Check it out to be sure but I don't expect appreciable differences in offset compensation with that output stage bias change.
Salas DCG3 preamp (line & headphone)
Michael Percy Audio sells a 25k CP2500. There is also a smaller 16mm pot, the CP601, which I have used. It is good (better than an Alps RK27 blue), but not as good as the CP2500.
There is also the Alps RK50, which is really expensive (and good), but ~$600 or so. Not sure if Penny and Giles are still making their rotary pot or not, but those are quite good as well.
Michael Percy Audio sells a 25k CP2500. There is also a smaller 16mm pot, the CP601, which I have used. It is good (better than an Alps RK27 blue), but not as good as the CP2500.
There is also the Alps RK50, which is really expensive (and good), but ~$600 or so. Not sure if Penny and Giles are still making their rotary pot or not, but those are quite good as well.
In any case you can add Zo via upping R1 if you will feel any thinning of tone vs the 20k.
Salas,
If only changing gain resistors, shouldn't be any offset differences, right?
I want to use a gain switch on mine.
Rush
In my doubled up balanced setup, XLR pin 1's are connected to the chassis. The two DCSTB unit G's are each connected to a common chassis point thru CL60/caps. To this common chassis point the G wire from the Pem is also connected. My PEM is a Schaffner unit with a filter builtin. When I pulled the G wire off the PEM the 320hz spike went down quite a bit. I have not had a chance to check it with a filterless PEM
nash
Thanks for details.
My SE unit single signal GND wire is connected from attenuator common L/R GND to Earth/enclosure joint-point with Rod Elliott concept (10R GND elevation). Almost same as your way, beside you are using 10R/6A thermistor. But, I also have big yin yang diodes there. I’ll try to remove 10R resistor, as Salas indicated, and see if my 60Hz spike damped down.
I believe that the rest of spikes which I see below 1kHz are harmonics from that main one.
Does your Schaffner use Y caps for common mode noise suppression?
My Ultraperm 80 sheets are on the way. Let see then...
Salas, my TKD 10k pot is on the way. What range of added resistance should I play with? I added resistance to balance the bias. You were right, it was academic, could hear no difference from memory. Also lowered gain to 2x, still boatloads of gain, never get past 11 o’clock on volume control on any material. I’m having way to much fun playing with this preamp!!!
Its your speakers are very sensitive. What, 100dBSPL/W/m? Can you drop the power amps voltage gain by say 6dB? That would lower the system's noise floor, increase the damping, lower THD, more hand on the pot, win win.
10k ladder has as much Zo (max output resistance) as a 20k series one. So it should be equivalent to your 20k Alps blue. If you should hear any untoward tonal balance tilt to thinner start with good quality 1k from wiper to DCG3 input and climb by 1k until satisfied.
The TKD declares ladder internal arrangement although a full ladder has two points of contact and two sets of resistances. I would like to measure the TKD to see how it really behaves for insertion Zo.
10k ladder has as much Zo (max output resistance) as a 20k series one. So it should be equivalent to your 20k Alps blue. If you should hear any untoward tonal balance tilt to thinner start with good quality 1k from wiper to DCG3 input and climb by 1k until satisfied.
The TKD declares ladder internal arrangement although a full ladder has two points of contact and two sets of resistances. I would like to measure the TKD to see how it really behaves for insertion Zo.
By the way, according to killie99's hands on experience from Alps to TKD, the curve alone should help volume control over your hi sens speakers.
P.S. There are also many fake Alps in circulation that look very close to the original. Which is kind of opaque anyway but fakes can really intensify the quality perception jump to a TKD.