Shall I say that DX7s need no introduction? Well there are more web pages than I’d try to count about them, so if you need an introduction, go get it.

The original DX7 to me was that sleek thing with membrane keys which, in 1984, someone I knew got hold of, praised the capabilities of effusively, and left me with unattended for a few minutes. Being sort of used to simple analogue synths, I thought, well, let’s see? And pressed a few membranes, managing to change what it was doing out of all recognition in a few short seconds, with no idea how to change it back. Up DX7 creek without a manual, nor any clue how I got there. I thought it would be best to just leave it rather than make things worse. Leave it at speed, before its owner returned. I never saw it again.

Clearly this memory has stayed with me. In fact it’s probably the exact reason why I prefer proper synthesisers, i.e. ones with a control for each parameter, that you can see, adjust, and then put back where you found it. Nevertheless, I’ve always thought that one day I would like to find out how to use the thing. One of my own, without the risk of wrecking someone else’s setup again.

So, here we have one of the DX7 updates, a DX7S, from 1987 I think, and in need of some attention. I’m not sure what’s wrong with it, but battery replacement is apparently wanted. Hopefully not much more than that.

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A summary of investigations into Hohner analogue electronic pianos and string machines. (To date. Not planning any updates at this point, but you never know.)

HIPs and Strings

Ephemeral photos of most of these instruments turn up occasionally in online sales; longer-term linkable references are given below. Different branding seems to have been used by Hohner in different national markets, however, so even if this list is comprehensive technically (which I can’t guarantee), there may be alternative names in some parts.

Drawings below are sketches intended to highlight the distinguishing characteristics of the instruments, rather than be exhaustively accurate. Or get the perspective right or anything. Slider caps in particular may vary even in the same model; so I’m not trying too hard to represent the exact types found — where they haven’t all vanished or been replaced.

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Side by side shots of the Korg SD delays, the -200 opened for comparison while I convert the -400 for 240V.

The SD-400 (brown) has the bypass, short/long delay option, swell, and ADT settings, but no tone control. I haven’t quite worked out which I prefer; the -400 seems to have a fixed filter; it’s smoother than the SD-200 (silver) on simple delays, unless you turn the -200 tone down. Maybe the -200 is better for harsher delays. The only online technical information I’ve found for them suggests they have roughly the same range of 30–400ms for the -200 and 25–400ms for the -400. Presumably the -400 should go lower on its Short setting, but it’s the same as the -200 on its Long setting. In practice, comparing these two, the -400 gets up to around 10% longer delay, but that could just be a calibration thing on one of them.

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In spite of the apparent quietness of the last few months, I’ve been working on synths in between other things; in particular on the Vermona. After the initial post, in the absence of any written technical information, I was planning to draw my own circuit diagrams. Actually I did some board drawings, because that’s easier when all you have are last year’s photos and enough space to sit.  ^[1] A couple of weeks ago, this was complicated by my discovery of a new (I think) and rather great old manuals page at vermona.com, which includes circuit schematics ^[2] for both versions of the Synth. The full update I was slowly working on will be rewritten in the light of the new information . . . but it will be better. For now, here are my drawings — with the component numbering brought into line with the schematics, as far as possible. (My earlier numbering was entirely arbitrary as there is no screening on the boards.)

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MS-10s need no introduction, so — here’s one. Probably from about 1980 but I haven’t got it far enough apart to look for component dates.

This arrived in a purportedly “Pro-Serviced” state. In contrast to my many other gripes on the topic, I must note that it was well-packed, and arrived faster than the estimated earliest date. Also in near-perfect physical condition, which for me is a first, for a synth without a case. So would buy again? Maybe. It doesn’t even smell bad. No rotting food or wildlife, no decaying components, no decades of garage-storage and no undead tobacco. ^[1]

But I’d like to know what “Pro-Serviced” means. Perhaps that this time I’m paying someone to do the things I would normally do myself? This clearly doesn’t include cleaning, past a cursory wipe; there’s a lot of dust ingrained on the modwheel and at the back of the keys.

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