Dead Ensoniq OEX-8 outputs


First post here… and hello. I’ve just gotten an OEX-8 for my Ensoniq EPS. Unfortunately, outputs 1 and 3 don’t function. The rest are fine. Continuity tests suggests that the cable is fine, as are all of the output jacks themselves. I am wondering if anyone here has any insight they might share (or a schematic for the OEX-8 - I am happy to purchase one from Syntaur if such a thing is available).

Is there any potential danger in connecting the OEX-8 to the EPS to make use of the working outputs?

Any advice would be greatly appreciated.


Nothing, huh? Well, further exploration has revealed other symptoms.I’ve now got crackling and intermittent signal on some other outputs - and a few of them sort of “faded in” when I first triggered something through them (just the default square wave generated by the EPS). Granted, this was using a different D-Sub cable (the one that came with the OEX-8 worked, but has loose pins, so I bought another on eBay), so I wonder if that had anything to do with it.

I would love to get this thing working…


My guess is that circuitry is failing somewhere on the OEX-8 circuit board. The outputs of this expander are created by a digitally multiplexed signal from the EPS, then the OEX-8 decodes that digital signal and creates analog outputs. In other words, it’s not just a ‘splitter’ box where a dirty contact on a connector pin might lead to crackling on a specific channel. In short, I think the expander is not working, and repair would likely be expensive (in the labor to locate the problem).

It would be ideal to find someone nearby who has an expander, and would let you test it on your EPS - that would let you isolate the problem to either the expander itself (that’s what my money’s on), the cable, or the EPS.


Thanks Sam. I am sure it’s the OEX-8, as I’ve tried two cables and two EPS’. We’ve confirmed that the jacks work, as do the TL072s. Now, we only checked those when we thought only outputs 1 and 3 were bad. Now we’re wondering if it’s the demultiplexor. I’m keeping my eyes out for another OEX-8, but they don’t seem to be too common.