Ampex Model 601
A stereo tape system that ended up bolted into the dashboard of a Citroën. That tells you how seriously people took it.
Overview
The Model 601 is a stereo tape recorder built around the Model 601 tape transport. The configuration collectors usually run into is the 601-2: that same transport paired with two Model 601 electronic chassis for stereo record and playback. It has full-track erase with stacked record and playback heads, running at 7½ ips. It was designed to be worked, and people worked it hard, in places tape decks had no business being.
The numbers are respectable for the period. Frequency response is quoted at 40 to 15,000 cps, with 40 to 10,000 cps held within ±2 db and no more than 4 db down at 15,000 cps. Wow and flutter is under 0.17% rms. Signal-to-noise runs over 55 db below peak recording in the full-track configuration. The 7½ ips speed is fast enough for real high-frequency content and slow enough that a session didn't burn through tape.
The most famous thing that ever happened to a Model 601 happened in Monte Carlo. Radio Monte Carlo had one built into the dashboard of a Citroën DS-19, and the station's chief engineer, M. Auvray, used the mobile rig to simplify remote recording for broadcasting. The electronics were modified for the car: two switchable inputs so playback could be mixed with a microphone, or two mics mixed for simultaneous recording. The center-dash meter panel carried the regular VU meter plus a voltmeter and a frequency meter. Power came through a 50-cycle converter off the Citroën's 6-volt battery. Cables and accessories lived in the trunk so the cabin stayed usable for passengers.
Owners in the used market were already treating the 601 as a known quantity by the late 1950s. It wasn't an exotic. It was a catalog machine with a real installed base, which means parts machines and documentation turn up more often than they do for the oddball stuff. Period coverage of the era's tape recorder market, such as the quick-reference roundups in Audio-Record (September 1956, p.2), treated the Ampex line as established catalog equipment rather than a novelty.
The 601 family is modular. The transport and the electronics are separate pieces - the 601-2 is literally a transport plus two electronic chassis - and that makes it easier to service. When a channel goes quiet, the fault is usually traceable to one chassis rather than a monolithic board, and the erase/record/playback head stack is straightforward to inspect. The stacked-head, full-track-erase layout is also why the full-track signal-to-noise figure is the one worth quoting: erase happens across both channels at once, so there's no half-track erase compromise in the noise floor.
The caveats are the usual ones for a machine of this vintage and this duty cycle. Heads wear, and a deck that spent its life in a broadcast or institutional setting will often show it. The 7½ ips-only running speed is a limitation if you want the extended response of 15 ips. And the automotive conversion story shows that many 601s led hard lives before they reached a collector's bench. A clean, unmodified example with healthy heads is the one to hold out for. A modified or heavily serviced unit needs its provenance read carefully.
For a period-correct stereo tape front end, the 601-2 offers full-track erase, stacked stereo heads, 7½ ips, and a transport designed to be maintained rather than replaced. It won't win a spec war against later machines.
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