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SOHA II Builders Thread - Page 81

post #1201 of 1688
Unlike the suggested layout from the Soha II webpage, I think I'm going to mount the toroidal PT closer to the PCB so the Ac inlet and switch can mount on the far side of the rear panel - away from the audio inputs. This also make more room for the Bantam DAC

Does anyone think the Avel toroid will introduce noise/hum into the PCB if it's that close to the rear of the PCB?

Thanks.
post #1202 of 1688
Quote:
Originally Posted by tubesmuggler View Post
Does anyone think the Avel toroid will introduce noise/hum into the PCB if it's that close to the rear of the PCB?
Personally, I'd keep the thing as far away from the PCB as possible. But you could build it the way you want it (before drilling holes), test for hum, if there is, move it back and change your back panel configuration.
post #1203 of 1688
Thanks for your input pixeljedi. I think I'll do it the standard way. Then figure out a way to mount the Bantam dac or skip it. I'd rather have a 24bit dac anyway.
post #1204 of 1688
Quote:
Originally Posted by tubesmuggler View Post
Thanks for your input pixeljedi. I think I'll do it the standard way. Then figure out a way to mount the Bantam dac or skip it. I'd rather have a 24bit dac anyway.
Or you could throw the toroid in a separate enclosure and enjoy the extra room
post #1205 of 1688
Me again. I noticed the supplied RCA jacks are not the insulated type so they will be grounded at the rear panel. Is there still a need to run a ground from the RCAs to the ground lug on the input terminal strip, or can I just run the L and R channel leads up to the input terminal strip? And then ground from the PCB star to the enclosure.

Thanks guys.

Regarding the layout, I'm attempting to move the PT up to the PCB and install the bantam dac. I'll listen for hum and if it's noisy I'll move it back and start drilling the rear panel.
post #1206 of 1688
Quote:
Originally Posted by tubesmuggler View Post
Me again. I noticed the supplied RCA jacks are not the insulated type so they will be grounded at the rear panel.
I would isolate those RCAs from the chassis
post #1207 of 1688
hi guys,

I need some help troubleshooting my SOHAII


All was fine in the initial setup till the point where i am supposed to insert my tube.

The Left tube did not light up whereas the right tube light up albeit a little dim.

Both tubes were then removed and pin 4 measured 12.6V for both whereas pin 5 measured 0V. The voltages were measured with reference to ground.

A swap of tube was done and results is the same, i.e left tube did not light up. this cfms that both tube are working fine.

Tubes used were 12AU7 and in parallel mode for 12.6V

where should i proceed next for my trouble shooting?
post #1208 of 1688
I've started the intial setup procedure. The PS is fine. I've moved on and jumpered J1 and J2. Unfortunately I can't set the Buffers. I'm aiming for 220mV across R10L and R10R, but the lowest I get is 280mV. At start up they measured around 450mV...

Any idea's what to check?

TIA!!
post #1209 of 1688
Quote:
Originally Posted by tubesmuggler View Post
I've started the intial setup procedure. The PS is fine. I've moved on and jumpered J1 and J2. Unfortunately I can't set the Buffers. I'm aiming for 220mV across R10L and R10R, but the lowest I get is 280mV. At start up they measured around 450mV...

Any idea's what to check?

TIA!!

Make sure you have all the transistors properly orientated and in the right spots.
post #1210 of 1688
Alright, I got a question here.

I have around $200 USD to play with to build an amp for my HP2.

I thought about building a Soha+Jisbos amp but there's probably plenty lonely units now, left unused, maybe a deal will pop up. .

Than I thought about it, could this amount be sufficient to build a Soha II ?!!

What I want to know precisely is, the average BOM list price for both builts so I can estimate if the extra price difference would be worth it.

Happy listening
post #1211 of 1688
Hey guys. I figured out the problem. I had the R10's installed on the R12 pads and visaversa! Oooops.. That's all fixed up now and the buffers are set correctly.

Unfortunately I'm on to the next problem. The difference between TB+L and TPL is about 19V. However the TB+R and TPR is WAY off. About 45V difference. I've checked the tail current and both channels are at 2mA (400mV across R6). The TB+ is at 62V.

I have swapped the tubes around but the problem remains in the right channel. Does this mean I have a bad BC560C ?

Thanks for any direction you guys can offer!

(Geez I can't wait to listen to some music!!)
post #1212 of 1688
I've taken some more measurements:

Pin1 = 36V
Pin6 = 16V

Tail current is set and stable. The Rp is 18K as required.

What's the next step? New BC560C transistors??
post #1213 of 1688
Quote:
Originally Posted by tubesmuggler View Post
I've taken some more measurements:

Pin1 = 36V
Pin6 = 16V

Tail current is set and stable. The Rp is 18K as required.

What's the next step? New BC560C transistors??
yes
post #1214 of 1688
No dice. I've just replaced Q1 and Q2 and the results remain unchanged.
Voltage measured across R2 is 300mV, across R3 is 330mV. I believe it should be 220mV and 230mV or so.
post #1215 of 1688
Got it! The ZN Mcap was damaged/shorted out. I removed that and everything was pretty much good.

Unfortunately that leaves me with crappy Solens because I can't get anything else to fit. The Auricap leads are too fat for the pcb holes. How do the Wima's sound compared to Solens? Should I just stick with the Wima's?
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