Proximity buzz?

[sluckey]

The PT hum is probably characteristic. I don't really know. Easy fix, don't put your guitar pickups near the PT.

Looking at the gut shot of that amp, I'm surprised it doesn't sound like a buzz saw. And there is some downright dangerous wiring methods and component mounting inside that chassis. Just look at those screen resistors for example. And those PI coupling caps. If any one of those 4 component leads contact the chassis, you may have some expensive repairs. I doubt this amp is roadworthy.

I'm not trying to be mean spirited with my criticism. I'm just being realistic. That's a gross misuse of a hot glue gun!

[cbass]

The PT hum is probably characteristic. I don't really know. Easy fix, don't put your guitar pickups near the PT.

Looking at the gut shot of that amp, I'm surprised it doesn't sound like a buzz saw. And there is some downright dangerous wiring methods and component mounting inside that chassis. Just look at those screen resistors for example. And those PI coupling caps. If any one of those 4 component leads contact the chassis, you may have some expensive repairs. I doubt this amp is roadworthy.

I'm not trying to be mean spirited with my criticism. I'm just being realistic. That's a gross misuse of a hot glue gun!

That was my first thought. Some one made this to sale. Wow

[sonofmickel]

But I think he uses epoxy rather than hot glue. Fingernail test did not appear to make a dent in the goo.

I have tugged at the leads and they seem like they are staying put. Suprisingly quiet except for the low 60 hz hum and the loud proximity hum.

I will take your advice and keep my guitar away from the amp, especially with single coils. Maybe that's a feature...play the dang guitar instead of fiddling with knobs.

Thanks for the help.

[Leo_Gnardo]

Beats that funky mold smell that usually accompanies amps & instruments, don't it.

I like that old funky mold smell.

I'll send you a box of my old sox, indulge yourself!

sonofmickel, glad you got your meter reading sensible stuff now.

Overall amp hum regardless of control settings, could be one or several causes. One major cause is output tubes that aren't well matched. After that a dozen more. If the hum level is low enough to be covered up by your playing, not much to worry about. Many people, including me, have been misled by listening too intently, too closely, in a very quiet room. Of course it's wonderful to have hum down to a barely perceptible level but it's not always practical. These are guitar amps, not $50,000 stereos.

Big hum with guitar pickups a foot away from the power transformer, hell, you gotta expect that. Reminds me of a bad old joke:

Patient: Doc Doc, I get a pain in my eye when I drink my coffee!

Doc: Take the spoon out of the cup before you start drinking. That'll be $450, pay the receptionist. NEXT!

Pickups sense changes in magnetic field. They don't care if it's from wobbing strings or anything else. Hums & buzzes, just the sort of thing you'd expect a foot away from any power transformer.

[sonofmickel]

I see your point about the coffee and the pain from a spoon in the eye.
But...I thought toroidal transformers had basically no field effect, that's why the are chosen for very quiet applications. Also for light weight.

I have had a few of the new Class D poweramps that had about zero "buzz" from inductance. How, or why is the toroidal this sensitive. I think a video will be made of my particular model showcasing what I believe is a bit too much interference.

[Reeltarded]

Yeah normalish..

Is there shielding in that cabinet?

[Leo_Gnardo]

I see your point about the coffee and the pain from a spoon in the eye.
But...I thought toroidal transformers had basically no field effect, that's why the are chosen for very quiet applications. Also for light weight.

I have had a few of the new Class D poweramps that had about zero "buzz" from inductance. How, or why is the toroidal this sensitive. I think a video will be made of my particular model showcasing what I believe is a bit too much interference.

The AC magnetic field is supposed to be "contained" in the toroid core, net it doesn't go anywhere. Like a hamster running in its wheel. However if there's too much field, insufficient core or overloaded transformer, the field's going to show up outside the core and that's what I'm thinking is going on with your buzz pickup.

If the transformer is designed/chosen "conservatively" with a fair amount of margin between the way it will be used and max ratings, shouldn't throw much of a field. Likely that's what you have in your class D amps.

[Reeltarded]

It sounds like it's not shielded. The guitar isn't any closer to the transformer than it is anything else in that freaking antenna... except what sounds like the unshielded circuit.


What is the shortest distance between two points?

Thirteen inches.

[M Fowler]

Just worked on a Laney VC30 212 and it hummed like crazy I discovered power tube imbalance was the cause. New set of EL84's and the amp never sounded so good.

Side note: the old IEC plug/fuse holder must have broke at some point in it's history and replaced with regular IEC plug no main fuse. Inside the wires were twisted together no solder and no crimp connects it all fell apart when I removed the black electrical tape. Told the owner I'm fixing this mess whether you like it or not. The amp now has a fuse.

[sonofmickel]

That's it!
New set of tubes and the "hum" has all but disappeared!
That should always be the first thing to try.

Amp sounds fine if a bit forward on the clean channel. I am going to blueprint it. It appears to have a hybrid tonestack. The mid is not grounded and on the volume pot there is a resistor and cap in series instead of the usual bright cap. An avant-garde gain channel as well. Definitely not Blackface or Shiva.

Edit: the mid IS connected to ground ala Fender, didn't see where the black wire went, it goes to the volume pot-then to ground(should have done a continuity test!) anyway, all the black wires get a little confusing to me.

[Leo_Gnardo]

Are you telling us the hum your guitar picks up from the PT cleared up with a change of tubes? Seems bizarre but if it works, go with it.

[sonofmickel]

The "hum" has subsided, not the "buzz".

The proximity buzz is still there. There was a low 60 hz hum that was audible even with the volume down and increased with Master Volume turned up. That is almost nil with new tubes installed.

I may try installing a shielded wire for the clean channel input. The gain channel has a shielded wire input.

[Reeltarded]

NO

THERE IS. NO BOX SHEILDING look inside your amp CABINET

You have one of the two largest sides of your chassis open to RFI.

[Bob S]

Not trying to defend the build quality in any way - I know how anal we are about it here...
But looking at it subjectively, some of us have had great success with big boards & with holes for the tube socket connections. Components as close as poss to where they need to be. Very stable - even for an Express circuit. This just leaves out the board.
The builder is a member here & I have played 2 of his amps. They do sound great. An ugly girl with the lights off sorta thing.
^^^ AND SHIELDING. Tape is your friend.

[Structo]

60Hz noise (hum) usually involves the heater wiring.

120Hz noise, is twice the frequency (yeah) and is usually caused by the power supply as in B+ voltage.

To put it very simple, most likely a power supply problem or lead dress problem.