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I'm trying to set up a hold music system for my company. Right now we just have an old FM radio with a headphone jack tuned into some local radio station. We would like to move to something more controlled than that, however.

I thought this was a simple thing. Our server has audio out so I figured I'd just rip some CD to it and set up a daemon to keep the music looping. I did this, but the problem here is that the music is inaudible through the hold system. If you listen closely you can maybe kinda hear it playing but not really, at most you get faint bursts of static that resemble the beat of the music.

I thought maybe there was something wrong with my music playing system, so I got my MP3 player and phone and tried them both, but it's the exact same thing. I figured maybe there was some sort of bitrate threshold that the phone system had or something, so I re-ripped the CD at 64kbps and tried that again, but to no avail. Same thing as before.

So far the only thing that is audible through the phone system is our FM radio. Can someone explain why? The only thing I can think of is that it's perhaps an analog/digital thing but I thought the standard headphone-out audio on a computer was analog in the first place?

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The standard headphone-out on a computer is analog, so at that point the bitrate of the music is irrelevant. Question: did you use line out or headphone jack and did you adjust the volume from the computer? –  user17642 Sep 21 '09 at 16:54
@emgee - I've tried both line-out and headphone-out. I've also tried setting the volume to max, medium, and low levels, but every situation produces the same result. –  DWilliams Sep 21 '09 at 17:04
Could you provide more details about the hardware and software? –  tomjedrz Sep 21 '09 at 17:43
Have you tried connecting an MP3 player, walkman, or some other device to the phone system other then the FM radio? It would be nice rule out the sound card on the computer as the issue. –  Zoredache Sep 21 '09 at 19:32

3 Answers 3

up vote 2 down vote accepted

It's nothing to do with the digital aspects of the source material on your computer, because (as someone else pointed out) it is an analog signal once it comes out of your sound card.

Here are some possible reasons:

  • Perhaps there is an electrical problem and there is a potential between the grounds of the two devices. This could cause a 60Hz hum which might confuse the phone system when it re-digitizes the music.
  • The phone system is likely wanting a mono signal (a 1/8 phono jack with a single black band) but your sound card and MP3 player probably have a stereo out (a jack with two black bands). When you plug one into the other, the signals mix electrically with varying results. Try getting a cable that splits the stereo signal into two mono signals, and just use one of them.
  • Maybe the level is wrong. You said you tried several volumes, but it really is a likely culprit so maybe try again. Does your phone system specify what level the signal should be at?
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I think you hit on the problem here with your second point.I checked the number of bands, and the one coming out of the KSU had one band, indicating that it is indeed mono. I was using an audio extension cable without even thinking about it, and it has two bands. So, I assume if I buy a mono audio extension cable then that will do the trick since it will just pick up on one of the stereo bands? –  DWilliams Sep 21 '09 at 17:48
Actually upon rethinking that, buying a mono extension cable would just be the exact same setup I have right now and wouldn't work either. Do you have any idea where I could get a cable that splits the stereo signal as mentioned? –  DWilliams Sep 21 '09 at 17:56
You could make one by purchasing a stereo 1/8" jack, and a mono 1/8" jack. Wire it up to ignore one of the channels on the stereo jack. If you don't want to get messy with solder, find a splitter that goes from stereo 1/8" to 2 RCA jacks (they're really common). Then get an adapter that goes from RCA to mono 1/8". BTW, you might be able to test this theory first by unplugging the cable very slightly. Depending on how those black bands line up, you might get different results through the phone system. –  lukecyca Sep 21 '09 at 18:23
@lukecyca, the when connecting a mono cable into a stereo source, the signals should not mix. The ring and sleeve contacts would be shorted basically removing the right channel. If the computer isn't providing any output on the left channel, this may be a problem. –  Zoredache Sep 21 '09 at 19:39

To be honest, you should look for royaltey free MOH, as playing the radio or commercial CD's (or copies of CD's) is illegal as it violates copyright law.




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I'll look into that. I'm not the type of person who pays attention to licenses and such (copyleft/FOSS is the future IMO) so it would be nice to not have to worry about it. Unfortunately this doesn't solve my problem. Music won't play through my system, copyrighted or not. –  DWilliams Sep 21 '09 at 16:48
Sorry. I realize my answer didn't answer your question. Have you tried hooking up an external CD player? –  joeqwerty Sep 21 '09 at 16:53
IIRC: In Canada, SOCAN provides a blanket license for businesses that play music in their stores or on-hold, and it's quite reasonably priced. It was $100/year for a non-profit where I set something up a few years ago. ASCAP, BMI, and the other US counterparts probably have something similar. Throw them a bone... their primary business model is falling apart. –  lukecyca Sep 21 '09 at 18:29

As noted by a couple of other posters, the input jack is analog not digital, so the sampling rate and encoding characteristics have no meaning in that context. If the system is getting MOH from data files on the system then the encoding specifics will likely matter.

Even if the hardware has a sound card and analog input, the telephone system may not be capable of accepting the input and using it as MOH. One VoIP system I am familiar with is not programmed to use analog input.

Even if the system can use the analog input for MoH, it is not likely the default, so it may well need configured to do so.

Good luck .. hope this helps. If you provide more info about the specifics of the system and I can help more I will edit.

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