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UNPLANNED DOWNTIME: 12th Oct 23:45

Tube Amp Gain and Fat switch

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jaymenonjaymenon Frets: 761
edited June 2023 in Amps
This is the ‘High Gain’ switch (white arrow). It seems to be a resistor connected to the wiper of the preamp gain pot.
The red wire exiting the switch connects to pin 2 of the preamp valve.

what is it please and how does it work?




And this is the Fat Switch (Red Arrow)
seems to connect through either of those two capacitors (white arrow) to the pre-amp tube (blue arrow)



What is it please and how does it work?
this is the “fat” capacitor - connects to pin 7 of the preamp tube. 


Below is the ‘normal’ capacitor

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Comments

  • RiftAmpsRiftAmps Frets: 2989
    tFB Trader
    Draw it on out paper and you'll quite quickly see how they both work :)
    *I no longer offer replacement speaker baffles*
    Rift Amplification
    Handwired Guitar Amplifiers
    Brackley, Northamptonshire
    www.riftamps.co.uk

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  • EmprizeAmpsEmprizeAmps Frets: 11
    Looks to me like you have two routes for the audio signal coming from PIN 6 - fat switch.  You have different value ceramic caps which will add or shave off bass response. The output from this switch goes into the volume/gain control.  The ceramic 470pF cap on the pot adds bright.The audio signal comes out of the middle lug and through the 470k resistor into the top pin of the 'high gain switch'. The audio signal will go from here to PIN 7.If you engage the switch then the other resistor to ground in conjunction with the 470k creates a voltage divider i.e. reduces the level of signal.
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  • jaymenonjaymenon Frets: 761
    EmprizeAmps said:
    Looks to me like you have two routes for the audio signal coming from PIN 6 - fat switch.  You have different value ceramic caps which will add or shave off bass response. The output from this switch goes into the volume/gain control.  The ceramic 470pF cap on the pot adds bright.The audio signal comes out of the middle lug and through the 470k resistor into the top pin of the 'high gain switch'. The audio signal will go from here to PIN 7.If you engage the switch then the other resistor to ground in conjunction with the 470k creates a voltage divider i.e. reduces the level of signal.
    That is so interesting and so very helpful @EmprizeAmps ;

    Thank you very much :)
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