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 FatMan: Issue with VCF AR Mode 
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Joined: Sun Jan 30, 2011 10:36 pm
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Post FatMan: Issue with VCF AR Mode
My FatMan (built in 1996) has an issue with the "AR" VCF envelope mode. A stock FatMan has two modes, "AR" and "ASR". Mine has the "repeating AR" mod, which adds a third mode to allow the VCF's envelope generator to act as a pseudo-LFO. My FatMan behaves as expected in the "repeating AR" and "ASR" positions. However, in "AR" mode the envelope generator's Release cycle has to complete before the envelope can be retriggered. That doesn't seem right.

For example, let's say that the VCF Attack is set to minimum and Release is set to five seconds. If I play a note I get the expected envelope, but if I play a second note within five seconds the EG is not retriggered. The first note I play after the initial five seconds is up will once again retrigger the EG.

Is this how a stock FatMan behaves? If not, is this behavior something that can be corrected? Thanks!


Mon Feb 07, 2011 11:27 pm
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Joined: Sun Nov 09, 2008 2:49 pm
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Post FatMan VCF A(S)R
I'll have to spend some time with this to see if I can work out a solution, but it looks like it is a toggling action related to the modification. Maybe just a capacitor and resistor to make the uC i2 line get a pulse instead of a toggle is all that's needed??? I'll let you know when I've had the chance to try it out.

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Tue Feb 08, 2011 3:41 pm
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Post Re: FatMan: Issue with VCF AR Mode
Thanks in advance, Scott. This issue isn't critical. I'm sure you're a busy guy with lots of important things to work on. :)

Can I assume that what I described is NOT how a stock FatMan behaves?

You did the mod for me back in 1996. Let me know if I can provide more information.

Thanks!


Thu Feb 10, 2011 8:24 pm
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Post Re: FatMan: Issue with VCF AR Mode
One more thing...I'm not an electronics expert, but would it be helpful if I compared my FatMan against the documentation of the "repeating AR" mod?

Thanks.


Thu Feb 10, 2011 9:38 pm
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Post Re: FatMan: Issue with VCF AR Mode
No, it doesn't occur unless the modification is in place which toggles the i2 line to the uC instead of pulsing it. I guess I never noticed this before but I also tend to have Velocity advanced which hides the condition.

I don't think it will be any help comparing what you have with the Repeating AR schematic.

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Fri Feb 11, 2011 5:58 pm
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Post Re: FatMan: Issue with VCF AR Mode
Scott: Please let me know if at some point there's a fix for this.

As always, thanks for your help.


Mon Feb 14, 2011 6:53 pm
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