GGG - Parallelyzer, a few basic questions.

[VPIF]

Hi.

I have been sucking in a lot of the information in this forum lately, and I've really learnt a lot, so a big thank you to all the contributors to this excellent forum!

So -  here I go!

I want to build the "GGG – Parallelyzer" as a mixable parallel effects loop in my amps effects loop (did that make any sense)!?!

Amp input > FX-send > four channel stereo paralellyzer > FX-return > power amp > speaker.

It will be housed in a rack unit, so there should be plenty of space. My skill/knowledge is at a very basic level, when it comes to electronics, and I have only built circuits using preexisting layouts to etch circuit boards, and populated them in accordance to parts-layout graphics, in a "colour by numbers" kind of way.

1. I was thinking of using the "GGG – IC buffer". Will I need eight (or twelve – including the unaffected input and output signal), or is there a simpler solution? Do I need a different kind of buffer, since the signal is already at "preamp level", or should I skip them altogether?
2. I am planning to build two "GGG – mini mixer" with four channels each - thus the possibility of having four stereo loops. Is this a simple and effective way to achieve this? I don't think I really need to be able to control the individual L/R volume of each stereo channel.
3. Phase switcher: As mentioned, I am still at the "colour by numbers" level regarding electronics. In the Parallelyzer-article at GGG there is a reference to an article at GEO. Does anyone know of a layout for this phase-switching circuit? I guess the right thing to do would be to try to design a layout, and post it on the forum for correction, right? Do I need one phase-switcher per output, or would it be adequate with one per stereo-pair?

Sorry for the long post. I will appreciate any help and guidance you can give me. Thanks.

[Skruffyhound]

I think, if I remember correctly, that the phase switch section of the ROG (RunoffGroove) Splitter/Blend is R.G.'s (Geofex) but with component values added http://www.runoffgroove.com/splitter-blend.html That's it, the section with the FET coloured pink in that schem.

In fact, when I made something similar, a four channel splitter/mixer, I read all the articles you are reading now, but in the end decided that ROG's splitter/blend was actually the parallelyser, just with two channels. So I doubled it up and used that.

Kudos if you get this big project done, but there are lots of issues with what you are trying to do. My advice - build something along the same lines but simpler, then come back to it in 6 months, you will know 5 times as much about building in that time (I know I do) and save yourself alot of frustration. On the other hand throwing yourself in at the deep end has it's advantages too

The phase switch is there in case one of the effects in your chain inverts the signal phase, most effects do not do this, some would call it bad design that certain pedals invert. So, one effect out of twenty, on one out of four signal lines inverts and phase cancels part of the output, you use your phase switch. If you have 2 signal lines inverted, same thing, if you have three, God forbid, its easier to phase switch the un-inverted signal chain to be inverted, at least this was my logic, so  2 phase switches per 4 channels.
Good Luck and welcome to the forum
Aston

[ianmgull]

Here is a layout I did for 6 GGG IC Buffers on one PCB. It was designed to be modular so If you want 8 just though another TL072 on there.

http://www.diystompboxes.com/smfforum/index.php?topic=72506.msg587667#msg587667

[ianmgull]

Also, regarding the phase switcher:

You may not even need it. Do you know which effects you are using yet? You'll only need phase reversal if the effect inverts its output relative to the rest of the channels.

[VPIF]

Thanks.

I have seen the Splitter-blend, but I guess I misunderstood it as being a circuit which would allow you to blend two different effects loops in a "crossfade" kind of way - and not with the "clean" signal.

The reason why I want parallel loops with volume controls is to blend in a leslie simulator, because I don't want 100% of the signal "leslied". I will also like to be able to add a discrete modulation effect to one side of the stereo-image (can I say "stereo-image" in English?). I am also thinking of having my two digital delay units in a parallel loop.

You're maybe right about this being a project that would involve a lot of swearing and yelling of profanities, but I think the buffers and mixer will be doable, because of the excellent guides at GGG. The plan was to use separate circuit boards for all the buffers and both mixers, and all phase-switches - but I guess the hard part is to make all of these circuits interact in the desired way, right!?! I'll definitely read the Splitter-blend article more thoroughly, though.

[VPIF]

Thanks for the layout, ianmgull. There's maybe not such a big risk to put all the buffers on one board, as long as I've got a layout. The inside of the rack unit will be a kind of jigsaw puzzle, anyway, where there's some room for trial and error.

I will be using Line6 Rotomachine (leslie sim.), TC electronic D-two (digital delay), Korg SDD-1000 (old 8-bit digital delay) and possibly a Boss chorus applied to one side of the stereo.

The only thing I'm still uncertain of is how the buffers will respond to the FX-loop level (they are designed to be before the amp, right)?

[Skruffyhound]

We are talking about parallel lines of effects here, there are not really any loops, unless you feed something back into an input. I took it very literally and built the Splitter/Blend x 2 in two separate boxes so one can sit on each end of the pedalboard and I can see visually more clearly what lines of effects I have. So if you stick your Leslie-ized signal in one send and the clean signal in another send you can blend with a single pot or you can keep the signals separate and send them to a simple mixer where you have one pot for each channel. Perhaps this is what you are trying to do. Anyway, good luck.