# Reducing the effect of a phase shifter?



## Greg Ellis (Oct 1, 2007)

I've got a very simple one-knob phase shifter (it's a Danelectro clone of the Phase 90), and while I like the effect, I find it a bit "too much" sometimes. The knob controls speed.

Right now I'm running it after wah and dirt, but before delay, chorus and reverb.

Is there some other position in the chain where I can get a similar effect, just not quite so pronounced?

I took the pedal apart to see if there were any hidden trim pots or anything (like a mix control maybe?). No dice.

Any ideas?


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## keto (May 23, 2006)

Probably not. Even my very old phaser has a 'mix' or 'intensity' knob to deal with that. That said, Mr. Hammer should be along shortly to give you a more thorough and correct analysis of the situation  We are very blessed, it's been said before but I will reiterate, to have his presence in our community. Hat's off to you, Mr. Hammer.


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## mhammer (Nov 30, 2007)

The schematic fof the danelectro Pepperoni can be found here: http://www.experimentalistsanonymous.com/diy/Schematics/Phasers/Danelectro Pepperoni Phaser.gif

1) The P90 had a fixed amount of feedback/regeneration. The particular amount depended on whether it was "script" or "block". But the P90 does not require feedback, and some folks actually _prefer_ a phaser without feedback. reducing feedback reduces the obviousness of the effect. The schematic suggests that the Pepperoni does not employ any feedback, so that option is off the table.

2) Phaser subtlety also depends on the mix of wet and dry. A 50/50 mix gets you the most pronounced notches, and cutting back on wet (e.g., a 60/40 mix) gets less pronounced notches. In the case of the Pepperoni, this would involve replacing R29 (150k) with 180k or perhaps 200-220k.

3) A narrower sweep also produces a subtler sound. The sweep of the FETs depends on the current used, or current feeding the "gates" of the FETs by the LFO. In the Pepperoni, this is set by R12 (3.3M). making it larger in value (e.g., 3.9M, which was used in some issues) will narrow the sweep. Better for "bubbly" sounds.

4) There is a trimpot, and the trimpot is used to set the bias of the FETs. It is summed with the LFO at the point where R12 and R25 meet. Tweaking that trimpot sets the "starting point" of the sweep, and effectively the range it sweeps in. Yo may find that simply altering the range gives you a sound you can live with. Maybe you prefer gurgly to swirly, or vice versa. You won't hurt the phaser by tweaking it, but you may find it tricky to regain your original setting if you liked it best. 

The difficulty with doing any of this is that the Pepperoni uses surface mount components, which are harder to work with, and certainly harder to replace with thru-hole. You CAN, however get a 1/8W resistor and use if to replace the SMD component already there. I've done it. In fact I did it to a Behringer clone of the P90.

Phasers placed before a distortion are subtler and more dreamy or "pillowy" that when placed after a distortion. The reason is that when placed after a distortion, they filter it, in much the same way that a wah after a distortion has a more synth-like sound. Placed before a distortion (which is precisely how Jimi and Robin Trower did/do it, albeit with a Uni-Vibe) the phaser serves to adjust how close to the clipping point different parts of the spectrum are. That has the effect of modulating the sonic byproducts without having only a pronounced effect on specific points in the spectrum. Try it, you'll like it.


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## Greg Ellis (Oct 1, 2007)

Thanks - this worked (moving the phaser in front of my gain pedals), although maybe a bit more than I wanted.

I'm going to play it this way for a while, and see.

I have a sneaking suspicion that the sound I really want is the "univibe" style, rather than the phase 90, but there's only so much money in the wallet, if you know what I mean...


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## mhammer (Nov 30, 2007)

Many folks have subbed the Uni-Vibe cap values into a 4-stage phaser and had good luck getting that sound. I subbed those values into a Ross Phaser clone that I made about 8 years back (as part of a 3-pedal prize for a battle of the bands in my son's high school), and it just killed. Couldn't stop playing it.

The actual Uni-Vibe has a somewhat different LFO than the Pepperoni, and between that and the use of photocells, you get a sightly different feel to the sweep. But as an ersatz vibe, a simple cap-change can be surprisingly effective. If you're good with the soldering iron, you can easily try it out and put the originals back in if you don't like the result.

It's also the case that Uni-vibes have a more restricted speed range. Since they produce a rather unfocussed shallow dip, slow sweeps do absolutely buggerall. You simply can't hear them. So, for example, in the case of the Pepperoni, it is probably a good idea to put a 150k-180k fixed resistor across the two outside lugs of the speed pot to reduce it from max 500k (slowest speed) to a max of 115-130k (depending on added parallel resistor. so that you get a sweep range from around 1hz to whatever the fastest speed was originally. If that fastest speed isn't bubbly enough for ya, tack on a 22k resistor in parallel with the 10k (R13) that's already there. That sets the fastest speed.

Uni-vibes do not have any feedback/regeneration, as a rule, simply because it doesn't do anything useful and can actually detract from the sound. IN the Pepperoni's case that would seem not to be an issue because it appears to have no feedback.

Charlie "Moosapotamus" Barth has a nice illustration of adapting a Small Stone to do some of what I describe, here: http://www.moosapotamus.net/THINGS/frankenstone.htm


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## mrmatt1972 (Apr 3, 2008)

I was going to suggest using an effects loop. Many amps have one built in and you can dial in the amount of effect vs dry that you want.


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## mhammer (Nov 30, 2007)

I think what Greg wants, or at least believes he wants, is not attainable via what you suggested.

It's a useful approach for some things, but not what I suspect he's looking for.


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## Greg Ellis (Oct 1, 2007)

It might help, actually, but I don't have an effects loop in my amp, so it's kinda moot.


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