.50cal+ Squeal

[mches]

Hey all, great board you guys have here.

I have a .50 caliber + (6l6 version) head that is experiencing excessive squealing when playing at band level volumes with the gain set to anywhere above 2. The type of squealing I'm talking about is incredibly high pitched (sounds like an angry pig) and can only be stopped by rolling back the volume on the guitar, lowering the gain below 2, or lowering the master / lead master to a level where the drummer drowns me out. If I keep the strings completely muted (palm muting on one end with the other hand muting at the fretboard) the squealing will also stop, as well as if I play constantly. Additionally, any notes I try to let sustain will ring out for 1 to 2 seconds before beginning to feed back.

I've tried multiple guitars, multiple cables, and multiple preamp and power tubes to correct the issue, but the amp always begins squealing before I can get the amount of gain I want. I've tried moving as far away from the amp as possible, as well as standing behind it. I'm always locked into a rock tone with the gain set so low when I'm really after more of a metal type tone.

I've read reports of players being able to use this amp with the gain set to 6 and both the master and lead master set above 5 without experiencing squealing. This setting would be perfect for me but is currently unattainable.

Any ideas what is causing this issue?

Thanks!

My setup:
ESP LTD EC401VF Guitar w/ SD JB in the bridge and SD 59 in the neck.
.50 Cal +
4x12 slant recto cab

 

[MrMarkIII]

It's probably a microphonic 12AX7 in the V1 position.
Here's the manual:
http://www.mesaboogie.com/manuals/50%20Caliber%20Plus.pdf
It could also be a microphonic pickup. The feedback going away when the strings are completely muted makes that a possibility. A bad tube tends to squeal no matter what.
You don't say what your other knob settings are, and if you're running the Treble and Presence really high, that could be a problem.
If it's not the first pre-amp tube, put it back where it belongs and go on to the next one in line. One tube at a time. Rinse and repeat.
If you've got the dough, and you're impatient, you can go the scattershot route and simply replace all the tubes at once and hope for the best.
Hope this helps.

 

[mches]

Thanks for the response.

I just went through a retube trying to fix this problem with no luck. Consequently the amp does sound better than ever due to the new tubes, when it's not squealing.

I'm beginning to think that my pickups are microphonic in each of my guitars I've tested. After doing some research it seems like potting the pickups in wax might be the solution I'm looking for.

 

[FXR]

We get that when the front end is over-driven. Using a pedal and the volume on the guitar the gain can't go past 11 o'clock on one amp. We had to get someone down on the pedal board tweaking the output knobs to the gain setting and it was a compromise. But for us, we got what we needed.

 

[snave]

I suggest you get the amp checked out by a tech. I had the same head as you a few years back, and squealing like that didn't even occur with the gain near dimed.

 

[mches]

I might have to bite the bullet and get it looked at by a tech then. I potted the pickups and made sure they were absolutely stable, but am still getting the same squeal.

It is certainly a frustrating problem, I like to have both of my masters around 5.5, but can't have the gain anywhere above 2 really before it starts squealing like mad.

 

[scottcrud]

Try my settings and see if the squeal won't go away:

gain-10, mas-3, lead mas.-9, treb-7, bass-3, mid-5, rev-0, pres-3, geq pretty much the classic V with the mids pushed up a bit...

I also put a 12aT7 in the phase inverter spot...

 

[FXR]

I have come to find after the time that has past since I last posted that I had a bad PI tube causing the feedback in my Express 5:25 when the front end was driven.

Worse, I didn't think the PI tube was bad because I swapped in a bad replacement that had the same bad characteristics despite being new. So, with no change, I kept putting the bad tube back in. I had purchased the tube I was swapping in and out specifically for the PI. Tube quality is a tough thing these days sadly. A Mesa Chinese(old) and a Penta Chinese(new) in this case. The Mesa Chinese tube was well worn however.

I put a working tube in the PI and I can crank the front end now, push the hell out of the gain, run high mids & bass high and she hangs in there. It's loud as hell and punchy again. I'm back to where 25 watts is too loud for the house. Getting the guitar to interact with the amp and getting feedback is easy to with the front end pushed hard, but not out of control. When I last posted I couldn't go past 2 o'clock on the gain without feedback issues and if I turned on the OD it all went to hell in feedback and oscillation sounding noise.

Anyway, I hope you find your ghost too. I'm crossing my fingers hoping my exorcism celebration isn't premature, but I think I nailed it and fixed my complaints.

 

[mches]

I have come to find after the time that has past since I last posted that I had a bad PI tube causing the feedback in my Express 5:25 when the front end was driven.

Worse, I didn't think the PI tube was bad because I swapped in a bad replacement that had the same bad characteristics despite being new. So, with no change, I kept putting the bad tube back in. I had purchased the tube I was swapping in and out specifically for the PI. Tube quality is a tough thing these days sadly. A Mesa Chinese(old) and a Penta Chinese(new) in this case. The Mesa Chinese tube was well worn however.

I put a working tube in the PI and I can crank the front end now, push the hell out of the gain, run high mids & bass high and she hangs in there. It's loud as hell and punchy again. I'm back to where 25 watts is too loud for the house. Getting the guitar to interact with the amp and getting feedback is easy to with the front end pushed hard, but not out of control. When I last posted I couldn't go past 2 o'clock on the gain without feedback issues and if I turned on the OD it all went to hell in feedback and oscillation sounding noise.

Anyway, I hope you find your ghost too. I'm crossing my fingers hoping my exorcism celebration isn't premature, but I think I nailed it and fixed my complaints.

I also bought a supposedly balanced PI tube (from eurotubes) when I was first dealing with this issue. I'm hoping that it turns out swapping the PI with a different, better tube fixes the problem.

My amp has been at the tech for a while, and I think they're a little stumped by it (not a good sign). I'll let them know to try several different phase inverters.

Thanks.

 

[jpdennis]

Is your amp still at the tech's? Did they find the problem? Do you use the effects loop?

Dennis