8100/XT

[cgould]

And as we know the early dsp boxes were not even as good as the 8100a/xt2!
Sitting next the my 8100a/xt2 is the 8200!

The trouble is,i can get my modified 8100a/xt2 louder than the 8200,for the same perceived distortion on midrange :

I would expect the 8200 to be cleaner on mpx spectrum though,but the midrange stays more forward on the 8100a/xt2,probably due the 6 band limiters,whilst the 8200's band 3 has a wide frequency range!

Also another simple but very effective design.............the 222a,say no more!

LOL!

I agree here too! I wasn't too impressed with the 8200. My modded 8100 / XT2 was louder, and sounded better. -But to be fair, it was the best of the DSP boxes at the time.

DSP audio processing was in its infancy back then!

The competing DSP designs of that time period died a quick death. Probably among biggest ones back then was that Paragon thing...then there was the Gentner Lazer, in which Gentner tried to take Glen Clark's multiband analog limiter companion to the Prism, which was under development when he sold Texar, and do it in DSP.

Again, the tech was too rough and so the results were..ahem..less than stellar.

The 8200 killed all of those REAL fast.

-C

 

[BROADCAST]

I found the aes/ebu input on the 8200 to be very useful,the lack of noise floor direct from a cd player was suprising!

Regarding my 8100a/1 psu mods,have a look at http://www.maximod.com/optimod/

 

[skippertthomas]

...Any longing for the days of a DAP on your good ol' AM five killowatter?????

 

[RadioMan203]

...Any longing for the days of a DAP on your good ol' AM five killowatter?????

I remember visiting an AM during the 70's that had a DAP on-air and was simply amazed that the mod monitor looked like it had DC on the meter - it was at 100% with hardly any noticeable wavering ... except when the jock spoke!

 

[wgliradio]

The trouble is,i can get my modified 8100a/xt2 louder than the 8200,for the same perceived distortion on midrange :

A properly designed airchain with an 8100a/XT2 or even an 8100 with a trick or too can sound better than an 8200, and a few others in the same family. I love the sound of mine, there is just something about it that has not been duplicated properly in other Orban boxes. Goran Thomas talked about it earlier in this thread IIRC. But this is great nonetheless.

 

[rorban]

It is truely is a classic design, and an amazing feat by Orban no doubt about that! I wish I could be a fly on the wall when all those "aha" ideas were popping into his head...
-Cornelius

I spent a full year tuning the 8100 if you count the time spent on experimenting with approaches that didn't pan out. On the other hand, the idea of distortion-cancelled clipping was one of those "eureka!" moments, although it occurred when I was designing the 9000 and was struggling to get rid of sibilance distortion caused by difference-frequency IM.

The original 9000 design used an analog BBD as a delay line for the distortion cancelling clipper. I will never forget the experience of first turning on the distortion cancellation sidechain and hearing the sibilance distortion just plain vanish.

A later "eureka" moment came when I realized that I could instead use the system lowpass filter as a delay line when compensating for the group delay of the distortion cancellation lowpass filter. That opened the door to a much higher quality audio path and led to the 8100's clipper. Of course, the actual implementation required matching the magnitude and group delays of the two parallel filters to a very close tolerance. Otherwise, the depth of the distortion cancellation would not be satisfactory. This required fun with Chebychev polynomials and the like. (Edison said something about "99% perspiration."

 

[Sgeirk]

The above post is one of the coolest posts I've seen on here, perhaps ever.

 

[wgliradio]

That was nice The moment when the distortion disappeared must have been like harps playing.

 

[skippertthomas]

Great insight to the legend in the shop... I can see a shining light blasting into the lab room and a flock of Angels singing the Hallaluah Chorus... Must have been a lifetime moment...

 

[FredRichards]

I remember visiting an AM during the 70's that had a DAP on-air and was simply amazed that the mod monitor looked like it had DC on the meter - it was at 100% with hardly any noticeable wavering ... except when the jock spoke!

One of the stations I worked at had (2) DAP 310s running in parallel, one with stock setup, and another with the expansion time constant changed so it would punch in the -15 to 0 dB area. Along with the clipper in the DAP, the MW-1A had a "mod enhancer" (buzz box) that was set to another 1 dB of clip.

Like you say, the positive wiggles between 115-124% and negatives between 90-97%. And the obvious, "what dynamic range??"

Thats the way corporate liked it.

 

[RadioMan203]

One of the stations I worked at had (2) DAP 310s running in parallel, one with stock setup, and another with the expansion time constant changed so it would punch in the -15 to 0 dB area. Along with the clipper in the DAP, the MW-1A had a "mod enhancer" (buzz box) that was set to another 1 dB of clip.

Like you say, the positive wiggles between 115-124% and negatives between 90-97%. And the obvious, "what dynamic range??"

Thats the way corporate liked it.

Depending on the timeframe, that was what AM radio was all about. Balls to the wall and loud and proud! I remember the Westport AM I worked at had an MW-1 that I had really singing with an Optimod 8000a feeding the composite STL, feeding a CRL final limiter into the Kahn AM stereo box (yes, this was mid-80's). It was great, with the only problem trying to get the post-sunset box to match with the same audio depth (9 watts with an LPB TX-20). I finally got the LPB to become a mirror image, audio wise, by using the MW-1's modulation enhancer box on the LPB's audio chain. You'd hear the power switch but the audio was just as dense.

 

[skippertthomas]

When I get a stand alone AM, I'll pay Bill good money to set up that 'classic AM' chain.....

 

[BobOnTheJob]

When I get a stand alone AM, I'll pay Bill good money to set up that 'classic AM' chain.....

It'll be close, but with the NRSC mask, sadly, AM will never sound quite like it did 25 years ago. For starters, using the clipper in the MW1A is no longer legal as it generates audio products beyond 10khz. Although with the help of the Omnia 5EX HD+AM, analog AM can still sound mighty fine...

 

[RadioMan203]

It'll be close, but with the NRSC mask, sadly, AM will never sound quite like it did 25 years ago. For starters, using the clipper in the MW1A is no longer legal as it generates audio products beyond 10khz. Although with the help of the Omnia 5EX HD+AM, analog AM can still sound mighty fine...

Remember, I didn't use the Modulation Enhancer clipper on the MW-1 (mine wasn't an "A", but the station a fellow engineer worked at in Stamford had the "A" version - not sure of the difference) but I used it on the little LPB running 9 watts of post-sunset power. I was able to pick it up 15 miles away loud and clear with a nice kick.

Bob is right on the money about AM never sounding as good as it had. I've noticed such a difference of main channel analog audio with all the stations running AM-IBOC. Lack of bass is the thing I've noticed most.

A good processor will certainly make AM analog sound good, but with the NRSC bandwidth restrictions it will never be the same. I'm actaually going to be experimenting with one of the Hamilton Part 15 AM transmitters and I picked up a mod enhancer box - I haven't hooked it up yet, but I hope to get a copy of the schematic in case it needs help. There's a whopping 2 electrolytics that I'll probably replace just for the fact they have to be at least 30 years old.

 

[Parasound]

Glen clark used to make the rcf1 card,then the rcf2,then the cobalt blue neural network card,to go in the 8100a as card 5,all that finished when he sold the rights to gentner with the prisms.
I believe it used fuzzy logic in that blue epoxy block,i found it way too aggressive!
Also it ran very hot,I sold mine on ebay a while ago as i could not live with it.

"Cobalt Blue" came after the sale of Texar to Gentner.

-Frank Foti

Cobalt blue was a GlarkCom product, not a Texar or Gentner.
I think Glen still uses the name GlarkCom.
But for the RCF-2. It was made by Gentner, after introduction of the PrismII FM
They opened the design of the modules wich are on the RCF-1. They also opened the design of the Phase rotator.
They thought that the production of the modules, took too much time

 

[kevtronics]

I remember the Westport AM I worked at had an MW-1 that I had really singing with an Optimod 8000a feeding the composite STL, feeding a CRL final limiter into the Kahn AM stereo box (yes, this was mid-80's). It was great, with the only problem trying to get the post-sunset box to match with the same audio depth (9 watts with an LPB TX-20). I finally got the LPB to become a mirror image, audio wise, by using the MW-1's modulation enhancer box on the LPB's audio chain. You'd hear the power switch but the audio was just as dense.

Was that the audio processing responsible for "The AM Stereo Challenge"?

http://ourworld.compuserve.com/homepages/kevtronics/ams-chal.gif

Kahn had some "ME-1"-type clipping built into his AM Stereo exciters because due to the phase shift involved with his system, the waveform of pre-clipped peaks would not be preserved when it hits the air, resulting in overmodulation. In fact I believe he also recommended you to disable pre-emphasis in your audio processor and let his box do it instead.

Kahn also got all hot and bothered because his system was more difficult to modify to meet the NRSC spec than Motorola's C-Quam. He claimed that his AM Stereo system was more "spectrally clean" to begin with and that NRSC was just a kludge to keep hotly-processed C-Quam stations from splattering onto adjacent channels. Right or wrong, the NRSC 10 kHz cutoff did eliminate interference to the second adjancent channels... but now IBOC proceeds to totally defeat its purpose!

 

[RadioMan203]

Was that the audio processing responsible for "The AM Stereo Challenge"?

http://ourworld.compuserve.com/homepages/kevtronics/ams-chal.gif

Funny how someone lifted the graphic right off my station tribute web site:

http://wmmmradio.tripod.com/

and before anybody says anything, yes the site needs to be updated badly! I plan to expand it when I get some free time.

Actually, the station went AM Stereo prior to me becoming chief engineer. They were running the first generation CRL AM Stereo system, similar to the processing that WEBE was using around the same time - in fact, it was probably due to the influx of cash from the sale of the FM that allowed the former sister AM to go Kahn Stereo in the first place, thanks to CE Clayton Hintz.

Kahn had some "ME-1"-type clipping built into his AM Stereo exciters because due to the phase shift involved with his system, the waveform of pre-clipped peaks would not be preserved when it hits the air, resulting in overmodulation. In fact I believe he also recommended you to disable pre-emphasis in your audio processor and let his box do it instead.

I remember the clipper pots in his exciter, and they did let you get pretty agressive and if you were careful it would stay pretty darn clean. I found that out after I took most of the CRL stuff offline and put my 8000a in place at the studios.

Kahn also got all hot and bothered because his system was more difficult to modify to meet the NRSC spec than Motorola's C-Quam. He claimed that his AM Stereo system was more "spectrally clean" to begin with and that NRSC was just a kludge to keep hotly-processed C-Quam stations from splattering onto adjacent channels. Right or wrong, the NRSC 10 kHz cutoff did eliminate interference to the second adjancent channels... but now IBOC proceeds to totally defeat its purpose!

I honestly don't remember that, but I've always had great conversations with Leonard. A very knowledgeable guy for sure, and IMHO I think his system should have been made the standard for AM stereo. I know Clayton did a lot of work on the directional array before I got my turn at the engineering duties, but I know he spent a great deal of time optimizing it.

 

[CW]

I honestly don't remember that, but I've always had great conversations with Leonard. A very knowledgeable guy for sure, and IMHO I think his system should have been made the standard for AM stereo. I know Clayton did a lot of work on the directional array before I got my turn at the engineering duties, but I know he spent a great deal of time optimizing it.

I remember the Kahn lawsuit against the FCC after they made CQUAM the standard...The spectrum analyzer pics showed in the suit proved Leonard's case....his was the cleanest spectrally....and HE is very knowledgeable....just a poor salesman (his refusal to allow licensing of his receiver decoder design was a mistake!!! THAT killed Kahn's AM Stereo system and allowed Motorola to jump into the lead during the "Let the marketplce decide" era of Reganomics. Of course, Kahn's system has its downfalls; poor stereo sep above 5-6kHz and the antenna array MUST be flat or balanced in its reactance curve or else one channel will have a different freq response than the other...and in stereo, that sucks. I think with IBOC being allowed (not mandated!), KAHN should file a motion to allow his AM stereo system back on since it causes less spectral noise than IBOC or CQUAM! (at least with two radios, you can get the stereo effect! Noone has to sell special rcvr for that but then I still have my SONY XR-33A with the four in one decoder chip...so I could listen to Kahn again; never listed to CQUAM on it...Oh wait, YES I did!!.....WLS was CQUAM in the 80s!)

 

[kevtronics]

Noone has to sell special rcvr for that but then I still have my SONY XR-33A with the four in one decoder chip...so I could listen to Kahn again; never listed to CQUAM on it...Oh wait, YES I did!!.....WLS was CQUAM in the 80s!)

WLS is still C-Quam AM Stereo today. They had been using IBOC for a while, but at least when I last checked a week ago, they had switched back to C-Quam.

And as for Ol' Lenny, he's been trying to push his CAM-D system, which he claims to be a digital AM system that works better and causes less interference than IBOC. He claims to have CAM-D exciters in production and a handful of stations are using it on the air, although with questionable legality since the FCC has never proclaimed CAM-D to be either allowed or disallowed.

You can also still transmit Kahn Power-Side, the mono single-sideband derivative of Kahn AM Stereo, with a 15 Hz Kahn pilot tone if you want, fully legally. 1280 WADO in New York City was doing that until a few years ago, and it would cause my multi-system Sony radio to pop into Kahn AM Stereo mode, with the audio much louder in one channel than the other. I believe 1600 WWRL is still transmitting Power-Side today, although without the pilot tone.

 

[fugazi]

Amazingly i heard one went last week for $5000!!!!!!!!!!!!!! to greece.

This is nuts ;-)