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Questions about 4x Gate Delay and Quad AD
MUFF WIGGLER Forum Index -> Mattson Mini Modular  
Author Questions about 4x Gate Delay and Quad AD
pugix
I'm about ready to buy one of the DIY boards for the Gate Delay and also the Quad EG. Some questions first.

The Gate Delay outputs are +15V (or close), right? Just asking. All of the gate outputs in my system are about +5V.

The Quad EG expects a +5V gate, which is right at the level of gates from my other modules. (All of my modules with gate inputs have thresholds somewhere in the range of 1V to 3V.) Could I have problems gating the Quad EG from my other modules?

Can I trigger the EG with a +/-5V square wave? Any issue with negative voltage going in?

Does the EG require a sharply rising input, or does it have a Schmidt trigger?

How hard would it be to modify the Quad EG to lower the gate threshold, or to lower the output level?

Now, about the Gate Delay logic. When does an output go low? I understand that an output will not trigger if the delay is longer than the width of the incoming gate. But how is the output gate end related to the input gate? If the input gate goes low, do all the outputs that have fired also immediately go low, too? In other words, is it just a delay on the start of the gate, but not the end? Or is it a pulse stretcher?

That's a lot of questions! Sorry. Time for more coffee, George. Coffee Addiction FTW

Thanks,
mmm
pugix wrote:

The Gate Delay outputs are +15V (or close), right? Just asking. All of the gate outputs in my system are about +5V.


Yes, I did that so they could be used with any other system regardless of the gate level they are designed to receive. Hopefully, the other guys built their stuff so that it doesn't really matter if the gate voltage is higher, as long as it gets to the threshold. If I'm wrong, please let me know.

Quote:
The Quad EG expects a +5V gate, which is right at the level of gates from my other modules. (All of my modules with gate inputs have thresholds somewhere in the range of 1V to 3V.) Could I have problems gating the Quad EG from my other modules?


Actually, it triggers right around 7V. Yes, you could, unless I change the voltage divider values on the inputs 8_)

Quote:
Can I trigger the EG with a +/-5V square wave? Any issue with negative voltage going in?


See previous statement. Negative voltages are not an issue, the inputs are diode clamped to ground on negative excursions.

(they're also normalled to each other so that a trigger input affects all the subsequent channels until you specifically plug a different trigger into a subsequent channel)

Quote:
Does the EG require a sharply rising input, or does it have a Schmidt trigger?


Neither. Once you hit the trigger level, it latches and self-completes the attack cycle. I guess thats like a mega-schmitt trigger.

Quote:
How hard would it be to modify the Quad EG to lower the gate threshold, or to lower the output level?


Different values on the input voltage divider and, do you want to lower the output levels? They're 0-5V output. You could always toss some pots on the outputs and manually attenuate them if you need them lower.

Quote:
Now, about the Gate Delay logic. When does an output go low?


When the input gate/trigger voltage is removed or, goes low.

Quote:
I understand that an output will not trigger if the delay is longer than the width of the incoming gate. But how is the output gate end related to the input gate? If the input gate goes low, do all the outputs that have fired also immediately go low, too? In other words, is it just a delay on the start of the gate, but not the end? Or is it a pulse stretcher?


Short answer:
A delay on the initiation of a gate until the gate is removed.
With all 4 delays at minimum, it is also a gate multiple applause

Long answer:
It's just 4 channels of RC time constants that charge while the gate input is positive. The input actually goes to a comparator and it fires and starts the delay sequence on all four channels when the input is above the voltage level set by the threshold control. The Comparator voltage charges all 4 channel caps through the panel pots. The cap output on each channel goes to a comparator for that channel. There is a trim pot on the board that determines at what voltage the caps have to reach before providing a positive channel output.

So, to follow through, Once the gate input (or voltage input) is below the comparator threshold level, it drops to 0V and any channel that hasn't charged enough to trigger it's output doesn't complete.

The output gates all remain high (about 13V) until they're dropped when the gate goes low. If you don't want it to remain high and use it as a timed trigger source, put a 0.01uF cap in series with the output. That will cause a short-term trigger event each time they go active. Having a switch to short out the cap can allow you to select either a trigger out (cap in line) or a continuous out (cap shorted.)

Quote:
That's a lot of questions! Sorry. Time for more coffee, George. Coffee Addiction FTW



That's a lot of answer. Ihope I covered all of it. I tend to ramble. seriously, i just don't get it
Coffee sounds wonderful... applause


G
pugix
George, thanks for all the answers, and the private messages.

I've ordered both DIY boards! nanners It's peanut butter jelly time! nanners

It will be great to have 4 envelope generators in a 1U wide 5U panel. I'm going to mount it next to the VC Mixer. I can drive it from the Mattson 4x Gate module, or from my dual CGS slope detector, among others.

thumbs up
pugix
I need the list of pot values for these two modules. Seems to me there was a PDF wiring diagram for each DIY module somewhere on the Mattson wiki, but I can't find it. I know the parts list will accompany the modules when they arrive, but I was hoping to get a jump on ordering the pots.
mmm
pugix wrote:
I need the list of pot values for these two modules. Seems to me there was a PDF wiring diagram for each DIY module somewhere on the Mattson wiki, but I can't find it. I know the parts list will accompany the modules when they arrive, but I was hoping to get a jump on ordering the pots.


Hi Richard,

Internet is spotty where I am.

http://mmm.sevcom.com/wiki/index.php/4x_Gate_Delay_Board

http://mmm.sevcom.com/wiki/index.php/QuAD_/ASR_Envelope_Generator_Boar d

That should help you out.

BTW PM'd you with info

G
pugix
Thanks George. Just what I needed.
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