[regal]

Quote:

Originally Posted by jmf /img/forum/go_quote.gif 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.

 

[runeight]

Quote:

Originally Posted by czegevara /img/forum/go_quote.gif 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.

 

[regal]

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.

 

[runeight]

Zo should be about 1.5R.

 

[pixeljedi]

Quote:

Originally Posted by czegevara /img/forum/go_quote.gif 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

 

[eruditass]

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?

 

[regal]

Quote:

Originally Posted by DoomzDayz /img/forum/go_quote.gif 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.

 

[pixeljedi]

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.

 

[regal]

Quote:

Originally Posted by pixeljedi /img/forum/go_quote.gif 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

 

[pixeljedi]

Quote:

Originally Posted by regal /img/forum/go_quote.gif 100V/10k= 10 ma 10 ma*100V= 1W, so 2W would be safest

thanks!

 

[rolotube]

Quote:

Originally Posted by regal /img/forum/go_quote.gif 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.

 

[nattonrice]

http://www.head-fi.org/forums/6228710-post75.html

 

[regal]

My Mullards responded nicely to the additional current.

 

[regal]

Quote:

Originally Posted by DoomzDayz /img/forum/go_quote.gif 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?

 

[Killercrush]

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 )