How do you tell if a buffer is working?

I

iamjackslackof

Well-known member
Maybe a silly question, but I am laying out a buffer PCB, and I realized I don't know how to tell if it is working properly, or just passing the clean signal. It will be part of channel switcher pedal and have a buffered/unbuffered switch, so I'm not sure I'll be able to hear which one is on and verify everything is working correctly. Is there a way to measure it somehow? I assume measuring the difference in output impedance might do it, but I'm not sure how to do that.

Thanks!
 
Put it in front of a GE fuzz if it makes the fuzz sounds like 💩 then It’s working….

I can tell when a buffer is working because my high end is pronounced vs a slightly dull high end without a buffer.

Edit: oh yeah you should be able to measure the Ohms on the output jack to see the difference from engaged vs not engaged.
 
Thanks! It occurred to me later as well that on killing power, the buffered signal should drop while the unbuffered should not.

Is measuring the ohms on the output jack an accurate way of determining the output impedance as well? I would assume not, but I hadn't thought of it for testing the buffer, so thanks for that!
 
Chuck D. Bones said:
Dan's right. Except for the last sentence. Ohmmeters don't measure impedance, they measure resistance. Put a capacitor in series with the output of a circuit and the resistance measurement will read open circuit. 99% of pedal circuits have a capacitor in series with the output of any active parts to remove residual DC.
Click to expand...
I guess it depends if you're after a real or imaginary impedance reading. It's all complex to me. :cool: [feeble attempt at electronic lingo humor]
 
Connect a capacitor to ground at the buffer output to simulate a looooong cable. Experiment with the value, I just tried 47nF just now and it worked great as a test. . If the buffer is engaged and working, then it should sound much brighter compared to if the buffer is bypassed (assuming the buffer is first in chain, so bypassed would be the same as the cap connected directly to the guitar out).

Depending on the buffer output impedance, you may still lose some high end with the 47nF cap, but waaay less than if the pickups’ output impedance sees the cap.
 
if I run my SG through a bunch of cable into my amp and roll the volume back I get a noticeable loss in tone. If I have a buffer between, then it sounds much more similar to me plugging my 10' cable directly into my amp. If you can't hear a difference... maybe its not working or you don't really need it?
 
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