Bypass Potentiometer?

[subvader12]

Hello everyone! Me again, I have a question about making a potentiometer (Drive 10k) still pass signal (in this case, voltage) but in a minimum part, I'm not sure how to approach this without adding more parts or is it necessary making a modification, as currently pins 1 and 2 of pot are connected and 3 is the output signal, but when I turn it down it just cuts off.

I was thinking of having a parallel resistor of lesser value, but that would make the pot value lower also, any way to make the voltage still pass in lower value but not totally cut off? Any help appreciated!

[patrick398]

Wouldn't it be better to have the 'drive' control be a pot from emitter to ground to vary the gain? I think with the current arrangement you're adjusting the bias of the transistor which is possibly what's causing you to lose signal.
Someone will be along to correct me shortly 

[Fancy Lime]

Hi subvader12,

I would gladly help but I am not sure I understand what you want to do. Do you want to set a minimum or maximum resistance even if the pot is already at minimum or maximum?

Also: The "drive" pot in your schematic actually sets the bias of the stage as well as the amplification factor. Depending on what you want to achieve, there may be better ways to do this.

Cheers,
Andy

[Fancy Lime]

Also, what I forgot to mention: If the pot is set to 0, your transistor will get too much current and get destroyed.

[subvader12]

Well the emitter pot seems to make more sense now that you mention it, I'll try it with a protoboard and see how it turns out.

Also to answer to Fancy Lime yes, I want to still have signal when I turn the pot all the way down but not so dirty, will it be achieved like that with the pot at emitter to ground?

[Fancy Lime]

Yes, making the emitter resistor into a pot would be better. But there is a better way still. Have a loog at Tim Escobedo's Legendary Circuit Snippets:
http://www.jiggawoo.eclipse.co.uk/guitarhq/Circuitsnippets/snippets.html
Scroll almost all the way down (3rd from the bottom) to where it says "Utility Boost". The BJT version is pretty much the best and easiest solution to your question. It goes from gain=1 to the maximum gain that the transistor is capable of (minus the feedback through the 2.2M resistor, but that is not much and you can use a 2.7M here as well). Just add your clipping diodes and the "Vintage" switch.

Hope that helps,
Andy

[PRR]

> I want to still have signal when I turn the pot all the way down

You want a Series resistor. Not Parallel.

So the pot turns down, not to Zero, but to maybe 2k. Add a 1.8k or 2.2k in series with the pot.

As others say, your current consumption goes way up when this resistor gets way small. The more polite way to reduce gain in this affair is to increase the emitter resistor.

[subvader12]

Fancy, I've tested the part you mentioned and it works perfectly, thanks for giving me this idea and now I can say my overdrive is complete!

Thanks everyone for your time. Let's just leave this here so others can make use of that page.