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post #1591 of 1688

Hi Veiko,


Thanks for the reply. It was indeed a weak solder joint.


Onto the next round of tests ;)

post #1592 of 1688

I actually finished putting together the parts. I used quite a bit of Elna Silmic II, it is obvious that the board weren't designed to use largish capacitors and it looked a bit hilarious to me.



Unfortunately, when I reach the last initialisation step I have a problem. I can not get get a 19V drop between TB+ and TP on both side. think I recalled getting about 19V on one of the channel at first, but later on all I have is 0.2V. Did I blow the top CCS? If so why?


Btw, this is with the mod performed here with a lower R4 and R6:



Edited by Navyblue - 4/30/12 at 11:31pm
post #1593 of 1688

Wow, this amp sounds pretty damn sweet.


Thanks so much to Alex and everyone else who helped along the way.

post #1594 of 1688
Originally Posted by Navyblue View Post

What do you mean by you desoldered the RCA jacks? I assume you are talking about the input RCA jacks?


You are probably right that nobody is reading this. biggrin.gif Sadly most of these DIY design seems quickly forgotten. From what I see only the very affordable ones (like CMOY) or the very high end ones remains popular.


I was trying to spot the difference between the BOM from Jeff and the one on the website. So far I spotted one difference, I am not sure how significant though. For C6L/R it is "Metalized Polyester/Polypropylene Film Capacitor 1μ 63V" on the website and "Boxed Metal Film Capacitors 63V 1.0μf 5%" on the Jeff's BOM. Does it matter to use "boxed metal film capacitor" over the Wima I have, which is a metalised polypropylene capacitor? It is interesting that on Jeff's Excel sheet it is listed separately from C2L/R, which are the same value as C6L/R but is a metalised polypropylene capacitor (Wima).


Edit: In Jeff's Excel sheet, the C6L/R Mouser part number links to a polyester film capacitor, which from what I understand, are similar (if not slightly inferior) to polypropylene film capacitor. I wonder why Jeff do this?

Heh, funny you should mention "nobody is reading this".  I've been contemplating getting a SOHA II board from Jeff, but I really need another project like another hole in the head..


Do you have a Mouser Part list saved you could share?  And do you have a total BOM cost from Mouser?

post #1595 of 1688
Originally Posted by MrSlim View Post

Heh, funny you should mention "nobody is reading this".  I've been contemplating getting a SOHA II board from Jeff, but I really need another project like another hole in the head..


Do you have a Mouser Part list saved you could share?  And do you have a total BOM cost from Mouser?


Jeff will send you the correct Mouser part list when you order the board. I tried to PM it to you but looks like it's not allowed.

I believe SOHA II can be built for around $200, someone correct me if I'm wrong.

post #1596 of 1688


Weird, I just got a PM from someone else last week.. 

post #1597 of 1688

I am supposed to get at least 19V voltage drop between the power supply and the plate.


On one channel, I got about 27V of voltage drop, which is fine.


On another channel, I got about 1V. And of course that channel isn't working.


I swapped the tubes around, same thing. What is wrong here? Is any transistor toast? Or is there a bad joint somewhere? (although there isn't as far as I could tell)


Thanks. smily_headphones1.gif

post #1598 of 1688

Hey Navyblue,


Just want to make sure I'm reading that right. So when you swap tubes you're still getting 1V from the non-working channel?


What I would do, is measure the voltage from each of the tube pins on the non-working channel and compare with the working channel. Then trace back along the path(s) that is not giving the correct voltage(s). The good thing is, you do have a working channel to compare voltages :) And yes, definitely check for bad welds. For my issue above, I just had to reheat a weld and my issue was solved.


Hope that helps.

post #1599 of 1688


Could you post some voltages? (tube pins, etc)

Or just do what pixeljedi said.

post #1600 of 1688

Did anyone by any chance download my test results, post #1586?

I'd be grateful if someone could send the file to me. I lost it myself.

post #1601 of 1688
Thanks guys, I thought no one is reading this. biggrin.gif

I managed to trace the problem, it was some bad solder joint.

Btw, how did you guys do in the hum/buzz department? With my headphones it is pretty much silent, but I don't use any high sensitivity headphone at home. However if I use it as pre amp, I can hear some hum and hiss if I put my ear on the speaker. Of course it is inaudible at reasonable listening position.
post #1602 of 1688

Nice to hear you got it working too.

If it works for you, don't touch it :D that's my rule anyways.

Good tubes usually cause less noise. What are yours?


As I wrote before, my hum levels are theoretically non-existent: 0.2% (600ohm load). What is your sound source?

In real life, I blame my PC's cheap PSU for all of my hum and noise. Could also be the refrigerator in the next room, who knows. Very irritating.

Anyways, I get zero noise at full output from most other sources.


I'll have to build a DAC with an optical input to be able to listen through my computer again.

post #1603 of 1688

Glad you got yours working Navyblue.


I haven't noticed any noise in mine, using electro-harmonix 12AU7 tubes. I split the power off into it's own enclosure because I've integrated a Gamma2 in the signal housing for the signal processing (running optical from my laptop). Sounds pretty damn amazing.

post #1604 of 1688
I am using RCA clear top 12AU7A. Source is mainly Rega DAC through optical. Both the source and amp are behind power filter too.

Any of you did the 300mA heater mod? This allows you to use more tubes, including the 12BH7 which some people swear by over any 12AU7 including the exotic ones.

That said regarding the hum and hiss, my case is still open up top (still waiting for my sheet metal punch for the tube holes). And my PCB standoffs are 80mm tall, so shielding is near non existent.

I like the sound so far, and I haven't touched my Beta 22 since it is operational. I think it isn't done burning in yet, yesterday I just notice some really low bass coming out after feeding input at max volume for a few hours.
post #1605 of 1688

I'm running the heater mod in mine. Yeah, I tried those rca clear tops, and they sounded a bit bright for me - which was a bit rough given the price for them. I just got some new tubes today, JJ ECC802s, so far I'm blown away with what I'm hearing - really ultra clear tone.


Sucks about the hum you've got. Is everything grounded correctly (one central ground point?). A couple of years ago I had a really bad ground loop in my system - I traced it to the cable tv ground line (which is separate from the house electrical ground). I ran a copper line from that cable ground to my power conditioner's grounding lug - killed the buzz instantly. cool.gif

Edited by pixeljedi - 5/11/12 at 12:28am
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