Ortofon DSS-732 Cutterhead
A stereo disc-cutting head built around a 500-watt amplifier, aimed at putting nothing into the lacquer that wasn't already on the tape.
Overview
As Studio-Sound (July 1975, p.49) advertised, the DSS-732 is not a cartridge. Collectors who know Ortofon only from its phono pickups tend to assume the DSS line is another family of moving-coil cartridges. It isn't. This is a cutterhead, the business end of a disc mastering lathe, the piece that swings a heated stylus through lacquer to carve the groove a record is stamped from. It is professional mastering hardware. It turns up in the same catalogues as Ortofon's consumer cartridges because the company made its reputation on both sides of the groove.
Ortofon specified the DSS-732 for 10 Hz to 20 kHz. The drive behind it was the GO 741 cutting amplifier, a 500W-at-20kHz design built specifically to command this head. The amplifier's negative-inductance circuit fought the natural rise in drive-coil impedance at high frequencies. That held current constant, so the head could deliver the top end it was rated for.
The head is a stereo cutter with a vertical cutting angle of 15°, available at 20° to special order. Maximum stylus excursion in the 45° direction is 100µm. Drive-coil resistance is 8.5Ω, feedback-coil resistance is 135Ω, and the feedback-coil voltage is 8 mV/cm/s lateral. The motional-feedback ratio at 5 kHz is 10 dB for the 732 - the 731 runs 12 dB - and the feedback turnover point sits at 20 kHz.
What the feedback buys is separation, and that is the reason the head exists. Cutting engineers of the period fought resonances in the supersonic region, and the usual fixes were to roll off the highs or to equalize around the peaks. Ortofon's answer, laid out in its own 1979 advertising, was a head with the lowest secondary resonance above 24 kHz. That is the company's claim, not an independent measurement. The idea was that response stayed flat and separation stayed high in the lacquer.
The 732 was the standard stereo member of the pair. Its sibling, the DSS-731, was the four-channel discrete version, built for half-speed cutting of systems using ultrasonic carriers, with response quoted to 25 kHz. Ortofon's own copy described the 732 as the more rigid version of the 731, covering the range up to 20 kHz and meeting what the manufacturer called all reasonable requirements for high quality stereo recording. Both heads carried a considerably higher stability reserve than the earlier DSS-661, and both were said to allow more than 18 dB of feedback at 5 kHz in typical operation.
The supporting gear was a real part of the system. The STL-732 regulated filter was a two-channel treble limiter built to prevent non-permittable high-frequency levels from reaching the cutter, accepting line levels up to +12 dBm with attack adjustable from 0.3 to 100 ms and release from 3 ms to 1 s. The CPS-741 correction amplifier handled four channels - two programme, two preview - with phase reversal, EQ and monitor controls. The GO 741 amplifier set, sold as a pair with a common GE 741 power supply, carried current and temperature meters on the front panel and a monitor amp with replay-cartridge equalisation for A/B checking during a cut. Temperature feedback would cut power if the head overheated, so these were clearly driven hard.
That is 1979 money for a single cutterhead, which explains why these lived in mastering rooms and not on shelves. The 731 cost more than the 732, which fits the extended response and half-speed four-channel work it was built for.
It is rare, and it is not the sort of thing that changes hands on the consumer market. A DSS-732 is only useful to someone with a lathe, a GO 741 pair, and the appetite to keep a helium-cooled cutterhead alive. The helium cooling and hand-wound coils described in the factory report make service difficult decades later. Buyers should expect to find these as part of a complete cutting system rather than as a standalone head, and should treat any listing that presents one as a drop-in consumer component with suspicion.
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