On/Off Switch Stompbox

[elinter]

I have a Fender Frontman 15R amp.  It has a push button on the front panel that engages/disengages the overdrive.  I would like to modify the amp to replace the button with a stompbox.  I'd like to put a 1/4 in female jack on the back of the amp and build a simple on/off stompbox.  This link http://www.mrgearhead.com/faq/schematics/fender/Frontman%2015G%20Schematic%2068F.pdf has the circuit schematic that showes the push-button.  

Is this doable?  Can someone explain how to do this?

Thanks,
Mike

[Paul Marossy]

It's hard to tell looking at the schematic. If that footswitch controls a relay that changes "channels", then it won't be possible. If it uses a strandard DPDT switch, then it would be possible. Just replace the section that would normally be switched in the amp with your stompbox circuit. Beware though, it may not work at all like you expect it to - it could be very noisy. I tried doing something similar with my Seymour Duncan Convertible, but it failed miserably...  

[bigjonny]

Your amp simply has a DPDT that toggles the drive/normal channel.  This means that if you want to move your switch 20' away from the amp, you'll have to run your preamp signal through 40' of cable.  Not an acceptable solution.

You'd have to replace the DPDT with a relay DPDT.  If you build stompoxes, this probably isn't too diffcult (I say this having NOT seen the interior of your amp).  However (disclaimer), please do ensure you understand the risks of opening an amp (e.g. death).

Relays often are just DPDTs that are activated by a control voltage.  In many cases, it can be like how you light an LED in a stompbox: provide a path to ground, and the relay "flips" or the LED lights up; open the path, and the Voltage stops flowing, and the (non-latching) relay returns to its previous state, or the LED goes out... So, the clever will note you can turn an LED on at the same time as flipping a relay quite easily in this case.

The only trick is that you'd have to find 25-50V to power the relay.  It looks like you have +/-23VDC on your power supply, so it is potentially possible, but at this point we're beyond my current understanding of amps.

I fiured all this out to mod my Prosonic Amp.  See the Prosonic schematic, and try to decifer how the footswitch activates the relays.  HINT: the footswitch is just two SPST switches that independtly open and close a connection to ground.

See R.G.'s article about relays. for more info.

*edited* to correct the (now different) link to the Prosonic Schematic.

[Paul Marossy]

I think you're right, that appears to be a standard DPDT switch. Aside from getting a relay to work, my biggest concern is how noisy that whole arrangement would be and if you would have any popping noises due to switch bounce. If it were me, I wouldn't bother with it, but go for it if you feel so inclined.  

[bigjonny]

my biggest concern is how noisy that whole arrangement would be and if you would have any popping noises due to switch bounce.

O ya.  I forgot to mention that.  The pop.  I meant to.  Could be a problem.  Thx Paul!

If it were me, I wouldn't bother with it, but go for it if you feel so inclined.

Ya, I'll have to agree w/ Paul on this one.  Just build a BSIAB II, or some other awesome distortion pedal, and ditch your amp's dirt channel.  That sounds like a better return on your effort to me.

Unless you're playing a Pro Tube line Fender amp, Fender's distortion channels (to me) tend to sound pretty lousy.

[bigjonny]

O ya -

Should you decide you MUST go the route of relays, I believe NEC part #ED2-5NJ will suit your purposes.  This is what Zinky recommended to replace relays on the Prosonic, and as I recall, they would work on +23VDC.  This is an ASSUMPTION based on memory, however.  Read the datasheet before you commit to installing one.

[elinter]

Chalk it up to ignorance...how hard could it be to replace one switch with another...  Oh well, I do appreciate the great feedback.  

Think I will try building a separate pedal...agree its a better return on effort.

Thanks!