JMI Secrets - Circuit Borrowed from Hammond Vibrato ???

[kagliostro]

Does someone knows which is the Hammond circuit that was stolen ??



Thanks

Franco

[sluckey]

Does someone knows which is the Hammond circuit that was stolen ??

That Vox vibrato circuit was copied from a Wurlitzer organ, not a Hammond organ. See

     http://sluckeyamps.com/misc/Dorf_TheWurlitzerVibrato.pdf

[HotBluePlates]

That Vox vibrato circuit was copied from a Wurlitzer organ, not a Hammond organ. See

     http://sluckeyamps.com/misc/Dorf_TheWurlitzerVibrato.pdf

100%

Sluckey doesn't need me to second-guess his statements, but I agree this is an error in Elyea's otherwise outstanding book on JMI amps.  The circuit was lifted directly from Wurlitzer organs.

[kagliostro]

Many Thanks Friends

At the moment I'm not able to read the PDF because I'm on the phone and seems I must be on the PC to open the file

Thanks again

Franco


EDIT: Problemi solved, I can read the whole text


👍👍👍

[Willabe]

I've read that Gibson got it from Wurlitzer and Vox took it from Gibson. 

[DummyLoad]

IIRC, the early Hammond pitch shifting scheme was electromechanical, with a later scheme that was all electronic employing saturating core inductors.

Steve, wasn't your warbler project based on the saturating core inductor type?

--Pete

[sluckey]

IIRC, the early Hammond pitch shifting scheme was electromechanical, with a later scheme that was all electronic employing saturating core inductors.

Steve, wasn't your warbler project based on the saturating core inductor type?

--Pete

Yes. And the earlier Hammonds did use a motor driven rotating scanner type vibrato.

[kagliostro]

Something that rensambled a circular saw ?


Franco

[sluckey]

Scanner looks like this...

     http://theatreorgans.com/hammond/faq/a-100/fig-28.jpg

Theory of operation. Scroll down near the end of page...

     http://theatreorgans.com/hammond/faq/a-100/a-100.html

[kagliostro]

This is what I was remembering





https://www.quora.com/What-exactly-is-making-the-sound-in-a-Hammond-organ-if-not-air-through-a-pipe-or-reed

Franco

[sluckey]

This is what I was remembering

That is the tone wheel. It generates the sine wave tone you hear when you press a key. For example, pressing the middle C key activates a switch that selects the proper tone for a C note. Quite different from the vibrato scanner. The vibrato circuit occurs farther down the signal path. When that C tone passes through the scanner circuit, the frequency is shifted a little bit below C and a little bit above C, producing the vibrato effect.

That's a very simplistic explanation and may not be totally accurate, but should give you an idea of what's going on.

[kagliostro]

Oh, I understand

Franco

[HotBluePlates]

I've read that Gibson got it from Wurlitzer and Vox took it from Gibson.

We may never be sure how something got swiped.

However, it's worth pointing out that before Dick Denney enters the scene that Tom Jennings is in business selling keyboards/organs.  We might guess Wurlitzer's vibrato was swiped directly on the basis of JMI's business-focus before the AC-amps enter the picture.