Mfos wave freaker and VC echo on +\-15v

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dummyplugconspiracy
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Mfos wave freaker and VC echo on +\-15v

Post by dummyplugconspiracy »

Hi -

I know most of the Mfos stuff is happy with +\-15v power but the wave freaker documentation doesn’t say much other than it requires a minimum of 12 V. There’s no mention of changing components to accommodate 15, so I guess that means I just build it as designed give it 15 and everything will work. Right? Some of the other modules have specific instructions to either make them work with 15 V or assurances that they will work with 15 V without changing anything. Wave Freaker didn’t seem to have that detail, so I would love it if someone could confirm this for me. I’m also building the VC echo module which does seem to say 15 V is fine with no instructions to change components,. I have both on order and wanted to make sure before I start building. Thanks
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Bodo1967
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Re: Mfos wave freaker and VC echo on +\-15v

Post by Bodo1967 »

dummyplugconspiracy wrote: Thu Jul 14, 2022 11:06 amI know most of the Mfos stuff is happy with +\-15v power but the wave freaker documentation doesn’t say much other than it requires a minimum of 12 V. There’s no mention of changing components to accommodate 15, so I guess that means I just build it as designed give it 15 and everything will work. Right?
Mine works fine on 15 V. The internal biasing is done with zener diodes and voltage dividers (which are fed from the 10 V zener diode) anyway.

However, by all means make sure...
MFOS wrote:With no signal input the biasing on the non-inverting input of U3-A (Tl074) causes it's output to sit at about 5.3 volts.
... there's really 5.3 V there. In my build, the original R16 and R17 values only led to about 4.7 V in the first place, and finally I replaced R16 with a 500 k trim pot that allowed me getting the required 5.3 V.
MFOS wrote:Negative level signals on the inputs of the CD4066 will turn on the parasitic protection diodes and cause havoc (and excessive current drain).
This will (and did) happen with 4.7 instead of 5.3 V. It caused a lot of trouble including a fried analog switch.

There's more info here.

Quotes labeled "MFOS" are from the original Wave Freaker circuit description on musicfromputerspace.com
... why buy it for $100 when you can build it yourself for $150?
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dummyplugconspiracy
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Re: Mfos wave freaker and VC echo on +\-15v

Post by dummyplugconspiracy »

OK interesting. I am buying this parts kit and PCB from Soundtronics who usually does an excellent job addressing these issues before they cause problems. I will take these notes and compare them to what they send me to see if they've already accounted for the issue you mentioned.
THANKS!
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dummyplugconspiracy
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Re: Mfos wave freaker and VC echo on +\-15v

Post by dummyplugconspiracy »

Ok - I finished the vc echo module build. It's not working correctly. Before I go too nuts, I wanted to see if anyone else got tripped up on this. The symptoms are a bit odd. It outputs low noise when no source is connected and when I feed it some tone it just does a repeating volume ramp up that doesn't seem to be affected by adjusting delay time. Slightly distorted too. The strange thing is that the knobs all seem to work. Original signal, echo level, even delay time does that cool pitch artifact when you turn it but it doesn't actually behave like an echo effect. I'm wondering if that mic/line switch is where my problem lies. I triple checked wiring and it all looks right. I even checked it on 12v instead of 15v but no difference. When I crank original level im definitely hearing my input signal loud and clear. I'm getting it on a scope tomorrow night but any advice between now and then would be appreciated. I thought I had this one nailed .....
Thanks!!
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Re: Mfos wave freaker and VC echo on +\-15v

Post by dummyplugconspiracy »

SOLVED. I am a dope. I forgot that Ray didn't put a specific wire termination point on his boards that explicitly says "GROUND". So when I read the wiring diagram, I connected all the pot and jack grounds together, but never tied it back to the PCB! Embarrassing. Once I tied them to one of those ground lugs, everything worked like a champ. Fun module!
THANKS
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