WQXR has to have some of the sweetest audio I've ever heard. Of course, music sounds great, but even the "jock" mics are so clean and the highs come thru with brilliance. I know they run Harris Digit transmitters. Does anyone know what kind of audio processing and studio mics they use?
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WQXR AUDIO CHAIN
- Thread starter VeteranPD
- Start date
I know back in the late 80's they had the Aphex "Audiophile" system (compellor, dominator and I believe their matching stereo generator). This was back when I was actively involved with the NYC Chapter of the SBE. I'm sure they've probably have gone digital by now, but they still are one of the best sounding stations I've ever heard.
You can catch a very small glimpse of WQXR's current processor in these photos:
http://www.necrat.com/wqxr_pro.html
The Aphex audio chain remains as a backup (with a CRL stereo generator!).
http://www.necrat.com/wqxr_pro.html
The Aphex audio chain remains as a backup (with a CRL stereo generator!).
R
Radioman100
Guest
R. Fry said:
You'd be amazed how many people use the Digit with the optional analog composite input module, or running analog composite into the digital input module in "emergency backup" mode.
You can't run a composite clipper without a composite signal. A classical station like WQXR probably doesn't, but a lot of people do.
R. Fry said:
The built-in stereo gen fed with AES-3 sounds good in theory, but I've found that the DIGIT's optional analog input module, fed with a good quality external stereo gen, sounds noticeably sweeter in practice.
I built a new transmitter facility three years ago and had the budget to install two "alternate main" Harris Z-series transmitters. As an experiment, I ordered one of the DIGIT exciters with the digital input module and the other with analog. Both were fed with the same processor (Omnia 6 FM) so I used the "FM" AES output to feed the digital input on Transmitter A, with one of the composite outputs of the Omnia stereo gen feeding the analog module on Transmitter B. Every few days, I switched transmitters and asked my staff to listen critically and try to detect a difference.
First, we observed modulation overshoots ranging from 15 to 20% on the "digital" DIGIT. If the drive was reduced to keep these within FCC limits, there was an slight reduction in loudness. We also agreed that the audio quality on the digital interface just wasn't as natural-sounding as on the analog. I decided to return the digital input module that had been shipped with Transmitter A and exchanged it for the analog. Harris kindly agreed to do this at no charge.
Incidentally, there is a minor disadvantage to using the SCA input on the digital module for composite stereo; the resolution of the A to D converter is not as good as in the analog input module.
Most engineers I know who have had experience with this exciter have drawn similar conclusions.
Based on the photos, my guess is that WQXR ordered their DIGIT with the analog input module and feeds it a composite signal from the Aphex stereo gen.
I, for one, am surprised that WQXR would have a pair of Aural Exciters and a Studio Dominator in the rack. They must've been using these very lightly, if at all, because they never sounded too loud or too bright for a Classical station.
Kevin Tekel said:
Ahhh but the important secret remains. What SETTINGS did Rodney use?
;DPlay Freebird said:
Probably due to the high frequency content of the program audio. The DSP stereo generator in the DIGIT has very tight modulation control as long as the AES-3 input is spectrum-limited to about 16 kHz.
People who liked the characteristic sound and loudness possible with analog composite clipping did prefer the analog input module, understood.
[Disclosure: I was the Harris FM product line applications engineer when the DIGIT was introduced (retired in 1999)]
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Yep, so do I ;DSgeirk said:
M
menotti1
Guest
Can't fool me, i saw that DSP_X,too.Tweaked right the box is awesome.i doubt they are using most of that other gear.Just using rack space.
R. Fry said:
Have you looked at the DSP stereo encoder of an Omnia 6 or Optimod 8500?
IMHO, Harris Digit AES module= One of the worst designs ever by Harris. The early plastic boxes had RFI problems. All versions have overshoot problems caused by the 32 kHz sample rate. The wide-band chip (low pass filter?) later introduced was a band-aid. While it improved overshoots, the chip also introduced junk to the SCA region. Harris should have listened to Frank Foti when he proposed a digital composite interface. I always loved most Harris transmitters and used to often say, "Please stick to making transmitters." "Leave the processing and stereo generator design up to the pros." I lost faith in Harris when they refused to admit the Wilkinson combiner problem in many SS IPA's. An old solder technician in Quincy told me about it. You couldn't see it without a large magnifying glass. I guess it was a third-party vendor problem. Why did they continue to use it then? Rant mode off.
Anything digital with a maximum sampling rate of 32 kHz is junk. This isn't 1995, folks... get with the times!
fm-engineer said:
Overshoot did not occur at any sample rate from 32 kHz to 56 kHz if/when the incoming AES-3 audio from the station's audio processor was properly bandwidth-limited (~16 kHz). There were (are?) hundreds of DIGIT/Orban 8200 combos with punchy, overshoot-free modulation performance using the DSP stereo generator in the DIGIT.
Standard digital sample rates greater than 32 kHz and the spectrum above 16 kHz that they can convey aren't of much use in generating an FCC-compliant, FM stereo waveform -- which doesn't permit program modulation in the region of the 19 kHz pilot. Passing spectrum above 16 kHz also complicate the performance of audio processors because of the higher value of analog FM pre-emphasis in that region of the audio spectrum.
Besides which, few adults or even teens these days can hear much above 16 kHz, even in a well-controlled listening environment.
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R. Fry said:
History has shown that digital FM exciters moved away from 16kHz low pass filtering, for the reasons of overshoot.
Consider the following scenario, that did happen quite a bit, when the DIGIT exciter was introduced. There were many stations that did not have a DSP based processor. They were still using older analog boxes. There isn't a single analog processor out there that offered band limited audio, where all content was removed at 16kHz. The nature of the 15kHz low pass filter is such, that it began to rolloff at 15kHz, but contained energy - along the filter's slope - out to around 18kHz. It's not feasible to create an analog LPF that has a cutoff freq @15kHz and brick wall remove everything @ 16kHz. It possible in theory, but not probable nor practical in reality. This is an area were DSP shines.
I'm explaining this, as any of those analog processors would have been connected to the DIGIT via a good quality A/D unit, and with the sampling rate set to 32kHz, guess what happened? If you answered "overshoot", then pick a prize from the Harris transmitter guy!
The overshoots occurred because the signal content that existed in the 15kHz -> 18kHz domain, would overshoot in the 16kHz LPF in the DIGIT. I proved this in our lab. BTW: I used an 8100 for the test, and it had overshoots!This disproves his comment about FM audio spectrum needing to be tightly band limited to 16kHz, as there has always been 'some' signal content in the 15kHz -> 18kHz domain. This is the nature of how the analog low pass filters work, and they never negatively affected FM stereo transmission prior to a digital exciter. That dates back to the mid 1970's when it was discovered how to eliminate overshoots in 15kHz low pass filters.
Designing the DIGIT with the tight low pass filtering it employed, was WRONG!! I know why they did it, because the 8200, was the only DSP box, at the time, and it supported 32kHz sampling. At that time DSP MIPS were very expensive, and I'm sure that Orban and Harris were trying to conserve on costs. We never bought into that, as having the ultimate broadcast DSP guru around...Steve Church...we were able to conserve cost, yet employ higher sampling.
I must laugh, as it's been over 10 years since this goofy debate about FM stereo L/R audio sampling occurred, and the Harris folks *STILL* are pontificating propaganda that was wrong then, and it makes them look foolish now!
Another historical note: Harris later worked directly with me to improve the situation by letting out the low pass filter's corner frequency somewhat, but it never truly fixed the problem.
M
menotti1
Guest
As Paul Harvey would say AND NOW YOU KNOW THE REST OF THE STORY.I had one station with all Harris gear.It only took ONE..The digit exciter sucked...
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