Single loop ROG splitter blend

[joaocosta88]

Hey there!

I know that this is a simple question, and probably is answered somewhere (trust me, i did search)...
I want to build a ROG splitter blend, but in my use case I only need one fx loop, with the blend pot blending the dry signal from the input, with the return of the fx loop signal (from full dry to full wet).
What type of changes do I need to make to the circuit to accomplish this? Is it enough to "hardwire" the red send to red return? The schematic I'm following it this one: http://www.runoffgroove.com/splitter-blend.html

I know there's a couple of other schematics that only have one fx loop (bblender, buff n blend, paralooper, split n blend), but most of them either don't have the phase inverter, or have extra stuff that I don't need...

Thanks in advance, and I apologize if this was answered in another thread...

[duck_arse]

welcome to the forum.

I know little about split/blends, and I can't even see the image I'm posting, but -


seeing as U1B and U2B are identical stages in series, and seeing as you only need one of them, you could drop the jfet section and replace it with U1B and join the input of U2B to U1A, if you see what I mean.

[antonis]

I can't even see the image I'm posting,

Neither we but I suspect you mean something like below:



edit: U1A output cap value (10μF) could be lower down to 10nF..

[marcelomd]

Hi, and welcome to the forum!
To make a one loop split:
- Remove U2B and associated circuity, including the output 10u capacitor;
- Remove 1M from "red send";
- Connect "red send" to one side of the blend potentiometer.
You'll end with U1B -> 10u capacitor -> blend potentiometer.
You'll also end with a spare opamp stage, U2B. You can use it as a buffer after the blend pot.

[joaocosta88]

Thanks for the answers! I believe all the answers "solved" the problem with the same circuit, which is interesting!
Why am I allowed to drop the jfet from the circuit? why does it make sense to be there when we have two loops, but it is not needed when dealing with only one loop?

Thanks for helping!

[antonis]

Why am I allowed to drop the jfet from the circuit? why does it make sense to be there when we have two loops, but it is not needed when dealing with only one loop?

Due to "unknown" output impedance of Green return..
(U2A configuration is a "phase polarity" switch, in case of two return signals are 180^o out of phase, so it doesn't exhibit U2B high input impedance..)

[joaocosta88]

To be honest, I would be lying if I said that I understood that it will come with time. Thanks for the help!! 

[antonis]

To be honest, I would be lying if I said that I understood that it will come with time. Thanks for the help!! 

It will come more easily.. 
http://www.geofex.com/article_folders/polarity_reverser/polarity_reverser.htm

P.S.
U2B input impedance is 1M (the value of bias resistor)
U2A input impedance is a bit more complicated 'cause you have to consider the parallel combination of 220k//220k//1M equivalent value (about 100k)..
This value might, or might not, be considered "low" - it depends on Green return signal impedance..
Q1 Source follower ensures a high input impedance (1M+4k7) while also ensures a low output one (about 400R or so..)

[PRR]

> why does it make sense to be there when we have two loops, but it is not needed when dealing with only one loop?

Long train of thought.

Two loops can be out of phase. One loop is always in phase with itself.

To fix the out-phase case, we have a phase inverter.

The input of a happy (yet simple and cheap) phase inverter is a heavy load on e-guitar.

The JFET buffers that to an easy load.

[moosapotamus]

What type of changes do I need to make to the circuit to accomplish this? Is it enough to "hardwire" the red send to red return? The schematic I'm following it this one: http://www.runoffgroove.com/splitter-blend.html

Yes, wiring the red send to the red return will work. But, consider using a mono switching jack for each of the sends, and a regular mono jack for each of the returns. Then, you will be able to wire each pair of send/return jacks so the input signal will pass directly through (from send to return) when nothing is plugged in. If you only plug in the green send/return, for example, you will still have clean signal passing through the red send/return, and you will be able to blend between clean and the effect. And, you never know... you might want to try two effects in parallel some time in the future (or, maybe even sooner).

[marcelomd]

Found this on my collection.



I'd still use a buffer of some kind after the blend potentiometer.

[antonis]

@joaocosta88: First of all, identify dry/wet signal phase synch..

It might be more easy to implement a dual op-amp phase splitter before wet effect and then just mix both signal via a pot..
(strongly dependent on wet ouput impedance, of course..)