Parallel effects loop for Marshall style amps

[emartine]

Hello, Larry. I just finished building the loop! Its seems that its not working properly.
The things are these:
1. When I disable the loop with the DPDT switch, the return pot still acts like a volume..
This ain't right, or is it?

2. The send pot is not changing things very much..

3. I cannot put the return control very high, otherwise it squeals a lot..
I think this might be is how it works. If I decrease the output volume of my reverb then I can increase a little more the return.

4. The series loop option has less gain than parallel option..

Any ideas?
Thanks!!

[novosibir]

Hello, Larry. I just finished building the loop! Its seems that its not working properly.
The things are these:
1. When I disable the loop with the DPDT switch, the return pot still acts like a volume..
This ain't right, or is it?

No, this isn't right!

2. The send pot is not changing things very much..

Then you do have a bug in your circuit.

3. I cannot put the return control very high, otherwise it squeals a lot..
I think this might be is how it works. If I decrease the output volume of my reverb then I can increase a little more the return.

Oscillation due to improper lead dress.

4. The series loop option has less gain than parallel option..

Again any bug in your circuit.

Any ideas?

How can I have ideas w/o your amp on my bench and w/o seeing, what you've done at all?
Rip all out and build it up once again, but this time properly!
Or - if you're not very experienced with tube amps - have someone with experience & knowledge, doing it for you.

Thanks!!

Anytime!

Larry

[emartine]

Hello, Larry. I just finished building the loop! Its seems that its not working properly.
The things are these:
1. When I disable the loop with the DPDT switch, the return pot still acts like a volume..
This ain't right, or is it?

No, this isn't right!

2. The send pot is not changing things very much..

Then you do have a bug in your circuit.

3. I cannot put the return control very high, otherwise it squeals a lot..
I think this might be is how it works. If I decrease the output volume of my reverb then I can increase a little more the return.

Oscillation due to improper lead dress.

4. The series loop option has less gain than parallel option..

Again any bug in your circuit.

Any ideas?

How can I have ideas w/o your amp on my bench and w/o seeing, what you've done at all?
Rip all out and build it up once again, but this time properly!
Or - if you're not very experienced with tube amps - have someone with experience & knowledge, doing it for you.

Thanks!!

Anytime!

Larry

Well. You had some ideas!!
I would check the board, but Im pretty sure that is OK. There might be something else, may be in the switches..
Ill check that again..
Thanks

[emartine]

Hello, Larry. I just finished building the loop! Its seems that its not working properly.
The things are these:
1. When I disable the loop with the DPDT switch, the return pot still acts like a volume..
This ain't right, or is it?

No, this isn't right!

2. The send pot is not changing things very much..

Then you do have a bug in your circuit.

3. I cannot put the return control very high, otherwise it squeals a lot..
I think this might be is how it works. If I decrease the output volume of my reverb then I can increase a little more the return.

Oscillation due to improper lead dress.

4. The series loop option has less gain than parallel option..

Again any bug in your circuit.

Any ideas?

How can I have ideas w/o your amp on my bench and w/o seeing, what you've done at all?
Rip all out and build it up once again, but this time properly!
Or - if you're not very experienced with tube amps - have someone with experience & knowledge, doing it for you.

Thanks!!

Anytime!

Larry

Well. You had some ideas!!
I would check the board, but Im pretty sure that is OK. There might be something else, may be in the switches..
Ill check that again..
Thanks

Larry
Can I send you throw PM a link to the layout I follow with the switches added?
May be you can see easily if I did something wrong..

[novosibir]

Better send it to my email.
Klick on my username, then on left on the link "email"

Larry

[mathd]

Please can you send me the schematic for this effects loop if i qualify

[novosibir]

Read the 1-st post of this topic to see, what's required!

Larry

[emartine]

Better send it to my email.
Klick on my username, then on left on the link "email"

Larry

Great loop, Larry!!
I finally was able to test it for a while. I love how quiet it is!

I have a couple of questions about it:

Is possible to mod it to have it as a series loop when the send pot is on 10? and bypassed when send pot is on 0 ?
Can I get rid of the quiet sound when in series mode, pots cranked, and no guitar cord
jumpering Send and Return jacks??

[novosibir]

Is possible to mod it to have it as a series loop when the send pot is on 10? and bypassed when send pot is on 0 ?

... and that cool beer is coming out of the unused speaker jack, when the Return pot is set at 3

The short answer: No!

Can I get rid of the quiet sound when in series mode, pots cranked, and no guitar cord
jumpering Send and Return jacks??

You can hard wire the Send jack's tip to the Return jack's switch contact of the tip, that's all.
But when you play w/o effects in parallel mode, you always should turn the Return level to zero.

Larry

[Just Mike]

Can somebody please explain to me how to wire this into a master volume JCM-800? I've read and reread every post in this thread and I can't get it into my head. I have Larry's diagram and schematic but I still don't get it. I think it's the master volume that's messing me up.
Let me explain how I have it wired and maybe somebody can tell me where I'm wrong.
On the layout thet Rockstah did, I have a wire coming off of the .0022u cap that is part of the phase inverter (this is a new cap that I added, right?) going to the high side of the master volume. This is also where a wire from the wiper of the treble pot ties in. Is this right?
I'm getting good level to my effects unit, but nothing coming back and the overall volume of the amp is lower than without the circuit. Tone seems to be the same though.
I need somebody to walk me thru this...Thanks.

[Just Mike]

OK, I'll walk myself thru it.

1. On a master volume 2204 style amp, one must remove the jumper between the treble pot wiper and the master volume feed. The return from the output (pin 6 of the tube) goes to a .022u coupling cap that is not shown on the diagram and then to the input of the master volume.
2. Make sure none of your tube pins are shorted to ground. And I'll add here; see Larry's signature.

[nasoftz]

hello forum!
I'm very sorry 'couse I didn't give usefull feedback to this thread...! I 'm wrong and I must admit my mistakes

So after lot's of time spent playing on my 2203 that has this loop installed since 2008 and for sure, after lot's of

gigs without my amp, I was able to compare different stock and diy serial/parallel loops installed on Marshall-like tube

amps with Larry's "monster" loop. I 'm pretty sure that ..no way .. this is the best loop I ever use!
If you take a look on "bullet in your head" recorded live in one of my gigs posted on my youtube channel (called like my

nick) you can hear the loop installed on my amp playing at really high volume. I installed it after MV : no hum no

squeal no noise at all , it is amazing!

To everyone:
Now I'm going to install it on my peavey classic 20 amp ... but I would like to build it in a more compact design than

one used on my JCM800... take a look to the pic...



problem is : I'm not pretty sure that 63V voltage rating on 22n caps will be enought or I absolutely need to swap with

bigger ones, couse for JCM800 I just used same rating of the 470n... suggestions are really appreciated XD

To Larry:
2 days ago surfing on the internet I found a copy of your schematic uploaded by "someone".. like I know, when I got it

from you long time ago, you never gave the permission to make it public... Please contact me is you need to know that

adress...

All the best!
Maurizio

[novosibir]

problem is : I'm not pretty sure that 63V voltage rating on 22n caps will be enought or I absolutely need to swap with bigger ones, couse for JCM800 I just used same rating of the 470n... suggestions are really appreciated XD

The 22n's after the Send Level and before the grid of the recovery stage can be 63V, there's no high voltage.
The 470n on the CF's cathode must be 100V min.
Only for the 22n at the plate of the recovery stage must be 400V

Larry

[nasoftz]

thanks Larry, so voltage rating of onboard caps seems to be ok! ^^
I 'm going to wire that 22n/450v outside compact pcb and directly in front of PI..

[nasoftz]

Larry,
FXloop is now installed into my Classic 20 I decided to wire it directly after the master, running throught master wiper that I have disconnected from the board and wired to the send fxloop input, loop return is in front of the PI, connected to the 22n/400v coupling cap.
Problem is that I got no sound from the preamp: a very thin and too far signal is audible only at "high" volume setting.
With everything disconnected front the loop,when I turning the send pot from "10" to "2" than I get no sound and no noise, when I reach the "2" position I start to get a kick in my ass with big ground pops (and the amp start to tell me that I did a mistake XD) , so problem is starting from "2" to 0" of the send pot, if I leave the send pot a those settings, amp start to hum like hell, if you turn up to "3" than problem is gone but still no sound.
However when I connect the Guitar to the return of the fxloop, guitar sound pretty well,so fx return is working,,
I just think that problem is on dry signal running in paralell throught the loop but I rechecked my circuit comparing it to the the diagram and everything seems to be pretty well connected.