Troubleshooting a Mcintosh MX4000/MDA4000 Combo

[zinophile]

So, I am not getting sound out of the MDA4000 and into the MX4000, when hooked up to the "proprietary" digital input on the MDA4000. Radio out to amp from the MX4000 works fine.

Here's info and how it is hooked up:

Note: I am using the CD mechanism form my DRX9255 in the MX4000, because the original in the MX4000 is shot (cd won't spin up). Shouldn't be an issue, as they are the EXACT same mechanism from what I can tell (same part numbers, same control board, same hookups).

I have had the MX4000 separately for awhile now, but never hooked up to a test system, aside from verifying that the radio worked. I bought the MDA4000 from a respected member here on diyma. He tested the MDA4000 with a Clarion cd changer and his DRX9255, to verify operation before agreeing to sell it to me, so it should be good. Was packed/padded well when shipped.

So:
Digital out of MX4000 (grey/black end of DCA-005(?) cable), into the digital input on the MDA4000 (black end of DCA-005 cable), out of the MDA4000 output (analog RCAs), and back into the analog input on the MX4000 (RCAs, and not the AUX in input).

I have two of the Clarion/McIntosh digital cables, and no sound out with either one. I know they are working, at least up to the black connector (processing end) that plugs into the MDA4000, because I disconnected the connector from the cable, and I see the red glow of the optical signal being sent at the end of the cable. I have a third DCA-001/002 Clarion cable, but godammit, I can't find it anywhere. F!

I have also tested the BNC input on the MDA4000 and everything is fine there. Digital signal into the MDA4000 (from my Fiio X3), analog signal out from the MDA4000 and back into the MX4000 through the AUX In input. Sounds awesome!

Some ideas:

1) Can I actually have two bad processing ends on the digital cables? They look brand new. How can I test if any signal is coming out the end plug, after optical is converted to use the Clarion input?

2) Can I test anything signal-wise with a voltmeter, at the output RCAs on the MDA4000?

3) Could the input section going back into the MX4000 be bad somehow? Any way to test this?

Anyway, any help troubleshooting is MUCH appreciated. I am really frustrated.

 

[mpaschetto]

I'm interested in your results, because I've got a similar problem with my MX4000/MDA4000 combo.
My issue is distorted sound from the CD player.

My FM tuner sounds fine.

I've listened to the output straight out of the DAC with my headphone rig, and it sounds perfect.
Only when that DAC output is looped back into the MX4000 does the CD source sound badly distorted.
Obviously, something inside the MX4000 is mucking things up...

Mike

 

[zinophile]

@mpaschetto: I will definitely let you know if I ever find anything out. Did you need to use a headphone amp to hear the output from the MDA4000 through your phones?

It does sound like there is something up with the output stage of your MX4000. You sure that the RCAs that you are using are good?

 

[mpaschetto]

Yep, I verified that my interconnects are good.

I don't think the signal from the MDA4000 is powerful enough to drive headphones directly....but I can't say for sure.

I also fed a signal into the AUX inputs via the CD player and preamp from my home stereo.
The same distortion was present through the AUX input.
I think it's safe to say the problem with my system is somewhere in the head unit itself.

 

[mpaschetto]

I'm not sure the output from the MDA4000 is powerful enough to drive headphones directly...but I didn't try it.

Yep, I verified that my interconnects are good.

I used the CD player and preamp from my home system to apply a signal to the AUX inputs on the head unit.
The same distortion was present through the AUX inputs, so my issue is definitely in the head unit...