D.Self and maybe some others have analysed that attenuator style and told us it is not good.
Something to do with the attenuations of CM and DM interferences.
I used to think this simple rheostat attenuator maintained the balanced impedances and thus was perfect, until I read D.Self, then I stopped recommending it.
You are welcome. Enjoy
P.S. Is the VTA SP14 an Aikido related type of circuitry?
I will have to check out the Aikido. The SP14 uses two 6sn7's per channel with s/s rectification and regulation for the heaters with valve rectification and s/s regulation for the h/t.
BTW for those who utilize the DCG3's headphones output too, mainly for North American market accessibility, the new $300 106mm planar Monoprice M1060 seems to gather interest for delivering large magnetostatic goodnesss on the cheap. Has some construction issues others say. That would not stop curiosity it proved as they are out of stock already.
https://www.monoprice.com/product?p_id=16050
https://www.youtube.com/watch?v=dlWaIDITScI
https://www.monoprice.com/product?p_id=16050
https://www.youtube.com/watch?v=dlWaIDITScI
Hi Salas
Do you have more info on what the benefits are in adding a resistance there or any links to discussions about this that you are aware of?
Thanks
hello Salas
Now that I reasonably finished my power amps that have 30dB gain and produce a sound quite lisible, I am enjoying the DCG3 as I should.
But I have a small issue, with the DCG3 I hear a low level noise only aparent when there is now signal. It seems like digital crizz but might as well be other thing.
Can the preamp be uncompatible with the V12R I am using ?
Now that I reasonably finished my power amps that have 30dB gain and produce a sound quite lisible, I am enjoying the DCG3 as I should.
But I have a small issue, with the DCG3 I hear a low level noise only aparent when there is now signal. It seems like digital crizz but might as well be other thing.
Can the preamp be uncompatible with the V12R I am using ?
Hmm... now that's complex enough because it has stacked positive PSUs, sense runs, two pots.
1. Ground the metal necks of the pots.
If something does not change to the better... 2. Sever the top layer's front edge ground plane at mid-line between channels with a hobby knife and replace the now yellow to chassis wire with two of those connecting the pots signal return legs to the chassis screw like a Y. Because I possibly see a PSU 0 ground bar wire going from edge to edge connector and the loop continues around through the GND plane.
1. Ground the metal necks of the pots.
If something does not change to the better... 2. Sever the top layer's front edge ground plane at mid-line between channels with a hobby knife and replace the now yellow to chassis wire with two of those connecting the pots signal return legs to the chassis screw like a Y. Because I possibly see a PSU 0 ground bar wire going from edge to edge connector and the loop continues around through the GND plane.
Changing the GND layout did not help but I scoped the shunt outputs and found noise in the MHz range.
I am using shunts that I saved from an old folded build so they are optimized for 35Vout.
In this case I have one 30kohm resistor fro vref and the tail ccs jfet has a trimmer in the source leg so to get the desired 17Vout I just turned the trimmer pot. current in the shunt ccs might be too small and also current in the vref ccs.
I will build new dedicated shunts for this preamp and report latter.
I am using shunts that I saved from an old folded build so they are optimized for 35Vout.
In this case I have one 30kohm resistor fro vref and the tail ccs jfet has a trimmer in the source leg so to get the desired 17Vout I just turned the trimmer pot. current in the shunt ccs might be too small and also current in the vref ccs.
I will build new dedicated shunts for this preamp and report latter.