I'm modifying my RAKK DAC to incorporate an analogue volume control as it is my only 'source' component and the addition of the volume control is far more convenient with two mono power amps.
I'll be adding the KandK passive I/V module, which uses a couple of Llundahl transformers and delivers a balanced output, and will use a switched shunt attenuator. I could use this as a passive volume control but I need to connect to the power amps over interconnects a couple of metres long so probably not a good idea and a linestage to drive the cables seems like a sensible thing to do. I don't need substantial gain in the linestage, unity to 6dB will be fine.
I could use a Pass JFET DCB1 linestage that I have; by reputation very good. This is unbalanced. It represents an easy implementation. I was going to use this module in a DAC for a spare room system.
Alternatively, I have a pair of Welborne CATO modules that I've previously used as an active I/V dac output. The CATO is a valve/mosfet hybrid circuit that sounded excellent in the previous set up. Anyway, it is possible to reconfigure the CATO module to act as balanced to single-ended convertor/line stage and this is tempting given the previous positive experience and the fact that they're otherwise not required.
However (I got there in the end but I thought context important!) the quoted Common Mode Rejection for this configuration is 50dB, which seems a bit low given that op amps and the like usually quote up around 100dB CMR. Is a figure of 50dB CMR likely to be an issue?
Ta muchly
Ray
CMR Question
#2
I asked this question over on DIY Audio too; it seems that 50dB CMR isn't bad within the audio band (which isn't where opamps are measured apparently) so I'm gonna reconfigure the CATO modules as balanced/single ended convertor linestages and see how it works out.
Ray
Ray