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FDP Forum / Fender Amps: 1985 - Current / Princeton and Deluxe Reverb pans

Rob Jai

Calif Cap City

"Jai" pronounced "J"
Aug 18th, 2016 10:39 AM   Edit   Profile   Print Topic   Search Topic

A couple of questions. What is the purpose of the reverb pans in these amps (and probably others) being enclosed in a vinyl bag and sitting unmounted rather than being mounted to the base of the amp?

Secondly, when looking at replacement tanks for a PRRI I see several recommendations for 'MOD' brand tanks but model numbers listed often suggest a tank much shorter than the 17" stock pan. Almost half the length. Does length of the pan have any bearing on how well it does or does not perform?

Peegoo
Contributing Member
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Eat. Sleep. Guitar.

Repeat
Aug 18th, 2016 01:04 PM   Edit   Profile   Print Topic   Search Topic

They are in a bag to keep dust bunnies and spiders out because anything (even as light as a spider web) in contact with the reverb springs will deaden the vibration of the springs and negatively affect the sound of the reverb.

The metal pan itself is not attached to the cabinet in order to help keep it as independent of the cabinet as possible. There are usually a few screws through the edge of the vinyl bag into the wood. On modern amps, the pan has soft rubber isolators on the screws that mostly block the cabinet's vibrations and prevent them from reaching the reverb springs.

Also aiding this is the pan is actually the suspended portion of the reverb unit; the entire thing is called a "pan," but it's actually a metal box with an internal pan, suspended in place by four soft springs. Inside that pan are the send and return transducers, connected by two or three long springs.

The reason for all this acoustic isolation is the pan is a sort of microphone: the return transducer is an electromechanical device; it's designed to sense motion in the springs, convert that motion to an electrical current, and feed it back through the reverb recovery circuit to be amplified by the amp's power stage.


The length of the pan is not as critical as the number of turns (and tension) of the springs in the pan. Done properly, a short pan can sound just like a longer pan (generally) as long as the reverb springs have the same number of turns as the long-pan springs.

amphead4
Contributing Member
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Cincinnati, USA

Aug 18th, 2016 01:15 PM   Edit   Profile   Print Topic   Search Topic

Pans aren't all that expensive so you might take a chance and try a six spring pan in place of the stock four spring pan.

(Yeah, I know it looks like it only has two springs but each one counts as two - one on each side of that bead near the middle.)

They also come in short, medium and long delay so there's lots of experimenting to do, if you are so inclined.

I have always assumed the long pans sound better than the short ones simply because BF and SF amps have better reverb than say a Blues Jr, IMO. But I've never bothered to test long versus short in the same amp to prove it to myself.

Rob Jai

Calif Cap City

"Jai" pronounced "J"
Oct 27th, 2016 06:05 PM   Edit   Profile   Print Topic   Search Topic

So, the reason for my initial question is that I bought a used Princeton Reverb, Special Edition. The one with the wine colored tolex and 12" speaker.

The reverb in this amp didn't seem to be working. Thinking that maybe I had a bad pan in it, I changed the pan to a Mod brand pan and while I now have some reverb, it also doesn't sound like much. Evem with the reverb dial turned up all the way (I would generally not go over 4) the reverb still sounds weak. It's hard to describe, but it sounds kind of nasally and has very little trial at the end of the played note or chord.

I have previously owned a DRRI and thought that the reverb in it was nice and expected this PRRI would be nice too. It's NOT - at least not right now.

Could it be that I have a bad tube? Would a tube affect reverb and if so, which tube should I be looking at?

More often than not I play through a reverb pedal but it would be nice to have on board reverb that sounded decent and I think that this amp should be able to provide that. There's gotta be something wrong.

willie
Contributing Member
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Too Near Atlanta GA

Amp Tech Emeritus
Oct 28th, 2016 02:37 PM   Edit   Profile   Print Topic   Search Topic

That amp should have too much reverb if anything...you have a tube or component issue most likely.

Nice explanation of "the bag" btw Peegoo :)

w

Rob Jai

Calif Cap City

"Jai" pronounced "J"
Oct 28th, 2016 03:37 PM   Edit   Profile   Print Topic   Search Topic

Thanks Willie and yes, Peegoo's explanation was a good one.

I guess I'll try another AT7 tube. I "think" that's the one that affects reverb. I've already changed the pan and assume that the new one is fine. We shall see.

FDP Forum / Fender Amps: 1985 - Current / Princeton and Deluxe Reverb pans




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