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Mix-Minus

SFM-Ptgal said:
How was the mix-minus feature for telephonre hybrids achieved on the vintage broadcast consoles, those with simply Audition-Program bus outputs, like this one:
http://www.oldradio.com/archives/hardware/Gates/Gates-Stereo80.jpg ?
Click to expand...

I believe in the (really) old days, mix-minuses were relatively uncommon. At least in all but the larger facilities. We would just send the announcer's mic audio downstream to the caller, and that was all. It was adequate for most purposes as, in smaller markets especially, there were fewer instances of the telephone-intensive programming that requires a mix-minus. You didn't see many consoles with extra 'utility' busses until PR&E came along roughly 30 years ago.

If the console does not support enough mix busses to create a mix-minus, you would have to build it outside the console. It's possible to do with an external, parallel mixer, but you don't have near the flexibility or capability to create the identical mix, never mind the convenience, that you have when you can use a single fader for each source.

On the other hand, if the mix that you need to make requires duplication of only a few sources, it's not impossible or operationally unmanageable.

If you **really** want to go crazy, you could design and construct another mixing bus internally... :)

Kind Regards,
David
 
In The Day, the little Shure micropnohe mixers were the weapon of choice. You could mix four mics, and you could feed the phone hybrid before the mic faders, so the caller heard constant level audio which didn't change if you put him on air.
 
I remember years ago just using the speaker phone accessory that Bell Telephone (AT&T) furnished for their old key sets and an amateur type hybrid phone patch. In those days the phone company also applied a beep tone to alert the callers that they were being recorded which was inserted at the isolation transformer required between your stuff and theirs. I think the side tone suppression built into the phone made the back feed of the announcer from the phone less objectionable.

More recently I built a similar set up for taking viewer calls in a cable TV access studio and it worked pretty good. You could detect a bit of the audio from the phone but since the talent was miked with lapel mikes the difference was acceptable due to the proximity differences. If I had had one of the Shure portable mixers I would have used that set up to feed the downstream audio from the studio and then to the main mixer adding the upstream there to keep them separate which is what was done before mix minus was built into the main board. The old Gates Producer Consoles worked great for that too.
 
in the ancient days of consoles, most stations used the Shure M-67 or M-68 mixers

mics went to inputs, output (set to 'mic level') went to a mic input on the console, the 67/68's 'auxiliary' output fed the hybrid (often-times an amp was needed); output of hybrid went to separate input on console

then came consoles that had the ability to feed 'program' and 'audition' simultaneously, all mics went to both 'program' and 'audition', 'audition' fed hybrid and output of hybrid fed 'program' thru another pot

then console makers started putting mix-minus busses in as standard equipment

I think...........it's been a while
 
Gary Glaenzer said:
in the ancient days of consoles, most stations used the Shure M-67 or M-68 mixers

mics went to inputs, output (set to 'mic level') went to a mic input on the console, the 67/68's 'auxiliary' output fed the hybrid (often-times an amp was needed); output of hybrid went to separate input on console

then came consoles that had the ability to feed 'program' and 'audition' simultaneously, all mics went to both 'program' and 'audition', 'audition' fed hybrid and output of hybrid fed 'program' thru another pot

then console makers started putting mix-minus busses in as standard equipment

I think...........it's been a while
Click to expand...

The Shure Mini Mixers appeared like mid '60s. Shortly after that I think early '70s consoles with the push pad switches became available which let you feed audition and program simultaneously. The first ones I saw were custom made by a company in Louisville Kentucky and had 16 mix channels which could feed 4 different output channels in any combination. These features later got incorporated into the top of line off the shelf consoles.

The system I related was used in radio and TV in the early 60's and mid fifties. I recreated it in a way for a Public Access TV studio in the 80's because we had no money to buy auxiliary mixers of any kind. The caller heard the studio talent through the speaker phone as well as the studio hearing the caller. Separation was maintained by the lapel mikes and putting the speaker as far as possible from the mikes. Crude but it worked.
 
You may be able to pick up the output of the mike preamp on your Gates console and use that to feed your hybrid. Believe it will have enough level, though you might have to put a fixed pad in place if it is too hot, based on your normal mike level into the program channel.

Don't specifically recall all the details about your model board, but many of these Gates/Harris boards have a series of switches used to select remote lines into one channel. Have seen consoles where one of these switches is split off from the group and used as an isolated select switch for various functions. Might be a way to switch feed to the hybrid on or off.

Until three years ago, our production console was a 1983 vintage Autogram. But that console had the innovative feature of a switchable mono buss, which we used for a mix-minus feed to the hybrid. But this was a production console--we could set-up ahead of time for a session when we needed to record a telephone interview. Usually something like an interview with a coach for later reply before the live broadcast of a game. The Shure mixer scheme sounds more practical for air use.
 
An easy way to do mix-minus is put a transformer into your microphone line when on telephone calls which only carries the studio
mike audio, inserted so the audio from the mike partly cancels the local audio. A 70-volt public address xformer offers several taps for a desired level of cancellation. The caller's audio does not receive the cancellation.

Another cheapie is a high-quality AGC or compressor dedicated to the telephone circuit.
I recently ran across a telephone recorded call I made on a Panasonic 1968 cassette recorder back in 1972, direct from the earphone circuit of the phone, where the levels are equal and balanced with no special efforts made.
 
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