Estey/Magnatone/Audio Guild "wobbly" vibrato?

[BubbaKahuna]

I have an old Audio Guild "Imperial" combo amp from around late 60s or so.
All tube, 12" speaker in an enclosed part of the cabinet with a tone chamber that boosts the bass response to 'unreal'.

It has the coolest vibrato sound I've ever heard in an amp.
It actually bends the pitch up & down slightly along with the volume throb normally associated with various in-amp Vibratos.
It has got to be the swampiest thing ever stuck in an amplifier.
You can do pedals on "Born on the Bayou", but not like this thing does. Yowza!

Anyone ever reverse engineered this circuit or made a work alike for a stompbox?
That would be too cool.

Cheers,
- JJ

[Processaurus]

I haven't played the amp that you're talking about, but a while ago I was trying to graft different circuits onto my tremolo, that had a fair bit of extra room.  I tried a phase 45 and small clone chorus, my favorite sound was using the wet only of the small clone as a vibrato, into the tremolo, both hooked to the LFO from the trem.  With just a little true pitch bending it added some great character.

[markm]

How about a Brownface type?

[R.G.]

The Magnatone vibrato is a true vibrato, in the same sense that the Univibe provides a true vibrato. In fact, the circuits have a lot in common. The Magnatone amp uses a tube version of the phase splitter plus variable resistor phase shift network like the Univibe.

I think the sound you're looking for is an "imperfect" phase shifter that has some tremolo in it. It wouldn't take much tweaking to make an easyvibe circuit into one of these. May take some dinking to get the frequency response the way you remember.

[Processaurus]

It was interesting, I tried the phase 45 set as a phase vibrato with no dry signal into the tremolo, and could hear it working, but much prefered the pitch bending vibrato +trem combo from the chorus circuit rather than the phase vibrato.  Sounded a bit seasick with the phaser.  That was just a dinky 2 stage phaser though, unlike the 4 stages of the uni/easy vibe.  Seems like with phasers the more stages the better the vibrato effect is.  I remember the vibrato I got from my two phase 100 circuits i have stashed away somewhere was surprisingly decent, and deep, when I ran the two in series.  That was 12 stages...

I believe at tonepad there is a project for the ross phaser that has an add-on board for more stages, that one uses OTAs, so would be straightforward to make an 8 or 12 stage phaser, and use it as a vibrato, in cunjunction with a tremolo you could sync to the LFO.

[Rodgre]

All this reminds me. I need to trace the circuit in an old Jordan Vibrasonic pedal that I have. It does that phasey wobble like the old Magnatone amps. It's similar to the vibrato on my AC30 as well.




I keep meaning to check out a DOD Vibrothang again, which does both tremolo and vibrato/phasing at the same time. I would fear that mentioning it would make it become a collectors item, but it really never sounded as good as it could have without some modding.

Roger

[David]

All this reminds me. I need to trace the circuit in an old Jordan Vibrasonic pedal that I have. It does that phasey wobble like the old Magnatone amps. It's similar to the vibrato on my AC30 as well.




I keep meaning to check out a DOD Vibrothang again, which does both tremolo and vibrato/phasing at the same time. I would fear that mentioning it would make it become a collectors item, but it really never sounded as good as it could have without some modding.

Roger

A Vibrothang?     Don't waste your time, IMHO.  I have one, and think it vacuums.  YMMV.  PM me if you want it.

[markm]

If you have the schem for this, I'd like a copy if possible?