robot sounding spdif problem

[thedude400]

I'm having a problem lately with using my lexicon processor with my interface. I have had it working properly before but now when I set up the spdif connections i hear this metallic sounding robot-esque sibilince sound. I faintly hear the effect but the robot noise is so overpowering, using my processor in 24 bit/48khz with my interface has become pointless. I know using a normal rca cable isnt recommended but should still work. I doubt that is the problem though I suppose it could be.

I have the clock set to external and everything , I have switched the cords around and messed with the input levels etc. I made sure the bit rate and khz's all match up .I just don't know what to blame or what is causing this problem. I know getting actual spdif cables could be a step in the right direction but is that gonna solve this problem. Anyone able to help me out with this problem?

[bigwillz24]

Only one way to find out... buy a cable. Seems like you've done all the troubleshooting. But if you had it working perfecty before I'm guessing it has something to do with something you changed.

[gtrman_66]

A normal RCA cable and a coaxial digital cable are definately not the same thing. The spdif cable has a 75 ohm resistance whereas the audio cable is just straight "zero" resistance cable. I found out the hard way about using straight RCA cable when my spidif coaxial on one of my audio cards quit working after while.

I have some 75 ohm high quality video composite cable with RCA connectors I have been using with no problem on coaxial spdif connections. As far as I know, there isn't a whole lot of difference between the two.

[SRR]

What lexicon and what interface are you using?

[MOFO Pro]

I doubt the cable can be giving you that much of a problem... unless it's defective (you may want to try a different RCA cable... and if you're going to cheap out on a cable at least make it an RCA video cable, an audio cable's impedance is way off).

Sounds more like clock settings... like both devices are set as external/slave or internal/Master... it really sounds like a frequency mismatch... but you say you've checked and they agree... Do you have a feedback loop set up by mistake? Digital feedback can sound very robotic when it starts clipping. Does it occur with no audio source? Does it gradually build up as you add gain to the source... or does it pop up quickly at a certain gain level?

I doubt it's the cable... but you haven't given us alot to work with... what's the interface?

Edit: Obviously I got called away halfway through this one... answering this question for the third time

[bigwillz24]

Did he bail? I'm kinda curious as to the interface.

[SRR]

Originally Posted by gtrman_66

A normal RCA cable and a coaxial digital cable are definately not the same thing. The spdif cable has a 75 ohm resistance whereas the audio cable is just straight "zero" resistance cable. I found out the hard way about using straight RCA cable when my spidif coaxial on one of my audio cards quit working after while.

I have some 75 ohm high quality video composite cable with RCA connectors I have been using with no problem on coaxial spdif connections. As far as I know, there isn't a whole lot of difference between the two.

Sorry you have been misled, a metal coat hanger will work for passing spdif signals. However using a good quality shielded cable with RCA connectors might be better then a coat hanger in the long run. There is no such thing as a "digital" or "SPDIF" cable, as there was never a "CD ready speaker", remember that marketing slogan from the 80's anybody? You can use any coax wire for SPDIF connections, nothing will blow up if you use something labeled video, audio, digital audio, or any another label they want to put on the cable. Your audio card certainly did not stop working cause the cable you were using was labeled one way or another.

[SonicAlbert]

It sounds to me like you might have your audio double routed through your SPDIF interface. In other words, the audio signal is going through it the first time, and then is somehow routed around and going through it again a second a split second later. This could cause the type of sound you describe, or something like it.

I suggest you take a close look at all your audio pathways, both in hardware and software.

[thedude400]

it's an mpx 500 and an aardvark q10. Could be the Aardvark but I really doubt it. Aardvark might be no longer in business for strange and undisclosed reasons but the q10 has been very solid for me thus far. I've been using one on and off for just under 2 years. The cable I'm using is just a radio shack cable.

The one thing I did change recently was a hard drive reformat which isn't anything that would affect processor /interface compatibility. I will have to really take a closeup look at my signal chain . I'm basically positive everything's set up correctly but who knows maybe it is just a silly mistake. I have a guy coming in to finish up a 5 song demo tomorrow morning and we have been anxious to use the lexi so hopefully I can troubleshoot successfully by then. I will post my resolution if I ever get one.

[SonicAlbert]

Particularly check the audio routing in software, as it can be really easy to double the signal somewhere along the line. If you are somehow monitoring signal from two different points in the path then you could get that sound.

I thought Aardvark made excellent products, it's too bad they disappeared. You could see it coming though. At the NAMM show their booth basically got deserted the last couple years. You'd see one or two lonely guys standing there but no one stopping in to check their gear. Somehow they lost the buzz and people went elsewhere.

[RezN8]

Not sure if this was what you were saying earlier about setting the clock to external, but with some products, the "SPDIF device" has to be chosen as the clock source. For instance, a few years ago when tracking with the Yamaha DG Stomp SPDIF through a Delta 1010, we had to set SPDIF as the masterclock in the Delta 1010 control panel.

Does the Aardvark have an option for this, or is external the only option?

I have used the Lexicon MX with SPDIF too, and I think I remember something about a setting in the Lexicon to set to digial out vs. analog. Don't quote me on that, but it's worth looking into as well.

Hope this info helps! Cheers, Rez

[SonicAlbert]

Another possibility is that you have your Lexicon set to pass both the dry signal and the wet signal. If you have the unit set to less than 100% wet this could also cause a sound which is possibly the one you are describing. There would be a slight delay between the two.

[MCI2424]

Originally Posted by SonicAlbert

Another possibility is that you have your Lexicon set to pass both the dry signal and the wet signal. If you have the unit set to less than 100% wet this could also cause a sound which is possibly the one you are describing. There would be a slight delay between the two.

It would also cause phasing (like a flanger type of sound)

I guess it could sound "robotic"

[SonicAlbert]

Right, that's what I think he is describing. Not quite a phasing or flanging sound, but a doubled signal that is just a few milliseconds apart.

[Robert D]

Originally Posted by SRR

Sorry you have been misled, a metal coat hanger will work for passing spdif signals. However using a good quality shielded cable with RCA connectors might be better then a coat hanger in the long run. There is no such thing as a "digital" or "SPDIF" cable...........

Reflections and sloppy edges from poor digital transmission line impedance control are real, and easily demonstrated. Any 75 ohm cable is fine for S/PDIF, you don't need anything exotic, but use 75 ohm cable.

[RAK]

Originally Posted by SRR

Sorry you have been misled, a metal coat hanger will work for passing spdif signals. However using a good quality shielded cable with RCA connectors might be better then a coat hanger in the long run. There is no such thing as a "digital" or "SPDIF" cable, as there was never a "CD ready speaker", remember that marketing slogan from the 80's anybody? You can use any coax wire for SPDIF connections, nothing will blow up if you use something labeled video, audio, digital audio, or any another label they want to put on the cable. Your audio card certainly did not stop working cause the cable you were using was labeled one way or another.

Yeah, what he said.

While it is recommended that for S/PDif or "Coaxial" connections you use an RCA cable rated at 75 Ohms, it's stil an RCA cable. Just like how the XLR cable you use between your microphone and your mixer for an analog connection, is the same XLR cable you use for a digital AES/EBU connection.

[mixsit]

I know the clock and data connections are pretty lenient in that respect but where or at what point does that spec apply then? Presumably it's just a set amount of capacitance for 75 ohms at some radio frequency right?