SPL 2489 monitor controller talkback mod?

[CLee]

I have an SPL 2489 Surround Monitor Controller. Nice piece of gear but it does not allow a talkback switch to dim the monitors. I popped the top to see what was in there and it looks like a pretty complicated mod to tap into the dim switch. Has anyone done this?

I'm going to try to get info from SPL, but any advice would be much appreciated...

[CLee]

No one?

[Richard Fairbanks]

What do you use for talkback now? Most devices have a talkback microphone output but very few have a logic output that mirrors the talkback switch. Even if they do, you have to overcome the way talkback and dim functions are usually implemented. Talkback is typically "on" only when the switch is held down, whereas dim or mute are typically operated with a switch "push on" followed by a separate "push off". I imagine that is how SPL works, but I don't have experience with one. Wiring onto the SPL switch is easy and that is probably what I would do. Detecting the talkback switch can be done in a couple of ways, but making the logic work between your talkback button and your SPL will take a little cleverness. I would probably use a self contained programable board like Basic Stamp . It has everything needed to do the job, assuming you can mount it into the SPL and "borrow" some power for it. You will most certainly void all of your warrantees by wiring onto switches. I wouldn't be afraid to do it but it requires some skills beyond a soldering iron.

[CLee]

I'm using the talkback button on my Pro Control, as well as inputing a remote producer talkback switch into the PC. My thinking is to tap into the PC logic signal and use that to drive relays mounted inside the SPL box that work as momentary bypasses of the dim switch. The dim on the SPL is indeed push on/push off so the contacts will have to be broken and bypassed with a pad when the talkback is engaged.

Not impossible to do but I was hoping someone had tackled it before and had a wiring diagram. SPL Germany was no real help except to say you needed relays, which I figured already.

The alternative is to make inline "little boxes" going from the output of the SPL to the input of my monitors with relay engaged pads. Then I need to build a whole power supply, but it might be easier than messing with the SPL dim switch

[Richard Fairbanks]

Yes, it would be easier except for the pesky power supply. They make a mechanical sound that is helpful, they can alert you that your client pressed the talkback button (electronic switches are silent). Relays are easy but they get dirty and so I hate them. No matter where in the signal chain you put them they can cause intermittent/noisey operation, or outright distortion. You have to clean them regularly to keep them sounding like "a straight wire". They do "mute" easily, but "dim" is a little more involved. That is why I was thinking of a way to use the dim feature already built into the SPL, and to borrow power from the SPL. But you're right, it would not be as simple. Best luck!