Rotovibe intensity, curious about how subtle it is with distortion

[Myampgoesto12]

Santa brought me a new toy!!

It's a JD4S Rotovibe with a Revision A board in it.

My first impression is total love when used on a clean signal with it placed before my compressor, actually first in my chain so far. Nice swirly woosh and can get a little sea sick-ish when the intensity and rate dimed and playing full lower chords (bar chords, etc.) simultaneously. That's no biggie though. My only let down is its subtlety when used with distortion. I tried it after and of course it's got that psychedelic jet tone, whish cool but not particularly useful.

I have a schem that I found here on DIY but it isn't exactly accurate to my version/revision. Based solely on the fact that both of my internal trim pots are 20k, and there isn't a 20k pot in the entire schem. I haven't done much tracing simply because this pack full of parts. Through hole at least, but still packed.

I've tweeked the internal pots for two reasons.
-To learn for myself what they do
-After that to tune it to my taste

My findings are that the pot closest to the input jack either alters the waveform of the LFO, or changes how the LED/LDR or vactrol things light up in response to the LFO waveform. And the other pot changes how far the effected signal is detuned by the phase stage. I checked myself with this pot by switching to vibrato mode at medium speed and could hear the notes get a pinch lower. Maxing this pot out really makes the sea sickness happen at intense settings lol.

So my main question is this- is the subtlety of this effect a result of it's frequency response (say, the caps used in the phase stage because I have no idea what the math would state the response to be  ) or another perameter like the intensity control?

It's still no deal breaker either way, I have my diy -phase 90 kit in a wah box- that sounds pretty darn good before distortion. Just trying to see if there's more this pedal could offer.

Thanks

[Myampgoesto12]

So I took some more time to look up phasers and how they treat distortion and came across a post from Mr. Hammer about how most vibes don't have feedback loops within the phase shift stage and a little light bulb popped above my head. I think I'm on the right track here but I have a little problem.....

Comparing the phase stage of the Roto to a p90 they are suuuuper similar. So I did some tracing of the phase stage and figured why do that fully when the p90 feedback loop is simply a resistor between the output pin of the last opamp and the input pin of the second. And figuring the worst I would get is some runaway feedback I made a little 11k jumper wire (two 22k's in parallel cause I couldn't find a 10k) to just apply it between ouputs and inputs of the tl064 used in the phase stage.

With this between pins 2(-input 1) and pin 14(output 3) I found a wicked phase sound that I absolutely love on dirt and on cleans, but when I switch it to vibrato mode it's still shifting phase along with the drysignal switching between modes it sound like the phase shift is weaker in vibe mode but it's still very present.

Am I missing something about the layout of a new feedback loop? It's like I'm bypassing the mixing bypass switch or something hah.

Thanks

[Myampgoesto12]

Sorry to keep rambling on about this.. but I've found something that I haven't seen discussed yet(doesn't mean that it hasn't). The LEDs in the phase stage of this particular unit don't appear to be set up like the schem (older version that I've seen clones of) where each LED has a limiter resistor on it. These look like they attach to a transistor drive stage of some sort.







On the component side of the board the transistors are located to the upper left of the LDR/LEDs.  I was hoping to maybe find a way to increase the brightness of the LEDs (and potentially the debth of the effect) but I haven't messed with this type of setup. If these were like the older models it would be simple to find the limiters and alter their values lol.

I'm digging for caps now to see what I can cook up with the phase stage. I had a random .1uf that i touched to the existing caps in the phase stage but I need a few more options to find something that sounds like it's worth modding the pedal for. May try the P90 values just for kicks.

Sort of figured out my feed back loop problem. I was literally bypassing the dry signal bypass effectively adding a loop to a loop hah. But I didn't find a sweet spot there yet. Still tinkering.

[Myampgoesto12]

Sorry to keep going on about this, but I have learned something new!

I built the depth control portion of the circuit in my circuit sim and just used a sine voltage source as the faux waveform. The trim pot works much like the trim pot in a p90 where it sets the center voltage of the waveform, not changing the over all voltage swing.

I've sort of traced the phase stage but still working on it. However I've found that playing with feedback stages doesn't really yield a usable difference in tone. I'm gunna try caps soon, just gotta findem.