Passlabs D1 (PCM63) vs. Threshold DAC-2 (Ultra Analog D20400a) - who have heard both?

no reason to change neither value nor power of zeners used

with normal use and procedures, nothing wrong will happen

zener is there to cover mishaps and possible power-on transients, in case someone get to different cap values (before and after series CCS)

and, this time, I can bet it did what's placed for - JFet is still alive

again, who knows what zap you made, while having things wrongly connected
 
R9 is gate stopper, of course that it is in signal path

though, if you enjoy being anal, chasing "better than proper industrial metal film", be my guest

R11 is practically load for Q2 source follower; final element where current swing being converted to voltage swing, so - yes - it is in signal path

again what I wrote in second line
 
Another question...

For the beautiful array of 'output' capacitors, is the role DC blocking, and is the value (15uF) selected to have appropriately low roll off in the context of the preamp input impedance?

Cheers -

1737678651911.png
 
Thanks ZM. I can be a bit dense...

You must have anticipated the next question.

So, going into a 50k input impedance preamp, if I get it right, the -3db roll off is about 0.2 hz. At some point, I gathered some 1uF caps for DC blocking in a tube DAC and I was just wondering if it might be worth trying them in the D1, if/when I get bored. It seems, 1 uF would give a 3.2 hz -3db roll off. Now my Casio is limited to very basic functions and I may have this all wrong.

And not asking you to bust out your calculator..

Cheers,
Soren
 
Good news for Threshold DAC-2 owner's:
go to post #21 under
 
The only curious thing about firing this up, is that you measure and adjust DC offset on the INPUT.

Fed it +/- 30V and let it cook for 20 min without the DAC chip connected to the input. Measure offset on the inputs and adjust. Once you are happy, connect the DAC output and enjoy.

If bypassing the on board PSU, you can always study my photos for how not to connect it 😊
 
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