DECWARE.....ZTPRE anyone have any expeiriance with one ?

Finally, to be sure we are looking at the same schematic, I am looking at the one shown on the last page of the manual.

Yes I think that’s the one Al pdf you have to rotate it twice, what I see that the cap sees is if the pot is at half way is a series and two parallel resistances, and yes as you say if full up it get’s closer to just 2 x parallel resistances.
Anyway whatever that cap is too small, and should be at least 1uf to take away the problem if close or full up on the VC.

Cheers George

almarg
The cap will only "see" the input impedance of the power amp when the 100K output level control is at or near max.

You sure Al, I see it like the cap seeing the "parallel" combination of what the volume control and poweramp impedance is combined, just like two paralleled resistors. As the pot goes to ground like the input of the poweramp would.

EG:
Pot = 100kohm
Amp=100kohm
Cap sees= 50kohm


Cheers George

almarg
I see that the output tubes are coupled to the output connectors via capacitors having what to me is a very surprisingly low value of 0.1 uf

I just downloaded the latest I believe circuit.
And what Al has pointed out is quite bad, as if that preamp’s xlr output sees an input load of 20kohm the bass will be rolled of at -3db already at 80hz!!!! In other words you’ll have no low bass.

If it sees a Class-D amp which many have 10kohm input impedance, the bass will be -3db at 160hZ!!!! no upper bass either!!!

It’s rca output "could" be fine as they are isolated by the transformer coupling from outside amp impedance’s.

I suggest you don’t use the XLR output with any amp/s less than 100kohm input impedance.

Cheers George