Vibing a Phase 90?

[Mark Hammer]

Thanks Mark, so the feedback route is the 'resonance' control?

http://www.sabrotone.com/wp-content/uploads/2010/08/MXR-Phase-90.gif

On Harald's vero the output at pin 7 of IC2 routed through the switch via R18 to pin 6 of IC1 (the Block/script switch)? This kills the path or runs it through the 22K R18.

Yup, that's it.

[kaycee]

So, as promised the mods to the vero:

Using Harald Sabro's vero of the MXR Phase 90 phaser as the base, here are a few mods for the circuit.



The main mod is to change the filter capacitor values to give a vibrato type effect.
The four capacitors to change are: C2, C4, C5 and C7.
The values are: 15nf, 150nf, 4n7 and 470pf. Apparently the sequence doesn't matter. You can also try the Dunlop Rotovibe values: 330pf, 33nf, 1n5 and 15nf.

The way that I did this was to use a 4pdt toggle switch
http://www.ebay.co.uk/itm/150522990363?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2648


This is wired from the capacitor positions on the board by flying leads to the switch in this way:


   
Next mod is to raise the volume output. Increase the value of R26 to 180K.

Wet/dry mix: If you want to add a pot to mix the wet and dry signals you take output from points 2k and 23e, each going to the outer lug of a pot (@ 47K -100K lin). Remove R25 and take the center lug back into the circuit at 25j the base of the PNP transistor. You will need to balance the mix using series resistors on the outer lugs, try 100K @2k and 56K @ 23e. I prefer a proper clean blend to this method.

Depth/Range control: from Mark Hammer, replace R17 (1M) with a 330k series resistor and a 1M pot.

This is my completed build. I added a clean blend (Joel Purkiss Buff'n'Blend) and a post circuit boost, the central knob.


Thanks to everyone who offered help and advice with this, and to Harald for the vero.

[Mark Hammer]

So how does it sound to your ears?

[kaycee]

Its okay, I'm not that wild about the vibe option on this, (I like the magnavibe circuit quite a lot, even though its a bit noisy) I think that I like the P45 circuit more in this format. I might take another crack with the rotovibe values. But if your going to build a P90 on vero you'll most likely need this size box, so why not add another switch, can't hurt?

The clean blend is something I suggest people try, particularly with the P90 as it can be used to tame the throb a bit. It was a useful project for me to undertake and I appreciate all the pointers and help from folks

[DougH]

Its okay, I'm not that wild about the vibe option on this,

That's the way it struck me when I tried it on the breadboard when I was building my phase 90.

Nice looking build.

[kaycee]

Thanks Doug 

An interesting idea is to split the two pairs of filters and run them off of different LFO's, gets very wobbly.