Modding a Phaser into a Tremolo?

[DuoSonicboy]

First off, I'm a largely self-taught n00b, so be gentle.
I've been experimenting with modding phasers lately (Uni-vibe mods, stage lifts, etc.).  I've been looking at tremolo pedals, but I was wondering if it would be possible to somehow turn a phaser into a trem.  I did a search that suggested upping the capacitors in a two-stage device to about .1uf for a "tremolo-y" sound.  Would this work?  Any other ideas?  I don't really care if it's a perfect tremolo, just an interesting effect would be enough to make me happy.  Ideally, this would be a switchable mod built into my Small Stone, if that makes any difference.
I'll try any ideas - just toss 'em out!

[Paul Perry (Frostwave)]

Look at it this way: the phaser is varying by changing the apparent resistance of the fet.
So if you replace the caps by a resistor - or by a large cap in series with a resistor (so that the biasing is not screwed up) then, as the fet is varied by the LFO, you are effectively sweeping a voltage divider.
A two pole two way switch will suffice for a simple phaser.

[DuoSonicboy]

I think I understand the basic concept - I looked up voltage dividers on wikipedia and read that they can be used to control amplitude.  A .1uf cap pretty much passes all of the guitar's frequencies, so is there any advantage to using that over, say, just another 27k resistor?  I still get confused whenever phase-inversion comes into play.

[Paul Perry (Frostwave)]

I think a voltage divider section, consisting of a resistor and a fet, is going to give a better trem effect than a cap and a fet. Because, if the cap is large enough to pass all frequencies efficiently, then there won't be much trem depth at all.
But, only experiment can tell for sure!!
Go to it, and tell us how you get on. We are keen to know!!

[Ben N]

Have you read this thread?
http://www.diystompboxes.com/smfforum/index.php?topic=55129.0

In it, RG Keen references a modification of the Phase 90 into a Fender Pro-like trem. I don't know if this is something you can do with an existing pedal or not, though. Check it out.

Ben

[mac]

The EA trem and the phozer v.1 use the same oscillator. I guess that a switch could connect the osc to the Phozer or the EA.

mac

[DuoSonicboy]

Well, it works using 30k resistors instead of caps and it is a trem...

-but-

there's not much trem depth and the LFO clicks like crazy.  i'm gonna tweak a little when I have some time and see if I can improve the situation.

[Jim Jones]

I realize this is an ancient post but I was mucking around with the same idea just last night. 

For giggles I was tinkering with my Easyvibe (socketed .01 caps in the phasing stages), and thought about making a phase/trem option as I don't care for the vibrato-only effect.  I ended up keeping the .01 cap in the first stage and just placed wire jumpers in the other three capacitor sockets.

You wouldn't throw out your Fender Tremolux after hearing the mod but I think it sounds really good.  Is there any harm in doing what I've done?  If not I think I'll wire up a toggle switch and call it a day. 

Jim

[Mark Hammer]

If you've seen any of my various posts on converting a Small Stone or Ross phaser into a "phasefilter", you will know that the way in which the OTA, be it a CA3094 or half an LM13600, is used in each of those permits the type of filtering action to be changed by simply rerouting a single component.  Those stages can also be converted into straight VCAs as well, though the documentation that would tell me how to do that is missing on my machine here at work.

Clearly, while it may require 4 stages to produce 2 notches, it would require only one OTA stage to produce simple volume modulation.  So essentially what you'd be doing is converting something like a Small Stone into something like the Hollis Frobnicator.  This is a VERY early suggestion, however.  I'll need to dig up documentation at home later tonight or tomorrow to determine if it is practical.  If it starts to require multiple switches, or some exotic multi-pole switch that takes up too much wiring and costs too much money, then another path should be pursued.

[Jim Jones]

Hey Mark,

I experimented with just jumpering a single cap and then a pair and finally three.  The tremolo effect was deepest and most pronounced with the three stages jumpered.

Jim

[moosapotamus]

You can also just disconnect one end of the cap to effectively disable that stage. When I built my frankenstone I used 3-position (on-off-on) toggle switches to switch each stage between bandpass-off-lowpass (re: phasefilter mod). If you only have one active stage, it sounds very tremolo-like.

~ Charlie

[frequencycentral]

Why not just build a tremolo? A much simpler beast than a phaser!

[Jim Jones]

Why not just build a tremolo? A much simpler beast than a phaser!

Well, the phaser was already there so I thought, "What the hell." 

I tried mucking with it again last night at higher volume levels and it doesn't sound pretty.  Too much distortion with the caps jumpered and a nightmare to wire nicely as well.  All those wires going to the switch were picking up LFO racket and all kinds of nonsense.  Oh well, it was worth a shot. 

Jim

[Mark Hammer]

I will still put in a plug for the phase-filter mod, since it produces an effect that feels like a tremolo.

[col]

I think that Guitar magazines (UK) latest kit is a phaser/trem project. Has anyone built it/got a schematic?

Col