ilovefuzz.com

So yesterday I picked up this Music Man HD150. My first tube amp. Sounds awesome clean and dirty and I am quite happy with how it sounds.


That is until this morning when I started noticing unwanted distortion It's this kind of swelling sound when I dig in. I'm running the amp low and have the preamp volume low, so it shouldn't be clipping. Any ideas of that this sound could mean? You can hear it really well after the hammer on in the last few seconds of the video.

Also FYI, the preamp is solid state.

[youtube]http://www.youtube.com/watch?v=EO5Sl2LmUo8[/youtube]

I had a similar issue when I was feeding the signal from a Fender Twin into a bass stack via the line out. The Twin was all rickety, the chassis rattled, the bolts weren't tightened etc. and all that rattling and buzzing was somehow coming out through the speakers on both amps and it sounded exactly like your "ghost distortion". Fifteen minutes with a screwdriver solved the problem. I hope this is the case with your amp.

Bon Hoga wrote:I had a similar issue when I was feeding the signal from a Fender Twin into a bass stack via the line out. The Twin was all rickety, the chassis rattled, the bolts weren't tightened etc. and all that rattling and buzzing was somehow coming out through the speakers on both amps and it sounded exactly like your "ghost distortion". Fifteen minutes with a screwdriver solved the problem. I hope this is the case with your amp.

that has happened to me as well. rattling stuff sounds like weird unwanted distortion for sure.

Still getting the noise. Should I take the whole amp out of the chassis and see if I can find any loose hardware? I took the back off and every screw I could access without taking it out was tight. I also made sure all of the external stuff on the amp was locked in, and I made sure my speaker and speaker grill were secured.

As I was told, all is original except the power tubes. Used two different basses and different cables. Going to try a different outlet or something. So frustrating because it was fine yesterday and it sounds so good otherwise. It's not unplayable, but ya know. Bleh.

I played with a guitarist and drummer today and the amp is dirty enough at that volume that this problem doesn't really matter, but I don't know if I'd be doing more harm than good in not fixing it? Iunno. Sounded killer though.

Ehh....
Pull the tubes out one at a time and put em back in to make sure they're seated properly?
Idunnolol

Yeah I was thinking about that, will do tomorrow.

I had a similar issue with my amp when I first got it. I would recommend taking it to a tech. It probably needs new tubes or something.
and be really careful opening up your amp and stuff. don't mess with any caps or they might kill ya!

Usual tube amp cautions and don't lick the circuit board applies. Stuff hurts.

First thing I'd look for is to make sure the fuse is the right value for the amp (and slo-blow if applicable, etc). Most amps of that era seem to come with the wrong type installed, and it can be a problem especially once you start tinkering with new volumes/tubes/etc beyond what was 'safe' for it before. Note that 'safe' is not something I'd screw with - it runs on the fuse it was intended for or there's something wrong.

If that checks out, pull the tubes. Reseat them. See if that fixes it. Swap their positions, same.

Also swap the polarity switch if it has one (that era probably does still) - BEWARE of ground issues if so. All the TGP people will insist you. absolutely must get that replaced, and it's not a bad idea if present but at the same time I never did on amps that had it and lugged them around to dodgy crapholes for years.

Swap to a backup set of tubes as well.

I'm guessing it's either bad tubes or something drifted out of spec. Hard to say, though, I'm hearing more background hiss etc than what is bothering you.

Yeah my camera is not the best at recording what is really going on. I need to get a field recorder at the very least. Checking the fuse and resetting the tubes are good ideas, will do that today. If those don't help I'll take it to a tech.

& yeah it does have a three position ground switch. From what I read the middle position is the safest so I flicked it to all three positions then back to the middle, still had the same sound. I don't want to leave it in any other the other positions seeing as how I could potentially shock myself pretty terrible.

is the sound the same on all outlets? i always plug my tube amps into a furman since the dreadful gig where i had that sound than bam amp a went, and backup amp b which was plugged into same outlet went <worst gig ever> (and i even bought a fucking backup amp. sigh. who the fuck dose that.) but anyways yea could be power issues. i always rule that out first in weird amp noises. than i check cables, and guitars. if not that, and your not tube amp savvy i recommend taking it to a pro. i suck with electronics, so i try to be good friends with my amp repairman haha

mine does the same stuff but I dont really care because I like and and just crank the fucker.

having it gone over by a tech should help.

Yeah, I can't tell when mine is cranked & playing with others sooo whatevs.

fishtankdork wrote:is the sound the same on all outlets? i always plug my tube amps into a furman since the dreadful gig where i had that sound than bam amp a went, and backup amp b which was plugged into same outlet went <worst gig ever> (and i even bought a fucking backup amp. sigh. who the fuck dose that.) but anyways yea could be power issues. i always rule that out first in weird amp noises. than i check cables, and guitars. if not that, and your not tube amp savvy i recommend taking it to a pro. i suck with electronics, so i try to be good friends with my amp repairman haha

Yeah I actually didn't end up trying it on quite levels on a different outlet, so I will do that tomorrow. Also need to get a surge protector or whatever for my amp & pedals for sure. Didn't play the amp today so no resetting the tubes or changing of the fuse yet either.

But all good suggestions. I'll probably have a tech look if I can't solve it, just cuz it's old n sheit. Thanks dudes

Yea, check the fuse for sure. I've run amps for years on the wrong ones before I realized how important it was to check (I made a very nice vintage tweed champ go splat because the previous owner had put in something literally that might as well have just bypassed the fuse, OT went south, a glorious, glorious sound for a couple hours but then...dead).

Also, check the tubes themselves for signs of scoring/burns on the pins etc as well - sometimes there's carbon buildup that's harmless, sometimes it's a sign of problems, sometimes the carbon gods just love you.

But if you're happy with it at playing with others volumes, and the fuse checks out, might not be something to worry much about - noise floor on big iron isn't always quiet.