RG Keen's LERA (Leslie Effect Rotor Adapter) - schematic and more inside

[notnews]

Hey all
I stumbled across this.. the idea really intrigues me. It replaces/augments the "speed" control on any LFO- type effect, simulating the behavior of a rotary Leslie. I started translating this to vero but had some trouble.. would anyone be willing to take a stab at it?

Looking at the design, I think this works by ramping the speed either up or down like a leslie does when you switch from fast to slow or vice versa. I'd love to open a discussion about this circuit if anyone wants to analyze it and share their thoughts.

Schem:


I also found wiring diagrams for building the LERA inside of and outside of the main effects box:



A little more digging turned up a design someone made integrating the LERA into John Hollis' EasyVibe circuit (hand-drawn vero):

[notnews]

A little more digging... I found a better EasyVibe schem w/ and w/o the integrated LERA:
http://www.geofex.com/FX_images/ramp-lfo.pdf

And the MXR Phase 90 w/ and w/o the LERA:
http://www.geofex.com/FX_images/p90ramp.pdf

I am really interested in how the ramping circuit sounds.. would love some feedback from this community

[MAO]

This should work...

[notnews]

Thanks so much MAO..
What do you think about the idea behind this circuit? just curious if it seems as appealing and interesting to you as it does to me.. I may have the wrong idea about what this circuit is capable of..

[Neil mcNasty]

About the LERA:
It is not an effect, but a simulation of a speed feature/limitation found on Leslie Speakers, where you had two different speeds to choose from, and since the Leslie has a heavy physical object that had to change it's rotation speed to change tempo, it would then increase/decrease the tempo gradually, because of the weight it has to pull/break.
This is known as the Ramp Up/Down effect, and therefore the name LERA for this circuit.

It does not affect the sound at all, it simply enables you to get this Ramp Up/Down feature, making it "fade" between two Tempo/Speed settings.
When looking at this circuit a couple of years ago, I did not understand the circuit very well, and I then had the impression that it was not something that could be added to any LFO, but only for a certain type of LFO. Hopefully I was wrong, since this is a very nice feature that I hope some brilliant minds here could be able to crack the code on, and figure out how to implement this to many different LFOs.

Regarding the vero:
I suspect that the speed controls of the LERA (Slow Speed & Max Speed) could be moved off-board, since the LERA replaces/bypasses the original speed pot when trowing the switch that activates the LERA.
So when building it into an effect from scratch, it is being hooked up directly to the circuit without the activation switch and it is replacing the original speed control.
The old ramp/dual speed controls that we find in old effects, normally had these as trimpots inside, so that you had fixed slow and fast speeds.
These days people want more control over their effects, so that is why I suspect that these two speed controls could be nice to have off-board...
Does that make sense to you guys as well?

Looking forward to see how this turns out...

[Beaker]

I am familiar with this "effect" with a Leslie speaker, take a look at this video:



You can clearly see the horns and the wooffers accelerating and decelerating on it - and that is with a perfectly working model. As the drive belts wear and loosen, it takes progressively longer to speed up and slow down.

I would love to stick this in a tremolo pedal for a start!

I also seem to remember trying a vibe pedal  (maybe a Hughes and Kettner) in a shop a long time ago. If I remember right, it had a momentary footswitch that acted like a break pedal - step on the switch, and the vibe slowed down to a standstill. Release your foot and the speed increases to normal. I thought it was a really cool feature.

[MAO]

If anyone is interested, I'll modify the Phase 90 layout on the main site to include the LERA as shown in the link.

Phase 90 with LERA

Or maybe draw up the Madbean NomNom with the LERA.

Let me know

 

[notnews]

I'd love to hear how this sounds with a Phaser or a Flanger.. if you could augment the Phase90 layout with the LERA that would be awesome, MAO! I'm not super familiar with the NomNom, if you think that would be a better pair then definitely shoot for that combination instead.

Question.. so replacing the "speed" potentiometer with the LERA, does that then limit the "speed" of whatever effect you're augmenting to the two speed dictated by the LERA circuit? If so, maybe it would be a good idea to have a LERA/IntrinsicSpeed switch to choose between the LERAs speeds and the original "speed" pot's speed, no? Unless there is already a way to choose an arbitrary speed with the LERA...

[MAO]

The Phase 90 would probably be easier since the layout is already out there, but I have built the NomNom, added a depth control and it sounds great!

I may do the NomNom, I don't think we have that one posted yet.

It looks like we may be able to use a 4PDT switch to choose between the Speed pot and the LERA.

Hmm, now I'm interested in it too...I'll get on it.   Thanks for bringing it up!  

[Beaker]

Re. your question, I would love to see daughter board version (as above) but with a trimpot for minimum speed rate,  a trimpot control for acceleration/deceleration rate, and a rate indicator LED for good measure. That way this could be added to many effects with minimal extra drilling for additional extra pots and switches - you would only need a LED hole and footswitch hole adding!

The idea of using a momentary footswitch to "brake" the speed of an effect is really appealing!

EDIT: the way I was looking at this suggests the "original" speed is still maintained by the pedal, and the LERA only adds a minimum speed and accelerate/decelerate rate? Am I wrong?

I think I'm confusing myself now

[notnews]

Beaker - the full LERA schematic has a switch for "up/down", which (to me) suggests that you can use the LERA to accelerate up towards a speed1 dictated by the LERA, or accelerate down to a speed2 dictated by the LERA... that said, I don't see any "max speed" or "min speed" pot in the schem. I do know that it was designed to eliminate the speed pot on the original effect to be entirely replaced by the LERA. With the original speed pot gone, how would the effect know what the removed speed pot is telling the circuit?

TBH I'm also confused.. hope I'm not confusing anyone more than they were already!

[Travis]

I haven't looked at the LERA schem to be sure, but if it doesn't have a speed pot that may be by design. The Leslie didn't have a speed pot either, it was "fast" or "slow"

[notnews]

That's what I'm thinking.. the LERA has a "Down Speed" pot and a "Max Speed" pot. The LERA replaces the original speed pot on the pedal with two speeds and the ability to ramp up/down between the two... that's why I thought having the ability to bypass the LERA and access a full-spectrum speed pot (like the speed pot in the original) would be helpful, that way a user can access an arbitrary speed with the speed pot, and then engage the LERA to ramp up and ramp down between two speeds dictated by those two LERA speed pots.


The golden goose, I think, would be to have one of the LERA speed pots double as BOTH the max speed (or min speed) pot in the LERA circuit, and ALSO the original speed pot. That way when the LERA is engaged, the speed doesn't have to change to either the max or min LERA speed. You can have the "max" speed set, for example, engage the LERA and the speed wouldn't change, then be able to ramp down to the min speed and back up to the max/original speed. (Or up and back down to the original speed if the min LERA speed pot is the original speed and the max LERA speed pot is the ramp direction).... does that make sense? It sounds feasible with the right XPYT switch, just not sure exactly how to implement that.

That said, maybe just making both speed trims in the LERA external would accomplish what I'm set out for...

Sorry to use this space as a stream-of-consciousness notepad... hope I don't annoy anyone!

[MAO]

Well here goes....

Madbean NomNom with Depth and LERA