DIY / MacGyver question: Tricking my API A2D into slaving?

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alexdingley
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DIY / MacGyver question: Tricking my API A2D into slaving?

Post by alexdingley » Wed Sep 20, 2017 10:42 am

I guess this is a DIY project... or maybe it's not possible.

I recently acquired one of the early-series API A2D stereo pre-amps with built in converters. I added it to my Antelope Orion 30+ rig as an extra set of ins on the S/PDIF inputs. The Orion is the Clock master, and I do a lot of work in Logic X and PT 12 where I'm jumping from 44.1 to 96 to 192Khz in different sessions. So I'm constantly shifting sample rates.

I have one of the early model API A2D units, where the "sync in/out" ports seem to be mounted to a slightly raised back panel, as if they were an add-on. Though the unit came with these extra BNC ports. I was just told, by a tech support guy at API, that these early units don't chase Sample Rates... you can sync them to external word clock, but you still have to manually set the proper sample rate by dial on the front face of the API unit. So, if you're externally clocking to your Orion, you'd have to remember to set the sample rate manually any time you jump sample rates (this presents a scary possibility for subtle problems if I'm absent minded).

It turns out that these models supposed did have a "gang" mode when you're using more than 1 API a2d together. They have these 9-pin D-subs on the back for ganging multiple API A2d units together, and when you use those, the secondary a2d units WILL slave & chase external clock. You'd know it because the sample-rate light dims out on the front of the slaved unit, and ONLY the 'ext' clock light remains lit.

I'm trying to see if there's a way to work around this.

Is there a pair of pins that can be jumpered on the 9-pin D-Sub, or can I make a cable that would trick the solitary API A2D into thinking it's following the sample-rate of another 'master' API A2d, so that it would actually just slave to my Orion's clock?

I'm not sure if the 9-pin D-Sub is transmitting analog signals or digital info, so I have no idea where to begin. Just figured I'd ask you all to see if anyone has had & solved this exact issue before.

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Randyman...
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Re: DIY / MacGyver question: Tricking my API A2D into slaving?

Post by Randyman... » Fri Sep 22, 2017 5:44 pm

Total guess, but I'd assume it is sending the selected sample rate to the slave unit - either via serial signaling (doubtful) or even a crude shorting of different pins for different rates (pin 1+2 = 44k; pin 1+3=48k; pin 1+4 = 88K; etc). So it is likely a dynamic interface that changes with selected sample rate, and would probably leave you in a similar state as you are now :) .

Just making assumptions over here :cool:
Randy V.
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alexdingley
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Re: DIY / MacGyver question: Tricking my API A2D into slaving?

Post by alexdingley » Sun Sep 24, 2017 6:50 am

Oh yeah... that idea of shorting differently across the different pins might very well be what’s going on. I’ll just quit checking out the teeth on this wonderful horse that was gifted.

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