Amp question

Tal Herbsman · From: Wisconsin, USA

Hi all: new to PSG (almost 1 year). I have a non traditional amp (Mesa rectoverb 25 combo) that I got a good deal on. I realize it's not ideal but it generally sounds really good to me and I don't need much headroom for home playing. The one issue I have with it is an unpleasant shrill unmusical sound (almost like out of tune beating notes) that comes from playing double stops on strings 3/4 or 4/5 roughly from fret 12-17ish. Not a problem with single notes or on any other part of the neck. It's driving me nuts. The guitar is in tune. The sound is not distorted. I have not discovered a gain/eq setting that makes it go completely away.

So before I go crazy replacing amp speaker, tubes and PSG pick ups etc can anyone tell me what this phenomenon is all about? Is this the honking sound people have described re other amps? IS it fixable or do I get another amp?

Lane Gray · From: Topeka, KS

You might have some rough spots on the tops of the fingers, and the sound is always there and only becomes noticeable high up the neck. Turn the amp off,, wait for the AC to cycle off, play it acoustic, and listen for it.
While it's POSSIBLE you have a tube or other part of the amp are introducing something, but I bet it's just, ummmm, amplifying something the guitar is doing.
_________________
2 pedal steels, a lapStrat, and an 8-string Dobro (and 3 ukes)
More amps than guitars, and not many effects

David Nugent · From: Gum Spring, Va.

Good suggestion from Lane. Try playing with the amp turned off and attempt to determine if you still detect the problem...Question: Since you stated that you are a relative beginner; do you move the bar vertically while playing so that the tip of the bar is barely covering the strings being played or consistently keep all ten covered? If the latter, this may be preventing you from exerting sufficient pressure on 3/4 or 4/5 and causing you to experience the unwanted overtones (especially at fret 12)...Just a thought.

Tal Herbsman · From: Wisconsin, USA

Thank you for the advice! I tried with amp off and it sounds clean, I also tried with another amp and I cant recreate the annoying shrill sound so I do think it's the Mesa amp itself. Any ideas what might need to be replaced first?

Jerry Overstreet · From: Louisville Ky

It may be just multiple string artifacts from that particular amp because it can't handle the range and high output of the steel guitar pickup. Be sure you don't have the 10W option selected v.25. Probably works fine with standard guitar?

Tal Herbsman · From: Wisconsin, USA

I'm using it in 25W mode. Would a unity gain box or different preamp tube help things out?

James Holland · From: Alabama, USA

That amp is designed to break up at some point, and your pedal steel's pickup is hotter than the typical guitar humbucker, probably making it break up sooner - does it worsen with higher volume settings? Does it worsen with harder attack? And does it worsen in the 10w mode?

Brian Evans · From: Nova Scotia, Canada

That is a complicated little amp. I would set it up for clean, 25 watt, master up quite high, gain down quite low, tone and presence in the middle, reverb off. That gets you the least gain and lowest signal levels in the pre-amp. Next, I would turn down the signal from the guitar. The Gain control is after the first pre-amp stage, and too much signal can over-drive the first pre-amp section. You could try changing V1 to a lower gain tube, like at 12AU7 or a 12AT7, but turning down the guitar and the gain may well do almost the same thing.

Edit: The 25 watt mode is classic pentode power amp and should have higher headroom and go into distortion a lot later. Trying to reduce the gain in the first pre-amp stages just reduces signal level to the second and subsequent stages, so they don't get into saturation and distortion. Over-driving the first input stage with pedals and high output pickups is classic for an overdriven sound, but what you are hearing could be harmonic distortion effects beating against each other.

Tal Herbsman · From: Wisconsin, USA

Thanks again for the replies. The inharmonic sound is definitely correlated to input volume but not as much as I expected, just gets slowly worse. Strangely 10W mode is possibly a little better but certainly not worse. I've tried every gain volume ratio. Doesn't seem to make a huge difference.

Out of curiosity: when does one think of changing speaker vs pre amp tubes?

Lane Gray · From: Topeka, KS

Use input #2?
_________________
2 pedal steels, a lapStrat, and an 8-string Dobro (and 3 ukes)
More amps than guitars, and not many effects

Tal Herbsman · From: Wisconsin, USA

Only one input.

Tim Whitlock · From: Colorado, USA

Could be cone cry. Try hooking up the amp to a different speaker and see if you get the same effect.

Tal Herbsman · From: Wisconsin, USA

I looked up cone cry and found a couple of sound clips and it does sound like what's happening in my amp! Listening more carefully my annoying sound is a constant frequency inharmonic tone playing regardless of the note played.

I haven't been able to hook up to another speaker to test this out.

Q1: if it is cone cry, does replacing the speaker solve this problem?

Q2: is this a defect with the original speaker or is it just to be expected from using the amp for the wrong application? THe amp uses some custom Mesa designed 75 W 12" built by eminence based on another model called a v30.

thanks again.

Jim Sliff · From: Lawndale California, USA

I don't think it has anything at all to do with the amp. That amp should be sufficient for home use and isn't going to cause "beats"

Tal Herbsman · From: Wisconsin, USA

I'm about ready to pull my hair out at this point. I assumed it was cone cry and so replaced the speaker with a new Cannabis Rex that people here seemed to like. It sounds much worse now.

As for tuning, I use a peterson strobe tuner with their standard sweetened tuning. I also tried sight bar slants to play with slight pitch offsets, no effect. this is not a beating phenomenon.

My reference amp is a PV N112 I got on this forum. I've been playing suspect double stops so often now I'm starting to hear it with that amp as well.

I'm a piss poor novice player that has no business worrying about tone and I'd like to forget all about it but it's driving me nuts every time I hear it.

Jon Light · From: Saugerties, NY

Forgive me if you have already addressed this:

Are you using a volume pedal? If so, does this still happen when the volume is backed off 50%?
If you are not using a pedal, full-on PSG pickup output is hot. Possibly too hot for the amp's input.

Expert VP technique uses the top 50 (or more) % of the throw as sustain extender. IOW, amp input should not see 100% steel signal.
Does any of this apply?

Lane Gray · From: Topeka, KS

If you have the ability on your guitar, power the pickup. It'll tame the output, and usually improve the tone.
_________________
2 pedal steels, a lapStrat, and an 8-string Dobro (and 3 ukes)
More amps than guitars, and not many effects

Bud Angelotti · From: Larryville, NJ, USA

So this happens around the 12th fret, yes?
Could be you are not muting the strings behind the bar with your left hand. A little extra pressure with the bar and extra pressure with the left side of your left hand, behind the bar, when you play around the 12th fret.
_________________
Just 'cause I look stupid, don't mean I'm not.

Bob Hoffnar · From: Austin, Tx

Bob Hoffnar · From: Austin, Tx

Hmmm...

Is there a low ghost note that gets lower as you push the pedals way in the background ?

If that isn't there it may not be IMD. Why don't you contact me via Skype while you are at your steel. We can sort it out that way.
_________________
Bob

Tal Herbsman · From: Wisconsin, USA

Thanks again for the suggestions. I am using a pedal typically @ 100%. I backed it down to 50% as suggested at the same time increasing amp volume and it does sound better but I'm not really sure if this isn't a function of the volume being lower. Hard to do A/B type comparisons...

Out of curiosity, why is using a buffer different from lowering the volume with a pedal or lowering the preamp gain? Does the provided different impedance to the amp?

Bob, thank you for the generous offer. What would be a good time?

Lane Gray · From: Topeka, KS

BTW, I meant LOWER the pickup.
_________________
2 pedal steels, a lapStrat, and an 8-string Dobro (and 3 ukes)
More amps than guitars, and not many effects

Brian Evans · From: Nova Scotia, Canada

"Out of curiosity, why is using a buffer different from lowering the volume with a pedal or lowering the preamp gain? Does the provided different impedance to the amp?"

A buffer has a very high input impedance - which is great for accepting the signal from the guitar pickup - and a very low output impedance, lower than the pickup, which is great for sending the signal to the amplifier. The amp also has a high input impedance (typically 1 meg ohm)and does a good job of accepting the input from a pickup - but the combo of a pickup with it's medium impedance, a volume pedal that could be a simple medium - high impedance volume pot, and the volume pot on your guitar, and throw in a maybe long or wonky cable... sometimes the guitar needs a little help.

Your amp has the input fed directly to the first pre-amp stage. The gain control is between the first and second pre-amp stages, and the volume control is between the pre-amp and the power amp stage. So a hot pickup with any kind of boost, and the pedal at 100% can over-drive the first input stage. It's quite a hot stage, with a high gain tube (12ax7). Turning the guitar down, running the pedal at 50%, using a short cord, adding a buffer with a long cord, turning the gain down (to reduce signal to the second pre-amp stage) and turning the amp volume up to control the over all volume would be what I would do.

Jon Light · From: Saugerties, NY

As has been mentioned, the pickup height could be a major factor. What pickup do you have? A couple of pups have been well documented (anecdotally) to benefit from greater than normal distance from the strings:
BL 710 and Lace Alumitone.

Tal Herbsman · From: Wisconsin, USA

GFI II

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