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

"John Byrns" <byrnsj@[EMAIL PROTECTED]
> wrote in message 
news:byrnsj-0DC5A7.11355805032008@[EMAIL PROTECTED]
> 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.

It will be interesting to see what the one on e.Bay goes for.
Ampex seems to be flavour of the month at the moment.

>
> 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.

Wasn't it triode strapped?

>
> 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.

Tynan is not planning (as far as I know) to do multitracking, so
channel crosstalk may not be too crucial.
>
> 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.

I am still digging for info about a similar (better) product
from the UK, built by Vortexion.  Units could be daisy
chained together to form an expandable mixer with a
common buss.  It had huge rotary faders and a PPM for
each unit.

> Oops, cancel that, the pans switches would also have to be
> replaced by pan pots to meet his specs.

I made many many recordings (years ago) on a tube
desk that had no centre pan at all.  There were four
groups, so to centre vocal in a mix you had to send
the channel to Gr 1+2 and then parallel on the patch
bay:-)   Boys, you ain't seen nuffink!!

Regards
Iain