or Connect
Head-Fi.org › Forums › Misc.-Category Forums › DIY (Do-It-Yourself) Discussions › SOHA II Builders Thread
New Posts  All Forums:Forum Nav:

SOHA II Builders Thread - Page 74

post #1096 of 1686
Thread Starter 
Pin 7 is the V+. It should be at 12V. Can you track this down?
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 #1097 of 1686
Pin
1 11.72V
2 0V
3 0V
4 -12.04V
5 0V
6 0V
7 11.96V
8 11.72V

I edited my post these are the correct voltages
post #1098 of 1686
Thread Starter 
The output of the opamp is correct at 0V. What is the voltage at the collector of the MPSA14?
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 #1099 of 1686
Quote:
Originally Posted by runeight View Post
The output of the opamp is correct at 0V. What is the voltage at the collector of the MPSA14?
0V
post #1100 of 1686
Thread Starter 
OK. So if the collector is at 0V and the + of the relay is at 12V and if the - of the relay is connected to the collector then the relay has to be latched. But it's not??

Maybe check the continuity across the relay?? And solder joints? Etc.
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 #1101 of 1686
No the relay is getting no power
post #1102 of 1686
Thread Starter 
I guess you've measured across the relay coil and it shows 0V? But the + rail is 12V and the collector is 0V??

If this is true then there has to be a discontinuity somewhere. A bad solder joint at the relay coil?
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 #1103 of 1686
Quote:
Originally Posted by runeight View Post
I guess you've measured across the relay coil and it shows 0V? But the + rail is 12V and the collector is 0V??

If this is true then there has to be a discontinuity somewhere. A bad solder joint at the relay coil?

I was having trouble getting the proble on the coil, it is getting the 12V. The Rt channel is latching but not the left and I noticed that the left side got hit with my solder iron during construction, so I believe I have a bad relay.

Thanks for helping me track this down and I have a better understanding of how the E12 circuit works.
post #1104 of 1686
Thread Starter 
You're welcome. Hope we found the problem.
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 #1105 of 1686
Yes the new relay is working great.

But I am having another issue. TP+R dials to 60V just fine but TP+L is stuck around 10V, fickin C15P is in backwards (reversed polarity). Do you think I should replace Q2P when I have the board out or should it have held up to my stupidity
post #1106 of 1686
Bigger problem now, reversed C15P to correct polarity.


Got 60V on both sides. Plugged in the 5963 tubes set for 12.6V. Set the tail current to 400mV across R6. Went back to check TB+L/R and it dropped to 27V, thats all I can get out of it. Checked TB+ still a solid +120V. Tried running with just one tube or the other and can get the right voltage.

Turned out one of the RCA5963 tubes was bad, glad I bought three. Just wanted to share this info in case anyone else loses plate voltage when they plug in the tubes and set the tail current.


Will be plugging in the RCA inputs and headphones tonight, got my fingers crossed!
post #1107 of 1686
Thread Starter 
So you're finally going to hear music tonight??

I hope you like the amp.
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 #1108 of 1686
Quote:
Originally Posted by runeight View Post
So you're finally going to hear music tonight??

I hope you like the amp.
yes great sound! beats the old Soha + Jisbos contraption by miles. Really glad you used the jumpers to bring everything up in stages I think this is essential when mixing HV tubes with LV SS.

Couple questions:

My tubes are off about 1V at the plate when set to the same current, which is more important to equal the gain, the current or the plate V?

I am amazed at the sound of the 12AU7 with only 1.25mA. But is there any opportunity to push more current thru the tube by lowering the resistance of R6 ?
post #1109 of 1686
I finished my case prototype of the SOHA-DAC combo. I know the cutting and wiring is shameful, but they are work well now. Next step is to find some good board and redo the wire.

There are two LED that indicate the source is coaxial-DAC or RCA line in. Now source is DAC.


On the top the metal net is a piece of officedepot's card holder.



The red board is the DAC, DIR9001+PCM1793. I got it from ebay. It used 12DC single rail input, and splited it into +-6V and virtual ground by LM1875. I removed the LM1875, and made a DC source on the yellow board, +-9V to the OPAMP, +6V to DAC, -6V for source switching and LED. Since the OPAMP is using the seperated DC source from DAC, I put the OPAMP, decoupling cap into another board. The opamp board is connected to the socket with pins. The two relays are for coaxial or RCA switching, and LED controling.
post #1110 of 1686
Has anyone found a source for a grommet that fits the holes in the top for the tubes?
New Posts  All Forums:Forum Nav:
  Return Home
Head-Fi.org › Forums › Misc.-Category Forums › DIY (Do-It-Yourself) Discussions › SOHA II Builders Thread