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4066 operation
4066 operation
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Old 25th August 2019, 03:51 AM   #11
benb is offline benb  United States
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4066 operation
Quote:
Originally Posted by audiostrat View Post
Hello,

I am posting to ask a simple question about the common analog switch 4066.

Can the power supply (and the control signals) to this IC be completely isolated from the analog path that will be injected into the switch I/O? No ground connection between them. In other words, can it be used as a "relay" where the "coil" circuit (IC power supply) has nothing to do with the switching path.
Short answer, no.

Longer answer, the signal must stay within the voltages at the power pins of the 4066. At the 4066's maximum operating voltage of 15V, the signal must have a peak value of within + and - 7.5V (actually, probably a volt or so lower than the power voltages). This is usually how the 4066 is connected for audio, the power pins are at -7.5 and +7.5, the control voltage switches between these two voltages, and the signal (with a nominal DC level of 0V) can be DC connected to the switch.

This all presumes a line-level (from a CD/DVD player, TV sound "line output," FM tuner and such) signal. It's possible to switch a signal directly from a phono cartridge, but you'd get much better performance running it through a standard RIAA preamp first and switching the preamp's output. It's basically not possible to switch a "speaker level" signal with a 4066.

We can give you better help (with probably shorter responses, not mentioning things we think you might want to do but cant) if you're more specific about what you want to do.
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Old 29th August 2019, 04:28 PM   #12
audiostrat is offline audiostrat  Greece
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Many thanks for all your answers.

Actually, I want to switch / route analog signals with no clicks or pops. The signal levels will be guitar levels - in the era of a couple of millivolts up to 1-2V or so.

Since I haven't found any means of doing it flawlessly (=every analog switch IC I read about and can buy does not seem to be good enough, and I don't have much time to try them), I decided to incorporate a "master" mute circuit at the output to noiselessly perform any switches when they happen.

Since I wanted to isolate the analog power supply rails from the switches, I found it preferable to switch using relays and a single isolated supply for their coils. The relays I am planning to use are Fujitsu RY-12W-K, instead of using 4066 ICs.

So the question could be rearranged: could the 4066 act as a reliably quiet analog switch (which hardly seems to be the case)? Or would the Fujitsu relays or other ICs perform better in that regard?

To cut the story short, I am currently favoring relays over 4066 since they require simpler power supply (single ended, and only one for 20 coils I will be using). I have read that relays usually don't provide noiseless switching too.

If you think / know the 4066 or a similar switch can be completely quiet when switching please share it!
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Old 29th August 2019, 04:40 PM   #13
Kay Pirinha is offline Kay Pirinha  Germany
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Btw, some time ago we've had a discussion on a pin compatible equivalent, but with improved properties (lower on resistance, higher isolation resistance, lower distortions). Sadly, I don't recall the designator any more. Could someone please help me?
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Old 29th August 2019, 05:39 PM   #14
JMFahey is offline JMFahey  Argentina
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Quote:
Originally Posted by audiostrat View Post
Many thanks for all your answers.

Actually, I want to switch / route analog signals with no clicks or pops. The signal levels will be guitar levels - in the era of a couple of millivolts up to 1-2V or so.
Yes, keep them well below 15Vpp .

Quote:
Since I haven't found any means of doing it flawlessly (=every analog switch IC I read about and can buy does not seem to be good enough, and I don't have much time to try them), I decided to incorporate a "master" mute circuit at the output to noiselessly perform any switches when they happen.
1) you CAN switch noiselessly, just be careful with grounding, switching waveform (hint: no *abrupt* edges which bcan feed through) and making certain DC at both sides of the switch is same value.

Quote:
Since I wanted to isolate the analog power supply rails from the switches, I found it preferable to switch using relays and a single isolated supply for their coils. The relays I am planning to use are Fujitsu RY-12W-K, instead of using 4066 ICs.
So it´s a ready made decision ... I wonder why you ask about 4066 then.

Quote:
So the question could be rearranged: could the 4066 act as a reliably quiet analog switch (which hardly seems to be the case)? Or would the Fujitsu relays or other ICs perform better in that regard?
IF it´s quiet enough as a "main switch", it should be quiet enough for internal switching, wouldn´t it?

Quote:
To cut the story short, I am currently favoring relays over 4066 since they require simpler power supply (single ended, and only one for 20 coils I will be using). I have read that relays usually don't provide noiseless switching too.
Yes, relays are conceptually simpler.
Relays can be noiseless, you´ll also have to be careful about switching signal, DC levels on both sies of switch contacts, etc.
All require somewhat careful planning.
Hey, even a fingertip operated switch requires care.
Quote:
If you think / know the 4066 or a similar switch can be completely quiet when switching please share it!
Yes, it can, see above.

More specific, I bet 4066 (and 4053, etc.) datasheets or application notes have some pages on noiseless switching, control signal debouncing, etc.

Go straight to Manufacturer´s data instead of endless reading Forum posts written by none too savvy and contradicting Members.

Go straight to the source.
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Last edited by JMFahey; 29th August 2019 at 05:44 PM.
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Old 29th August 2019, 05:47 PM   #15
nigelwright7557 is offline nigelwright7557  United Kingdom
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Clicks and pops come from switching different dc levels.
Make sure input and output DC levels on the 4066 are the same and there shouldn't be a problem.
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Old 29th August 2019, 05:51 PM   #16
audiostrat is offline audiostrat  Greece
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Quote:
Originally Posted by JMFahey View Post
Yes, keep them well below 15Vpp .


1) you CAN switch noiselessly, just be careful with grounding, switching waveform (hint: no *abrupt* edges which bcan feed through) and making certain DC at both sides of the switch is same value.


So it´s a ready made decision ... I wonder why you ask about 4066 then.
If I was confident that 4066 will switch noiselessly, I would go for it! Pardon me for the misconception, I actually mean that since 4066 don't seem to be able to work better switch-wise, I would prefer the relay.

As far as switching the relay goes, if I needed to get them to switch noiselessly, I have also read that I need to eliminate DC difference between the terminals of the switch.

Isn't that possible using AC coupling (RC filters) plus a "bleed" resistor to ground in each terminal? The caps of the filters being very low leakage of course..
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Old 29th August 2019, 06:05 PM   #17
synonymous is offline synonymous  United States
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If you can incorporate differential (balanced) line in your circuit it may also help in some way.
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Old 29th August 2019, 06:08 PM   #18
Mooly is offline Mooly  United Kingdom
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4066 operation
If you switch any signal at any non zero point you will get a click or pop.

For example if you switch a 1 volt peak sinewave when it is part way through the cycle then you will get a sudden output voltage corresponding to the point on the sine the switch is closed. That step change in level generates a sudden click.
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Old 29th August 2019, 06:48 PM   #19
audiostrat is offline audiostrat  Greece
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Quote:
Originally Posted by Mooly View Post
If you switch any signal at any non zero point you will get a click or pop.

For example if you switch a 1 volt peak sinewave when it is part way through the cycle then you will get a sudden output voltage corresponding to the point on the sine the switch is closed. That step change in level generates a sudden click.
I understand that, and for my application this is not a problem: my switcher should not make any pops when there is no signal present, if the user decides to switch while a signal is still "dancing" I would not consider any pops problematic, but something to be expected.
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Old 29th August 2019, 08:41 PM   #20
MarcelvdG is offline MarcelvdG  Netherlands
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For balanced line level audio signals, I've made switching circuits with both relays and 4051 multiplexers that produce no audible switching sounds at normal volumes, except for the sound of the moving parts of the relays. I haven't a clue how far you get with millivolt signals and possibly higher source impedances, though.

I guess I'd go for something with very little or very slow charge injection, like a small photo-MOS optocoupler or a JFET with slowly switched gate voltage (that is, switching signal filtered with 1 Mohm-100 nF or so).
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