# Civilian 6n2+fu32 tube headphone amp



## DavidK35

Bought this amplfier (110v version) recently from a Singapore reseller. Arrived in under 10 days in perfect condition. Prompt service & answer emails but no tracking.Total cost including shipping, paypal, $226.00. One of the chinese fu32 tubes failed after one session, but no loss as always replace the chinese stock with NOS anyway.
  Biffed out all the chinese tubes & replaced with NOS. I love the 1940's tubes & after researching found that the 832A is a direct replacement for the fu32. These are way cheap & plentiful to buy & knock the socks off any later 9 pin miniature set ups (IMO), that I have tried. Same cannot be said for the 6AX7 (replacement for the 6N2) which is very hard to find but not expensive. There are a couple of options however.
  For now I have gone the route of using 6AT7 instead of 6AX7 with the 60mu instead of 100 with no detrimental effect or volume change. The initial tube to replace the chinese is a canadian Rogers 6AX7 NOS & was a big improvement, however after putting in a euro NOS 6AT7 the sound has improved again. The main tubes are RCA 832A NOS, not only do they sound great but look really funky too. The other option would be to rewire to suit the 12AX/AT7 types, a simple fix for those handy with a soldering iron.
   
  The specs say 32-600 ohms headphones & 1W but do not say what it is @ the different impedences. For now using the low impedence AKG241 headphones. At 12 o'clock position it is plenty loud. Plan to buy some Fostex TR50 ortho's in the near future, as I think this amp has the oomph to do them justice. The AKG241's have never sounded better & have more base & cleaner highs than in previous amps.
  For a total of $250 this is an amazing bargain IMO. It does run hot so needs plenty of space, but would not recommend it for desktop/speaker set up due to the heat issues. No safety frame comes with this. A switch at the back allows speaker or headphone use. The manual is one sheet of paper in chinese so your on your own there. I do not know all the appropriate words for describing the sound but sounds great to my ears. Good firm base, rich mids & smooth highs & great detail throughout.
   
  From the sales blurb they probably had high impedence phones in mind but list from 32ohms up, so took a chance but so far has worked out great.
   
  From the seller (translated):
   
  [size=24.0px]The real price of civilians 6n2 + fu32 fever headphone amplifier[/size]
[size=24.0px]Finished with a floor machine[/size]​ [size=24.0px]All hand welded scaffolding[/size]​  ​ [size=24.0px]6n2 + FU32 Sakunami tube single-ended output 4w +4 w, amp output 1w,[/size]​ [size=24.0px]And all of my products, comments, suggestions, criticisms, is my greatest support and encouragement, I have to create the world's most cattle Mic ---- cheap good sound, so that more people enjoy the fun of this part on the ear feel good to hear the sound through, improve quality of life for the ears.[/size]  [size=24.0px]Tube amp can not get rid of desire and mysterious, expensive veil.[/size]​ [size=24.0px]Pure tube amplification and power amplification CPI-end amp choice![/size]  [size=24.0px]Contrast RP030 million class amp standard (not a tube amp gallstones can compare).[/size]  [size=24.0px]First used in particular to promote the headphone output transformer, protecting you against hundreds of thousands of dollars of damage to high-end headphones, the real price close to the people for only 568 yuan a table,[/size]​ [size=24.0px]We listen using Sennheiser Sennheiser HD800 flagship dynamic headphones[/size]​ [size=24.0px]Optional power supply 110v 220v to 110v please and after explaining our shoot, normal delivery is 220v[/size]​  ​   
[size=18.0px][size=large][size=24.0px][size=12.0pt]Power cord[/size] [size=12.0pt]Signal cable supplied (that is on the computer's power cord) due to safety issues related to the preparation of your own, do not provide the finished machine[/size][/size][/size][/size]​ [size=12.0pt][size=18.0px][size=large][size=24.0px]Sennheiser HD600 HD650 HD700 HD800 series headphones perfect match[/size][/size][/size][/size]​   

[size=12.0pt][size=18.0px][size=large][size=24.0px]Product Features[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px]A push by Beijing 6n2 tubes and Beijing fu32 Class A vacuum tube amplifier circuit in parallel, using the output transformer output[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px]2 core output transformer using Z11 0.35MM 66 * 32 wafers using special processes around the system, power supply using H 14 360[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px]0.5 annealed wafers[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px]3 along the line audio input, perfect headphones protection circuit, output transformer no-load protection[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px]Four former senior designer fever seniors (old driving New) provide a prototype circuit, and then have experienced fever seniors (gall Arts Presbyterian)[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px]Improved circuit, put on a prototype, which took six months of selecting components for adjusting the sound improved, setting production sale, bulk[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px]Production strictly in accordance with the sound when adjusting component assembly[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px]5 goals headphones and listen to the sound description[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px]6 Listen with headphones as: flagship Sennheiser HD800 headphones with the machine and Italy RP030 Professional[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px]Headphone Amplifier contrast audition[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px]7 sound described as: 6n2 + fu32 two headphone amplifiers for a fever, in the audio band with excellent performance, high-quality ear[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px]Player, the overall balance of low and medium frequency, with the CPI tube characteristics, the full sense of low volume and intensity, IF warm alcohol[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px]Thick, high-frequency has special advantages, the entire frequency layer[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px]Times clear, with great accuracy, but did not split at very high frequency sound detail, stretch and bright high-frequency[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px]Be controlled very well![/size][/size][/size][/size] [size=12.0pt][size=18.0px][size=large][size=24.0px]This paragraph sound performance overall service, praised the high cost can be put headphone amp[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px]Generosity[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px]Product Features[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px]Sources may use audio CD player and a computer (PC with a sound card line-out port on the need)[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px]A use of all AC filament lighting, with 102DB headphones listen, hear a little hum noise, feel, and do not[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px]Like the static power[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px]1 uses 6n2 driven fu32 parallel CPI amplifier circuit, power amplifier output 4w +4 w push speakers with impedance requirements[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px](4 - 8) ohm two-way speaker, sensitivity 90db above 6.5 inch, headphones 32-600 Europe (1w or so)[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px]3 volume potentiometer type used in Japan ALPS 16 potentiometer, ensure clear positioning and left-right balance[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px]4 with accuracy up to 1% metal film resistors and import electrolytic capacitor. Coupling using imported oil capacitors[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px]5 uses 0.8mm brushed stainless steel surface with wooden chassis,[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px]Performance Specifications:[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px]The machine output characteristics, 4 ohm output port directly, 8 ohm output and a headphone jack switch[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px]1, the product full name: 6n2 + fu32 amplifier + amp vacuum tube amplifier with two machine[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px]2, Color: brushed stainless steel surface qualities[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px]3, Weight: 6kg about Taping Dimensions 40 * 35 * 25cm[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px]4, Product Size: Size 32 * 18 * 16cm height with tube[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px]Parameters Table[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px]· Input: one RCA input[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px]· Output: behind the amplifier output impedance of 4 ohms Interface 8 ohms two set of interfaces 4w +4 w[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px]Front 6.35mm standard headphone output hole 32-600 Europe[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px]· Frequency response :26-38KHz ± 2db[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px]Output SNR:> 118dB "A" - wtd[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px]Output total harmonic distortion: <0.008% 10Hz to 20kHz[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px]· Amp maximum output peak: (1w left) (corresponding to the power please correspond headphone impedance calculation)[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px]To provide this special thanks to the local senior prototype circuit fever predecessors (old driving New)[/size][/size][/size][/size]
[size=12.0pt][size=18.0px][size=large][size=24.0px]Quality Warranty tube package with two months, the whole year of free maintenance, warranty, all within the freight buyer[/size][/size][/size][/size]
  ...................
   
  From another supplier:
   
  [size=x-small]*TUBE amplifier is not like other transistor and digital amplifier.it's 4W*2,but it's support 20-100W speaker,no problem.*[/size]
*[size=x-small]about Headphoe 6.35 JACK output:1W,perfact for 32-600ohm hadphone.free give one 6.35 to 3.5 converter,then you can connect it to all headphone[/size]*


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## TrollDragon

I was pondering that amp before I bought my Little Dot, I liked the look of tubes in it. Then I ran across a page with different tubes and the same amp for less than $150 so I took a pass on the Chinese one.

I'll try to find that page again if you want it.

Sent from my HTC Desire HD A9191 using Tapatalk 2


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## DavidK35

I think I know the one you mean, but does not have the headphone output, or the funky 40's tubes
   
  This one?


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## jhin

i just ordered one of this amp.
  also i ordered  some NOS GU23 to replace the  chinese FU32 and a NOS 6N2P-EV to replace the 6N2
  Thanks to your info i also ordered one NOS 6AT7.


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## DavidK35

Great, let us know what you think of this amp, but give it time to show it's full potential. A minimum of 1 but 2 weeks burn in is better. These larger tubes
  definitely take longer to burn in than the miniatures. Enjoy.


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## TrollDragon

Quote: 





davidk35 said:


> I think I know the one you mean, but does not have the headphone output, or the funky 40's tubes
> 
> This one?


 
  Yeah that was the one, I saw it on the SiliconRay site.
  Your right no HP Out, I totally missed that.
   
  Those fu32 look just too cool but the RCA's look even better and probably last longer as well.


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## jhin

i received the amp today.
bad news, it came with one broken FU32 tube and seller refuse to send me a new tube but they just want to partial refund of $5
DONT BUY FROM 85China.

not good enough.

so i just order a set of GU32

i open it up and one of the big filter capacitor came off the mounting and it was just loose inside.BAD

so i remount it and i made an aluminium clamp to secure it in place so it does not come off in the future.

will post photo later.

can not test it.. will be waiting for the replace ment tube GU32

NOW

a couple of questions

- when im using a headphone, does the amp need to be connected to a pair of speakers while using the headphone? can i use headphone without connecting it to a speakers?
- the switch at the back, what is the position of it when listenning to a headphone and speakers?
- what is the best tube to replace the chinese 6n2?

This the photo of the capacitor after I install an aluminium clamp


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## Jonnville

Any updates on your impressions of this amp?  I have one on the way too.  Plans are to swap the tubes for NOS and put it in a decent looking chassis.
   
  Regards
   
  Jon'.


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## DavidK35

You do not need to connect speakers.
  Yes you can use just headphones.
  Headphone position is up.
  IMO the best replacement is US/Euro NOS. 6AX7 & 6AT7N I have used both & are fine, the 6AT7N is my preferred option & does not really affect the output volume.
   
  For pure cosmetics I am going to replace the volume knob, to match other gear.


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## DavidK35

Just noticed in my original thread starter post, the "other option" to rewire to suit 12AX/AT7 is regarding the 6N2/6AX7 tube not the main tubes.
   
  Wiring diagram: http://www.triodeel.com/images/rb6n2pcv.gif


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## Jonnville

Am I right in thinking that the 6AT7N is interchangeable with the 6DT8?
   
  Regards
   
  Jon'.


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## jhin

davidk35 said:


> You do not need to connect speakers.
> Yes you can use just headphones.
> Headphone position is up.
> IMO the best replacement is US/Euro NOS. 6AX7



thanks for the info

im just waiting for the new tubes
i just made a new side panels for it. the ones the came with it is just to ugly ( pine wood with red stain).












I know it will not improve the sound quality, buy I just looks better 



i will also replace the volume knob. i have a lathe, i might machine an aluminium or wood.


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## DavidK35

Quote: 





jonnville said:


> Am I right in thinking that the 6AT7N is interchangeable with the 6DT8?
> 
> Regards
> 
> Jon'.


 

 Yes that is right, if you do use that tube let me know what you think of it.


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## DavidK35

Quote: 





jhin said:


> thanks for the info
> 
> im just waiting for the new tubes
> i just made a new side panels for it. the ones the came with it is just to ugly ( pine wood with red stain).
> ...


 

 Very nice panels, when you have all the mods completed post more pics.


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## jhin

Here is the photos of the finish modded Civilian 6n2+fu32 tube headphone amp.
  I made a wooden front panel.
  I replace the original switch with a rotary switch to match the volume knob.
  I also added a green LED on top of the headphone jack ( its not connected yet )
   
  The back stay the same.
   
  I still dont have the replacement tube..=(


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## TrollDragon

Very nice work.

I'd replace the headphone jack with a black 1/4" panel jack, like the locking Neutrik ones.

 www.neutrik.com/en/audio/plugs-and-jacks/locking-1/4-chassis-jacks/nj3fp6c-b

Would match those excellent knobs, just sayin.  

Sent from my HTC Desire HD A9191 using Tapatalk 2


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## jhin

Quote: 





trolldragon said:


> Very nice work.
> 
> I'd replace the headphone jack with a black 1/4" panel jack, like the locking Neutrik ones.
> 
> ...


 
  ummmm.. that neutrik headphone jack is nice...might consider that.


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## MDR30

Let us know what it sounds like when you've received the tubes.

I would stay away from locking jacks for one important reason: should you, your wife, friends or children trip on the cord, the whole thing could crash. And it's akward always having to use two hands swapping headphones. I know, I have an amp with those jacks and I tend to use it less than the others because of that.

I'm sure Neutrik and other manufacturers have regular jacks that looks good as well. It' a kind of safety release.

Nice work, by the way!


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## Jonnville

Mine's arrived and although I haven't had a chance to listen to it yet, the build quality looks very good - a very pleasant surprise and far better than I expected. 
   
  I have some NOS RCA 832As and a 6DT8 in transit too - really looking forward to playing around with this great little amp.
   
  Regards.
   
  Jon'.


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## DavidK35

Been burning in my new Fostex T50RP ortho headphones with this amp & it seems to be a match made in heaven. This amp has plenty of power to drive these low impedence headphones, effortlessly. A 12o'clock setting is the max you need with these headphones & blows the AKG's away. No more very annoying sibilance, a ton of bass, excellent mids & a slightly rolled off treble which to me is perfectly balanced. Especially good for modern rock/pop recordings that all have way too much treble to start with. One ends up just listening to the music for long sessions as the balance is just right. Anyone who thinks these headphones do not have enough bass are using the wrong amp, no modifications necessary IMO, just partner them with the right amp, like this one. For $350 approx for amp + NOS + h/phones, this has to be one of the most outstanding bargains in head-fi.


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## DavidK35

Does anyone know what/where to purchase a rotary on/off switch to replace the existing power switch? Needs to have a 6mm shaft so I can match the new volume knob I installed. TIA.


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## Haidar

Any more impressions of how this sounds?


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## Maniac

I also got one just for kicks, since it is really not expensive...

 As is unmodified, it is a bit on the clouded/muddy sort of sound, not very clear/sharp.  It does have good punch, but it really need to work on the detail side of things.
  
 I've so far modded the input tube to take 12AX7 instead of 6N2P (I don't plan to tube roll through all of Russia/Eastern Bloc have to offer, so 12AX7 it is), and swapped the Chinese FU-32 for a pair of RCA 832A.  One interesting thing I found between the Chinese FU-32 and RCA 832A is that RCA's plate is like what you'd expect, uniform color, no scratch or other marks.  While the plate on Chinese FU-32 was really scratched up, not that it scratched through the plate coating, but it was quite visible.
  
  
 Other than the tube swap, I've also replaced the pair of coupling cap in between input and power tube.  These cap is interested, as it uses ceramic housing, instead of the normal epoxy dip/plastic wrap.  Perhaps it was some kind of surplus high voltage cap re-purposed as audio coupling.  Since I have no idea how these if those cap are good or not, I swapped them for a pair of Bennic FPP 0.33uF/400V caps (It was 0.1uF, unknown voltage).
  
 the amp is just back in one piece about 30 minutes ago, and I'm letting it warm up before listening to it seriously.  By warming up, that include the irons on this amp, as they tend to get pretty warm after a while.  Which does take a while. 
  
  
  
 Seriously, these tubes really light up pretty, especially if you dim the room a bit.  That alone might be enough for quite a few people to get them.


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## Maniac

Follow up on the previous post, the amp with the following modification:
 Tube:
 Chinese Beijing FU-32 -> RCA 832A
 Chinese Beijing 6N2 -> JJ 12AX7 (including Filament connection mod on the amp)

 Cap:
 Replace the unmarked ceramic 0.1uF cap with Bennic 0.33/400V FPP cap
  
 A bit of tidying up of the connections, such as the cap is now wired directly across the input and power tube, instead of going back to the bus, routed round and round and then to the power tube.


 After about 16 hours of continuous operation, the thing cleared up quite a bit, it is much better than what it was without modification.   I will swap in the Chinese FU-32 tube in a moment and see how much difference did that tube make.
  
 ====Edit====

 Swapped the original FU-32 for about an hour, and couldn't stand the muddy sound.  Swapped back RCA 832A, and it already sounds better within a minute of powering up.


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## Argybargy

FYI Neutrik locking jacks clamp hard on Viablue plugs, very very hard to remove. As stated previously I would avoid locking jacks.


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## TrollDragon

argybargy said:


> FYI Neutrik locking jacks clamp hard on Viablue plugs, very very hard to remove. As stated previously I would avoid locking jacks.


 

 Or just remove the locking bit's... 
	

	
	
		
		

		
		
	


	



 http://www.head-fi.org/t/86990/guide-to-modifying-a-neutrik-locking-jack#post_1002790


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## Argybargy

Thanks, didn't see that thread. I'll give it a try. I have 2 of those buggers in my parts bin.


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## Maniac

You can get one of those non-locking Neutrik sockets that is the same shape as the one in there, which will allow you to swap it in without any additional metal work.


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## Pyralix

Just received mine after waiting awhile. around $200 shipped from http://cart100.com/Product/23718020085/Fever_6n2_fu32_tube_amp_vacuum_tube_head/ca.
  
 One of the FU32s didn't work out of the box. Replaced the tubes with NOS tung-sol 6ax7 and haltron 832As, sounds very nice!
  
 Thanks for the review DavidK35.


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## DavidK35

Glad you like it, enjoying mine also, best value around for a modest $200 or so, very undervalued. Replaced the volume knob with a big
 solid shiny bronze one, looks retro cool to me.


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## Shaffer

How does the sound quality compare to some of the other amps around? What would you guys say it's similar to, or not?


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## DavidK35

Full rounded sound with sweet treble, makes my AKG's sing. Had to give up on the Fostex phones they developed a fault & the supplier failed to fix the problem. Would like to try Sennhesers when funds permit.


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## Redcarmoose

http://www.ebay.co.uk/itm/HiFi-6N2-FU32-pure-Class-A-Tube-valve-amplifier-4W-x2-Headphone-amp-110-240V/291100069277?_trksid=p2047675.c100011.m1850&_trkparms=aid%3D222006%26algo%3DSIC.FITP%26ao%3D1%26asc%3D20647%26meid%3D5942965672541399043%26pid%3D100011%26prg%3D9210%26rk%3D3%26rkt%3D10%26sd%3D111020468637
  
 Looking at this then I found this place called Head-Fi?


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## ag8908

I just purchased this from cart100.com and got some 832a vacuum tubes off of ebay. My question is, can a 12au7a work in this? or do you need a 12ax7? thanks


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## DavidK35

Cannot use any "12" series, unless you rewire it (I posted a schematic in an earlier post) . Without rewiring
 you need to use a "6" series, 6AX7 & 6AT7 both work.


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## ag8908

Thanks. I actually cancelled the order after hearing from another source that the internals on this amp are of really low quality. It's powerful and I fear it could ruin expensive headphones. It does look super cool though.


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## DavidK35

IMO you should not listen to fearmongering rumours, unless it comes from multiple sources.
 I have had zero issues with mine. Good luck.


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## MDR30

ag8908 said:


> Thanks. I actually cancelled the order after hearing from another source that the internals on this amp are of really low quality. It's powerful and I fear it could ruin expensive headphones. It does look super cool though.




You get what you pay for, and sometimes you get more! Especially from China.


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## JustinBieber

I'm interested in picking one of these up. I'll replace the cheapo Chinese tubes and probably replace the knobs to something prettier. 

Does anyone have any feedback powering these with the HE-500 or a different pair of planars other than the Fostex? Any background noise, hum, channel imbalance, or any other issues? Info on this are scarce and anything would be appreciated.


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## davejansen

Just chiming in here as there really isn't a whole lot of information available on these amps (nor an actual product name, it seems).
  
 I've picked up one of these to power my Thunderpants (modified Fostex T50RP) at work. Having previously used the surprisingly capable Little Dot 1+ for this very duty, I wanted to try something else and this amp caught my eye for both its looks and pricetag, along with it being a tube amp. I have actually purchased replacement tubes that were recommended by someone else but have yet to receive them, so keep in mind that my initial impressions are for the stock amp and only after having listened to it for about 15 hours or so.
  
 For the sake of completeness; I listen to music from my iMac (using iTunes), using optical out connected to a iBasso D10 Cobra as a DAC, to which the amp is connected. In the photos you see me use a very flimsy 3.5mm to rca cable, that's because my proper cable is currently on its way in.
  

  
 I think the amp looks pretty nice as-is, but can definitely see room for improvement. The knob is fine but it feels plastic-y so replacing the knob itself could be nice. The big power switch on the left makes a proper FLICK sound when you turn it on or off, which I kind of like, but it feels decidedly "homemade." The outside of the headphone jack is plastic and it shows, but you sort of not notice this once you have your headphone plugged in (which is why I have the thing anyway), so it doesn't bother me.
  

  
 The amp, as was mentioned before, gets quite warm. When you adjust the volume you can feel a very apparent glow coming from the big tubes, which slightly light up too, if you look carefully / at an angle. I immediately gave it a listen when I received the amp and listened for about three hours straight, and could notice a rather obvious change in sound quality in that time. It seems quite apparent that this amp (or its tubes, actually) benefit greatly from burn-in. I want to reserve my opinion on the stock tubes until I get the other set (these, in case you're curious), but my initial impressions compared to my memory of the Little Dot 1+ with this headphone is that the bass is a bit more muffled, less punchy. I want to write an addendum to this once I have received and listened to the other tubes, though.
  

  
 The amp matches quite well with the modified Fostex T50RPs that I'm using (Smeggy's Thunderpants), though I wish it had a little more power. Whereas I had plenty of room left on the Little Dot 1+ with these headphones, with certain albums I have to push it over 75% to get it to a good volume level. On the specs listed it supported headphones ranging from 32 to 600 Ohm, but no further information was listed.
  
 That said, they perform admirably. I get the right volume even though I have to crank the knob up more than I'd prefer, but at the same time I notice no obvious sound distortion. I actually don't even notice any hiss or background noise, even when not playing any music. Even with the Little Dot 1+ I'd hear background hiss at higher volumes, so in that sense this one is, somehow, better.
  

  
 Overall I like the amp. While it won't win any awards or probably won't get past a proper review from someone who knows what the hell they're talking about, I _like_ it. It sounds good, it looks unusual in a good way, and it's a pleasure listening to it. Combined with the Thunderpants it gives a nice sound that doesn't tire your ears (I listen all day, every day, so that's important for me), and there's plenty of room to play with this amp, either by putting in some more expensive tubes or by replacing some parts to make it look even better.
  
 I bought mine through Aliexpress for $240 shipped. They even offer 110v and 220v models, which I'm not sure other places offer too.
  
 Hope this helps others that have stumbled upon this intriguing little amp. Please feel free to shoot me a question if you have any.


----------



## DavidK35

Look forward to your review when you have the replacement tubes (NOS I presume).
 You will notice a big difference after a burn in of 3 days,
 24 hours will get 90% of it.


----------



## Nympho

Any clue how this amp may sound with DT990 250OHM on NOS tubes?


----------



## Lorspeaker

these tubes are cute.....


----------



## davejansen

I'm still waiting on my replacement tubes, but I received the 3.5mm to RCA cable I ordered from China a couple of days ago.
  
 Having listened more to the amp throughout the week, I'm enjoying the sound it produces for the most part, though I'm increasingly curious how different things will sound with the tubes I've got coming in. They're by no means fancy ones so I can honestly say I have no idea what the result will be. With these tubes and my headphones bass is quite boomy, more-so than when I used these headphones with the Little Dot 1+ or a cheap Korean-brand HiFi amplifier before. When comparing it to the iBasso D10 Cobra (seen in the photos used just as a DAC) using as an amp, too, I have to say the combination doesn't work very well with my headphones. The Fostex has some pretty sharp highs, and the D10 seems to amplify that, giving it a rather uncomfortable sound. It's far less with this amp, but again, I'm curious what will happen with the replacement tubes.
  
 Overall I tend to listen to more active music at work (where I have this setup), which is why I was looking for something with a bit more "oomph" bass-wise, as compared to my home setup.
  
 A small photo update, mostly focussed on the new 3.5mm to RCA cable. You'll also notice the optical cable bought from the same shop.
  




  
 Thanks for reading!


----------



## borrego

I received the "Deluxe" edition of the amp today. I purchased the amp directly from the manufacturer store in China. I also had the amp modified to have 12.6V filament power supply to use 12AX7 tubes.
  

  
 The deluxe edition of the amp uses aluminum case, and slightly more powerful power supply transformer. According to the manufacturer store, it shall give better dynamics and "sense of space".
  

  
 For those who are interested: the output transformer of this amp (pictured above) have the following output impedance settings: 10ohm when connected to 32ohm headphones, 14.5ohm when connected to 64ohm headphones, 42ohm when connected to 300ohm headphones, and 64ohm when connected to 600ohm headphones. Inductance of output transformer is measured at 17.58H at 100Hhz, and 15.7H at 1kHz.
  
 Other advices from the manufacturer:
 1. The amplifier can "auto detect" the headphone impedance and use the corresponding output transformer settings (I have no idea how but the output transformer picture does have 5 output wires)
 2. Modification to use 12.6V filament has to be done with special attention to avoid A/C current noise.
 3. Don't bother to swap FU32 tubes with Russian GY32 tubes, the FU32 is better
 4. Upgrade FU32 to 832a tubes will result to better treble details. The rest will be similar
 5. The blue wires connecting to the FU32 tubes are with 280V. Thus one must handle those wire with extreme care to avoid electric shock
 6. Proper initial "burn-in" for the tubes should be tuning on the amp listening for approximately 2 hours, then turning off and let the tubes ti cool down, then listening to 2 hours... till the sound more or less settle. It will usually take approximately 20 cycles.
  
 My observations:
 1. The design concept of this amp is to use the cheapest/most widely available tubes in China to make a good sounding amp. Both the 6N2 and FU32 tubes costs around USD2.2 each in China
 2. All FU32 tubes available on the market are NOS. The most recent production was done in early 90's, with some date back to 1959. So even new FU32 tube is at least 20 years old.
  
 Link to the manufacturer shop on Taobao: http://item.taobao.com/item.htm?spm=a230r.1.14.5.wERvfJ&id=35905011085&ns=1#detail


----------



## davejansen

I have received the replacement tubes earlier this week and wanted to give you a small update now that I've had a chance to spend some time with the amp and new tubes.
  

  

  
 The tubes look rather old because of the half washed out prints on them and sprayed-on paint (or whatever it is), but they're not scratched or dinged or anything. The Chinese tubes that came with the amp look better because they're new, but the difference is, quite honestly, not very big. They're a funky looking tube, anyway. But none of this really matters of course, we're here for the sound.
  

  
 I replaced the Chinese tubes with these and flipped the amp on and left it there for about 20 minutes or so before I gave it a first listen. While I believe burn-in is important, I also just really like to listen to music while I work, so I don't mind _experiencing the burn-in with the tubes_, so to speak. Interestingly enough, too, there was an immediate sound quality difference when compared to the Chinese tubes. I'm not a pro in any sense of the word when it comes to describing audio (or experiencing it for that matter), but I'll try my best to put in words what I felt/heard.
  
 Especially as I keep using these tubes, I notice they produce a more open sound, with more separation between instruments. The booming feeling of the Chinese tubes is much less here, too, and seems to keep getting better as more hours are put into these tubes. With certain tracks the playful placing of instruments works really well with these tubes when compared to the Chinese ones, which I really like.
  

  
 Overall I'm very happy with the setup. I'm glad I went for the Russian tubes, the difference is both noticeable and a clear improvement, to my ears anyway. If you end up going for this amp, I recommend you get replacement tubes too, if only just to experience the difference (and choose whichever one you prefer). I bought mine here, it cost me about $30 shipped to get these.
  
 Hope this helps! Feel free to ask me any questions if you have them. I'll try my best to help out.
  
 -Dave


----------



## Nympho

Has any one changed the blue tube wire connectors? They seem incompetent.


----------



## borrego

nympho said:


> Has any one changed the blue tube wire connectors? They seem incompetent.




Those blue wires are running at 280V and get very hot from the FU32 tubes. Typical PVC/PTEE cable jackets will get melt down because of the temperature. I won't bother replacing those.


----------



## Nympho

I am new to tube amps and i have a fluttering sound in my right headphone is that normal burn in?


----------



## Lorspeaker

not burn in....jus a fly gotten trapped in your right cup...


----------



## Nympho

I think the tube may be going bad, I switched the the two RCA 832A and the problem moved to the left headphone.


----------



## JustinBieber

Switch one tube into another socket. If the flutter sound goes into the left channel then one tube is messed up.
  
 If you're talking about this amp, you can grab 832A pairs of tubes on eBay. I imagine it sounds better than the cheapo Chinese tubes this amp comes with.


----------



## borrego

The 832A tubes on ebay are not new tubes (judging from the tube pictures where there are carbon deposite inside the tubes). So one is betting to get a good used pair of 832A.

The best price/performance tube rolling will be to rewire the central tube socket to run 12.6V filament voltage and replace the 6N2 tubes with 5751 tubes. Thus will give the best sound improvement.

If one think the FU32 tubes are "cheap" and inferior, the 6N2 tube will be worse.

Personnally I think the FU32 tubes are perfectly fine, sound performance vise. The best upgrade will be to use 12.6V 5751 tube replacing the 6.3V 6N2. I have checked with the manufacturer directly and it was also their upgrade recommendation.


----------



## DavidK35

You can get replacement USA NOS tubes dirt cheap @ http://www.vacuumtubes.net/prices.htm
  
 $7ea.


----------



## borrego

davidk35 said:


> You can get replacement USA NOS tubes dirt cheap @ http://www.vacuumtubes.net/prices.htm
> 
> $7ea.


 
  
 Wow. If it is really USD7ea for NOS 832A then it is indeed dirt cheep. I just send them an email asking the shipping cost.


----------



## Nympho

maniac said:


> Follow up on the previous post, the amp with the following modification:
> Tube:
> Chinese Beijing FU-32 -> RCA 832A
> Chinese Beijing 6N2 -> JJ 12AX7 (including Filament connection mod on the amp)
> ...


 
 is the unmarked ceramic caps the green ones or the white ones with brownish ends?


----------



## Maniac

White one with brown ends.
  
 Just tap them with something hard, I use my ring (platinum) and it will sound a bit like two pebbles hitting one another, and that's ceramic.  Plastic will sound dull.


----------



## Nympho

maniac said:


> White one with brown ends.
> 
> Just tap them with something hard, I use my ring (platinum) and it will sound a bit like two pebbles hitting one another, and that's ceramic.  Plastic will sound dull.


 
 Thank you very much. Just got my hakko soldering iron today, so i can start practicing before i even try to change them.


----------



## Maniac

nympho said:


> Thank you very much. Just got my hakko soldering iron today, so i can start practicing before i even try to change them.


 
 Good luck, the wiring can be simplified by applying simple logic.  Something like "does this line need to go back and forth for absolutely no reason..." 

 My advice on this amp is that due to the cheapness of the amp, DO NOT drop uber expensive parts in it, it is going to be a waste of your money.  Try out cheap and good parts by all means, save the high end parts for other stuff.

 The amp is limited by the output transformer, and there really is no point going too far when you are limited by the output transformer.


----------



## Nympho

maniac said:


> Good luck, the wiring can be simplified by applying simple logic.  Something like "does this line need to go back and forth for absolutely no reason..."
> 
> My advice on this amp is that due to the cheapness of the amp, DO NOT drop uber expensive parts in it, it is going to be a waste of your money.  Try out cheap and good parts by all means, save the high end parts for other stuff.
> 
> The amp is limited by the output transformer, and there really is no point going too far when you are limited by the output transformer.


 
 I have been thinking hard of keeping the idea of using the FU32 and changing to a 12ax7, then taking out the stereo outputs, and creating my own design. But I still have a lot to learn before I can start on such a big project since I dont have any electronic experience. After I read through a few books I got I can start planning. Also I dont think I'll need 2 output transformers if I go w/o the stereo outputs.


----------



## Maniac

nympho said:


> I have been thinking hard of keeping the idea of using the FU32 and changing to a 12ax7, then taking out the stereo outputs, and creating my own design. But I still have a lot to learn before I can start on such a big project since I dont have any electronic experience. After I read through a few books I got I can start planning. Also I dont think I'll need 2 output transformers if I go w/o the stereo outputs.


 
 What do you mean by taking out the stereo output?  Where do you plan to tap it?


----------



## Nympho

maniac said:


> What do you mean by taking out the stereo output?  Where do you plan to tap it?


 
 Well I don't need the speaker terminals, I only need the RCA input and 1/4" jack so I am guessing the only reason for both output transformers were to have a dedicated one for the headphone and one dedicated for the speaker output. So if I am correct on that then I can get a decent $80 dollar output transformer instead of the two cheap output transformers.


----------



## Maniac

nympho said:


> Well I don't need the speaker terminals, I only need the RCA input and 1/4" jack so I am guessing the only reason for both output transformers were to have a dedicated one for the headphone and one dedicated for the speaker output. So if I am correct on that then I can get a decent $80 dollar output transformer instead of the two cheap output transformers.


 
 No, they don't work like that.  Each transformer is needed per channel, so you will still need two transformer, no matter if you want to use headphone only or speaker only.  Also, I'm not sure about the transformer's configuration, and one with the fitting spec might not be so easily found.

 I'd recommend using this amp to have fun and learn, but don't spend too much money on it, the natural limitation of this machine is there because it is priced so low.  If you want to drop the big bucks, I'd suggest saving it up for a different toy/amp.


 I ended up selling the amp because I didn't plan to custom ordering output transformers for it, as it will just be double or triple of what I paid for the machine.


----------



## Nympho

maniac said:


> No, they don't work like that.  Each transformer is needed per channel, so you will still need two transformer, no matter if you want to use headphone only or speaker only.  Also, I'm not sure about the transformer's configuration, and one with the fitting spec might not be so easily found.
> 
> I'd recommend using this amp to have fun and learn, but don't spend too much money on it, the natural limitation of this machine is there because it is priced so low.  If you want to drop the big bucks, I'd suggest saving it up for a different toy/amp.
> 
> ...


 
 Starting from scratch since the rca 832a runs 6.3v in parallel I could go with an
 Edcor XPWR028  
 but if I ran them in series I could go 12.6v but then there would be a lack of amps, so that probably wouldnt be the best way to go.
  
 Then with (2) Edcor CXPP25-600-8K output transformer that would be a very strong start to the build, then the rest of the build would be the small things that add up cost quickly, resistors, caps, sockets, etc. If I can create a viable schematic Ill sell  the civilian and start from scratch.


----------



## Maniac

IMHO if you start from scratch, there are a lot of other amps you can build, and some of them have much more available tubes for you to choose from...


----------



## borrego

I just received the RCA JAN 832A tubes from vacuumtubes.net, replaced the FU-32s and listened for 3 hours. I have the Shuguang 12AX7M in the middle (like it better than the 50's GE 5751)
  

  
  
 Initial Impression:
  
 Compare to the FU-32s, the RCA 832A definitely gives better mid and treble resolution. The overall sound gives better sense of clarity. But the bass is definitely much weaker and loose. Leonard Cohen's vocal sounds 20 years younger. The RCA 832A also runs cooler compare to the FU-32, I suspect it will give less output power (it is common that Russia/Chinese copied power tubes usually can output higher current)
  
 Depending on one's taste, can't really state the the RCA 832A is better than the FU-32 or vice versa. Please note that my amp is the "deluxe" version with larger power transformer which can better drive the FU-32s.
  
 Will keep burning in those RCA 832A for another week and see if the bass will improve. Will also try pair the GE 5751 with it (but I already found the GE 5751 give loose bass, so might not be good combo with the 832A)


----------



## DavidK35

3 hours is not long enough, give it more time. Also try a NOS 12AT7 WA in place of the 12AX7, every application I have tried them
 they outperform the X's, spec's are almost identical to the 5751.


----------



## borrego

davidk35 said:


> 3 hours is not long enough, give it more time. Also try a NOS 12AT7 WA in place of the 12AX7, every application I have tried them
> they outperform the X's, spec's are almost identical to the 5751.


 
  
 12AT7 would require different coupling cap value and draw much more current compare to 12AX7, so most likely I won't try that.
  
 The Shuguang 12AX7M is the OEM version of the Groove Tube 12AX7M: http://www.sweetwater.com/store/detail/GT12AX7MSel. I can get the Shuguang no marking OEM version for about USD9 ea directly from Shuguang China.


----------



## borrego

Tried the GE 3 mica 50's 5751 with the 832A. The 5751 is a better pairing comparing with the 832A to take the better treble clarity advantage. The bass is more defined and extended now (but still a bit soft). The overall sound signature is like "feather in the air".
  
 I would say the 5751+832A is good for female vocal. The 12AX7M + FU32 is better for male vocal and heavy hitting drums.


----------



## NoPants

can someone post pics of the innards? Are the stages just cap coupled?


----------



## borrego

I found a Japanese page of the amp, which the user replaced the FU-32 with European QQE 03/20 and CV2799 tubes
  
 http://news.livedoor.com/article/detail/8712546/
  
 Just the anodes of the QQE 03/20 and CV2799 tube will be longer than the FU-32/832A will cause potential electric shock hazard.


----------



## waltertlc

I got a unit ...replaced with UK CV tubes...very good. But still having a hard time finding a replacement for the 6n2.

https://scontent-sin1-1.xx.fbcdn.net/hphotos-xtp1/v/t1.0-9/11219603_10153520910409477_1596331254382047647_n.jpg?oh=3bb28f695e35aa64476cfc33da4304ea&oe=567A289D


----------



## borrego

waltertlc said:


> I got a unit ...replaced with UK CV tubes...very good. But still having a hard time finding a replacement for the 6n2.




The Shuguang 7025 is actually a very good balance between details and harmonics, and is very cheap. I am using that with the 832A now.

I also strongly suggest you to get some ceramic/gem beads (those you find on bracelet) to cover those exposed CV tube anodes. Those anodes are running at 300+ volts.


----------



## waltertlc

borrego said:


> The Shuguang 7025 is actually a very good balance between details and harmonics, and is very cheap. I am using that with the 832A now.
> 
> 
> 
> I also strongly suggest you to get some ceramic/gem beads (those you find on bracelet) to cover those exposed CV tube anodes. Those anodes are running at 300+ volts.






The shu guang 7025 is a direct replacement or need to modify the pins? Seems the 7025 is 12AX7 equivalent.


----------



## borrego

7025 is a 12AX7 low noise equivalent. 12AX7 can run with 6.3V filament voltage as with 6n2. I have this confirmed by the Chinese designer of the amp.

The Shuguang need about 15 on/off cycles (each cycle is a 2 hours listening session) to sound best.


----------



## waltertlc

swapped out the CVs with RCAs ...wow...my thoughts were they sound pretty much like SS amps..
11990471_10153549315924477_1908793972645639067_n.jpg


----------



## waltertlc

Update ... bought a tube adaptor to fit 5670 tubes into the 6n2 ... lost some gain ..and the sound quite different...
12039192_10153572898569477_3865869452169994498_n.jpg


----------



## MIKELAP

To use the 12ax7 tube did i see correctly you strap heater pins 4 and 5 together dont understand schematics could anybody have a picture of the new configuration of the wires.Thanks


----------



## MIKELAP

Here are a few pictures of inside of 6N2+FU32 amp


----------



## Jeffr005

Thanks for the photos MIKELAP.
  
 I received the same amp about a month ago, for under $300 I am really impressed with how the amp sounds.
  
 Build quality is pretty good as well!
  
 I purchased mine from aliexpress.com


----------



## MIKELAP

jeffr005 said:


> Thanks for the photos MIKELAP.
> 
> I received the same amp about a month ago, for under $300 I am really impressed with how the amp sounds.
> 
> ...


 
 Yes it is decent have several different power tubes and also expecting 12v adapters to use 12ax7 types right now using 6AX7 and 1509 Russian power tube also have 832, 832a,and GU32.


----------



## MIKELAP

mikelap said:


> jeffr005 said:
> 
> 
> > Thanks for the photos MIKELAP.
> ...


----------



## Jeffr005

Please keep us all updated once you have made the changes and if it is something that you would recommend as well.


----------



## MIKELAP

Interesting review but will have to translate also reviewer list compatible tubes               http://news.livedoor.com/article/detail/8712546/


----------



## MIKELAP

I was reading earlier on this thread that you could modify the amp socket to accept 12 v. tubes since then adapters became available 12AX7 TO 6N2 I bought this one from Ebay should receive it shortly     http://www.ebay.com/itm/281787284149?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT


----------



## MIKELAP

I received 12V. tube adapters yesterday and i gotta say 12v tubes sound very good in this amp compatible 12v tubes i found decent are 5751,12AX7,ECC81/12AT7, CV4024.,5814A. But best of all no need to modify amp socket.


----------



## Jeffr005

Hey Mike,
 Thanks for the update!
  
 Do you recommend the 12V. tube adapters? They seem pretty inexpensive too.
  
 What tubes are you currently running?


----------



## MIKELAP

jeffr005 said:


> Hey Mike,
> Thanks for the update!
> 
> Do you recommend the 12V. tube adapters? They seem pretty inexpensive too.
> ...


 

 If you like tube rolling i would recommend getting a 12v adapter but differences between 12v and 6v. are not that obvious i have the 12v.=5751,12AX7,ECC81/12AT7, CV4024.,5814A. and 6v.= 6n2, 6N2P-ER, 6DT8,6AX7. and i must say that imo they all sound good but like they say YMMV .I am currently using a Mullard  ECC81/12AT7 & switching with a 6AX7 and i would say the 6AX7 is cleaner sounding than the warmer Mullard, that's using Senns HD800.Will be installing these anode caps soon dont really like the stock                                                   connectors,                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      
  
 caps are safer i would think


----------



## MIKELAP




----------



## Jeffr005

Looks good.
 I totally agree with you on the stock connectors. That is an area where cost savings was really flexed.
 Where did you pick up those caps from?


----------



## MIKELAP

jeffr005 said:


> Looks good.
> I totally agree with you on the stock connectors. That is an area where cost savings was really flexed.
> Where did you pick up those caps from?


 
 Although the caps get very very hot they seem to be ok not melting.                                                          http://www.ebay.com/itm/281852097107?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT


----------



## inexorableend

I'm really interested in this amp. How does it compare to, E.g., the Magni 2 Uber? Has anyone tried it with planars? What about with speakers/bookshelves?


----------



## borrego

inexorableend said:


> I'm really interested in this amp. How does it compare to, E.g., the Magni 2 Uber? Has anyone tried it with planars? What about with speakers/bookshelves?




No comparision, the 6n2 FU32 amp is a "proper" SE tube amp circuit design, with output transformers, AC heater power supply, choke transformer (in upper model). While the Magni 2 Uber is a solid state design using external switching DC power supply.


----------



## borrego

Earlier this week I put in a top of the line Shuguang 12AX7-T to pair with the 2 RCA 832a. Compares to the previous Shuguang 7025, now the bass goes a bit deeper and with more textures, treble has a little bit more harmonics. Now the amp is perfect for my taste.

Please note that my amp was modified having 12.6V heater voltage right from the factory.


----------



## MIKELAP

inexorableend said:


> I'm really interested in this amp. How does it compare to, E.g., the Magni 2 Uber? Has anyone tried it with planars? What about with speakers/bookshelves?


 
 i tried this amp with 40 ohm Fostex TH500RP planars and this amp is not powerful enough for planars but this amp works great with 300ohm Senns HD 800 ive also tried it with vintage KEF 104 but those speakers are not efficient enough its not bad at low volume but thats it ..


----------



## MIKELAP

borrego said:


> Earlier this week I put in a top of the line Shuguang 12AX7-T to pair with the 2 RCA 832a. Compares to the previous Shuguang 7025, now the bass goes a bit deeper and with more textures, treble has a little bit more harmonics. Now the amp is perfect for my taste.
> 
> Please note that my amp was modified having 12.6V heater voltage right from the factory.


 
 You could have simply bought an adapter thats what i did and it  works great .


----------



## MIKELAP

Received 2 pairs of Haltron QQE03/20 the sound compares to others tubes i have ,the main differences is the size of the tube which is smaller than for example the 832 , and distance between the 2 anode pins on top of tubes are closer together and are slightly bigger  if you use the stock connectors you will have to enlarge the female part of connector for anodes to fit in which will be loose after when going back to other tubes with smaller anode pins so might not be a good idea to try this tube ,unless you have spare connectors that you can rig to use specifically for those tubes


----------



## MIKELAP

These anode caps will not fit on HALTRON QQE03/20 tubes (pic..#2 tube on the right ) as the anode pins are closer together some modification is required to the caps due to clearance issues                                                                                                                                                                                                                                                                                                                                                                        
 #2


----------



## Seamus3900

Hi, New here but I have the HALTRON QQE03/20 tubes on this same amp, just filled down the pins a little so they would fit but I don't think they are as good as the stock tubes. For me they sound weaker and less bass , not sure how to describe it in words 
	

	
	
		
		

		
			





.  I have a lot of 12AX7 tubes so I might try to get that adapter you recommend from ebay and see if that helps the sound. Its a nice looking amp but can't drive my audeze lcd-2's at all but nice with my NightHawks.


----------



## hitchcaster

no, they "work" with adapters but still the tube isn't getting the 12v it wants to see to work correctly... so the tubes won't sound the same with the adapter then if they had the voltage adjusted from 6v to 12... ive got some adapters arriving tomorrow so i am going to try it anyways     
  
 to folks who modded to 12v..   how do you get 12v?  is there another tap on the transformer?


----------



## MIKELAP

Received a new adapter today  with this one a 6SN7 tube can be used  in the driver spot


----------



## ChopperCharles

If I mod this amp, will it give me more gain with 12AX7s? I have a pair of power-hungry orthodynamics that really need a bunch of juice.
  
 Charles.


----------



## borrego

choppercharles said:


> If I mod this amp, will it give me more gain with 12AX7s? I have a pair of power-hungry orthodynamics that really need a bunch of juice.
> 
> Charles.


 
  
 Your orthos likely need current more than voltage (gain) to be driven well. I have no problem having the amp driving my HE-500. Though I already have the amp modded to use 12AX7 from the factory.


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## ChopperCharles

So is that a no? They're Yamaha YH-2 drivers.  What would I need to drive them to ridiculous volume levels? Right now a Toshiba SY-665/SC-665 pre/power amp is doing that job, but I'd rather have something small and cute to bring to work. 
  
 Charles.


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## hitchcaster

any one try upgrading transformers on this?  or at least know the specs of the OT's and choke?   the RCA 832a's sound really good and not broken in yet


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## borrego

hitchcaster said:


> any one try upgrading transformers on this?  or at least know the specs of the OT's and choke?   the RCA 832a's sound really good and not broken in yet



The OTs are one of a kind with no other manufacturer makes. Specification is here: https://www.head-fi.org/f/threads/civilian-6n2-fu32-tube-headphone-amp.671419/page-3#post-10853175

Given the price of the amp, it does not have much economic sense to upgrade the OT and choke. You may want to try replacing the stock PIO coupling capacitors with Russian FT-3/FT-1 capacitors if you want more resolution, which can be done relatively cheap.


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## hitchcaster

borrego said:


> The OTs are one of a kind with no other manufacturer makes. Specification is here: https://www.head-fi.org/f/threads/civilian-6n2-fu32-tube-headphone-amp.671419/page-3#post-10853175
> 
> Given the price of the amp, it does not have much economic sense to upgrade the OT and choke. You may want to try replacing the stock PIO coupling capacitors with Russian FT-3/FT-1 capacitors if you want more resolution, which can be done relatively cheap.



yes thank you... the amp is actually pretty high quality and a simple circuit...  i put some mustard .33's in it when i first got it.. the stock caps are pretty goofy/cheap...  volume pot is cheap so i upgraded that also.   i was thinking of trying some u-caps since they are affordable vcap copies.. the russian teflons i think are good but ive never got them to beat high end caps made for audio, so id rather spend a little more when i consider those.    interesting the OT's can't be upgraded.. thanks!


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## MIKELAP

If anybody is interested in buying the FU32-6N2 Headphone /Speaker Amp i have one for sale .It has low hours around 1 1/2 year old i also have adapters to use 12ax7 and 6sn7 tubes .Also i have 12 pairs of different brands for sale PM me if interested .Thank you


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## Origen Ru (Jun 5, 2019)

borrego said:


> I just received the RCA JAN 832A tubes from vacuumtubes.net, replaced the FU-32s and listened for 3 hours. I have the Shuguang 12AX7M in the middle (like it better than the 50's GE 5751)
> 
> 
> Did you clean the pins of the with RCA JAN 832A  some jeweler's cloth to remove the black color (oxide) ?.
> ...


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## Origen Ru

This is my Little Bear P32 which included a GU 32 Chinese tube.


 
Replace the Chinese GU32 tube with the RCA CRC 829B and the OPAmp NE5532P with a Burson V6 Vivid, at first it sounded lacking in low and medium because it came with the black layer of oxide on the pins of the bulb, clean with a jeweler's rag for an hour until they were silvery and bright, I tried it and the sound is now magnificent.


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## MIKELAP (Sep 7, 2020)

Origen Ru said:


> This is my Little Bear P32 which included a GU 32 Chinese tube.
> 
> Replace the Chinese GU32 tube with the RCA CRC 829B and the OPAmp NE5532P with a Burson V6 Vivid, at first it sounded lacking in low and medium because it came with the black layer of oxide on the pins of the bulb, clean with a jeweler's rag for an hour until they were silvery and bright, I tried it and the sound is now magnificent.


How did that go replacing the GU32 by a  829B  ? You can use that tube in your amp ?


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## Hal Rockwell (Sep 13, 2020)

I own the Little Bear P32 and decided to mod it with the 829B tube. It seems like 829B being a higher wattage equivalent of 832A. In any case, the pin-out is the same and the tubes in this amp run in starvation mode. I already own the Burson V6 Vivid. Lets see where it gets me.
I'm going to do additional mods too, like replacing the power button in the back, with a toggle switch in the front.


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## Hal Rockwell

MIKELAP said:


> How did that go replacing the GU32 by a  829B  ? You can use that tube in your amp ?














Well I can confirm that 829B works in Little Bear P32, and so far it sounds very promising.


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## MIKELAP

Also tried the 829b tube with A 6SC7 AS driver with adapters in the Civilian amp works nicely transformer temp is 50c after a few hours of run time


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## hitchcaster

i have to switch mine to 120v for usa use... was using it overseas... anyone know where to get a PT with these specs or close that work?   maybe a better PT would sound better then the cheap chinese one anyway... thanks!


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