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Author Topic: 4066's to switch ROM bends in and out?  (Read 844 times)

swiftyfrisko

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4066's to switch ROM bends in and out?
« on: April 01, 2018, 05:02:32 PM »

Hi,

Wondering if anyone can tell me where I'm going wrong here.

I've bent a few 90's romplers with the data and address lines broken out to a patchbay. All good so far.

I want to be able to switch the bends in and out via MIDI and sequence them.

I built the MIDIMUSO CV12 MIDI to gate kit, so I've got 11 5v gate signals to trigger with, and I was thinking I could use 4066 ICs to switch the bends in and out.

However, no joy. I'm guessing this is because of the 4066's  "on" resistance of 125 ohms.  Is that right? EDIT: if that is the problem, would MAX 312 / 394s work? Datasheet states <17 ohms "on" resistance.

If so, is there any way of doing this, is there an alternative switching IC, or am I going to have to use relays?

Thanks in advance  :)
« Last Edit: April 02, 2018, 06:41:48 PM by swiftyfrisko »
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Gordonjcp

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Re: 4066's to switch ROM bends in and out?
« Reply #1 on: May 31, 2018, 11:51:32 AM »

Reed relays might work without being too slow and mechanically noisy, but the power consumption would be pretty heavy.

Your 4066 idea would probably work reasonably okay.

You could try using AND gates.
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swiftyfrisko

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Re: 4066's to switch ROM bends in and out?
« Reply #2 on: July 24, 2018, 03:18:53 PM »

Got something working in the end.

In case it might be useful to anyone else trying to automate similar bends via MIDI, here's what I found: 4066's can't be used for ROM bend switching on any of the six machines I tried it on. There's a resistance of >200 ohms even when the switch is on. Vishay's equivalent switch is better, at around 50 ohms, but still doesn't work. MAX 313 switches are around 10 ohms "on" resistance, the lowest I could find, which seems to work in 95% of cases. They're are around 10 each, but that's all I could find in through hole format.

This is what I wound up with: a MIDIMUSO DCO3 chip which produces up to 11 5v gates from MIDI note on/note off info (as does their CV12 chip). This then drives two MAX quad switches, giving eight switches to patch in total. Very simple but does the job.

Don't buy MAX 312s by mistake like I did, they're normally closed, hence the otherwise unnecessary inverters on the board.

Here it is installed in a bent Korg 03/rw: https://www.youtube.com/watch?v=Q9WlcbT_l9U
« Last Edit: July 26, 2018, 05:29:17 PM by swiftyfrisko »
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