 pin tubes:
> 
> https://www.aliexpress.com/item/GD-...r-Smart-Desktop-Wifi-SD-Card/32811062445.html
> 
> Amazon & some dealers on e-bay still have the original. Better hurry if anyone is thinking about buying it.



Yes!

There's also this high end model:

https://www.amazon.co.uk/Nobsound-R...1?ie=UTF8&qid=1533235090&sr=8-1&keywords=appj

.... the replacement for mine:

https://www.amazon.co.uk/PA1501A-6A...2?ie=UTF8&qid=1533235090&sr=8-2&keywords=appj

... and this rather odd looking one:

https://www.amazon.co.uk/Nobsound-V...4?ie=UTF8&qid=1533235090&sr=8-4&keywords=appj

... none of them appear to be headphone amps!

I don't want any of these after perfecting the original with the mods we've done here!! Luckily it looks like the amp is reliable, I've had mine for at least 5 years, but what happens if one of the surface mount parts, or the SMPS goes west?


----------



## Pratt99 (Aug 3, 2018)

baronbeehive said:


> For the Philips I was lucky to pay about £30 from a UK seller so no customs charge or VAT, I would try and find something around $60. For the Mazda silver anode I think I paid around $65. I have seen them going for around $75 on Ebay by Brent Jesse who is a reputable seller and sells them on his own website for much more than this. I wouldn't pay silly money, I'm talking hundreds of dollars, just wait for one to come up at a reasonable price and NOS testing.
> 
> I would be happy to go for either of these:
> https://www.ebay.com/itm/2x-ECC83-1...357459?hash=item41dff6a4d3:g:lUUAAOSwmuVaX6pz
> ...


@baronbeehive Thanks much for this info. I have setup some ebay search alerts for these. It is true that it will be easier to resell these in ebay in the case that I  don't like coz these are known names in the tube world. My current favourite is telefunkun ( branded as  dynaco and fisher) 12ax7 and I got them for 25 dollars. They have a nice flat response, great transparency and goes well with my hd600. Will report back if I manage to buy the Philips or Mazda. Also saving some cash to upgrade my  Schiit Bifrost sigma delta to multibit. I believe that should improve resolution from the DAC end.


----------



## baronbeehive (Aug 4, 2018)

Pratt99 said:


> @baronbeehive Thanks much for this info. I have setup some ebay search alerts for these. It is true that it will be easier to resell these in ebay in the case that I  don't like coz these are known names in the tube world. My current favourite is telefunkun ( branded as  dynaco and fisher) 12ax7 and I got them for 25 dollars. They have a nice flat response, great transparency and goes well with my hd600. Will report back if I manage to buy the Philips or Mazda. Also saving some cash to upgrade my  Schiit Bifrost sigma delta to multibit. I believe that should improve resolution from the DAC end.



No problem!

Don't forget to get the type I posted, there are several different types, and brands and the only way you can know it's Philips is the delta symbol which braaam told me about. I've been listening again to mine and decided not to change again for anything else, this tube has everything for me and superb detail for a 12ax7, ECC83 type, maybe because it's a European tube with different sound to some others, also I believe the earlier versions to be the best. I don't know if you'll like it, it's way different type of sound to the Telefunken, which I have to say I didn't like, I don't like neutral tubes usually! Nevertheless it would be interesting to try the Philips with your HD600, I've found it to have the best soundstage of any I've tried. The Mazda is lighter sounding but I can't get rid of this tube as the treble is so good as I've said.

Edit: I think you might get better layering on the soundstage whereas the Tele's would be flatter, though clearer. I found the 12SL7 GE's to be transparent and flat like this but they worked a treat on my other amp which already had good layering.


----------



## Rick_B (Aug 4, 2018)

Peekeesh said:


> I joined this drop. I haven't gotten it yet but massdrop says it will ship mid august.
> 
> https://www.massdrop.com/buy/appj-1502a-tube-headphone-amplifier/talk#discussions
> 
> ...



I joined this one, too, and got my amp yesterday...I got shipping notification Wednesday that it was being sent from Hong Kong...arrived here at around 1:00PM local time...two days from Hong Kong to Texas, wow!

I've got it running this morning in my Ham Radio room, listening to my HE-400i's with a MyDAC hooked up to the APPJ with Wireworld Eclipse 8 cables, feeding it from this computer and JRiver via Audioquest Carbon USB cable, and using a home made braided SPC copper braided power cord....installed some NOS Sylvania 6V6GTA "coin base" tubes with a Great Britain manufactured 12AX7 (haven't looked deeply into who makes this one) after running it about an hour with the stock tubes...but, swapped that 12AX7 out just now with a NOS RCA 12AY7 and gained some definition that was glossed over by the previous tube...I've got several other flavors of 6V6 tubes in one of my packed storage units so I'll have to go mining there this weekend...

I think I may like this one better, or at least as much, as my Antique Sound Labs MG-Head OTL MarkIII DT.  I'll also need to compare it to my Darkvoice with NOS tubes and my Little Dot with Western Electric 403A tubes and a Burson V5i opamp...

I can't wait to let this thing run in for a couple of weeks, and then start with a few little mods, I have some Black Gate 330mfd@25V caps I'll use for the cathode bypass caps, I'll probably bypass them with a couple of .01mfd Auricaps I have if I don't use Sprague Vitamin Q .012@400V oil caps...I also have some Gudeman .51@300V Vitamin Q type oilers that I may try as coupling caps...

It's all fun and games...

P.S.  I like how this site classifies me as a New Head Fi'er after joining over a decade ago!  I lurk, I guess, and learn from others and only contribute if I have something salient to say.  Glad this forum exists!


----------



## baronbeehive

Rick_B said:


> I joined this one, too, and got my amp yesterday...I got shipping notification Wednesday that it was being sent from Hong Kong...arrived here at around 1:00PM local time...two days from Hong Kong to Texas, wow!
> 
> I've got it running this morning in my Ham Radio room, listening to my HE-400i's with a MyDAC hooked up to the APPJ with Wireworld Eclipse 8 cables, feeding it from this computer and JRiver via Audioquest Carbon USB cable, and using a home made braided SPC copper braided power cord....installed some NOS Sylvania 6V6GTA "coin base" tubes with a Great Britain manufactured 12AX7 (haven't looked deeply into who makes this one) after running it about an hour with the stock tubes...but, swapped that 12AX7 out just now with a NOS RCA 12AY7 and gained some definition that was glossed over by the previous tube...I've got several other flavors of 6V6 tubes in one of my packed storage units so I'll have to go mining there this weekend...
> 
> ...



Ha.... you even beat me looking at your join date.... by one month! Congrats on your purchase.

Some interesting amps in your inventory by the looks of it, what model Little Dot have you? I have a MKVi+ and someone else here has the MKViii.

Good luck with your modding, don't forget take the advice here, and I think your bypass caps are a little too low, I think 0.1uF is best, but have fun!

Lucky to have got those Black Gate caps, some here have used the next best thing, Kaisei's.


----------



## Rick_B

baronbeehive said:


> Ha.... you even beat me looking at your join date.... by one month! Congrats on your purchase.
> 
> Some interesting amps in your inventory by the looks of it, what model Little Dot have you? I have a MKVi+ and someone else here has the MKViii.
> 
> ...


I bought a box full of those Black Gates several years ago, still have a bunch...
The Little Dot amp is the 1+....


----------



## baronbeehive

BTW, I had to comment on your profile pic... I always loved those TR4's,  as a matter of fact I shall be seeing some today, I'm on my way to a classic car show later!

As a side note I had the same experience as you with mail from Hong Kong, got here quicker than local mail!


----------



## Rick_B

baronbeehive said:


> BTW, I had to comment on your profile pic... I always loved those TR4's,  as a matter of fact I shall be seeing some today, I'm on my way to a classic car show later!
> 
> As a side note I had the same experience as you with mail from Hong Kong, got here quicker than local mail!



I restored that 1962 TR4 from a basket case in the late seventies...I even drove it to a local transportation museum and it earned me a spot as their restoration manager...biggest mistake I made was selling that car, my 1967 390GT Mustang fastback, and my 1976 KZ-900...ahh well, the adventures of youth!

I miss British cars, they were so much fun to work on, and contrary to many beliefs, were not that bad as daily drivers....I had the TR4, a Spitfire, and restored also a Sprite and a Midget....I loved peeling my 6'3" self out of a Spridget....tiny little cars but I could fit in them, unlike the Honda S2000 or even the Miata of recent vintage.

Back to the subject of this thread,  I'm impressed by the sound of this little amp...I've recently been using my Antique Sound Labs amp in transformer output mode with my HE-400i's...my impressions of this amp, with the coin base Sylvanias and a "real" NOS TungSol 12AX7 are very favorable, I need to do more evaluation and let the unit run in for a while before I do any real in depth analysis, but so far it is impressive.

I've been messing with electronics for over five decades, building, fixing, restoring, and using all kinds of audio and Ham Radio gear, doing a simple capacitor swap on this amp should be a doddle...with as good as it sounds stock, though, I wonder....

I've got a series of burn-in tracks running through the amp now and in a couple of days will listen more intently to see what the results tell me.

Thanks for the note!


----------



## baronbeehive (Aug 5, 2018)

Rick_B said:


> I miss British cars, they were so much fun to work on, and contrary to many beliefs, were not that bad as daily drivers....I had the TR4, a Spitfire, and restored also a Sprite and a Midget....I loved peeling my 6'3" self out of a Spridget....tiny little cars but I could fit in them, unlike the Honda S2000 or even the Miata of recent vintage.
> ….
> I've been messing with electronics for over five decades, building, fixing, restoring, and using all kinds of audio and Ham Radio gear, doing a simple capacitor swap on this amp should be a doddle...with as good as it sounds stock, though, I wonder....
> 
> Thanks for the note!



OK, I was interested!

Must resist commenting on your various cars, some of which I know quite well! I know what you mean about fitting in cars, I have a new version Mini Cooper S (BMW) and I believe it has less room inside than the old minis, which I also had way back, which look like toys side by side with the new ones, this is down to all the safety features needed nowadays.

Yes the amp is good in stock form.... with the mods, and the right tubes, it is simply great! The amp is easy to mod, only problem the PC is not very sturdy so...!!

NB: there were 4 TR4's at the show today, all looking great!


----------



## Maxx134

Rick_B said:


> I bought a box full of those Black Gates several years ago, still have a bunch...


If you have bigger than 330uf, try it.
I had tried similar size and was surprised how much more forcefull the bass achieved with 1000uf.
Even 2200uf is good as long as you add a .1uf or smaller film cap to help it..


----------



## Rick_B

Maxx134 said:


> If you have bigger than 330uf, try it.
> I had tried similar size and was surprised how much more forcefull the bass achieved with 1000uf.
> Even 2200uf is good as long as you add a .1uf or smaller film cap to help it..



More bass?

I just listened to Cryogenic Encounters by Liquid Stranger...I don't see the need for any more force in the bass than that...the well recorded high res FLACs, DSF, and WAV files stored on my computers are shown pretty darn well, the one area I am trying to improve is the "tinkly" stuff...for instance, I know how good Melody Gardot's "Who will comfort me" sounds on a $100K+ system I work with at least three times a week...I listen to the sound of the zills in a tambourine for instance, to tell me how clear and clean the high end is...I find that with my hearing that the less distortion there is in the high end the longer and more comfortably I can listen without fatigue and exacerbating my tinnitus...

Sometimes it is hard balancing getting the top end to be really good and natural sounding and not removing texture...I love texture...to me it's what makes music come alive.

I do have some Sprague 1000uf @ 63V caps, but does quality outweigh quantity here?  That is, do the qualities of the Black Gate caps trump the higher microfarads of the Spragues?


----------



## baronbeehive

Rick_B said:


> More bass?
> 
> I just listened to Cryogenic Encounters by Liquid Stranger...I don't see the need for any more force in the bass than that...the well recorded high res FLACs, DSF, and WAV files stored on my computers are shown pretty darn well, the one area I am trying to improve is the "tinkly" stuff...for instance, I know how good Melody Gardot's "Who will comfort me" sounds on a $100K+ system I work with at least three times a week...I listen to the sound of the zills in a tambourine for instance, to tell me how clear and clean the high end is...I find that with my hearing that the less distortion there is in the high end the longer and more comfortably I can listen without fatigue and exacerbating my tinnitus...
> 
> ...



I'd like to chime in here, before Maxx134 adds his thing, because this is quite close to my heart, as I've been mentioning this very thing on the thread relating to the other amp I have, (the LD).

I entirely agree with you about the textural details, I first noticed them on this amp immediately after modding it, it came as quite a shock! Since then I've been trying to get the same sound from the other amp.

First, I think you need the bass frequencies to add richness to the sound throughout the frequencie response so that you don't get that annoying tinkly stuff you mention. I would choose the coupling caps with care as the most important change. I used Jupiter copper foil paper and wax caps mainly because I had one left over from modding the other amp. They have a great natural sound which we found out about on the other thread, however they are expensive. There are alternatives almost as good such as the ones Maxx134 used, Audyn True Copper, much cheaper. The  important thing seems to be the copper which gives the lively realistic sound. The other thing is that the better quality caps separate the sound into layers better and bring air into the sound allowing you to hear what's going on more easily. They are also refined, but at the same time reveal all the detail that's there.

The cathode caps mainly allow efficient response from peaks in the waveform, so you get better speed and recovery as you probably know, so that the PSU is freed of some work in maintaining the signal waveform, important in a low output amp.

I spent a lot of time trying to remove the tinkly stuff from the other amp and then I realized it was just too smooth and needed texture back in the sound, for me this APPJ is one alive amp, it has this and it has clarity.

Bear in mind this is one of the cheapest amps on the market, but my amp, the speaker APPJ, has been said to be ridiculously good in expensive systems and I've been saying it for some time now, I wouldn't change a thing. Whether it will compete with a 10k system is another thing, something I wouldn't know about, but I  have a feeling it would give it a good run for its money!


----------



## Maxx134

Rick_B said:


> Sometimes it is hard balancing getting the top end to be really good and natural sounding and not removing texture...I love texture...to me it's what makes music come alive.


For texture, you will need above average coupling caps (Jupiter copper)...



Rick_B said:


> I do have some Sprague 1000uf @ 63V caps, but does quality outweigh quantity here? That is, do the qualities of the Black Gate caps trump the higher microfarads of the Spragues?


My usage of the higher capacitance was for using demanding planar headphones, which can cause slight voltage fluctuations at the cathode resistor voltage.
The audible effect of larger size was actually more sustain , not greater bass.
In your case the blackgates would probably be preferable.



baronbeehive said:


> about on the other thread, however they are expensive. There are alternatives almost as good such as the ones Maxx134 used, Audyn True Copper, much cheaper.


I no longer recommend the Audyn for the "coupling" position.
Instead I would use it for a bypass position.
Although it was superior transparency, it also does not do as well, a layered soundstage.
I will be switching to Jupiter for coupling, and clarity cap CMR for any bypassing.
For the electrolytics, the Nichion Muse is also good like the AudioNote Kaisie.


And way cheaper.


----------



## baronbeehive

Rick_B said:


> I know how good Melody Gardot's "Who will comfort me" sounds on a $100K+ system I work with at least three times a week



I wonder if you could hook up your APPJ to your 100k system somehow? Would be interesting.... I've already said that reviews have said how good my speaker APPJ is with high end speakers.


----------



## Rick_B

baronbeehive said:


> I wonder if you could hook up your APPJ to your 100k system somehow? Would be interesting.... I've already said that reviews have said how good my speaker APPJ is with high end speakers.



It's not my system, let's make that perfectly clear!  I'm retired and live off of Social Security, there's no way I can afford something like that...even contemplating the price of the Jupiter capacitors mentioned in this thread is out of my budget...but, I do set-up and evaluate systems for people who do have the money, but not the time or expertise to do it well.  I work part time for a well respected mail order/Internet audio dealer but have also been interested in electronics since building my first radio receiver over fifty years ago, I am nearing my fourth decade as an Advanced Class Ham Radio licensee yet high fidelity has been a passion of mine for decades.

My APPJ is a headphone amp, not a speaker amp, and the only thing I could do would be to hook it up to the Esoteric stack (transport, DAC, Rubidium Clock) and see how it performs there...I'm almost afraid to do that...it might melt my mind...

Getting to work around the upper echelon of audio gear really gives me a chance to "calibrate" my ears as to what is possible and helps guide my much more budgetary attempts to get good sound in my home.

I could take home, and have taken home, many, many pieces of gear over the past three decades to test and evaluate and therefore I realize that it is just my luck that allows me to sit and listen to it and get a handle on what is possible without having to "invest" a bunch of money in the gear.  

Which is what has brought me to inexpensive headphone amps, I'm still trying to come up with something that does as well as the Bryston headphone amp that we carry, but for a lot less money...and, I have a lot of vacuum tubes in storage...

I still haven't done any mods to my APPJ, I prefer to let new electronics run in for two weeks with music and burn-in tracks before really sitting down to take a listen...

Thanks for the comments!


----------



## Mecii

Maxx134 said:


> For texture, you will need above average coupling caps (Jupiter copper)...
> 
> 
> My usage of the higher capacitance was for using demanding planar headphones, which can cause slight voltage fluctuations at the cathode resistor voltage.
> ...



Do you think you will be able to mount the Jupiter's in such a way to not have to extend the case? Can't wait to see pictures of this. Also, how did you extend your case and where did you acquire the materials?
Thank you for all your input here!


----------



## Maxx134

To extend case was a bit tricky as the board needs to be buffered or it will get the weight .
I used screw extenders from tube guards.
I will take pics when I open for upgrade.


----------



## baronbeehive

Maxx134 said:


> To extend case was a bit tricky as the board needs to be buffered or it will get the weight .
> I used screw extenders from tube guards.
> I will take pics when I open for upgrade.



I used screws and brackets from a meccano set, ideal size for the purpose, unfortunately my own boyhood set had long gone and so I had to buy new ones!



Mecii said:


> Do you think you will be able to mount the Jupiter's in such a way to not have to extend the case?



The Jupiters will fit, and the cathode caps, the problem is the bypass caps, I don't think you will be able to get these to fit without extending the base, you could look at different caps measurements to see.



Rick_B said:


> It's not my system, let's make that perfectly clear!



Ha... no I didn't mean to suggest that it belonged to you... heaven forbid, just that you had access to such a system!!We can all dream but I return to the review of my amp which suggested that nobody with an expensive system would contemplate using such a cheap component - the APPJ - with extreme high end speakers because of the differential in price but that was the only reason, not the quality of sound of the APPJ.

I came across the speaker APPJ, called the Miniwatt, because I had a SS amp at the time with a tube preamp and wanted to replicate the sound I got from this setup with a bit less complicated system. The Miniwatt did this…. and more! And part of the fun was that it was cheap, and overlooked by others!



Rick_B said:


> My APPJ is a headphone amp, not a speaker amp, and the only thing I could do would be to hook it up to the Esoteric stack (transport, DAC, Rubidium Clock) and see how it performs there...I'm almost afraid to do that...it might melt my mind...



I think I see your problem, I would be scared to even switch on this system!

Edit: Your blackgate caps should go some way to achieving the SQ you want. I wondered if you could maybe do an exchange with some of these highly desired caps for a pair of Jupiters perhaps, if you have some to spare.


----------



## Rick_B

baronbeehive said:


> I used screws and brackets from a meccano set, ideal size for the purpose, unfortunately my own boyhood set had long gone and so I had to buy new ones!
> 
> 
> 
> ...



I would like to try something like that on the system, but the room is medium sized and damped, the few watts out of a single 6V6 type tube just wouldn't be enough to push the Spendor D-7s to a reasonable volume....maybe the Reference 3As he has, but the CAT amps, or the Pass XA250's are a better fit...we've tried a set of Dared 845 based SET amps, and they do sound sweet on the Ref 3As, but that's what 20? 25 WPC?  A bit more than the 6V6...now, maybe in my Ham Radio room system with the Loth-X Ion BS-1 speakers, or the Loth-X Amazes and the smaller volume and closer listening perspective of the room it would sing...but that is where I do most all of my headphone listening in the night when the significant other has trundled off to bed, and boy, do I not like to wake her up when she has retired for the night!



> I think I see your problem, I would be scared to even switch on this system!


We have a system that is sitting at 250K retail at work, so I guess I'm a lot luckier than a lot of people in what I get to listen to....


> Edit: Your blackgate caps should go some way to achieving the SQ you want. I wondered if you could maybe do an exchange with some of these highly desired caps for a pair of Jupiters perhaps, if you have some to spare.


Well, yeah, I'd be willing to do an exchange, the Black Gates I have are 330uf@25V F types, if there is any interest LMK....


----------



## baronbeehive (Aug 12, 2018)

Rick_B said:


> I would like to try something like that on the system, but the room is medium sized and damped, the few watts out of a single 6V6 type tube just wouldn't be enough to push the Spendor D-7s to a reasonable volume....maybe the Reference 3As he has, but the CAT amps, or the Pass XA250's are a better fit...we've tried a set of Dared 845 based SET amps, and they do sound sweet on the Ref 3As, but that's what 20? 25 WPC?  A bit more than the 6V6...now, maybe in my Ham Radio room system with the Loth-X Ion BS-1 speakers, or the Loth-X Amazes and the smaller volume and closer listening perspective of the room it would sing...but that is where I do most all of my headphone listening in the night when the significant other has trundled off to bed, and boy, do I not like to wake her up when she has retired for the night!



Yes, indeed!

All I can say about this, bearing in mind I'm an interloper on this thread with my APPJ, different to the title of the thread - but they do have things in common, is this: I can't usually go more than half volume without deafening myself, and my speakers are only 87db so shouldn't really work.... but it does work in a big way!

Have a look at this review: http://www.6moons.com/audioreviews/miniwatt/miniwatt.html

This is an earlier model than mine.


----------



## Rick_B

baronbeehive said:


> Yes, indeed!
> 
> All I can say about this, bearing in mind I'm an interloper on this thread with my APPJ, different to the title of the thread - but they do have things in common, is this: I can't usually go more than half volume without deafening myself, and my speakers are only 87db so shouldn't really work.... but it does work in a big way!
> 
> ...


I have actually seen and heard one of the Miniwatt amps several years back in a customers house...used for a desktop system...

I have a pair of 3.5 watt Bottlehead Paramours that I built years ago so I do know how far a few watts could punch, especially on the Lowther DX55 drivers in my Third Rethms, or even on my Klipsch Hereseys...


----------



## Haidar

I'm considering some changes to the circuit. If one were to remove all the negative feedback, what would the output impedance be?


----------



## Maxx134

Haven't seen any schematic for this to judge.


----------



## Haidar

Maxx134 said:


> Haven't seen any schematic for this to judge.



Hi Max, There is a schematic here:
https://www.head-fi.org/threads/any...une-appj-pa1502a.780178/page-24#post-13480908


----------



## baronbeehive

I've had the opportunity to compare my speaker APPJ with my other amp, a Little Dot MkVI+ now that I've more or less finished the mods on it.... and now that it's working again. I think my speaker APPJ must be very similar to the headphone APPJ because it seems to be performing very similarly to what Maxx134 has said about his.

First I would say that you would expect the Little Dot to be good, it is a balanced amp, heavily modded to match with the headphones you are using and to optimise tube operation, and has expensive tubes - too expensive.

I found that the Little Dot is slightly better in resolution but the APPJ is very close, the LD is also slightly better in soundstage, probably due to the resolution which puts the instruments accurately in the soundstage, easy to hear through headphones, however the APPJ is again not far behind, it has a deep, wide soundstage, very realistic sounding through speakers, great detail and depth. I still feel that the APPJ has a slightly tighter bass, but the mods on the LD have put it very close with excellent detail. Also the APPJ has slightly better textural detail, I feel this is partly due to the frequency range which allows the APPJ to stand out in some ways, for example cymbals really sparkle without being too sharp. Recent mods however have pulled up the LD and it is now very close. Guitars ring out beautifully on both amps, also pianos have weight and attack on both amps.

I think we've come a long way with this amp simply by installing some quality components to make the difference. I have to say that I'm very happy with them both, they're both performing at top level..... perhaps not at the $100K level, but then I wouldn't know about that would I!!


----------



## jekjek

baronbeehive said:


> I've had the opportunity to compare my speaker APPJ with my other amp, a Little Dot MkVI+ now that I've more or less finished the mods on it.... and now that it's working again. I think my speaker APPJ must be very similar to the headphone APPJ because it seems to be performing very similarly to what Maxx134 has said about his.
> 
> First I would say that you would expect the Little Dot to be good, it is a balanced amp, heavily modded to match with the headphones you are using and to optimise tube operation, and has expensive tubes - too expensive.
> 
> ...



Agree. This amp is amazing!


----------



## baronbeehive

jekjek said:


> Agree. This amp is amazing!



Ha ha, yes indeed!



Haidar said:


> I'm considering some changes to the circuit. If one were to remove all the negative feedback, what would the output impedance be?



This is an interesting idea, and one which has been mentioned on another thread.

The 6V6 is operated in tetrode mode and this is why NFB is required to keep impedance down. If NFB was removed the 6V6 should go triode mode and then some other changes would be required all of which is beyond my skill level atm.

It's shocking to think that this baby amp can be improved yet still.


----------



## Maxx134

The output sockets are wires for triode operation, so no change there.

I am thinking the removal of feedback would change the output volume, sound, and impedance of the "circuit", but the secondary of output transformers are fixed,
So their impedance to the headphones should be the same.

The output tube impedance match to the transformer primary should change and may or may not be an issue.
 Would have to calculate the output tube impedance and also find info on acceptable range to match.

Although may be easy to disconnect, (I haven't checked) my concern would be both volume and distortion if it was a large NFB..
Most likely moderate if the resistor is a high value.

Haven't check just commenting.


----------



## Haidar

baronbeehive said:


> The 6V6 is operated in tetrode mode and this is why NFB is required to keep impedance down. If NFB was removed the 6V6 should go triode mode and then some other changes would be required all of which is beyond my skill level atm.





Maxx134 said:


> The output sockets are wires for triode operation, so no change there.
> 
> I am thinking the removal of feedback would change the output volume, sound, and impedance of the "circuit", but the secondary of output transformers are fixed,
> So their impedance to the headphones should be the same.
> ...



Thanks both of you! To me this is worth exploring, even with some alterations to the circuit.


----------



## jekjek

It's getting quiet here

I am listening to this unknown ultron 12ax7 square getter

It sounds pretty awesome


----------



## Maxx134 (Aug 31, 2018)

Peekeesh said:


> @Maxx134 i was backreading and CZ4A said that for kt66 tube, tungsol is recommended just because the draw is .9 a. Other kt66 tubes pull 1.3a.
> 
> https://www.head-fi.org/threads/any...une-appj-pa1502a.780178/page-15#post-12521319
> 
> If those genalex kt66 work great and won't damage the amp, then im down to try them



I found out that the Genalex tubes I am using are running a bit hotter than all previous tubes I used so far, so they making the amp a bit hot after on a while, but I am sticking with them anyways as the amp seems to not be having issue with them.

It probably is not recommended to run tubes with heaters that high but so far I am liking these tubes most overall.
Resolve is just as good with other tubes uses but these do have the largest soundstage.
The Tung-Sol KT66 was nice but not have the resolve of the others.
I believe it needed more burn in but I was not impressed.
The Gelanex was impressive from the start.

The KT66 type have the largest soundstage on this amp circuitry..
More than the 6L6 which was another favorite for large stage.
The other tubes I tried excelled at clarity, like the 6BG6G (RCA)..
All output tubes..


----------



## baronbeehive

jekjek said:


> It's getting quiet here
> 
> I am listening to this unknown ultron 12ax7 square getter
> 
> It sounds pretty awesome



I can't remember if I had an Ultron or a Hytron, but it was a Tungsol.

Yours looks like it has round plates, does it have any other markings

A pic might help!


----------



## jekjek

Here you go
Anyone can help to identify this?


----------



## baronbeehive

jekjek said:


> It's getting quiet here
> 
> I am listening to this unknown ultron 12ax7 square getter
> 
> It sounds pretty awesome



I think Ultron was just a German label of various European manufacturers. I see the plates are the flat ladder type plates, probably the most common type, they're the same whether it be Mullard, Amperex, and others. I think probably not these though, Mullards and Amperexes usually have the 2 or 4 seams on top of the glass and other identifying marks. The getter is common too.

Unfortunately without any codes either etched or printed it would be impossible to identify these, they could be great...… or not so great!!

As your probably know I thought my Philips tubes were either Mullards or Mazdas and it was only by identifying the codes on the glass that the Philips factory could be identified.


----------



## jekjek

baronbeehive said:


> I think Ultron was just a German label of various European manufacturers. I see the plates are the flat ladder type plates, probably the most common type, they're the same whether it be Mullard, Amperex, and others. I think probably not these though, Mullards and Amperexes usually have the 2 or 4 seams on top of the glass and other identifying marks. The getter is common too.
> 
> Unfortunately without any codes either etched or printed it would be impossible to identify these, they could be great...… or not so great!!
> 
> As your probably know I thought my Philips tubes were either Mullards or Mazdas and it was only by identifying the codes on the glass that the Philips factory could be identified.




Thanks baron

My APPJ will sometimes lost the left channel sound completely

I am not sure is it problem with the volume pot or the tube

I am using RCA 6V6 now but still experiencing sudden channel lost


----------



## baronbeehive

jekjek said:


> Thanks baron
> 
> My APPJ will sometimes lost the left channel sound completely
> 
> ...



When did this start happening, and under what circumstances, for example does it happen after a while after switching on without you touching it or does it happen when you move one of the tubes?

First though, swop the 2 power tubes around and see if the problem moves with the tube.


----------



## jekjek

baronbeehive said:


> When did this start happening, and under what circumstances, for example does it happen after a while after switching on without you touching it or does it happen when you move one of the tubes?
> 
> First though, swop the 2 power tubes around and see if the problem moves with the tube.



It will happen randomly after i turn on the amp for around 20 to 30 minutes

then the left channel will fade off in 2 seconds

Initially i thought is because of the loose screw in the volume pot. I can get back the left channel by wiggling with the volume pot

Last week I have tightened up the volume pot and its tight now. No room to wiggle now 

Changed power tube from 6V6 to EL33 with same issue


----------



## baronbeehive (Sep 4, 2018)

Right, I strongly suspect a faulty connection, most likely on one of the 6 caps you put in, coupling, cathode, or cathode bypasses. The fact that you wiggle the pot only moves the whole PCB, I think if you wiggle any of the tubes the same thing might happen. You might be able to find the culprit by wiggling the tubes and the one causing the worst drop off might be where the fault is.

You will have to take off the chassis top and bottom again, *half an hour or so after you've switched off to reduce any chances of danger from the undischarged caps. Never touch anything inside while it is switched on.* Look at every connection you made and see if it looks loose, or coming away from the board. You might have soldered over a lifted pad, which is the round connection onto the board, so it would be difficult to see any fault. Sometimes a cold solder will cause this problem, and they are difficult to see. The solder joints should look shiny, not dull or rough looking. If you gently pull at each connection you might see any loose movement. If it is a lifted pad then you will have to make a proper repair…. I had to do this. Lifted pads can happen when you pull out old components, or if you put too much heat or pressure on the joint when soldering.

The best way to find a faulty joint is by using a multimeter and testing for continuity, but since there are so few new joints made with these mods you should be able to detect anything faulty easily. Anything suspect should be resoldered. Make sure no wires are touching or loose.

Also check the wires are not broken when you put back the chassis top plate. Also make sure there's no blobs of solder lying around, they can cause shorts.

Can you take any pics of the joints.

Really any soldering should be checked with a multimeter for continuity with all connected components which would show up any problems, because if you don't do this you won't know if there's a problem, and you could short out the board and components.

If in doubt this would be an easy job for an electronics engineer to fix.


----------



## jekjek (Sep 4, 2018)

its a mess down there


----------



## Rick_B

jekjek said:


> its a mess down there



First thing that comes to mind is that solder is not glue.


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## baronbeehive

jekjek said:


> its a mess down there



.....yes.... Hi jekjek!

I'm afraid there are a few problems here…!!!





Just to take one thing that I can see, where there is no pad to solder to you can see that there isn't a proper connection here, you might have been lucky and made contact on the other side of the board, looks the same for the coupling cap. I'm a bit surprised that the  amp worked at all frankly. Seriously I would advise you to spend a relatively small amount of cash and get this properly repaired because it might stop working for good otherwise.

Sorry to have to say that but you won't be able to enjoy it until the job is done properly, I don't know what you think?


----------



## jekjek

baronbeehive said:


> .....yes.... Hi jekjek!
> 
> I'm afraid there are a few problems here…!!!
> 
> ...



I think I have to re do the solder job my self and see if i can get it fix

Labor repair service in Singapore is not cheap

Thanks for your reply Baron!

I appreciate it


----------



## baronbeehive

jekjek said:


> I think I have to re do the solder job my self and see if i can get it fix
> 
> Labor repair service in Singapore is not cheap
> 
> ...



OK, take it slowly step by step, post pics and we will try to help.

There are plenty of resources online, youtube soldering videos etc.

Good luck!

.


----------



## jekjek

Found the culprit
Its the headphone jack
Wiggling it will get the missing channel back


----------



## rdale

I bought an APPJ PA1502A to drive my Audeze LCD-3s via Nordost Heimdall 2 cables. I paid 185 euros including shipping and think it is one of the best HiFi bargains I've ever bought. I upgraded the power tubes to cryo treated Genalex Gold Lion CV511 / 6V6G, and the input tube to a Psvane 12AX7. I am certainly a fan of tube amps with speaker systems, but I had never heard a tube amp driving headphones before. The was a large upgrade between driving the LCD-3s direct from my Chord Hugo and from the APPJ. More treble resolution with the Audezes sounding almost like electrostatics by comparison. The bass and dynamics seem fine and the doesn't seem to be any lack of power from the PA1502A

I've had a Miniwatt N3 speaker amp for about 8 years which is also an amazing bargain. I use Psvane EL84s and a TJ Full Music 12AX7 in that amp, fitted with EAT Cool Dampers. It drives a pair of Tandy LX5 speakers with the Linaeum ribbon-like tweeter and sounds great.

I've replaced the metal feet in both amps with 3M Acoustfeet, and here are the pair of them sitting on SSC Minibase stands:



 




This picture shows the 3M Acoustifeet - I unscrewed the standard metal feet and then needed to cut small holes in the Acoustifeet to accomodate the screws on the amp bases.


----------



## Mecii

DavidK35 said:


> Yes that's right, after reading the whole thread I decided that the changes indicated from the other mod were not for me.
> 
> If you have ordered adaptors for the 6BG6 "G"s then I hope you have ordered them with longer external wires than normal.
> The ones I got initially were only suitable for 6BG6 "GA"s. The ones I have on order now are 20mm longer.
> ...



I ran into the same issue with the adapters I ordered off of eBay; also not long enough to reach the top of my 6BG6 G tubes. I now have to to reorder adapters with longer leads. Could you share where you were able to purchase adapters with longer leads that can reach the top of the 6BG6 G?
Thank you,
Mecii


----------



## baronbeehive

rdale said:


> I bought an APPJ PA1502A to drive my Audeze LCD-3s via Nordost Heimdall 2 cables. I paid 185 euros including shipping and think it is one of the best HiFi bargains I've ever bought. I upgraded the power tubes to cryo treated Genalex Gold Lion CV511 / 6V6G, and the input tube to a Psvane 12AX7. I am certainly a fan of tube amps with speaker systems, but I had never heard a tube amp driving headphones before. The was a large upgrade between driving the LCD-3s direct from my Chord Hugo and from the APPJ. More treble resolution with the Audezes sounding almost like electrostatics by comparison. The bass and dynamics seem fine and the doesn't seem to be any lack of power from the PA1502A
> 
> I've had a Miniwatt N3 speaker amp for about 8 years which is also an amazing bargain. I use Psvane EL84s and a TJ Full Music 12AX7 in that amp, fitted with EAT Cool Dampers. It drives a pair of Tandy LX5 speakers with the Linaeum ribbon-like tweeter and sounds great.



Ha, I see you've got a pair, headphone-speaker APPJ combo, I thought of doing this, looks great!

Is that right your Tandy LX5's are only 81db, and yet work well with the 3.5w Miniwatt, that finally confirms what I've been saying all along that the amp drives my 87db speakers very well.

I had the TJ Full Music tubes as well.

Finally are you really saying that your APPJ is a large upgrade from the Chord Hugo, amazing information. Perhaps now people will believe!


----------



## rdale

baronbeehive said:


> Ha, I see you've got a pair, headphone-speaker APPJ combo, I thought of doing this, looks great!
> 
> Is that right your Tandy LX5's are only 81db, and yet work well with the 3.5w Miniwatt, that finally confirms what I've been saying all along that the amp drives my 87db speakers very well.
> 
> ...



The Tandy's are actually quite efficient, maybe 88-89db or similar, and they are very easy to drive as the crossovers consist of a single inductor and a single capacitor. I upgraded the crossover components with a better cap and an air cored inductor and rewired them internally with Chord Carnival cable. The Miniwatt drives them really well.

I think the TJ Full Music sounds as good as the Psvane 12AX7, but one I was using in my phone preamp failed after about six months and so maybe the quality control isn't as good as the Psvanes.

The APPJ PA1502A is well up to driving the LCD-3s - it isn't that the Hugo sounds bad with the LCD-3s, just that the APPJ sounds so good. I don't think I will upgrade the coupling caps like several people on this thread have done, as I'm not confident I have sufficient electronics knowledge to do  that. But I'm pretty sure the improved feet and SSC Minibase stands have helped with the bass tightness and dynamics of both the the speaker and headphone amps.

Here is a picture of my completed desktop setup with the LX5s on IsoAcoustics stands:


----------



## rdale

rdale said:


> The Tandy's are actually quite efficient, maybe 88-89db or similar, and they are very easy to drive as the crossovers consist of a single inductor and a single capacitor. I upgraded the crossover components with a better cap and an air cored inductor and rewired them internally with Chord Carnival cable. The Miniwatt drives them really well.



I'm wrong about the efficiency of the Tandy LX5s - I've done some searching for old reviews and they are indeed only 83db. It might be because they are omnidirectional with a simple crossover that the Miniwatt N3 has no trouble at all driving them.


----------



## CZ4A

Mecii said:


> I ran into the same issue with the adapters I ordered off of eBay; also not long enough to reach the top of my 6BG6 G tubes. I now have to to reorder adapters with longer leads. Could you share where you were able to purchase adapters with longer leads that can reach the top of the 6BG6 G?
> Thank you,
> Mecii



If you're handy with a soldering iron you can make your own 6BG6 adapters using this kit (http://www.vacuumtubes.com/6BG6.html). The seller will sell the adapters separately of the 6BG6GA tubes he's selling, and may be able to assemble them for you for a fee if you ask. The SND Tube Sales adapters are what I use for my 6BG6Gs and they reach the anode cap just fine. Plus, I have plenty of wire left over to make my own adapters. One of my upcoming projects will be to make a 6/12SN7 to 7/14F7 octal-to-loctal adapter.


----------



## Zulkr9

I just found an article where someone uses a 6L6, is this optimal and is there no issue of harming the amp ? https://www.aradiogurl.net/hhjournal/2016/06/01/gemtune-pa1502a-appj-headphone-tube-amp-mod/


----------



## baronbeehive

Zulkr9 said:


> I just found an article where someone uses a 6L6, is this optimal and is there no issue of harming the amp ? https://www.aradiogurl.net/hhjournal/2016/06/01/gemtune-pa1502a-appj-headphone-tube-amp-mod/



No, that shouldn't be a problem. I find that the amp doesn't run very hot so it should be able to handle a bit more heat without any issues.


----------



## DavidK35

Mecii said:


> I ran into the same issue with the adapters I ordered off of eBay; also not long enough to reach the top of my 6BG6 G tubes. I now have to to reorder adapters with longer leads. Could you share where you were able to purchase adapters with longer leads that can reach the top of the 6BG6 G?
> Thank you,
> Mecii


The ones I ordered were from "vicaudio_1" on ebay. In hindsight 160mm was a bit too big 150mm would be better. No extra cost involved


----------



## Peekeesh

I have this adapter and it works great:

https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.com/ulk/itm/201176552239


----------



## baronbeehive

Rick_B said:


> I can't wait to let this thing run in for a couple of weeks, and then start with a few little mods, I have some Black Gate 330mfd@25V caps I'll use for the cathode bypass caps, I'll probably bypass them with a couple of .01mfd Auricaps I have if I don't use Sprague Vitamin Q .012@400V oil caps...I also have some Gudeman .51@300V Vitamin Q type oilers that I may try as coupling caps...



I don't know how far you've got with the mods but I forgot to say I have 2 spare Kaisei 1000uF 25v cathode caps going begging. I know you have caps but these are top notch so if you want drop me a line.

I also have some tubes you might be interested in going cheap.... Amperex 12AX7, Philips Miniwatt 12AX7, TJ Full Music 12AX7 (new issue), Tungsol 12AX7 (new issue), GE 14AF7, Tungsol 14AF7, RCA 14F7, GE 12SL7 and a matched pair of nos Russian 6F6C Kobra's, The Kobras were highly thought of a while back on the thread, they didn't work on my amp, (which has EL84's), also the Tungsol 14AF7 are probably the pick of the bunch! They're no use to me now.


----------



## swagadelic

selling this btw, with some upgraded tubes. more in the ad. (youill have to google translate from swedish)

starting bid at 100 euro

https://www.tradera.com/item/301974/323585172/appj-pa1502a-horlursforstarkare


----------



## baronbeehive

Maxx134 said:


> Also, I do like some 9pin tubes regardless for signature, but for resolution I still believe the 14type loctals are a bit above and way cheaper.



Yeah, you're right about the 14AF7 type, I have the Tungsol, it is the most resolved of tubes I've tried. I've just gone back to it and I had forgotten how good it was. So it's in my top 3 now with the Philips and the Mazda. These other 2 have qualities that I like though so I can't get rid of any of them, the Mazda with the light and airy treble, and the Philips with the rich tone and layered soundstage. I'ts not quite up to the TS on resolution but very good, but the TS soundstage is more one dimensional I feel, none the less all great tubes, and the Philips is still my fav.


----------



## Maxx134 (Jan 6, 2019)

Zulkr9 said:


> I just found an article where someone uses a 6L6, is this optimal and is there no issue of harming the amp ? https://www.aradiogurl.net/hhjournal/2016/06/01/gemtune-pa1502a-appj-headphone-tube-amp-mod/


I am using the Gold Lion 6L6 which is the hottest running tube I ever placed on the amp and so far it working fine, but I don't use it more than 2 hrs at a time and the only concern I have is the heat so if you have a nicely cool or vented room it should be ok, but the tube heater current on the standard (not the safer heater current tungsol remake) 6L6 is a bit too high.

I dont care and take my chances because they are my favorites in terms of retaining resolve with  having the largest soundstage and also having a good sound.

Edit**
The amp does not get hotter than most tube amps so it still ok.
On other tubes it runs cool.

I still consider the 6bg6g tubes as the most transparent , but second in soundstage.

Hey Baronbeehive, have you ever tried your headphones to the speaker amp version you have?
Just need some speakertaps..


----------



## baronbeehive (Oct 12, 2018)

Maxx134 said:


> I am using the Gold Lion 6L6 which is the hottest running tube I ever placed on the amp and so far it working fine, but I don't use it more than 2 hrs at a time and the only concern I have is the heat so if you have a nicely cool or vented room it should be ok, but the tube heater current on the standard (not tungsol remake) 6L6 is a bit high.
> I dont care and take my chances because they are my favorites in terms of retaining resolve with  having the largest soundstage and also having a good sound.
> 
> I still consider the 6bg6g tubes as the most transparent , but second in soundstage.
> ...



I came across something a while back about Gold Lion tubes for drivers, so probably 12AX7, are yours the reissues? I think they all are.

I haven't tried it with headphones, there was some issue about how to wire them, I think with an adapter, and ground them which wasn't resolved to my satisfaction so I stayed away!

It would be interesting though, it is so similar in performance to the LD.

Edit: I just remembered you like to bask in temperatures around 30 degrees, so not surprising the amp runs a touch hot LOL.


----------



## baronbeehive (Oct 17, 2018)

Just done another quick comparison of the 2 amps now that I've gone back to trying the 14AF7 tubes again - heavily modded, balanced LD amp, and the APPJ speaker amp. The LD has the best tubes I've got in, the APPJ has the very resolving 14AF7's.

Probably the last time I bother to do this, it's getting increasingly difficult to tell the differences when they are so close:

They are so similar in resolve thanks to the 14AF7 in the APPJ, the soundstage is a bit more enveloping in the LD with more depth, but with the Philips 12AX7 in this brings more depth to the soundstage of the APPJ, the bass is still slightly tighter in the APPJ, mid range is fuller and refined sounding in the LD, treble is still slightly more extended in the APPJ partly due to the 14AF7 but even with the Philips in the APPJ it is still more prominent. With the recent mods to the LD the textural details and dynamics are much more similar in the 2 amps now.

The differences in treble and bass are slight and I put this down to the fact that the APPJ still sounds a bit sharper and I think the reason for this is that the output impedance is very well controlled by the OT's whereas the LD is output transformerless and achieves the right impedance with NFB which can be problematic. Neverthless I think the LD can be improved further by those Nichicon caps I heard about, and possibly my OCC silver output wires, so still something up my sleeve......

This is remarkable considering how heavily modded the LD is and how cheap and slightly modded the APPJ is, it really is a bargain, I can't really understand the people who move on and try something else when it would be difficult to better what they have in the first place!


----------



## baronbeehive

Just checked up to see if the APPJ's are still available, in case mine should ever go wrong, not that it will, it's been going strong for well over 5 years now, and I came across what looks like the latest speaker version, the EL34 amp here:

https://www.aliexpress.com/item/APP...-Ended-Audio-HIFI-Stereo-Amp/32832930441.html

There has been a replacement for both headphone and speaker amps with a 2 power tube speaker amp not long ago. It looks like the makers have gone back to a 2 power tube, 1 driver tube design with the latest amp which looks very pretty. Some specs are different too, wonder what it sounds like?


----------



## Makiah S

I feel goofy, but did we have any kind of compilation of which 12SN7s we liked and how they compared to existing 12au7s? 

I just realized my next amp [a nice TOTL semi-custom build aroudn $1600] uses 12au7s and my 12SN7s should work! As I got a nice little collection of 12SN7s for this amp!!!


----------



## Makiah S

baronbeehive said:


> Just tried the GE12SL7 silver round plates, to see if indeed they do sound a tad harsh in the treble as some have said, or whether they sound more realistic on my system....
> 
> Now that I've had initial listening impressions I completely agree with the above 2 posts regarding the 12SL7 GE, but not the Tungsol, the sibilance is especially prominent because I haven't heard that on this amp before, so again I'm back with my TS5751, I don't think it can be beaten!
> 
> ...



You talking New Production TS5751


----------



## baronbeehive

Mshenay said:


> You talking New Production TS5751



No NOS. Readers of this thread will know that I've updated my tube preferences since that post and if you haven't been keeping up with this thread..... shame on you lol.... after a long time with the TS5751 I now favour these: TS 14AF7 for best resolution as several here have found, Philips 12AX7 for punch, soundstage, overall balance, and Mazda 12AX7 for downright beautiful treble, light, airy seems to float away on the breeze!

So what's your new amp and why have you gone for it?

BTW there hasn't been any comparison of 12SN7's and 12AU7's here.


----------



## Makiah S

baronbeehive said:


> No NOS. Readers of this thread will know that I've updated my tube preferences since that post and if you haven't been keeping up with this thread..... shame on you lol.... after a long time with the TS5751 I now favour these: TS 14AF7 for best resolution as several here have found, Philips 12AX7 for punch, soundstage, overall balance, and Mazda 12AX7 for downright beautiful treble, light, airy seems to float away on the breeze!
> 
> So what's your new amp and why have you gone for it?
> 
> BTW there hasn't been any comparison of 12SN7's and 12AU7's here.




Sonnare Amps the Emotion, runs a 4P1L pair + a 6SN7 and a 12XX7. Dan has STRONGLY recommend I ditch my 12SN7s an start investing in some nicer made for Audio 9Pins which I'll eventually start doing, but ugh I already spent so much buying/selling and trying out Octals -.- 

Oh well, I appreciate  having the Philips recommendation. Prices aren't TOO crazy, other suggestions have been for the CBS 5814a and the GE 6072a 

anyways, when the 9pins start rolling in I'll likely start comparing them to my 100%/100% 12SN7GT


----------



## Maxx134

baronbeehive said:


> Some specs are different too, wonder what it sounds like?


It using similar caps as stock of this one, so expect it to need cap upgrade to sound its best.



Mshenay said:


> Sonnare Amps the Emotion


Details are hidden on "patent pending" design because it is nothing more than using SS help to it, just like most newer amps today.

The real difference here is using a more transparent highly regarded tube for  output stage, so you get less tube coloring and distortion.

At price of $1.7k , I would expect above average sound.
I would expect it to rival some $4k tube amps, so its fairly good value.

Of course it is not as great value as this, or a DIY amp, but better than most.
I like to see a trend of greater value amps than what we have so far.

Too many expensive old-school designs in this market ready to be eclipsed...


----------



## Maxx134

I updated this old post on the caps:

https://www.head-fi.org/threads/any...une-appj-pa1502a.780178/page-24#post-13481434


----------



## Makiah S

Maxx134 said:


> It using similar caps as stock of this one, so expect it to need cap upgrade to sound its best.
> 
> 
> Details are hidden on "patent pending" design because it is nothing more than using SS help to it, just like most newer amps today.
> ...



Maybe but we will see! Details later this month I hope! 

I also got a Psvanne 12AU7 to compare to my Sylvania 12SN7GT


----------



## baronbeehive

Maxx134 said:


> I updated this old post on the caps:
> 
> https://www.head-fi.org/threads/any...une-appj-pa1502a.780178/page-24#post-13481434



You mention that the Kaisei's are dark sounding but I don't think that is entirely the reason to necessitate the use of faster bypass caps to liven the amp up. The reason is that other members who haven't used Kaisei's have also mentioned this perception of lifelessess on upgrading the caps to high capacitance. So I must agree with your other statement that Redge advised the use of the bypass caps for that specific reason, ie that they are faster and therefore would bridge that gap when the high capacity caps are recharging after a log spell of discharge, if I understand correctly.

The options appear to be:


Upgrade caps quality but keep at stock value - retains liveliess but power recovery possibly found wanting
Upgrade caps to higher value - possible loss of liveliness but more power recovery ability
Upgrade caps to higher value + use small, fast bypasses - more power recovery ability, better liveliness, but possible smearing of sound
On the last point I haven't heard any problem.

I must say that the Kaisei's sound goes very well on this amp though.

And, yes exciting developments are happening now with the modern designs!



Mshenay said:


> Maybe but we will see! Details later this month I hope!



Look forward to your comparisons!


----------



## Makiah S

I used kasai's and Auri cap XO's and I felt that this amp outperforms a schiit Valhalla 2 pretty noticeably... so to say that the arc apps are dark I would ask in comparison to what? As with the Russian power tubes Max recommended earlier I don't think a brighter of sound would do this amp any good

an I'll b picking up the psvanne tommorow or Wednesday


----------



## Makiah S

Yuck, sadly what every one says about the Psvanne being to dry is indeed true, 

It was wonderful with Hotel California but switching into Spanish Harlem, I found strings and the paino tooo harsh. The ADI 2 Dac I'm getting will likely help me get the clarity I'm looking for.


----------



## rdale

Mshenay said:


> Yuck, sadly what every one says about the Psvanne being to dry is indeed true,
> 
> It was wonderful with Hotel California but switching into Spanish Harlem, I found strings and the paino tooo harsh. The ADI 2 Dac I'm getting will likely help me get the clarity I'm looking for.



Maybe the Psvane needs running in. I use Psvane 12AX7s (not 12AU7s) in my pa1502a, my Miniwatt N3 amp and my Puresound P10 phono amp and it doesn't sound at all harsh in any of these applications. It has a distinctive harmonically rich tone and great clarity which I really like.


----------



## Makiah S (Jan 10, 2019)

rdale said:


> Maybe the Psvane needs running in. I use Psvane 12AX7s (not 12AU7s) in my pa1502a, my Miniwatt N3 amp and my Puresound P10 phono amp and it doesn't sound at all harsh in any of these applications. It has a distinctive harmonically rich tone and great clarity which I really like.



The AX7 is a different gain from the AU7, an as you know more gain should also yield more distortion but in the case of a tube amp the added distortion isn't always undesirable, though I did have it running Pink Noise for the last day before I listened tonight.

That said the other question is what Power Tubes your using and what DAC you've got. I will say it was quite clean indeed. I'll likely run it through my Ember II as well to see how it does there.


----------



## baronbeehive

Maxx134 said:


> I editing this post a year later because I have tried various caps since in different amps and in these types of circuits where there's a cathode cap, it will play a factor to the sound, and Kaisei caps in tbis situation will provide a darker richer tonality, while a Nichion KZ will be more neutral, and I prefer them over any Silmic2.
> 
> Remember the caps are in a situation to affect tonality *only* because they are in a position of being a "cathode cap".



After trying those Nichicons in my other amp and being so pleasantly surprised, it's scarey to think what the Nichicons will do to this amp pushing it yet further!

Having said that I really like the tonality of the Kaisei's, I still think the tonailty of the amp is second to none, at least of those amps I've heard, and it is so nearly at the very top level I think.


----------



## baronbeehive (Jan 11, 2019)

…...and a note about the Nichicon KZ's... they're cheap as well as good! So anyone thinking of upgrading the cathode caps, go on and do it!

The upgrade in sound will be well worth it, tight defined bass and extended nicely textured treble, it did it for me with my other amp lol! Bass and treble are already good on this amp so it will be the icing on the cake, or the cherry if you prefer! Treble is such that plectrum strikes on guitar strings stands out beautifully, all types of cymbals ring out and vocals are an inch from your ear, neutrality and transparency are all increased... need I say more.
.


----------



## corbimatic

Hi everyone,

I’ve read all 48 pages on this thread over the course of the last several weeks, and decided to buy the APPJ PA1502A based on what I see. I have an extensive record collection and a working knowledge of electronics and acoustics from college courses, but am completely new to tube amps. For years, I’ve been running my turntable through my home theater receiver with what I felt were pretty good results, actually. My wife and I just finished a gut rehab of a two flat here in Chicago, which we stripped all the way down to the external shell. That allowed me to build out my home theater the the exact specs I wanted, and during that process I decided that I wanted to dip a toe into the HiFi world to try to get the best I could out of my records, finally separating the two competing functions into equipment that worked best for each.

One thing about me is that I hate spending money on something until I know I really like it. As an example, I wanted to digitize my record collection a decade ago, so I bought an entry-level Stanton T.55 turntable with a USB port. I hated it. Not the turntable, but the whole process, and all the time spent cleaning up the mp3s and normalizing and blah. Just not my thing, I guess, so when Apple Music came out I just added every record I own to my library (which ps, had a blast with that!) and ended up with significantly better quality digital versions than I ever could have reproduced through any needle cartridge on the market. It makes me very, very happy that I didn’t drop more $$$ into a better turntable. That home theater I just mentioned - nearly all Amazon Warehouse deals. I decided to start playing tennis recently, so I signed up for Park District courses for $100/10 wks. and bought myself a $25 racket (ps, I’m up to level 3 in 6 months after never having held a racket in my life and shopping for a nicer one if you have suggestions.) Ok so you get the point - start cheap, see if I like it, work up if I feel the need/desire.

I chose the APPJ for a variety of reasons, but #1 is that it’s a headphone amp - not a preamp that can also do headphones, not a speaker amp that can do headphones, it’s for headphones. In the design/build process I ended up with a record cubby under the stairs that will hold a few hundred of my favorites (the rest are also close at hand) and it has a second shelf with just barely enough room for a turntable (with a preamp built in) and a headphone amp - so I didn’t want to pay for circuitry I will never, ever use. Second, I chose this one because based on comments from a number of you, the output transformers appear to be reasonably high quality, which I know from my experience with solid state amplifiers and electronics lab back in college can be make-or-break for sound quality. Third, I wanted an amp that was 100% tube amplification and not a hybrid (which to me feels like taking the garbage halfway out, which side note: had a roommate after college who would do that and it drove me bonkers; why is there a trash bag at the door when you could keep going another 4 feet to the outside cans.) Fourth, I really wanted something I could feel comfortable opening up and taking apart, which also limited my cost parameters - I’m unlikely to rip open a $500 amp and much less likely to swap out parts. Lastly, I really wanted someting that didn’t come with Chinese or Russian tubes with no known equivalents, like the 6J1 or the 6N1, particularly. On this last note - it seemed like so many of the reasonably priced headphone amps that are out there used tubes like these that had no known equivalents, didn’t have much in the way of NOS available, and had zero reissue stock available. My plan (and this is where I think I’ll get some immediate feedback) from the beginning was to buy an amp that allowed me to replace the tubes using readily available reissue stock first before even bothering with NOS. 

So I settled on the gemtune over the Valhalla, the Little Bear or anything else Nobsound makes, the Bravo Audio, or any of the Little Dots. I just saw the UPS guy ring the doorbell and drop off the box and got a notification from Amazon that it was delivered, so I’m going to set it up over the weekend and plan to post my thoughts on it in the coming weeks. My first set of reissues (which, guys, I know they’re not the same as NOS, and that they’re made in Russia and all that) is a matched pair of Genelax 6V6GTs and a Genelax 12AX7 I ordered on Amazon (Prime with free! shipping). I’ll let you know what I think of those before I check out some of the (many) other reissue options available on Prime. 

For the tech nerds who need to know my whole setup to provide thoughts/comments/advice, I still have that Stanton T.55 turntable with a new 500 cartridge, which has a preamp built in. I will run it to the amp via RCA cables, and then I have a pair of Sony MDR-7506 headphones that are 64 ohm impedance and believe me, I know they’re not the nicest or most expensive option out there but I’m guessing fit my bang-for-the-buck preferences nicely.

More to follow!
-Matt.


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## baronbeehive

corbimatic said:


> I’ve read all 48 pages on this thread



Hi Matt!

I like that...



corbimatic said:


> One thing about me is that I hate spending money on something until I know I really like it.



I really like that….



corbimatic said:


> ... so when Apple Music came out I just added every record I own to my library (which ps, had a blast with that!) and ended up with significantly better quality digital versions than I ever could have reproduced through any needle cartridge on the market. It makes me very, very happy that I didn’t drop more $$$ into a better turntable.



Yes I've been there, you did the right thing. I've got a couple of albums I couldn't get anywhere else which I digitized on a USB deck but on the whole I would steer clear of that laborious process as you say...



corbimatic said:


> So I settled on the gemtune over the Valhalla, the Little Bear or anything else Nobsound makes, the Bravo Audio, or any of the Little Dots. I just saw the UPS guy ring the doorbell and drop off the box and got a notification from Amazon that it was delivered, so I’m going to set it up over the weekend and plan to post my thoughts on it in the coming weeks. My first set of reissues (which, guys, I know they’re not the same as NOS, and that they’re made in Russia and all that) is a matched pair of Genelax 6V6GTs and a Genelax 12AX7 I ordered on Amazon (Prime with free! shipping). I’ll let you know what I think of those before I check out some of the (many) other reissue options available on Prime.



…..I was with you all the way... until you mentioned the Little Dot…. that's my other amp LOL!!

Seriously you've made a good choice a lot of people here are very happy!

On the Genelax 12AX7 I am very interested in what you think as I've been wondering about these, some types are highly regarded.

Look forward to hearing what you think when you've done the setup under your stairs.... we will be happy to share our thoughts on tubes, mods and so on!


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## Pratt99

baronbeehive said:


> …..I was with you all the way... until you mentioned the Little Dot…. that's my other amp LOL!!



@baronbeehive  How do you like the little dot compared to your speaker version of pa1502? I understand it is no longer apples to apples comparison. But the reason I am asking is that my appj pa1502 is not in working condition right now. It started sounding thin and sharp(on both the channels). I checked/changed the tubes, source, changed outlets, took a look inside the amp etc but all is well, so the problem is with amp. As of now I have not decided to fix it, and thinking of trying something new. So interested to learn about your impression on little dot. Thanks.


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## Pratt99 (Jan 11, 2019)

Mshenay said:


> I used kasai's and Auri cap XO's and I felt that this amp outperforms a schiit Valhalla 2 pretty noticeably...



Interesting comparison! Since my Appj pa1502a is not in working condition right now, I tried the Massdrop CTH to see if I could be happier. So here is my comparison between the two based off my MEMORY. My appj only had the coupling caps upgrade(jantzen superior z-cap)  and I had the 14AF7 + RCA 6bg6 tubes on them. After 100 hrs burn in and two weeks worth of listening I listed the CTH back for sale. IMO the APPJ clarity advantage in the treble region was pretty obvious even based off my memory, but CTH had its strengths in instrument placements(layering capability). I was able to locate the instruments in 3d space which I never felt or noticed in a significant way with the APPJ amp. Also CTH felt like it had a wider soundstage, but this I am not sure since I am relying on my memory here.


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## baronbeehive

Pratt99 said:


> @baronbeehive  How do you like the little dot compared to your speaker version of pa1502? I understand it is no longer apples to apples comparison. But the reason I am asking is that my appj pa1502 is not in working condition right now. It started sounding thin and sharp(on both the channels). I checked/changed the tubes, source, changed outlets, took a look inside the amp etc but all is well, so the problem is with amp. As of now I have not decided to fix it, and thinking of trying something new. So interested to learn about your impression on little dot. Thanks.



Sorry to hear about your amp! That's a shame because it looks like you had done some good cap upgrades and have a good tube combo for best soundstage and resolution. The only thing you could have done to top all of that off is fit cathode caps which would have increased power reserves resulting in more dynamics, and the tonality of the amp could be changed depending on which caps you used also.

I will try as best as I can to compare the two amps, bear in mind my APPJ is the speaker version and I prefer to listen through speakers rather than headphones because I feel the sound is more real and natural.

Also bear in mind it will depend on what equipment you have, mods etc., and I have to remember what my impressions were prior to modding them

In unmodded form both amps sounded great, I preferred the APPJ for the reasons above. The APPJ is a faster amp which means that bass is tighter, treble had a bit more sparkle. Whereas the LD had a smoother more relaxed, richer more refined sound and great soundstage, both amps had great tonality. I would say the LD was slightly more tubey sounding whereas the APPJ was more neutral.

The mods bring the level of both amps up to compete with top level amps I believe. I wanted to try to cancel out the weaknesses of both which I more or less managed. The LD became more lively, tighter, transparent resolved, great treble and bass more like the APPJ and the APPJ more resolved punchy airy soundstage, more like the LD.

I did however use top quality caps in the mods so nothing was spared in the APPJ and I believe that was what really bumped up the level of the amp in soundstage in particular, which has a nice separation of instruments and a wide, fairly deep soundstage. I don't know if this is due to the speakers you would have to ask others on this thread some of who have experience of the 2 amps also.

I have to say that it was way easier to mod the APPJ, not much needed to be done whereas it took a lot of work to get the LD to get to the top level, and a lot of the time it was trying to keep up with the APPJ in some respects.

If you were to change amps I don't think you would get a better performing amp, unless you spent well into the thousands, what would be different is the flavour of the amp, do you want more tubey sound, more transparent sound and so on.

I wouldn't change my APPJ except for an absolute top level amp and probably not even then. Why would I when I love the flavour of both amps now LOL!


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## baronbeehive

@rdale I remembered you have the speaker and headphone APPJ's and I wondered if you could do a comparison of these, it would be interesting to see how they differ!


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## Haidar

Could someone please point out in the schematic where the coupling caps and cathode caps are?


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## baronbeehive

Haidar said:


> Could someone please point out in the schematic where the coupling caps and cathode caps are?



I haven't got the schematic but this is where they are on the board, coupling caps are the white rectangluar caps, cathode caps are the brown round caps.


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## Haidar

Thanks baron!


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## Pratt99

baronbeehive said:


> Sorry to hear about your amp! That's a shame because it looks like you had done some good cap upgrades and have a good tube combo for best soundstage and resolution. The only thing you could have done to top all of that off is fit cathode caps which would have increased power reserves resulting in more dynamics, and the tonality of the amp could be changed depending on which caps you used also.
> 
> I will try as best as I can to compare the two amps, bear in mind my APPJ is the speaker version and I prefer to listen through speakers rather than headphones because I feel the sound is more real and natural.
> 
> ...



@baronbeehive  Thanks much for your time and patience.  This makes me reconsider my decision to try something else. The reason I wanted to look around is I am not sure how to or where to go to fix this amp. I am located in the USA and I did a google search on "tube amp repair" and I got some results on people who work on guitar amps.  So I need to figure this out, if someone located in USA have some info on this please share.

Another option is to order a new amp from china (costs around $200) since I already have the tubes and caps, but I got the same question "what if I run into issues , where do I go to fix it?"


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## rdale

baronbeehive said:


> @rdale I remembered you have the speaker and headphone APPJ's and I wondered if you could do a comparison of these, it would be interesting to see how they differ!



Yes I have both the PA1502A and a Miniwatt N3 speaker amp.

They are a great visual match and look really good sat next to each other - I posted a picture of them earlier in this thread. I've replaced the feet on them with 3M Acoustifeet and sat them on SSC Mini Bases (I got both of these items from MCRU in the UK). It is very difficult to compare the sound of the headphone amp driving Audeze LCD-3s with the Miniwatt driving modified Tandy LX5 speakers with Linaeum ribbon-like tweeters. They both sound very transparent and 'electrostatic-like'. The Miniwatt works best with Psvane valves, and I preferred Psvane EL84s to Genelec Gold Lion Reissue EL84 valves that I use in my other small single ended speaker amp, a Glow Amp One. I use cryo treated Gold Lion Reissue 6V6s in rthe PA1502A with a Psvane 12XA7 input tube. I use Duelund speaker and interconnect cable all my systems and I think that adds to the tonal richness that valves amps have.

In comparison to the Glow Amp One, the Miniwatt N3 has slightly faster more lit up treble where the Glow was more on the rich side, although the Minwatt bass was less extended. I haven't noticed a lack of bass extension with the LCD-3s/PA1502A compared with my Chord Hugo driving the Audezes. I didn't really hear what the Audezes/Nordost Heidall 2 cables were capable of until I heard them with the PA1502A.


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## baronbeehive (Jan 12, 2019)

Pratt99 said:


> @baronbeehive  Thanks much for your time and patience.  This makes me reconsider my decision to try something else. The reason I wanted to look around is I am not sure how to or where to go to fix this amp. I am located in the USA and I did a google search on "tube amp repair" and I got some results on people who work on guitar amps.  So I need to figure this out, if someone located in USA have some info on this please share.
> 
> Another option is to order a new amp from china (costs around $200) since I already have the tubes and caps, but I got the same question "what if I run into issues , where do I go to fix it?"



No worries I enjoy being boring about amps!

Re: your APPJ I don't want to influence you in any way regarding keeping or changing it if that's what you want, it's just my view.

What I've done if I need help in the past is to take it to a local electronics repair engineer. It probably doesn't matter if they specialise in tube amps, all that's needed is someone who can test an electronic circuit and usually anyone such as TV repairs and such like would be able to troubleshoot and repair it. It's probably something happened to the mods you did affecting the circuit.

Edit: I would not use it again until it's been repaired before any damage is done!


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## baronbeehive

rdale said:


> Yes I have both the PA1502A and a Miniwatt N3 speaker amp.
> 
> They are a great visual match and look really good sat next to each other - I posted a picture of them earlier in this thread. I've replaced the feet on them with 3M Acoustifeet and sat them on SSC Mini Bases (I got both of these items from MCRU in the UK). It is very difficult to compare the sound of the headphone amp driving Audeze LCD-3s with the Miniwatt driving modified Tandy LX5 speakers with Linaeum ribbon-like tweeters. They both sound very transparent and 'electrostatic-like'. The Miniwatt works best with Psvane valves, and I preferred Psvane EL84s to Genelec Gold Lion Reissue EL84 valves that I use in my other small single ended speaker amp, a Glow Amp One. I use cryo treated Gold Lion Reissue 6V6s in rthe PA1502A with a Psvane 12XA7 input tube. I use Duelund speaker and interconnect cable all my systems and I think that adds to the tonal richness that valves amps have.
> 
> In comparison to the Glow Amp One, the Miniwatt N3 has slightly faster more lit up treble where the Glow was more on the rich side, although the Minwatt bass was less extended. I haven't noticed a lack of bass extension with the LCD-3s/PA1502A compared with my Chord Hugo driving the Audezes. I didn't really hear what the Audezes/Nordost Heidall 2 cables were capable of until I heard them with the PA1502A.



Thanks for that, very interesting! I'm lucky in that I've managed to get the sound of both the speaker amp and the headphone amp to sound pretty much the same, quite an achievement considering the different equipment involved!

Yes they both looked good in the picture you posted!

I remember reading about the Glow One a while back and they were comparing it to the Miniwatt N3 and on that basis I decided on the Miniwatt.... and I'm glad that I did!


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## corbimatic

Welp, I’m hooked. The stock tubes took the entire side 1 of Houses of the Holy to warm up, but by side 2 the sound was pretty impressive. Clarity was good, bass was there, vocals could get a little harsh at times but that’s also probably partly Robert Plant’s fault. Next I listened to Axis: Bold as Love and interestingly, the first track (EXP) when the grungy distorted guitar is swirling around your head - there was almost a discreet step between left, right, and center. I’m new to HiFi headphones, so I’m not sure if I’m just used to it sounding much more blended as sounds move from left to stereo to right channel. Anyway, I didn’t pick up on it as much or at all on the remaining tracks that rip sound all over the soundstage in your head, and generally was impressed with the amp. I am willing to admit that after spending as much time shopping as I did, I’m prone to confirmation bias here, so I’ll give it a critical listen again but my first impression is: this is a very good amp for the money.

Oh, and I think I need to ground the chassis of my turntable to it. I got just a slight zap when I touched both with my hand at the same time. Didn’t notice any of the tell-tale humming of an ungrounded magnetic cartridge, so not too concerned, but I assume it can’t hurt.

Question - my headphones are 64ohm Sonys. At high gain, they sound great and plenty loud at maybe 45/50% volume on the dial. On low gain, they sound great at 85/90%. Is there any reason to think I might get better or worse long-term tube performance at different volume settings? Said another way - Navy jet engines in the 60s were designed to operate best when wide open, so my (now) 95 year old neighbor who was a test pilot they nicknamed “Speedy” never flew anywhere at less than max velocity. Samesies? By the way, Speedy still takes his tiny 12’ boat with the way oversized engine out in 5-7’ swells in the middle of the lake and calls it surfing.

Question 2 - how do I post pictures? This thing doesn’t like my setup pics.


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## baronbeehive (Jan 13, 2019)

corbimatic said:


> Welp, I’m hooked. The stock tubes took the entire side 1 of Houses of the Holy to warm up, but by side 2 the sound was pretty impressive. Clarity was good, bass was there, vocals could get a little harsh at times but that’s also probably partly Robert Plant’s fault. Next I listened to Axis: Bold as Love and interestingly, the first track (EXP) when the grungy distorted guitar is swirling around your head - there was almost a discreet step between left, right, and center. I’m new to HiFi headphones, so I’m not sure if I’m just used to it sounding much more blended as sounds move from left to stereo to right channel. Anyway, I didn’t pick up on it as much or at all on the remaining tracks that rip sound all over the soundstage in your head, and generally was impressed with the amp. I am willing to admit that after spending as much time shopping as I did, I’m prone to confirmation bias here, so I’ll give it a critical listen again but my first impression is: this is a very good amp for the money.



First impression is always important, I tend to find that the impression improves with time as you get to appreciate the amp.

Probably more of a headphone thing than to do with the amp. I know some headphones have that weird presentation where there is a well defined place for right, centre, and left, much like the old recordings used to put drums on the left stage, keyboards on the right etc. If you were to get to modding... and who wouldn't... then I would suggest good quality caps will improve soundstage. With my.... *expensive*.... Jupiter caps the soundstage has increased and become much more open, airy and seamless on my headphone amp.



corbimatic said:


> ...my (now) 95 year old neighbor who was a test pilot they nicknamed “Speedy” never flew anywhere at less than max velocity. Samesies?



I'm hoping you're not thinking of listening at max volume all of the time LOL! Be kind to your ears…. as well as tubes!

I don't know if it would harm the tubes long term, but that's not practical listening!



corbimatic said:


> Question 2 - how do I post pictures? This thing doesn’t like my setup pics.



Copy and paste is the simple way.

This was copied and pasted from Paint:






This was uploaded from a folder:


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## rdale

corbimatic said:


> Question 2 - how do I post pictures? This thing doesn’t like my setup pics.



I had the same problem when I first registered for Head-Fi - I think you might need to have done a minimum number of posts or maybe someone has to confirm you're not a robot. But it suddenly started working for me.


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## Pratt99

baronbeehive said:


> No worries I enjoy being boring about amps!
> 
> Re: your APPJ I don't want to influence you in any way regarding keeping or changing it if that's what you want, it's just my view.
> 
> ...



@baronbeehive Thanks again! Will check with my local electronics repair shop then. Since the sound went thin I assumed this should be a powersupply issue and someone with knowledge on tube biasing will be a better source to ask for help. Will update if I manage to get this fixed.


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## corbimatic (Jan 14, 2019)

Question on the high/low gain switch - my guess is that on the high gain setting nothing is actually happening, and that the low gain is just adding a resistor in series to increase circuit resistance for use with lower impedance headphones. If that’s the case, that would help me answer the question on whether to run on high at 40% or low at 80% for normal listening volumes. Anyone take a close look at the switch? I’m not ready to crack mine open quite yet.

Second question for folks who have switched out capacitors - has anyone hooked this up to a oscilloscope to see what the stock low-end frequency response within 3db is? I get how the coupling capacitor might be acting as a high-pass filter in this circuit, but wondering if we can put some real numbers on it. Mine seems to have pretty good low frequency response, as best I can tell it’s getting pretty far to the low-end of the range and I can’t detect any of the tell-tale signs of a diode thirsting for current when the bass drum thumps. Wondering if this was something done primarily by people powering speakers with this little guy?

Second listening session was Diver Down and by the time I got to Little Guitars (which is an excellent track) the amp was definitely warmed up and sounding great. A good record for checking out the range, in my opinion, because you have a lot of very loud things going on, sometimes all together, and sometimes not. Everything sounded very accurate and I got really nice clarity. I followed that up with 77, which is an excellent pop record but is the least demanding from a post-production/engineering/cross-fading/stereophonic standpoint of what I’ve listened to so far. That proved to be a good test in and of itself, as David Byrne’s range might be limited but his voice is distinct and was very well represented and clear, and sounded natural. Last record was The Bends, and while they certainly mellowed out and became much more prog/alt/art-rock with OK Computer, this is a record that is still very much guitar-god-alternative-grunge and yet uses production/engineering to move things around the sound stage. The amp again, represented things well and gave a nice, full-range, clear representation of the record. 

So that’s probably it for posts using the stock tubes. They sound great, for what they are. I question if the 6N4 is the reason I hear discreet steps on certain highly engineered tracks like EXP on Axis: Bold as Love. It could also be that I’m not used to headphones and for the first time I’m hearing the hurried overnight work of Chas Chandler et al after Hendrix lost the side 1 master tape when he left it in a taxi. It only really showed up on that one track, which is admittedly the most demanding of what I’ve heard so far. I would say this whole tube amp thing is outrageously fun and new and exciting for me, and while I don’t think that’s clouding my judgement too much, I would also readily admit that I miss having many several thousand watts of multi-channel power shaking my whole house. We just moved, but in the old place it was a source of pride for my wife to come home and find that I’d popped another retrofit recessed light out of the ceiling with sonic power emanating from coils driving magnets shaking massive diaphragms. Oh well. Time to grow up anyway, right?

I’ve got reissue Genalex matched 6V6s and a 12AX7 on order and will keep rolling through the reissues I can get on Amazon Prime. From what I can see on there now, I can get matched 6V6s and a same-branded 12AX7 (or similar) from: Electro-Harmonix, Tung-Sol, Telefunken, JJ Electronics, Mullard, and Fender’s Groove Tubes (not really a reissue on that last one I guess...) One of the many reasons I settled on this amp was the ready availability of the reissued stuff. After that I might maybe possible start digging a hole in my wallet with some of the NOS options. The 1960s RCA 6V6G does look pretty rad, after all.


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## baronbeehive (Jan 16, 2019)

Pratt99 said:


> @baronbeehive Thanks again! Will check with my local electronics repair shop then. Since the sound went thin I assumed this should be a powersupply issue and someone with knowledge on tube biasing will be a better source to ask for help. Will update if I manage to get this fixed.



OK. It could be the SMPS as you say but I think that's more likely to go suddenly..... and would be accompanied by smoke lol, so perhaps it's the driver tube socket because the driver tube feeds both power tubes. The socket gets a lot of use with tube rolling and could have worked loose.


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## baronbeehive (Jan 16, 2019)

Oh I see... I thought you had actually been consigned to the cupboard under the stairs lol!



corbimatic said:


> Question on the high/low gain switch - my guess is that on the high gain setting nothing is actually happening, and that the low gain is just adding a resistor in series to increase circuit resistance for use with lower impedance headphones. If that’s the case, that would help me answer the question on whether to run on high at 40% or low at 80% for normal listening volumes. Anyone take a close look at the switch? I’m not ready to crack mine open quite yet.




I see you have the updated APPJ with the gain switch, nice!

You are correct and it wouldn't harm the circuit to run at those settings, I don't know what the effects are on tubes is in the log run though.



corbimatic said:


> Second question for folks who have switched out capacitors - has anyone hooked this up to a oscilloscope to see what the stock low-end frequency response within 3db is? I get how the coupling capacitor might be acting as a high-pass filter in this circuit, but wondering if we can put some real numbers on it. Mine seems to have pretty good low frequency response, as best I can tell it’s getting pretty far to the low-end of the range and I can’t detect any of the tell-tale signs of a diode thirsting for current when the bass drum thumps. Wondering if this was something done primarily by people powering speakers with this little guy?



You are correct again, but no i don't have an oscilloscope. I'm the only one here with speakers apart from rdale.

This is why we decided to put high capacitance cathode caps in for that very reason. Also this is why I made 3 options in my earlier post for replacing them. The actual power output, 3.5W in my case though quite low is not so important for the operation of the amp, more important is recovery from clipping in transients. If this is super effecient then you could probably make do with only 1W of power. We settled on 1000uF capacity for the cathode caps so that there was plenty of power in reserve for recovery. The problem is that electrolytics are slow, what is really needed is fast acting film caps but these are very large and expensive so what we went for is a compromise of high capacitance electroytics but with small faster bypass caps to aid those higher frequencies. The higher you go with capacitance the higher the power reserves but the longer the charge-discharge cycle which will adversely affect the higher frequencies.

Clipping is not usually heard over the music because the ear just thinks what it is listening to is a continuous stream of music, and if recovery from transient clipping is good it would not be heard, but if recovery was poor then the music would sound pretty bad.



corbimatic said:


> Oh well. Time to grow up anyway, right?



Possibly, yes!

1000Watts seems a good idea until you realize that circuits with that much power have associated problems with damping down the frequency response to get the desired output impedance, and need to use massive amounts of GNFB which has negative effects on SQ.

How would you say your APPJ compares to your 1000W monster, apart from all that power?

Very interesting observations in your review, keep us posted!

Edit: I only have experience of the TS and JJ reissues, and I liked the JJ's which have a good reputation. However reissues in general.... nope, not really!


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## corbimatic

Ah, that makes sense. I have the headphone-only version of the amp, the APPJ PA1502A, and so far I’m really impressed with the sound quality when pushing my headphones, which are reasonably priced but audiophile enough for me (the Sony MDR 7506.) I think you have the APPJ PA1501A, and so I get why you might potentially experience clipping and might have trouble reaching very low frequencies without upgrading your coupling capacitors to something that can hold a lot more farads when you try to push speakers. I said I was done with reviews of the stock tubes, but for reference I’ll add that I listed to DMB’s Big Whiskey and the GrooGrux King, which is a nice test because Dave’s voice is singular, and Carter’s drums are almost more melody than rhythm and Dave’s guitar is almost more rhythm than melody, and the amp did a really nice job recreating the entirety of the soundstage with great clarity. I followed that with Meddle, which is a great test album for the stock capacitors as the entire B side is basically one long homage to low frequencies and sonic experimentation by Waters and Gilmour. From what I can tell, zero issues hitting and sustaining and recovering from very low notes at pretty loud volumes. I think for anyone considering getting a dedicated headphone-only amplifier with pure tube amplification (not hybrid) this little guy is an excellent choice, even with the stock tubes in. 

My other setup is my home theater, which is a completely solid state Dolby 7.1 setup with the speakers all built into the walls and ceiling. The comparison is somewhat difficult, because with all that digital processing the soundstage separation is going to be extreme by comparison, but at the same time my vinyl is a stereo source at best. In the past I would run the 3 front channel speakers and subwoofer (a Monitor Audio IWS-10 pushed by an IWA-250) and quite franky, it’s just not an apples-to-apples comparison. It makes movies with Dolby Atmos or 5.1 or whatever advanced digitally processed source sound pretty cool, and for music it’s... pretty effen good, too, but again, hard to compare. Headphones have such dramatically lower total harmonic distortion than even the world’s most expensive speakers that it’s just not apples-to-apples. Also I never once plugged headphones into my receiver, although I suppose I could do that and get back to you. I’d say the primary difference is that I don’t feel the bass anymore. I certainly hear it and it’s represented with perfect clarity, but the couch and walls aren’t also vibrating and things aren’t rattling on the shelves.

The reissue Genalex Gold Lion 12AX7s and matched 6V6s show up today, if the approaching snowstorm doesn’t stop the delivery. This is Chicago, so a few inches of snow shouldn’t be an issue. Everything I’ve read tells me the reissue 12AX7 is a worthy reissue, so I’m excited to see what it can do. I think the 6N4 is potentially limited in its ability to process tracks that move things around the soundstage in rapid, loud fashion (see also: Jimi Hendrix.) 

I also have to admit that I couldn’t hold off buying NOS tubes for as long as I intended. I found a matched pair of smoked glass 1950s RCA 6V6GT aka VT-107A and a 1960s RCA 12AX7A on nostubestore.com and pulled the trigger. I asked for the low-cost shipping method which will take a few weeks coming from Europe, so I’m telling myself that means that I actually waited awhile before diving into NOS world, but if I’m being honest with myself I jumped in head first and plunked down a chunk of money before the reissue experimentation even began... And so it goes.


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## baronbeehive (Jan 19, 2019)

corbimatic said:


> Ah, that makes sense. I have the headphone-only version of the amp, the APPJ PA1502A, and so far I’m really impressed with the sound quality when pushing my headphones, which are reasonably priced but audiophile enough for me (the Sony MDR 7506.) I think you have the APPJ PA1501A, and so I get why you might potentially experience clipping and might have trouble reaching very low frequencies without upgrading your coupling capacitors to something that can hold a lot more farads when you try to push speakers. I said I was done with reviews of the stock tubes, but for reference I’ll add that I listed to DMB’s Big Whiskey and the GrooGrux King, which is a nice test because Dave’s voice is singular, and Carter’s drums are almost more melody than rhythm and Dave’s guitar is almost more rhythm than melody, and the amp did a really nice job recreating the entirety of the soundstage with great clarity. I followed that with Meddle, which is a great test album for the stock capacitors as the entire B side is basically one long homage to low frequencies and sonic experimentation by Waters and Gilmour. From what I can tell, zero issues hitting and sustaining and recovering from very low notes at pretty loud volumes. I think for anyone considering getting a dedicated headphone-only amplifier with pure tube amplification (not hybrid) this little guy is an excellent choice, even with the stock tubes in.



Yeah! I have the speaker version, the APPJ PA0901A, or Miniwatt, which I always mention to avoid confusion because the Miniwatt threads died out a while ago whereas this thread is still going strong, despite having to be given the kiss of life a while back... and it was touch and go! APPJ's continue to be made and you have the latest upgrade with the gain switch so this is the place to come for information about it. I enjoy reading about members experiences, which are mostly positive.



corbimatic said:


> Headphones have such dramatically lower total harmonic distortion than even the world’s most expensive speakers that it’s just not apples-to-apples. Also I never once plugged headphones into my receiver, although I suppose I could do that and get back to you. I’d say the primary difference is that I don’t feel the bass anymore. I certainly hear it and it’s represented with perfect clarity, but the couch and walls aren’t also vibrating and things aren’t rattling on the shelves.



…...no neither are your brain and eyeballs!

Yes, no beating headphones for accurate reproduction compared even with the most expensive speakers, no room acoustics to consider at all, just the shape of your ears!

Some headphones are capable of real bass heft, even sub bass, and bass drum reverberation but mostly its a question of accurate definition.



corbimatic said:


> The reissue Genalex Gold Lion 12AX7s and matched 6V6s show up today, if the approaching snowstorm doesn’t stop the delivery. This is Chicago, so a few inches of snow shouldn’t be an issue. Everything I’ve read tells me the reissue 12AX7 is a worthy reissue, so I’m excited to see what it can do. I think the 6N4 is potentially limited in its ability to process tracks that move things around the soundstage in rapid, loud fashion (see also: Jimi Hendrix.)
> 
> I also have to admit that I couldn’t hold off buying NOS tubes for as long as I intended. I found a matched pair of smoked glass 1950s RCA 6V6GT aka VT-107A and a 1960s RCA 12AX7A on nostubestore.com and pulled the trigger. I asked for the low-cost shipping method which will take a few weeks coming from Europe, so I’m telling myself that means that I actually waited awhile before diving into NOS world, but if I’m being honest with myself I jumped in head first and plunked down a chunk of money before the reissue experimentation even began... And so it goes.



Don't we all!

Keep us posted on your observations, I am interested in those Gold Lions.

With NOS you should get better all round SQ frankly, soundstage etc. should all go up a level there are plenty of recommendations going back a few pages or so, or you can ask of course.


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## corbimatic

baronbeehive said:


> Yeah! I have the speaker version, the APPJ PA0901A, or Miniwatt, which I always mention to avoid confusion because the Miniwatt threads died out a while ago whereas this thread is still going strong, despite having to be given the kiss of life a while back... and it was touch and go! APPJ's continue to be made and you have the latest upgrade with the gain switch so this is the place to come for information about it. I enjoy reading about members experiences, which are mostly positive.
> 
> 
> 
> ...



The Genalex tubes are in, and they sound great so far - although I’m hearing them develop as they burn in. Spinning OK Computer right now and it’s another great test album, with songs that are all over the map sonically. It seems like the 12AX7 is doing a better job processing multi-channel and cross fades better than the stock tube, and while everything started off a little harsher at first the tubes are definitely mellowing and sounding nice. There was almost a little bit of a vibrato effect on some of the guitar riffs at first, but that’s gone away at this point.


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## baronbeehive (Jan 20, 2019)

corbimatic said:


> The Genalex tubes are in, and they sound great so far - although I’m hearing them develop as they burn in. Spinning OK Computer right now and it’s another great test album, with songs that are all over the map sonically. It seems like the 12AX7 is doing a better job processing multi-channel and cross fades better than the stock tube, and while everything started off a little harsher at first the tubes are definitely mellowing and sounding nice. There was almost a little bit of a vibrato effect on some of the guitar riffs at first, but that’s gone away at this point.



Re: the Gold Lions, check out the following quote from member maxx134:

_"I am using the Gold Lion 6L6 which is the hottest running tube I ever placed on the amp and so far it working fine, but I don't use it more than 2 hrs at a time and the only concern I have is the heat so if you have a nicely cool or vented room it should be ok, but the tube heater current on the standard (not the safer heater current tungsol remake) 6L6 is a bit too high.

I dont care and take my chances because they are my favorites in terms of retaining resolve with  having the largest soundstage and also having a good sound.

Edit**
The amp does not get hotter than most tube amps so it still ok.
On other tubes it runs cool.

I still consider the 6bg6g tubes as the most transparent , but second in soundstage."_

If you followed this advice it would save you a bunch of dosh and a lot of time spent searching.... sleepless nights wondering if you've missed something... and worrying that someone else has got a better setup than you...

You could do even better and have an end game tube setup if you paired the power tubes above with a 14AF7 Tungsol or similar. Several members have found these to be the most resolved of all driver tubes.... and you will like this.... they're dirt cheap, costing a few dollars!

You will need adapters though if you choose to go down this route.


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## corbimatic (Jan 21, 2019)

Ok so the Genalex Gold Lion 12AX7 / B759 is too much gain for the little guy. I gave it a solid go and really let it burn in, but it’s still harsh and giving me nastiness when lyrics contain the letter S or F or if everybody’s playing at the same time. I just ordered a Genalex 12AX7 in the non-gold pin configuration which might sound like I’m a crazy person, but this website gives me reason to think I’ll get a more mellow tone out of it: https://www.amplifiedparts.com/tech-corner/12ax7-comparison-current-made-tubes 
We’ll see. I went back to the stock 6N4 paired with the reissued Genalex 6V6-GTs and using those power tubes is a step up in sound quality; particularly in the low end. Listened to 1984 twice in a row (which ps never do that to your poor records that’s just mean, but I think David Lee Roth craves attention so much that it’s ok this one time) with the two different configurations and Hot For Teacher and I’ll Wait both went from very harsh to not nearly as harsh but still not perfect. Going to keep trying configurations and hope I can find some kind of reference out there with actual electric data like the one above for old tubes.

Edit: also added a Tung Sol 5751 and JJ Electronics 5751 to the order. Thinking that gives me a spectrum of gains to try out, from the gold pin Genalex 12AX7 > standard pin Genalex 12AX7 > JJ 5751 > Tung Sol 5751. Will share results!


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## corbimatic

Ok the Genalex standard pin 12AX7 just showed up and I’m spinning Brothers in Arms with it plus the reissue Genalex Gold Lion 6V6s and there’s a dramatic difference. Only one song in so it’s probably not warmed up yet and there’s no way it’s burnt in but the highs aren’t at all harsh, the vocals don’t have shrill letters S or F and the soundstage is very clear. Excited to get the 5751s in to see what they do but for now this is an outstanding setup.


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## corbimatic (Jan 25, 2019)

Guys the Tung Sol 5751 with the Genalex 6V6s is making Dark Side sound like sonic butter I’m kinda blown away right now. I know every craps on the reissue stock but without needing adapters and without having to pay a fortune and wait for a guy in Prague to snail mail you 60 year old tubes you pray aren’t smashed on the sailboat they take to get here - you can get some pretty stellar sound out of this amp. The clarity is so good I’m hearing things I haven’t heard in probably an unexaggerated 100 listens to this album (they used to haze us to it when I was a pledge). Particularly the talking parts that are mixed in throughout the album. Zero harshness, with tight, forward bass, mid range clarity and crystal clear highs. I’m a big fan rn.

Edit: Also listed to Electric Ladyland and I have to say I’m blown away by this setup. Just the stock amp, no modifications with the TS 5751 and I’m hearing things I’ve never heard in albums I’ve listened to so much the covers are falling apart. At the end of Moon Turn the Tides... Gently, Gently Away there’s a low frequency note that I always assumed was meant to be distant; turns out it’s not. Crazy good clarity and low-end.


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## baronbeehive

corbimatic said:


> Edit: Also listed to Electric Ladyland and I have to say I’m blown away by this setup. Just the stock amp, no modifications with the TS 5751 and I’m hearing things I’ve never heard in albums I’ve listened to so much the covers are falling apart. At the end of Moon Turn the Tides... Gently, Gently Away there’s a low frequency note that I always assumed was meant to be distant; turns out it’s not. Crazy good clarity and low-end.



Hey, great, sounds like you're having a ball!

I thought you'd like the Tungsol, used to be my favourite for many years, I still love it, but I've just moved slightly now to preferring a slightly sharper sound but without the harshness. The Tungsol manages to pull off great detail, soundstage, good bass... and treble, but zero harshness, only beautiful liquid flow.

Great observations, your amp obviously hits the spot!


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## corbimatic

baronbeehive said:


> Hey, great, sounds like you're having a ball!
> 
> I thought you'd like the Tungsol, used to be my favourite for many years, I still love it, but I've just moved slightly now to preferring a slightly sharper sound but without the harshness. The Tungsol manages to pull off great detail, soundstage, good bass... and treble, but zero harshness, only beautiful liquid flow.
> 
> Great observations, your amp obviously hits the spot!



Hey can I put 6L6 tubes in this amp without damaging it or the tubes and without having to do any mods?


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## baronbeehive (Jan 27, 2019)

corbimatic said:


> Hey can I put 6L6 tubes in this amp without damaging it or the tubes and without having to do any mods?



He is talking about NOS tube not the remake from what I can see.

I wouldn't like to advise you on this, I wouldn't have a problem, and Maxx134 says it's OK, you could wait for him to advise. If he is having no problems then you shouldn't either. The tube will be OK but if there is a wire run nearby it could be a concern so caution is advised.

Edit: I would give the RCA 6bg6g's a try first, they have no issues with the heater current and they are next best thing, to see what the APPJ can do.


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## corbimatic

Welp, I’m blown away. I bought a matched pair of RCA 6V6GT aka VT-107As from 1953 and an RCA 12AX7 from the early 60s and it’s knocking my socks off spinning Life’s Rich Pageant right now. The whole range is well represented, from low to high and crystal clear without being harsh or loose. I’m super into this set up. The power tubes are the smoked glass military issues and they also look rad, on top of the incredible sound. Would recommend.


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## E8ArmyDiver

Hi everyone..I'm glad to see this amp getting some love..I still have mine that I reviewed wayyy back,still with the Vintage Mullard tubes as in the review..It's been sitting in the box almost 2 years now as I moved to the iFi Stereo 50 & then the Quad VA-One so it only has a few hundred hours use...This week I bought new Harbeth M30.1 speakers so I'll be removing the 15wpc.VA-One & replacing with the Quad Vena II all Solid State with 3 times the power...Since I ADORE tubes I'm going to use the Pre Out to drive this amp..Still have the HE400i cans but upgrading to Ananda in just a few weeks...It really is a great little amp for Planar cans & I'm glad now it never sold...


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## Hippocamp

Free APPJ modding stuff

Did some modding a few years ago but my soldering skills were pretty raw, and ended up ruining the PA1502A. Now moved on to solid state only and no more modding.

If anyone here would like the APPJ for parts, plus some tubes and misc components, just PM me, and I'll send then along for the price of shipping.

Here's the extra stuff: 
3X of the Russian tubes (1 matched pair)
Pair of J&J 6L6GC
Tung Sol 3751
Mullard 12AX/ECC83
4X of Obligato premium caps
Pair of Kasei  25v1000 (one of leads broken)


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## Hippocamp

Shipping only to US or Canada (too complicated otherwise)


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## Makiah S

Coincidentally I'll be putting mine up for sale here soon


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## dpump

PM sent to Hippocamp for the amp and parts.


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## jekjek

My appj spoilt and i was about to get my second set of appj amp
Nice amp


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## baronbeehive

jekjek said:


> My appj spoilt and i was about to get my second set of appj amp
> Nice amp



You say spoilt, did you manage to get the circuit tested, that's all that's needed to find the faulty connection. Once that's done it can be repaired easily. Get the circuit continuity tested by someone, if you can't find anyone there must be someone, perhaps in the local college electronics dept. or a local audio club that could help you out. Good luck anyway!

This little top level amp could yet be improved!I'm thinking about replacing the Kaisei cathode caps with Nichicon Muse KZ's. I've already replaced my cathode caps in my LD amp, and they have made a considerable change to frequency extension from bass to treble for the better. So this would most likely improve an already top amp to top level, without a doubt! The Nichicons aren't expensive.

I love the sound signature of the amp so would not change but anyone considering changing theirs, I doubt you would better it, you would just change the sound somewhat, maybe to your liking, maybe not.


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## jekjek

baronbeehive said:


> You say spoilt, did you manage to get the circuit tested, that's all that's needed to find the faulty connection. Once that's done it can be repaired easily. Get the circuit continuity tested by someone, if you can't find anyone there must be someone, perhaps in the local college electronics dept. or a local audio club that could help you out. Good luck anyway!
> 
> This little top level amp could yet be improved!I'm thinking about replacing the Kaisei cathode caps with Nichicon Muse KZ's. I've already replaced my cathode caps in my LD amp, and they have made a considerable change to frequency extension from bass to treble for the better. So this would most likely improve an already top amp to top level, without a doubt! The Nichicons aren't expensive.
> 
> I love the sound signature of the amp so would not change but anyone considering changing theirs, I doubt you would better it, you would just change the sound somewhat, maybe to your liking, maybe not.



This amplifier is the one i enjoyed most
The 12ax7 just sound so complete in many ways as compared to other tubes

I am in a dilemma now as the cost to repair vs getting a new set from aliexpress is very very close


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## Hippocamp

Hippocamp said:


> Free APPJ modding stuff
> 
> Did some modding a few years ago but my soldering skills were pretty raw, and ended up ruining the PA1502A. Now moved on to solid state only and no more modding.
> 
> ...



Parts have been sent to a good home.


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## baronbeehive

jekjek said:


> This amplifier is the one i enjoyed most
> The 12ax7 just sound so complete in many ways as compared to other tubes
> 
> I am in a dilemma now as the cost to repair vs getting a new set from aliexpress is very very close



Yes, it is a great sounding amp, you have the tube realism, just put on some great female vocals like Bebel Gilberto for example to see what I mean, and yet it is a fast sounding amp with good resolution, whereas some are too thick sounding.

At least they don't cost a lot new, hope you make the right decision lol!


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## jekjek

baronbeehive said:


> Yes, it is a great sounding amp, you have the tube realism, just put on some great female vocals like Bebel Gilberto for example to see what I mean, and yet it is a fast sounding amp with good resolution, whereas some are too thick sounding.
> 
> At least they don't cost a lot new, hope you make the right decision lol!



They sound very good with this square getter baby


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## baronbeehive

jekjek said:


> They sound very good with this square getter baby



Looks like a GE, I like them, they have a good clean sound, similar to my Mazda, I use them on my other amp.

I still use the Philips and Mazda on this amp though. The 14AF7 is also used occasionally but is a bit too forward in the treble to use all the time for me.


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## jekjek

baronbeehive said:


> Looks like a GE, I like them, they have a good clean sound, similar to my Mazda, I use them on my other amp.
> 
> I still use the Philips and Mazda on this amp though. The 14AF7 is also used occasionally but is a bit too forward in the treble to use all the time for me.



I have ordered a new appj amp
I currently have 3 tube amps and 2 hybrid
But i find myself keep using APPJ and Musical Paradise MP301
Occasional use is the DV3322 and the rest is collecting dust


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## baronbeehive

jekjek said:


> I have ordered a new appj amp
> I currently have 3 tube amps and 2 hybrid
> But i find myself keep using APPJ and Musical Paradise MP301
> Occasional use is the DV3322 and the rest is collecting dust



NICE!!

.


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## wushuliu (Jul 26, 2019)

Anyone looking to do cap mods may want to grab some Miflex caps while their prices are still low. Cheapest Copper and Aluminum in Paper/Oil caps you can get right now and feedback so far is they are better than Jupiters. Even Tony Gee at Humblehomemadehifi has given them stellar ratings on his Cap Test page (and if you've never been to his Cap Test page you better start now...)


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## Pratt99

Thanks. Purchased the speaker version of this appj amp from tube Depot recently. They need a cap upgrade. Will take a look.


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## baronbeehive

wushuliu said:


> Anyone looking to do cap mods may want to grab some Miflex caps while their prices are still low. Cheapest Copper and Aluminum in Paper/Oil caps you can get right now and feedback so far is they are better than Jupiters. Even Tony Gee at Humblehomemadehifi has given them stellar ratings on his Cap Test page (and if you've never been to his Cap Test page you better start now...)



Hey, good info there wushuliu! Looks like they could compete with the Audyn's at least, I haven't seen anything on whether they are actually better than Jupiters. I put down the stellar performance of my amp to fitting these caps.



Pratt99 said:


> Thanks. Purchased the speaker version of this appj amp from tube Depot recently. They need a cap upgrade. Will take a look.



I am obviously interested in this, could you give a link to which version of the speaker amp this is as they have been upgraded since mine, (which is getting old)!

I urge you to fit quality caps properly, even if it means taking it to a professional. The amp will benefit enormously from such a simple upgrade.


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## Pratt99 (Jul 26, 2019)

@baronbeehive Here is the link,

https://www.tubedepot.com/products/tubecube-7-stereo-vacuum-tube-amplifier

Edit: This is the older version and must be the same as the one you have. Not the upgraded one.


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## wushuliu

baronbeehive said:


> Hey, good info there wushuliu! Looks like they could compete with the Audyn's at least, I haven't seen anything on whether they are actually better than Jupiters. I put down the stellar performance of my amp to fitting these caps.



I've seen two user reports recently at Audio Circle with members replacing their Jupiters with the Miflex, citing slightly more detail and resolution. Tony Gee has them ranked higher than Audyn Copper (12.5) and just about equal to Jupiter (13+ vs 13.5). I wouldn't recommend the Miflex necessarily to someone who already has Jupiters, but to anyone who is looking to up their cap game the Miflex can be had for 1/3 the cost of the Jupiter Copper...


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## baronbeehive (Jul 26, 2019)

wushuliu said:


> I've seen two user reports recently at Audio Circle with members replacing their Jupiters with the Miflex, citing slightly more detail and resolution. Tony Gee has them ranked higher than Audyn Copper (12.5) and just about equal to Jupiter (13+ vs 13.5). I wouldn't recommend the Miflex necessarily to someone who already has Jupiters, but to anyone who is looking to up their cap game the Miflex can be had for 1/3 the cost of the Jupiter Copper...



Interesting! Looks like they would do instead of Jupiters for some people wanting something a bit less pricey.




Pratt99 said:


> @baronbeehive Here is the link,
> 
> https://www.tubedepot.com/products/tubecube-7-stereo-vacuum-tube-amplifier
> 
> Edit: This is the older version and must be the same as the one you have. Not the upgraded one.



Ah right, I'm very pleased to see my version is still being made, albeit rebadged now. I'm a bit less worried in case anything should go wrong with mine.

Good review too! His point about the slight roll off at the top, I don't find now with the upgrades, treble response is very satisfying, and the upgraded coupling caps has meant that the bass response is also fuller with the different rated capacitance. So the upgrades has meant better frequency response all round.

His other point about the low power output has also been addressed. So long as transient recovery is as efficient as possible the power ratings are fine. We've put in higher rated capacitance here as well for the cathode caps and this helps here.

People are beginning to wake up to the advantages of lower output amps. High power means having to control frequency response to stop it going haywire. This is done using negative feedback, too much negative feedback gives the characteristic cold analytical SS sound with the closed in soundstage. This is why tube amps are so good at soundstage. Also high power leads to unwanted EMF effects and so other stages are used in the amp to control this. So low power does away with these disadvantages. If transient recovery is super efficient then low power amps can play surprisingly loud.

Edit: I have a couple of Kaisei 1000uF cathode caps if anyone wants, I cut the legs short but wires can easily be soldered on.


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## wushuliu (Jul 26, 2019)

The APPJ PA1501A can also be ordered Prime on Amazon for $179 [EDIT: Just realized this is not the same as the amps being discussed, it's newer]. The 1502A headphone version however is getting harder to find. They are much more expensive on Ebay. I just ordered one on Amazon for $199 shipped which is the cheapest I could find. I also have a Project Sunrise kit on the way. We'll see how they compare.


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## Pratt99

wushuliu said:


> I also have a Project Sunrise kit on the way. We'll see how they compare.



Will look forward to your thoughts. I also have a semi-upgraded 1502A ( only replaced the coupling caps). I think the upgraded appj will have the edge terms of clarity. However, you might like the sunrise for other reasons.


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## wushuliu

The PA1502A arrived. Nice packaging. Cute little amp. I gave it about an hour to cook and took a listen. The stock 12AX7 has so much gain and the typical grainy borderline shrill mids I remember from my tube diy days some years ago. I pulled it out and replaced with an EH 12AY7 I had laying around. MUCH better. Let it cook some more overnight and now the amp is showing some promise. More balanced, lots of power to drive an HD650/6XX. Noise floor could be lower and the separation/soundstage is lacking but for $200 and one tube swap it sounds great. Very engaging. I think I have to decide whether committing to all kinds of tube rolling and modding will be worth it vs. my current modded JLH-based amp which sounds excellent or the forthcoming Project Sunrise.


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## baronbeehive (Aug 4, 2019)

wushuliu said:


> The stock 12AX7 has so much gain and the typical grainy borderline shrill mids I remember from my tube diy days some years ago. I pulled it out and replaced with an EH 12AY7 I had laying around. MUCH better.



As you say, tube issue. The amp is refined sounding, not shrill, yet still with the detail and dynamics (modded). You could try TS5751's, very smooth, and lower gain. For other recommendations look back a few pages.



wushuliu said:


> Noise floor could be lower and the separation/soundstage is lacking but for $200 and one tube swap it sounds great.



The amp should be totally silent, ask other members, probably tubes  again. Separation and soundstage are vastly improved by cap and tube upgrades. Also let it cook for some more hours yet!



wushuliu said:


> I think I have to decide whether committing to all kinds of tube rolling and modding will be worth it vs. my current modded JLH-based amp which sounds excellent or the forthcoming Project Sunrise.



As I said I have a pair of Kaisei 1000uF cathode caps, same as I used in mine. Then you would need something like Audyn True Copper 0.1uF's as bypasses. Also I have a pair of Russian Russia 6F6C Kobra power tubes recommended a while back for improved soundstage. Then you would need, say, a pair of the Miflexes coupling caps that you mentioned, say $100 the lot for the upgrades!

If anyone is interested in the parts that I have lying around for the cost of postage drop me a PM.


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## wushuliu

Got the Sunrise up and running and it's already impressive - and that's with the APPJ's 12AX7 as the test tube no less, which now sounds great in this application. The soundstage is more in line with my preferences. More importantly, I can bypass input caps altogether, change gain and impedance however I want, Use 6v AND 12v tubes and most crucially - improve the power supply. All without panicking about breaking leads and access to the internals.

I can only hold on to one of these and I think it's going to be the Sunrise.


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## Maxx134 (Aug 7, 2019)

I still using the Gold Lion KT66 on the output tubes,
even though it wasn't recommend because of heater amp draw is higher than the new production kt66, or other tubes recommended.

It combines the clarity of the Russian , with the soundstage of the duller large tubes I mentioned before.

It ran a bit hot in my warm room, but extended listening in my air condition room it is steady warm and tube still touchable, (quickly lol).
These are my fav tubes.
Very musical with clarity , if you don't mind taking the risk.


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## baronbeehive (Aug 9, 2019)

Hi Maxx!

Looks like you're still using the 14F7. I'm settled on my final tube combo, I still use the Philips 12AX7, surprisingly good for that tube type. In my setup I find the 14F7 just a tad treble centric although resolution is fantastic. Also the Philips is beautifully rich sounding.

This amp really is something, when you have the textural detail and realism that this has now you know that it is pretty special.
.

Edit: perhaps you could fry your breakfast egg on your amp with the Gold Lions in lol!


----------



## baronbeehive

wushuliu said:


> Got the Sunrise up and running and it's already impressive - and that's with the APPJ's 12AX7 as the test tube no less, which now sounds great in this application. The soundstage is more in line with my preferences. More importantly, I can bypass input caps altogether, change gain and impedance however I want, Use 6v AND 12v tubes and most crucially - improve the power supply. All without panicking about breaking leads and access to the internals.
> 
> I can only hold on to one of these and I think it's going to be the Sunrise.



Glad you've made your decision, having the amp in kit form looks like a good idea as you say, upgrading your power supply especially could be useful, also changing the other settings.


----------



## wushuliu (Aug 9, 2019)

baronbeehive said:


> Glad you've made your decision, having the amp in kit form looks like a good idea as you say, upgrading your power supply especially could be useful, also changing the other settings.



Yes, the APPJ has not been so accessible for me. I don't know if they changed enclosure parts recently but I couldn't even get inside the chassis because the heads of the cheap screws immediately started stripping (tried multiple screwdrivers and multiple head sizes) : (


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## baronbeehive (Aug 10, 2019)

wushuliu said:


> Yes, the APPJ has not been so accessible for me. I don't know if they changed enclosure parts recently but I couldn't even get inside the chassis because the heads of the cheap screws immediately started stripping (tried multiple screwdrivers and multiple head sizes) : (



Right! Swopping out the caps was simple but it is made tricky because of the fragile nature of the PCB inside, also the other components are surface mount so would not be easy to change like in a kit such as the Project Sunrise. Several of us ran into problems over this further back in the thread, plus Maxx and myself had to rebuild the chassis to accommodate the upgrades.

Project Sunrise looks to be an interesting idea, not sure if I would be happy with an open chassis though! Let us know your impressions when you've had time to listen to it.

Edit: Is that you or Roger Waters in your profile pic? Just asked because I'm a big fan of Pink Floyd, I played my fav album "Pulse" a couple of days ago in fact, I love it!


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## baronbeehive (Oct 10, 2019)

Can't remember exactly how long I've had this speaker APPJ for, (PA0901A), but it must be not far short of 10 years, and the other amp I have, the Little Dot MKV+ for several years longer than that. Both are modded with the LD having a far greater number of upgrades than the APPJ which was relatively simple to do, it only requires upgraded coupling and cathode caps. The caps should be of best quality possible to affect sound beneficially, so the Miflex's that member Wushuliu mentioned could be a good bet for coupling, and the Kaisei's for cathodes are fairly cheap but good.

As I've had the amp for quite a while now I'm in a good position to to evaluate it properly, and I've got used to using different tubes from what I started out with so I thought it might be interesting to do a summary of my impressions of the amp now for anyone interested... if there's still anyone out there that is! I know there are a couple of members with that version APPJ.

Build: To answer a question from a member a while back I can say that the amp is reliable.... touch wood.... the upgrades have made no difference to this. This is good because the internals, being surface mount are not really made for modding but if they're left alone should last really well. But if the upgrades are done with care that shouldn't affect this,  however I managed to mess it up, along with several other members! So build quality is not bad.

Pairing: It should pair well with anything from simple no crossover to multiple crossover amps, mine is single crossover, from sensitivities from about 85db upwards, mine is 87db and people have said it shouldn't work with such a low sensitivity, 90-95 would be much better. My answer to this is it works fantastically well, I use it in my average sized dining room, I like it quite loud and I never feel the need to go past 12 oclock so plenty in reserve. It doesn't clip or distort at all and is dead quiet. It would pair with warm or more neutral speakers, mine are fairly warm sounding.

Sound: The sound is beautifully balanced, liquid with good frequency response pre mods. Post mods it just pushes everything to the max, soundstage, resolve, textural detail, dynamics, frequency extension are all top level. The sound is transparent but with a nice touch of tubes, but it is not over warm or syrupy.

Comparisons: From reviews and my own experience I would put this at top level post mods. Other amps may be more neutral, or more tubey sounding according to taste. To see it compare favourably to the much more expensive and highly modded Little Dot is pretty impressive and difficult to believe.

Tubes: I think I'm in a good position to know what my preferences are now I've lived with them for several years. I won't go into past tubes, people can look back in the thread for that. So starting with my previous favourite the Tungsol 5751 has a glorious liquid, yet detailed sound. The TS14AF7 has great resolve, detail, treble, transparency, I thought it was slightly thin occasionally and one dimensional soundstage, but still excellent, Philips 12AX7 has great punch richness, resolve, textural detail, frequency extension, 3d soundstage. The Mazda 12AX7A silver anode is lighter and taughter sounding with light extended treble, great resolve, really open soundstage, there is a really exciting percussive edge to the upper register like when a real guitar is being played near by. Can be a tad thin on thin sounding music but on most music sounds quite brilliant IMO with great textural detail. That and the Philips are my fav tubes now... with the Philips in top position. This tube is the best I have heard, and it is unlikely to ever again come out of it's socket on the amp. It has texture in abundance, the frequency extension is impressive with powerful bass, mids and treble all in perfect balance. The tube has much of the percussive attack of the Mazda but is better for all types of music due to its richer tonality whereas the Mazda can be on the light side. The dynamic response of the tube and all that textural detail all go to making the soundstage impressive and many layered although it is not so open sounding as the Mazda. I think the Philips is perfect for this amp because the amp naturally has a tight attack and quickness of response, therefore the fuller sound of the tube makes for a better combination on the amp. This is the best ever sound I have heard coming out of this little amp. I think I have finally overcome my prejudice against the 12Ax7 tube which I now regard as a superb tube taking into account all the variants we have gone into here, and it is known to be a very linear tube.

I've gone into this at length because having lived with the amp and tubes for some time now I feel in a good position to comment finally on the setup we have here.

That's where I'm at atm and I doubt anything will change as I'm very happy with the amp. I would be interested to hear what others with the headphoe APPJ, the subject of this thread thought in comparison.

I believe this amp displays all the best qualities of SET tube amps: speed, openness, transparency, and the SQ indicates to me that the transformer is good quality too, which is fortunate on output.

Edit: I added a concluding section to the paragraph on tubes...


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## greinedo (Jan 10, 2020)

Dear Head-Fier,

This is my first post here.

I wanted to register in order to thanks everybody for giving me the idea to modify my venerable APPJ PA901A I own since several years. Currently my tube setup is Psvane 12AX7-T/2 + EL84M from TAD. Sounds very nice to me, although there might be better options.

I already played a lot with caps on my DAC I build on my own but never dared to touch this small tube amp. The posts I read here gave me some encouragements and I took the opportunity of day-off around Christmas to do it. The components I choose are on a rather cheap side. Fitting inside was also a consideration :

- Jantzen Superior Z-cap 0.47µF for decoupling
- Jantzen Superior Z-cap 0.1µF + Panasonic FM 1000µF 50V for the cathode bypasses

The result is is already amazing, although not burned-in. After several years using this toy I'm really impressed with the musicality.

Before  : 

 


After :


----------



## greinedo

Small update :

After 50+ hours of listening, the musicality has really improved. Seems Jantzen or Panasonic caps or both need burn-in time.

I was still a little bit disturbed by a not even left-right music thing, something in the stereo image. Therefore, I decided to bypass the onboard pot by cutting some traces in order to isolate the pot and wiring direct to 12AX7 pins.

That was again a very good modification. Because stereo image improved nicely. Seems my pot was a bit defective or bad quality.

I purchased an ALPS potentiometer in order to build an external volume device. But I wonder if I ever will use it. The digital volume of my setup (LMS with PicorePlayer) is already sounding very good, I'm not sure inserting an analog device will improve. But now, I'm worrying about the 2 cheap RCAs. May be for next time.

I'm currently feeding the APPJ PA901A with my dac prototype based on a raspberry, an allo kali, an I2S home made AK4497 dac and output stage with bursons v6 and other things I tuned a lot. And connected to 94dB hand made speakers.

Since I have finally found how to insert images directly, here the last modification and my playground.


----------



## baronbeehive

greinedo said:


> Small update :
> 
> After 50+ hours of listening, the musicality has really improved. Seems Jantzen or Panasonic caps or both need burn-in time.



Hi greinedo, nice work!

I will reply to you as I have that APPJ, and there are only one or two people left on this thread now, partly because of the age of the amp and it has had several new versions since then, (which I'm rather sorry about)!

Glad you like the amp, it is pretty amazing! I am continually being shocked by it, even now after about 10 years of ownership!

The Jantzen caps you used look to be fine, the right values to boost bass performance and the cathode caps at 1000uF will give power a boost to avoid clipping and improve transient response, given that this is a relatively low power amp, (which is not a problem because low power often means clean power). Together with the bypasses to boost the faster treble frequencies is what is needed here.

I found burn in time improved the soundstage airiness and clarity especially, but for the Jupiter and Kaisei caps I have put in they need into the hundreds of hours before I really started to notice it big time.

The upgrades are really worth it for this little baby amp.



greinedo said:


> I was still a little bit disturbed by a not even left-right music thing, something in the stereo image. Therefore, I decided to bypass the onboard pot by cutting some traces in order to isolate the pot and wiring direct to 12AX7 pins.
> 
> That was again a very good modification. Because stereo image improved nicely. Seems my pot was a bit defective or bad quality.
> 
> I purchased an ALPS potentiometer in order to build an external volume device. But I wonder if I ever will use it. The digital volume of my setup (LMS with PicorePlayer) is already sounding very good, I'm not sure inserting an analog device will improve. But now, I'm worrying about the 2 cheap RCAs. May be for next time.



Changing the pot has been mentioned but as far as I know nobody has actually done it due to the lack of space, and if you're not getting any problems it's best left. As the amp is autobiasing you can't adjust it by any other means. Digital volume seems a fine compromise.



greinedo said:


> I'm currently feeding the APPJ PA901A with my dac prototype based on a raspberry, an allo kali, an I2S home made AK4497 dac and output stage with bursons v6 and other things I tuned a lot. And connected to 94dB hand made speakers.



Good work on the DAC, did you make the speakers too?

Let us know your impressions through your speakers after more burn in time, I am interested to know as mine are only 87db but are absolutely stunning quite frankly!

Also any questions about tubes etc., but there is a lot about that back in the thread.


----------



## greinedo

Hi baronbeehive, Thank you very much for the reply !



baronbeehive said:


> Glad you like the amp, it is pretty amazing! I am continually being shocked by it, even now after about 10 years of ownership!



Yes, I'm addicted to this sound. Not sur it's triode wired or penthode but I like it so much. Unfortunately, the fragile and compact build doe not allow a lot of tweaks. I'm tempted rebuilding something from scratch similar by starting building a kit, then modifying it, like this one : https://www.loetstelle.net/projekte/el84compact/el84compact.html (sorry in German) and pcb, high quality transformer etc here in section tube accessories : https://www.die-wuestens.de/eindex.htm.

I already assembled 3 solid state amplifier since I own this little tube amp but they never came close to the appj. 2 TA2020 amplifiers and one based on TI chip TPA3251. All 3 landed in the basement where I already stored my Onkyo AV receiver when Appj came.



baronbeehive said:


> As the amp is autobiasing you can't adjust it by any other means. Digital volume seems a fine compromise.


Indeed. I realized only after modification that there is now direct connection from dac output stage (burson op amp) without any resistor or coupling cap until 12ax7 pin and bias resistor (240kOhms). Before, the pot was 10kOhms. So there is a change in layout but sound is just better, and I will stay like this.



baronbeehive said:


> Good work on the DAC, did you make the speakers too?


No, thats certainly a long work. They have been made in the 90's by a passionate guy who even invented a patented wave guide inside the speaker. This sounds soo good. A bit off topic here but fyi a english guy reviewed a newer model (only 92db) and thinks the same. https://vintagehifiproducts.wordpress.com/2012/10/07/mulidine-cadence/ For me they are ideal speakers for small tube amps. And fyi my extravgant dac with 7 linear power supplies in flea market case  :  https://drive.google.com/open?id=14bFmckb2tfy8VZbMCKlKslzDEZmzgHno and not very transportable !

I will give feedback when things are stable I'm really interested in advise concerning good sounding EL84 and 12ax7 tubes. I'm already very convinced with s EL84M/6П14П and I'm lurking on a 12ax7 Full Music tube : https://www.tubeampdoctor.com/en/tj-full-music-12ax7 May be someone has an opinion.

Thank you again very much for this thread. There is a lot inside very interesting and a lot I still must read.


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## baronbeehive (Jan 11, 2020)

greinedo said:


> Yes, I'm addicted to this sound. Not sur it's triode wired or penthode but I like it so much. Unfortunately, the fragile and compact build doe not allow a lot of tweaks. I'm tempted rebuilding something from scratch similar by starting building a kit, then modifying it, like this one : https://www.loetstelle.net/projekte/el84compact/el84compact.html (sorry in German) and pcb, high quality transformer etc here in section tube accessories : https://www.die-wuestens.de/eindex.htm.



Pretty sure its triode. I was impressed that you had no problems with your upgrade!

Most of us here ran into problems due to the flimsy PC. Not sure you need a lot of tweaks anyway, the sound of this amp compares favourably to my much more heavily modded Little Dot MKVI+. The only other mod I've heard of is a diode mod which I gather involves a faster acting diode, but as the amp itself is very fast and open sounding as a typical SET amp, so it probably doesn't need it.

If you're interested in an amp build check out this one: https://www.head-fi.org/threads/modern-balanced-tube-amp-build.852879/
It is a modern hybrid tube amp designed by someone who I heard of through the Little Dot Supermod thread. He had some interesting ideas which another member of the thread has put into practice. I have no relationship to this person who does the amp build, but am very interested in trying it myself. This is a review thread of theamp: https://www.head-fi.org/threads/oblivion-ultrasonic-studios.902926/



greinedo said:


> I will give feedback when things are stable I'm really interested in advise concerning good sounding EL84 and 12ax7 tubes. I'm already very convinced with s EL84M/6П14П and I'm lurking on a 12ax7 Full Music tube : https://www.tubeampdoctor.com/en/tj-full-music-12ax7 May be someone has an opinion.



Look forward to hearing your impressions!

Re: tubes I swear by Amperex EL84, they're the best I have heard, clear and warm sounding. The only ones I haven't heard and was interested in were the Mullards but as I already have Mullard sounding 12AX7's I haven't bothered.

What type of sound do you like? I refer you back to my long review post on this page for the conscensus here, and also my preferences. If you do like the sound of the Philips make sure you get the right one, see back in the thread for the info. The Full Music 12AX7's are quite good reissue tubes but nowhere near as good as NOS.

With the upgrades and better tubes, I'm certain that this little gem, no pun intended, will hold up to the very best, and it has a sound signature that I love!

I'm interested that you have the speaker version as well, as most members here have the headphone version.


----------



## DavidK35

baronbeehive said:


> Hi greinedo, nice work!
> 
> I will reply to you as I have that APPJ, and there are only one or two people left on this thread now, partly because of the age of the amp and it has had several new versions since then, (which I'm rather sorry about)!
> 
> ...





Still here, with the cap mod & original amp. Enjoying it as much as first day. After trying a whole host of tubes (earlier in the thread) settled on the 14N7 as driver & the unbeatable 6BG6G coke bottle
power tubes. Spacing very tight but works fine. Shame they changed the design, mine's a keeper.


----------



## baronbeehive

DavidK35 said:


> Still here, with the cap mod & original amp. Enjoying it as much as first day. After trying a whole host of tubes (earlier in the thread) settled on the 14N7 as driver & the unbeatable 6BG6G coke bottle
> power tubes. Spacing very tight but works fine. Shame they changed the design, mine's a keeper.



Hi DavidK35, good to hear from you again, hope your granddaughter is letting you use your headphones once in a while lol!

The amp looks awesome!

Yes I don't see why they changed it, how can they improve on perfection.
.


----------



## rdale

DavidK35 said:


> Still here, with the cap mod & original amp. Enjoying it as much as first day. After trying a whole host of tubes (earlier in the thread) settled on the 14N7 as driver & the unbeatable 6BG6G coke bottle
> power tubes. Spacing very tight but works fine. Shame they changed the design, mine's a keeper.


I’m a happy owner of both the speaker APPJ amp, a Miniwatt N3, and the headphone one that is in the title of this thread. I use Psvane EL84s and 12XA7 with my PA0901A which gives it very high resolution and a really warm rich treble. I’m pleased to say that the amp is still available, it is called the TubeCube 7 for $180:

https://www.tubedepot.com/products/tubecube-7-stereo-vacuum-tube-amplifier


----------



## DavidK35

baronbeehive said:


> Hi DavidK35, good to hear from you again, hope your granddaughter is letting you use your headphones once in a while lol!
> 
> The amp looks awesome!
> 
> ...




Yes, she does now & then LOL. When I play through loudspeakers she likes to adjust her position and stand dead centre in the sweet spot, instinctively knowing
about the "stereo" effect.


----------



## greinedo

baronbeehive said:


> Pretty sure its triode. I was impressed that you had no problems with your upgrade!



Today, I placed an external potentiometer, when he came, and  finally, it seems a bit better. Music is by comparison a very little dry without any pot. Then, with my wife we listen complete old Persuasive Percussion Vol 2 - Enoch Light, and it was huge music in the living room ! So realistic.
I made a mistake while ordering. Original pot was 10k, now it's 50.


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## jekjek (Jan 20, 2020)

My turn to mod my second APPJ
Fingers crossed





Clean up the board
And managed to fill it up


 
But there is a continous hum coming from the left channel

It doesn't change when i move the volume pot


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## baronbeehive (Jan 20, 2020)

Hi jekjek!

I will have a proper look when I have time but for now I need to know a couple of things:

Does the amp work despite the hum?
It looks like you cut the legs of the original caps? That's ok.
When you soldered the new caps did you take the top off the chassis as well as the bottom? If you take the top off you should be able to see if the solder points look good and that the round copper pads have not come off with too much heat or pressure. If they look ok we will assume the circuit is ok for the moment.
Did you fit the cathode caps the right way around with the negative as shown in this pic the white band at the bottom in this pic which I have borrowed from another member:



*
I must give a warning never to touch anything inside while it is switched on or for about half an hour after you switch off to allow the caps to discharge.
*
Until the amp is working properly I wouldn't keep it switched on for too long!

I'll get back to you when I have time .

Edit: The only way to check the circuit properly is with a digital multimeter such as this: https://www.amazon.co.uk/Neoteck-Multimeter-Resistance-Voltmeter-Laboratory/dp/B01N9TRQI1/ref=sr_1_2_sspa?crid=NCNFJ31YDC8I&keywords=digital+multimeter&qid=1579559632&sprefix=digital+mul,aps,229&sr=8-2-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEzRjNNWlJaOEZVMlFWJmVuY3J5cHRlZElkPUEwNTYwNjUxUlRPTkJKUzVaTlFRJmVuY3J5cHRlZEFkSWQ9QTAxMDQzOTEyM0JDSE9PM1ozV1k0JndpZGdldE5hbWU9c3BfYXRmJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==

You can then check the solder points with other connections in the same trace *- with the amp off -* and if they have continuity as measured by the DMM then you know the connection is ok!


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## baronbeehive (Jan 20, 2020)

Where I've marked in red it is possible from what I can see that the round pads might be damaged, the others look ok. The way to tell is by looking closely at the solder points to see if the pads have come away partially from the board, preferably with the solder removed so you can see better. Where I've marked in blue there are 2 points that are connected along the green trace. If you had a multimeter you could check these 2 points for continuity. If the meter shows continuity you can be fairly sure that the solder points are good and therefore the circuit is good there. If there is no continuity then there is a break in the circuit and it needs to be fixed.





When you've looked at your soldering let me know if you think there is a problem there and we can take it from there. Look at the bottom of the PCB as in the pic, and also look at the same points from the top of the amp because these need to be good too.


----------



## jekjek

baronbeehive said:


> Where I've marked in red it is possible from what I can see that the round pads might be damaged, the others look ok. The way to tell is by looking closely at the solder points to see if the pads have come away partially from the board, preferably with the solder removed so you can see better. Where I've marked in blue there are 2 points that are connected along the green trace. If you had a multimeter you could check these 2 points for continuity. If the meter shows continuity you can be fairly sure that the solder points are good and therefore the circuit is good there. If there is no continuity then there is a break in the circuit and it needs to be fixed.
> 
> 
> 
> When you've looked at your soldering let me know if you think there is a problem there and we can take it from there. Look at the bottom of the PCB as in the pic, and also look at the same points from the top of the amp because these need to be good too.



Thanks baron
Despite the hum, the amplifier works fine
I can almost accept it as it does not interfere with the music
I get fuller body music with this setup than what i get with the previous capacitors (wimas and panasonic)

I will continue to troubleshoot it this weekend and if I'm not able to resolve this, i might have to send it tube amp repair guy

The hum was on the same level despites of the volume change


----------



## jekjek

I connect a jumper cable highlighted in red because i yanked out the lead in the earlier mod
but I didnt have any humming back then

i will try to move one of the jupiter capacitor away from the yellow transformer and will see if the humming continues


----------



## baronbeehive

jekjek said:


> Thanks baron
> 
> I will continue to troubleshoot it this weekend and if I'm not able to resolve this, i might have to send it tube amp repair guy



No worrries

Yes do that, or a TV repairman, or anyone who can troubleshoot PCB's.



jekjek said:


> I get fuller body music with this setup than what i get with the previous capacitors (wimas and panasonic)



Yes, you have a set of top capacitors there so the amp will be elevated to top level status. Jupiters are excellent for realism and the Nichicons will increase bass definition as well as sharpness and boost power. You will notice the sound improving more and more as the amp burns in.




jekjek said:


> Despite the hum, the amplifier works fine



If you notice anything that's not right such as burning, fluctuating sound, sound imbalance between left and right etc., switch off immediately. You have such a nice choice of components now I would hate to see anything nasty happen.

I'm assuming that you have connected those 2 points indicated by the red line with wire, because the trace was damaged. Yes that looks right according to that trace

I can't emphasise enough that a DMM would be very handy to check these things yourself.

Also, very important, those components will be exposed at the bottom of the amp. This is extremely dangerous because, if you're like me fumbling with the amp's volume in the dark you will be exposed to very high voltage so I would close that however you see fit.

I think you might be fairly new to this so I will prepare a checklist later of things to do.
.


----------



## baronbeehive (Jan 21, 2020)

Hey jekjek!

Just checked your pics of your mods and it looks to be good!

From what I can see you've got the cathode caps in the right way round, also the bypasses look to be correct (negative to negative from bypass to cathode cap). Nice work!

Your soldering is much improved over the last time LOL!

From what I can see everything looks good, but it can be difficult to check for faults.

Check the wiring is not touching anything metal, also check no wires are broken, including other wires on the inside. I had a wire from the inside to the transformer break.
Check the soldering is secure
Check the joints are good and not loose
The make sure there is no loose bits of solder lying around on the PCB.

A final check would be to check the solder joints you did for continuity with other connections in the same trace *on both sides of the PCB* with a DMM, this would reveal any problems you can't see. I think this is the most likely thing to go wrong because any damage to the connections on the PCB is difficult to see.

Let me know if everything is alright after your next check.
.


----------



## jekjek

This morning the tube amp repair guy call me up and asked to repair the amp myself..
I am a bit puzzled by his request thus i went over his place and he showed me one of the jupiter caps was picking up the buzz from the transformer. He asked me to repair it myself 
Lol
So this is how the amp looks like now after another rearrangement 


 

The hum on the left side is gone now but some faint hum is coming on the right side 
Looks like I'm going to be busy this weekend


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## Maxx134 (Jan 24, 2020)

jekjek said:


> he showed me one of the jupiter caps was picking up the buzz from the transformer.



Since it is not polarized, reversing the coupling cap usually said to help.

One lead of the cap is usually connected to the outer area of cap.
Some ppl like to connect that outer shield lead to driver tube, so the power tube input gets the inner part of the cap.

I have no comment about it as  I have not tested that.



jekjek said:


> The hum on the left side is gone now but some faint hum is coming on the right side
> Looks like I'm going to be busy this weekend


Yep..

The story with this amp, is that in stock form, the bottom lid closes all the way, and effectively _shields _the power supply section, which is a  "switching" PSU .
So you can try to help with shielding if you like, by moving caps away and/or covering the PSU section, but be careful not to short anything out with any added metal.


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## Maxx134 (Jan 24, 2020)

I bought some new coupling caps for this amp (clarity CMR), to see if I can  help increase the soundstage.

Here is a funny pic for you.
Expensive driving cheap!
Nice.


For the 1502 model, Most of the good tubes on my amp are a bit forward with the exception of the Gold Lion KT66, which runs hotter than the rest..


----------



## baronbeehive (Jan 24, 2020)

Maxx134 said:


> I bought some new coupling caps for this amp (clarity CMR), to see if I can  help increase the soundstage.



Hey Maxx!

See if you can put those caps in without trashing the PCB this time LOL!



Maxx134 said:


> Here is a funny pic for you.
> Expensive driving cheap!
> Nice.



Wow I never realised that was so expensive, well... the APPJ *is* expensive... in performance anyway.



Maxx134 said:


> For the 1502 model, Most of the good tubes on my amp are a bit forward with the exception of the Gold Lion KT66, which runs hotter than the rest..



I haven't found any Gold Lions for my amp, not sure they do 12Ax7's. I doubt if yours would run hotter than the Little Dot with 6 big bulb tubes anyway.


----------



## baronbeehive

Maxx134 said:


> The story with this amp, is that in stock form, the bottom lid closes all the way, and effectively _shields _the power supply section, which is a  "switching" PSU .
> So you can try to help with shielding if you like, by moving caps away and/or covering the PSU section, but be careful not to short anything out with any added metal.



Yes he could move the caps out of the way of all that EMF coming from the transformer coil, and out of the PSU section altogether.

If the caps don't fit so well he could extend the bottom like we did with a box of aluminium heat sink sheets screwed together.


----------



## baronbeehive

jekjek said:


> This morning the tube amp repair guy call me up and asked to repair the amp myself..
> I am a bit puzzled by his request thus i went over his place and he showed me one of the jupiter caps was picking up the buzz from the transformer. He asked me to repair it myself
> Lol



Yes, repair guys can be a bit sniffy about working on modded amps.

When you move the caps be careful to check that the solder connections haven't become loose or broken. Also when you bend the cap legs be careful they don't break, it is best to bend them away from near the cap body.


----------



## baronbeehive

Don't bend the legs like this near to the cap body. Now that you've done it I wouldn't bend it again from there, I broke a leg like this, which was expensive!


----------



## baronbeehive

Also check this solder joint when you move the caps, it looks a bit dodgy from here, but maybe OK.
.


----------



## jekjek

After a few trial and error on Jupiter caps and Mundorf
I gave up and fix the Wima back on the amp
To my surprise the hum was gone. So now I am a happy APPJ owner again


----------



## baronbeehive

jekjek said:


> After a few trial and error on Jupiter caps and Mundorf
> I gave up and fix the Wima back on the amp
> To my surprise the hum was gone. So now I am a happy APPJ owner again



OK .

The original is still very good as I remember, maybe keep the project for the future?

Glad everything is still working fine.

Don't know what could have caused that other than where you put the caps, in the PSU area was not a good idea, the switch mode power supply does voltage conversion constantly which causes a lot of noise which is usually out of range of hearing.

I would suggest if you do that I future to get the DMM though. If you have that it is easy to check if the connections are still good after you have done anything to the amp, in which case everything should still be OK.

So enjoy your amp…!


----------



## jekjek

thanks Baron
the amp is still very good with Wima


----------



## Maxx134

jekjek said:


> thanks Baron
> the amp is still very good with Wima


There are even better wima higher pulse rating and, also, the blue ones.
Same size.


----------



## 1800yolk

Hi guys!
I remember coming to this thread about 3 or 4 years ago and reading it a lot before purchasing this amp. I saw that it would be a great companion for my HE-400i headphones & Bimby DAC, and they definitely have been! Another thing that caught my eye was the fact that I could make changes to the sound by buying new tubes and possibly swapping out the capacitors. Well, as much as I've wanted to all this time I've never had any money to buy anything for it! I still don't have much money to throw at it, but 

if you could spend around $50 on replacement tubes, which ones might you go for? Main goal is to find something clear but also warmer in the high 10khz+ frequencies would be nice.

Thank you!! I'll be reading older posts to try to find a good option but it is a lot to sort through


----------



## Makiah S

It's not a triple Mica but I picked up both a 6072A 5 Star [1875/1875] and a non 5 Star for comparison (From Doug's Tubes with the Balanced Triodes option picked)

So that'll be fun, I'll be comparing them again'st my 100%/100% Sylvania 12SL7GT


----------



## baronbeehive

1800yolk said:


> Hi guys!
> I remember coming to this thread about 3 or 4 years ago and reading it a lot before purchasing this amp. I saw that it would be a great companion for my HE-400i headphones & Bimby DAC, and they definitely have been! Another thing that caught my eye was the fact that I could make changes to the sound by buying new tubes and possibly swapping out the capacitors. Well, as much as I've wanted to all this time I've never had any money to buy anything for it! I still don't have much money to throw at it, but
> 
> if you could spend around $50 on replacement tubes, which ones might you go for? Main goal is to find something clear but also warmer in the high 10khz+ frequencies would be nice.
> ...



Ha, nice to see this thread still trundling along periodically!

Sorry for the late replay, most of the information can be found a few pages back, but I will try to answer. Difficult because there are several types of "warm". For driver tubes, Sylvania, 12AX7, or better triple mica 5751, are warm and bright, especially in the high frequencies. They are a tad light sounding, Mullard, ECC83 are warm in the soft cosy blanket sense if you see what I mean. I really like the Mazda,12AX7A silver anode for warmth, with a delicate sound with clearly defined edges to the sounds, they might be a bit expensive though. I managed to get more warmth with the power tubes, but I won't recommend these as they are different to the types you have on yours.

So check out the last pages and see if there are any power tubes back then that would suit.

Glad to see you are enjoying the amp!


----------



## baronbeehive

Mshenay said:


> It's not a triple Mica but I picked up both a 6072A 5 Star [1875/1875] and a non 5 Star for comparison (From Doug's Tubes with the Balanced Triodes option picked)
> 
> So that'll be fun, I'll be comparing them again'st my 100%/100% Sylvania 12SL7GT



Hey Mshenay!

So you've still got your APPJ, it must have made a bit of a impression, I thought you had replaced it!

I haven't come across the 6072A's but I imagine they would be totally different to the 12SL7 Sylvanias. The different gain and other factors could make this tube quite interesting.


----------



## Makiah S

baronbeehive said:


> Hey Mshenay!
> 
> So you've still got your APPJ, it must have made a bit of a impression, I thought you had replaced it!
> 
> I haven't come across the 6072A's but I imagine they would be totally different to the 12SL7 Sylvanias. The different gain and other factors could make this tube quite interesting.




Well I've been wanting to get rid of it but my guy has been fine-tuning his amp for a year now

I'm experimenting with an Auris Euterpe as a potential replacement go with the stock JJ tubes it's unimpressive, or it's a bit too full for my taste though I don't think it's going to take much to push it over the edge

And I actually did purchase a triple Mica an 80s double Mica and five star, I found that I tend to like the 12A U7 and these are apparently an  ay7 which has a slightly higher gain than the AU series but not as much as the AT definitely not as much is the AX

And I will again be comparing them against my Psvanne 12au7 and 12SLGT7


----------



## Maxx134

Mshenay said:


> And I will again be comparing them against my Psvanne 12au7 and 12SLGT7


I have plenty of the 12 pin types then I will be putting up soon in the for sale threads, and I have to say the older the tube, the better sound...

 so late production tubes are not as good as the oldest ones.
C
Don't ask me why it is, but that is what it is...

That's a general statement, but it can almost be considered a fact(!), because of how prevalent it is.
Oldest tubes are usually the best.


----------



## Makiah S (Jun 18, 2020)

Maxx134 said:


> I have plenty of the 12 pin types then I will be putting up soon in the for sale threads, and I have to say the older the tube, the better sound...
> 
> so late production tubes are not as good as the oldest ones.
> C
> ...



well I should be in for a treat, the GE Triple mica is what a late 50s early 60s, vs the 80s Double Mica

one theory I heard had to do with the level of precious earth metals in those tubes versus the more recent productions which no longer have access to those metals and the substitute for different materials, either way this is supposed to be one of the very best so I hope I don't have to buy any more tubes lol

chances are I won't be picking up your 12 pins as again I've got enough lol, but maybe I'll have some that I can sell and I might pick up some of yours as a exchange of swords


----------



## Makiah S

Maxx134 said:


> I have plenty of the 12 pin types then I will be putting up soon in the for sale threads, and I have to say the older the tube, the better sound...
> 
> so late production tubes are not as good as the oldest ones.
> C
> ...



Right and as a heads up guys don't forget to gently clean your tube contacts every so often [I do it like once a year] a tiny bit of Deoxit Red on my 6sn7's with a follow up of Gold once they've dried

Did my power tubes today and was a bit shocked how much cleaned off <.<, impressions for the 58/59 6072 Triple Mica the 5Star 6072a Black Plate and the 80s Jan 6072A Double Mica are in coming today I hope


----------



## Makiah S

Started with the 80's Jan Double Mica, and it's nice! Smooth without being too thick, tho I'm listening with an AD 2000, the real test is how does it do with HD 800


----------



## baronbeehive

Mshenay said:


> Right and as a heads up guys don't forget to gently clean your tube contacts every so often [I do it like once a year] a tiny bit of Deoxit Red on my 6sn7's with a follow up of Gold once they've dried
> 
> Did my power tubes today and was a bit shocked how much cleaned off <.<, impressions for the 58/59 6072 Triple Mica the 5Star 6072a Black Plate and the 80s Jan 6072A Double Mica are in coming today I hope



Good point! I do this once after purchasing tubes to remove years of grime but haven't touched them since. I've noticed how contacts soon get dirty.


----------



## baronbeehive

Mshenay said:


> Started with the 80's Jan Double Mica, and it's nice! Smooth without being too thick, tho I'm listening with an AD 2000, the real test is how does it do with HD 800



I'm interested to hear your comparisons with the Sylvanias.

The triple micas are supposed to be the best, I've tried the Sylvanias but settled on the Tung Sol double mica 5751's a while back. As a side note some of the opinions on the 12AX7 tube family I've heard are that they aren't as good as the 5751's, due to some deficiencies in the sound, but I must say that I don't agree with this. The Philips I've got atm I've had in for over a year now without touching them, and I don't intend to as they are the best tube I've ever heard in the APPJ. I wanted to get some of the Mullard sound but retaining detail and clarity, and the Philips certainly have this.

BTW what do you think of your Audio Technicas, I've always liked them.


----------



## Makiah S (Jun 27, 2020)

baronbeehive said:


> I'm interested to hear your comparisons with the Sylvanias.
> 
> The triple micas are supposed to be the best, I've tried the Sylvanias but settled on the Tung Sol double mica 5751's a while back. As a side note some of the opinions on the 12AX7 tube family I've heard are that they aren't as good as the 5751's, due to some deficiencies in the sound, but I must say that I don't agree with this. The Philips I've got atm I've had in for over a year now without touching them, and I don't intend to as they are the best tube I've ever heard in the APPJ. I wanted to get some of the Mullard sound but retaining detail and clarity, and the Philips certainly have this.
> 
> BTW what do you think of your Audio Technicas, I've always liked them.



I'm pretty smitten with the AD2000s I must say, and I'm not a fan of the 12AX7s either. The Triple Mica's I have are actually 12ay7s/6072[a]

An overall I find the 58/59 Triple Mica [The GE holy grail] is similar to my own White Label Sylvania in that it's airy with a very taut bass. I will need to do some more comparisons but so far I'm happy with how it sounds! I've actually been rolling these little guys into my Ember II and Auris Euterpe more than my APPJ PA1502a tonight, as these guys will function in all three amps


Sooooooooooooooooo I can say with certainty there is something special about the GE Triple Mica 58/59 6072/12ay7 

Really good timbre and tone without being too dry, that and it's got excellent clarity and staging, the GE 5 Star is also nice if you want a bit more body. When I've got some rest I'll compare the Triple Mica to my 12SL7GT


----------



## baronbeehive

Mshenay said:


> I'm pretty smitten with the AD2000s I must say, and I'm not a fan of the 12AX7s either. The Triple Mica's I have are actually 12ay7s/6072[a]
> 
> An overall I find the 58/59 Triple Mica [The GE holy grail] is similar to my own White Label Sylvania in that it's airy with a very taut bass. I will need to do some more comparisons but so far I'm happy with how it sounds! I've actually been rolling these little guys into my Ember II and Auris Euterpe more than my APPJ PA1502a tonight, as these guys will function in all three amps
> 
> ...



Excellent!

Yes, sorry I forgot you were talking about 6072A tubes.

That sounds typical GE sound, clear and airy, yes. I like them too, I used 12Ax7's in both amps for quite a while, and they were dirt cheap!

Yes, the reason I replaced my Audio Technicas a few years ago and got the HiFiMans was because they had a similar emotional type signature, but I felt the HiFiMans took this a step further.


----------



## Makiah S

baronbeehive said:


> Excellent!
> 
> Yes, sorry I forgot you were talking about 6072A tubes.
> 
> ...




Well to my ears there's a speed and quickness the AD2000 has alongside it's sweeter mid range that I like, the Hifimans even my zippppppppppy modded HE 4 didn't quite balance tone and quickness like AD 2000 does, that said HD800 is still for my tastes better it's just not always pleasent with older music where as AD2000 lacks some resolve without sounding "slow"

I did the Grill Mod on my HE 4XX and quite like'd that, anyways yea I'm happy with my choice to go GE!As they remind me of the traits I like about my late 40's Sylvania Octals

Tho I'm bummed I didn't like the GE or my Syl Octals with my Project Ember II, oh well tonight I'll have a chance to hear the GE's in my APPJ PA1502A

An tonight will settle which of my Tube's is staying in my main rig! It's Auris Euterpe VS Appj with a myriad of "Holy Grail" type tube's it should be a nice night


----------



## Maxx134

Mshenay said:


> Right and as a heads up guys don't forget to gently clean your tube contacts every so often


I used a glass fiber pen to polish my tube pins.


Got it on eBay..


----------



## baronbeehive

Mshenay said:


> tonight I'll have a chance to hear the GE's in my APPJ PA1502A



You can also get cryoed GE's from watfordvalves.com if you're interested, which I didn't get around to trying.


----------



## baronbeehive

Maxx134 said:


> I used a glass fiber pen to polish my tube pins.
> 
> Got it on eBay..


I don't know about the glass fibre pen... looks like the Oblivion chassis could do with a dust as well lol....!
.


----------



## Makiah S

baronbeehive said:


> You can also get cryoed GE's from watfordvalves.com if you're interested, which I didn't get around to trying.



Hmm I checked them out and didn't see an Cryo'd 6072 GEs


----------



## baronbeehive

Mshenay said:


> Hmm I checked them out and didn't see an Cryo'd 6072 GEs


You're right.. only 12Au7, 12At7 and 12Ax7's. The claims for them are pretty special though. I was interested to see if they lived up to the claims but never got around to it.


----------



## Maxx134

You can check out my list of tubes here


----------



## qingcai

is there any better choice for similar amp , for planar headphone.


----------



## Makiah S

qingcai said:


> is there any better choice for similar amp , for planar headphone.


Honestly I'm enjoyed my project Ember II from garage1217 for quite a while there are power supply upgrade you can purchase like the noise nuke that floats around you can also put all of the bypasses in and fully simplify the circuit which makes it very heavily colored by the choice of two and have yourself a really nice hybrid amp for planar magnetic headphones the schiit lyr three is also good as is the Cavalli hybrid from massdrop, 

As far as DIY or existing products to modify I believe there are some little dot Hybrids that people like the mod


----------



## qingcai

Mshenay said:


> Honestly I'm enjoyed my project Ember II from garage1217 for quite a while there are power supply upgrade you can purchase like the noise nuke that floats around you can also put all of the bypasses in and fully simplify the circuit which makes it very heavily colored by the choice of two and have yourself a really nice hybrid amp for planar magnetic headphones the schiit lyr three is also good as is the Cavalli hybrid from massdrop,
> 
> As far as DIY or existing products to modify I believe there are some little dot Hybrids that people like the mod


thanks, I will check it out. 
I own a darvoice, it does sound good to my ears. so that bring my interest of tube amp.


----------



## qingcai

this is 2nd time I saw people mentioned about ember ii. 
thanks.


----------



## qingcai

Mortus said:


> hello
> 
> I am searching any opinion about this: Gemtune APPJ PA1502A  tube amp ,probably it is based on Miniwatt N3  APPJ PA0901A speaker amp
> and if so miniwatt has good review ,has anybody hear of it ? is it worth any attention ?
> ...


very curious about the output transformer. some people mod the "capacitors" , are these capacitors output capacitors ?


----------



## Maxx134

qingcai said:


> very curious about the output transformer. some people mod the "capacitors" , are these capacitors output capacitors ?


Transformers I can't say.
Capacitors changed are not output. The ones mentioned in thread to be changed are the "coupling caps". They "couple" the driver stage (that middle tube) to the output stage (two bigger tubes which are connected to the transformers for output).


----------



## qingcai

Maxx134 said:


> Transformers I can't say.
> Capacitors changed are not output. The ones mentioned in thread to be changed are the "coupling caps". They "couple" the driver stage (that middle tube) to the output stage (two bigger tubes which are connected to the transformers for output).


thanks for the reply, I just read from the begining, and I got my appj today.


----------



## qingcai

my changes. 0.1uf + 1500uf for bypass.  0.47+0.1 for coupling.


----------



## CJG888 (Oct 27, 2021)

baronbeehive said:


> This is my PCB, very similar to yours, very neat and tidy inside:
> 
> 
> 
> ...


Sorry to dredge up a really old thread, but I am in the process of recommissioning my old PA0901A. So far, it sounds good on the end of a WBA tube preamp, driving my home-designed and built Tangband full-range desktop monitors. I’m using NOS Philips “foreign” EL84s and an EI ECC83 (made on an old Philips production line). A JJ ECC83S is incoming for comparison purposes.

Now to the issue of capacitors: are the polar AN Kaiseis the correct ones for the cathode? I presume they should be… As for the coupling caps, I have a bunch of NOS RCL 0.22uF PIOs and also a selection of 0.22uF Mullard “mustard” foil caps in my “box of bits”. All are rated at 400V. Would you recommend using either of them? I don’t really want to go all out for the Jupiters yet.

Presumably I can just connect a pair in parallel to get to 0.44uF.


----------



## CJG888 (Oct 29, 2021)

OK, I have a plan. The nasty steel feet have come off, to be replaced with three RDC cones, attached to the bottom plate. The Audio Note Kaiseis are on their way over from the UK, and will be bypassed with 0.10uF ICW polypropylene caps which I still have from the 1990s (NOS). Coupling caps will be a pair of NOS vintage RCL 0.22uF PIOs.


----------



## Maxx134

Nice. PIO caps have good natural sound.


----------



## baronbeehive (Nov 1, 2021)

CJG888 said:


> Sorry to dredge up a really old thread, but I am in the process of recommissioning my old PA0901A. So far, it sounds good on the end of a WBA tube preamp, driving my home-designed and built Tangband full-range desktop monitors. I’m using NOS Philips “foreign” EL84s and an EI ECC83 (made on an old Philips production line). A JJ ECC83S is incoming for comparison purposes.
> 
> Now to the issue of capacitors: are the polar AN Kaiseis the correct ones for the cathode? I presume they should be… As for the coupling caps, I have a bunch of NOS RCL 0.22uF PIOs and also a selection of 0.22uF Mullard “mustard” foil caps in my “box of bits”. All are rated at 400V. Would you recommend using either of them? I don’t really want to go all out for the Jupiters yet.
> 
> Presumably I can just connect a pair in parallel to get to 0.44uF.


Hi there, it is a very old thread by now! Yes all good. What rated Kaiseis are you using? I think the amp needs 1000uF or at least quite a high rating to complement the sound and power output otherwise it will probably be a bit too treble centric. That's what I have in mine together with the .1uF bypasses.

You might need to extend the bottom of the chassis, if so go back to around page 19 and 28 or so to see.

What sensitivity are your monitors?

Be careful soldering to the PCB pads they come off quite easily.


----------



## CJG888




----------



## CJG888

OK, the AN caps haven’t arrived yet (Brexit!).

I’ve fitted the vintage PIOs, and the sound is already much more transparent and open.

Those woolly pads are IKEA cabinet feet, to keep the capacitor leads away from the casework! The central standoff has been insulated with heatshrink.

Will the cathode caps not fit inside the case?


----------



## baronbeehive

CJG888 said:


> OK, the AN caps haven’t arrived yet (Brexit!).


Haha, I know the problem, it's the same here!


CJG888 said:


> OK, the AN caps haven’t arrived yet (Brexit!).
> 
> I’ve fitted the vintage PIOs, and the *sound is already much more transparent and open*.
> 
> ...


Great to hear!

I don't know, if they are 1000uF, 16v ones then they are 26mm, as mine were 25v I can't say definitely they seem to have changed the range of caps at Audio Note. So you will have to measure. If they don't fit upright then you will have to put them in sideways like your coupling caps.


----------



## CJG888 (Nov 11, 2021)

In went the Kaiseis today. They are a tight fit, but can be installed in the positions of the stock caps.

Unfortunately, none of the coupling caps which I have to hand could be made to fit (those NOS PIOs are huge), so I have left them out for now. If required, maybe a pair of Solens can be made to fit on top of the board…

As it is, treble doesn’t seem to be missing, though. I’ll wait and see how the caps burn in.

After several hours of running-in, I can say that bass extension and dynamics have improved dramatically.


----------



## CJG888

I’m also using a JJ ECC83S on the input, for maximum “bite”. This tube is closer to the E803CC of old…


----------



## AudioCats

I am late to the party.

I recently got a used PA1502A, and took it apart for some cleaning and refurbishing. The build quality is very good, and APPJ don't cut corner in the design phase, everything seems to be well thought out, there is a large heatsink for the power supply control chip (TOP250YN), a large sheet metal shield over the switching power supply section, there is even a large silicon thermal pad to transfer the heat from the PCB to the metal shield.  Comparing to my Little Bear P8, which is at about the same price, this APPJ is super well made. (Little Bear P8 ==> so so build quality, sub-standard design)

Tube rolling so far (configuration = 0.44uf FT3 as interstage coupling caps; volume control changed to shunt-pot type, with 22k AudioNote as input resistor; 6F6 as output tubes; gain switch=H): 
I have tried 12ax7 and 12au7, both are amperax bulgleboy measured as "new".  I much prefer the 12ax7, much cleaner and fuller sound. 
with 12au7 installed there is more hum, and the sound is "harder", not as rich. The plate voltage is at just 55v (125v with 12ax7 installed). To properly use the 12au7, I think the cathode resistor value needs to be adjusted to get proper plate voltage. I am happy with the 12ax7 so I am not gonna mess with that. 

coupling capacitors: so far I have tried FT3 (aluminum/teflon) and K40Y9 (paper in oil). The K40Y9 has a more "simplified" sound but is smoother and more easy-listening. I will try some other caps later (Dynamic, Vitamin-Q, AudioCap Theta etc).

(minor) complains about the PA1502A:
-- volume pot is tiny, there is obvious channel imbalance at low volume. This is not a real problem with my current phones (Forstex T50rp), the full listening volume happens with volume pot at around 12 o'clock anyway.
-- there is a low hum, audiable when music is not playing.  The filament supply is DC so I was surprised to hear this hum. It doesn't sound like the typical 60hz. I will investigate this further.


----------



## AudioCats

pvico said:


> For those interested, here is the schematic of the amplifier.
> https://www.dropbox.com/s/ggm7a0la2era3n3/PA1502A APPJ Schematic.png?dl=0
> Here is the LtSpice simulation package:
> https://www.dropbox.com/s/rk5oukakn2bzwzg/PA1502A APPJ.zip?dl=0
> ...



thank you very much for your great work, much appreciated. It makes tinkering with this little amp much more fun.


----------



## AudioCats (Feb 13, 2022)

back ground noise / hum:
the hum is audiable with my T50rp, but it is very obvious with my 32 ohm Beyer 770. The waveform taken at the phone jack is not what I have expected,
(measured with T50rp plugged into the jack)
peak-to-peak amplitude is ~500mV, the space between spikes is about 16uS, so ~65kHz. The power supply IC, TOP250YN runs at 132kHz, these spikes are likely from the switcher. it looks like the noise from the switching power supply has gotten into the signal path. The "hum" I am hearing might be some kind of beat frequency.






The HV rail looks relativly clean but does have these spikes. Scope capture shows 1.2v peak-to-peak in AC-couple mode, but 8Vp-p in DC-couple mode.




Filament supply has these spikes too, ~1.5Vp-p




Filament supply circuit: D3 is the rectifier (gets hot when running the amp), C04 (1500uf/16v) is the first filtering cap, current goes through L04 (3.3uH) to the 2nd filtering cap C05 (1500uf/16v). I changed L04 to 700uH, the spikes went down to 0.7Vp-p. The hum is a little quieter but still annoying when using 32 ohm Beyerdynamic.
increasing C05 capacitance did not make much improvement either.

I will try using a separate supply to provide the filament voltage, maybe that can help getting rid of the hum. Not sure if this will affect the HV rail though, (the feedback for TOP250YN is taken from the 12v rail before L04).

update:
I could not make the spikes go way with what I have in my parts box. The largest coil I have tried is 1.5mH and the spikes at the output jack went down to around 300mVpp, the hum was still there and sounded more or less the same.
At this point I am convinced that while the spikes are real, it is outside of my hearing range, the hum I am hearing is probably something picked up by the long lead wires I am using in the signal-cap test rig.

update:
I connected a DC supply to provide the 12v filament voltage, now the switching supply on the board only has to provide HV voltage ==> 174v DC, with 6Vpp spikes; power consumption of the amp is 11w/22va; (correction but hum is still there. 

Different HV reservoir caps have noticeable effect in this amp, I tried ASC polyprop vs Nichicon KZ electrolytics (three 100v KZ in series), the KZ yields more solid impact while the sound with polyprop is more spacious with richer bass details. I much prefer the polyprop.


----------



## baronbeehive (Feb 6, 2022)

Hi AudioCats, just noticed a new member here after all this time!

Just reply to a couple of points, nobody else has mentioned a hum so I wonder if it is something to do with your amp or connections? As you say the SMPS does exhibit noise but usually outside the range of human hearing unless your hearing or headphone is ultra sensitive. And the metal shield should do the job of stopping PSU noise entering the audio signal. I must admit I was initially concerned about the SMPS after hearing horror stories about them spontaneously combusting but after many years of use, and some modding, it has remained good.. touch wood!

Re: cathode bypass caps I have the Nichicon KZ's in my other amp and love them but for the APPJ I have the Audio Note Kaisei's which do an excellent job of rounding out the sound to a pleasing weight and resolution. What capacitance have you installed here? I'm not really qualified to comment on the headphone APPJ you have as mine is the speaker version but with a low power output the higher the better for power handling, mine are 1000uF with excellent results.

You mention 12Au7, I recently tried a 12AT7 Brimar from Footscray factory, and I was very surprised when it turned out to better my Philips Herleen factory tube because it is much lower gain, so it is now permanently installed in the amp. The SQ from the amp now matches my other highly modded amp which is a Little Dot MKVI+. Not bad for a lowly $150 amp!


----------



## AudioCats

yeah, the hum I am hearing is likely (mostly) from my capacitor test rig (long wires connecting to header blocks, allowing fast coupling capacitor change without soldering). 

I haven't tried different cathode bypass caps yet. The voltage at 6v6 cathode measured around 12v, I will try some 1000uf/25v BG-std and see what happens.


----------



## baronbeehive

If you do try those 1000uF's you will need to parallel some smaller bypasses to help with the higher frequencies. Without them the high capacitance will help with power handling but will adversely affect the sound producing a rather heavy sound.

There is a very  handy calculator for finding the best cathode bypass capacitance here: https://www.ampbooks.com/mobile/amplifier-calculators/cathode-capacitor/calculator/
It may be that 1000uF is overkill if you look at the calculator but it should certainly benefit power handling anyway and has no adverse effects such as oscillations.


----------



## AudioCats (Feb 8, 2022)

baronbeehive said:


> ...
> I must admit I was initially concerned about the SMPS after hearing horror stories about them spontaneously combusting but after many years of use, and some modding, it has remained good.. touch wood!
> 
> ...


I think appj people put a lot of thoughts into the design, I don't worry about heat problem in this little amp. It was not super warm when I was running it in full stock condition, though only for about an hour.
I did measure power supply component temps before mods. The hottest part was D3 (rectifier diode for filament supply, doing about 1A), it reached 65C after a few hours (with the amp rested on the side with bottom plate removed). I suppose it can get to 80~85c during normal operation. C04 is next to it so can see some rather warm temperature, and APPJ chose a 1500uf/16v Rubycon that is rated to 130C (!). I was impressed when I saw that.


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## baronbeehive

AudioCats said:


> I think appj people put a lot of thoughts into the design, I don't worry about heat problem in this little amp. It was not super warm when I was running it in full stock condition, though only for about an hour.
> I did measure power supply component temps before mods. The hottest part was D3 (rectifier diode for filament supply, doing about 1A), it reached 65C after a few hours (with the amp rested on the side with bottom plate removed). I suppose it can get to 80~85c during normal operation. C04 is next to it so can see some rather warm temperature, and APPJ chose a 1500uf/16v Rubycon that is rated to 130C (!). I was impressed when I saw that.


Right! Good information, I didn't get round to looking at the schematic, so didn't know that about the 130C component, I'm pretty impressed with that too. I did make my own rudimentary schematic with the connections for the purposes of the alterations.

You're right the amp doesn't run hot so I've never had any worries.


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## AudioCats (Feb 11, 2022)

Partial schematic of PA1502a's power supply. I didn't bother to trace anything related to the power control IC (TOP250YN) since I don't plan to make any change there.





Q1 (4N60, 4A/600v rated) and C06 form a capacitance multiplier.
The TOP chip monitors the filament line voltage, IC2 is the opto-isolator to relay feedback back to the TOP chip.  HV/B+ line is unregulated.


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## AudioCats

result of my 6v6 cathode caps experiments: 
(shunt-pot input resistor=audioNote; interstage coupling=FT3 teflon; phones= 32ohm Beyer)
a) ASC 20uf polyprop: boomier bass than stock, hollower sounding; has low frequency "motor boating" oscillation.
b) 1000uf/25v BG-std: solid bass, with rich bass details. a bit cleaner sound than stock. Bass impact might be a little too hard/overwhelming. 
c) Nichicon ES (green) bipolar 220uf/50v, long lead to + side: bass between BG-std and stock; cleaner sound than stock; overly warm, a bit rounded-off? 

stock cap has softer boomier bass than BG-std, more lay back, duller sound with less focus.

The differences are not night and day.   Nichicon ES is good enough, and it is the same size as stock, fits perfectly.

(I wanted to try Kaisei but the values I want are out of stock at partsconnexion.)


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## baronbeehive (Feb 16, 2022)

Yes, this amp as stock is very good as is but is really needing some basic mods such as we are doing here to bring out the best, which is endgame AFAIK.

That cathode bypass calculator I linked to is very interesting, I haven't tried it with this amp because I didn't know some of the inputs. But, for example the frequency curve for a 1000uF cap shows suspected overkill but, as there is no oscillation in the APPJ, I have stuck with it because of the excellent sound and power handling. In the cathode bypass calculator example above there was no difference in the frequency curve for a 500uF or 1000uF cap hence suspected overkill.

I tried initially with 1000uF in this amp and found as suspected that the sound was heavy, dull and the higher frequency sparkle were lost. As soon as I installed the smaller Audyn True Copper caps as bypasses the sound became very lively again. Without that I suspect that something around 500uF might suffice on its own.

I haven't found the bass overpowering or boomy at all on the contrary it is sharp, detailed and in proportion to the rest of the frequency band. The treble also is extended and I find the whole SQ really excellent. Of course it all depends on the quality of parts installed. The Kaiseis were the first I tried and I think they complement the sound very well by making it sound fuller and detailed yet still warm sounding. I tried Nichicons in my other amp but not the ones you used.

Also as I had one spare Jupiter copper foil, paper and wax cap from my last mods I got another to put into the APPJ for coupling, so again top quality parts. OK so I ended up doubling the cost of the amp but at around $150 for the stock amp it is an incredible bargain IMO.

Edit: try to get a non polar cathode bypass cap if you can, better for constant power flow and hence sound.


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## AudioCats (Feb 16, 2022)

*shunt-pot input resistor *experiments:
(bugle-boy12ax7; 6f6s; 0.44uf FT3 as interstage; 220uf Nichicon ES as cathode bypass; 32 ohm beyer driver)

--AudioNote, non-magnetic: fine, sweet and clean; has some bite; not overly "cheerful"
--Vishay VAR: warm and slurry, bass too thick
--Caddock TF020: bass bottoms out?
--shinkoh: soft and pleasant; some boominess in bass; no bite
-- riken: clear top, more bite than AN, emotion about the same as AN but not as much fine details?

Riken's detail level is about the same as shinkoh.
AN's detail level is about the same as VAR and TF020 (and one notch above Riken and Shinkoh)

==> start with AN; if want darker use Shinkoh, if want brighter use riken.

In my other stuff, especially the electrostatics, I usually prefer TF020 or VAR, the AN has always been a bit too "sweet and cheerful". But in this amp AN is the winner.


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## baronbeehive

AudioCats said:


> *shunt-pot input resistor *experiments:
> (bugle-boy12ax7; 6f6s; 0.44uf FT3 as interstage; 220uf Nichicon ES as cathode bypass; 32 ohm beyer driver)
> 
> --AudioNote, non-magnetic: fine, sweet and clean; has some bite; not overly "cheerful"
> ...


Don't know if you are interested but someone on another thread has very recently done a test of several resistor types I will quote here just in case: 

_"the AN Niobium ... very good clarity and detail over the FR, a very refined, detailed and smooth high end kind of sound... Afterwards I still tried the AN tantalums, but they were clearly worse than the niobiums with soft bass and muddied low treble. So as they now worked in my system I'd rank them as follows: First, Audio Note Niobium non-magnetic - these are worth their price here and they are in a different league to the rest. Second, the Kiwames - they have good punchy and deep bass and are relatively cheap too even if they don't have the very best clarity. Third, the AN tantalums which had many things in common with the Kiwames but were worse. Fourth the TKD metal films which have a crisp character but are low on bass. Fifth and last the Ohmite Audio Golds which didn't really stand out with their characteristics."_


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## AudioCats

AN Niobium, interesting  ... Partsconnexion doesn't carry them. I might try to find some one of these days.

I do not agree with  Kiwame being better than AN tantalum (as series resistor in shunt-pots). Not even close.

in the PA1502A, I think the shinkoh is good enough, AN is kind of an over-kill.


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## AudioCats (Feb 23, 2022)

test result of *using a separated power supply for filament* (the on-bard supply only does HV/B+)

I was hoping to solve the hum problem by using a dedicated filament supply, but it *did not work*. There was audio frequency noise in the HV line, some kind of oscillation maybe, (not just the 63khz sharp spikes). It seems that the onboard power IC is expecting the 12V line to have some kind of load, when the current draw goes up the hum/noise frequency increases, and wise-versa. The oscillation was around 10hz when the load resistor was 68 ohms (around 180mA draw). At 0mA draw it became some kind of motor-boating noise. 
The "sweet spot" (relatively speaking) happened when the load resistor was 12 ohms (1A draw), but the hum was still noticeable.


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## baronbeehive (Feb 23, 2022)

Not heard of this before, sounds like you've got a faulty unit. Could be a faulty SMPS.

I've had mine for years with no problems.

Edit: Have you tried changing the tubes, one might be faulty?


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## AudioCats

sorry, I probably need to clarify: the problem happened when using a separate power supply for the 12v filament power. 
The amp works fine in original configuration (but has hum when using sensitive headphones).


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## baronbeehive (Feb 24, 2022)

AudioCats said:


> sorry, I probably need to clarify: the problem happened when using a separate power supply for the 12v filament power.
> The amp works fine in original configuration (but has hum when using sensitive headphones).


OK, great! I can't comment as mine is the speaker version, don't know what headphones others have here.


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