Audio / Video source switching IC options?

[mkiijam]

Simple idea and it has been done a thousand times, but I find myself not being able to find a clear answer.

Say for instance the INPUT buttons on a Home Stereo Receiver. "CD" "RADIO" "PHONO" etc. You push one switch and the systems selects it and deselects the previous choice. BTW, I'm not even sure what to call this function.

Now, is there a chip or circuit (IC) that is the grand-daddy of them all for this function? I have seen it done Multiplexors, Decade counters, MCU, and of course mechanically with interlocking switches. I even dreamed up a system with latching relays and diodes, but... ISN'T there an existing off the shelf "INPUT SWITCHING IC" that does NOT require data and clock? Like an analog switch or something? If not, is the 4017 circuits really the best way to do it??? 

[Terry Bites]

Answer, I very much doubt it. Very much. What market would there be?
A ring counter is probably the easiest (least parts) to implement.

I'd call it a tristable.

Here's a fun thing- the RCs are debounce.

[Someone]

Here's a fun thing- the RCs are debounce.

Ugly having to use RC in feedback!

ISN'T there an existing off the shelf "INPUT SWITCHING IC" that does NOT require data and clock? Like an analog switch or something?

"radio button" is the UI term, but there isn't a chip as volume production uses either a mechanical switch or jams all that into the firmware. Has been visited on here with some hardware solutions:
https://www.eevblog.com/forum/projects/discrete-logic-design-vs-a-super-cheap-micro/

[Ian.M]

Also see https://www.eevblog.com/forum/projects/selector-switch-using-push-buttons-(e-g-like-source-selection-on-an-hifi-amp)/
I suspect the CD4028 + feedback resistors was a popular choice 'back in the day'

[paulca]

I've used some H74 transceiver chips with the clock pin pulled low as passthrough level convertors.

This is not an application mentioned in the datasheet, but it works.

I wonder if the H74 series multiplexers will also "freeze" in passthrough with the right bit of torture and cajoling.

On second thoughts... they will, clock or no clock all be based on logic levels.

[mkiijam]

Here is the electro / mechanical version, just to be clear.

[Benta]

This would be my way of doing it (inputs need pull-down resistors for the switches and a reset circuit has to be added to the FFs):

[cantata.tech]

Answer, I very much doubt it. Very much. What market would there be?

Japan was very successful at turning out millions of them, primarily designed by Sanyo and made billions of dollars making audio systems.

These IC's already exist.

Actually, on some of them they do nothing. All the wires seem internally bridged. The controller just carefully stops one (powers it down) before starting another (powers it up).

Hate to say smoke and mirrors, but I don't know the technical words for any other way to describe them.

[mkiijam]

These IC's already exist.

Do you know of a part number?

[coromonadalix]

https://www.analog.com/media/en/news-marketing-collateral/product-selection-guide/choosing_switches_or_muxes.pdf

https://www.analog.com/media/en/technical-documentation/data-sheets/ADG798.pdf

https://www.ti.com/lit/ds/symlink/lmh6574.pdf?ts=1674667794802&ref_url=https%253A%252F%252Fwww.google.com%252F

https://www.analog.com/en/products/dg1207.html#product-overview

[mkiijam]

I appreciate the links. I'm reading through these.

Quick question in case you know, Do these chips allow for momentary switches to be used to latch the output until another is pressed? If not, then they of no use to me.

[Benta]

Quick question in case you know, Do these chips allow for momentary switches to be used to latch the output until another is pressed? If not, then they of no use to me.

No. They're simply analog switches, like the 4051 in the circuit I posted.

[cantata.tech]

These IC's already exist.

Do you know of a part number?

It wouldn't be just one part that you need unless you're
looking for the whole unit:

https://www.jaycar.com.au/search?text=video+selector

For something more DIY, here's a project where someone else has done aone just for audio it. Video requires extra channels.

https://hackaday.com/2015/11/02/escape-cable-hell-with-a-multi-io-audio-multiplexer/

[IDEngineer]

Look up routing switchers, that's the system level solution. They come in audio, video, and both. Dig into how they handle things internally. I used to design those waaaay back in the 80's and at that time the signal path was done with discretes because there were no IC solutions with sufficient signal quality. Hard to believe that hasn't been addressed since. A bit of research should reveal something.

[mkiijam]

Look up routing switchers, that's the system level solution. They come in audio, video, and both. Dig into how they handle things internally. I used to design those waaaay back in the 80's and at that time the signal path was done with discretes because there were no IC solutions with sufficient signal quality. Hard to believe that hasn't been addressed since. A bit of research should reveal something.

See my schematic back in the chat a ways. I beleive that's how it would be done the electro-mechanical way. The pure mechanical way is interlocking switches, but I hate those...

[IDEngineer]

No, routing switches have an electronic signal path. They might have switches on the front panel to select the path, but the switching is done electronically. True even for the video versions, even back in the 80's. Nobody wants to use hard contacts for this stuff.

[Benta]

I'm astounded that the knee-jerk reaction "throw an Arduino at it!" hasn't cropped up yet...

[Ian.M]

I'm astounded that the knee-jerk reaction "throw an Arduino at it!" hasn't cropped up yet...

Now you've done it! 

Using a cheap MCU to control analog switches (or similar) is entirely too obvious, and probably the best choice from a BOM cost perspective.   If its for production, get them factory pre-programmed and drop-shipped to your PCB assembler.

[themadhippy]

several methods are  shown on  https://sound-au.com/project163.htm

I'm astounded that the knee-jerk reaction "throw an Arduino at it!" hasn't cropped up yet...

T'is exactly what i done,and i try and avoid the buggers  if at all possible,but after spending far to long in the rabbit hole  i went for the easiest option, it also made controlling the relays for the switched attenuator  much simpler.

[paulca]

For something more DIY, here's a project where someone else has done aone just for audio it. Video requires extra channels.

https://hackaday.com/2015/11/02/escape-cable-hell-with-a-multi-io-audio-multiplexer/

This is a rather poorly implemented version of my current project.  The difference is, all mine IO are digital and I don't want no stinking 1 to 1 routing nonsense. I want full many to many with mix and EQ.

But overall it's the same goal.  To not have to swap cables around to have multiple sources.

[paulca]

I have seen, what I consider, hacky techniques on my travels through audio forums.  Mostly relating to digital streams, but the principle should still apply.

Instead of switching the inputs per-sae, enabled/disable/mute inputs and wire them all together.  So when you want to switch from one source to another, it just mutes one and unmutes another.  Mutes or Enables.  If you have 2 I2S devices, it will pull the enable pin high on one source and pull it low on the next.  The sources carry on playing, it's just their outputs are disabled and only one at a time makes it to the next stage.

In analogue audio terms a buffer opamp with gain of 0 or 1 for each input.

For video, that might also work, depending on the video stream and the opamps.

[mkiijam]

Whether it is switching the MUTE or the INPUT or the OUTPUT or CREAM or SUGAR, the real issue for me is:

Pressing one button "un" presses ALL others. It matters not what the buttons control. i.e. if they control mutes or source selects or when the cows come home.

Just that there is an automatic deselect of everything else. THAT is the trick. Again, think of the mechanical interlock switch array or the schematic I drew.

[David Hess]

Now, is there a chip or circuit (IC) that is the grand-daddy of them all for this function? I have seen it done Multiplexors, Decade counters, MCU, and of course mechanically with interlocking switches. I even dreamed up a system with latching relays and diodes, but... ISN'T there an existing off the shelf "INPUT SWITCHING IC" that does NOT require data and clock? Like an analog switch or something? If not, is the 4017 circuits really the best way to do it???

Implementations varied over time as technology changed.

Modern implementations use CMOS switches and multiplexers.  Before this, JFET integrated and discrete switches and multiplexers were used, and before this, "chopper" bipolar transistors were used.

At higher frequencies there are bipolar transistor switches and multiplexers which work with currents instead of voltages and are often based on the Gilbert cell multiplier.  One of the first, and longest lived, ICs Tektronix made for themselves was a channel switch for operation up to 200 MHz.

[Benta]

Pressing one button "un" presses ALL others. It matters not what the buttons control. i.e. if they control mutes or source selects or when the cows come home.
Just that there is an automatic deselect of everything else. THAT is the trick. Again, think of the mechanical interlock switch array or the schematic I drew.

Already posted in reply #6. It's impossible to select more than one input or output. Don't you read the answers?