PROFESSIONAL SYSTEMS ENGINEERING (PSE), STUDIO III TUNERPSE STUDIO III tuner in excellent original working condition. As you can see in the pictures, this is in extremely nice condition. The only item to be addressed is a missing (stuck on) foot on the bottom. It is the way I got it many years ago. The following is from the Tuner Information Center site: The early-'80s vintage PSE Studio III was the only tuner manufactured by Minnesota-based Professional Systems Engineering. It is analog-tuned with a digital readout. The Studio III has a copper shield covering the front end that is soldered to the board on all four sides. A toroidal power transformer is also on board. Its tuning indicator is similar to that of the Nakamichi 430: rectangle-shaped green LEDs that fade on or off, then glow evenly when properly tuned. A round red LED, for stereo indication, is centered between the green tuning LEDs. The tuner has six preset tuning slugs with similar adjustment requirements as the Magnum Dynalab FT-11's three. The PSE's six presets scroll in one direction only by pressing 'SELECT' on the front panel, and six rectangular green LEDs light up one at a time and coincide with the tuning slug adjustments. With the first six SELECT modes, you lose manual tuning; when you press SELECT a seventh time, all six presets go dark and you regain control of manual tuning. Turning the tuner off, then back on resets the tuner to manual tuning. Lots of nice quality-looking parts cover the board and a fresh-looking handmade appeal greets you when the cover is removed. At the output are a pair of TLO70CP J-FETs. Similar to some Magnum Dynalab 101 series tuners, the PSE has high- and low-output RCAs. But unlike the Magnums, whose low output bypassed the 5532 stereo op-amp entirely, the PSE has a two resistor per channel shunt that drops the stereo signal. Its two ceramic filters are marked E10.7L G1, and the MPX chip is an MC1309P. The Studio III is quite rare. According to Crispin Metzler, the engineer who designed the Studio III, it used "double conversion with a comparator driven 96S02 monostable detector. The microstrip front end with pin diode AGC attenuator provides superior selectivity and was simple and easy to align in production. The comparator and TTL/CMOS digital detector share the same main board with the RF front end with no measurable impact on sensitivity or quieting." Cris adds additional detail: "The PSE tuner was built on low-loss PC Board material. I used 9 inch long micro-strip lines in the front end instead of the usual coils. This made alignment a snap (they could set trimmer caps by eye!), but did cause some frequency drift challenges when the board material was changed. The first mixer was push-pull JFET's (later production used MOSFETS), driving an IF amplifier consisting of 10115 ECL line receivers (cheap, with superb overload tolerance) and linear phase 10.7 MHz ceramic filters. A 10107 ECL XOR/XNOR gate provided a $0.25 balanced mixer/oscillator/bias generator IC for the second conversion to 600 kHz. This drove a balanced 6-pole LC Gaussian phase second IF filter, which drove a slicer consisting of an LM306 comparator. Both zero crossings were used to drive the monostable (sometimes called a 'pulse counting') detector giving an effective second IF of 1.2 MHz with large deviation. Heath Zenith had attempted an FM tuner with a monostable detector, but the results had been rather poor, especially with classical music. I traced the problem to their use of a single monostable at 50% duty cycle. The input state would slightly modulate the timing because of metal bus and bond wire drops; this resulted in a 'glitch' in the transfer function right at the 50% point! It could be seen on a a scope and in hand plots of the detector transfer curve. Adding resistance to the VCC pin would increase the distortion. While virtually undetectable with 100% modulation, it did awful things to flute solos! My use of two monostables (96S02) at 25% duty cycle each, OR'd together eliminated this source of trouble since one only fired with the input high and the other only fired with the input low. To eliminate any chance of supply-related troubles, both 'true' and 'not' outputs of the 96S02 were OR'd in a buffer to give a differential output into a linear phase differential 76 kHz filter. Only then were op-amps permitted into the signal chain! I never succeeded in measuring the tiny distortion of this detector by itself. Hand plots were linear to within the width of the pencil line. A Motorola stereo decoder was loaded into linear phase 3-pole filters referenced to the positive supply instead of the recommended simple resistor load and the best op-amps I could locate were used throughout. I added a canceling circuit for the 19 kHz pilot tone which some people find to be annoying. The whole thing was packaged in a one inch high by relay-rack-width black case with LED displays for frequency, tuning, and six preset channels and was built and sold by PSE for many years until too many of the semiconductors were obsoleted. Some kind soul at National Semi scrounged wafers out of desk drawers for the final run of these tuners."
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