# Posted new design:  "Jonokuchi" destop amp



## pmillett

People have asked me for a DIY tube headphone amp design that will drive small speakers (like computer speakers) for quite a while.  I just posted such a design, called "Jonokuchi" (Jonokuchi refers to the beginner ranking of sumo wrestlers).
   
  Details are here:
   
http://www.pmillett.com/Jonokuchi.htm
   
  It's a simple amp, nothing revolutionary, using 13EM7 tubes.  It can be built point-to-point, or I have a PCB available that makes it an easy build for a newbie.
   
  Pete


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## holland

It looks like a fun and easy build, particularly with the PCB.  Thanks for sharing it.


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## Uncle Erik

I like those graphs!

Thank you for another great project Pete - you've done so much to help our hobby along.

Now... do I have a spare $200 around here somewhere....


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## nikongod

Thanks for sharing this amp, it looks like a fun build!


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## n3rdling

Perfect for what I need 
   
  I've decided to make this my first build.  I ordered the Edcor transformer package you set up on their website.  Right now I'm going through the BOM, and found a minor mistake and also had some questions.
   
  For part "Resistor, 220k ohm 2W small film", the quantity is 2 but should be 3 I believe, as you have it listed for R4/R6/R7.  There are also two small price miscalculations on your BOM: 1. you listed the price of the PCB as $30 instead of $40, and 2. on the speaker binding posts you put quantity 2 but didn't extrapolate the price accordingly. 
   
  For "Resistor, 330 ohm 2W small film", Mouser has a minimum order limit of 2000 for part number "660-SPR2LT521R331J" .  I see you have these resistors starred with the comment that others can be used.  I'm guessing there should be no problem if I use the alternative "594-5083NW330R0J" which is a metal film resistor, even though the rest of the resistors I have in my cart for this amp section are carbon film?  Or would I need to use purely metal film resistors in this case?
   
  Once the above concern is confirmed or denied, I will make the mouser project public and post it here with in stock parts for people who wish to build this cool little amp.


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## nikongod

One can mix various resistor brands & types freely as long as power ratings (and in some extremely high voltage amps voltage ratings {does not seem to apply here, and almost never in a cathode resistor, just general FYI}) are respected. 
   
  The KOA SPR carbon films in the BOM are pretty pimp, and the amp looks like sex with the green resistors on the red PCB. Perhaps a call or email to mouser is in order? They sell most other values in that line as singles, and 330ohms is not exactly an unusual value.


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## spritzer

You can always pay more for the same resistors by buying from the boutique sellers.  Kiwame is the same as the Koa SPR series.  There are a lot of good 2W resistors out there so the sky really is the limit.


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## HiGHFLYiN9

Looks great Pete, you can count me in to put one together


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## HiGHFLYiN9

Pete, unless the board has changed from what you have on the site, you may want to switch these on the BOM:
   
  C9+C10 to C5+C6 (0.1uF 630V)
  C14+C15 to C9+C10


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## pmillett

Quote: 





n3rdling said:


> For part "Resistor, 220k ohm 2W small film", the quantity is 2 but should be 3 I believe, as you have it listed for R4/R6/R7.  There are also two small price miscalculations on your BOM: 1. you listed the price of the PCB as $30 instead of $40, and 2. on the speaker binding posts you put quantity 2 but didn't extrapolate the price accordingly.
> 
> For "Resistor, 330 ohm 2W small film", Mouser has a minimum order limit of 2000 for part number "660-SPR2LT521R331J" .  I see you have these resistors starred with the comment that others can be used.  I'm guessing there should be no problem if I use the alternative "594-5083NW330R0J" which is a metal film resistor, even though the rest of the resistors I have in my cart for this amp section are carbon film?  Or would I need to use purely metal film resistors in this case?


 
   
  You are correct, the 220k resistor should be 3 pcs. - thanks, I will fix the BOM.  On the 330 ohm, the part you mention is fine. 
  
  Quote: 





nikongod said:


> The KOA SPR carbon films in the BOM are pretty pimp, and the amp looks like sex with the green resistors on the red PCB. Perhaps a call or email to mouser is in order? They sell most other values in that line as singles, and 330ohms is not exactly an unusual value.


 

 I agree!  I guess I didn't notice the minimum was a full reel at Mouser! 
   
  Quote: 





spritzer said:


> You can always pay more for the same resistors by buying from the boutique sellers.  Kiwame is the same as the Koa SPR series.  There are a lot of good 2W resistors out there so the sky really is the limit.


 

  Parts Connexion has the "Kiwames" in almost every value, so that is an option to keep all the same resistor type.
  
  Quote: 





highflyin9 said:


> Pete, unless the board has changed from what you have on the site, you may want to switch these on the BOM:
> 
> C9+C10 to C5+C6 (0.1uF 630V)
> C14+C15 to C9+C10


 

 You are correct.  I thought I fixed that, but maybe I forgot to push the update to the web site.  Sorry for the confusion!


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## pmillett

OK, the BOMs should be fixed.  Freaky - my local copy had been updated, but for some reason when I published the website updates these files did not get replaced, even though a newer copy existed in my local web.  So I manually deleted the files on the server and re-published.
   
  Guess I have to enter the current century and dump FrontPage one of these days.
   
  Pete


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## Region2

Wow, nice design.  I just added this to the list.  Definitely interested and I love how accessible you made it for DIYers of all levels.


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## the_equalizer

Looks great!   Thanks for sharing yet another neat amp!


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## budx3385

Has anyone built this amp yet? I would very much like to know how it sounds!!!


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## c12mech

This has now been added to my list to build.  I like the fact that it is right in a good price range with the PCB.  I will most likely do it p-t-p though.  I just like the freedom of lay out that way.


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## pabbi1

I've gotten as far as tubes... just a couple of projects to finish up first.


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## n3rdling

Got my parts from mouser in the mail today and almost finished populating the board while watching basketball.  This is a lot of fun!  I have a couple questions and things I noticed:
   
   
  On the BOM you forgot to put the 10 Ohm 2W resistors for R22/R23
  On the BOM for the caps at C1/C2 the "value" and "description" are different.  Should I use 1uF/63V or 1uF/100V?
  I know the LEDs have a negative and positive lead, but the board doesn't indicate polarity.  Does orientation matter on this amp?
  In your picture of the populated PCB it looks like you have some kind of jumper installed at JP1.  I didn't see a JP1 on the BOM...what is that part and is it necessary?
   
  The wirewound resistor I'm using at R5 is the recommended part in the BOM ( 71-CW005220R0JE73 ).  I ordered two of these (one backup) from Mouser and the package is labeled correctly but I'm wondering if they put the wrong resistors in the package.  The following text is printed on the resistor:
   
  DALE
  CW-5
  220 Ohm 5%
  6.5W
  M1016
  MEXICO
   
  The part that confuses me is the "6.5W".  Is this normal?  I am looking at the data sheet for those resistors ( http://www.vishay.com/docs/30215/cw.pdf ) and I can see a CW-5 under "historical model" and then the corresponding data shows a Characteristic U of 5.0 and a Characteristic V of 6.5...I'm guessing that explains the confusion and there's nothing to worry about?  This is my first build so I'm being extra cautious so nothing blows up on me. 
   
  Once I find out the answers to these concerns I'll put in a second Mouser order and hopefully the amp will be done next week!  I'll probably do some of the chassis work tomorrow.


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## HiGHFLYiN9

Mine's populated but I'm waiting on some particular ceramic tube sockets from Hong Kong. It looks like Pete used some plastic / phenolic sockets that are relatively straight without side protrusions for mounting to a chassis in order to make use of the relatively small 1/4" standoffs. Once those sockets come in I can finish the drilling of the chassis and get it off to the powdercoater along with the Edcor Bells.
   
  N3rdling, The 10ohm resistors were missing on the BOM as you noticed, I mentioned it on DIYAudio but forgot to post it here. You don't have anything to worry about with the resistor. The BOM calls for a 5W and you have a higher spec'd 6.5W, no worries. The orientation of the LEDs is shown on the schematic.


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## pmillett

Quote: 





n3rdling said:


> On the BOM you forgot to put the 10 Ohm 2W resistors for R22/R23
> On the BOM for the caps at C1/C2 the "value" and "description" are different.  Should I use 1uF/63V or 1uF/100V?
> I know the LEDs have a negative and positive lead, but the board doesn't indicate polarity.  Does orientation matter on this amp?
> In your picture of the populated PCB it looks like you have some kind of jumper installed at JP1.  I didn't see a JP1 on the BOM...what is that part and is it necessary?
> ...


 

  
  Yes, I left off the 10 ohm resistors on the BOM.  Sorry, need to fix that.  Though they are not strictly required, they help to lower the noise caused by coupling from the power transformer to the output transformers, and also make the amp perform more consistently into differing headphone impedances.
  
  The caps should preferably by 100V.  63V is OK but has very little margin. 
   
  The LEDs do need to be oriented correctly.  The end closest to the tube sockets is the anode... so anode/cathode of the upper LED and anode/cathode of the lower LED.
   
  JP1 is there so you can short out the ground loop breaker if you want.  You should not need anything there.  If you experience hum problems you can try shorting it.
   
  The 5W (6.5W) resistor is fine.  Dale up-rated the power on many of their wirewound resistors.  Just a spec change, same part.
   
  Quote: 





highflyin9 said:


> Mine's populated but I'm waiting on some particular ceramic tube sockets from Hong Kong. It looks like Pete used some plastic / phenolic sockets that are relatively straight without side protrusions for mounting to a chassis in order to make use of the relatively small 1/4" standoffs. Once those sockets come in I can finish the drilling of the chassis and get it off to the powdercoater along with the Edcor Bells.
> 
> N3rdling, The 10ohm resistors were missing on the BOM as you noticed, I mentioned it on DIYAudio but forgot to post it here. You don't have anything to worry about with the resistor. The BOM calls for a 5W and you have a higher spec'd 6.5W, no worries. The orientation of the LEDs is shown on the schematic.


 

 Good observation on the sockets.  I used some sockets that do not have that "lip" that most of the ceramic sockets have.  So you will need to match the hole in your chassis to the socket.  FYI, the sockets I used are really good, tight (phosphor bronze!), and cheap.  They come from Allied... https://www.alliedelec.com/search/productdetail.aspx?SKU=5870024
   
  Pete


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## n3rdling

Thanks for the help guys.   Everything soldered into place.  Now I just need to get those 10 Ohm resistors and the tube sockets/diodes are in the mail right now.  Just double checking but I won't need to drill different holes than what is shown on the guide if I'm using these sockets right? http://www.partsconnexion.com/product9597.html  Also, what knobs did you guys settle on?


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## pmillett

Quote: 





n3rdling said:


> Thanks for the help guys.   Everything soldered into place.  Now I just need to get those 10 Ohm resistors and the tube sockets/diodes are in the mail right now.  Just double checking but I won't need to drill different holes than what is shown on the guide if I'm using these sockets right? http://www.partsconnexion.com/product9597.html  Also, what knobs did you guys settle on?


 

 If you use 1/4" standoffs, you will have to make the tube socket holes bigger than I did, because the flange on the ceramic socket will not fit into the hole.
   
  Pete


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## wotts

I saw this and thought it would be a fun project. I finished populating the board a few days ago, and just ordered the FPE kit. I swapped the color to dust magnet (black anodize) and changed the in-lay color. When the case comes, I'll post some pictures. Thanks for a cool project Pete!
   
  -Tim


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## wotts

The case came so here are the pictures. I also included some of the pictures of my board, complete with the sockets on the wrong side. I fixed that and there is a picture of that as well. And there are a few internal shots of the I/O wiring. I'm now waiting on the transformers. Enjoy!


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## wotts




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## the_equalizer

Looks VERY nice, so far!!


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## c12mech

Looks good.
   
  I'm looking forward to hearing some listening impressions for one of these.  I'm on the fence as to whether or not to build this one.  The price is definitely right in my range.


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## HiGHFLYiN9

Doh, I bet it was tough to get those tube sockets flipped around, 8 pins to desolder. I probably would have cut my losses, snipped the pins and desoldered them individually. 
   
  I'm pretty much finished drilling out the hammond chassis on mine, just have to run it over to the powdercoater. I ended up using the allied sockets that Pete used.


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## wotts

I used about 3ft of .1" solder braid and numerous shot of the desolder pump. 
	

	
	
		
		

		
			





  There were a few Sam Adams that helped along the way. I'm not sure if I mentioned it already, but I missed the part about the case needing the socket holes to be bigger when using the sockets on the BOM, so I had to ream them out. Ended up using a large step bit and them brought it to work and used a deburring tool on it. 

  
  Quote: 





highflyin9 said:


> Doh, I bet it was tough to get those tube sockets flipped around, 8 pins to desolder. I probably would have cut my losses, snipped the pins and desoldered them individually.
> 
> I'm pretty much finished drilling out the hammond chassis on mine, just have to run it over to the powdercoater. I ended up using the allied sockets that Pete used.


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## n3rdling

I actually finished mine about two weeks ago and it's been running perfectly ever since.   I'll post more about it when I'm able to take some pics.


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## wotts

How long did it take to get the transformers? I think I was quoted a 4-6 week lead time.


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## HiGHFLYiN9

It took four weeks before mine shipped from Edcor, which is a very typical turn-around time for them.


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## wotts

Cool. Getting excited to get this finished.  Anyone tested speakers with this? I was looking at the passive AudioEngine speakers myself...


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## n3rdling

I think it took about 3 weeks for me to get my transformers. 
   
  A large reason I decided to build this amp is because I have a set of bookshelf speakers I use at my computer (where my headphone system is located) and the amp I was using before was some cheap Chinese 150W speaker amp.  With that amp I couldn't really adjust the volume at all or it'd blast my head off, so I ended up having to use windows volume control at like 10%.  Very annoying.  This amp puts out something like 3W I believe and it is just perfect for me.  It can drive the bookshelves louder than I need and I get tons of play on the knob.  Sounds good too.


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## ujamerstand

Which bookshelf speakers do you have? I'm interested in knowing what other stats fans have for their speakers.


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## n3rdling

My bookshelf speakers are McIntosh LS320.  My main speakers are Quad ESL-57.


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## ujamerstand

Quad ESL! Of course haha! 
   
  The McIntosh bookshelfs looks really sturdy. I'll take that into account when I decide to upgrade from my crappy polk audio speakers, thanks!


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## wotts

I just received my shipping notification for my transformers! I should have this completed next Friday. Woohoo!!


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## HiGHFLYiN9

I'm currently putting the finishing touches on my build, did anyone else finish up theirs?


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## wotts

Mine is done. I'll get some more pictures posted - i have some in my profile. I truthfully have not spent much time with it since I bought the HE-6s. They are a little demanding, but I'll try to get some impressions on the amp written up as well.


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## n3rdling

This amp is awesome   I've had it on for about two months straight with no problems at all.


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## vmvietnam

It looks very nice and PROFESSIONAL design bro! I wish i could make one for myself !


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## wotts

I uploaded some new pictures. I did not resize them...might be HUGE.


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## HiGHFLYiN9

Good work on yours Wotts, I'm surprised you fit the ceramic tube sockets in there so well, congrats!  
   
I'm finally all done! Here's a few pics:
   

   

   
   

   
   
  Tubes seem to be tough to find, most of the tube suppliers only have one or two 13EM7s sitting in their inventory; it's hard to find two of the same type with the exception of Raytheons and GEs. 
   
  Full build details and pics are available here: http://www.diyaudioblog.com/2011/02/starting-pete-milletts-jonokuchi.html​


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## wotts

Wow! That looks amazing! May I ask where the case came from? I read the blog, didn't notice that on the first pass through.
   
   
  I don't recall where I got my tubes from, but they are Westinghouse. Maybe a rebrand? I bought a second pair on ebay. Those are RCA. As for the sockets, I had to ream out the top plate to make them fit. They still rise out of the case about 1/4".


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## n3rdling

VERY nice!


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## Blueimac

First Tube Amplifier build but after deciding on the "Jonokuchi" destop amp as a first build I haven't been able to find any recent updates form other builders, I have some questions to be answered and hopefully will find some help here - I'm looking forward to getting the PCB soon so I can get started. 
   
   
   
   
   
  First question is about the #6-32 x 1/4" standoffs for supporting the PCB, Should the standoffs be metal (which I'm assuming would ground the PCB to the chassis) or Nylon to prevent grounding the PCB ?
   
   
  Second - Would a pair of Sylvania GE 6EM7 tubes be a suitable replacement for the 13EM7 13v filament tubes ? I haven't been able to find many 13EM7 tubes and was wondering if there are any tubes that could be used as replacements ?
   
   
  Any input on better quality replacements for C5 and C6 - 0.1uF 630V coupling capacitors ? I've been looking at the Obbligato Gold Premium Capacitors 
   
   
  Last - I'm thinking about a minimalist chassis design with a cleaner look, Would it be possible to conceal the three transformers inside the chassis if kept away or _shielded_ from the PCB ?
   
   
   
   
Also for anyone who may be building this project soon here's one update for now on the Jonokuchi BOM as this part is no longer available from Mouser -
   
   
  D1 - Fairchild Bridge rectifier 2A 50V - 3N253  (Mouser Part # 512-3N253) is no longer available so I'm using the following in it's place 
   

 *Mouser Part #:*  625-2KBP005M-E4
 *Manufacturer Part #:*  2KBP005M-E4/45 
 *Manufacturer:*  Vishay Semiconductors   
 *Description:*  Bridge Rectifiers 2.0 Amp 50 Volt


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## Blueimac

First Tube Amplifier build but after deciding on the "Jonokuchi" destop amp as a first build I haven't been able to find any recent updates from other builders, I have some questions to be answered and hopefully will find some help here - I'm looking forward to getting the PCB soon so I can get started. 
   
   
   
   
   
  First question is about the #6-32 x 1/4" standoffs for supporting the PCB, Should the standoffs be metal (which I'm assuming would ground the PCB to the chassis) or Nylon to prevent grounding the PCB ?
   
   
  Second - Would a pair of Sylvania GE 6EM7 tubes be a suitable replacement for the 13EM7 13v filament tubes ? I haven't been able to find many 13EM7 tubes and was wondering if there are any tubes that could be used as replacements ?
   
   
  Any input on better quality replacements for C5 and C6 - 0.1uF 630V coupling capacitors ? I've been looking at the Obbligato Gold Premium Capacitors 
   
   
  Last - I'm thinking about a minimalist chassis design with a cleaner look, Would it be possible to conceal the three transformers inside the chassis if kept away or _shielded_ from the PCB ?
   
   
   
   
Also for anyone who may be building this project soon here's two updates for now on the Jonokuchi BOM as these parts are no longer available from Mouser - 
   
   
C1,C2 - 1uF 100V film cap 5mm LS  Wima (Mouser Part# 505-MKS21/100/10) using the following in it's place 
   
*VISHAY-RODERSTEIN*
 [size=1.2em] *MKP-1837 Metalized Polypropylene*[/size]
 [size=1.2em] *Film Capacitor*[/size]
 [size=1.2em]  [/size]
 [size=1.2em] http://www.partsconnexion.com/capacitor_film_visrod.html#14846[/size]
   
   
  D1 - Fairchild Bridge rectifier 2A 50V - 3N253  (Mouser Part # 512-3N253) using the following in it's place 
   

 *Mouser Part #:*  625-2KBP005M-E4
 *Manufacturer Part #:*  2KBP005M-E4/45 
 *Manufacturer:*  Vishay Semiconductors   
 *Description:*  Bridge Rectifiers 2.0 Amp 50 Volt


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## Greystoke

I've got the PCB for this kit almost fully populated, waiting on tube sockets (got a couple of different styles to try) before cutting the top plate.  I've also left off the switches and jacks on the front edge, thinking of doing a slightly larger case so I'll need to adjust the spacing of the front controls.
  
 I didn't realize until I started this post that this is kind of a necro-thread; anyone built one of these kits lately?


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## tdubl07

This build was a fun one. And requires patience since ordering the transformers took about 6-7 weeks for delivery. Well worth it. Lots of power, and sounds great. Anyone thinking about building one, go for it. Tubes are still readily available if you know where to look. Check antique radio supply or vacuumtubes.net


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## vmvietnam

So kool! Thanks for sharing yet another neat amp!


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## guppysb

Hey Guys,
  
 Thank you Mr. Millett for creating such wonderful projects for us do to. Just bought all the parts, and I guess the transformers will arrive in 6-8 weeks. So excited, this is my first DIY project. I have a Computer Engineering degree, but nowhere close to that of a EE, so just a bit nervous about the high voltage. If you guys don't mind, I have a few questions:
  
 1. What gauge of wiring should be used for the speaker binding posts to the PCB, along with the RCAs?
  
 2. I see that HighFlying9 added a power light to the project. If I wished to add an LED, perhaps with an inline resistor to ground, where should I connect LED in terms of power to? It's been a while since I did some EE, software engineering is a bit easier, hehe. Using this as a reference: http://electronics.stackexchange.com/questions/32965/add-on-off-indicator-led-to-circuit
  
 Please let me know if there is an easier solution.
  
 3. It looks like both the 1/4" and 1/8" jacks can be placed on the board. I have the Sennheiser HD 650 and a BeyerDynamic DT 990 250 ohm. That's a combined impedance of roughly 550 ohms. Would the amp be able to drive both sets of headphones at once, one placed on the 1/4" and another on the 1/8"? 
  
 4. I also have a set of Behringer Audio Truth 3030A (active studio near field monitors), which I connect using a direct input box (input is RCA, output is balanced XLRs to the speakers). Will I have any issues if I use the output of the 1/4" or the 1/8" to RCA to send the signal to the direct input box? Just curious as to your take on it.
  
 5. I've been doing a lot of reading at: http://www.diyaudio.com/forums/tubes-valves/182269-jonokuchi-new-desktop-amp-little-red-board.html
 It seems that spacing the OPTs by 2 or more inches away from each other helps the hum. I am thinking of going with acrylic as an enclosure, instead of a metal one. Will I have issues with the POT humming with acrylic, or any other issues?
  
 Sorry if I have really dumb questions, just trying to learn a bit. Thanks for the help.


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## zeroecco

Built one of these myself,
  
 I have to say that on my beyer T70's this amp struggles a bit. I have to run at close to full tilt to get the volume these headphones need.


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## guppysb

Hey Guys, Finally finished putting the amp together this weekend, after all the parts arrived. I am, however, having some issues. I would appreciate any suggestions for debugging the following issue: I have very little sound output from the left channel. It does not matter if I use 1/8" front or the rca rear inputs. It also does not matter if I use the 1/8" or the 1/4" outputs. Perhaps a bad ground? Also, when I slightly move the amp or the pot, I get static on the left channel as well. With a little bit of moving the amp, the static goes away. Everything seems to be left channel related. I don't have passive speakers to test the speakers output, so this is strictly a headphone out issue so far. Please let me know what I can debug, would greatly appreciate any help.


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## Mr Rick

guppysb said:


> Hey Guys, Finally finished putting the amp together this weekend, after all the parts arrived. I am, however, having some issues. I would appreciate any suggestions for debugging the following issue: I have very little sound output from the left channel. It does not matter if I use 1/8" front or the rca rear inputs. It also does not matter if I use the 1/8" or the 1/4" outputs. Perhaps a bad ground? Also, when I slightly move the amp or the pot, I get static on the left channel as well. With a little bit of moving the amp, the static goes away. Everything seems to be left channel related. I don't have passive speakers to test the speakers output, so this is strictly a headphone out issue so far. Please let me know what I can debug, would greatly appreciate any help.


 
 I would start by swapping the tubes around. If the problem stays on the left channel I would start looking for cold soldered joints or loose connections.


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## guppysb

Quote:


mr rick said:


> I would start by swapping the tubes around. If the problem stays on the left channel I would start looking for cold soldered joints or loose connections.


 
 Thanks for the reply Rick!
  
 I had swapped the tubes and it didn't make a difference. I originally thought the issue was with my 1/8" output jack and so I de-soldered it and replaced it with a new one. Now, not only do I have the same issues as before (can't really hear left channel), there is also a loud buzzing on the right channel. The buzzing gets louder as I increase the volume. I inspected all the solder joints to make sure there was enough solder and there weren't any solder bridges. Checked for continuity with my DMM. I guess I'll just try to resolder the shifty looking joints tomorrow.


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## wotts

As for the buzzing, did you install the jack with the updated instructions on Pete's website? I think there are resistors added to the rear legs of the jack. I'd have to look to be sure.
  
 I would reflow the solder joints just to be sure for the channel issue. Might be something faulty driving the tube. It's been a while but I recall transistors inside...did one get too much heat on install?


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## Mr Rick

guppysb said:


> Quote:
> Thanks for the reply Rick!
> 
> I had swapped the tubes and it didn't make a difference. I originally thought the issue was with my 1/8" output jack and so I de-soldered it and replaced it with a new one. Now, not only do I have the same issues as before (can't really hear left channel), there is also a loud buzzing on the right channel. The buzzing gets louder as I increase the volume. I inspected all the solder joints to make sure there was enough solder and there weren't any solder bridges. Checked for continuity with my DMM. I guess I'll just try to resolder the shifty looking joints tomorrow.


 
 Yes, take a break. Tomorrow the problem might just jump out at you. It's worked for me.


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## guppysb

Quote:


wotts said:


> As for the buzzing, did you install the jack with the updated instructions on Pete's website? I think there are resistors added to the rear legs of the jack. I'd have to look to be sure.
> 
> I would reflow the solder joints just to be sure for the channel issue. Might be something faulty driving the tube. It's been a while but I recall transistors inside...did one get too much heat on install?


 
 Hey Wotts,
  
 I didn't do the resistor mod described on Pete's website. I ordered a chassis 4 inches wider than the one he used, and spaced apart the output transformers from the main power transformer. I could try to do the mod tomorrow and see where it gets me. I wonder if I can remove the 2 10 ohm resistors from R22 and R23 and use it for the mod. Although, he mentioned that 220 ohms was used in the mod.


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## wotts

The other thing that comes to mind is a ground loop. I'll have to crack mine open and take a look. Or maybe I have pictures...I'll look and get back to you.


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## guppysb

Thanks Wotts! I have a hammond aluminum chassis. I know one of the pcb mounting holes is meant to be grounded. I have my pcb mounted to the chassis with washers and bolts on all the mounting holes. Doing a continuity test, all the mounting holes go back to ac ground.
 What is worrysome is that the 1/4" also has quite a few ground connections, along with the 1/8" jacks, and also the switches. I know this is going to sound stupid, but was I not supposed to solder all the holes for the switches/jacks/pot? I assumed I was since it looked like Pete made it so a standard item could fit in there.
  
 I guess tomorrow will be filled with soldering/desoldering/looking at the schematic to see where I went wrong. I'll post some pics of my PCB tomorrow and maybe you guys can point out where I messed up. Thanks again for the replies guys, good to know I am not alone here and out $350.


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## guppysb

*Update #2:*
  
 Hey Guys,
  
 I have some good news! The amp is working 100% when I select the input to be the front 1/8" jack. However, when I select the rear inputs, I have the same problem as before, where the right channel is fine but the left channel you can barely hear. I had 2 327 ohm resistors lying around, and so I did the hum mod listed on Pete's website. That seems to have gotten rid of the noise/buzzing/hum. Also, shorting JP1 seems to have almost no effect for me, so I removed the jumper.
  
 If anyone has any idea how to fix the left channel problem for the rca inputs, I am all ears (yes, pun intended)! You guys have been great so far, thanks for all the help!


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## Mr Rick

guppysb said:


> *Update #2:*
> 
> Hey Guys,
> 
> ...


 
 Well that is good news. At least now you know the amplifier itself is working correctly. If you had an oscilloscope you could signal trace that pesky left channel input and see just where the signal disappears. Somehow the signal is getting lost before it ever gets to the amplifier section. There can't be a whole lot to look at, but not having a schematic I really can't suggest what to look for. A cold soldered  connection. A wrong value resistor in the signal path. A reversed capacitor. Or something as simple as the shield of a cable shorting to the center conductor.
  
 Good luck.


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## guppysb

*Update #3:*
  
 Hey Rick, as always thank you so much for the quick replies. Too bad you're in SoCal, I'd buy you a few drinks if you were in the Bay Area!
  
 So I took everything apart and applied a bit more solder to shifty looking joints. Then I went through every single part to make sure it was working well. It turns out that R18 and R19 were burned out. They were supposed to be 1M ohm resistors but weren't given even 1/3 of that resistance. So I just happened to have some spare resistors and put them in. Turned on the amp and both the rca and 1/8" inputs are working well!!!!!
  
 Once I get the chassis powder coated and stuff, I'll post some pictures. I am just happy that the amp is finally working well, that was like a good 14 hours of debugging lol. I don't really know if the speaker out section works yet since I have no passive speakers, but maybe in the future I'll give it a shot.


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## Mr Rick

A little celebration music.
  
 https://play.spotify.com/track/31JOjxeYaeORVmV41pqgAo


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## guppysb

mr rick said:


> A little celebration music.
> 
> https://play.spotify.com/track/31JOjxeYaeORVmV41pqgAo


 
 Very nice choice!


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## wotts

Glad to hear it worked out! I forgot to mention I had the pictures of my build on my user gallery. I was looking to see how I had it grounded. Moot point now I suppose. What speakers are you using?


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## guppysb

I am currently using Beheringer Audio Truth 3030A, which are active near fields. I need to find some cheap passive bookshelf speakers to test the speaker outs on the amp.
 What is seriously impressing me about the amp is like no harmonic distortion, what so ever. I have maxed the pot to max volume and no hissing, buzzing, humming, or anything. The sound seems good so far, although I am not that impressed by it. I guess a good amount of burn is going to be needed for the amp. I have Motorola 13EM7 tubes in there. Maybe sometime this week I'll order another pair and see how they fare.


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