Now we are in water FAR over my head...

Friend gave me an old Brownsville 15G amp. So, since I just wired up my Psycho box, let's see how it goes.

Lots of hum.  Amp works, Psycho works, though I think I need to dial it in as far as amp settings go.

How do I deal with the loud hum?

Why does the amp have 2 gain controls?

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Hum is the scourge of electric guitars and amps. The causes are almost endless.

Realize that as you overdrive the signal (distortion, high gain, etc) you will pick up hum. You can minimize this with a number of steps.

1. Ground the strings. They act as antenna to stray noise like from florescent lights.

2. Check your wall outlet to be sure it is properly grounded (many are not).

3. Try a different amp to see if the guitar or the amp are the source of the hum.

4. Try a different guitar to see if the amp or guitar are the source.

5. If the amp has a wall-wart power supply it is likely creating a lot of hum. Good, clean power supplies are not that common. Boss makes some good ones.

6. Turn the gain down a lot and turn the volume up to the level you want. Is gain driving the hum?

7. Bypass the Psycho knob and try  #6, Is the psycho knob adding a lot of noise? If you did the assembly, remember that poor solder joints add a ton of noise.

Okay, that should keep you busy for a while. If you can get the hum down a bit, you may have to live with it when the gain and psycho knob are both turned up into the high distortion (metal) range.

If you find something, let us know so we can learn as well.

Ditto what Tom T says, but you can sometime try touching metal components to see if the hum stops. Touch the metal ends of the cable, the guitar jack, the bridge (provided its grounded), a screw on the amp, etc. If you hear the hum stop (or lessen) when you touch one of these things, you've got a grounding problem. Also, if you reversed positive and negative that can often lead to unwanted hum. Double-check your positive and negative leads on both ends of the psycho knob.

Tom T's suggestion of localizing the problem is great. Try it w/o the Psycho Knob, try a different guitar, try a different cable, different amp if you have one, etc. See if you can nail it down to one thing. It could possibly be the amp you just got.

BTW, your amp has two volume pots because the first is a trim/gain pot. You can think of it a lot of different ways but oversimplified... the first one is gain and the second one is volume. Piezos have lower output than magnetic pickups which have lower output than active pickups. The first gain pot is normally used to get the level right for your setup (prevent clipping to the original signal), the second is used to control the actual volume. As Tom T states, try turning the gain down and the volume up and see if that helps. For a clean tone, I typically start with the gain knob in the middle and adjust from there.

Good tips, Poorness. When chasing hum, buzz, whatever, every tip helps to narrow it down. So much for the idea of a Hum-bucker.

Real life example (swear I did not make this up).

Earlier today I was finishing up some modifications on one of my three stringers. It uses the Gitty 3-string hard tail bridge and I ground the strings by drilling a hole under the bridge and running a ground wire from the audio jack to the bottom of the hard tail bridge. Works great and grounds the strings well.

So I finish up my work which involved loosening the hard tail a bit to the neck to be tilted. I put it all back together and give it a test run. First thing I notice is a lot of hum that wasn't there before. I touch the strings and nothing happens. I touch the jacket of the cable and the hum goes away. (light bulb flashes)

I get out my ohm meter and do a quick test and confirm that my strings are not grounded. So, I undo every thing (again) and find that my ground wire had slipped down its hold just enough that it no longer touched the bottom of the hard tail. Put things right, reassembled and back to the amp. Funny thing, no hum, even with my Blue Driver pedal turned up pretty high and the amp with a good bit of gain of its own.

I guess I confirmed the importance of ground strings.

No advice on the hum(except learn the words). One of my amps has two gain knobs, one is used with the drive button and the other is without it engaged.  Do you have two inputs? They could be for them.. Hope this helps

Every time I try to look your amp up. I get pics of my Fender. Can you post a clear pic of the control panel?


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