Frese 'Audio Pilot'

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RodeoJack
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Frese 'Audio Pilot'

Post by RodeoJack » Sat Jul 18, 2015 11:14 am

Seems there are more than a few here, who might go back far enough to remember this processor. Possibly, it was seen more in the Pacific Northwest, because it was hand-made by a consulting engineer from Eastern Washington (George Frese).

Local legend suggests the 125% positive peak limit was largely credited to this 'box' (filled about 1/3 rack). It was sold during the early days of the Volumax and yes, if you had a transmitter that could handle it, it could conservatively be called a 'screamer'. George says he discontinued it because he couldn't easily rein it in well enough to run below 125%. It's probably too late to lend credence to legend, but I think it's safe to say there weren't any modulation monitors out there that could measure what this thing could produce.

I'm wondering if it found its way outside the Washington State area. George said he built around 46 of them and, so as to avoid destroyed modulation sections, did the initial installation on all of them. I worked on or can account for only 9.

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Bill DeFelice
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Re: Frese 'Audio Pilot'

Post by Bill DeFelice » Sat Jul 18, 2015 11:58 am

I remember reading about this on a few broadcast blogs but audio engineer Bob Schwenkler has a picture of it along with a scan of the original manual for the beast.

http://www.schwenkleraudio.com/technica ... chematics/
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RodeoJack
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Re: Frese 'Audio Pilot'

Post by RodeoJack » Sat Jul 18, 2015 12:39 pm

Yep. That's it. The description in http://www.thebdr.net/articles/audio/proc/proc-hist.pdf is very close to my recollection, though it seems I was off by a few units.

George was a first-chair violinist, and he put his musical experience to use in the development of the processor. I was a little dismayed to see how the design continued to evolve as he sold the things. Guess it's not too surprising, but now I wonder where the ones I had stood in that line. Bernie Wise tended to do a bit of that, too.

The article answered my question about how widespread the installation base was. Thanks for that.

I do recall his feelings about release time. When trying to adjust an old Gates limiter, back in the '70s, he suggested I set the 3-position release switch to one of the slower settings. His feeling was that, by providing a bit more dynamic range, the station would sound better overall, even if that limiter couldn't make you the loudest thing on the dial. That was when a lot of us were just using Sta-Levels and a wideband limiter of one brand or the other.

The BDR picture is the standard layout of the processor. The Schwenkler picture shows the positive polarity switch and "float clipper" section in different order.

Oh... this thing would tear your ears off when it decided to switch polarity. That was simply done by a DPDT relay. Amazing, how much different your voice sounds in your headphones when something like that decides to switch. You'd come out of a song, get through 2 or 3 words and bam! Took a bit of getting used to.

In a studio installation, it was a bit noisy. The polarity and gate functions had relays in their circuits, which were constantly clicking away.

Some fond memories of that processor though. I had more than a few people wonder how we made our stations so loud. The irony was that a couple of those transmitters were "only slightly modified" Bauer 707s or RCA BTA-1s, neither of which handled aggressive processing all that well 'out of the box'.

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Re: Frese 'Audio Pilot'

Post by sallen » Tue Aug 25, 2015 7:10 pm

Shock and amazed I had the privilege of rediscovering the Audio pilot installed at KOL in Seattle. It will soon be on display at one of the transmitter sites I maintain on Vashon Island. I was just amazed at what I was looking at and it's all there. I maintain a two heritage sites on Vashon Island and have been collecting old broadcast gear to display. This will be one of the center pieces. I was just blown away at what I was looking at.

Are there any Audio pilots in working condition? The goal is to maybe get this one running. To be able to display it when people come to visit the transmitter sites on Vashon is more than I could hope for.

If it were not for this thread being fresh in my mind I might have not realized the piece broadcast history I was looking at. In the next month I hope to get it moved and racked up at the 1090/770 site on Vashon Island.

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Re: Frese 'Audio Pilot'

Post by RodeoJack » Wed Aug 26, 2015 10:57 am

Incredible find. Congratulations!

Bill Wolfenbarger might like to hear about this, if he recalls the processor.

Other stations you might try, if you can find people who recall those early installations:
KRKO
KGY (now KBUP)
KPQ (both AM and FM versions)
KWSU

There was one at (then) KREW, but ownership has changed several times, it's no longer at the tower site and the person who bought it has passed.

Greg Smith may know of a few more, if you have contact with him. I understand there may have been some of these in Bellingham and the Tri-Cities.

This may be nothing but a novel thought, but someone in Seattle recently told me George installed the processor at one (or more) of Mexico's "border blasters". That brought up a number of visions. First of all, it took a bit of diligence to keep the processor operating properly, though that wasn't particularly complicated... just something that had to be done now and then. After that, one might consider the transmitters this thing might have been hooked up to. If it was working correctly and there was plenty of power available, and I understand this was a challenge, a Doherty might be a good candidate. If I recall, the early Ampliphase transmitters didn't like asymmetry, and most plate rigs really wanted more iron. Considering how big some of those transmitters were, that might have been a challenge. The processor made transformers hot and modulator tubes glow impressively. On the other hand, the stories you read about those installations suggest some of those transmitters rarely ran at full power, so there may have been some capacity there.

Comparing this to a guy with a lead foot and a muscle car... If the stories were true about corona discharges around insulators and distant fences, and how turning up the juice could dim the lights in nearby towns, one might naturally think, "wonder what would happen if we tossed in an Audio Pilot!"

sallen
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Re: Frese 'Audio Pilot'

Post by sallen » Wed Aug 26, 2015 2:23 pm

If we get it going there is a Nautel NX50 we can try it out on. Old meets new. Of course this will be in the analog mode. I do have a 317C2 at another site and a DX50 at the shared site with the Nautel.

RodeoJack
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Re: Frese 'Audio Pilot'

Post by RodeoJack » Wed Aug 26, 2015 6:11 pm

Would love to visit the site when you do that, if it can be arranged.

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HadYourPhil
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Re: Frese 'Audio Pilot'

Post by HadYourPhil » Mon Sep 07, 2015 3:19 pm

I'd love to hear one...
We improve things by making them worse...

RodeoJack
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Re: Frese 'Audio Pilot'

Post by RodeoJack » Tue Sep 08, 2015 5:20 am

I'd be careful not to expect too much, given what most stations use today. The Audio Pilot was introduced before discriminate processing came about... certainly well before the Dorrough, but maybe more around when Langevin had their try? I saw my first installed unit in 1972 or '73.

The AP was mainly a single-band comp/limiter with what might pass for "complex" release circuitry. It did have a second stage, but that was controlled by the modulated envelope and, possibly, the float clipper. That stage was the reason you didn't need to pad down the audio when changing power levels from day to night. It also was what dealt with modulation levels vs aging tubes. You knew you needed a new set when you got up one morning and noticed the station was loud enough, but beginning to sound ragged. The 2nd stage was very slow and looked more like an AGC on the wrong side of the limiter, if that explains the effect in had on the audio itself.

Other engineers I've talked with about the AP recall the impressive speed with which it caused transmitters to go through modulator tubes. Even after being modified, the AP was responsible for its share of blown modulation transformers. In the hands of someone, determined to knock his neighbors out of the water, none of the 4-400 based high-level plate rigs I saw had enough iron or design overhead to stand up to an audio pilot with its foot to the floor. Without much effort, it was easily the nemesis of a Bauer 707. It did behave well with the BC5 series, which we had a bunch of over here, and Dohertys seemed to like it. Not sure there would have been any point with an Ampliphase. George understood the relationship between his box and any given transmitter well enough that the stations always sounded good when he left. It was easy to modify his settings though, and that's where people tended to get into trouble with it.

I only recently found out that George modified the processor as subsequent models were made. Back when I actually had my hands on those things, I didn't know, and I don't recall it coming up in conversation. I wrote off the differences between stations to everything but the but the AP. Now, I wonder....

I expect a working processor to be loud as hell. How clean that will be remains to be seen. Having a single band, I do recall spending a lot of time, trying to find a spot where it was reasonably aggressive without pumping. In that, I'm not sure I was ever satisfied enough with the results to leave it alone. In conversation with him, George held that, when adjusting release times on anything, less was more. The Audio Pilot had a continuously-variable release "pot", where most other limiters of the time had 2 or 3-position switches. For easy-listening (MOR) or talk formats, it wouldn't have been hard to set up at all.

My faded recollection was that the early (CBS) Audimax/Volumax combos sounded somewhat better with percussive audio, if not as loud. I think disco would have made all of those systems wilt.

Will definitely be interesting to see how well my memory of the processor holds up!

HadYourPhil
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Re: Frese 'Audio Pilot'

Post by HadYourPhil » Sun Sep 13, 2015 10:30 am

The A/V combo was fast enough that percussion didn't sound bad through it, but given the increased bass content of songs in the late 70's and beyond, they would pump on that material. Enter the DAP.
We improve things by making them worse...

Old-Mazda
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Re: Frese 'Audio Pilot'

Post by Old-Mazda » Tue Sep 13, 2016 12:54 am

Interesting, There was an "AP" at KOZE in Lewiston, ID. George demonstrated it to me while trying to sell another. When the station dropped to 1kw at night, he could hit almost 200% modulation. George was quite a guy!

RodeoJack
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Re: Frese 'Audio Pilot'

Post by RodeoJack » Fri Sep 16, 2016 5:39 pm

Oh, there's no doubt he was onto something back then. "Hadyourphil" makes a good point about bass pushing the processor back. It had only one band and turning the release up would make it pump badly. In fact, that worked against George's philosophy about things. When I told him about an old Gates doing that, he told me to turn the speed down (position 3 of 3, as I recall). In his mind, the clipper pushed modulation higher than anything else in town. Reduce density and people would perceive better dynamics and a loud signal.

I'm not sure if any of his procs were still running by the time the Orban or Gregg Labs stuff started coming out. The 125% limit might have shut them all down by then. Would have been an interesting comparison but, like I said, I have 40 years of sentimental memory about it and am not sure I'd want that shattered by an Omnia One.

On another (related) subject. Someone here might recall that George built an Audio Pilot for FM! I know of only one such animal, which he installed at KPQ-FM, where he lived (Wenatchee, WA). Literally... TWO 3-foot racks, side by side... left & right channels, feeding the STLs. It would have been very interesting to see how he kept them tied together. Also, given how the system was originally built for AM, I'm wondering if he just left the float clipper and RF part out of the FM version.

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