I have an idea but I need some help!!!!!!!!!!!!!

[sevenisthenumber]

I want to put an additional 3pdt footswitch in my Bluesbreaker clone. What i would like it to do is switch between the normal volume and gain knob to a second volume and gain knob that i can set at different settings. Like having two bluesbreakers in one case. Ive heard this is possible using one pole to switch between the gain pots, one pole for the volume pots and the other for a bi color LED to show which one your using.
Can someone out their show me how to do this?!!!  I would much appreciate it!

Thanks

[Zben3129]

don't quote me on this, its late and Im probably wrong,

But if you connected the "input" of the pots (from signal, most likely an outer lug, sorry I don't know the shem) to the middle lug of a set of three on the switch, and then wired the pots in parallel off of the 2 other lugs and joined them where the path would be the same again, it should work.

After typing this, I realize how sucky a desription it is, so I am off to look at the schem, and I should have a pic in about 30 mins if all goes well of the setup

Zach

[Zben3129]

K...



So, for the pots, conect the unswitched lugs. This means wire the 1st and 3rd lugs of the gain pot together, and the 2nd and 3rd lug of the vol pot(maybe 1st and 2nd, it will be the unswitched lug, you should know what that is) together. For the LED, obviously don't forget to ground the appropriate pin
I
Hopefully this works, again no guarentees, Ill check back in the morning, when I can think straight.

Cheers

Zach

[Sock Puppet]

I can see problems with that but no elegant solution springs to mind.

The worst of it is the open feedback loop when the switch is changed over - loud pop. Then the effect on the gain of the second stage as the 100k pots are paralleled, unsure how much of a problem that would be.

Paralleling the volume pot ground (Vb here) will make them unuseably interactive in some positions - if one is turned down and the other turned up you'd have the signal from the 6k8 shorted out for instance.

The only kludge I can see that would do anything like work would be paralleled outer lugs on the pots at the output, wipers switched to the 0.1 capacitor  - and it's going to pop! think about that later ( will change the tone stack and level a bit (what happened to 220k/250k pots?) but a bit of tweaking the .01s there will take care of that if you don't like it).

Secondly connect the gain pot pin 1s together with one switch pole bridging the wipers, making the second pot dependent upon the gain setting of the first.

There goes my morning stream of consciousness blather, I hope I'm wrong.

Far better to make another - it would be an order of magnitude more versatile and above all would work properly.

S.

[sevenisthenumber]

I found this looking around!  This is what i want to do. the "dual channel" mod.
Any one know how?

http://www.wpa.net/~vaughn/ts9/vmod.jpg

[gez]

If I wanted to do this simply, the following might work OK for an additional 'drive'/'gain' pot:

I'd use a CMOS op-amp (minuscule input bias current) and stick a 10M resistor between its output and - input, to keep the amp biased between switch-over of the two pots.  The switching could be done with one half of a DPDT.  The wipers could be wired together and the switch selects between the 'free' ends.  With any luck, the insignificant bias current wouldn't cause any significant offset due to the 10M resistor, and switching would be quiet.

In a tubescreamer, for example, this would mean that the 10M would always be in parallel with one of the 500k pots; so the effective resistance at max gain would be around 476K, but you could always increase that 51K resistor to compensate.

Edit: the volume could probably be done simply too, but would need to know how you've done it.  Schematic?  Plus, a FET input amp might work OK too (would have to suck it and see).

[gez]

If I wanted to do this simply, the following might work OK for an additional 'drive'/'gain' pot:

I'd use a CMOS op-amp (minuscule input bias current) and stick a 10M resistor between its output and - input, to keep the amp biased between switch-over of the two pots.  The switching could be done with one half of a DPDT.  The wipers could be wired together and the switch selects between the 'free' ends.  With any luck, the insignificant bias current wouldn't cause any significant offset due to the 10M resistor, and switching would be quiet.

In a tubescreamer, for example, this would mean that the 10M would always be in parallel with one of the 500k pots; so the effective resistance at max gain would be around 476K, but you could always increase that 51K resistor to compensate.

Edit: the volume could probably be done simply too, but would need to know how you've done it.  Schematic?  Plus, a FET input amp might work OK too (would have to suck it and see).

Actually, the 10M probably isn't necessary.  In the tube screamer, I think I'm right in saying there's a small cap from output to input.  The charge on that would probably keep a FET input op-amp biased between switch over.

[Sack Puppet]

I agree with Gez.

I also think two individual pedals make this thread history.

So I'd like to point out that we're talking about ts-9-possible mods to a home brew Bluesbreaker and the solution looks like it's going to be more complicated than the versatile 2xindividualpedals. If you stare at the ts9 schematic and bear in mind the original question then the way to do the mod becomes apparent because it's a different pedal altogether

Sorry no links, I'm trying to get to bed,

S.