Re: Where is Graham's mixer design? (was Re: RAT Tube Mixer update?)

In article <Kwszj.306398$SZ6.125156@[EMAIL PROTECTED]
>,
 "Iain Churches" <IainNG@[EMAIL PROTECTED]
> wrote:

> "John Byrns" <byrnsj@[EMAIL PROTECTED]
> wrote in message
> news:byrnsj-7A13F2.13431604032008@[EMAIL PROTECTED]
> 
> > 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.
> >
> 
> John. There is an Ampex MX-10 tube mixer on e-Bay.  1 day to go,
> so take a look a.s.a.p.
> 
> Regards
> Iain
> 
> 
>
http://cgi.ebay.co.uk/Ampex-MX-10-Vintage-Tube-Mixer-Rackmount_W0QQitemZ230227
>
561997QQihZ013QQcategoryZ119022QQssPageNameZWDVWQQrdZ1QQcmdZViewItem#ebayphoto
> hosting

I remember back around 1990 the MX-10 was all the rage with the guys on 
rec.audio, those were the days before the split into rec.audio.opinion, 
rec.audio.pro, rec.audio.tech, and rec.audio.tubes.  I think I have a 
PR-10 maintenance manual somewhere around that may include a section on 
the MX-10.

The MX-10 uses traditional pentode microphone amplifiers which probably 
wouldn't sit too well with today's triode fanatics, or provide the 
lowest noise level.

The MX-10 also uses the dreaded pan switches (left, center, end right) 
rather than actual pan pots.  It also has an interesting "virtual earth" 
mixer circuit where the impedance of the "virtual earth" point varies 
greatly depending on the setting of the internal level adjust controls.  
The channel crosstalk must be horrendous when the level adjust pots are 
set for maximum gain and two microphone channels are centered while one 
each are panned left and right.

Add a couple of more microphone inputs, a more robust balanced output 
stage, and a headphone monitoring amplifier and it looks just like what 
"T" needs.  Oops, cancel that, the pans switches would also have to be 
replaced by pan pots to meet his specs.


Regards,

John Byrns

-- 
Surf my web pages at,  http://fmamradios.com/