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In Reply to: Ampex 351 Preamp + Other Transport? posted by jdubs on October 23, 2006 at 20:29:32:
Would probably work OK at least for playback. Head impedances in transistor decks are lower. Playback Equalization would have to be tweaked - requiring a playback calibration tape (from MRL?) and maybe some adjustment of the input (head loading) resistor. Good luck in finding the Cannon plugs for the head connectors - might want to add RCA's on the back in parallel.
Follow Ups:
One could maybe get away without adjusting the input resistance going from a medium impedance head in a SS deck to the high impedance input of the 351 repro amp. Depending on the head used the output of the head might be a little on the low side for the gain structure of the preamp. Bear in mind that stock 351 repro electronics sound very nice, but they are usually a little noisy. All that said Charles is right, it should work. The reverse situation of running a high impedance head from a 351 into modern SS electronics would probably require adjustments.
Hi, Doc:I own an Ampex 351-2 which came out of our local "Berkeley Youth Radio" and it was in a rollaround cabinet with Innovonics electronics installed above. I assume that the Innovonics (sp?) electronics, though not as nice as the original preamplifiers which came with the deck, had been tailored for that transport.
Any comments, except the obvious one that Innovonics stuff sucks?
According to the manual, the Innovonics 376 can work with heads ranging from 200mH to 1H, with the optimum being 200mH.If it is equipped with the optional head transformer, and the strapping is changed accordingly, then it will work with heads ranging from 3mH to 6 mH, with 4mH being optimum.
Thanks, Paul!I have the data on the machine and I believe that everything is "as per".
This one turned up at the old location of Urban Ore in Berkeley many years ago.
If anybody is interested in acquiring this machine, it is available locally for very reasonable $$$
The transport is oddly marked "352-2" but to me, it is a 351-2.
Probably 7.5 / 15 ips only though. I cannot remember at the moment!
I purchased the deck essentially for the nice cabinet, which I wanted to insert my 3534-4 into one of these fine days!
Only Bodyslam would have the manual, and dig it out for you.
Hey Richard,I'm afraid I have no experience with the Inovonics preamps, but AFAIK they were indeed designed specifically for high impedance Ampex heads. The reason they were being retrofit in the 70's was supposedly about lower THD and the ability to handle really high output levels. Of course back then we all knew that SS circuitry was vastly superior to tubes. ;^)> I did find one reference to their sound being described as "aural sandpaper".
My only experience with aftermarket repro amps on a 351 is the Shafer tube preamps as used on Dave Dintenfass' Herniator MKIII at VSAC 2003. They sound very nice, but do suffer from the same bit of hum as the stock electronics.
Thanks, Doc!Sounds like the stories I have heard from others when it comes to those SS electronics as substitutes for the tubed originals.
I ran into Dave D. at AES two years ago, but not this year, though he may have been somewhere over in Moscone Center in SF.
I hope you were there and enjoyed the convention this year!
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