Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: fingersoccer on June 13, 2016, 04:24:06 pm
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I'm starting a Deluxe Reverb build and I'm looking for a way to switch the reverb on/off using a foot pedal. I know I can just connect a 1/4" cable to a jack that grounds the reverb circuit, but I've read that you need to keep the cable as short as possible to avoid unwanted noise getting into the signal path. It seems like a better way to do that would be via a relay, so the reverb signal never actually goes through the cable.
However, I've read that relays can sometimes chatter and cause distortion when an amp is so loud that it vibrates the relay's contacts. Is there an alternative switching method that would allow the reverb signal to stay entirely in the amp and withstand vibrations?
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Fender has been successfully using a real footswitch for over 50 years. Gotta use a shielded cable for the reverb.
But, if you want to 'improve' on that, you could use a vactec VTL5C1 opto switch. Connect the switch terminals across the reverb tank return jack (just like the regular footswitch jack). Build a simple 5VDC supply powered from the filament circuit. Switch the dc to the LED inputs on the opto switch. Hoffman has everything needed on this page...
http://hoffmanamps.com/MyStore/perlshop.cgi?ACTION=enter&template&thispage=Lamps&ORDER_ID=!ORDERID!
(http://hoffmanamps.com/MyStore/perlshop.cgi?ACTION=enter&template&thispage=Lamps&ORDER_ID=!ORDERID!)
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This is just a general comment about foot switches. I seldom have issues with simple foot switches and when I do they are simple to repair. I have on the other hand had serious problems with Mesa Nomad 45 foot switches which are very complex. They are full of ICs and control a bunch of relays and are not simple to repair at all.
As sluckey said Fender has been done well with simple foot switches for years. A Deluxe Reverb is a great amp and there is not much reason to reinvent the wheel. My advice is to build it in a standard way and play it for a while. If at some point in the future you don't like something, that is the time to consider a change.
I have not given it much thought but some sort of optical switch could be made to work with no moving parts. Someone smarter than me may chime in on that idea.
Cheers,
Billy
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> I've read that ...cable ...short
> I've read that relays can
You can read anything you want in the interwebs. Idiots don't even need to type to spew hogwash anymore... I was startled how well Google/Android voice-recognizes.
Agree that Fender's begging-for-hum cable HAS worked OK, and is maybe the only part of a g-amp which hasn't needed "upgrading" (until cheap logic led to more-and-more switch functions to impress buyers with unmaintainable gizmos).
However if you must lipstick this pig....
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Thanks for the thoughtful replies. I've never used a reverb footswitch before, so if the shielded cable version isn't noisy enough to worry about, then I guess there's not much point, as Pianobilly said, in reinventing the wheel.
If I decide to use a replay later, it looks like Hoffman has a helpful article about connecting relays (http://el34world.com/projects/relay_switch.htm) (and PCB + parts).