quad slew

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Navs
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quad slew

Post by Navs »

Repurposing an unused A-180 multiple as a quad passive slew:

http://navsmodularlab.blogspot.com/2010 ... -slew.html

:)
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dude
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Post by dude »

more slew!
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en.
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Post by en. »

uhuh! thank you navs and fonitronik!
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Smooth Operator
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Post by Smooth Operator »

Great idea! :tu:
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Thonk Support
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Post by Thonk Support »

brilliant.. am I right in thinking the A180 has no other components, purely ganged connectors? If so then this is a very simple DIY project without an A-180 also.
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fonik
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Post by fonik »

absolutely, monobass.

it is actually nothing but a fixed lopass filter. there are quite a few passive module designs you could easily build as a start. what about a switch to select from different cap values? this would give you a passive 6db lopass with selectable cutoff (has been made by moog in the past millenium :wink: - see below). or what about fixed hipass, attenuators, multiples, switches (selectors)... all you need is a cheap soldering iron from the hardware store, believe me, it is sufficient for a start.

anyways, navs module will be very useful for everyone who frequently uses gates for VCAs...

Image
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stk
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Post by stk »

Could this be modified to use a pot for variable cutoff/slew?
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fonik
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Post by fonik »

no, actually not.
by replacing the resistor with a pot you would not just change the slew rate but also change the level. in other words, the slower the slew the lower the signal level. for your ears the lowering of the level would simply whitewash the effect of changing the slew.
to prevent this you would have to use opamps as buffers, thus having an active module.

as i mentioned above you could use a switch for selecting capacitors of different values (as seen on the moog schematic above). the larger the cap, the slower the slew...
Last edited by fonik on Wed Jul 07, 2010 9:36 am, edited 1 time in total.
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haesslich
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Post by haesslich »

with a 4051 and a counter you could replace the switch by a trigger signal... okay, again this would be an active module ;-)
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stk
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Post by stk »

Thanks for the info, fonik.
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itijik
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Post by itijik »

This is nice. I was thinking that this would be perfect to use with the A160-161 outputs! :hyper:

(oh, you mention the RCD on your article...YAH!)
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Post by itijik »

Are the values used for this filter the same values used on the fonik mixer, heard here?... http://navsmodularlab.blogspot.com/2010 ... ixing.html
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fonik
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Post by fonik »

no. far from that. in fact it is a different configuration. the fonitronik attenuverting mixer uses a highpass configuration to remove offset.
and it uses a 22uF, that gives much longer times anyways.
nav wanted to remove the 'pop' of the VCAs caused by those steep rising edges, so he wanted to smooth them just a little bit. yo won't even recognize it on slowly changing CVs.
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Post by Thonk Support »

fonik wrote:absolutely, monobass.

it is actually nothing but a fixed lopass filter. there are quite a few passive module designs you could easily build as a start. what about a switch to select from different cap values? this would give you a passive 6db lopass with selectable cutoff (has been made by moog in the past millenium :wink: - see below). or what about fixed hipass, attenuators, multiples, switches (selectors)... all you need is a cheap soldering iron from the hardware store, believe me, it is sufficient for a start.

anyways, navs module will be very useful for everyone who frequently uses gates for VCAs...

Image
I like the idea of making some manual switches with adjustable slews :)
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itijik
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Post by itijik »

Thanks fonik!
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dequalsrxt
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Post by dequalsrxt »

that'd be nice to do to one of the sets of multiples on the 1u modular world utility strip... might have to do that. cheers! :guinness:
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fonik
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Post by fonik »

Monobass wrote:I like the idea of making some manual switches with adjustable slews :)
the values from the moog module are for audio, primary. you may want to try different cap values for CV.
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DGTom
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Post by DGTom »

Great use for a "useless" module :hihi:

For "random" slew, use an LDR instead of a normal resistor (or in parallel)

Bend the LDR so it faces inside the case or towards the crack in between modules for differant amounts of "random"

@Navs; have you tried stacking multiple RCD outs into the input?
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[Djo]
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Post by [Djo] »

Thank you for this tip navs!

I made mine with a switch. I use 1µ and 4.7µ.

Edit : 4.7µ is too small, I put a 6.3µ on parallel and it's great. ;)

Sound example :
Soundcloud A180 Mod Slew
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en.
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Post by en. »

:tu:
it could be nice also with a three position selector 1-off-2
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itijik
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Post by itijik »

I made mine today! I did the top four like navs did (1uF), to kill pops. For the other sets, I used 4.7uF and 10uF just for fun.
I just cut a few traces, so I wouldn't have to de-solder the whole thing...
Image

A really easy and effective mod, thanks again guys! :tu:


Oh, and ignore the cold solder joints ;)
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stk
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Post by stk »

[Djo] wrote:Thank you for this tip navs!
I made mine with a switch. I use 1µ and 4.7µ.
Edit : 4.7µ is too small, I put a 6.3µ on parallel and it's great. ;)
Great first post :banana:
Thanks for the audio examples, they're always appreciated.
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[Djo]
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Post by [Djo] »

Great first post :banana:
Thanks for the audio examples, they're always appreciated.
Thank you stk!

I have learned a lot here but my poor English vocabulary and my shyness prevent me from sharing my knowledge... :confused:

Hmm... Pratice makes perfect! :roll:
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Cat-A-Tonic
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Post by Cat-A-Tonic »

fonik wrote:as i mentioned above you could use a switch for selecting capacitors of different values (as seen on the moog schematic above). the larger the cap, the slower the slew...
What about using a variable capacitor like the ones in old crystal radios?
They can be used in passive applications right?
<iframe src=https://audius.co/embed/track/Eq4Qw?flavor=card width="100%" height="480" allow="encrypted-media" style="border: none;"></iframe>

<iframe src=https://audius.co/embed/track/bQ2RM?flavor=card width="100%" height="480" allow="encrypted-media" style="border: none;"></iframe>
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Navs
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Post by Navs »

Wow! Amazed to see this has inspired others to DIY their own :)

Been at the lakes trying to escape the crazy heat in Berlin - thanks to fonik for jumping in with his expert advice.

I've been meaning to do this for ages. Getting the suitable values encouraged me to build it. I unscrewed the cliff jack/ pcb from my mult as I had some left-over jacks from an aborted project.

Cutting the traces and soldering onto the board looks like a neat solution and I particularly like the switched version :tu: I assume you sacrificed one input to make this possible? This was an option I considered, but I would have liked to have had 4 inputs, so the module would have been 6HP+.

There are other passive filter suggestions in Nicolas Collins' Handmade Electronic Music book and I remember seeing the Moog schems at the em-forum. I bet that was fonik too ;)

Another module I wanted to build was a quad gate to trigger converter. Am I right in guessing a passive HPF would do the trick?

Oh, and yes: feeding the quad slew with four RCD outputs works a treat!

And another trick: you can cascade the slews for quad-rounding e.g. slew 1 > slew 2 etc. I love open designs :sb:
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