Hoffman Amplifiers Tube Amplifier Forum

Other Stuff => Solid State => Topic started by: tubesornothing on May 16, 2009, 11:52:06 am

Title: Yamaha Leslie Amp - effects out
Post by: tubesornothing on May 16, 2009, 11:52:06 am

A buddy wants to have an effects out installed in his Yamaha leslie RA200 amp.  In looking at the preamp, I see it has a typical SS preamp, then goes to an 3 stage active filter, before being passed to the power amps.  I am thinking to have the effects out after the coupling cap of the preamp, but before it goes to the 3 stage active filter.

Should this be a buffered effects loop?  Anything special I should consider since its solid state?

thanks
ToN



Here are some pics with an arrow indicating where I want it to go:

Lo-res:  http://tubesornothing.myphotoalbum.com/view_photo.php?set_albumName=album01&id=yamaha_leslie_preamp_001 (http://tubesornothing.myphotoalbum.com/view_photo.php?set_albumName=album01&id=yamaha_leslie_preamp_001)

Hi res: http://tubesornothing.myphotoalbum.com/view_photo.php?set_albumName=album01&id=yamaha_leslie_preamp_001&full=true (http://tubesornothing.myphotoalbum.com/view_photo.php?set_albumName=album01&id=yamaha_leslie_preamp_001&full=true)

Title: Re: Yamaha Leslie Amp - effects out
Post by: PRR on May 18, 2009, 02:23:58 am

""The owner of this MyPhotoAlbum does not allow visitors to download their photos.""

? ? ?

> Anything special I should consider since its solid state?

Unlike tube grids, transistor Bases are, in general, NOT at zero volts DC.

That blocking cap assumes TR4 emitter biases around +8V, and TR6 TR7 bases are biased to about +16V. Your effects jack(s) must be at zero V DC. To build a full send-return, you must turn-around the first cap and add a second cap. For just a Send, there is another way to do it, but it comes to the same number of parts, so do it this way except the "return" is just fed from the Send.

Title: Re: Yamaha Leslie Amp - effects out
Post by: tubesornothing on May 20, 2009, 11:27:03 pm

PRR - thanks very much.  SOrry about the photos, I thought they were publicly viewable.  I appreciate you digging one up. 

Thanks for the tip on the cap - that I would have never figured out.

Should I have any consideration for buffered/unbuffered?

thanks
ToN

Title: Re: Yamaha Leslie Amp - effects out
Post by: PRR on May 21, 2009, 05:58:35 pm

> I thought they were publicly viewable.

Viewable, yes. But to mark-up the plan, it would be convenient to download the image so I could load it into an image editor. Instead it seems to want to sell me prints?

My work-around was "screen grab", but that's awkward.

http://tinypic.com/ is a good no-frill image host.