Relay and switching questions

[Colossal]

I'm trying to wrap my brain around the best way to handle some switching issues and was hoping to see if you guys had some ideas how to go about it. I'd like these options to be foot switchable and have been perusing the various Dumble schematics for insight into adapting 5V relays for this purpose.

Here's what I'd like to do:

<u>1) Switchable Lead/Crunch/Clean</u>
This would just be a 3-way switch which simply chooses between a 1MA pot, a 100kA pot, and a straight "through" connection (no resistor). I'd like there to be 3 footswitches for this such that one overides the other two when pressed. An LED would be used to illuminate the active setting on the foot switch box. There is no real "channel" switching here, just switching the pathway between three possible resistive choices.

<u>2) Switchable preamp boost</u>
This would be nothing more than a 1MA "raw" control which, when switched in, allows the degree of tonestack bypass to be selected via a pot. When off, the 1MA pot is out of the picture and the tonestack is normal. This is just On/Off via a relay. I would use a Dumble relay setup as a template.

<u>3) Switchable mid boost</u>
This would be nothing more than bypassing an extra cap inline with the treble cap a la Dumble mid boost. This is pretty straightforward and I am planning to adapt the Dumble approach.

So, in summary, I'm mostly wondering how to do Item #1 and if this whole arrangement could be done using a typical 5-pin XLR jack or something similar. Just trying to sort out the best way to achieve #1 while not getting overly complex. If I have done that already, well, I accept the challenge! I have a 5V source for a regulated PS.

Thanks, in advance, for any help with this.

[Ears]

See "other stuff"
http://www.valvewizard.co.uk/
His example on channel switching should do 1).

With a little thought you might also add LED annunciation on the amp as well as on the ft-switch, house the logic in offboard ft-switch enclosure and the relays (with their drivers) in the amp.
Requires 5 conductor cable to the footswitch for the 3 channels.

[Colossal]

See "other stuff"
http://www.valvewizard.co.uk/
His example on channel switching should do 1).

Thanks Ears! I had read this very page on the venerable Wizard's site once a long time ago and completely forgot about it. Thanks for repointing it out. Yes, this looks like it could do it. The latching footswitch circuit which defeats the other two "channels" is <i>exactly</i> what I am after. Ampdoc is also giving me a hand with this.

With a little thought you might also add LED annunciation on the amp as well as on the ft-switch, house the logic in offboard ft-switch enclosure and the relays (with their drivers) in the amp.
Requires 5 conductor cable to the footswitch for the 3 channels.

LEDs above the Clean, Crunch, and Lead level knobs on the front face of the chassis would be a cool feature. I'll have to study Merlin's drawing ...the switching stuff is pretty new for me...

Thanks again!

[harryk]

Hi! I do not want to hijack this thread but I have similar problem with three channel tube preamp. I already have a logic controller to steer Vactrols or relays for three channels. I have normally used realys for channel switching but now I am intenting to go Vactrol way. My problem is how those Vactrols should be connected to input stage to get all three channels work perfectly and independently. With relays it is easy because relays connect unused channels completely away from signal chain. Vactrol is a optocoupler which does not work like relays. Any ideas how this problem could be solved?? I have three individual preamp channels wtih own voicings and own eqs etc. That is why I would not like to use a common one tube buffer stage. Harry

[ampdoc1]

harryk.

Most commercial amps that incorporate vactrols, use them in pairs. One is in series with the audio signal, and the other fun from the same point to ground. They are switched in reverse. When you want signal flow, the series vac is on, giving minimum resistance to the signal, while the grounding vac is off, giving a high resistance to ground. While you do not get an absolute ground, the combination provides enough attenuation to work well. See the Rivera Knucklehead on Amp Heaven for an example.

ampdoc1

[harryk]

Thanks! I was assuming that it would be something like that but I want to hear other people opinions. I will study that method and try it to my three channel project. Harry