[Mullet]

Hrmmmm.. I've reflowed things. Didn't find any bad soldering. Maybe this requires a 2nd look. I did notice you've had this problem as well as others. Seems the EHHA's design is prone to this because of it being DC coupled. Hence the reason for the servo.
 
I did find this...
 
Quote:

  Here's how I would have go about troubleshooting.
 
1) Look for any shorts
 
2) Double check all components.
 
3) Check the BJTs using the BJT sanity tutorial an amb forums :
http://www.amb.org/forum/howto-bjt-sanity-check-t59.html
If there is some confusion , compare the results with the other working board.
 
4) Check & compare the resistances of output mosfets
 
Replace the faulty devices and see if you can get it working.

 
I know this is basic stuff and I should know most of this by now. But I just want to be sure I'm doing it right. I'd hate to create more damage than what is done.
 
1. Checking for shorts. Best way to do this...
 
2. Double checking components... I'm assuming this means one has put the parts in the their proper place.
 
3. Check BJTs... I'll use the recommended site.
 
4. What resistance should I expect for output mosfets? And at what points should I check?
 
I think I'll have to uncase this puppy to get a better angle on what is happening. I suppose I can use the good board to help.

 

[Mullet]

Gosh this thread is dead.
 
So I've finally gotten things sorted out and it's quite perplexing. I've re-flowed joints on the amp section of the bad board and used generous amounts of flux this time. I didn't change the wiring layout, so that didn't change. I did re-tighten the terminals due to removing the board for re-flowing. In any event, now things are working. I'm getting a maximum of 3mV offset on the bad board and around 1mV on the good board. There was a slight buzz, even with the pot totally turned down. I changed the power cable and have plugged it directly into my wall outlet and not the power strip I'm using. Now the buzz has gone away.
 
How does this amp sound?
 
Fantastic!
 
It feels like all of my headphones are now totally driven with authority. There seems to be more width in sound stage compared to my other Cavalli DIY amp - the Compact Tube Hybrid. I guess you could say it's less congested. With more listening time and comparison to my other amps I'll be able to fully grasp what it does and doesn't do.
 
On to my next project... the journey begins...

 

[muskyhuntr]

Congratulations on your build!!!  Looking forward to seeing some pictures.  Good luck on your next build!
 
Me

 

[Klechty]

  Gosh this thread is dead.
 
So I've finally gotten things sorted out and it's quite perplexing. I've re-flowed joints on the amp section of the bad board and used generous amounts of flux this time. I didn't change the wiring layout, so that didn't change. I did re-tighten the terminals due to removing the board for re-flowing. In any event, now things are working. I'm getting a maximum of 3mV offset on the bad board and around 1mV on the good board. There was a slight buzz, even with the pot totally turned down. I changed the power cable and have plugged it directly into my wall outlet and not the power strip I'm using. Now the buzz has gone away.
 
How does this amp sound?
 
Fantastic!
 
It feels like all of my headphones are now totally driven with authority. There seems to be more width in sound stage compared to my other Cavalli DIY amp - the Compact Tube Hybrid. I guess you could say it's less congested. With more listening time and comparison to my other amps I'll be able to fully grasp what it does and doesn't do.
 
On to my next project... the journey begins...

sorry for the late answer.
May be you get a faulty pcb.
I'm working on a pcb without this annoying noise, i will post somme pictures when i receive it.

 

[Mullet]

Yeah, the noise thing is weird. It had gone away and now it's back with a vengeance. I don't think it's my input wiring (RCAs). I'm using belden cable for the wire, which includes three wires - black, red, and gnd. I usually cut either black or red and keep the gnd. Then I wire both the gnd and either black or red depending on left or right channel. Both go to my pot inputs. I'm using the AMB RK27 board with an RK27. I've tried isolating the RCA jacks using those fancy Rean RCAs. I'm pretty certain they are isolated from the chassis. Or at least I think so. Anyway to tell for sure?
 
I'm thinking my star ground wiring is correct. I'm using the alternate wiring instead of the primary wiring on Alex's site. The only things that I can think of that relate to noise would be my transformers being too close. Can I just use copper foil to shield them?
 
I'll probably take everything apart and start with different star ground wiring to see if that helps. I actually have a ground loop breaker in the mix, but it doesn't seem to have an effect to removing hum.
 
I have some pix that I'll upload in a few hours.

 

[Klechty]

  Yeah, the noise thing is weird. It had gone away and now it's back with a vengeance. I don't think it's my input wiring (RCAs). I'm using belden cable for the wire, which includes three wires - black, red, and gnd. I usually cut either black or red and keep the gnd. Then I wire both the gnd and either black or red depending on left or right channel. Both go to my pot inputs. I'm using the AMB RK27 board with an RK27. I've tried isolating the RCA jacks using those fancy Rean RCAs. I'm pretty certain they are isolated from the chassis. Or at least I think so. Anyway to tell for sure?
 
I'm thinking my star ground wiring is correct. I'm using the alternate wiring instead of the primary wiring on Alex's site. The only things that I can think of that relate to noise would be my transformers being too close. Can I just use copper foil to shield them?
 
I'll probably take everything apart and start with different star ground wiring to see if that helps. I actually have a ground loop breaker in the mix, but it doesn't seem to have an effect to removing hum.
 
I have some pix that I'll upload in a few hours.

Yes you can cover the transformer with a copper foil. Don't forget to put the foil to the ground.
The problem with the ehha is the number of cables that float around.
This the reason why i did my own pcb.

 

[stixx]

I am selling my unfinished EHHA RevA --> boards all populated and fully working
(had it playing on the breadboard for months).
Standard psu exchanged with a pair of Salas shunt regs. For details look here:
 
http://www.head-fi.org/t/763448/fs-ehha-rev-a-boards-with-salas-shunt-regs-and-transformers

 

[luxodesign]

Hello all! I am here to ask for a bit of help. A good friend of mine has been looking at some of the DIY amp projects and asked for my help to assemble a kit. I agreed, I know my way around soldering boards and assembling arduino components and was happy to help. So he ended up purchasing the EHHA Rev A kit from GlassJar which I received last week and it looks great, very expertly assembled kit.
 
The problem is I am in way over my head, I can read a basic schematic and I can do a clean solder job. I can NOT assemble this kit with a 100% certainty that I am not going to do something which will affect the quality of the sound. 
 
If anyone out there could help me out with assembling this thing I can offer my services with CNC, laser cutting/engraving or even water-jet cutting. My company provides custom fab services and I was initially going to make him a case out of walnut to match his headphone stand specifically designed for whatever amp he chose.  In fact, I would be happy to trade some custom case work if anyone is interested. (I'm in California)
 
I realize no one has been on this thread for months and the interest in the Rev A seems to have waned a bit, we are really keen to hear a true tube amp though so I'm hoping for the best!

 

[stixx]

You have the kit, you do know how to do a clean solder job, you probably have the tools... that's a good way to start.
 
You don't necessarily have to be able to read the schematics when stuffing the boards... follow the BOM and the designations
on the boards, CAREFULLY check which part goes where, carefully check orientation / polarity and, most of all, take your time!
 
Start populating the heater and psu boards first since they are really easy and good practice to get aquainted with he EHHA.
Then do the amplifier boards. As said take your time since desoldering parts on the amplifier boards will not be easy and unneccessary 
when you do it right from the beginning.
 
When you have achieved this come back here and ask for advice on how to wire everything up... there are diagrams etc., and
probably good advice from one or the other visitor here... 

 
When interested I can send you all the information I have on my computer about the EHHA RevA, PM me with an email adress!

 

[Mullet]

Also, I'd say to try and read the whole thread. There is a wealth of info that should help in getting it done. It's not a super hard project. The wiring is the most frustrating part I'd say. Looking back, I'd say I would have preferred a single board. A lot of people report having a low level hum, including myself. If there were less wiring then maybe it wouldn't exist. Perhaps, going with that custom transformer would help. All things aside, I have to say this is a great sounding amp though. Everyone that hears it at meets, has good things to say like... end game amp, etc.

 

[luxodesign]

Thanks for all the encouragement, I got the BOM from my buddy and can now see more clearly the correlation between it and the boards, this is going to be easier than I thought. That is to say, I thought is was almost impossible and now I think if I take my time I can get it done in a week or so
 
I have read through the thread and found some good stuff starting at page 30, but it still freaked me out pretty well.  I will try to post some pics as I go, I'll start on the heaters and work my way in.  
 
Again, thanks for the responses, it's been a big help and we appreciate it.

 

[luxodesign]

Alright, I have some time this weekend and I'm hoping to knock out the boards. I am making some assumptions and I'd like some feedback if you all have time, I have not worked with some of these types of components before.
 
So this the first heater board, I'm not going to do the second until I hear back (and I need some parts from mouser, dropped a resistor and subsequently crushed it with another project)
 
I assumed the anode leg on the rectifiers was to be facing up, can you confirm? 
 
On to the next boards, I am warming to the task and am now very excited to hear this amp. My buddy has some sort of crowdsourced headphones that I listened to and it was just fantastic even on his solid state. I got lazy years ago and traded the convenience of digital for a lot of sound quality, this project has really reminded me of I've been missing.
 
Thanks again for all your help,
 
 
OK, so I guess I can't upload a picture as I lack the necessary permissions.  I'll see if I can't get that fixed, would really like to post them as I go,

 

[Klechty]

Dude,
 
i encourage you to read that.
 
https://www.cavalliaudio.com/diy/ehhaa/main.php?page=boards

 

[luxodesign]

Yeah, that was the first place I went, I spent about a week researching this thread and other places online. As I said earlier I have only a very basic understanding of schematics and while the BOM may call out the right piece, I don't always know what that piece looks like. I am also very concerned about getting some of the polarities wrong and I've been using a multimeter to feel my way through the resistors so I don't mess that up.
 
All in all I'm getting most of the board done, I'm going to do one channel first, trouble shoot it and then start the next set. I've ordered a spare board from GlassJar so that if I do screw anything up too badly it's an easy fix.  
 
Really wish I could post pics of my progress, still working on that bit.
 
Thanks again for all the support, I am hoping to finish at least the one channel this weekend,

 

[luxodesign]

OK, so I have one channel mostly done, I just need to confirm my resistors from GlassJar (they were larger than the PCB and I'd have to solder them in at a weird angle).  I am going to get some confirmation on all that and then I'll be ready to go.
 
Many thanks again to Stixx for sending me some wiring diagrams, I'm going to have a go at it this week, maybe over Thanksgiving weekend if I have time.
 
Apparently I have to post 40+ messages or so before I'm allowed to post any pics of my build. I am very tempted to to just post 36 additional posts but I have a feeling the Mods That Be will not look kindly on that (seriously, just joking, please don't boot me!)
 
Anyone have trouble pushing in the tubes? I am a little nervous that I've done something wrong on the solder side (I even broke out the ol' 60/40 for the socket so I hope not) as when I went to fit the tubes to send a pic to my buddy they seemed extremely tight and I was worried I'd break something so I just stopped. I'll wait until I'm totally ready to go before I load up the tubes and chip.
 
-luxo