Merlin's Practical Serial Effects Loop layout

[telentubes]

I was going to put a .01uf right after pin 6, then start the loop after that. The return of the loop would head to the Master Volume right side lug. The left lug would go to ground. The wiper will go to the PI, via a 1k2 resistor then a .02uf cap. Thanks for that reminder. Could be easy to forget with it missing on the schematic.

[studiodunn]

Do pins 4,5&9 all need tied to ground?

[martin manning]

4, 5, and 9 on the 12AX7? They have to be connected into the filament string.

[telentubes]

I just finished this up yesterday, so the timing of your question is perfect. It's near impossible to see all that is going on here, and I will try to get some better shots to post, but this gives a layout option. The heater wires are attached at pins 4/5, and 9, like the other preamp 12AX7s.

Merlin's effects loop.jpg

[M Fowler]

Beautiful workmanship there.

[studiodunn]

Thank you Martin, I typed before thinking.

Tele - That is stellar looking work sir. Thank you for making me embarrassed to post my gut shot

Loop works great! I have some strangeness in how the MV and Treble are working in conjunction, But I think I have and idea of what I've wired up wrong.
I'm using a Stereo jack since the pedal I built to use is set up the same way...one less cable to deal with.

I'm going to try a few things and will report back, but again, thank you all.

IMG_2242 (2).JPG

IMG_2243 (2).JPG

IMG_2241 (2).JPG

DSC01008.jpg

[studiodunn]

Got this all sorted and working great. I have zero tonal change and unity gain.

The only issue being a scratchy MV now. It almost drops the signal momentarily and then recovers once I stop turning the pot.
The loop is placed between the Tone stack and the MV.
Any suggestions?

[JazzGuitarGimp]

Do you have an AC coupling cap between the loop output and the MV pot?

[studiodunn]

Do you have an AC coupling cap between the loop output and the MV pot?

Doh! Thank you JGG.

[gsb]

Hi !
I,m building jtm45 with PPIMV. I have Merlins book but question is -to do or not in that build .Player has some TC delay etc .
Thanks for help
gsb

[dorrisant]

Modulation effects are best in the loop with that model...

[gsb]

Hi !
For JTM45 i think parallel will be better or not ?
Thanks GSB

[dorrisant]

Hi !
For JTM45 i think parallel will be better or not ?
Thanks GSB

Maybe, maybe not... Depends on personal taste. You could have it serial or parallel by installing a switch. Most people would say serial though.

[wattsup]

I want to try this. If I were going to put a control pot on the return, would I put a 1M pot in place of the 1M resistor, or put a coupling cap after the 100K resistor and then a 1M or something like that value going to the phase inverter?

[xtian]

I want to try this. If I were going to put a control pot on the return, would I put a 1M pot in place of the 1M resistor, or put a coupling cap after the 100K resistor and then a 1M or something like that value going to the phase inverter?

Just replace 1M with pot. To me, this is unnecessary, because the Send level control covers that base.