Metropoulos Forum

I installed the Metro Zero loss loop in a 2203 with lukewarm results. Although after adjusting the internal trimpot I didnt have any noticable loss with the loop engaged, I do have an amp that doesnt sound the same as before the mod with loop bypassed.
The feel is now stiffer and there's a noticable loss of either gain or some compression. Sounds like someone turned the mid control all the way up. It just honks.. I'm hoping this problem can be solved without having to take the loop out altogether.

I used a 22K decoupling resistor which gave me 310 volts when measured at the loop board. Perfect range according to the Metro literature.
After measuring the B+ from pin 3 of the output sockets after the mod I did notice that the B+ voltages in the amp are now @ 30 volts higher.
Aside from adding the dropping resistor the directions called for a single swap of a 5.6k resistor in the PI where the (2) 10 K's were in series. Seems like this was a big drop. I'm wondering if changing this value a bit could get the amp back where it was before the mod. My original plate voltage was 425 volts.

Voodooamps posted in a RG thread mentioning the loop ideally should be in series with the B+ rather being in parallel to the B+ as the Metro directions detailed to keep it transparent. Transparency of the loop isnt really my issue however. Its possible this may have something to do with why I'm not happy with the results but again, the loop itself seems to be doing it's job, the amp itself sounds really bad with the addition of this loop.

Something has to be tweaked a bit somehow, the voltages restructured possibly. This is unfortunate, my best sounding Marshall is now my worst sounding Marshall.
Any input would be appreciated. Thanks a lot!!

Welcome to the forum. Hopefully this issue of yours will get resolved. Let's try with some pic's...
Has Voodooamps designed an FX loop in series with the B+ ?

Thanks for the warm invite Jimi!
I tried to post some before but it exceeded the allowed pixels. Let's try one at a time.

Had to reduce the picture sizes significantly. Sorry if they're a bit blurry because of it.
I grounded the board to the existing lug on the board near V3.

I'm not exactly sure on the knob side and where it's connected to the phase inverter input cap, but everything from the switch and board side looks to be in order and wired correctly. Yes, Steve's instructions call for a separate dedicated ground. If you don't want to drill then relocate the FX ground from the top of the stand-off to the bottom so that the wire coming from the loop is in full contact with the chassis. Should be easy to do...
Maybe someone will see something else so you can get rockin' !

Steve's been a big help via email. I think i might have it worked out and the loop has been great all along. Im really happy with the tonal results and also the great product support. Im impressed all around!

I wanted to follow up on this post to report my findings. The issues I was having were not related directly to the loop itself.
Looks like the B+ connection on one of the preamp socket was loose.
I would also like to report that this is the best loop I could have possibly hoped for. It's perfect for marshall heads that do not have a loop and it does exactly what it says it will in your amp. ZERO TONE LOSS. The bypass is perfect, complete transparency and when engaged, I hear NO issues.
I couldnt be happy that I can integrate some of my older marshall's into my modern rigs. I've blown away by Steve's loop and his help troubleshooting. Thanks again Steve.