DIY slew circuit?

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wetterberg
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DIY slew circuit?

Post by wetterberg » Mon Nov 17, 2008 8:23 pm

Hey all
I'll be needing an octuple slew unit for a device I'm dreaming up, and I'm looking around for a proper slew device...

I seem to remember that slewing something == lowpassing it? So variable slew== variable cutoff lowpass?

It needs to be simple, but ideally it will have one control across all 8 slews, making it neccesary to do an active circuit... Just wondering if you guys had any ideas?

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Post by Cat-A-Tonic » Mon Nov 17, 2008 8:32 pm

Maybe you could build a Harry Bissels and mult the 3 pots out to the other circuits.
I have no idea if this is possible.
Can you mult pots to multiples of the same circuit for universal control of several channels?

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Post by wetterberg » Mon Nov 17, 2008 9:08 pm

funny, I had googled and searched my brains out for "slide" "glide" "slew" etc, but not "lag" - the Harry Bissell Morph-Lag circuit is just 5usd from CGS! Thanks man! I didn't know that schematic was a diy staple!

I'm afraid that "multing" the control wouldn't be possible unless using vactrols... I don't know if I want to go there.... but I would never rule it out, either!

Here's something I could sink my teeth into, though - just found this thread on electro-music - talk about breadboard friendly - a TL072, a cap, a pot and two jacks!

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Post by Cat-A-Tonic » Mon Nov 17, 2008 9:17 pm

If you want to go the super small route I'd suggest Bridechambers NanoGlide Dual Lag for only $2!
http://www.bridechamber.com/bridechambe ... 20PCB.html

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Post by A Dingleberry Monstrosity » Tue Nov 18, 2008 1:51 am

unless my EE degree has failed me, any lpf will for the job

im willing to bet me EE degree has failed me.

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Post by neandrewthal » Tue Nov 18, 2008 3:37 am

In the vactrol controlled buchla VC portamento, the setting pot is the same thing as a control voltage, so it's easy to mult it. Just run 15v through your pot and then to each lag.

It's a bit more complicated than a regular lag, though, so I don't know if you'd want to build it 8 times and use $40 worth of vactrols.
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Post by flts » Tue Nov 18, 2008 3:45 am

Isn't that expo glide in the schematic just two unity gain buffers and a variable RC filter between them?

Like ADM, I would've thought any simple LPF would do too, since that what a lag / slew does IS lowpassing. Of course there are extra requirements besides "any lpf" if you don't want to mess up the pitches or want a certain kind of response / slew curve. And I'm no EE.

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Post by wetterberg » Tue Nov 18, 2008 8:24 am

well that's why I asked in my initial post, gents - I too remember it this way.

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Luka
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Post by Luka » Tue Dec 16, 2008 5:02 am

there is a buchla vc-slew circuit going around
ill see if i can find it

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Post by Luka » Tue Dec 16, 2008 5:04 am


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Post by BananaPlug » Tue Dec 16, 2008 9:04 am

Here's a linear lag circuit, simpler than the 3 opamp Bissel circuit you usually see. You should be able to put a VTL5C3 in parallel with the timing resistor and and have a nice VC lag. To replicate the 1M resistance, try the Vactrol paralleled with 1.1M resistor. A dark VTL5C3 should be about 10M.

:hail: All praise Harry Bissel


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Post by Scott Stites » Wed Dec 17, 2008 9:52 am

I love linear lag - it feels more 'natural' to me on a keyboard, but expo lag has its place, too -S&Hs and stuff, and sometimes keyboard, too. I put linear lag on the Klee because it seemed to fit better in that application. The AutoGlide on the Appendage is expo, because that felt a bit more natural in that app.

If anyone is going to build those smaller simpler circuits, it's a good idea to place a 100 Ohm resistor between the first buffer and the pot. Otherwise, when the pot is engaged, you'll often have a bit of detuning. The 100R resistor prevents that from happening. IIRC from my fumblings years ago that may be more the case with linear.

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Post by Luka » Wed Dec 17, 2008 4:34 pm

welcome to muff scott
good to see you over these parts

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Post by Scott Stites » Tue Dec 23, 2008 5:09 pm

Nice to be here, Luka. Who can resist a forum that has both cats and synths?

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Post by flight » Tue Dec 23, 2008 5:58 pm

Wetterberg: In technical terms, a low-pass filter is an integrator. If you integrate a square wave you get a triangle wave, which can be thought of as slowing the output response time of the circuit relative to the input signal.

I don't know if that helps or not though... :)
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Post by wetterberg » Wed Dec 24, 2008 12:07 am

every last bit of geek-fo helps, mate :D :guinness:

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Post by flight » Wed Dec 24, 2008 8:49 am

w00t!
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Post by heapish » Fri Sep 01, 2017 12:15 pm

BananaPlug wrote:Here's a linear lag circuit, simpler than the 3 opamp Bissel circuit you usually see. You should be able to put a VTL5C3 in parallel with the timing resistor and and have a nice VC lag. To replicate the 1M resistance, try the Vactrol paralleled with 1.1M resistor. A dark VTL5C3 should be about 10M.

:hail: All praise Harry Bissel


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Am I right in saying this is passive?

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Post by mskala » Fri Sep 01, 2017 12:18 pm

heapish wrote:Am I right in saying this is passive?
Nothing with op amps in it is passive.
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Post by Navs » Fri Sep 01, 2017 2:29 pm

mskala wrote:
heapish wrote:Am I right in saying this is passive?
Nothing with op amps in it is passive.
This is passive:

viewtopic.php?t=18842

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Post by heapish » Fri Sep 01, 2017 2:53 pm

Never mind, just seen the notes for the power at the bottom. Hopefully I can make a dual one up on board

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Post by masterofstuff124 » Fri Sep 01, 2017 3:08 pm

http://yusynth.net/Modular/index_en.html

check out the dual gated slew

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heapish
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Post by heapish » Fri Sep 01, 2017 7:06 pm

Is the 1meg pot Log? as its processing CV. That chip is 50p, deeeeecent!

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