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PostPosted: Fri Sep 15, 2017 11:26 pm 
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Mark II

Joined: Sun Feb 02, 2014 11:51 am
Posts: 95
Hi,

Tonight at practice the TC-50 was up to bat. All was well in channel 2, gain at noon, tight, crunch heaven. Channel 3 however, was having issues. My guitars (a PRS with Seymour duncan Mark Holcomb pick-ups, a JP IX with the Liquifier/Crunchlab set up) would both howl around when not being played, even with strings fully muted. The only other time I've experienced this was with the Rectoverb cranked, I figured it was a Rectoverb thing. When the guitars were being played, there wasn't any problem, just when stopping and holding the strings the guitars would howl.

The settings (o'clock): EL34 tubes, Channel 3 Tight, Gain 2:00, Master 1:30, Pres 1:00, Treble 12:00, Mid 10:30, Bass 9:00 , Output 10:30. Amp was on a concrete floor in a double garage. I was maybe 5-10 feet away from it. I put EL34s in before practice because I figured the extra power (vs. 6V6) would be needed with these guys (GnR, old school Metal 80s-90s). Room was pretty solid (brick, cement etc.)

Yes, the amp was loud, but not overly so. With the Mark V it can be much louder with no howling around.

Any ideas of what settings to modify (without reducing volume) to prevent the howling? I did knock the bass and mids down a bit when it first started howling, but it didn't help much.

At any rate, I love the tones out of the TC-50 so I'd like to get this to work in the future. Thanks,

Mace


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PostPosted: Sat Sep 16, 2017 6:14 pm 
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Mark I

Joined: Thu Dec 01, 2016 3:14 pm
Posts: 30
I had a squeeling with a guitar that had really hot pickups. Im not familiar with your pickups but maybe it could also be a microphonic preamp tube. Have you tried another guitar?

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PostPosted: Sun Sep 17, 2017 7:55 am 
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Dual Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 2507
Location: North Carolina
I believe it is the tight mode causing the feedback issue. It works about the same as the Mesa grid slammer but is not adjustable like the pedal is.
You may need to adjust gain and presence to find the happy median. I have been getting feedback with the tight mode on CH3 so I generally do not use it. If you do need it, you may have to adjust your settings to compensate for the gain structure change.

Pickup potting (typically a wax) used on the coil if not sufficient could lead to similar issues. You could always try the foam pad behind the pickups (which would cut down on body resonance behind the pickup that may cause feedback issues. I have a Koa guitar that rips but will feedback without the dead space filled with foam pad behind the pickup. Open cell type works well, compresses easily and does not push back on the pickup unless you pack too much in the cavity. If you have a bleed capacitor on the volume pot, try removing it and see if that changes anything.

Your guitar cable can also play a role, if it is one of those high dollar cables like the Mogami Platinum cables, sound great but makes everything much brighter than I prefer, much easier to get feedback with it so I do not use it very often.

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Current amps:
TC-50, JP-2C, MK V, Roadster, RA100
Old friends I sometimes miss:
Mk III (blue stripe), Mark IVb-WB


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PostPosted: Sun Sep 17, 2017 9:49 pm 
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Mark II

Joined: Sun Feb 02, 2014 11:51 am
Posts: 95
Hi,

Thanks for the replies. Always helpful!

Pickup potting - I did that a few years back on an old Japanese 1970's vintage Epiphone I borrowed while living in Germany when it was doing the feedback/howl like this. However, that was at much lower volumes. The potting helped a bit, but it really just changed the frequency of the feedback, made it lower.

The thing about the PRS and Music Man guitars is that I have cranked the living crap out of the Mark V 90 watter Ch 3, Mark IV and IIc+, BRIGHT on, with no issues with these guitars (albeit a different practice room, which was actually smaller, but not as boxy and cement walled as where the TC-50 was howling). The Mark V was with a more or less classic "V" curve (more like a check mark, with the high side on the left) on the EQ and gain at about 1:30-2:30, presence 12 noon, treble maybe noon to 1:00.

Once, months ago, the Music Man was howling with the Rectoverb 25 MODERN cranked (I do not remember the dial settings). So, it must be that the TC-50 Ch3 TIGHT and Rectoverb Ch2 MODERN have something in common as far as the frequency band distribution.

I'll have to do some more experimenting with a couple other guitars with less "hot" pick-ups and also dialing the settings a bit, but this type of aural abuse is something best not done at home. haha

One last questions: Do any of you guys get feedback (with the strings muted silent) with the settings I posted? Just curious.

Mace

PS I always wear custom molded earplugs when practicing, just so y'all don't think I'm a glutton for punishment.


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PostPosted: Mon Sep 18, 2017 6:20 am 
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Dual Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 2507
Location: North Carolina
I have gotten feedback on CH3 in tight mode, muted strings and not using hot pickups. I chose one of two options, dial back on the volume control or just not use the tight mode (unless the gain was reduced).

It is a bit more aggressive than the Mark V:90W and the frequency response is also different. well lets say before the Saturation mod, I could not dial the gain above 10oclock on the V without instant feedback unless the strings were muted, the second I would pull away though, ouch.

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Current amps:
TC-50, JP-2C, MK V, Roadster, RA100
Old friends I sometimes miss:
Mk III (blue stripe), Mark IVb-WB


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PostPosted: Mon Sep 18, 2017 7:56 am 
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Mark III
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Joined: Sat Dec 17, 2005 11:16 am
Posts: 265
Location: Bellwood, PA
To be honest, I think your channel master is too high. My basic settings are: EL34 tubes (stock), Tight, Presence 10:00, Ch. master 11:00, Gain 1:30-2:00, Bass 2:00, Treble 11:30, Mid 1:00 and my Global master is set around 10:30-11 depending on venue/home use. Mine is dead silent with no feedback at all. My main guitar at the moment is a 2017 Charvel San Dimas with a Seymour Duncan JB & 59' in it. Now, mind you I have the head version and am running it through a Recto 4x12 cab, so that will make some difference, but I really think if you lower the channel master a bit you'll notice a big difference. There really isn't any practical or utilitarian reason to have the channel master up past noon. That would be my first recommendation. Hope you solve the problem man, it's a fantastic amp.

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PostPosted: Mon Sep 18, 2017 4:02 pm 
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Mark II

Joined: Sun Feb 02, 2014 11:51 am
Posts: 95
Daxman73 wrote:
To be honest, I think your channel master is too high. My basic settings are: EL34 tubes (stock), Tight, Presence 10:00, Ch. master 11:00, Gain 1:30-2:00, Bass 2:00, Treble 11:30, Mid 1:00 and my Global master is set around 10:30-11 depending on venue/home use. Mine is dead silent with no feedback at all. My main guitar at the moment is a 2017 Charvel San Dimas with a Seymour Duncan JB & 59' in it. Now, mind you I have the head version and am running it through a Recto 4x12 cab, so that will make some difference, but I really think if you lower the channel master a bit you'll notice a big difference. There really isn't any practical or utilitarian reason to have the channel master up past noon. That would be my first recommendation. Hope you solve the problem man, it's a fantastic amp.


Thanks for the input. Not sure if I mentioned it but I'm running the stock combo.

You could be right. I was noting that the TC50 sounds a bit thinner than other amps and it was suggested (I think by Bandit) that the channel masters be raised, which might beef it up. Maybe that worked in spades (as evidenced by the incessant howling)!

My old Epi SG has a Duncan JB in the bridge, so I'll try your settings (and suggestion) with the SG and other guitars and see what happens.

Mace


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PostPosted: Tue Sep 19, 2017 1:57 am 
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Dual Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 2507
Location: North Carolina
the channel master and the gain work together. You could adjust the gain to compensate if needed, this can make things difficult if you are tying to balance channel levels. You can even use the gain as a volume control as I found that the gain setting dramatically influences output volume and or the master volume influences the gain characteristic. Tight mode does change the response in the midrange and upper frequencies as well as the bottom frequency. With the CH2 a boost in bass and reduction in treble reduces the thin character. CH3 tight mode does pose its challenges and I have had some difficulty getting past the howling issue when using it. Finding a setting that works for you may be different that what others may have due to differences in guitars, pickups, etc...

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Current amps:
TC-50, JP-2C, MK V, Roadster, RA100
Old friends I sometimes miss:
Mk III (blue stripe), Mark IVb-WB


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