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Hi folks, Not been here for a long time... but I thought I'd make a quick post. I've been playing the 80's a lot recently... and have gotten into altering the Brilliance fader during play. It's quite tricky to get a free hand in sync so I thought I'd look at the "wah" function on the expression pedal. First thing that struck me was that along with "wah" you also must have volume. Not what I'd like. I'd like the volume to be set and just open and close the "Brillinace". Second thing was that I thought I might be able to "modify" to get just "wah"... but looking at the schematic I cannot fathom how the "wah" function works. It doesn't seem to be a direct replacement for the Brilliance lever...? Could anyone please shed some light on it please...? So, apart from disconnecting the Brill pot's wiper and putting it to a foot pedal sweeping between +/-15 volts - which was an idea I had - can anyone think of a quick way of getting that function...? Cheers, Tom |
开云体育Hi Tom! ? Quick note since I’m at work.? I’m looking at the big, fold-out schematic at the PRA EXP WAH Circuit all the way at the top right.? The foot pedal voltage comes in on EI(52) and buffered by IC3. The output goes through LEDs PH1 and PH2 that shine on internal photocells for the volume control.? It also goes to PH3, over to the left, to control the wah (nothing to do with the brilliance or VCFs) The catch is that, since they’re in series, you can control wah without volume in the LED/photocell modules.?? You could just use a DSDP switch to bypass the photocell pins on PH1 and PH2 so the pedal doesn’t control the volume.? It might mess with the level so it could need a couple of resistors in series with the bypass path so the volume is the same. ? David On Apr 20, 2017, at 8:40 AM, noddyspuncture@... [yamahacs80] <yamahacs80@...> wrote:
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On Apr 20, 2017, at 11:58 AM, noddyspuncture@... [yamahacs80] <yamahacs80@...> wrote:
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Another Question about the exp wha circuit: none of you have audio or video where you can hear this effect? On my cs 80, with the pedal at full volume (full down) , you will hear the sound of the bandpass filter. He is normal? See my cs80 on this video, I play the pedal up & down vithout touch the keyboard:? Thanks Tommaso
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Hi Tom,
I just posted a redrawn diagram to get a better overview of the effects order. Since, for some reason, the resolution is reduced after the file transfer, I put a copy here too : What you're trying to do was originally planned by Yamaha. It is visible on page 66 of the Service Manual, where the WAH alone is drawn but was carefully struck out. On the next diagram, I have reconstructed what the initial design might have been : Note that this only an hypothesis and I do not pretend that it works. Anyway, that gives the idea. The reason why Yamaha chose not to do it is not clear. Perhaps the PRA board was already full ? As for controlling the brilliance, that would require an other design. Joachim |
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I thought about your project for a while and here is how I would do it, if I had to :
? This is not a full design since the resistor values need to be computed (with a ratio 1/3 between FH and FL to generate the CS-80's characteristic filter opening) and the voltage/current should be checked so that they comply with the existing circuitry.Hope this helps, Joachim |
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Again, thanks - I'll have a good look at your diagram...but I was thinking along the lines of actually over-patching the brilliance control (wire from the wiper) to a pot in a 'custom' pedal - along with +/-15 & ground.
I think it would be much simpler and would behave in the exact same way...? Cheers, Tom |
开云体育If you’re going to do a +/-15v pedal, why not just plug it into the sub-osc external input jack, turn up the ext level knob next to the jack, and set the Sub Osc to EXT and Sub Osc VCF to max and Sub Osc VCO and VCA off. ?No circuit mods! ?I’m just not sure how much range you’ll get. ?David
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