A simple "active" tuner out for volume pedal

Ryan Quinn · From: Northampton, MA

I had followed the thread on adding a resistor to create a tuner out on a passive volume pedal, Tuner Out For Your Volume Pedal, and was just reminded of it when I saw it was a "sticky" on the top of the page. I decided to create my own topic because I don't want to get off-topic on that sticky thread.

I was considering the single resistor modification described in that thread, but wound up going another route by retrofitting my Goodrich volume pedal with an op-amp buffer/splitter with separate amp and tuner outputs. I wrote it up on my band's website (http://www.salvationalleystringband.com/2014/01/steel-guitar-buffervolume-pedal/) if anyone is interested. Apologies for any mistakes in the schematic, I don't have much experience drawing circuits.

I figure if anyone is thinking about taking a soldering iron to their pedal to add a resistor, they might consider getting a little more fancy with something like this. It loads your pickup with a 1M input impedance and provides an isolated tuner out that continues to work when your heel is down and your amp is silent. It has a very low parts count and meets the basic goals described in the original thread with the added benefit of providing the tuner a full signal with no voltage or current loss. It fit easily into my Goodrich, along with a battery and external power jack.
_________________
Fessenden SD-10, Long-Scale Fender 400, Short-Scale Fender 1000

Don Griffiths · From: Steelville, MO

Brilliant idea there Ryan! Thanks for the explanation.
_________________
Shobud Pro1,BMI U12, Santa Cruz F, PRS Standard, Fender Twin Reverb, ‘53 000-28

Georg Sørtun · From: Mandal, Agder, Norway

Even with some mistakes in the schematics, that is a pretty OK active VP. The "tuner out" is a nice addition for those who need that.

BTW, no need to add an active stage after the pot. With a 10Kohm pot the output "impedance" is never higher than 5Kohm, which is plenty low enough to keep noise out and drive long cables.
If anything, try it with a higher grade op-amp, to get distortion even lower at this critical first stage.

Ryan Quinn · From: Northampton, MA

Thanks for the feedback.

Good to know there's no need to add an op-amp to drive the cable. My sense was that the self-noise from the additional op-amp stage would likely cancel out any benefits from lowering output impedance.

I actually did swap out the RC-4558 for an OPA-2134 op-amp. I only used the 4558 at first just in case I burned up the chip when I powered it up. I think I could hear a difference between IC's, but it was subtle. I'm happy to get any signal improvement I can pick up though.
_________________
Fessenden SD-10, Long-Scale Fender 400, Short-Scale Fender 1000

Forum Index > Electronics		Next oldest topic :: Next newest topic

All times are GMT - 8 Hours	Jump to: