Jim Fosgate: Of (Surround) Sound Mind Page 2

Guttenberg: Jim, this is getting a little weird...

Fosgate: My working method is a little unusual. The first thing I do with any design is program the circuit into my brain and emotional system. Mind you, I don't actually build prototypes or put any of this down on paper—at this point I'm working through the details of the circuit in my head. I had to finally force myself to build the first Dolby Pro Logic II prototype. I guess I was afraid that it wouldn't work, or that the whole thing was just a head trip.

Guttenberg: I've heard the first prototype was an all-tube design.

Fosgate: Yes, I built it with tubes because I love tubes, and possibly because it took longer to do it that way. It was a huge breadboard with 24 tubes and three power transformers! The circuit went through three major revisions, but the first one worked beautifully, and I immediately knew it was a lot better than any other matrix processor. I brought Norma in to listen—she has an ear for surround—and she thought it was a great improvement, too.

Guttenberg: Where did you go from there?

Fosgate: I worked on it for another six weeks and built a solid-state version for my car. I drove to the winter CES in Las Vegas, and played it for Roger Dressler of Dolby. After a 30-minute demo, he turned and said, "This constitutes a breakthrough, doesn't it, Jim?" That's exactly what I wanted to hear.

Guttenberg: Whew, what a relief!

Fosgate: A few months later, Roger came out here to Heber, and we performed a few tests together. We encoded the five channels from a Dolby Digital DVD down to two channels and ran that stereo signal through the PLII. That way, we could compare the sound of original discrete five-channel mix to the PLII's matrixed five channels. And at first we thought the switching system wasn't working—the sound hardly changed when we hit the switch. After pulling cables and checking out everything, we realized, by God, it is working! The A/B'd sound was that close!

Guttenberg: So you presented Dolby with that all-tube, all-analog PLII prototype. How did they transform your idea into a usable digital form?

Fosgate: Actually, I built a solid-state breadboard patterned after the tube version, substituting operational amplifiers for the tubes. Dolby's computers crunched numbers around the clock for three months on the circuit, and they needed several more months to write digital code before we could audition the result.

Guttenberg: That's pretty amazing, since you cooked up the whole thing in your head—and never touched a computer.

Fosgate: Right. My wife was pretty surprised when she saw [that] the first PLII patent ran 200 pages. She had some empathy for what I'd been mulling over for so many years. When Dolby finally sent the digital version for me to audition, I compared it to my tube analog processor. I couldn't tell any difference, soundstage-wise. Roger headed up a listening panel at Dolby and, with their input, we further optimized the circuit.

Guttenberg: How did the refinement process play out?

Fosgate: I could make a change in Utah, fax it to them in the evening, they would rewrite the code, and send the new code to me over the computer. I'd burn a new EPROM and listen to the change—all within 24 hours. It took 40dB of negative feedback in the steering logic to optimize the channel separation.

Guttenberg: Uh-oh, feedback—that's going to rankle some Stereophile readers.

Fosgate: In this case we're not talking feedback around the audio signals, only the steering logic that controls the channel separation. Other matrix decoders, including all my earlier stuff, were "open-loop," feedback-free versions, but they all have serious limitations. The feedback logic circuit in PLII provides faster and more accurate logic action than an open-loop approach. It's able to track the signals in real time, even when the loudest signal is constantly changing directions. I have a very good audio memory, and I can remember what something sounds like from one day to the next, or even from one month to the next, although for the last few tweaks I used A/B comparisons to nail the final version down.

Guttenberg: I guess this is a good time to ask: What, exactly, is the difference between the original Pro Logic and Pro Logic II?

Fosgate: They both have their roots in quad and SQ matrix-style encoding/decoding. The original Pro Logic had mono "band-limited" surrounds, PLII has "full-bandwidth" stereo surrounds. Since original Pro Logic was a film-oriented system, Dolby had to make sure the center/dialog channel was rock-solid. So they weighted the steering toward the center front channel, which shrank stage width on stereo recordings. When Pro Logic came out, it was a marvel of performance and stability.

Guttenberg: PLII can work its magic on LPs and CDs?

Fosgate: Yes. Please understand that PLII doesn't affect the stereo soundstage, other than to display the in-phase part of the program over the three front channels—the out-of-phase or randomly phased signals are sent to the rear. When switching between stereo and PLII, you'll see that the stereo soundstage stays intact but has greater depth and width. Sometimes you're not even aware of the extra speakers, until you turn them off and the soundstage collapses back to stereo.

Guttenberg: It's more than a little ironic—your invention has made you a wealthy man, but you created this home-theater processor with music in mind. Literally.

Fosgate: I do most of my surround work listening to stereo music—movies no more than 2% or 3% of the time. During my 25 years of work on these circuits, I can say with all honesty that most of the listening was done using vinyl program material. I couldn't see why a circuit couldn't work equally well with music or home theater. I consider Dolby the experts on movies, and they're quite satisfied with the way PLII sounds with movies.

Guttenberg: PLII comes in two flavors, Music and Movie. What's the difference?

Fosgate: In the digital implementation, the logic is the same for both modes, but the movie mode adds some time delay to the rear channels for a more frontal presentation. Of course, you can listen to movies in Music mode, which is the way I listen to DVDs. I recommend trying it both ways to see which one sounds better to you.

Guttenberg: Can PLII break on through to the two-channel faithful?

Fosgate: In real life, we're used to hearing in a 360º sphere from all around us. Stereo is unnatural in that it is coming only from the front speakers. With my triamped, all-tube system, stereo sounds very, very good—it's what great stereo is all about—but when I switch from stereo to multichannel, there's no comparison. It's not that one is so aware of the back channels, but PLII makes the front soundstage wider and deeper. Some of my guests aren't aware of the rear speakers' contributions until I turn them off.

Guttenberg: But audiophiles associate multichannel with a mid-fi mindset. They have a hard time accepting that multichannel can be built to the same standards as the best two-channel gear.

Fosgate: That's true, and if I had to decide between a great two-channel audio system and a frumpy home-theater thing, well, sure, I'd go with the stereo. I know a lot of Stereophile readers think stereo is perfect, but I'd hope they can be open-minded and listen to what we can generate with a no-compromise, all-tube surround processor like my Fosgate Audionics FAP-V1. If you can take all the things we've learned about building a great system and carry that into surround, it's no contest. That's exactly why I designed the FAP-V1 for music lovers—but it can also play movies.

Guttenberg: You [along with Peter Schreiber and Dolby] won an Emmy in 2003 for the Development of Surround Sound for Television. After all these years of keeping the faith, the Foz finally gets his due. Congratulations!

Fosgate: Yeah, that was a big surprise. When they first contacted me by e-mail, I didn't realize they wanted to give me an award, so I didn't respond. When they finally called me on the phone, I understood and snapped to. It was a wonderful honor. I was humbled.

Guttenberg: What are you working on now?

Fosgate: I'm just playing with my tube gear and tweaking my phono system and amps. I don't think they're destined to become Fosgate products because they're too specialized—the phono preamp would be better suited to an outside manufacturer.

Guttenberg: I'm guessing you're open to offers.

Fosgate: I'd like to see it out there in the world so I could share the sound with other audiophiles, so sure—I'd be interested.

ARTICLE CONTENTS
Share | |

X
Enter your Stereophile.com username.
Enter the password that accompanies your username.
Loading