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Princeton Reverb Tremolo Pace

Discussion in 'Shock Brother's DIY Amps' started by jchabalk, Oct 21, 2020.

  1. jchabalk

    jchabalk Tele-Meister

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    I've been tweaking my Princeton lately through a couple of other threads.

    I love the tremolo in this amp and have been reading a few threads about slowing it down even more by increasing capacitance in the relevant part of the circuit.

    With the stock capacitor values (.01uF, .01uF, .022uF) and the speed turned all the way down i'm getting about 230bpm (just using an online tap temp tool to check). I tend to play it with the speed dial on 2 or 3, i don't go much faster than that.

    The idea of slowing it down some more was interesting so i clipped another .01uF cap i had into the circuit temporarily and it went down to ~200bpm. Then i swapped that extra .01uF cap with a .022uF cap and got it down to about 175bpm.

    So then i added both the .01uF and the .022uF cap and it didn't slow down any further (still got ~175bpm).

    I'll mess around with this some more this evening. Should it continue to slow down with more capacitance or is there a lower bound it maybe wouldn't fall past?
     
  2. Phrygian77

    Phrygian77 Friend of Leo's Gold Supporter

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    The caps form a series of phase shift filters, which gets the signal back around to 180°. The thing is, you can only get so much range out of the oscillator. You can go lower, but the upper end will also be limited.
     
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  3. jchabalk

    jchabalk Tele-Meister

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    ahh good - thanks for that!

    I'm going to play it tonight and see which value i like best. i was just experimenting this afternoon by clipping caps in the circuit when i had 10 minutes to spare.
     
  4. jchabalk

    jchabalk Tele-Meister

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    I played last night for a while, the trem sounds great. Here's what i've done (only temporarily at this point)

    • Added a .022uF cap to the trem circuit (so now i've got .01uF, .01uF, .022uF, +.022uF)
    • 2 additional 1M resistors in parallel with the stock 1M resistor on the plate of V4 (to increase the intensity)
    I'm going to solder the .022uF cap in place and probably replace the stock 1M resistor with a resistor around 220k or thereabouts.

    I'm now in the frustrating situation of needing to order $4 of parts, so i'll probably find some other small projects i need to get parts for too.
     
  5. Drew617

    Drew617 Tele-Meister

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    That's a good idea, but if you don't know, Tubedepot's shipping rates are very reasonable. Appears to be at-cost, and USPS first class is an option. I learned to build during quarantine and ended up doing several amps in a very disorganized fashion. I'll never start another without a complete BOM at the beginning, and without trying very hard to minimize vendors/orders. But tubedepot's $4 shipping kept me from really wasting money.
     
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