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Matching reverb pans to circuits?

2/17/1999 7:37 AM

Mark Hammer
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Matching reverb pans to circuits?

As an outgrowth of a series of correspondances between myself and another AMPAGE reader, I have a few questions to ask.

When you have no technical specs on a spring reverb pan, how do you go about finding out its electrical characteristics so as to best match it to a reverb circuit/project?

Just exactly how fussy ARE supporting electronics for spring reverb, and what should one expect when the marriage of pan and circuitry is not made in heaven?

Undoubtedly, this is a problem area that is not unlike transformer-speaker matches, except that speakers have the luxury of being coupled to air at one end, rather than more electronics. They also tend to be behave in a little more predictable manner than a floppy piece of rolled up wire.

2/18/1999 1:46 PM

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Mark:

(I had this whole thing typed out for posting earlier today, then lost the entire text when our server connection crapped out.)

I usually measure the DCR of the input & output coils, then compare measurements to published chart from Accutronics. This can get you in the ballpark as to what type of drive circuit & recovery circuit are best suited from a load impedance standpoint. You can at least determine if it will require a Fender type low impedance drive system, a high impedance Ampeg R-C coupled drive system, or a medium impedance (various solid state setups) drive system. I think the recovery coil isn't as critical as the drive coil. The transfer of power is the main parameter affected when the proper match isn't obtained. Plug a Fender type tank into an Ampeg circuit. There will be almost zero signal strength recovered, due to the drive coil mismatch (recovery coils are same for both).

I have encountered various pans in imported SS amps, and imported pans in Crate amps, that don't match the standard Accutronics offerings. These were all short tanks, BTW. I don't think anyone uses std. length (long) tanks produced by other than Accutronics.

The mounting orientation (best orientation for not bottoming out the suspension causing "crashing") is a tough one to identify w/o the factory codes.

Also, the decay time is not easily guessed w/o factory code. Listen to the tank in an actual circuit would be a way to get an experienced judgement. For instance, try a 4AB2..tank, then substitute a 9AB3, in a working Fender reverb amp. They both match the circuit electrical requirements, but have an easily recognizable different sonic character (which also depends on room size and amp knob settings).

Doc

2/18/1999 3:55 PM
Mark Hammer	Thanks. Useful info.

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