leslie cabinet preamp pedal

[gdmart]

hello,
Im wondering if anyone has info schematics/layouts for a preamp pedal for a leslie speaker cab. needs on off fast /slow.anyone here built one??

[NoFi]

Hi, i really don't know what you mean by "preamp" pedal. I have some kind of leslie vibratone i got from an old hammond organ, the switching circuit is very simple. Basically, it just switches the AC between the two motors by using relays.
There you go (schem + layouts) :
http://thebin.free.fr/Leslie/

Then all you need is a double footswitch and you get On/off with one switch, and slow/fast with the other.



Hope it can help, it will probably depend on what type of Leslie you have.

[Joe Hart]

I have been looking to build one for a while, but the AC current makes me a little concerned (not for my safety, but the safety of my Leslie cab). I do have a schematic. I'll try to dig it up.
-Joe Hart

[Joe Hart]

Here's a link...

http://www.captain-foldback.com/Leslie_sub/combo_preamps.htm

-Joe Hart

[Peter Snowberg]

I've never built one.... but I gave it some thought.

My Leslie has a motor for the woofer and another one for the horn, but each is a single speed motor. With both motors, fast is just too fast.

I like too many switches, so my control idea includes an on/off switch for each of the two motors, and a speed control for each. Two switches and two speed knobs doesn't seem out of line for controlling a dual phaser.

The deluxe version would have four speed controls and a fast/slow select stomp switch for each motor.

For the preamp part... what model Leslie do you have? You can just adapt the front of any tube guitar amp. I have a Leslie 122 which takes a differential input to get rid of hum from the speaker cable. For that model all you have to do is clone an amp up through the phase splitter and feed it to the power amp. Hammonds use a balanced transformer output which doubles as a phase splitter.

If you're not into building tube amps, I would suggest using any of the one chip amps out there. You really don't need much wattage to be really loud. 700mW is amazingly loud when driving it.

http://theatreorgans.com/hammond/faq/schematics.html

[Joe Hart]

Mine's an old 147. And by the way, it's not very loud when hooked up to my Yamaha organ (and the Yamaha is actually made to drive a Leslie cab, so it's not some problem with an external component). The Leslie also distorts (not in a good way) when I hit any low notes. Any ideas?
-Joe Hart

[NoFi]

Maybe the speaker is getting old, maybe the amp needs a cap job...
Now i understand what are those preamp switching pedals. It looks easier to me to build a separate switching circuit, and use whatever preamp you can find.

[Peter Snowberg]

This should be the schematic for your amp:

http://theatreorgans.com/hammond/faq/files/schematics/145mn-a.pdf

If you have a pair of 6550s in there, you should get some serious volume. You may have a bias problem.

Was the Yamaha made to drive a 145/147 amp or a 122 amp? The 122 amp uses DC voltage on the signal inputs to switch motor settings. That would mis-bias the input stage.

A pair of 6550s produces some serious volume. Just look at all those "50W" Marshalls.

FOr comparison of the inputs, here is the 122 schematic:
http://theatreorgans.com/hammond/faq/files/schematics/122mn-a.pdf

[Pedal love]

I have a leslie 760 top and bottom, with a trekII universal preamp. I like the way the baffles are pulled and need a circuit, maybe a variac that can alter just the motor's ac. Potentiometer-variable speed would be awesome.pl