speaker selection switch via relays

For reasons beyond me, the speaker selection was never installed on our desk.
While we do have the controls installed and they do function, the additional circuitry is M.I.A.

From the control panel I get the following action, 4 X speaker selects and when I select one, I get 24VDC at an edge connector pin. If I switch to a different one, I get 24VDC and a different pin. This is all in reference to ground.
From what I have been told  when the desk was installed by a former, the owner was asked how many speakers he wanted, at the time he had only need for one set so they did one set and the selector was never installed.

Since it is M.I.A. I would imagine I can get away with the following
A box that has  2 x inputs feeding  4 stereo  outputs and relays in between.  I could then use the 4 buttons to trigger the relays to open allowing signal for one set of outputs and then switching it over  to another set of relays as each button is pushed.

I would imagine I could get away with just the relay and the flyback diode but I would imagine there will be pops or clicks, does anyone have a good way to tame that action?

If you use good relays like the Panasonic TQ2 series, noise shouldn't be a problem.  Amek used hundreds (thousands?) in the "Rupert Neve" 9098 desks ( 5 Volt coils IIRC) for a variety of line level switching tasks and noise was never an issue.

https://www.mouser.com/ProductDetail/Panasonic-Industrial-Devices/TQ2-24V?qs=sGAEpiMZZMt0JUFY9eAysiXiTsrHHyCY

Note that the coil is polarity sensitive.

Bri

Brian Roth said:

If you use good relays like the Panasonic TQ2 series, noise shouldn't be a problem.  Amek used hundreds (thousands?) in the "Rupert Neve" 9098 desks ( 5 Volt coils IIRC) for a variety of line level switching tasks and noise was never an issue.

https://www.mouser.com/ProductDetail/Panasonic-Industrial-Devices/TQ2-24V?qs=sGAEpiMZZMt0JUFY9eAysiXiTsrHHyCY

Note that the coil is polarity sensitive.

Bri

Click to expand...

Yes... I have those on order, they arrive in a few days. 

breadboarded something ugly looking but it works as follows


tq2-24V relay with in4005 flyback diode, 4005 where what is in the parts bin. I added 2 leds and current limiting resistor so as the relays change on the breadboard, the leds follow to show you which is working and which is off.

it is housed in a large junction box with connectors so all people see is in and out connectors, along side the wires feeding the control faceplate on the desk. 

it might be simple, it might be ugly, but dam does it get the job done

As I mentioned, those Panasonic relays were used by the hundreds in the Amek/Rupert 9098 desks.  I went back and looked at some pix I had of the input modules that I took of an early "split" 9098 and there are at least 16 TQ2 relays per channel.  I maintained that desk for a few years....had one TQ2 fail on a 48 x 48, and switching noise was never an issue.

A few small switching things I've done since then with those relays were flawless.

Once again for folks reading this thread.....all TQ2 relays have a polarized coil.  Wrong control voltage polarity
on the coil, the relay just sits there and quietly looks at you.  lol 

I had pondered making a drop-in adapter for the American Zettler (sp?) relays used on early MCI 400 series desks.  Looking at the ancient schematics I seemed to find the relays were operated with random polarity powering, so it would take a full wave bridge on the adapter board to make the relay "agnostic".

Never got around to that PCB design project.....<g>

Bri

Brian Roth said:

As I mentioned, those Panasonic relays were used by the hundreds in the Amek/Rupert 9098 desks.  I went back and looked at some pix I had of the input modules that I took of an early "split" 9098 and there are at least 16 TQ2 relays per channel.  I maintained that desk for a few years....had one TQ2 fail on a 48 x 48, and switching noise was never an issue.

A few small switching things I've done since then with those relays were flawless.

Once again for folks reading this thread.....all TQ2 relays have a polarized coil.  Wrong control voltage polarity
on the coil, the relay just sits there and quietly looks at you.  lol 

I had pondered making a drop-in adapter for the American Zettler (sp?) relays used on early MCI 400 series desks.  Looking at the ancient schematics I seemed to find the relays were operated with random polarity powering, so it would take a full wave bridge on the adapter board to make the relay "agnostic".

Never got around to that PCB design project.....<g>

Bri

Click to expand...

We used/still use the 12V versions in all of the Avalon equipment  and the 24V versions in the mastering eq. 

Ive built several 4 in 6 out switching systems for customers using relays with no pops. Using 555s in conjunction with opto-isolators  so I could use pretty illuminated momentary push-buttons.
Another option is using cd4043 with relays which works really well.
Eventually i ended up using arduino nano's and teensy's after I wrote some code as that was something I could easily duplicate and add functionality too.
Just some thoughts.

Rocinante said:

Ive built several 4 in 6 out switching systems for customers using relays with no pops. Using 555s in conjunction with optometrist isolates so I could use pretty illuminated momentary push-buttons.
Another option is using cd4043 with relays which works really well.
Eventually i ended up using arduino nano's and teensy's after I wrote some code as that was something I could easily duplicate and add functionality too.
Just some thoughts.

Click to expand...

we already have the buttons that light on the surface so this was easy

well this is perplexing... I measure 24VDC(ref to chassis GND) unloaded.  when I attached in the relays and hit the button to trigger them I get a voltage drop. With a single relay it drops down to 17VDC, if I do two dpdt relays in parallel it drops down even further to the point it will not trigger the relays at all. If I test the same circuit using a 24VDC wall wart @ 1 amp, everything works as it should. so not sure why 2 Leeds and series and a parallel connection between the relays and less would cause such a voltage drop.  At any rate for now the solution is add a third relay that the desk triggers and is wired to get voltage from the wall wart and send it as needed.  it seems to work for triggering the extra relay per button and the specs of the tq2's can handle the VDC and current. So I should be o.k.  MY other option is to work out  how the existing card cage with relays mates to this but it looks like parts are MIA because none of the connectors mate and there is no documentation.  not sure which would be faster to work out...

well, I was going to say...

24V, sure. but what source resistance? -And what Imax?

Add a power supply, and use the supplied voltage to saturate the base of switching transistors.

Or use opto-isolators. Always a good bet.

keef!!!! I hope this finds you well mate.

For now the temp solution will be to bypass the desk controls and have an external control box.  I found the missing  bobs and bits but I have no schematics and they do not match any of the current mating connections so will have  draw me a schematic and test and measure things.