Fender Reverb Mods

[Richard]

I have a Super Reverb Reissue and am considering modding the reverb. I would like a subtler, smoother reverb, not the super boingy attack. Would swapping the 12AT7 in V3 for a 12AY7 or 12AU7 do anything for me? I could also splice a tone control or volume control in the cables to and from the tank or possibly dampen the springs. I'm mainly asking in case any of this is a bad idea, these all seem non-invasive and I'm probably not that interested in any permanent mods.

[Steve A.]

I have a Super Reverb Reissue and am considering modding the reverb. I would like a subtler, smoother reverb, not the super boingy attack. Would swapping the 12AT7 in V3 for a 12AY7 or 12AU7 do anything for me? I could also splice a tone control or volume control in the cables to and from the tank or possibly dampen the springs. I'm mainly asking in case any of this is a bad idea, these all seem non-invasive and I'm probably not that interested in any permanent mods.

For a smoother reverb I would replace the R26 1M resistor with a 1M trim pot. That will allow you to dial back the input to the reverb circuit, like the Dwell control on an old Fender 3 knob outboard reverb unit.

To make sure that you have enough of an input signal instead of a 1M trim pot you could wire a 500k trim pot in series with a 470k fixed resistor to ground.

If you were looking for more reverb you could wire a 1M trim pot in series with the 470k fixed resistor. Or use a pot mounted on the rear panel instead of the trim pot.

http://www.amparchives.com/album/Fen...Schematic.html

Steve Ahola

[g1]

If you don't want to open the chassis up, try a 12AU7 in the reverb drive position, instead of the 12AT7.
That will tame the reverb a fair bit.

[Richard]

That's one option I am considering. According to the schematic there's 16VAC at the send to the reverb. This seems small enough that I could install a reverb tone control or volume in the send or return line and experiment with that. As a side note, I was playing a Vibro King the other day and I couldn't hear a difference between raising the dwell control vs raising the mix control, although the reverb seem weak compared to a standard Fender reverb.

[Steve A.]

That's one option I am considering. According to the schematic there's 16VAC at the send to the reverb. This seems small enough that I could install a reverb tone control or volume in the send or return line and experiment with that. As a side note, I was playing a Vibro King the other day and I couldn't hear a difference between raising the dwell control vs raising the mix control, although the reverb seem weak compared to a standard Fender reverb.

If you are referring to TP19 while the voltage of the AC signal at that point is 16.0VAC there is ~433VDC coming from power supply node Z. P-z-z-z-t!

The difference between the Dwell and Mix settings is most noticeable when you slam the reverb circuit with a strong signal.

Steve Ahola

[Richard]

Thanks for pointing that out, I should have been looking at TP20. Someday soon I'll rig up a test cable, I'll see if playing with the signal at TP20 does anything useful.

[Pedro Vecino]

For me the best system is adjusting the gain in the cathodes of the 12AT7. But this, depending on the response of the tank. Today, virtually no two are alike. This is my starting point.
With classic good sounding Accutronics tanks a resistor usually between 1K and 2K2 in series with the cathode capacitor (22uF) works very well. With MOD tanks (more intense effect and with more density), you can even remove the capacitor. In both cases, but more with the MOD, it´s preferable to use a brighter 12AT7. I always use Mullard ECC81 NOS, but also serve parallel models of Philips Holland, 12AT7 RCA and others.
Many times I do this selectable by a miniswitch under the chassis.

[Steve A.]

For me the best system is adjusting the gain in the cathodes of the 12AT7. But this, depending on the response of the tank. Today, virtually no two are alike. This is my starting point...

I think that the new tanks from China are terrible- it has gotten to the point where I usually prefer a well-designed digital reverb in a guitar amp.

Have you had any luck with electronic or mechanical modifications to make the modern Chinese tanks sound and respond more like the old tanks in the BF/SF amps?

The ability to fine-tune Fender reverb circuits to meet the needs of guitarists would be an amazing super power!

Steve Ahola

[Pedro Vecino]

I do not manipulate transformers in reverb tanks because I d´ont know the logic operation mechanically. I have seen good reverbs with dancing transformers and the same with transformers rigidly fixed. I made some attempt in desperate cases, but without results.
Sometimes in classic Accutronics with strange behavior (harmonics that do not correspond to the original note), if the effect is long enough, it works acceptably tighten the springs slightly. I separate the union in the center and short few millimeters on each side to re-unite in a straight line (without bulging at the junction) with a minimum drop (1mm3) of epoxy.
In others, if sounds dark and insensitive with clumsy tracking simply not use them.
For me the best are the MOD. Dark and with high density but with great sensitivity and good tracking. These support very well the treatment of the gain in the cathodes and also support if required reduce the value of the input capacitor slightly to make things easier.
Digital, I know those of the Marshall JVM, the Marshall Haze and little else. They are far from the classic Fender concept although I imagine there will be good reverbs in other models, closest to this idea.

[J M Fahey]

super boingy attack

That's the *spring* reverb sound, love or hate it ... and it's a "mechanical" problem.

1) damp the springs, which is what will have the most effect.
Pull the reverb tank out of its bag, put it on a table or chair so it can still be connected, face up so you see the springs, play a little with full reverb on to calibrate your ears and then drop a drop of machine oil in the middle of one of the springs, play, the a drop on the other by it, play, and so on.

Each drop will damp reverb and boinginess appreciably.

If you don't like what you get, pull oil with a q-tip; if you do pull oil anyway (this was just for testing) and add a tiny tiny piece of soft bathroom sponge (think matchhead size) here and there, jammed between spring turns without falling.

Can't give better instructions, it's very experimental but works.

Reverb tank spring *does* have some damping rubber inside the end support, inside the brass tubes, but after 10-20 years all revert to the boingy undamped type because rubber rots.

2) forget springs and get a nice Digital Reverb pedal ... obviously NOT the type which claims to faithfully reproduce boingy springs

Don't worry about Loops, upfront is fine on a classic Fender Reverb amp.

[loudthud]

In another thread Juan pointed out that the capacitor that is across the Tank return actually resonates with the tank inductance to form a treble peak. If the tank is not original, that cap may need to be adjusted. Experiment with the value to find what sounds best.

[Steve A.]

I actually had good luck screwing around with the ss reverb circuitry in the Crate V-18 (the stock reverb was absolutely terrible and many people were upgrading the tanks.) Basically took it from sub-par to just barely passable...

Steve

[Leo_Gnardo]

That's the *spring* reverb sound, love or hate it ... and it's a "mechanical" problem.

1) damp the springs, which is what will have the most effect.
Pull the reverb tank out of its bag, put it on a table or chair so it can still be connected, face up so you see the springs, play a little with full reverb on to calibrate your ears and then drop a drop of machine oil in the middle of one of the springs, play, the a drop on the other by it, play, and so on.

Each drop will damp reverb and boinginess appreciably.

If you don't like what you get, pull oil with a q-tip; if you do pull oil anyway (this was just for testing) and add a tiny tiny piece of soft bathroom sponge (think matchhead size) here and there, jammed between spring turns without falling.

Can't give better instructions, it's very experimental but works.

Reverb tank spring *does* have some damping rubber inside the end support, inside the brass tubes, but after 10-20 years all revert to the boingy undamped type because rubber rots.

2) forget springs and get a nice Digital Reverb pedal ... obviously NOT the type which claims to faithfully reproduce boingy springs

Don't worry about Loops, upfront is fine on a classic Fender Reverb amp.

Cool! Juan shares his spring "tonics".

If you've had it with boinky spring reverbs, besides pedals there's some good old reverb boxes available reasonably cheap, for instance "MicroVerb" and the very swanky LXP-1. Ignoring any pretentions to impedance matching, I've used these as substitutes for spring reverbs in Fenders to very good effect, plugged into the jacks that ordinarily go to/from the tank. If you're game to try this sort of thing, just make sure your reverb is dialled full "wet". These gadgets also have handy DDL & chorus & flange effects too. Plug & play & dial & smile!

[Pedro Vecino]

When Steve mentioned digital reverbs, I thought he was referring to the integrated in commercial tube amplifiers. I know well the Alexis (Micro, Midi, Quadra ...) and Lexicon LXP´s. Each has its own color and its special features but is not what I associate to the "real" Fender reverb when it does things right (a truly inspiring sound). But I never tried through the original circuit itself...

In another thread Juan pointed out that the capacitor that is across the Tank return actually resonates with the tank inductance to form a treble peak. If the tank is not original, that cap may need to be adjusted. Experiment with the value to find what sounds best.

This capacitor (2200 pF) is not on the reissues Twin, Deluxe, Vibro and Super Reverb.

I actually had good luck screwing around with the ss reverb circuitry in the Crate V-18 (the stock reverb was absolutely terrible and many people were upgrading the tanks.) Basically took it from sub-par to just barely passable...

I know the V33, with the same or similar reverb circuit. These circuits through a 220K resistor just before the driver have never promised anything good. Usually long and plain with poor tracking. With a large tank (Belton 9EB2C1B, if I remember correctly) and some adjustments acquire more dimension and are more usable but very far from a traditional Fender reverb.

[Justin Thomas]

Maybe part of why we stick with that old Dino-Tech Springy Reverb is the thrill of the chase of the perfect verb sound... each one is unique in its own way as parts drift and things sag... And we can do things ourselves tone is them... whereas pedals, chips, etc. are much more consistent, but every verb sounds like every other verb...

Justin