"Ian Iveson" wrote in message
om...
: OTOH, until we know what you are trying to achieve, it is hard to
: help.
:
: There are a heap of considerations here, concerning where and how the
: mixing is done, and from and to where the feedback might go.
:
: AFAIK, your original concerns were relevant in a different context and
: may not be applicable here.
:
: Have you considered simulation? With spice you can get a reasonably
: accurate comparison of topologies, with their characteristic
: distortion and frequency responses.
:
: Several folk hanging out on rat use circuitmaker, and there are a
: range of valve models available. Certainly there is no shortage of
: models for such as ECC8X and EF86. You do need to find one with enough
: sophistication to reasonably approximate the distortion.
:
: Your plan seems reasonable to me, and clear in outline. One obvious
: question though: if it were possible to take your kind of short-cuts
: to console design in the 50s, why didn't they do it?
:
: If you take your feedback from the output of the white cathode
: follower, you will have a ring of three, which is a classic circuit
: for some reason I can't remember. Have you considered mu-followers for
: the gain stages, or perhaps just for the second? If allowable you
: could achieve such by using MOSFETS for the top devices.
:
: cheers, Ian

Yep, that could 'shave the bill', second stage will have large
voltage swing, little mosfet background noise won't hurt

Can't beat solid state noise-wise, no question. But you can
emulate the strategy to a certain extent, that is, use a 'massively'
parallel device approach, massive being in practical terms: 4.
Cheaper than 2 EF86's paralleled by quite a bit would be 4
Telefunken or Siemens C3m's ,triode-strapped, which would
give you about 60* amplification at about the same levels
as the EF86's, probably somewhat higher distortion (have
no data readily available, just the curves) and requiring a
'meetier' current source on top.
No data on noise, but as they were developed for long-
distance repeating of signals, low-noise was 'in by design'.
Worth a try, maybe, coz' these german telecom's tubes are just
now appearing on the market, in abundance it seems - hence
to good to be true pricing

Keep up 'the quest' ,
Cheers,
Rudy