FX loop on vintage amps

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Ahahah
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FX loop on vintage amps

Post by Ahahah » Sun Nov 26, 2006 9:36 am

Some stuff was available for vintage amps from Stewart Mac Donald's a few years ago. It was a device with tubes that had to be mounted on the amp circuitry...
I had a doubt back then and never bought it (didn't want to modify my lovely Deluxe Reverb).
Now that I'm ready to do so (I've a reissue) the thing seems to be unavailable.

Has anyone ever seen this ? 

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pullover
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Re: FX loop on vintage amps

Post by pullover » Sun Nov 26, 2006 2:49 pm

The only FX loop mod I have heard of for Vintage Fender Amps is through the amps reverb send and return. Some one else might know more.

"One neat trick you can do that doesn't alter the amp at all is to use the reverb driver as the effects send signal, and return the effects output to the reverb return jacks. Set the effects for 100% wet, and dial in the blend with the reverb knob. Be sure to do two things first, though--

1) Make sure that the reverb driver transformer is properly terminated. Build a small box with a pair of pass-through jacks. Set up the reverb send pass-through with an RCA jack (in) and a 1/4" jack (out) and an 8 ohm/10W resistor tied across the signal line (hot to ground) to properly terminate that reverb driver transformer. The return side can be a simple, 1/4" to RCA pass-through to prevent the need for wierd adapter cables of dubious quality from Radio Shack or the like....

2) If using a line-level (or pseudo line-level) effect unit, start with the output level knob fairly low, and run the amp's reverb knob about halfway up to avoid distortion. Remember, since the reverb tank's signal is /very/ small, the gain stage is set up to reflect that, and it may distort if the effect output is to high....

For the price of a project box, a resistor, and a few jacks, it's a heluva non-intrusive "mod"....."

For those of you with Fender Blues Devilles and the like which have SS drivers for the reverb tanks (also all you SS amp guys), you can forget the
requirement for loading the reverb driver output. It's only to save the tube-driven driver transformers, which /will short out/ if not properly terminated and dump the preamp B+ to ground through a dead short (no sound) or a high-resistance short (dirty sound at most volumes, weak output--check for lower-than-normal preamp B+). The SS drivers son't seem to have this problem, so enjoy...."  http://www.harpamps.com/micKfender/Fend ... -loop.html
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Ahahah
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Re: FX loop on vintage amps

Post by Ahahah » Sun Nov 26, 2006 11:55 pm

Thanks very much !!!

This is a very valuable advice !

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