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SOHA II Builders Thread - Page 42

post #616 of 1686
Quote:
Originally Posted by scompton View Post
I'm looking at ordering a kit and I had a couple of questions before I do. When I built my SS, I fried the mosfets when I was a little careless with the DMM probes. Can someone suggest what parts to order extras of if I'm similarly stupid while building this? I'd hate to have to wait on a Mouser order for one transistor.

I noticed towards the end of the other thread there was discussion of prepunched panels for the case. Are these available?
Alex had enough forethought to provide us with test points for most the places we take readings. If you use the DIP sockets at these points, it's extremely easy to test voltages without the probes slipping. In theory, you could even solder leads to each of these points, then attach alligator clips to the ends. Now way your DMM probe will mess anything up that way!

I finished my build recently and did LOTS and LOTS of readings because I was trying to troubleshoot a problem (reversed diode). I didn't fry any components at all. I think you will be fine. The MHSS is a nice amp, but this one is much nicer from both the builder standpoint and, more importantly, the listener standpoint

One tiny piece of advice. When soldering in your resistors, make sure the solder doesn't wick to far on the topside of the board. I am used to seeing the solder come all the way through to the top from using wave solder machines, so I actually made sure I had a good connection on both sides. This made attaching to some of the resistor test points more difficult. Maybe take not of which resistors you will be taking readings on and make sure there is a little extra leg on top to grab with your gripper probes.
post #617 of 1686
Quote:
Originally Posted by runeight View Post
Yes, it should do very well as a preamp. In fact, it might make a really good preamp because it can drive cables.
cool. BOM finished and will be placing my Mouser and GJA orders this weekend. i am building this for a friend and will be stuffing a gamma-1 DAC in as well for an all in one pre/HP/DAC - DIY enclosure.
post #618 of 1686
Quote:
Originally Posted by Hayduke View Post
Maybe take not of which resistors you will be taking readings on and make sure there is a little extra leg on top to grab with your gripper probes.
Seconded on that last point, if I were building another, I'd make sure that R6 on both channels had a little extra contact area to get to.

UB
post #619 of 1686
Quote:
Originally Posted by Uncle Bob View Post
Seconded on that last point, if I were building another, I'd make sure that R6 on both channels had a little extra contact area to get to.

UB
My first build actually has test jacks on the back for both sets of test points - the proto buffer test points were behind the heat syncs. The design is stable enough that's it pretty much 'set and forget' (unless you need to adjust tail current when tube rolling).

I should look at the values again and see how they are doing after six months - still sounds great so I haven't bothered to check!
post #620 of 1686
A little D'uh! update--

Some folks on this thread were helping me solve a ground loop problem that was revealed by the soha II. I was futzing with the connections recently and I realized the pot was not fully isolated from the chassis. I properly isolated it and now the ground loop is completely gone. I thought I had before, but... D'uh! and Yeah!

I built a y1 DAC and the two sound outstanding together. Thanks Alex and Ti!
post #621 of 1686
Since this thread was quiet lately, I just post some progress pictures


Casing isn't and will never be my cup of tea. But with the help of this newly acquired small bench drill, it's much easier.







Rear panel completed!
post #622 of 1686
Thread Starter 
That looks really nice. Every bit as good as the FPE panels that I had made.

Waiting now for the finished product.
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 #623 of 1686
Quote:
Originally Posted by wolf18t View Post
Since this thread was quiet lately, I just post some progress pictures


Casing isn't and will never be my cup of tea. But with the help of this newly acquired small bench drill, it's much easier.

http://images45.fotki.com/v1428/phot...CP_1561-vi.jpg

http://images46.fotki.com/v1453/phot...CP_1564-vi.jpg

http://images44.fotki.com/v1461/phot...CP_1566-vi.jpg

Rear panel completed!
Looks nice! I was about to ask how you did the nice lettering, then I spotted the transfer paper

I was pricing drill presses last week. That led to pricing mills, then CNC mills, then I got sane and closed the browser and listened to some music
post #624 of 1686
Quote:
Originally Posted by Hayduke View Post
I was pricing drill presses last week. That led to pricing mills, then CNC mills, then I got sane and closed the browser and listened to some music
LOL!

Got it a few weeks ago it was 33% off. If you stay with basic 8" or 10" drill press, it's very affordable.
post #625 of 1686
Quote:
Originally Posted by wolf18t View Post
LOL!

Got it a few weeks ago it was 33% off. If you stay with basic 8" or 10" drill press, it's very affordable.

I took the plunge and got a 10" myself this weekend, after seeing the levels of build quality I need to keep up with... Now I need to turn my attention to my last SOHA II case...
post #626 of 1686
Quote:
Originally Posted by Hayduke View Post
I was pricing drill presses last week. That led to pricing mills, then CNC mills, then I got sane and closed the browser and listened to some music
I went through the whole loop as well. My brain finally processed it and decided that buying a $600 CNC apparatus to drill a few holes was a giant overkill.

I finally decided to pick up a used drill press from Craigslist for $39. I hope it turns out to be a working one.
post #627 of 1686
Thread Starter 
Quote:
Originally Posted by tacitapproval View Post
A little D'uh! update--

Some folks on this thread were helping me solve a ground loop problem that was revealed by the soha II. I was futzing with the connections recently and I realized the pot was not fully isolated from the chassis. I properly isolated it and now the ground loop is completely gone. I thought I had before, but... D'uh! and Yeah!

I built a y1 DAC and the two sound outstanding together. Thanks Alex and Ti!
You're welcome.
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 #628 of 1686
Quote:
Originally Posted by runeight View Post
Kostalex, as you know TPR is too low. This could actually be a bad tube. That would be the first thing to change if you can.

Then you might try the tail current adjustment on the right channel again to be sure that it is right. If it is correct and if R4 is really 18k then it has to be a bad tube.

Try measuring the voltages on both leads of R4R to ground and tell us what they are.
R4 = 18.1k
voltages on R4R are 58,8v and 41,2v
voltages on R4L are 58,8v and 41,2v

He is also worried by the high temperature (90 Celsius degrees) of Q6, Q7 (both channels). So he reduced the quiescent current from 100 mA to 80 mA. Load is 30 Ohm.
post #629 of 1686
This is my first build with tubes and I'm having a bit of confusion I hope you guys can help clear up.

I have finished stuffing a Soha II board and ready to start testing but I'm a bit confused about the heater jumper. I have a pair of 5963 tubes and according to this spec sheet I found
http://scottbecker.net/tube/sheets/127/5/5963.pdf
I can run them in 12.6V series or 6.3V parallel.

The Cavalli Audio site says
"The 2 x 3 onboard header can be jumpered to select 12.6V parallel or 6.3V series operation."

What do I strap the heater at? I think I'm overlooking something obvious here as those are backward from each other and the 5963 would be unusable.
post #630 of 1686
Quote:
Originally Posted by Zippy View Post
This is my first build with tubes and I'm having a bit of confusion I hope you guys can help clear up.

I have finished stuffing a Soha II board and ready to start testing but I'm a bit confused about the heater jumper. I have a pair of 5963 tubes and according to this spec sheet I found
http://scottbecker.net/tube/sheets/127/5/5963.pdf
I can run them in 12.6V series or 6.3V parallel.

The Cavalli Audio site says
"The 2 x 3 onboard header can be jumpered to select 12.6V parallel or 6.3V series operation."

What do I strap the heater at? I think I'm overlooking something obvious here as those are backward from each other and the 5963 would be unusable.

I believe 5963s will operate at either heater voltage...


Start at 6.3v if you want to be safe...
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