Has Anyone Tried To Do A SS Version Of The Magnatone *True* Vibrato?

[Mark Hammer]

Well now you've made us curious.

[Paul Marossy]

Well now you've made us curious.

I'll have to do some kind of recording in the near future

[Eb7+9]

I think the use of independent LFOs to reduce the periodicity is key to making it more animated than dizzying.

Nothing to do with topic at hand Mark (re., Maggie emulation)

Running two independent LFOs would be the same as running two separate chorus pedals into two different amps ... producing a confused effect /not what Don Bonham's idea is about at all

To make his idea shine you need a well balanced phase/anti-phase LFO (not hard to do) and equal modulation amounts in parallel channels heading in opposite direction  .. requiring careful matched variable resistance sets, not a big all around favourite perhaps

[Mark Hammer]

I'm saying that the phase/anti-phase arrangement is not as aurally pleasing as the aperiodic "two separate" arrangement.

That said, because a single-stage (or even two-stage) vibrato circuit doesn't produce a strong pitch shift, a phase/anti-phase arrangement would not be awful, but would produce a jiggly "nervous" quality to the sound, rather than any sort of "roller-coaster" up-and-down, going from side to side.

For me, the poster child for why an aperiodic (unsynced LFOs) arrangement is better is the old Ibanez Flying Pan.  An intriguing sound...for about 20 seconds, and then an instant source of migraines.  The idea for a panned phaser sound isn't/wasn't a bad one, in principle.  The problem was that the high-contrast movement of the output - now-it's-here-now-it's-there - in tandem with the sweep of the phaser, was like trying to keep track of two rambunctious untethered toddlers in a crowded shopping mall.  Just waaaay too much to attend to.  A gentler phasing effect, or a gentler pan, would have improved the product, and transformed it from two toddlers loose to two toddler fidgiting in a stroller.  In the case of Don Bonham's idea, the gentleness of the pitch-wobble makes it manageable.

Why do I think aperiodic is better, from a perceptual perspective?  Because its unpredictable nature means one can, and does, direct attention away from the side-to-side modulation, and simply pay attention to the overall effect.

[Paul Marossy]

a single-stage (or even two-stage) vibrato circuit doesn't produce a strong pitch shift, a phase/anti-phase arrangement would not be awful, but would produce a jiggly "nervous" quality to the sound, rather than any sort of "roller-coaster" up-and-down, going from side to side.

Just a side note about my build. I noticed that when I have the intensity all the way up I get kind of a combo of slight tremolo and the side to side movement too. It's interesting to watch on the scope. I need to try this thing on my amp(s) this weekend to see how it works outside of my headphone only environment.

[Rob Strand]

http://moosapotamus.net/files/stompboxology-vibrato-rama.pdf

[samhay]

I've been down this rabbit hole before:
https://www.diystompboxes.com/smfforum/index.php?topic=111802.0
There is an analogue version and sound clip in post 12.

I then built a PIC to do an LFO with 2 outputs that vary in phase between 0-180 degrees. I also played around with one where the phase varied via another slower LFO. Sounded interesting, but also somewhat nauseating.

Ultimately, a 2 stage phase shifter with stereo outputs modulated 180o out of phase sounds good and is worth building if you like that sort of thing. If you built 2x 2 stages as per the Magnatone, I imagine it would be lovely. Must put that back on the list.

[bool]

Interesting, I had a self-buit 2x2 stage "phaser" in 80's, with metal-can 741s...

[Paul Marossy]

http://moosapotamus.net/files/stompboxology-vibrato-rama.pdf

That's interesting... looks like a good read

EDIT: That looks like it's from Boscorelli's Stompbox Cookbook. I have that in PDF form. Or it looks very similar anyway.

[anotherjim]

If you want other than 180deg phase shift in the LFO's, you can, if it's a form of phase shift oscillator, pick an intermediate point along the RC-RC-RC network and buffer it so it don't load the oscillator out of whack. This is how some 3 phase ensemble choruses work. An alternative is a quadrature LFO.
180deg shift can be a bit unpleasant, especially over headphones.

[Rob Strand]

That's interesting... looks like a good read

It's a while since I've read over it but I remember reading about the Magnatone somewhere.

Has anyone got data on the Magnatone VDR's?

[Paul Marossy]

Has anyone got data on the Magnatone VDR's?

I've heard from some reliable sources that the specs on those are unknown. I think about 10,000 other people would also like to know that! 

[Rob Strand]

I think about 10,000 other people would also like to know that!

  Ah, it's one of *those* issues.

[Rob Strand]

Interesting,

https://dalmura.com.au/static/Magnatone%20vibrato%20design.pdf

page 4, info on Varistors.


Cool, full data,
https://www.datasheetarchive.com/233BNR-32-datasheet.html
https://datasheet.datasheetarchive.com/originals/scans/Scans-94/DSAIHSC0006535.pdf

Some general info,
https://ia600105.us.archive.org/19/items/TNM_Thyrite_varistors_quick_catalog_1963_-_Genera_20180115_0183/TNM_Thyrite_varistors_quick_catalog_1963_-_Genera_20180115_0183.pdf

[Paul Marossy]

Interesting,

https://dalmura.com.au/static/Magnatone%20vibrato%20design.pdf

page 4, info on Varistors.


Cool, full data,
https://www.datasheetarchive.com/233BNR-32-datasheet.html
https://datasheet.datasheetarchive.com/originals/scans/Scans-94/DSAIHSC0006535.pdf

Huh, you must have spent a fair amount of time researching to come up with that. That is indeed very cool. That seems to be everything we ever wanted to know about the Magnatone vibrato varistors. 

[Rob Strand]

Huh, you must have spent a fair amount of time researching to come up with that.

Hard to believe but I found that first doc fairly quickly (maybe Varistor was the keyword).  The document is hot off the press in 2019.  Couldn't believe my eyes that someone had written it all up like that.    A big thanks to the author Tim Robbins!

[Paul Marossy]

Huh, you must have spent a fair amount of time researching to come up with that.

Hard to believe but I found that first doc fairly quickly (maybe Varistor was the keyword).  The document is hot off the press in 2019.  Couldn't believe my eyes that someone had written it all up like that.    A big thanks to the author Tim Robbins!

Huh that must've been published right after my failed attempt at a Maganatone-esque vibrato which prompted this whole thread. I waited a few weeks before admitting defeat and asking questions here. IIRC I started messing with it last December.

[Rob Strand]

Huh that must've been published right after my failed attempt at a Maganatone-esque vibrato which prompted this whole thread. I waited a few weeks before admitting defeat and asking questions here. IIRC I started messing with it last December.

Pretty bizarre.  The internet is fluid place.  I've had the opposite where I found some stuff but I didn't have time to look at it.  Come back the next week and bzzzt completely it's vaporized.   That's happened to me more than once.

[Paul Marossy]

Huh that must've been published right after my failed attempt at a Maganatone-esque vibrato which prompted this whole thread. I waited a few weeks before admitting defeat and asking questions here. IIRC I started messing with it last December.

Pretty bizarre.  The internet is fluid place.  I've had the opposite where I found some stuff but I didn't have time to look at it.  Come back the next week and bzzzt completely it's vaporized.   That's happened to me more than once.

That happened to me several times early on so that's why I save stuff onto hard drive (and back that up) or print it out. I have one whole bookshelf of various categorized 3-ring binders of printed stuff... schematics, articles, etc. and a lot of MS Word docs too (most of which is printed out but is also backed up in several places). Coming from the time when CAD first started being in widespread use, I learned to back up the back ups because things got accidentally deleted, or a hard drive crashed, a floppy disk failed or whatever.

[Mark Hammer]

Up above my bench right now.