Computer Fails as Audio Source for 8x24 MOH 1

[peterlargen]

Has anyone solved this before?

I dropped an old Pentium in my closet next to the 8x24 to be a music server for music on hold, replacing a Denon receiver. When I connected the PC to the MOH inputs, I received no sound.

I tested the output of the PC through headphones and through the Denon receiver. No problems there.

I re-connected the output of the Denon receiver to the 8x24 with the PC output coming in a tape input - again no sound.

However, if I disconnected the output of the PC from the Denon receiver, I got MOH (from another source, obviously). So it must be a ground problem...

I grabbed a laptop and connected it... same problem... running on batteries!

I got a suggestion on rec.audio.tech that I needed an audio isolation transformer.

Anyone run into this before? Have the solution?

Thanks!

 

[Arr]

Peter,
The input source must be 600ohm impedance. If your PC card isn't this you will need the matching transformer. Also of note: where micro headphones are used from a source there isn't enough output power even at 600ohms to provide MOH with the proper volumes.
I just had a customer's new 3X8 damaged by a sound source that was set way too loud. Ended up with really bad MOH cross talk on all phones.

Cheers
PhM

 

[peterlargen]

Thanks.

I found a nice description of the pros/cons of different types of isolation transformers. I'll build one, put it on, and let you know how it sounds.

http://www.blueguitar.org/new/articles/other/ground_loop.pdf

 

[peterlargen]

A 1:1 600 ohm isolation transformer solved my problems. I used inexpensive parts from The Shack, since this is only telephone-quality audio.

 

[Arr]

Peter,
Thanks for all the update replies. We all REALLY appreciate them. Too few do this. Thanks again.

Cheers
PhM

 

[peterlargen]

And for those of you doing this at home who'd like more details...

There wasn't enough power from the sound card to provide good quality audio. Too much background hiss when you boost the volumes at the phones. I dropped in a 30-watt preamp with a built-in parametric EQ, and now things sound great!

I created an .m3u playlist of the music and put a link to it in the startup group. I associated .m3u to Windows Media Player (I was using WinAmp but had some lockup problems after running for several hours). I set the enhancement to crossfade the songs at 5 seconds and turned on repeat. Now, whenever there is a restart, MOH restarts on its own. And I can change the music at any time remotely by just connecting to the network and copying in a new .m3u.

If I want to get fancy, I'll pre-build playlists for various holidays and use task scheduler to replace the playlist at specified times.

I put a PowerWare 5115 in the rack and have one load segment for the computer and one for the phone system. When power goes out, the computer does a graceful shutdown and turns off its own load segment, leaving all of the backup power to run the phone system. Now the phone system is live even when the power is out for long periods of time. When power comes back on, the computer is set to start on regaining power, and the music is back.

So, other than no MOH during power outages, I'm happy with this setup.

 

[MarvO1]

Peter, I'm doing almost the same thing. I am running an old slow 486 (headless)no monitor, no keyboard. I use VNC to control it remotely over my LAN. The only thing on it is my music source and an SMDR connection for my Call Detail Recording. I am using MusicMatch Jukebox for my sound control. I never thought about using the fade in and out. Nice idea.

MarvO said it