Hi Russ and Brian,

I am building an SRPP tube output stage to your wonderful DAC and getting good results. I am looking for some assistance with refinement to the design:

In my design I have used 2 tube-i-zator circuits and created a balanced design (currently using one BIIIse but with the ultimate aim of using 2 x BIIIse for full dual mono). The default I/V resistor value specified is 56R (you can see the circuit here: http://www.diyaudio.com/...ge-tube-i-zator-v2.0.pdf )

I believe in the past that you have recommended to experiment with 20R-30R but is this still the case for a balanced, dual mono design?

I am also interested to know what I should be listening for as I change the values. I currently am using 4 x 22R within the DAC but I can't really tell the difference between this and the originals. Are my ears just terrible or do I just not know what to listen for ;-) I also have a scope but I am not sure what to measure so I am currently doing it by listening!

I know that this is probably stretching your 'support goodwill' a little but there have been 2 further refinements to the output circuit and I'd be interested in whether similar changes can be made if the circuit is being used for a BIII (as opposed to the TDA 1541A). The modifications are shown here:

https://imageshack.us/a/.../8856/tubeizatormod2.jpg
https://imageshack.us/a/...eizatorccsfortda1541.jpg

Thank you for any thoughts.
Crom