fender style reverb footswitching

[eddie25]

Is there a more clever way to do foot-switching for a fender AB763 style reverb that doesn’t involve making the foot-switch cable a really long grid wire when the reverb is on?

Perhaps instead using a switching jack in the reverb recovery triode’s cathode ground path?

[Gaz]

It's definitely old-fashioned, but I think the original's fine, which is why it's been used for so long. You could move it to the output of the recovery stage since singal-to-noise ratio will be better there. I personally use relays, but that's mainly because I want to have an LED indicator on the pedal.

If I understand your idea, then I don't think it's a great plan because it lifts the cathode from ground completely, which I have read can reduce tube life.

I know Garnet has a scheme in his book where he uses a negative voltage to send a preamp tube into cut-off, giving the same effect (a mute), but I think that's just as much trouble as a relay.

[eddie25]

Thanks for the response. As it is now, the foot-switch is definitely adding a ton of noise. My jack is a lot farther away from the reverb input to the amp than fender does it, so that could be part of the issue, but I know others who have had this problem with a real fender as well. I have some experimenting to do I suppose.

[Milkmansound]

my amps use the old fashioned Fender method

if you get it right, it does not add any noise at all

also - make sure you are using a shielded footswitch cable because an unshielded one at that length will be injecting christmas carols into your amp

play around with the layout and grounding until the circuit is dead quiet and then pop the footswitch in and see if it adds noise

[eddie25]

You could move it to the output of the recovery stage since singal-to-noise ratio will be better there.

Great idea, this seemed to do the trick, I just ran a wire from the input of the reverb pot to the foot-switch jack. Much less noise!

I know Garnet has a scheme in his book where he uses a negative voltage to send a preamp tube into cut-off, giving the same effect (a mute), but I think that's just as much trouble as a relay.

Do you have this book? How is it?

[eddie25]

my amps use the old fashioned Fender method

if you get it right, it does not add any noise at all

also - make sure you are using a shielded footswitch cable because an unshielded one at that length will be injecting christmas carols into your amp

play around with the layout and grounding until the circuit is dead quiet and then pop the footswitch in and see if it adds noise

First thing I tried was shielding the wire run from the amps reverb input to the foot-switch jack, and it was basically no change. It might just be that long run though, it's about 7 inches. I see that your amps are set up like fender where the foot-switch jack is basically right next to the reverb input jack, I wonder if that is the key.

Perhaps it's my foot-switch as well, I would be surprised if it's not shielded though, it's the generic double switch from AES. But anyways, grounding the recovery stage output seems to be working pretty well.

Thanks guys!

[martin manning]

Don't know about the two-button, but the three-button foot switch I bought from AES did not have shielded cable. They sell a Fender replacement that probaby does.

[Milkmansound]

it might be the key - the jacks are bussed together and ground to the chassis very close to there they live

I think a good rule for reverb circuits is to compact them as much as possible - they are terrible for picking up noise and can really ruin an otherwise beautiful sounding amp circuit if not done perfectly

[eddie25]

Don't know about the two-button, but the three-button foot switch I bought from AES did not have shielded cable. They sell a Fender replacement that probaby does.

That would be a major bummer, I gotta tear the feet off to check. I was just looking at it thinking "there's no way this wouldn't be shielded."

it might be the key - the jacks are bussed together and ground to the chassis very close to there they live

I think a good rule for reverb circuits is to compact them as much as possible - they are terrible for picking up noise and can really ruin an otherwise beautiful sounding amp circuit if not done perfectly

I hear ya. It's was just that one wire to the switch jack that was out of place, and with my shielded wire test making zero difference I feel like it might not be a layout issue in that respect.

[eddie25]

... and it's not shielded. SIGH.

[FUCHSAUDIO]

use a relay.

[bcmatt]

I didn't even realize there was a solution to non-relay reverb footswitch noise.
I have a couple Traynor YGL-3as that I never plug a footswitch into for the reverb...only do the trem. Then I just built a 6G15 unit and had the same noise issue if I try to use a footswitch. I just assumed no one uses footswitches with these things, because they are dead quiet otherwise....

so it is possible? Maybe I should mess around with them... if I learn anything from this thread...

[renshen1957]

Do you have this book? How is it?

Hi,

The Garnet book is excellent, full of ideas and examples besides the usual suspect from Fender, examples of different brands types of reverbs, tremolos
and a variety of other ideas.

However, every circuit is in schematic form. A ton of Garnet amp schematics, too.

Best regards,

Steve

[Gaz]

... and it's not shielded. SIGH.

No worries, that's an easy fix, right? - just get a new switch. I'm sure you'll have a project down the road to use the other one. The Garnet book is interesting by the way, and Garnet comes off as being very humble and open minded in his writing. Cool to get his perspective. Wish Fender and Bran had written books...

[Firestorm]

In Fender amps I've worked on, problems are almost always frayed shields on reverb tank or switch cords or getting the switch plugs in backwards. The reverb switch side is grounded, the "vibrato" side is not. Those two wires cannot be inside the same shield, either. In original Fender footswitches, the metal switch housing is soldered to the shield, which quiets it up to. Fender tanks themselves are also grounded at only one end (output) which I guess prevents a possible ground loop. If everything is right, they're pretty quiet, but there are a lot of things to get wrong. (Well not a LOT).