Tube amp topography questions (channels, knobs, tubes)

Discussion in 'Amps and Cabs' started by RaistMagus, Jan 23, 2012.

  1. RaistMagus

    RaistMagus Member

    Dec 7, 2011
    Hi everyone, I am in need of advice from the more knowledgable, ampwise.

    What exactly does a 'channel' in an amp mean? Does each channel have to have a separate preamp and/or EQ section? Does it use seprate tubes to achieve that?

    Take for instance the Marshall DSL 401. The amp has 2 channels: clean and overdrive, and the overdrive has the options of OD1 (crunch) or OD2 (more drive). It's tubes are 4x12AX7 and 4xEL84. Are all four preamp tubes used in each channel or are they split (eg. two of them dedicated to clean and the other two to drive)? What about the power tubes? How does the OD1/OD2 function add more gain?

    DSL401 panel here:

    I do have a Budda SD 30 amp, with 3x12AX7 and 4xEL84. The amp has no tremolo or reverb or anything, and a single set of EQ controls. Is it a one channel amp? Does it have 6 gain stages, two from each 12AX7? Could any of the three 12AX7 be used for the effects loop?

    Budda SD panel here:

    The controls on the Marshall are: one Master Volume knob, one Gain knob for EACH channel, and a Volume knob for the Overdrive channel.

    The Budda’s controls are: Master knob (volume for dirt and clean channels on one knob...), Gain knob (affects ony the gain of the overdrive channel) and Rythm knob (affects only the volume of the clean channel but gives the clean sound quit a grit).

    Which tubes does each of these knobs push on each amp?

    Thanks for reading!
  2. smolder

    smolder Gold Supporting Member

    Jun 16, 2008
    Central Rocky Mountains
    yes... in most cases channels are separate preamp circuits with their own controls feeding into the same power tubes and speakers. In some cases there controls (master volume, etc) that work on both channels. Some amps facilitate switching between channels... otherwise look to an A/B or A/B/Y to accomplish that. Lastly... som amps allow you to jump channels (nonreverb fenders and four input marshals come to mind) which can thicken tone and give you additional flexibility.

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