Parallel Loop and Volume Control Pedal

[taniwhatuu]

Hi guys, I am working on a idea. Basically its a parallel Fx loop with a volume controller and blender.

• Input ->
• VolumePedalCircuit ->
• DirectSignalVolumeControlled -> FXLoop Send/Return
• DirectSignalVolumeControlled -> DirectSignal
• Mixer   -> Blend FXLoopReturn with DirectSignalVolumeControlled (here)
• Output

Case study.
I want to retain the pure original send signal but have volume control(via pedal) on the overall output(master)
Unusual phasing or latency when using my amps fx loop in a 4 cable method with digital Fx and the amps loop is in parallel mode. So I set the mode to series. This sounds very different to the original signal even with no fx applied. So make a volume controller with FX loop and mixer for finer tuning.

In my fx loop i have delay, harmonizer etc... All fx in the chain are set to 100% wet

Questions:

• Do I have to add buffers on every point of in/out of the circuit?
  
• Do I add a buffer to prevent the DirectSignalVolumeControlled  signal from creating a feedback loop between the fxLoop Send and Return(where the DirectSignalVolumeControlled signal is sent to the FXLoop send and also to the blender)

[Transmogrifox]

Questions:

• Do I have to add buffers on every point of in/out of the circuit?
  
• Do I add a buffer to prevent the DirectSignalVolumeControlled  signal from creating a feedback loop between the fxLoop Send and Return(where the DirectSignalVolumeControlled signal is sent to the FXLoop send and also to the blender)

#1) No, you can probably make it work ok with only 1 buffer. It might even be ok all passive if your "clean" path is high series impedance compared to your guitar or whatever is driving the input to this thing.
#2) The one place a buffer is highly recommended is on the clean path going into the mixer, so as you have identified, you don't create a passive feedback path around the FX loop.

As a better design practice, I would recommend making it all buffered to reduce unpredictable interactions between FX pedal outputs and your box inputs.  This allows you to present a solid >500k input impedance to everything going into your box, and drive with <1k output impedance from every signal leaving your box.

Also keep in mind that an arbitrary combination of FX pedals will have unpredictable phase and/or latency, so that will always be a factor in mixing clean & wet channels.  It's just part of the blending effect.

[ashcat_lt]

A buffer before the split, on the send, on the return, and then your mix amplifier is the safest bet.  Don't know for sure what you're doing for volume control section, whether it will need a buffer before or after or maybe work as the first buffer.  I do wonder are you sure you want it before the pedals and not after the mix?  Unless the amp's FX send is overloading the pedals, It might be best for S/N to leave it loud until it gets through them.

A quad opamp is not fun to design around when you want to do other things, but it's pretty convenient when all you need is buffers.

[taniwhatuu]

Thanks heaps for the help so far!

I've thrown together something just following what I am reading from a few sources

I decided to dump the volume pedal from the circuit and just dedicate this as a parallel loop thingy.

Regarding where the volume control is placed. If it was placed at the end of the path, it would also cut the tails off any delay/reverb signals hence why i would put it through the front although i'm not quite sure how this could effect the tracking of the harmonizer. Ill have to test that.

I currently have  a boss GT10 as my main fx and connect it via 4CM. I don't use any of the front stuff like a compressor/dist/od or amp modelling but the input of my amp receives the signal via the sendOutput which is buffered.

I could effectively place the volume control in the loop but I am thinking that the volume pedal would need to deal with 2 paths at the same time?

This is what I have put together so far? I haven't set any values yet. To be honest I don't actually know if this looks right or not?

[taniwhatuu]

UUgh! upon further research this is almost the same as the (AMZ Paralyzer) http://jmkpcbs.com/product/paralyzer/ where S-1T/R-1T  would be the direct signal and S-2T/R-2T  would be the loop from the effects returning only one channel though?

So in my case could I use this and add another R-3T for the right channel?