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Kahn Symmetra-Peak

Mike Phillips

Mike Phillips

Do you have a Kahn Symmetra-Peak taking up space that you'd like to sell? I'd like to play with one for a project. According to Kahn, these things were everywhere.

Kahn Symmetra-Peak

I've found the parts to build one, but buying one would be a lot easier.
 
The Symmetra-Peak was nothing more than a passive allpass filter.
You can easily build an active version using a couple of ICs.
 
frankberry said:
The Symmetra-Peak was nothing more than a passive allpass filter.
You can easily build an active version using a couple of ICs.
Click to expand...

Anyone know the specs on it? I'd be curious as to the filter parameters that Kahn used (number of poles, frequencies, Q, etc.), in order to duplicate it digitally. Just for grins, of course. ;-)

Kind Regards,
David
 
I know where one is at my day-job, and one of my free-lance clients is on the list as having a "superior" unit. I'll have to dig around and see if I can find it.
 
I picked mine up at Dayton in a "bone pile" of stuff spread on the ground for $1.00 a few years ago. It works well on my ham station audio chain. An all-pass filter cascade with op amps would be just as effective. It does average out the voice peaks fairly well and looks nostalgic in the rack with the TMC SBE-3 exciter and PAL-1KB 1kw amp.

Most processors include some sort of all-pass network to make peak clipping easier. I like what it does with voice but have never liked how it mucks up music. I prefer separate mic and music processing where the mics get preconditioned and dynamic range reduced before they hit the main processor as most have found (I do like Aphex very much).
 
Sorry for this late addition to the thread.
Back in the late 60s, I worked for WGTO, Cypress Gardens, Florida. They had a passive Symmetra-Peak in the program circuit at the studio.
I commented several times that the on-air bass sounded strange. Not quite the same as high Harmonic or IM distortion but it did sound strange.
I'm guessing that the Symmetra-Peak was responsible for producing this "signature" sound.
 
well it just so happens that we at the new WGTO have one of these units on the shelf. I have played with it but it seems to have a rather high peak in the voice range. Could be because I did not have it terminated in 600 ohms as was the practice back in the old days. Make almost any offer and I am sure I can get it out of the door.
 
Symmetra-Peaks did help voices, but did music no favors. Those boxes did have a "signature" sound related to the sub-par bass.
 
WGTO said:
well it just so happens that we at the new WGTO have one of these units on the shelf. I have played with it but it seems to have a rather high peak in the voice range. Could be because I did not have it terminated in 600 ohms as was the practice back in the old days. Make almost any offer and I am sure I can get it out of the door.
Click to expand...

The termination impedance is critical. The tuned circuits can do some strange things into impedances other than 600 ohms.
 
Mine is being fed by a balanced op amp low impedance output that I built out to 600 ohm at the Kahn input and it has a 620 ohm across the output to feed the 10k balanced input of the next device.
 
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