Mattson VCA questions

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pugix
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Mattson VCA questions

Post by pugix » Sat May 08, 2010 12:09 pm

First to note, the VCA link the MMM Store is broken. It goes to Emergency Kits.

http://mmm.sevcom.com/wiki/index.php?ti ... _Amplifier

I found the original from the history:

http://mmm.sevcom.com/wiki/index.php?ti ... &oldid=674

Now to my questions. George, why did you choose to have an overall output level pot instead of an attenuator on the master CV input? Is it because the amplifier will go above unity gain when CV in is at +5V and the Manual Level pot is turned up?

I was wondering if when I make my panel I swap the pots and put a master CV input attenuator and not have the output level pot. See any problems with this?

BTW, I'm cooking up a 5U x 1U panel that will house one each of the Mattson Envelope Generator and VCA.
Richard
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"Everything in our world is actually always modulated by everything else." - Peter B

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Re: Mattson VCA questions

Post by mmm » Sat May 08, 2010 1:04 pm

pugix wrote:First to note, the VCA link the MMM Store is broken. It goes to Emergency Kits.

http://mmm.sevcom.com/wiki/index.php?ti ... _Amplifier

I found the original from the history:

http://mmm.sevcom.com/wiki/index.php?ti ... &oldid=674
It's not broken. We get people Spamming the site and uploading their own crap. We delete and ban those users and I send an invoice to the linked companies for the advertising time. That really pisses them off but, who gives a sh--. :guinness:
Thanks for catching that, Richard. All fixed.
Now to my questions. George, why did you choose to have an overall output level pot instead of an attenuator on the master CV input? Is it because the amplifier will go above unity gain when CV in is at +5V and the Manual Level pot is turned up?
No, that's the way my brain works. :woah:

I think that goes back to my old EML days where the VCA's "leaked" and I always wanted to turn them down when I wasn't actually playing something.

Old habits and all....

The master CV input and the Manual level are summed together going into the VC input buffer. The manual level just applies 0-5VDC to the VC buffer to open it up in case people want to just let it drone. I found some patches where having a snappy EG in the master CV input and a hair bit of droning bleedthrough turned out really cool. But, that's me.



They actually don't go above unity. I actually think it's down a bit. An anomoly I've rectified by turning the mix channel up on my main mixer. :despair:
I was wondering if when I make my panel I swap the pots and put a master CV input attenuator and not have the output level pot. See any problems with this?
Not at all. If that's the way you want to do it, go ahead. I just provide a means, You guys provide all of the creativity :bananaguitar:
My I/O for the DIY boards are merely suggestive...for the most part.
BTW, I'm cooking up a 5U x 1U panel that will house one each of the Mattson Envelope Generator and VCA.
Cool, a Two-fer. Post pix!!!

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Post by pugix » Sat May 08, 2010 3:46 pm

Thanks, George!
They actually don't go above unity. I actually think it's down a bit.
So the sum of the Manual Level pot and the Master CV input is somehow clamped at +5V, so that the gain can't exceed 1.0 (or a little less). And if the Manual Level pot is turned all the way up, then the Master CV input basically would have no effect? Would a negative input on the Master CV input in that situation reduce the gain?
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Post by mmm » Sat May 08, 2010 4:36 pm

pugix wrote:Thanks, George!
They actually don't go above unity. I actually think it's down a bit.
So the sum of the Manual Level pot and the Master CV input is somehow clamped at +5V, so that the gain can't exceed 1.0 (or a little less). And if the Manual Level pot is turned all the way up, then the Master CV input basically would have no effect? Would a negative input on the Master CV input in that situation reduce the gain?
No, they're not clamped at +5v. You could put 6 or 7V on it and get more gain. If the master CV input transitions above the max manual voltage applied internally, it will bump the output level.

I don't know about the negative input scene. Technically, If the manual offset is up all the way and you apply an inverted envelope to the master CV input, It should work backward. I've never tried it.

Besides the 100K impedance resistors acting as a summation network, they feed into pin 3 of U1 which is negatively biased slightly less than ground with a 100K to ground and a 4.7M resistor from there to -V.

After the input buffer, the signal is diode clamped/ half wave rectified to prevent negative values on the base of the transistor driving the current mirror and entire modulation network. (Q1)

The raw VCA output goes to the top of the Output level pot. The wiper feeds that signal to an output buffer which splits the output in two identical output feeds. Thus, the dual mono outs.

So, short out CN2B pin 1 and 2 to loop the output back to the output buffer directly and bypass the output level pot.

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Post by pugix » Sun May 09, 2010 3:29 pm

Thanks for the plentiful information, George. I've ordered two each of the EG and VCA boards. And I finished my FPD panel design. I always wait for the boards before I order the FPD, just to make sure. The FPD panels are about $65 USD each. :cry: But I'll fit all four modules in two 1U panels (1 EG and 1 VCA per panel - all the panel bits fit in 16 spaces on a grid). The EG out will be normal-lug connected to the VCA master CV input jack. For functionality, this beats the Oakley ADSR/VCA hands down with 8 pots, 2 switches, 6 jacks vs. 4 big knobs, 1 switch (range) and 4 jacks on the Oakley, and a completely separate VCA. I plan to add an LED to indicate the EG output level too. A tiny LED can fit in between stuff.
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Post by mmm » Sun May 09, 2010 5:03 pm

pugix wrote:Thanks for the plentiful information, George. I've ordered two each of the EG and VCA boards. And I finished my FPD panel design. I always wait for the boards before I order the FPD, just to make sure. The FPD panels are about $65 USD each. :cry: But I'll fit all four modules in two 1U panels (1 EG and 1 VCA per panel - all the panel bits fit in 16 spaces on a grid). The EG out will be normal-lug connected to the VCA master CV input jack. For functionality, this beats the Oakley ADSR/VCA hands down with 8 pots, 2 switches, 6 jacks vs. 4 big knobs, 1 switch (range) and 4 jacks on the Oakley, and a completely separate VCA. I plan to add an LED to indicate the EG output level too. A tiny LED can fit in between stuff.
Wow, Thanks :hail: and COOL! :tu:

Make sure you post pics.

I may be low on 12p headers so, I may need to make an order. Inventory is this evening. Right after I feed my birds :)

Thanks Richard, I'll respond officially whan I get to that side of the computer.

G

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Post by pugix » Tue May 11, 2010 7:05 pm

Right after I feed my birds
My birds are really scarfing down the black oil sunflower seed this spring! Lots of cardinals here, but lately a gang of grackles is lording it over the feeder. Hey, they all gotta eat!

Or did you mean your parakeets? :confused:
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Post by mmm » Tue May 11, 2010 7:20 pm

pugix wrote:
Right after I feed my birds
My birds are really scarfing down the black oil sunflower seed this spring! Lots of cardinals here, but lately a gang of grackles is lording it over the feeder. Hey, they all gotta eat!

Or did you mean your parakeets? :confused:
I have a pair of cockatiels that I've known since they were eggs.

They'll be 23 YO this July. Apparently, feeding them works. :tu:

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Post by mmm » Tue May 11, 2010 7:23 pm

Oh, yeah,

I was low on connectors, so:

Richards: yes, all of the Richards that ordered and AB,

Connectors will be here Thursday.

:mmm:

I think I'll limit the next sale to just the Michaels out there :hihi:

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Post by Adam-V » Tue May 11, 2010 10:14 pm

I'm Michael and so is my wife....

Cheers,
Adam-V

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Post by mmm » Tue May 11, 2010 10:41 pm

Adam-V wrote:I'm Michael and so is my wife....

Cheers,
Adam-V
There's two!!! :sb:

On a more serious side. The VC Dual LFO sale ends tomorrow at midnight PDT.

I might even have enough connectors by the next morning. :party:

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Post by klstay » Wed May 26, 2010 11:18 pm

Looks like the same asswipes changed the page again?

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Post by klstay » Wed May 26, 2010 11:21 pm

Also, what is the response curve on these?

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Post by mmm » Thu May 27, 2010 12:39 am

klstay wrote:Also, what is the response curve on these?
Thanks, I fixed the page. IDK why people do that. :pan:

The response curve is linear.

G

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