best lfo for phasers??

[swt]

what do you consider it would be the best lfo for phaser and why??. i'v tried a lot of phasers, and some doesn't have the deep travel i need, some are not slow enough, etc. the only one that is prefect is the moogerfooger, but have no idea how to do something like that. what do you suggest to build?. parts or complexity being not an issue...

[Mark Hammer]

Don't confuse the translation of LFO output into phase shift change with LFO properties.  A perfectly good LFO can result in movement of notches only an octave or less if paired with the wrong LDR or FET.

There is also the question of the compatibility of the waveform and the style/use of phasing.  A waveform that works well for ultra-slow sweeps (e.g., <0.2hz) may not work so well for throbbing medium-speed (e.g., 0.7hz-2hz).  The same thing goes for the waveform that best suits "bubbly" phasing at faster speeds.

Of course, sometimes the SAME LFO can be used with different outcomes.  Recently, we had a thread here about the LFO used in the Small Stone and (OTA-based) Ross phasers.  The first edition Small Stone simply stuck a capacitor to ground on the output of the LFO that would add some slewing to the LFO output and change the sweep waveform when the speed went above a certain point.  I added this to my Ross clone and it works great.  Same LFO, same basic waveform, but differentially "reshaped" at some speeds.

[bioroids]

I guess a more general question would be how much movement is desirable for the notches on a phaser, to get a great phasing sound. I think this would also vary with the sound source, as the notches going higher (or lower) than the frequency spectrum of the instrument wouldn't make too much sense.

I found a little hard to tune a phaser with selectable 4/6 stages, and get a perfect sweep in both settings. I assume it is even harder if you got more choice of stages (say 8, 16 or whatever)

Luck

Miguel

[Mark Hammer]

Sometimes, what people *really* want is not a different waveform, but rather simply the ability to set the "start" and "endpoints" of the sweep with a manual adjust and sweep depth control.  Not so much HOW the notches are moved around, but WHERE.

You will note that few commercial phasers arrive with more than 3 controls: speed, depth, regen.  The depth control lets you set how much travel there is, and set it appropriately for slower and faster speeds, but restrictions in travel are almost always in the extent to which it sweeps upward from a default start point. The difference in feel can be substantial when comparing restricted travel in the range of the fundamentals against the same amount of travel in the lower or upper harmonics.  That difference in feel can be as much, if not more, than the difference in feel provided by different sweep waveforms that lack such offset/initial/manual adjustment.  I suspect this is primarily because of the different psycho-musical "meaning" of variations in harmonics vs variations in amplitude of fundamentals.

Note as well that if you allow the notches to sweep in the range of the fundamentals, that such notches will reduce any clipping for those frequencies further down the line.  In contrast, simply notching around the lower, middle and upper harmonics will still permit the fundamental to be unattenuated and better able to overdrive subsequent stages, again yielding a different feel.  Stick your phaser before and after your distortion pedal and listen to the differences.  Again, not a difference in HOW the notches are moved around, but WHERE.

[Sir H C]

The Roland Rackmount SPH-323 is the only phaser that I know of that gives a center frequency (same as tweaking that internal knob on most phasers) as well as depth, regen and all the rest.  It is an amazing phaser.

[Mark Hammer]

Actually, the bias trimpot on many phasers (e.g., the MXR P90) can be co-opted to do that.  I suspect the reason why companies don't take advantage of it is because it is more trouble than it's worth.  I moved the bias trimpot on my Rocktek to the chassis and about 40% of its rotation is useful (very useful I might add).  Ideally, it should be replaced with a smaller value pot and well-selected fixed resistors on each end so that the 40% gets translated into 100%.  Could a company turn out an inexpensive product and have every setting of that pot be consistently useful?  I doubt it.  Plus you have to explain to consumers what the tradeoff is between sweep width and offset/initial.  Hell, as it is, a great many BF-2 owners probably still don't know what the relation between the Depth and Manual control is.

[Sir H C]

Check out the mode zero site for pictures of the roland.  It is cool because that knob is calibrated on the front by the center frequency for the notches, therefore you can tell where the notches are going to be centered around.  A lot of fun.

[swt]

thank you all for the kind replies!. So any particular lfo to look at?. it's for the phaseur. The lfo it's not working properly, and i wanna try something else before boxing it. it's an ldr, 6 stages phaser with regeneration.