ampage Tube Amps / Music Electronics	For current discussions, please visit Music Electronics Forum.

ampage archive

Vintage threads from the first ten years

previous: Mark Hammer Technically, there are two ways to ... -- 10/10/2000 1:58 PM

Re: Increase the decay time on spring reverb?

10/12/2000 2:05 AM
jon	Re: Increase the decay time on spring reverb? Hi Mark, How you been? Thanx for the thoughtful in-depth reply. Coupla observations, and a few resultant questions....I've messed with several tube reverb circuits, found I really prefer the Ampeg capacitor-coupled circuit tone wise to the more common SE tranny coupled. Ran across this EL-84 cap coupled reverb circuit in an old Magnavox stereo console, was intrigued by the design. Unit used a Hammond tank (2 springs, long tank)with high impedance and short decay.Couldn't adapt it to work well with guitar, way too much in the way of microphonics. Kevin O' Connor has a nice section in one of his books describing that this is a real inefficient approach, so I went back to my old habit of breaking things to fix them to learn how they work....learned a bit about impedance matching of the tanks, etc. I've got several tanks that were pulled from SS reverb circuits (high impedance also, one has medium decay/2 spring and the other has medium decay/3 spring/short tank.) Both of these sound great with the modified Ampeg circuit. I was hoping to modify the Hammond from short to long decay to use in another project. I tried lengthening the springs, (tacked on additional springs of similiar characteristics) and shortened the springs by changing the hook-up point. In both cases, didn't really change the decay time much. that's what got me to thinking about the stationary magnets..... As far as changing circuit parameters, I was under the impression that "dwell" is really a drive control, determining how much signal voltage is presented to drive the pan. Up the signal voltage too high, and you go from increased decay to mud which happened when I messed with that circuit parameter, even with significant tone shaping). I'd like to learn more about the BB type approach, still waiting on "Guitar Gadgets" to arrive. Is there info there, or can you suggest other sources? cya, Jon

10/12/2000 2:05 AM

jon

Re: Increase the decay time on spring reverb?

Hi Mark,
How you been? Thanx for the thoughtful in-depth reply. Coupla observations, and a few resultant questions....I've messed with several tube reverb circuits, found I really prefer the Ampeg capacitor-coupled circuit tone wise to the more common SE tranny coupled.

Ran across this EL-84 cap coupled reverb circuit in an old Magnavox stereo console, was intrigued by the design. Unit used a Hammond tank (2 springs, long tank)with high impedance and short decay.Couldn't adapt it to work well with guitar, way too much in the way of microphonics. Kevin O' Connor has a nice section in one of his books describing that this is a real inefficient approach, so I went back to my old habit of breaking things to fix them to learn how they work....learned a bit about impedance matching of the tanks, etc. I've got several tanks that were pulled from SS reverb circuits (high impedance also, one has medium decay/2 spring and the other has medium decay/3 spring/short tank.) Both of these sound great with the modified Ampeg circuit.

I was hoping to modify the Hammond from short to long decay to use in another project. I tried lengthening the springs, (tacked on additional springs of similiar characteristics) and shortened the springs by changing the hook-up point. In both cases, didn't really change the decay time much. that's what got me to thinking about the stationary magnets.....

As far as changing circuit parameters, I was under the impression that "dwell" is really a drive control, determining how much signal voltage is presented to drive the pan. Up the signal voltage too high, and you go from increased decay to mud which happened when I messed with that circuit parameter, even with significant tone shaping).

I'd like to learn more about the BB type approach, still waiting on "Guitar Gadgets" to arrive. Is there info there, or can you suggest other sources?
cya,
Jon

Replies:

Mark Hammer I'm okay and back at work. Thanks ... -- 10/12/2000 3:39 PM