04 May How it all started: The history of the SVDS
Over the past few weeks lots of questions regarding old Cetec-Vega devices and technical details of the original Schaffer-Vega Diversity System (SVDS) came up. We got mails, people asking and discussing in the comments, so we were able to contact Mr. Schaffer himself to ask if he would be so kind as to fill-in pieces about the technology and of the history we didn’t already know – basically, “How did this all happen?” which leads to more questions and discussions of course – and he was agreeable.
So, get ready for a nice dose of Rock history!
For the impatient reader, I’ll sum up the key facts first. For the rest of the people, have a nice reading of more detail, and Mr. Schaffer’s comments below the key facts, which are really worth reading:
- Cetec-Vega devices were not intended or tailored for use with a guitar. Vega specialized in building wireless microphone gear for “relatively” non-demanding, low decibel, applications. SVDS was the first system to be designed, tested and built specifically for guitars.
- While the known 50kOhm (or 100kOhm) mod is known to match the input impedance of a Cetec transmitter with the impedance of a guitar, it does nothing else… there are other, even more substantial, differences between the Cetec and the SVDS X10. Even with the mod, no Cetec unit sounds like an SVDS.
The SVDS 63EX receiver was based on a Cetec Vega 63 Model, with refinements as follows:
- A guitar produces signals that are much more demanding than a microphone’s: complex waveforms with fast attacks, lots of notes simultaneously and strong harmonics – and you play it loud! Microphones are “easy,” the human voice smooth as silk. But to accommodate a guitar bound for 100+ dB amplification, both the transmitter and the receiver must break new ground and process signals very differently.
- Of the major differences between the SVDS and standard Cetec systems, companding is of course the most obvious. In order to gain the full advantage of companding, other factors need be addressed in designing the transmitter, such as pre-processing the signal even before feeding it to the (transmitter’s) compressor. Pre-emphasis (in the transmitter) and de-emphasis (in the receiver), and their associated time constants have to be carefully calibrated in order for the receiver’s expander to accurately track the transmitter’s compressor.
- Several 1980-era Cetec devices are labeled with “Dynex”, which stands for “Dynamic Expansion.” Mr. Schaffer did not have anything to do with Cetec’s “Dynex” technology; it was introduced after Mr. Schaffer moved on to pursue other interests (1980).
- Maybe (we don’t know it) “Dynex” is based on Mr. Schaffer’s work though. (Cetec was not allowed to use Mr. Schaffer’s invention for its own devices during the time 5 years he was active with SVDS.)
Ok, those were the key facts so far. Now some historical information about how it came about:
The story of the SVDS
1. As an idea, the The SVDS was born while Mr. Schaffer was out (“doing odd jobs”) on the Rolling Stones’ 1975 “Tour of the Americas.” He explains: “The ’75 tour marked the first time promoters sold tickets behind the stage, which sort of obligated Mick to grab a wireless hand mike a few times each night to go ’round back and show some leg. And almost every night, there was trouble – some of it was hilarious: the mic would crap out – RF fades one night… interference from taxi dispatchers, doormen and police calls the next. At its best, limited dynamic range made it sound terrible compared to a corded mic. Seeing that was my inspiration, what got me off to find solutions.”
“A wireless mic is just a radio…” Mr. Schaffer had been building radios since he was a teen-aged ham operator (“call letters” N2KS), had a hand in building a couple of New York’s studios and felt sure that he could make a better radio. Once off-tour, he began fiddling with one of the band’s wireless systems.
2. In 1975, Vega’s Model 58 receiver, mated to their Model 77 lavalier transmitter or various Shure hand mics, was nearly an industry-standard in the relatively low-amplitude applications of the day: film production, broadcast, summer theater, preachers. The 58 itself was simply a well-made radio receiver – nothing fancy – a non-companded single ended receiver that, like the 77 transmitter, had minimal signal processing – well-made, but with specs that fell well short of what was needed to deliver the signal from a guitar accurately and reliably. Amongst then-current wireless manufacturers, the Vega division of Cetec Corporation distinguished itself, to Mr. Schaffer’s eye, by going “the extra mile” to stabilize the frequency tolerances of its transmitters and receivers through crystal control using expensive helical resonator cavity filters on the receiver’s front-end to fight interference, As Mr. Schaffer accounts, “They “made” (as in “construct”) good stuff – why I chose them to manufacture.”
Mr. Schaffer, at first, started applying various tweaks and new ideas, especially companding, to the “usual” hand mic. Early into it he switched tracks and had the idea to build something that never existed: a system specifically for guitar. That proved to be far more demanding. After developing prototypes, Mr. Schaffer struck a deal with Vega to manufacture his system, the first companded wireless system of any kind, as well as the first system designed specifically for guitar.
3. The Vega 77 transmitter didn’t feature companding – it actually used a limiter to clip the tops off signal peaks. The X10’s audio front-end, time constants and pre-emphasis pre-processed for guitar, optimized its signal to be passed into a fixed 2:1 compressor for transmission to a fixed 1:2 expander, and its associated processing, in the receiver. This was “companding,” introduced for the first time. The transmitter’s 2:1 compression squeezed together the highest and lowest amplitudes of the guitar’s signal so that the whole signal could fit inside the narrow range that lay above the noise floor and below overloading. Transmitted to the other side of the circuit, the 63EX receiver expanded it back – 1:2, like a mirror. Careful signal processing ensured that the 63EX’s expander tracked the X10’s compressor accurately so there was no “breathing.” The companded SVDS delivered a dynamic range of about 100 dB.
The SVDS paired 2 major components: the X10 transmitter and the 63EX receiver. The X10/63EX combination became a system that overcame the audio limitations of previous wireless systems which could, at best, transmit a S/N ratio and dynamic range way too low for rock n’ roll guitar. The theoretical limit of dynamic range at the 5 KHz maximum FM transmitter deviation permitted by the US Federal Communications Commission was less than 70 dB.
4. Mr. Schaffer: “Noise gates are what I tried, at first, to kill the hiss in between notes… that just didn’t work. You’d hear a whole lot of loud pumping and breathing. It sounded like emphysema or maybe a full-blown asthma attack. But I knew a different technology: companders – Dolby & dbx – were already coming into studios – they were companders… and the technique made it possible to store 100 dB of signal on a 65 dB-limited medium: tape. It was magic. So I figured companding would do the same for another limited medium: radio. It did. It worked.” Companding “tricked” the RF section into delivering close to 100 dB with that same 5 KHz space.
5. SVDS also employed an RF technique known as “diversity reception” to eliminate signal fades – this called for two completely separate receivers packaged together with a comparator that, most simply, silently switched from one receiver to the other when a signal-strength threshold was crossed. This was the SVDS 63EX receiver. The diversity technique eliminated the fades that plagued previous systems.
(Neither Vega nor Mr. Schaffer invented the diversity technique – that was done by a guy with a funny name who, in the 1920’s, ran the US Army’s main trans-Atlantic shortwave station. Signal fades were a severe problem on shortwave… he discovered that he could eliminate them by using 2 antennas spaced at least a wavelength apart… each saw a different world. (Imagine he sat there monitoring signals from both antennas and throwing a big jackknife switch to pick between them at the first signs of a fade.)
6. For convenience and economy, Mr. Schaffer used the same casing as used by Vega’s transmitters and receivers for the X10/63EX. (Though the Vega housing was beige; the 63EX’s was black.)
Please mind the “63” vs. “63EX” models were completely different units!
Looking similar, working different: A Vega Pro63 with Dynex and the SVDS.
Some notes of interest regarding our favorite inventor:
7. Once Mr. Schaffer had manufactured prototypes in hand he took advantage of his luck – to be living in New York and plugged into just about everyone in music. Until word of mouth took off, he’d demo his stuff by loading units into an Anvil case and showing up at almost any gig, a studio or rehearsal stage. It only took a couple of years until most major bands were using one or more SVDS units.
The SVDS was about $4,100; too expensive for any but arena bands. Mr. Schaffer: “I wasn’t keen on making the compromises in design and construction it would take to get it cheap enough to be a real “consumer” model. Anyway, I wasn’t so interested in “commerce.” And I was itching with ideas to develop other stuff.”
8. “I really don’t know much about Vega’s DYNEX systems — we never used that term – it certainly came along after I’d moved on.” Of course, the acronym infers that the systems featured a compander. By the time Vega introduced its Dynex model, companding radios was generic, kind of public domain; SVDS raised the bar, and by the late 70s, companded systems had been introduced by, and were available from, several manufacturers. Mr. Schaffer never bothered to patent it or anything else. “During the years we were building SVDS, Vega couldn’t compete with us. But they weren’t music guys, anyway: even after we’d sold a few hundred units, even after we’d moved off and on, Vega still hadn’t a guitar or amplifier or someone to play it for test. You’d think…”
By 1980/81, Mr. Schaffer became obsessed with satellites and focused away from wireless. He left the music business and went looking for oddball TV in space. In 1984 he developed – of all things – an unusual satellite receiving system that could to tune in to Soviet TV. WTF Kenneth! Mr. Schaffer’s unique system was used by US government agencies and universities to spy on the Soviet Union. He insisted that all the 6 metre satellite dishes be red. (“You wanna eavesdrop on Russia… it’s gonna be RED!”) He came back to music briefly after becoming riveted by the changes he saw (on TV) going on in Gorbachev’s Russia, and in 1988 he brought Boris Grebenshikov, often described as the Bob Dylan-cum-John Lennon of the Soviet Union, to the US and UK to record an album, “Radio Silence,” for CBS, produced by Dave Stewart. In 1991, Mr. Schaffer started a company, BelCom, that became the biggest satellite communications provider to Western companies operating in the former Soviet Union. In 2003, he invented a technology that came to be known as “placeshifting” with a system called TV2Me.
Come 35 years after introducing SVDS… we find Mr. Schaffer still listening to Hendrix, and having 4 mismatched SVDS pairs in his front room closet – as souvenirs.
“Out of nowhere, comes this amazing letter from an irresistibly engaging guy in Rome… he had clearly done his homework — he really, really wanted any old units I could find and to know EVERYTHING about SVDS – particularly, as I understood it, as key to solving the mystery of Angus Young’s guitar sound on “Back in Black.” Crazy obsession, ask me…. but his care and devotion to it was compelling… “
“… before long I was packing up all my vintage souvenirs for a flight to a deserving home Rome.”
Let’s end this article with a nice image:
The SVDS in the news: Performance Magazine, Billboard Magazine, Rolling Stone Magazine
Now, dear members, any more questions? Please tell us in the comments then. Big thanks to Mr. Schaffer for being open and taking time to give us insight into the world of 70s and 80s Rock. We really feel honored.