Question to circuit designers

[H4T]

I'm just curious, why do the circuits for pedals out there almost always call for the use of a 3PDT switch? Why not put the indicator LED into the pedal circuit and allow the use of a less expensive DPDT footswitch?

[antojado]

If you do a search you'll find a ton of info on the "millenium bypass" which does just that. However, you can get 3PDT switches for as little as $4-$6 a piece so they're not really more expensive and there's less parts and wiring.

[Pushtone]

Good question. I don't think the Millennium counts as being "in the circuit", but that is one way.

How about using one side of a dual op-amp to run an LED?
I think this is how the Tonebone pedals do it and they use DPDT switches.

So if you have a circuit with an single opamp, use a dual and use the free side to power the LED.
It may flash to the rhythm of your pick attacks but that might be cool.
Does anyone think this might work?

I haven't asked this because 3PDT switches are easy and it's a good way to support Aron and the forum.

[R.G.]

When I first looked into them, 3PDT switches were $20 to $25 each, and DPDTs were $6.

3PDT is a straightforward way to do this, and when the prices on 3PDT dropped to $4, it became hard to convince anyone that it was worth the components to use a $3 DPDT and a Millenium Bypass.

Non-Millenium-Bypass setups were also less than satisfactory in terms of performance.

[Tubebass]

Pushtone wrote:
So if you have a circuit with an single opamp, use a dual and use the free side to power the LED.
It may flash to the rhythm of your pick attacks but that might be cool.
Does anyone think this might work?

I did just that in a Ross-type compressor. LED flashes when compression threshold is reached.

[Pushtone]

Did you put and caps in between to smooth out the flashing or just wire straight to the opamp pins.

Although flashing at the threshold sound very neat with a comp.

Does it just glow when your under the threshold?

[Tubebass]

I just wired the opamp as a unity gain non-inverting buffer, and connected the non-inverting input directly to the envelope detector in the comp. The output goes to the LED through a resistor. The LED stays dark when there's no signal (or signal below the threshold) but it should be possible to bias the opamp so that the LED glows dimly with no signal. I just did mine the quick and dirty way!