A question for any Mark III owners

Does your Mark III tend to squeal alot at high volume with high gain settings? I bought a blue stripe rackmount head awhile back and I love it but it squeals like a bitch when I crank it up, I've tried all kinds of different tubes in V1 and I don't think my settings are too crazy. I'm using it to play metal but I'm not a total gain monkey or anything, I used it at a gig last night and I had the 1st volume at 7, master at 2, lead drive at about 5 or 6 and the lead master at about 8, no presence, no pull bright. I wouldn't mind if it would shut up when I mute the strings, I'd consider that normal, but it doesn't. I was able to cure the problem at band practice just by using a decimator in front with the knob set just a touch over 9 o'clock, that jived with the clean channel just fine but those gate settings weren't doing it with the amp opened up a little more and I didn't really mess with it much at the gig because i didn't want to fuck up my cleans. Anyway, is this normal behavior for a Mark III? Am I going to have to be a slave to a gate or is there something wrong with my amp? Any experienced insight before I call Mesa and bug one of their techs? Thanks.

Step away from the amp. When you run high gain, it'll generally squeal. My III doens't do it, but my Recto will on the Vintage Channel, boosted. Or just turn off your volume every time.

This is going on when I'm 10 feet plus from the amp. It gets not as shrill when I mute the strings but it still keeps going. I've tried several of my guitars so that rules out pickups, I don't even use pups with high output. Some amps are worse about it than others and with lots of gain comes hiss and feedback but I've never had one that I couldn't stop when I would mute the strings. I really wonder if there's some sort of parasitic oscillation going on inside the amp, it seems like it but I'm just trying to figure out if it's common to the circuit design of Mark III's or if something is out of wack in mine and causing it.

Try some different settings. 8 on lead master doesn't seem too right to me, I've never had mine that high.

What kind of pickups are you using? My Mark III will expose poorly potted pickups (say that 3 times real fast!) quicker than any other amp I've ever owned and the suspect pickups (Seymour Forgot to Dunk 'Em) will squeal like crazy at stage volume.

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Drew":85856 said:

What kind of pickups are you using? My Mark III will expose poorly potted pickups (say that 3 times real fast!) quicker than any other amp I've ever owned and the suspect pickups (Seymour Forgot to Dunk 'Em) will squeal like crazy at stage volume.

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+1

I agree with the above. Try some new pickups/get them re-potted.

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Drew":f6af5 said:

What kind of pickups are you using? My Mark III will expose poorly potted pickups (say that 3 times real fast!) quicker than any other amp I've ever owned and the suspect pickups (Seymour Forgot to Dunk 'Em) will squeal like crazy at stage volume.

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Maybe that's my problem, I use duncans in just about all of my guitars, that makes me sad because I tend to like their tone more than about anything else. It might be time to go get some gulf wax and start dippin. Arggh.

The worst offender for me is the Dimarzio Super Distortion in my LP. That guitar will do a low frequency howl if I don't turn the volume down.

My Ibanez with Evolution will not do that and will not squeal...period.

You said it's doing it with all your guitars? It might not be pickups if thats true. Whats the life on the Pre/Power Tubes?

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CaseyCor":43e24 said:

You said it's doing it with all your guitars? It might not be pickups if thats true. Whats the life on the Pre/Power Tubes?

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also the mark III has a bit of a rouph upper range at some settings, try pulling the deep knob if you already haven't and lowering the mids as it is already really mid heavy to get it smoother.

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CaseyCor":378e2 said:

You said it's doing it with all your guitars? It might not be pickups if thats true. Whats the life on the Pre/Power Tubes?

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Yep I just tried it with another one with a rio grande bbq in the bridge and it's still doing the same shit. The tubes are fine, I actually bought it with mint NOS GE 6l6's already in it and I've swapped a crap load of preamp tubes through this thing over the past few weeks, first I was doing it to get my tone, now I've been swapping v1 out like a madman trying to figure this shit out. I think I've got it sorted out now but I won't know for sure until I get to really open it up at band practice tomorrow. So I think it was the treble, took it from 7 down to 5 then up to 6 and it's much more controllable, I can compensate for that with graphic eq. I still think there's a damn bright cap or something in there that needs to come out. But on the bright side if anyone wants to hear about some Mark III tube shootout results lemme know and I'll post my opinions, I've tried all sorts of NOS and newer stuff in it trying to tame this beast. The short results are that a Amperex 12ax7 in v1 is the most agressive sounding mother out of anything I tried, nice cleans too, it makes the Mark III quite the heaven and hell rig, it'll tear your face off but kiss you first. Thanks for all the input guys.

no squeals here. i run an isp decimator tho.

If the problem persists, I'd suggest having a tech run it over. Perhaps you've got a bad cap or something. Glad you've got the probem (moderatly) fixed!

A Noise Gate wouldn't be a bad idea either, just to tame the ever present feedback at high volume playing!

Yeah I just bought a decimator (thanks to mchn13 here on the board) and it works great but I really don't want to have to rely on a gate all the time. The decimator is by far the best gate that I've tried but it's still there, and it's totally acceptable, no one listening would probably even notice it but I do. It just feels weird sometimes, I like effects and stuff in the right places but ultimatley I'm a guitar-> cable-> amp kinda guy. I looked the amp over when I got it before I ever even fired it up, none of the electrolitics look leaky but that doesn't mean too much, no burnt resistors everything looks tip top. I've worked on amps a decent amount but they've all been marshall type circuits. I'll probably call mesa and see if they can point me in any direction on what it might be, I feel totally confident that I could replace anything on the board but I don't want to trouble shoot this thing from scratch, there's alot going on in a small package. Otherwise I know a great boutique builder not too far away from me that could sort it out no problem, I'd just feel bad bugging him because I know he's busy with custom builds. I don't mind if it's on the verge of going nuts, that's a quality I love in an amp, I just want to be able to control it. Thanks again for your help guys.

no squeals here either...i've got a few guitars with duncans, and a few with EMG's and i never have that problem

My old mark IV was crazy noisy with EMG's, but with my explorer with 500T is wasnt noisy with the gain on 10.