Jumpered FX loop in JTM-45 ish amp... I'm liking it!!

[5F6-A]

My main amp follows the 5F6-A circuit with a few later-Marshall twists (in order to control the flapping low-end) and quality components in the vein of the JTM-45:Mullard valves, GEC KT66s and JTM-45 OT by Joe Pampel. It was designed to have only one channel ( two inputs) and a buffered parallel fx loop with a mix pot which uses the unused triode of the V1 ECC83.

I was reading about jumpered inputs in JTM-45s so I thought... If I jumper the fx loop with a very short cable and set the pot to 100% mix I would achieve something similar to jumpering inputs.

So I did and the result has been excellent:

There's not a huge gain increase, not like stepping on a booster pedal: instead the amp's behaviour changes slightly and the tone coming through the speakers becomes fatter, wider and more complex.
It's not like a huge boost in the gain but rather it's like you've added another (quieter) amp in parallel to the previous one and you a listening to both from a distance where both tones mesh into one.
The overall loudness hasn't changed but the tone is more robust.

Any similar experiences?

[Dmoney]

sounds like a cool result for you, though I'm not sure the jumpered inputs and jumpered loop are really comparable. 

Putting the jumper in the loop and turning the mix knob round to 100% i assume (since I don't have the schem of the amp) gives you 100% of the recovery gain stage going to the rest of the amp. That gain stage may be set up to return a signal just higher than unity so you squeeze a tiny bit more cascaded gain out of the circuit. It's neat if you like it. That's a bit different to the jumpered inputs but I'm glad it worked out for you.

In my old soldano decatone, turning the loop mix to 100% had an effect even without a patch lead in place, because the jacks were switching and the loop was always in circuit even though it was a valve buffered series/parallel loop. I didn't really like the effect, but then that amp had more than enough gain anyway.

[5F6-A]

Thanks for the response. The difference is subtle but apparent and the added complexity is something that sounds very cool to my ears.

[5F6-A]

I have recorded a quick clip (please excuse the sloppy playing and low quality recording )

First lick is with the loop jumpered, then similar lick without the jumper

http://soundcloud.com/5f6-a/jump
I think the first sounds slightly fatter and more complex. See what you think...

[HTH AMPS]

Did you recently get the OT off Joe Pampel (aka Speedracer)? - I had some OTs from him around ten years ago that were great, then he just fell off the map.  Would love to get more from him if he's around.

[5F6-A]

I got mine from Joe about 8 years ago or so and then he stopped producing them or being available. A real shame, really.