Re: {Collins} Collins 212A and 212B Broadcast Consoles



Gene,

Did not know that you were the designer on this. This design seems to be the predecessor of the VCA buss used in later broadcast consoles. 

I have one and it is a great board but most of the photo cell attenuators have failed in mine - would love to be able to bring it back to fully operational original condition!! 

Scott Kerr
President
TrackerSoft, LP
skerr@xxxxxxxxxxxxxxx
214-991-2850
Tech Support 214-237-7001
Sent from my iPhone

> On Nov 19, 2015, at 12:50 PM, Eugene <earobinson@xxxxxxxxxxxxx> wrote:
> 
> I was the designer of the 212S console, the first Collins stereo console about 1963/4. I came out of a broadcast family background growing up around stations in the 40's and 50's. 
> The 212S did have a separate audition/monitor bus. 
> The 212S also used "photo cell" attenuators that I developed instead of Davin attenuators to minimize the amount of twisted shielded jacketed wiring and associated cost. 
> The distortion for this first all transistor stereo design was less than 0.25% over the full operating range. This greatly reduced the manufacturing labor and parts cost. We also attempted to eliminate the 600 ohm preamp input transformer but we could not assure ground loops would not be present when installed in the field. The final design ended up with a very small German made isolation transformer on the input of the preamplifiers. The noise floor for the preamplifiers was -127db with a 20 kHz bandwidth. The preamps dynamic range was -87dBm to 2 volts P-P.
> More than you wanted to know but Yes the 212S did have a separate audition bus.
> 
> Gene Robinson, N5LDX
> 
> 
> Sent from my iPad
> 
>> On Nov 19, 2015, at 10:47 AM, Scott Kerr <skerr@xxxxxxxxxxxxxxx> wrote:
>> 
>> separate audition bus



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