Bare Knuckle Pickups Forum
Forum Ringside => Guitars, Amps and Effects => Topic started by: Tricalibur on June 05, 2006, 04:55:19 AM
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would I be correct in saying that when you crank the volume (Loudness) knob on a Marshall SLP you are basicly causing the power amp tubes to distort? An on a similar note, if you were to have a preamp volume installed would that knob thereby vary the amount of drive applied to the pre amp tubes?Also, concerning the channels on a stock SLP.If youn were to crank the volume on the amp would the amount of drive being applied to the signal be any different between channel 1 and channel 2. I kno that there is a High Treble and a Normal channel and for some reason I used to always think that the treble was the more distorted.Thanks
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The high treble inputs might sound more distorted, but there's no more gain going into them than in the normal inputs. When you plug into the lower inputs of each channel though, there should be a reduction in gain available. The high treble channel has bypass capacitors on the mixer resistors and the cathodes inside the circuit which emphasise the mid and high frequencies, which lead to perceived gain (and coincidentally, part of the classic Marshall sound).
If you crank the volume knob, and don't have any master volume installed, you should be able to get the power tubes to distort. With a preamp master volume, only the preamp tubes would get overdriven at low volumes - the control would vary the amount of signal coming from the preamp tubes and hitting the power amp section.
If you want the sound of power amp distortion, you want to install a PPIMV (post phase-inverter master volume). Most of the power amp distortion comes from the 3rd preamp tube, which is known as the "phase inverter" section. It sounds much much closer to a Marshall run flat out than a preamp master volume does. Many people are happy to run these instead of attenuators, and it only costs a few quid in parts.
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so if you were to install one of these PPIMV things you would in fact be able to vary the overall amount of vollume with the original volume knob and also the amount of powertube distortion with the PPIMV? So what would happen if you were to crank both the PPIMV and the normal volume? Would you get twice as much gain or would the overall volume be the only thing to change? Also, when a stock plexi is run a t maximum volume (with no additional od or boost pedals used) are the poweramp tubes the only thing to distort? Meaning that on a stock plexi there is no way to make the preamp tubes overdrive?
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if you have a plexi with the volume on full you are distortion pretty much everything in the signal chain... preamp, output stage, the power supply will sag somewhat and you'll get core saturation in the output transformer & also some speaker cone breakup if you're running 25w or 30w greenbacks.
:twisted:
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A Plexi's distinct tone comes from it's circuit design.
If you want something with more gain/breakup, get a JTM45 or JCM800.
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A Plexi's distinct tone comes from it's circuit design.
If you want something with more gain/breakup, get a JTM45 or JCM800.
JTM45? Those are cleaner!
But turning the presence up often makes it sound more distorted.
JCM 800 is a decent alternative, and adding a 4th 12AX7 tube is also an acceptable alternative if you want the plexi sound with more gain (WARNING: This tone has balls!).
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A JCM800 may have the gain I want but there just to bright in comparison to the warm, smooth tone of a plexi IMO. Thanks for thu help guys. I think the plexi is what im gonna be lookin into buyin within the next year. I think if I attenuate and then blast the imput witha bad ass treble boost I should be able to get some real amazing tones :twisted:
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Now, I know its not the real thing and nowhere near as loud but the Zvex Nano is so plexi like at full chat- no good for gigging of course..