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SOHA II Builders Thread - Page 22

post #316 of 1686
Thread Starter 
Another small FWIW m0b1liz3 IIRC the kit comes with the transformer and the hammond case (the large one). So you won't have to buy these separately.
Dr. Cavalli gained notoriety with his first DIY amplifier projects. His success has blossomed into Cavalli Audio, a world leader in amplifier design.
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post #317 of 1686
More testing is underway...









Test Values:

TL+ 15V
TL- -15.2V
TH -12.5V
TB+ 111V

O/P Quiescent Current ~100mA

TB+L/R ~65V

Tail Current 2mA

TPL/TPR ~60V

For some reason, I'm not getting ~40V at TPL/TPR. When I measure the plate voltage at the socket I get Pin 1 on both ~40V but Pin 6 ~60V, so something isn't splitting the voltage between the plates?

*Edit* the only things not connected are the pot, and inputs. Also the E12 relay continues to click once powered. It's fairly sporadic... This is with tubes installed, EH 12AU7A
post #318 of 1686
just curious, why would you expect things to work without the pot installed?
post #319 of 1686
Quote:
Originally Posted by luvdunhill View Post
just curious, why would you expect things to work without the pot installed?
I didn't expect the pot to make a difference at this point... if it's as simple as that than I'm relieved. But I don't want to solder it in and then things still won;t work. I thought, maybe Q1 or Q2 got damaged and are not "mirroring/splitting" the current thru the triodes, thus allowing full B+ voltage to the second plate.
post #320 of 1686
Thread Starter 
bmw the pot needs to be installed for the input stage to bias properly. I should probably say this on the website.
Dr. Cavalli gained notoriety with his first DIY amplifier projects. His success has blossomed into Cavalli Audio, a world leader in amplifier design.
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post #321 of 1686
bmw, if you have an Alps RK27 volumepot on hand, follow runeight instructions.

In case you don’t have a volumepot on hand yet, you can temporarily shorted the input and go further with the initial setup. From the PCB top view, connect a lead (resistor snip) between the right and the middle solder point of the Alps RK27 volumepot. Do this for both channels of course. Hope your amp up and running soon.
post #322 of 1686
My kit is on its way...hope you guys are prepared for all the questions I'll have once it arrives
post #323 of 1686
Quote:
Originally Posted by runeight View Post
bmw the pot needs to be installed for the input stage to bias properly. I should probably say this on the website.
Awesome, I have one on hand I just didn't want to put it to waste if it didn't work.
post #324 of 1686
Thread Starter 
Quote:
Originally Posted by DrkRipper View Post
My kit is on its way...hope you guys are prepared for all the questions I'll have once it arrives
We're ready.
Dr. Cavalli gained notoriety with his first DIY amplifier projects. His success has blossomed into Cavalli Audio, a world leader in amplifier design.
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post #325 of 1686
What a relief, got my SOHA II up and running Everything checks out good and I'm running 90V B+ along with EH 12AU7's for the time being. So far the setup has great synergy with my HD580's, but as the amp continues to burn-in time will tell. I'm truly impressed by the sound and can't wait to start rolling in some tubes, next up hopefully will be some Russian 6N1P-EB's.

I just like to say I have a SOHA II tube thread, that hopefully users can populate with their impressions & opinions.

My "test" setup and test headphones:




^^^Listening to a little Pink Floyd
post #326 of 1686
Congratulations, nice build! What have you finally used for C1L/R? They seem soldered below the PCB.

My kit was shipped by Jeff last tuesday, I'm eager to get and start it. I've also ordered .22uF Jupiter caps (C1L/R) and NOS Sylvania JAN 12AU7 tubes from Parts Connexions. I'm a total tube newbie, I wish they will sound OK with my RS-1.

BTW do tubes will benefit from matching in the SOHAII design?
post #327 of 1686
Quote:
Originally Posted by wolf18t View Post
Congratulations, nice build! What have you finally used for C1L/R? They seem soldered below the PCB.

My kit was shipped by Jeff last tuesday, I'm eager to get and start it. I've also ordered .22uF Jupiter caps (C1L/R) and NOS Sylvania JAN 12AU7 tubes from Parts Connexions. I'm a total tube newbie, I wish they will sound OK with my RS-1.

BTW do tubes will benefit from matching in the SOHAII design?
I have C1L/R mounted under the board yes, they're VitQ's .22uF. I wouldn't run Jupiter caps, since this amp runs pretty hot and those beeswax covered PIO caps definitely wont tolerate the heat, maybe I'm wrong but double check with runeight and others.

From my understanding how "sellers" typically match tubes is no where near the operating conditions typical in most amps... so I think its fairly useless. If its free then go for it.
post #328 of 1686
Quote:
Originally Posted by bmwpowere36m3 View Post
What a relief, got my SOHA II up and running Everything checks out good and I'm running 90V B+ along with EH 12AU7's for the time being. So far the setup has great synergy with my HD580's, but as the amp continues to burn-in time will tell. I'm truly impressed by the sound and can't wait to start rolling in some tubes, next up hopefully will be some Russian 6N1P-EB's.

Listening to a little Pink Floyd
Good to know that your amp is up and running smoothly.
Enjoy!
post #329 of 1686
Thread Starter 
Congrats bmw. Looking foward to your case up now and your listening impressions. I assume the build was straightforward with no problems?

wolf18t, tube matching is not necessary as the SOHA II can handle most typical mismatches. However, tubes that have really bad mismatches may not work and you will simply hear this as some form of clipping or audio distortion. So far, no one has reported a tube that has failed in this way.
Dr. Cavalli gained notoriety with his first DIY amplifier projects. His success has blossomed into Cavalli Audio, a world leader in amplifier design.
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post #330 of 1686
Finally!

My SOHAII is making music It's fitted with a pair of 13D5A tubes which I wasn't sure would work.. it's not one that appears on most of the equivalents lists but the guy who sold them to me assured me they were ECC82 equivalents and it seems like he was right

My only concern at this point, is the voltage drop between TB+ and TP is only around 13V. Should I be worried about this? I'm getting 400mV across R6 on both channels.

Not had any chance to do serious listening yet, but I hope to spend a hour or two tonight enjoying the new amp.
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