HI-Z guitar to Leslie Pre Amp with Hamptone JFET amp block?
« on: December 15, 2010, 11:49:05 PM »
A friend of mine wants me to build him a pre amp for his leslie 125, and the Hamptone JFET amp block came to mind. I've built the JFET blocks before and they sound great for guitar DI, I imagine it would work alright as a Guitar to Leslie pre amp, but I don't have a leslie to test it with which is the problem. Is there any schematics for anybody who has taken on such a project before???

My plan is to do 4 footswitches, for Bypass, Fast, Brake, and Slow

But I'm not sure how the switching will work, hopefully I can find some documentation or a schematic somewhere. Would it be possible to have a continually variable pot for the leslie speed, and then just add one switch that would double the speed of the motor?

I think adding a line in wouldn't be a bad idea either.

Any comments, tips, suggestions would be greatly appreciated! Thanks!


Re: HI-Z guitar to Leslie Pre Amp with Hamptone JFET amp block?
« Reply #1 on: December 16, 2010, 12:37:07 AM »
Scratch that its a Leslie Model 25 not 125

abbey road d enfer

Re: HI-Z guitar to Leslie Pre Amp with Hamptone JFET amp block? New
« Reply #2 on: December 16, 2010, 03:40:32 AM »
The preamp is probably the easiest part here.
The switching is a little more difficult.
The speed change is done by using two different motors in the Leslie, so there's no way to make it continuously variable.
You need to know what type of cabinet (6-pin, 9-pin or 11-pin connector). The speed control is done in the cabinet via a SPDT relay; most cabinets have a relay driver (vacuum tube or solid-state), some don't (the 147 is an example). For the BRAKE function, on a 6-pin Leslie, you need an additional relay in the cabinet, and an additional control line.
The 9-pin cabinets have separate control ports for Slow and Fast. Brake is when both motors are de-energized.
A good basis is there:
Now, I don't really understand what a ByPass switch would do?

EDIT: Now I see that it's a Model 25. 6-pin connector. You need to modify the cabinet for Brake mode.
« Last Edit: December 16, 2010, 06:17:42 AM by abbey road d enfer »
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.


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