Request for SS effects loop schematic with series/parallel switch

[smackoj]

Hello fellow enthusiasts; I have looked for quite a long time and haven't found what I am looking for (see title). I want to learn how to add an effects loop send and return to a SS amp. I know the basics and have looked at the group of designs in the 'tube' section but converting to SS would be risky for my knowledge level. I realize there may be other forums that would be more slanted towards SS type gear, but I always like to ask here because of the high level of expertise.   

Muchas gracias amigos

[shooter]

scratch your head on this for awhile;

you got a breadboard and sand pieces?

[shooter]

here's my crude hack job.  I'd breadboard up the IC, stick a signal in and see what comes out, if the in and out look close, jack it into a pedal, jack the pedal out and maybe use headphones at the output of the IC.

[smackoj]

Hello and thanks; I see the similarity with the tube examples in the Archives and the Fender Chorus schemo, using half of the TL072 for 'send' and the other half for 'return' power. I'm not sure why the example Shooter supplied looks like both sides of the Opamp are driving the send. Maybe someone could explain the difference in the use of the Opamp for me? Or tell me if I am seeing things wrong?

thanks amigos

[shooter]

The return side "assumes" whatever is coming back is of sufficient amplitude to drive the next stage. If it isn't, you'll probably have to add another chip.  Also, look at the spec'd voltages on the original, that will probably give you a good starting point

[2deaf]

I want to learn how to add an effects loop send and return to a SS amp.

Any particular SS amp?  Do you have a schematic?

[smackoj]

I have a 1979 Premier P50R ss amp. It is not 50 watts, more like 8 or 10 watts. This is the same Premier Co. that made lots of early tube amps. Sorry I could not find a schematic.

thanks

[2deaf]

Probably a discrete device preamp with a single ended supply.  An IC opamp would not be the preferable device for an effect loop under these circumstances.

[shooter]

IC opamp would not be the preferable

probably true, the TL072 can be operated single PS, I believe it's also used in single supply pedals, but you can always breadboard up a NPN and experiment.

[2deaf]

. . . you can always breadboard up a NPN and experiment.

The BJT's are already operating in the low impedance realm, so you're already half way there for an effects send.  Probably use an emitter-follower with a voltage divider for the send and copy whatever they did at the input for the recovery.

[smackoj]

hi; does anyone dare to venture a drawing - schematic so I can visually see what you are saying?  Thanks for the good input guys.
jack

[shooter]

do you have a scope?

how bout one of these;

[smackoj]

Hi Shooter; No, I don't have a scope. So the yellow wire to a 10k is send and the orange wire to a 10k is the return? Sure looks simple enuf which is always a plus. 

[shooter]

Sure looks simple enuf which is always a plus

You might notget the desired results if you build the 555 circuit
Pick up a breadboard though, wire up Fenders TLo72 and listen, you might like it, you might give up, but hopefully you have fun

[smackoj]

hi shooter; I have a breadboard and a couple TL072 op amps. Am I correct about the yel and org wires being send and return?
thanks

[shooter]

about the yel and org wires

If you're talking about the breadboard pic, that has NOTHING to do with send/return, that was just a pic grab of a "typical" breadboard that you will need to mock-up your send return.

[2deaf]

Here is an idea for an Op Amp FX loop.  I haven't tried it, so it's up to you to see if it works.  30V maximum on the B+.

[smackoj]

That "op amp fx loop" looks good enuf to try. It makes sense to use one-half the IC for each side of the loop. I know that is the format Fender uses as seen up close to the top of this thread.  gracias

[smackoj]

I found this suggestion as a SS booster and FX loop over at La Revolution Deux which is hosted by Fred Briggs. I have built a few of his designs and really liked them. Here is his FX loop design: