Watery vibrato/phasing a la Ludwig Phase II/Synthi Hi Fli

[Rodgre]

I know that both the Hi-Fli and the Phase II are among the rarest and holy grailest of vintage pedals, and I'm almost certain that after paying through the nose to buy one, I'd be a little disappointed that they didn't do more than they do. Still, I'm really fascinated with the fact that I don't think there are any other pedals or effects that do what they did. Nothing else really approximates their circuitry.

Without really trying one out, I can't be sure, but I would love to find a circuit that would give a watery vibrato effect like I assume is the Hi-Fli, on Pink Floyd's Dark Side of the Moon record (guitar solo on "Any Colour You Like," backup vocals on other songs...) I'm thinking that the Phozer or a Phase 45 circuit might get me close. Any thoughts?

Also, the Ludwig Phase II has been discussed a lot, but I don't think anyone has even been tempted to tackle building one off of R.G.'s circuit tracing. Am I correct in thinking that a similar vowel-like filter effect could be made by controlling two resonant bandpass filters, set a certain distance apart, frequency-wise, with the same LFO? It's all beyond the scope of what I can whip up in a weekend, but I'm really fascinated by the concept.

Any thoughts?

Roger

[nordine]

its very funny that  when i did read your  post, i was finishing playing in an experimental phaser i got running.. experimental because it gots 'parts' from lots of not only phasers, but modulation devices... sounds real cool....

and yeah, i got that any colour you like sound... i think it should be pretty achievable with a phase 90 (phase45 too subtle), fiddle with the bias until you get to the bright side of the phase shifting, then crank the resonance to maybe its limit.. that should do

[R.G.]

I haven't even worked up the nerve to do a Ludwig. You are correct that a similar vowel like sound could be made with two bandpass filters being moved around, but they can't move in synchronism. See my article at GEO on the Sing-Wah (

http://geofex.com/Article_Folders/sing-wah/sing-wah.htm

) for a diagram of the vowel formant frequencies. Simply running an LFO on two bandpass filters might run through a couple of vowel regions, but what most voice pedals shoot for is to have F2 run from 800 to 2500 while F1 runs from about 400 up to 1000 and then back down to the low 100's. That path on the formant diagram takes you through most of the interesting vowels, leaving aside "u" and  "er".

There is a project in the back of my head to have a PIC put out a set of control voltages with a PWM output to run you through an interesting set of vowels, may be more than one, selectably, that would be both musically and vocally interesting; for instance, having the LFO cycle run through "oo-ah-oo-ah..." or maybe "eeeee-oo-ow" when a specific switch it pressed so your guitar could yell. Someday, someday. So many things already designed...

But I'm wandering again. See if you can find yourself a Multivox Fullrotor MX-2. This is a phaser along the lines of the hi-fli, but set up to be a leslie emulator. I bought mine from England and rebuilt the power supply. This unit does that massive, watery phasing as well as having a speed-up/slow-down LFO. The Multivox Little David "LD-2" is the same circuit but in a small wooden box that looks like a leslie cabinet. The MX-2 shows up on ebay from time to time. There's one there now, offered from Japan for about $199 BIN. Sometimes they're cheaper, as very few people know what they are. I paid $300, as it was a time of scarcity when I bought mine. The owner actually hand carried it from England to Austin, but that's another story.

"But what's the circuit like?" I hear you asking. It's a 10 stage phaser implemented in the same way as the Moog transistor ladder filter by rearranging the capacitors on the ladder, and using darlingtons. There are about 40 transistors in the ladder alone. It's one of the few circuits I've ever spent the time to trace out that I just said to myself "You know, it's easier to buy this one. Fewer hours needed to work and earn the money."

[Processaurus]

http://www.diystompboxes.com/smfforum/index.php?topic=45628.0

I'd actually be willing to get rid of it for an offer I couldn't refuse, as it is a rare and an interesting bit of electronics, but it hasn't found its place in music I play so far...

Out of general curiosity, I wonder if regeneration would work in the fullrotor, I've heard it doesn't work so well in the univibe type phasers as the usual phasers.

The sequenced formant filter idea at geo is compelling, I would very much like to try something like that sometime.

[nordine]

Out of general curiosity, I wonder if regeneration would work in the fullrotor, I've heard it doesn't work so well in the univibe type phasers as the usual phasers.

i think more than 'doesn't work so well', its a matter of how its done... some regen paths produce awful sounds, some are nicer and give you chewy sounds (ala small stone) ...some variables worth considering on regen are: negative/positive/both feedback, buffered/unbuffered, amount of bass frequencies on regen path, stage on which it's regenerated the signal

[ulysses]

hey rg,

did you ever get a successful trace out of the ludwig phase II? working in spice?

i'd be keen to give building one a shot.

cheers
ulysses