Yamaha GX-1 filterstructure

[Lindh]

Hi!

 

I'm struggling to find out in wich order the filters are placed in the GX-1. I've always heard that the LP comes first, before the HP. Then I saw this photo, where the HP seems to be first:

 

http://www.sequentix.com/gx1/ToneBoard1.jpg

 

Does anyone know the real answer?

[Plink Floyd]

The hpf does indeed appear to be first on that machine. Maybe there isn't really a best, or 'correct' order. No doubt if they were reversed is would sound different. But, I don't have a modular to go try it.

[mate_stubb]

It's not unusual for the HPF to be first (Jupiter-8, for instance). Your tone board photo appears to give the definitive answer.

 

If you haven't read them, the classic Gordon Reid GX-1 articles are highly entertaining:

 

http://www.soundonsound.com/sos/feb00/articles/yamahagx1.htm

http://www.soundonsound.com/sos/mar00/articles/yamahagx1.htm

[Lindh]

Thank's! Yes, those articles are very interesting!

 

But it doesn't make sense. Everywhere I've heard that the filterorder of the GX-1 is the opposite to the CS-80.

 

 

And now this tone board photo...

 

By the way, I'm building the GX-1 in a modular system. That's why I need to know

[mate_stubb]

Thank's! Yes, those articles are very interesting! But it doesn't make sense. Everywhere I've heard that the filterorder of the GX-1 is the opposite to the CS-80. And now this tone board photo... By the way, I'm building the GX-1 in a modular system. That's why I need to know

 

Check out Scott Rider's webpage for all kinds of block and circuit diagrams. He is a CS-80 stud, and was the guy who reverse engineered the potted submodules to produce the MOTM GX filters. Contact him with your GX questions.

 

Meanwhile start here:

http://www.oldcrows.net/~oldcrow/synth/yamaha/cs80/index.html

[uvacom-rotatt]

The hpf does indeed appear to be first on that machine. Maybe there isn't really a best, or 'correct' order. No doubt if they were reversed is would sound different. But, I don't have a modular to go try it.

 

If the filters were completely LTI it actually wouldn't matter in the slightest. We know that analog filters aren't entirely linear (although they should be basically time invariant under normal circumstances), but essentially unless one is driving them very hard there will probably not be any audible difference.

[Moogasaur]

I mean no disrespect to the designers at all, but the times that I've heard the MOTM GX-1 filter, it's sounded nothing like the GX-1 that I've heard on records. It's cool in it's own way (I've patched it before on someone else's MOTM modular), but why does it sound so unlike the tonalities from a GX-1? Or am I missing something?

[Plink Floyd]

If the filters were completely LTI it actually wouldn't matter in the slightest. We know that analog filters aren't entirely linear (although they should be basically time invariant under normal circumstances), but essentially unless one is driving them very hard there will probably not be any audible difference.

Fair enough. I guess the end result's no different than a bandpass filter?

[suitandtieguy]

taking a filter out of its context will not give you the rest of it.

 

i'm sure Scott did a great job on the filter, but it's like the MOTM-490. that didn't make my synth sound like a Moog either. however, when i put my CP3 clone in as the filter mixer, the game changed completely.

[Moogasaur]

 

taking a filter out of its context will not give you the rest of it. i'm sure Scott did a great job on the filter, but it's like the MOTM-490. that didn't make my synth sound like a Moog either. however, when i put my CP3 clone in as the filter mixer, the game changed completely.

 

 

I understand that a filter won't reproduce all aspects of a synth, but I do have a number of filters (MOTM-420, 490, 440, APR clone, EMS clone, etc, etc), and they all seem to impart at least a bit of the original synth's sound.

 

Are you using your CP filter mixer to lower the input levels to the MOTM GX-1 filter? I wonder if that's the issue?