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A view of the underside of the Stellavox SU8 with the bottom plate removed.
Like the equivalent Nagra, the Stellavox had a single servo motor with an optical tachometer. Tape
transport was by a single capstan and belt driven reel hubs. In fact a single duplicated drive belt was used, presumably to allow for breakages. Tape tensions were controlled by mechanical idle- roller governed slipping clutches. The electrially switched rewind was quite rapid and the tape was removed from the audio heads, but fast forward was just done by putting the motor into a high forward speed (at slightly over 30 I.P.S.), though this was similar to the way Nagra did things. A feature of the Stellavox was the way that it smoothly moved the pinch and flutter rollers into and away from the run position. This was done by a beautifully engineered sectored gear mechanism driven from the capstan shaft. Of course no pressure pads were used. |
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This is the underside of the supply reel hub area, with pivoting brake lever and rather fine red
felt brake 'shoe'. Hold-back tension is controlled by the pivoting arm of the supply tension roller above the deck plate (out of shot at the left of the picture) 'pulling' on one end of the brake lever via the red sleeved wire and pulley (bottom centre). This varies the amount of breaking force applied to the shoe by a helical tension spring. The engineering aspects of this machine are simple and nicely done. For example see also the underside of the tape counter below: |
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Above is the drive/capstan motor looking towards the main function control switch. The quality of
components is every bit as good as those used in the Nagra, perhaps better in some places. I like that spiral earth wire onto the motor casing.
Below is the underside of the rather nice cast plug-in head block 'module'.
These easily changed though expensive, these self-contained units came in a number of favours
depending on the format the machine would be working with (mono, stereo, half or full track, music mastering, film recording etc), tape speed (and thus equalization) and tape type (bias level). The idea was that while the machine's 'mainframe' had indeed 4 switched motor speeds, you actually changed the head blocks to change tape speed or tape type.
This was very simple and elegant and it avoided what might prove to be expensive and
embarrassing mix ups (the BBC completely removed the speed change system on their Uhers for the same reasons), but only if you had the cash to afford the additional head blocks at around £600 a time. Though the professional user would perhaps need only one or two modules; film sound recording was standardized at 7.5 inches per second, and music recording 15. Tape was usually standardized on one specific type and obtained in bulk, so there was no need to be able to change bias easily. And of course many an untrained 'twiddler' has mucked up bias and equalization settings on otherwise perfectly good machines - I should know!
With a power supply the Stellavox could even work at 30 I.P.S., and there was a 10 Inch reel
adapter to take advantage of the higher speeds, you would of course need the correct head block. Sadly though Stellavox never did sort out their large reel adapter which was in in comparison to the superb Nagra version, was rather a joke. |
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SU8 Interior
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But the machine is very compact, and does have a fairly significant amount of conventional
wiring inside. I once used to wire medical electronics for a living, and can only look at the Stellavox's internal 'spaghetti with some respect for those who knitted it all together (much better done though than the rat's nest to be found in much domestic electronics). And admittedly also with some concern if ever I had to do some serious fault finding in there... Yes the electronics is mostly modular plug in units, but what about the rest of it? Mind you the Nagra is also looks quite involved as well... |
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Rather more modular internally in comparison to the Nagra, most of the electronics are built
inside a number of plug-in screened metal cans. There is a large and complex mother board fixed directly under the deck plate, and these various screened modules plug into best quality gold- plated edge connectors. The modules are securely held in place by the foam lined bottom cover. The Stellavox was appreciably smaller and more compact than the equivalent Nagra portable, and therefore was rather more 'busy' inside, and probably something of a challenge to fault find and repair. The early electronic modules were encapsulated in resin and had to be returned to the factory for replacement, but the resin was left out of the later machines. Apart from the theoretically increased reliability of encapsulation, it was reputed that Mr Quellet was very proud of his circuitry and understandably did not wish his good work to be easily acquired by competitors. And I imagine that that is the reason that most electronics are covered with resin...
My own general impression is that the Stellavox seems rather stronger and more 'developed' than
the Nagra, and is in some ways rather nicer and more 'finished'. It certianly looks much less of a 'Meccano set'. But as these machines were very serious work tools and not jewellry, it could be argued that function, reliability and ease of servicing were far more important than look. |
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This is an inverted view of the MSP head block, which was fitted to the Stellavox SU8 and SP8
TC. It is switchable to work with mono 'Neopilot', stereo 'Synchrotone' and mono 'Synchrotone'. The Neopilot/Synchrotone heads (brass coloured ones in the picture) can also be used to record/replay time code. Without the exotic Ruby tape guides of the Nagra, the three stainless steel versions used in the Sellavox also seem fairly adiquate, perhaps one might like to compare this head assembly with the Nagra T-Audio head block. Below is a view of the Stellavox head block with the top cover removed. The presets are for equlization and record level adjustment. |
