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SOHA II Builders Thread - Page 78

post #1156 of 1686
Quote:
Originally Posted by jmf View Post
I also have RCA 6922 and RSD ECC82. What are the jumpers for those tubes ? Do I need to modify the different pot/currents on the board ?

JM
6922 = 6.3V
ECC82= 12.6 V

This amp really shines with expensive tubes try Amperex 8416, Amperex 6DJ8, or Amperex 12AU7. Also see my post on the Soha tube thread that shows how to get 5.5mA of tail current which really makes this amp shine.

Good Luck.
post #1157 of 1686
Thread Starter 
Quote:
Originally Posted by czegevara View Post
Im not sure if it was in this thread but guys from polish forum Audiostereo.pl are now working on Soha MKIV clone. Here is link for forum thread: SOHA CLONE MK III - projekt PCB - Do It Yourself - Forum Audio - Audiostereo.pl
and links for MKIII schematics and pcb with some changes to original project:
http://tan.lcf.pl/klon_soha_II/klon_soha2_2.6.2_sch.pdf
http://tan.lcf.pl/klon_soha_II/klon_....2_mozaika.pdf
http://tan.lcf.pl/klon_soha_II/klon_soha2_2.6.2_top.pdf
http://tan.lcf.pl/klon_soha_II/klon_...2.6.2_elem.pdf
We all here in Poland want to thank Alex Cavalli for such a great design!
Peter.
You're welcome. Do you have any amps built yet?

Nice to see that the amp has a dedicated following in Poland. I see that you have made some mods. Would you mind making another post or two telling us what you are adding or changing?

I'd certainly like to know.
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 #1158 of 1686
Does anyone know the output impedance of this amp? It seems to synergize well with Grados and I'm wondering if a low output impedance has something to do with it.
post #1159 of 1686
Thread Starter 
Zo should be about 1.5R.
Dr. Cavalli gained notoriety with his first DIY amplifier projects. His success has blossomed into Cavalli Audio, a world leader in amplifier design.
Reply
post #1160 of 1686
Quote:
Originally Posted by czegevara View Post
Im not sure if it was in this thread but guys from polish forum Audiostereo.pl are now working on Soha MKIV clone. Here is link for forum thread: SOHA CLONE MK III - projekt PCB - Do It Yourself - Forum Audio - Audiostereo.pl
and links for MKIII schematics and pcb with some changes to original project:
http://tan.lcf.pl/klon_soha_II/klon_soha2_2.6.2_sch.pdf
http://tan.lcf.pl/klon_soha_II/klon_....2_mozaika.pdf
http://tan.lcf.pl/klon_soha_II/klon_soha2_2.6.2_top.pdf
http://tan.lcf.pl/klon_soha_II/klon_...2.6.2_elem.pdf
We all here in Poland want to thank Alex Cavalli for such a great design!
Peter.
Here's a link to the Google translated version:
SOHA CLONE MK III - projekt PCB - Do It Yourself - Forum Audio - Audiostereo.pl
post #1161 of 1686
What is acceptable for the drop between TB+ and TP for R/L? Above 19v drop?

I bought my SOHA II here a while ago, went to change tubes, I am getting 15v on both tubes. Changed tubes to the ones that came with it, tested 16v. Did all the other tests before this, everything was in pretty good shape, the worst regulator was off by .2v.

Adjust the tail current (set to 2ma)? Leave it alone? I've been listening to the amp for quite a while before I took these measurements.

Also, my DT880s are pretty quiet but my more sensitive HD25's have a pretty audible noise floor. Is there anything I can do to fix this? It is independent of the pot, which is grounded.

EDIT: After moving them in and out and switching them and whatnot, one tube is dropping 19v, the other is 15v still - they are ebay tubes, what are the implications of this? Also, when I keep testing these, the relay keeps tripping - is that normal?
post #1162 of 1686
Quote:
Originally Posted by DoomzDayz View Post
What is acceptable for the drop between TB+ and TP for R/L? Above 19v drop?

I bought my SOHA II here a while ago, went to change tubes, I am getting 15v on both tubes. Changed tubes to the ones that came with it, tested 16v. Did all the other tests before this, everything was in pretty good shape, the worst regulator was off by .2v.

Adjust the tail current (set to 2ma)? Leave it alone? I've been listening to the amp for quite a while before I took these measurements.

Also, my DT880s are pretty quiet but my more sensitive HD25's have a pretty audible noise floor. Is there anything I can do to fix this? It is independent of the pot, which is grounded.

EDIT: After moving them in and out and switching them and whatnot, one tube is dropping 19v, the other is 15v still - they are ebay tubes, what are the implications of this? Also, when I keep testing these, the relay keeps tripping - is that normal?

The tubes are struggling to make the tail current at a plat voltage that is in range. Get some new ones.
post #1163 of 1686
Hey all, For bleeding the caps, what power rating did you guys use for the 10K resistor? All I have is 1/4Watt's kicking around my parts bin - I'm guessing I'll need more than that.
post #1164 of 1686
Quote:
Originally Posted by pixeljedi View Post
Hey all, For bleeding the caps, what power rating did you guys use for the 10K resistor? All I have is 1/4Watt's kicking around my parts bin - I'm guessing I'll need more than that.
100V/10k= 10 ma 10 ma*100V= 1W, so 2W would be safest
post #1165 of 1686
Quote:
Originally Posted by regal View Post
100V/10k= 10 ma 10 ma*100V= 1W, so 2W would be safest
thanks!
post #1166 of 1686
Quote:
Originally Posted by regal View Post
6922 = 6.3V
ECC82= 12.6 V

This amp really shines with expensive tubes try Amperex 8416, Amperex 6DJ8, or Amperex 12AU7. Also see my post on the Soha tube thread that shows how to get 5.5mA of tail current which really makes this amp shine.

Good Luck.
regal

My SOHA II is shining brightly with Mullard CV4003 "boxplate" tubes, but the higher current mod you mention sounds interesting. Could you please point me in the direction of the above mentioned post?

Thanks.
post #1167 of 1686
post #1168 of 1686
My Mullards responded nicely to the additional current.
post #1169 of 1686
Quote:
Originally Posted by DoomzDayz View Post
I have a similar hum, only with lower impedance higher sensitivity phones that does not change with respect to the volume knob and am looking for advice as well.


http://www.head-fi.org/forums/6171572-post50.html
Did you find a solution? I am curious as I have a similiar problem with a similar amp. A hum that doesn't change with the volume knob would indicate interferance after the tubes IMO? Anyone else have any ideas?
post #1170 of 1686
Hi everyone, I got a simple questions for you guys, is the SOHA II that hard of a build for a beginner DIYer ? Should I start with something like a standalone 2-channel JISBOS to get some soldering/troubleshooting skills ?! ( I'm a student in electronics )
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