Leslie 122 preamp

[jstark]

Hello,

I picked up a Leslie 122 for a song, and I'd like to start using it with my Nord Electro.  I was wondering if anyone would be willing to give feedback on this sketch of a preamp:




There are a couple other great threads for similar projects, but the images are nowhere to be found...

Any obvious errors with this circuit?


thanks!
David

 

[ruffrecords]

Which valve does it use?

Cheers

Ian

 

[jstark]

D'OH.

12AU7.



thanks,
David

 

[BYacey]

Looks to me that it could use an input coupling cap in place of the 10k resistor, and you may want to add some bypass caps across the cathode resistors, depending on how much gain you're looking for.

 

[jstark]

Looks to me that it could use an input coupling cap in place of the 10k resistor, and you may want to add some bypass caps across the cathode resistors, depending on how much gain you're looking for

thanks! should have drawn the input C on the schem. 

I don't need a ton of gain...but I do intend to put the turrets in place so at least I can easily experiment with cathode bypass caps.

 

[dmp]

What's the deal with the switch connected to B+ and the output transformer?

 

[jstark]

It puts a DC control voltage on the  signal lines, which is then used inside the leslie amp to control the motor relay.

 

[Reo]

Thanks for posting jstark, I might build one of these too. Are you going to make yours a standalone box or try and mount it inside the leslie cabinet?

 

[jstark]

Yeah, I'm going to mount it in the cabinet.  I just got all the parts in the mail so the next step is mocking it up.  The current idea is a small enclosure that will get hung directly above the existing amp, as long as this doesn't interfere with the lower motor and/or tensioner...

I'll keep this thread updated with progress.


David

 

[plimousse]

Hi,

Please find attached the schematic diagram

Cheers,
Pascal

 

[bernbrue]

If you need a nice tube preamp for keyboard saturation/distortion you should have a look at my Rude Tube Ivory project .  Schematic is almost identical to the Leslie preamp plus a nice three band tone stack. You'll find pcbs here: http://groupdiy.com/index.php?topic=53011.0
Build thread: http://groupdiy.com/index.php?topic=56356.0
Bernd

 

[pucho812]

as much as I like DIY get yourself a trek II uc-1a  You will not regret  it...

http://www.b3guys.com/Trek+II+UC-1A+Combo+Preamp.html/product_id/51