Parallel effects loop for Marshall style amps

[paulster]

Larry

On the version of the schematic that includes the bypass switch the second half of the switch at V3b effectively sits at B+ potential because it is before the 0.022 going to the PI. If you were to swap the cap and the resistor round and then parallel the switch with the resistor so it has the DC offset removed would it have any tonal effect?

Since I'd like to use a signal relay which isn't rated for this kind of voltage, keeping it closer to ground potential would be useful.

Cheers
Paul

[novosibir]

On the version of the schematic that includes the bypass switch the second half of the switch at V3b effectively sits at B+ potential because it is before the 0.022 going to the PI. If you were to swap the cap and the resistor round and then parallel the switch with the resistor so it has the DC offset removed would it have any tonal effect?

Since I'd like to use a signal relay which isn't rated for this kind of voltage, keeping it closer to ground potential would be useful.

Paul, there wouldn't be a tonal difference, but a BIG BANG while switching due to potential differences.

So no way - use other relays!

Larry

[paulster]

There wouldn't be a tonal difference, but a BIG BANG while switching due to potential differences.

It's amazing how you miss the blindingly obvious sometimes! Thanks.

[Capi]

Larry, I installed your parallel effects loops in the single-end amp posted time ago and works really well, transparent and no sound colouration.

Now I'm thinking of installing the loop in an amp ( DIY marshall based amp ) with this specs:

- Two channels, three modes ( clean/crunch, lead )
- Two Tone Stacks, one for CH1 ( clean/crunch ), other for CH2 ( lead )
- Three MV pots ( clean, crunch and lead )
- EL34 50W class AB power amp with long tailed pair phase inverter

My idea is to have the actual master volumes as individual volumes for each channel, insert the effects loops and add the Master after recovery stage.

How can I do this ? Is there a better way to do ?

Thanks!

[novosibir]

Do you really need a master for the clean sound?

What about, to have preamp masters for crunch & lead and none for clean before the loop section - and an additional overall master after the recovery stage just before the PI?

That's the way I'd do it. The overall master, to control the whole amp w/o influencing the loop levels.

Larry

[Capi]

This is tha actual arrange for my individual MV:



The clean channel is derived from the crunch circuit and share the TS ( cathode driven ). Something similar to Soldano SLO but with different voicing adjust to my taste.

Regards

[Capi]

Larry, I want to keep the preamp master for clean mode. So to add your loop, I have to cut the junction between the two optocouplers and C3. And add the send pot after the two optocouplers, I'm right ?

Then i have to add the overall master after the recovery stage.

Thanks!

[novosibir]

Correct, the loop has to go just before C3

Larry

[hammeron]

Hello, anybody here that have put this in a Sovtek Tube Midget 50-H amp ?

Niklas

[Evz]

sorry, if i did not get to read though the whole thread yet, but is there any danger in useing 330p instead of 220p? (this was the only value availble to me) please let me know if i should make any other alternations if i use the 330p.

Thank you!

[novosibir]

A 330p is too sharp, too brittle.
You don't have two 100p's, which you can solder in parallel?
I'd rather leave the cap off entirely instead of this value.

Larry

[Evz]

ill try some other stores, another question, is it ok to use 22u/450 polorized radial caps instead of one polorized axial between the power resistor and ground, and then using the same one on the Vb cathode?

[novosibir]

... is it ok to use 22u/450 polorized radial caps instead of one polorized axial between the power resistor and ground

Yes!

... and then using the same one on the Vb cathode?

No! High voltage electrolytics do have a too high ESR for cathode purpose.

Larry

[Evz]

would you be kind enough to point me in the right direction for the 22uf cap? like a poly film? or what should i get for that one?

[novosibir]

would you be kind enough to point me in the right direction for the 22uf cap? like a poly film? or what should i get for that one?

A low volt electrolytic cap - i.e. 16V, 35V, 63V or 100V

Larry