Regarding attenuators, I've been looking at alternatives for tube
equipment. As I see it:
- autoformer attenuators need such low impedence in that you're looking
at big caps before them to stop the DC. So anything you gain on the
autoformer you lose on the cap. I use russian teflon caps of 0.1uf
value, so I'm not keen on large multiples of them. I'm OK with up to
..3, maybe .5 in extremis.
- true transformer attenuators are interesting - eliminates the cap if
it allows DC.
- On the other hand you could, in balanced mode, just use a PP output
stage for the line out, and position the volume control after that - no
cap.
- Cap before stepped attenuator is what I use right now. It works, and
sounds good with teflon caps. My line stage is balanced, so I use a
shunt attenuator between legs, which in the present case is 47K shunt
with two series resistors of 22K before it, one in each leg. So the
resistance in the stepped attenuator isn't exactly constant.
- for convenience of input between SE and balanced, the next way I'm
going to build is integrated mono amps with stepped attenuator after
the first valve stage. this means I can use the same shunt attenuator,
but I can accept input as SE or balanced, depending on whether or not I
earth the second grid of the input pair.
Thoughts and ideas? Andy