Why do some tube amps produce better pinch harmonics than others?

[jl2556]

Hi,
I'm curious as why some mid/high gain tube amps produce pinch harmonics than others? Is it just simple resistor values that have been
limited to dial in the tone feel of the amp that the builder wants to control?
The reason I ask is that I just bought a 50 watt Hughes & Kettner Statesman Dual EL34(GREAT amp for the $). I have a homebrew 50watt SLO 100 I use and
I would love the Statesman to have as much of "this amp produces every nuance of your playing" that my SOL does.
It does the d, a and low e strings pretty good, but the high strings not so much. Would a good amp tech be able to get that affect out of the statesman without much trouble?
Or is there way more involved than resistor values?

[tedmich]

Howdy JL

My opinion is that the "jump" of a pinch harmonic is much more related to the overall gain of the amp. Very high gain designs like the SLO are much more effective at driving the string when you've hit a harmonic of the fundamental note with the side of your finger, as in a "chicken picked" pinch harmonic. While the H&K may be a high gain amp its also possible its voiced darker and the harmonic doesn't have the treble content required with that particular pickup, on that guitar with those strings.

Without the schematic on the H&K its difficult to say what would brighten it up to better emphasize the higher freq of the pinch, maybe a treble boost pedal or eq in the loop. In my experience the newer cobalt strings are fantastic for their higher harmonic content, they could make the H&K really scream for ~$7. Good luck!

[exclamationmark]

It's actually rather odd - One of my ultra high gain pre-amp designs actually doesn't do pinch harmonics as well as an amp designed for lower gain stuff, and I have no idea why. I'd hazard a guess that it might have something to do with how I've biased the pre-amp tubes, but then again their topologies were completely different. Or it might have something to do with the lesser amount of treble roll off on my medium gain build. Either way I'd say it's a little more involved than simply changing some resistors. Gain definitely has a lot to do with it, but not everything.

[tedmich]

^ agreed, also while you can pinch harmonics everywhere, most people mean getting the 1 or 2 octaves up harmonics on the higher strings, usually the unwound ones. So the treble content and the gain structure in the treble region are very important; definitely NOT a "first order relationship"!

"Change R43 to X ohms" will not turn the pinch harmonics ON, otherwise it'd have been a switch many years ago!

Try the cobalts and/or a treble boost or EQ in the loop, even a harder pick can sometimes help if you use one; I don't and my hands have to be dry and hard before I can do harmonics the way I like too. My main amp is a modded PV ULTRA with the JSX presence control added and pegged AND EB Cobalts so its razor sharp to compensate for finger dampening without a pick.

[big_teee]

I don't know the answer.
To add further, is the effect of different power and preamp tubes.
I put TAD Tall Bottles in the Traynor 50 Watt, and they made a huge difference with the harmonics.
Even on the Clean channel.
T

[woodyc]

It could be related to polarity, particularly for lower notes. It seems unbelievable, but all you have to do to prove it is get an acoustic with a piezo and a polarity switch (a lot of Fishman preamps have them) and try it.

[loudthud]

I wonder if it has to do with the exact location of the tone stack midrange crevasse. The phase also makes a big reversal at that frequency.

[J M Fahey]

It's not just "changing a resistor or two"; I'm sure those two amp schematics differ quite a bit.
And the Soldano was specifically tweaked for clarity and response speed, to the point that a few do not like it at all.

[kleuck]

The SLO is all about tone shaping, that's the key.

[jl2556]

....And the Soldano was specifically tweaked for clarity and response speed, to the point that a few do not like it at all.

Agreed, if you don't "have your hands together" the SLO isn't for you because it shows EVERYTHING...lol
Personally, I love any amp that does that.This H&K Statesman is so close is just frustrating...
I'm going to contact H&K and see what they say..
We do a lot of upbeat songs at church and I'm in the high gain quite often and there's a song that
when using my SLO(crunch channel @ 3'oclock w/TS9 and and Ibanez w/dimarzio EVOS)
I try to get the pinch harmonic on the 9th or 10th fret of the 2nd string and if i miss it, it's BAD...lol
but I love the challenge of trying to hit it right, and when I do, it makes a wonderful noise
.