Zero Loss FX Loop

[Spencerleehorton]

Hi All,

wanted to know a bit more about fx loop designs for marshall JTM45/plexi amps.
Before ive bought the metro fx loop but wanted to explore the design or other designs and get my own pcbs printed or i can prototype a single layer version.

the friedman/ceriatone design i have put into LTspice and so far it doesnt seem to do what i thought it would, but the question is what signal levels are at play here?
for the send if i am inputing 1v i seem to get only 80mv out? is this the correct level?
for the return if i input 1v i only get 8mv out?

where as this other design seems to have much more level and adjustment



is there a better design for these amps?

is there a better design for the LND150?

 

[ruffrecords]

R3, R4 and RV1 as drawn will attenuate the input signal by about 20dB. I am not familiar with the JTM45/plexi amps so I have no idea if this is intentional or not.

Cheers

Ian

 

[merlin]

for the send if i am inputing 1v i seem to get only 80mv out? is this the correct level?
for the return if i input 1v i only get 8mv out?

Send level seems in the right ballpark, but return level is strange. You'd expect unity gain overall...

 

[Spencerleehorton]

So return I would be looking for 80mv as well?

 

[Spencerleehorton]

Built this one today and I think one or both of my LND150s are faulty?
I get some sound through it but it’s a bit intermittent, the harder you play the more that comes through, I’ve got some more LND150s coming so I’ll change them.
What voltage should I expect on drain, gate and source on both transistors?

 

[Spencerleehorton]

Hi All,

wanted to know a bit more about fx loop designs for marshall JTM45/plexi amps.
Before ive bought the metro fx loop but wanted to explore the design or other designs and get my own pcbs printed or i can prototype a single layer version.

the friedman/ceriatone design i have put into LTspice and so far it doesnt seem to do what i thought it would, but the question is what signal levels are at play here?
for the send if i am inputing 1v i seem to get only 80mv out? is this the correct level?
for the return if i input 1v i only get 8mv out?

where as this other design seems to have much more level and adjustment
View attachment 136768


is there a better design for these amps?

is there a better design for the LND150?

Ive used this loop and it sounds amazing , made my own pcb

 

[merlin]

So return I would be looking for 80mv as well?

1V in, 1V out