In article <NZ1zj.188534$LD6.127142@[EMAIL PROTECTED]
>,
"Ian Iveson" <IanIveson.home@[EMAIL PROTECTED]
> wrote:
> Ian said:
>
> > Well, I've made my position clear a while back and I have
> > been busy lately doing part 2 of NFB 101 in the process of
> > which an idea struck me. Has anyone thought of using a
> > grounded grid amplifier as a mix amp?
>
> Yes. It seemed the obvious choice for the bus. An
> alternative would be an ordinary gain stage with a low value
> grid resistor.
>
> I couldn't maintain interest in mixer design beyond getting
> the ideas straight. It seemed like a fool's errand, and
> still does. I can't see why a valve mixer is a good idea. A
> box of mic amps, yes, with a state of the art SS mixer amp
> and chip earphone amp, maybe.
>
> And I could only copy a respected valve mic amp, considering
> I've never done any recording and have no idea what they are
> supposed to sound like.
>
> And I noticed that no-one else has actually posted very
> specific details. Coyness, in addition to the usual
> animosities, was clearly going to frustrate any attempt at
> serious discourse.
I posted a block diagram description of my Mk II design along with the
specific tubes used in each block a while back. IIRC, from that
description Ian Thompson-Bell was able to correctly describe the circuit
topology I used in each block, so all we need now are the component
values and a few details like the pan pot circuit and how feedback is
applied around the various blocks. So if you would like to know the
values of any particular resistors in the circuit you have only to ask.
The circuit details have been undergoing constant refinement, so far the
changes have involved a switch from a pan pot circuit using a single
element pan pot to Ian's pan pot idea using a two element control, and
some details of the feedback circuit around the microphone preamp are
still up in the air, but everything else has remained pretty well
settled in the Mk II design. My Mk I design, which used way too many
tubes, used a two element pan pot circuit like Ian proposed, so you
might consider adopting Ian's pan pot design simply a reversion to my
earlier design.
The work on my BBC inspired "RAT Retro Mixer" design has got me thinking
about yet another design inspired by the Ampex recorder electronics that
Iain mentioned in another thread. I haven't yet put this simplified
design to paper, but I am tentatively calling it the "RAT Audiophile
Mixer", a mixer designed to please the fanciers of SET amplifiers, if
you will.
Regards,
John Byrns
--
Surf my web pages at, http://fmamradios.com/
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