Monday, December 17, 2007
Vintage HP Test Equipment for Ribbon Mics
In several of our website and blog images there are scenes with some of our old HP test equipment, and I have had a couple of people ask what they are. Click on the image for a larger view.
On the left, an HP 334A Distortion Analyzer, null type, which can be used up to 600 KHz. It is in pristine condition and works very well.
Center is the familiar and ubiquitous HP 651B Test Oscillator, famous for its stability (except at the lowest range) and boatanchor aspect.
On the right is the less-common HP 4800A Vector Impedance Meter, lamp bridge type, with the correct 4801A Balanced Direct Plug-In. This is a far better impedance analyzer than the Hickock or B&K, as it smoothly tunes through the audio band and effortlessly reads Z with very little power actually going into the DUT (Device Under Test). It gets used every day. You can see an EV 635A sitting upright in the test fixture, which has a built in XLR connecter at the base, and a socket sized to fit our larger mics. I'm not sure why that '635 is in there, but it is one of the dozens and dozens of mics floating around here. I use an EV 635a on the air through my Johnson Valiant,,which only passes up to 8 KHz audio.
Above it you can spot another important piece of analog test gear, the highly desirable Panametrics 5052UA Ultrasonic transmitter, stepless gate, and receiver, good up to at least 60 MHz and an essential tool for IVUS or any single transducer test application, especially water-coupled types. With a spigot of gated RF right at the front, the 5052UA can perform pulse and spectral analysis all at once. These were very expensive when new - somewhere in the $3-5K range, but this one was a bargain, bought at the Deerfield Hosstraders many years ago as surplus. I was there with Jim Koger and we both spotted it - I cautioned him to not look too excited: "How much for the box with all the knobs?" I asked. "Twenty" was the reply and I responded. "Take ten?" "OK" he said. That unit got used at Boston Scientific in Watertown, where present-day IVUS was invented, for years, and was this exact pulser that proved that we could make a short pulse, low noise 30MHz ultrasound transducer with nearly zero ringdown, and that led to IVUS as we still know it, 20 years later. And that Panametrics pulser keeps doing its thing too, now with 3VUS, which is the next generation of IVUS.
That little thing on the upper left is a B&K audio and RF sweep generator that I picked up for $5 at a hamfest, and it has its uses.
Chris Regan at the controls.
Posted by Bob Crowley at 12:41 PM