Anyone know a simple starved voltage mod for tubescreamer?

[paultheoneyoulove]

Hello.
The other day, my 9v battery ran out, but right before it did, my tubescreamer gave this mad fuzzy, super compressed tone. Is there a circuit I could build to control the voltage coming from the battery or from a battery clip adapter for a one spot that would let me control the voltage? Sort of a variable resistor, where full on it lets all 9v through and full off it lets none through? I don't want to risk screwing with the guts of the circuit, hence the battery clip idea... In my head, a simple variable resistor with a couple of battery clips attached to pop it on the circuit would work, but I'm not an electronics expert! Cheers

[ragingben]

You should check the Beavis Audio Devolt. It is super simple. Or you could easily add another pot to your pedal that does the same. I have a schematic for my 'Bomb Idea' pedal on my site here which is essentially the same but with a voltmeter screen incase you wanted to build one with a display. TS style circuits starve really well, my favourite pedal to starve is the Digitech Bad Monkey, it gets really velcro-y at around 3-4v, it's the reduced headroom of the opamp clipping.

If you wanted to build the control directly into your TS you would just need a 10k linear pot and a 2.2k resistor (use 1w rather than a 0.25w). Find the + wire that runs from the 9v dc input to the circuit board and desolder it from the dc input and connect it to lug 2 of the pot, so the pot is connected to the circuit board. Connect lug 3 to the dc input where you just desoldered the wire from. Then connect the 2.2k resistor to lug 1 of the pot and to any ground point, probably the sleeve of the input jack. The resistor sets the minimum voltage, 2.2k will give you a minimum of around 1.6v, you don't want to go much lower. To raise this value use a bigger resistor, but 1.6v minimum is a good amount.

[Sporky_McGuffin]

On the Valvesporkers I just put a 10k pot in line with the 9v supply. Well, it was actually a 15v supply but that doesn't make much difference. Ben's approach works too - his is more of a voltage starve where mine's more of a current starve but the two are related and probably sound the same.

[ragingben]

Yeah, that's a great point from Mr McGuffin. I've only ever done voltage starve but I noticed Beavis Audio has both versions on their site.

[Sporky_McGuffin]

I think I'd be mildly surprised if the two sound noticeably different.

[alexjhh]

Not the way to go about doing it, but I used to stick batteries in my reverb pedal for a bit and leave them on so I could put them in my bad monkey afterwards. It sounds fantastic.

[ICBM]

I think I'd be mildly surprised if the two sound noticeably different.

I would think the only difference is that the voltage divider wastes more battery power by sending some current down the lower part of the track to ground. You still have the same voltage at the circuit power input and the same series resistance to the battery, either way.

[erictheweary]

Sure I've seen some power supplies offering a starved option. Danelectro do the Dan Electrode which is a 3 to 9v variable supply exactly for this purpose and is pretty cheap. However, as far as I can see, it only comes as a US style plug. So, probably no use at all.
http://ultimatemusicdirect.net/index...roduct_id=3487

[paultheoneyoulove]

You should check the Beavis Audio Devolt. It is super simple. Or you could easily add another pot to your pedal that does the same. I have a schematic for my 'Bomb Idea' pedal on my site here which is essentially the same but with a voltmeter screen incase you wanted to build one with a display. TS style circuits starve really well, my favourite pedal to starve is the Digitech Bad Monkey, it gets really velcro-y at around 3-4v, it's the reduced headroom of the opamp clipping.

If you wanted to build the control directly into your TS you would just need a 10k linear pot and a 2.2k resistor (use 1w rather than a 0.25w). Find the + wire that runs from the 9v dc input to the circuit board and desolder it from the dc input and connect it to lug 2 of the pot, so the pot is connected to the circuit board. Connect lug 3 to the dc input where you just desoldered the wire from. Then connect the 2.2k resistor to lug 1 of the pot and to any ground point, probably the sleeve of the input jack. The resistor sets the minimum voltage, 2.2k will give you a minimum of around 1.6v, you don't want to go much lower. To raise this value use a bigger resistor, but 1.6v minimum is a good amount.

This sounds pretty much perfect, and even better if I can do it via modding the 9V input. I might even be able to have it external, so it would sit next to the Route 66 with a digital readout. It was the main Fuzz Factory sound that I love so much, but from a starved TS! Lovely. I'll look into having a current starve, too, whichever works out easiest and...Well, the readout does sound cool...