Hey S.Luckey would the mods you did to your stand-alone revibe be practical in my application?
The mods I did will work in your circuit too. But if you are happy with the circuit as is there is no need. I had two objectives for modifying the LFO circuit.
First, I wanted an LED indicator that blinks at the rate of the LFO. This is mainly a visual mod, although it does increase the trem signal and it makes the amplitude of the trem signal more constant from slow speed to fast speed. But, while scoping the trem signal at my footswitch jack I noticed that the amplitude still dropped off noticeably at the faster speeds. Changing the .03 to .01 and the .1 to .047 increased the trem signal amplitude at the faster speeds, keeping the amplitude more constant across the entire speed range. Net result, I didn't have to readjust Intensity just because I changed speeds.
Second, I wanted the fast/slow speed capability because I like a slower trem. Switching a .01 cap in parallel with the original .01 cap causes the oscillator to slow down for a swampy Delta trem. But it also causes the fast speed to slow down too and sometimes I want the faster speed. Using a switch gives both speed ranges. Having an extended speed range is great, but the oscillator cannot work well over a wider range without a lot of other circuit changes. I found that below about 3Hz, the oscillator would sometimes drop out, just die. So, I put a 5.1M in parallel with the 3M speed pot to prevent the speed from going slow enough to cause drop out.
None of these mods affect the guitar sound. They deal strictly with the LFO circuit.
About your whop whop... That's likely because the two 180° out of phase trem signals are not totally cancelling in the modulator tube. For perfect cancellation the two trem signals must be exactly the same amplitude at the modulator grids (pins 2 and 7) ***AND*** the two triodes must be well matched ***AND*** the two 100K and two 470K resistors on the plates (pins 1 and 6) must be matched. A mismatch of any of these three parameters will result in some uncancelled trem signal appearing at the output of the modulator.
Changing both tubes in the trem circuit can affect the whop whop. That's where I'd start. Checking those four resistors I mentioned would be the second thing I'd do. Then I'd put a scope on the modulator grids to ensure the two trem signals are equal. If not, look back to the phase inverter to correct. If they are equal, move the scope to the modulator plates. If the signals are not equal then start rotating tubes. When everything is matched the trem signal will be completely cancelled and should not appear at the output of the two 470K mixing resistors. Since whop whop is not a mission critical parameter, don't expect perfect cancellation. Even if you get perfect cancellation, that's likely to change as the tubes age.
You can probably get the whop whop down to acceptable levels by simply turning the intensity down a bit.
