Zero loss FX loop and 1959/1987 circuit issues

SilkWilk

Member
Joined
Oct 1, 2019
Messages
44
Reaction score
19
Ive got a 100W Rockitt Retro plexi-style amp. Its got Metropolous zero loss FX loop installed from the factory and a PPIMV. I've never had much luck with this loop. I read great reviews online and hear great sound clips as well but whenever I try putting verb or delay in the loop with any amount of decent gain I just get harsh dirty repeats.

So far the only pedal I've tried is a zoom MS-CDR70 multi FX pedal that has served me very well over the years with other amps. I've tried adjusting the levels within the pedal, and I've also adjusted the level switch on the FX loop board from -20 or +8 I get the same harsh nasty sound either way.

I still havent ruled the pedal out - but wanted to get your guys thoughts - this loop seems to work great with JCM style amps but is this loop really Truley suited for NMV amps that are crunching the phase inverter/power amp section?

I was considering picking up a run of the mill standard reverb pedal like the TC Hall of Fame...etc somehting with a instrument level input. just to see. I've also wondered if perhaps I should throw a buffer pedal with a level control into the loop to see if I could gain more control of the level the pedal is seeing.

Something just doesn't seem right and I'd love to have wet effects when playing. I've considered going wet/dry and also would love to just grab a PowerStation or bad cat unleash and have the post FX happening there but feel I need to address this issue first if I have a loop in the amp.
 

Pete Farrington

Well-Known Member
Joined
Jan 18, 2021
Messages
1,324
Reaction score
1,423
Location
Staffordshire UK
whenever I try putting verb or delay in the loop with any amount of decent gain I just get harsh dirty repeats.
With a type 1,2 or 3 master volume after the phase splitter, the phase splitter will be clipping the signal after the loop, so that’s to be expected.
If turning the master volume down, to avoid that, you’ll need to put fx after the amp’s speaker output, eg with the unleash, power station mentioned.
Or swap to a type 4 master volume, 2203 style. But that would lose a lot of the depth of overdrive currently available.
 
Last edited:

SilkWilk

Member
Joined
Oct 1, 2019
Messages
44
Reaction score
19
With a type 1,2 or 3 master volume after the phase splitter, the phase splitter will be clipping the signal after the loop, so that’s to be expected.
If turning the master volume down, to avoid that, you’ll need to put fx after the amp’s speaker output, eg with the unleash, power station mentioned.
Or swap to a type 4 master volume, 2203 style. But that would lose a lot of the depth of overdrive currently available.

Thanks Pete, I wondered if the PPIMV type/placement was part of the issue. I have not really tried to play the amp with the ppimv out of the circuit and turned up loud enough for Van Halen style gain. I will have to test that out to see if the FX in the loop behave better when the PPIMV is out of the circuit.
 

XTRXTR

Well-Known Member
Joined
Feb 14, 2021
Messages
901
Reaction score
1,021
Location
Some City, USA
I'll just second what Pete said, the PPIMV allows the PI to overdrive what is put into it within a very small window of overdrive - range. I tried a PPIMV on my 2204 for a short time. I scoped the input to the PI and the output and was surprised how little signal it would take (6 Vpp) before it distorted the preamp signal to ridiculous garbled crap.

Mind you it was a 2204 so there was already plenty of overdrive available between V1a&b. But the point here is that the FX loop in a 1959 or 1987 usually connects between the tone stack treble and the input of the PI the same points where a normal or Pre-PIMV or what Pete is stating a Type 4 would be placed.

Thus a good electronic architecture to connect the FX loop and a type 4 MV if you decide to go that way, may be to place the type 4 MV after the return of the Fx loop and prior to the PI.

Of course taking time to experiment with pedals in the inputs for more overdrive and various tones without the PPIMV could be very helpful while using the FX loop so you can really get good representation of all the types of songs and tunes and guitar sounds etc you may need to use. Do that before making a decision about using a type 4 MV. That could save you some tech work. Perhaps use an attenuator for the actual output decibel level control.
 

Latest posts



Top