Defeating excess noise before compressor

[i624095]

I am in the process of updating a studio and have just put in an Optimod 8400, which I am in love with. I guess the problem is that there is nothing inbetween the board and the transmitter (with the exception of 5,000 ft of cable). I have heard the many stations use compressors on the audio before the actual compressor. Would a simple noise gate be the trick to defeat excess hiss being put out by the automation system and when using the phone interface. There's no hum, just hiss. I am not the greatest Optimod tweaker, but I think the noise floor at those times is actually higher than what an Optimod could filter? Thanks In Adavance...

 

[SamBuca]

> There's no hum, just hiss. I am not the greatest Optimod
> tweaker, but I think the noise floor at those times is
> actually higher than what an Optimod could filter? Thanks In
> Adavance...

You need to find from where the noise originates. If your board is producing a hiss with nothing potted up then troubleshoot the board...no sense in pulling your hair out over a dead cap. Also check the audio right off the line at the transmitter and see if the hiss is introduced between you and the transmitter or somewhere in the audio chain at the transmitter site. If you're using a local loop, call up the bell and have them troubleshoot the line....we just had a problem with low voltage on one of our circuits.

Regardless, put an AGC local to the equipment chain and defeat the AGC on the optimod or at least make it less aggressive. Your s/n ratio probably sucks if you're sending uncompressed audio over the line.<P ID="signature">______________
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[RadioDoc]

> I am in the process of updating a studio and have just put
> in an Optimod 8400, which I am in love with. I guess the
> problem is that there is nothing inbetween the board and the
> transmitter (with the exception of 5,000 ft of cable). I
> have heard the many stations use compressors on the audio
> before the actual compressor. Would a simple noise gate be
> the trick to defeat excess hiss being put out by the
> automation system and when using the phone interface.
> There's no hum, just hiss. I am not the greatest Optimod
> tweaker, but I think the noise floor at those times is
> actually higher than what an Optimod could filter? Thanks In
> Adavance...
>

My thought is that an AGC on the front end of the cable would make the hiss even worse. What you need to do is find out where the hiss is coming from. "White Noise" hiss is generally a signal-to-noise problem caused by too little drive from the output of a device.

In the case of your automation equipment, make sure you have the output turned up to a reasonable level. If you have to crank on the inputs of the devices after the automation, then the level is too low.

You should not have to have anything on the head-end of that cable run. I've done farther without many problems, other than maybe a bit of attenuation on the high end.

Something to think about...Lucent makes some inexpensive media converters that will take the input on the head-end and convert it to AES/EBU. You can then feed the other end directly into the digital input of the 8400. I don't remember those costing more than a couple hundred dollars.

Anyway, the prudent thing to do is see where the hiss is and work BACKWARDS! Otherwise, you're just masking a real problem.

My $.02...<P ID="signature">______________
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