Dual Reverb in a Fender Twin!

gregsk777 · 05-03-2009, 04:43 AM

I have had this idea stuck in my head for a while.

Would it be possible to install two separate reverb pots in a Twin Reverb that I could switch between using a SPDT switch or better yet a foot pedal?

This way I could go between subtle reverb to more intense "cranked to 10" full on reverb in the middle of a song.

Thanks, Greg

Chuck H · 05-03-2009, 10:28 AM

You could probably do it by simply building a modified pedal. The pedal for the reverb in your amp just grounds the signal. If you built a special pedal you could use a resistor to "half ground" the reverb. Thus reducing the output. So you could set a higher reverb level and then reduce it with the pedal rather than shutting it down. If you built the pedal with two switches you could have a kill and a half power button. If you wanted to get really jiggy with it you could use a pot on the pedal to adjust the amount of attenuation that takes place when that button is pressed.

Chuck

gregsk777 · 05-03-2009, 08:27 PM

Thanks Chuck, Interesting idea!

What kind of resistor would you recommend? Also if I were to use pot instead would I use a 100K linear pot just like the reverb pot in the twin or something else?

Enzo · 05-04-2009, 04:35 AM

Experiment and find out. get a pot from your drawer. 100k, 500k, 1M, doesn't matter a lot. Get a hunk of cable with an RCA male on one end - like snip the other end off a patch cord. Wire the cord to the center leg and one end leg of the pot. Plug that cord into the reverb footswitch jack. Now the pot is a variable resistor across the reverb signal. Don;t worry right now if it adds some hum or something, we are just checking the concept. Dial the pot up and down to se if it alters the reverb level in any useful way.

Remember you proposed a hi/lo switch, so all we are looking to do is see if there is some reduced level we can use with a resistor. Start with this unplugged and set the amp up to play with a high level of reverb. Even set at its highest, just plugging a 100k resistor into the jack might reduce your level, a 1M a lot less. Once you have established the max level, then pplug it in and start fiddling.

If you find a setting on the pot that reduces the reverb level to something you'd like when compared to full on, then unplug the thing and measure the resistance at that setting. You can then wire a resistor of similar value into a switch.

gregsk777 · 05-04-2009, 05:45 AM

You are right Enzo. Experimentation is key! I have to start small and think big!
Keep you updated on my progress.

Thanks, Greg

Chuck H · 05-05-2009, 04:40 PM

I'm thinking something like this:

gregsk777 · 05-06-2009, 01:25 AM

Interesting! Thanks for the schematic!

What would happen with both switches engaged? Would I theoretically get a third reverb option?

Chuck H · 05-06-2009, 03:04 AM

No, that's why that switch is marked "kill" on my schem. When that switch is engaged there will be no reverb no matter what position the second switch is in.

So it's one switch that chooses between two reverb levels. The higher of the two being selected by the "reverb" control on the amp and a second lower level chosen by a pot on the pedal and engaged by a switch on the pedal. And there would be a second switch on the pedal that mutes the reverb altogether any time it is engaged.

So technically there would be three levels. If "none" is a level.

Chuck

05-03-2009, 04:43 AM	#1
gregsk777 Junior Member Join Date: May 2009 Location: MA Posts: 13	Dual Reverb in a Fender Twin! I have had this idea stuck in my head for a while. Would it be possible to install two separate reverb pots in a Twin Reverb that I could switch between using a SPDT switch or better yet a foot pedal? This way I could go between subtle reverb to more intense "cranked to 10" full on reverb in the middle of a song. Thanks, Greg

05-03-2009, 10:28 AM	#2
Chuck H Old Timer Join Date: May 2007 Location: pacific north west Posts: 1,477	You could probably do it by simply building a modified pedal. The pedal for the reverb in your amp just grounds the signal. If you built a special pedal you could use a resistor to "half ground" the reverb. Thus reducing the output. So you could set a higher reverb level and then reduce it with the pedal rather than shutting it down. If you built the pedal with two switches you could have a kill and a half power button. If you wanted to get really jiggy with it you could use a pot on the pedal to adjust the amount of attenuation that takes place when that button is pressed. Chuck Last edited by Chuck H; 05-04-2009 at 08:12 AM.

05-04-2009, 04:35 AM	#4
Enzo Senior Member Join Date: May 2006 Location: Lansing, Michigan, USA Posts: 10,258	Experiment and find out. get a pot from your drawer. 100k, 500k, 1M, doesn't matter a lot. Get a hunk of cable with an RCA male on one end - like snip the other end off a patch cord. Wire the cord to the center leg and one end leg of the pot. Plug that cord into the reverb footswitch jack. Now the pot is a variable resistor across the reverb signal. Don;t worry right now if it adds some hum or something, we are just checking the concept. Dial the pot up and down to se if it alters the reverb level in any useful way. Remember you proposed a hi/lo switch, so all we are looking to do is see if there is some reduced level we can use with a resistor. Start with this unplugged and set the amp up to play with a high level of reverb. Even set at its highest, just plugging a 100k resistor into the jack might reduce your level, a 1M a lot less. Once you have established the max level, then pplug it in and start fiddling. If you find a setting on the pot that reduces the reverb level to something you'd like when compared to full on, then unplug the thing and measure the resistance at that setting. You can then wire a resistor of similar value into a switch. __________________ Education is what you're left with after you have forgotten what you have learned.

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05-03-2009, 08:27 PM	#3
gregsk777 Junior Member Join Date: May 2009 Location: MA Posts: 13	Thanks Chuck, Interesting idea! What kind of resistor would you recommend? Also if I were to use pot instead would I use a 100K linear pot just like the reverb pot in the twin or something else?

05-04-2009, 05:45 AM	#5
gregsk777 Junior Member Join Date: May 2009 Location: MA Posts: 13	You are right Enzo. Experimentation is key! I have to start small and think big! Keep you updated on my progress. Thanks, Greg

05-06-2009, 01:25 AM	#7
gregsk777 Junior Member Join Date: May 2009 Location: MA Posts: 13	Interesting! Thanks for the schematic! What would happen with both switches engaged? Would I theoretically get a third reverb option?

05-06-2009, 03:04 AM	#8
Chuck H Old Timer Join Date: May 2007 Location: pacific north west Posts: 1,477	No, that's why that switch is marked "kill" on my schem. When that switch is engaged there will be no reverb no matter what position the second switch is in. So it's one switch that chooses between two reverb levels. The higher of the two being selected by the "reverb" control on the amp and a second lower level chosen by a pot on the pedal and engaged by a switch on the pedal. And there would be a second switch on the pedal that mutes the reverb altogether any time it is engaged. So technically there would be three levels. If "none" is a level. Chuck

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