[SBE] audio problem

[Phil Alexander]

There are several possibilities. However, if the sound is good at the
studio it would be good to look at the audio chain beginning there.

	1. What additional (if any) audio processing is used following
       the console before the STL (if any).

	2. If used, what is the STL audio transport means? Are codecs 
       involved?

	3. What is the limiting processor immediately before the Tx?

If would also be interesting to check the audio phasing off-air
versus phasing at the console output. This is easily done using
a scope with X-Y inputs and observing the output of the console
and the output of the modulation monitor. The cause of deviation
from a straight diagonal line should be investigated.

If I had to guess, I'd be looking at phase reversal first, primary 
(over)processing at the Tx on a multi-band processor second, codec 
artifacts third and phase non-linearity fourth.

---------------------------------------------
Phil Alexander, CSRE, AMD
Broadcast Engineering Services and Technology 
(a Div. of Advanced Parts Corporation) 
Ph. (317) 335-2065   FAX (317) 335-9037





> -----Original Message-----

> From: Michael Holmes [mailto:admaker at ntelos.net] 

> Sent: Tuesday, August 21, 2007 6:55 PM

> To: mclappe at sbe.org

> Subject: Request re signal processor difficulty

> 

> Sirs:

> 

>             I am a radio commercial producer of 30 years experience. 

> 

>             I have a signal processor called an SPL (Sound Performance

> Laboratory, Germany) Vitalizer.  It enhances audio signals with a

> combination of dynamic EQ, amplitude-controlled phase correction and

> harmonic filtering.  The result is greatly enhanced transparency.

> 

>             This device is used in recording studios, post-production

> facilities, and live sound reinforcement.  It is advertised for these

> purposes plus as an enhancing device in broadcast facility audio chains.  

> 

>             For some reason, it distorts my commercials on the air, and has

> since I began using it.  I hear no distortion whatsoever in my studio.   I

> use its effect sparingly.  I'm not overdriving anything, and people at the

> stations say that my MP3's sound wonderful in their monitors (internal, not

> off-air monitors, which exhibit the distortion to them as well).  The

> company that manufactures this device is well-respected worldwide and has a

> good-sized range of audio products:  

> 

>            SPL Home:      http://spl-usa.com/index.html

> 

>            Vitalizer page:  http://spl-usa.com/V_MK2/in_short.html

> 

>             If it is possible, I would like to put this problem before your

> membership in the hope that someone has had experience with this device and

> can offer insight or solution to this difficulty. 

> 

>             I think it important to note that only someone familiar with

> this device will be able to address the issue.  Again, my levels are good,

> and are identical with or without the device in the chain.  With the device

> I get on-air distortion.  Without I don't.  To the best of my knowledge

> there are no other variables or differences.   The stations report that

> in-house everything sounds fine.  

> 

>             Thanks very much!

> 

> Michael Holmes

> 

> admaker at ntelos.net