Digital Audio Chain

Brian Bowers said:

I believe I'm correct in stating that only one provider of pre-emphasis should be turned on, yes? In other words, if I have 75us of pre-emphasis turned on, on the exciter, the audio processor's pre-emphasis should be turned off, and vice versa. That's correct, right?

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I'm not getting into the obvious discussion of GIGO (Garbage In/Garbage Out) - but on pre-emphasis, if we were told during initial configuration to turn it on, we did - you can change it in either the transmitter or exciter configuration menu (depending on exactly which models we're dealing with) to 0, 25, 50 or 75usec. If you're pre-emphasizing somewhere else, definitely you'd want it set to 0.

Pretty much everything we've built in the past 10 years is as acoustically transparent as you can get - THD+N in fractions of a percentage point and response curves within 0.05dB, so the exciter/transmitter shouldn't make any change to the sound. One thing I do see with AES/EBU a lot is folks tend to overdrive it... and you can't go any further with a digital signal than all 1s, so it can fall apart pretty quickly if that's the situation - in that case, you'd be best off feeding analog audio, where you can compress the daylights out of it without hitting the digital ceiling (whether it sounds good or not is another discussion, but that's subjective!).

If you can shoot back with model number of the transmitter, I can give more detailed instruction on checking pre-emphasis and general audio settings (we do have in later models a two slope limiter/AGC that can pump like a sonuvagun if you overdrive it - I highly recommend it be turned off, unless absolutely necessary).

Thanks for joining in Jeff. Can you answer me this - If I'm using the composite (BNC) input on the Nautel 3.5 (as of this writing, I'm forgetting if it is the NVLT, or GV model) exciter, does that signal go through any type of A-D (and possibly D-A) conversion? I'm pretty sure that what I'm hearing is basic audio degradation from digital losses, as the analog audio (which contains various grade levels of audio files) goes through various equipment (PPM encoder, Voltair, and profanity delay). I know that the Voltair is doing the worst amount of damage, as the minute I bypass it, some of my high frequencies are restored. This degradation is more noticeable on music files, as compared to commercials. It's *most* noticeable on new music files, as compared to older songs. Again, I'm trying to get this information through the PD's head, who downloads most of the new music, for this station I'm referring to. I'm pretty sure that he's not starting out with the highest quality soundfiles to begin with. IMO, our webstream audio sounds better than our OTA audio, since it only passes through one PPM encoder, and that's all (no Voltair, no profanity delay, and no transmitter exciter either).