stephen sawall
Well-known member
I have not owned a Marshall in years. My THD Series One Plexi is a NMV JMP style amp ..... But every Marshall I have ever plugged into sounds different. This amp by far is the best sounding amp I have ever heard. It does sound different in ways from any stock JMP I have plugged into. Usually these amps start to crunch around 11 o'clock on the volume. My THD does this around 9 o'clock.A few thing THD has said about these amps....I was kind of surprised to see EVH & Dave Friedman names come up when I was looking for info. I sound & play nothing like EVH.
"....is a crunchy, distorted-sounding amp that exudes a strong rock
and roll persona with a bright, snarly, vintage Fender timbre. Plugged into the Bright
channel, we could set the presence and treble knobs at zero and the tone would still be quite
clear. In this channel, the controls are very interactive; we found that the unused Normal
volume knob affected the bass frequencies even more than the bass control. When we
plugged into the Normal channel, the Bright volume knob acted like a notch filter. Settings
from 5-8 yielded a cool, skanky midrange dip."
"..... So I went to Andy Brauer’s shop where they had dozens and dozens of Plexi Marshalls and JMPs and asked them if they had an absolute favorite 50W amp. “Oh, yeah” they said, but it belongs to one of
our employees, Dave Friedman (now owner of Rack Systems in North Hollywood). It
sounds like nothing we’ve ever heard. So I ultimately borrowed that amp, and I’d fly
down every month to Make n’ Music with Dave’s amp and our prototype and we’d work
on getting it right. Dave’s Marshall was not 100% stock. It had either been changed a
little bit or they had used some components that were slightly different at the factory, but
it was basically a ’69 small box JMP and it sounded pretty much like the tone on the first
Van Halen album all on its own – just spectacular. We made a new circuit board based
on what we learned and observed with that amp and sold the hell out of them. Over the
next 5 years we built and sold 700 or so of those.
TQR: Can you describe what was so special about the sound of that amp you used for
your prototype?
It had more musical character, and the harmonic overtones sounded like they just
belonged with the note you were playing. You know, with some amps you can really
hear minor and major thirds within the harmonic texture that’s created. This one was like
that, it just did it a little bit better, and I think we succeeded in accomplishing what we set
out to do very well."
"One of the things I did was take the variation out of it – the variation in manufacturing.
Maybe you feel that the 1970 small-box JMP 50 is the best sounding amp for you. Fine,
go get 6 of them. Put the same identically rated, matched tubes in them and you’ll still
have six dramatically different sounding amps."
".....The amp has multiple primaries on the transformer so it
can be switched to the voltages of many different countries, and because of the way the
switches work out, there is also a setting on the switch for 140 volts. Now, if you set the
amp to “see” 140 volts but you only give it 120, it’s very similar to setting it at 120 and
giving it 105, so it’s very similar to running a Variac. Some people claim that Variacs
are dangerous to amplifiers, but it isn’t the Variac that’s dangerous, it’s the hand on the
Variac. An actual Variac is an adjustable transformer that, when it sees 120V it can be
adjusted anywhere from zero to about 145V. In his first interview – the first big on I
guess he did for Guitar Player, Eddie Van Halen said that to get that sound he ran his
amp on a Variac and he turned it up to 140V. He later corrected himself and said that he
set it at 95V. But by then a whole lot of people had already blown up their amps because
what they did increases the voltage to the tubes, the filter caps – everything, and that
usually results in something getting fried. Turning the voltage down just a bit – down to
105V – 95V, even down to 90V won’t hurt anything, but it will reduce the power of the
amp and it changes the bias setting a little bit. As the tubes cool down with lower
voltages it gives the amp a little different sound. It’s an educated guess that what the
majority of what one is hearing using a Variac is the result of the output transformer not
saturating. If you take a 100W amp and Variac it down, you’re only going to get about
60W out of it, meaning you’ll get somewhat more subtle harmonics out of it because
when the tubes distort, they’ll create much more complex harmonics than the output
transformer would be capable of passing if it were distorting instead. Once again, this is
educated guess, not gospel, and it’s very subtle.
TQR: But why is this potentially important to me as a guitarist?
It must be important, and significantly so, or you wouldn’t have done it.
It’s a different feel as much as a different sound. The amp can become more bouncy,
more dynamic, and harmonics that don’t quite catch at full voltage suddenly become
more discernible because the output transformer isn’t squishing them. Tubes are
generating those harmonics all the time, but because you’ve lowered the amount of power
you’re putting into the transformer, more of the harmonics are getting through. Also,
you’re reducing speaker distortion to some extent, and speaker distortion tends to smear
the notes and subtle harmonics."
I usually use full power .... not the brown option. The channels are linked internally so both volumes work all the time. There is a tube driven effects loop (4th preamp tube) that can be used as a boost. I usually never use it. Since most of the distortion comes from the power section I never use the loop for effects.... but have used it for preamp out & poweramp in.
