Pulling pre-amp tubes on Marshall TSL-122 ?

Discussion in 'Amps and Cabs' started by snilloc66, Feb 1, 2012.

  1. snilloc66

    snilloc66 Member

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    I know this amp isn't exactly "well-loved" around here, but I've had one since 1998, and have generally had pretty good luck with it.
    I've gigged it, and beat it to death for over a dozen years, and it's still basically going strong. (Although the footswitch hasn't worked in years :rolleyes:.)
    Anyway, I use the middle gain channel 99% of the time, and use a SHOD if I need any more gain than that.
    But I was wondering if there might be any benefit by pulling the preamp tubes on the clean or high gain channels? (Like they do on Deluxe Reverbs, pulling V-1 etc.) I think I was told in the past it would be OK to do. Any thoughts?
     
  2. mixn4him

    mixn4him Supporting Member

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    First off, no. And why? if you are not using those other channels what is it going to save pulling a preamp tube? Those circuits cascade and you will end up with no sound instead of less sound.
     
  3. freaksho

    freaksho Member

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    he's right. to elaborate a bit: cascading means one gain stage feeds into another. in most channel switchers V1 is used by all channels, and the gain channels will use the later tubes. so no V1 = no sound. but it's important to know that a gain stage is just half a tube so it's very possible that your med gain channel uses half of, say, the last preamp tube and the high gain channel simply adds in the 2nd half. but even if the high gain channel has it's own dedicated tube, if it's not being used then it's not in the circuit.

    but aside from that all this, what do you think you would gain by pulling out preamp tubes? i've never heard of this.
     
  4. snilloc66

    snilloc66 Member

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    I was just curious about it, because I know it's a common mod in Deluxe Reverbs.
    I own an original 65 Deluxe Reverb and have pulled V-1 in the past, and I know it was safe.

    Here's a piece from the Fender Guru Amp mods page:

    Pull out the V1 normal channel preamp tube – More preamp gain in vibrato channel
    We’ll start with saying that this is a must have mod. It is so easy to enable and disable that it can hardly be called a mod. If you are like most players and only use the Vibrato channel (reverb, tremolo, the brigth cap and the extra gain stage), you should pull out the V1 tube. This is the preamp tube for the normal channel which you are not using. Vice versa; If you’re using the Normal channel, you can pull out the V2 tube. All AB763-similar circuits (Deluxe Reverb, Super Reverb, Pro Reverb, Twin Reverb, Vibroverb, Vibrolux) are designed so that signal is leaking between the two channels. The amp will play louder at the same volume knob setting when pulling the V1/V2 tube that you’re not using. The stronger signal will push the second gain stage (V4 tube) harder and give you increased sustain, compression and harmomics. This mod does not change the amp’s clean headroom.
    This mod is one of Cesar Diaz’ tricks in the Fender Custom Shop Vibroverb 64 which he always did to Stevie’s amps.

    I was just wondering if this same philosophy could possibly apply to my TSL-122. Just curiosity.
    Thanks for the replies guys!
     

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