Phase 90 vibrato mod

[bancika]

If I understand correctly, for this mod I should place a switch to disconnect a 150K resistor going from the first opamp stage to output transistor (tis is dry signal if I understood well). Is this correct?
How will vibrato sound? Is it worth doing?
Thanks

[Mark Hammer]

First, YES, that is what is required to produce vibrato.

Second, unlike phasing, vibrato requires faster speeds to be heard.  Not necessarily faster speeds than the pedal normally produces, but only the mid-to-fast speeds will be useful to you, so if you have the wrong taper on your speed pot, you may be frustrated.

Third, since faster speeds are generally preferred for vibrato, some capacity to alter the sweep width is also very helpful.  I'm sure you realize from your use of chorus or phaser or even tremolo effects, that as you turn the speed up, lowering the depth/width of sweep is almost mandatory.  The human ear/brain prefers change to happen within certain rate limits; not too much change per unit of time, but not too little either.  While slow phasing provides an acceptable minimum amount of audible change per unit time, slow vibrato does not (hence the requirement to use generally quick sweep rates).  But rate of change is not only how fast you sweep.  It also includes how far you sweep each moment in time.  And sweeping far, very quickly, is too much change.  So, we prefer to reduce sweep width as we increase sweep rate.  Sadly, the P90 has no default control for adjusting sweep width.  There is but one width/depth setting.  Consequently, you may find that depth is suitable for vibrato, or not; suitable at speed X, but annoyingly boingy at speed Y.  I'm not satying you'll hate it or regret it, but it may not instantly be something that makes you say "Where has this been all my life?"

[bancika]

Thanks Mark.
As I mentioned before, I have a few extra holes on the enclosure which I want to use for some mods. So it doesn't necessarily have to be killer mod, just something that might be useful and something that can be set to the stock value.
I have chosen to add variable resonance instead of 24K resistor and intensity control (500K pot in series with 1M resistor going to the trimmer). Any comments?

[loki]

is the 150k resistor R8 or R7?