I got this, ready built, because I needed a simple switching function for another Eurorack module and it was being sold cheaper than any actual switching module or combination that should do it, and hey another sequencer will always be handy. So here’s some notes:

• There’s no start / stop button(s) or input(s). It can be stopped by plugging a dummy plug into the clock input but that’s yer lot. This seriously restricts its utility because you can’t easily get it to work in sync with other devices or even start it manually at a desired time. (But it occurs to me that you could mount a switch on the end of a dummy plug?)
• The sequencer doesn’t seem to respond to V‑Trig signals at the clock input in the way I’d like; that is, it resets to 0V but most input sources I use start high. Inverting the input fixes that, but it then starts out of step so anything it’s controlling may need to be reset to the previous step.
• The clock input is a bit finicky in other ways; not all clock signals will drive it; perhaps it needs a slightly higher voltage. The Doepfer dividers manage it, some other modules don’t. (This is independent of polarity.)
• Sometimes it steps the outputs without stepping the LEDs but I haven’t worked out how that was happening, and by the time I got it to work it wasn’t happening any more.
• There is a manual available from Erica but it’s a build-it manual and is very short on actual functional description of the finished module, so all the above points had to be worked out slowly and uncertainly rather than just read, and remain a little tentative.

With that worked out, it’s doing the job as intended but if I’m going to use it for the usual range of purposes one might use a sequencer, a useful mod might be to put a switch on the internal clock signal. And a reset switch to start it high if need be. For the time being I’m using an external inverter on the input.

(Update, 2024-09-17:) One other unexpected detail that’s causing confusion is that it seems somehow to be passing an extra pulse through to GATE OUT from CLK IN at the end of an active step. In other words, either an active switch appears to produce a trigger pulse at the start and end of the step, or, since it happens at the end of any sequence of active gates too, the subsequent inactive switch also produces a pulse. This does not happen when driven by the internal clock. For current purposes this is kind of useful if you know it’s there but I can see it being a problem otherwise.

Further investigation shows something about the nature of the issue. The connected devices (sequential switches) return to state 1 (out of 2) under specific conditions. They don’t respond in that way to either the Erica’s internal clock (GATE OUT with no input), or to the direct input signal (which as you may recall is inverted), nor to the pre-inversion signal, nor to the signals as passed through the Erica’s CLK OUT socket, nor to its GATE OUT when the input is not inverted. I should note that all this still obtains when the output devices have nothing connected other than the various step inputs tested.

After much confusion I was finally able to find the output pulse with the oscilloscope. This is 6V high and about 2µs wide at the top. Enough to trigger most output devices. (Though not all.) It is produced when a new input step occurs, but only if the next gate switch is off.

So it’s a combination of the NOT gate (Doepfer A166) and the Erica. I imagine this is to do with different response times in different devices’ components.

My MS‑10 has been behaving a little poorly recently, with the EG release time fluctuating to a gradually growing degree. So I’m going to have a look at it. First, have a look at the service manual as this failure seems likely to be a misbehaving capacitor. And yes, there’s a 6µ8 Tantalum cap (C35) on the release stage, so that’s the main suspect. I hear some bad things about Tantalums, but I’ve never had one fail before. Anyhow, I did have the thing apart for cleaning when I got it but didn’t take the PCBs out as it involves a fair bit of unscrewing things. So this is my first look at the relevant board (KLM-126c).

(Picture taken after repair.)

Checking C35 in-circuit, difficult to be certain but nothing obvious wrong.

more →

Quick note about a quick repair.

The SQ‑64 is a simple-looking but rather complicated digital sequencer which can receive and send CV/Gate/Trigger, Korg Sync, and MIDI signals, which is intrinsically a 64-step sequencer and which can chain sequences etc. It’s handy for translating analogue timing signals and setting up sequences for MIDI devices which can’t take a simple external clock, and so on. It has some limitations as a controller of analogue synthesisers however, but that’s not the topic today.

This SQ‑64 was I think bought new about two years ago, not long after they came out, and has developed a fault, so I’m going to investigate. The fault is that the eighth top row sequence button is activating intermittently without being pressed, which adds unintended gates to a sequence and prevents the user accessing additional functions in some modes because this button is interpreted as being pressed and having priority over other things, somehow.

more →

I had occasion a few days ago to install MacOS 10.12 on an old laptop, and encountered an error message at what seemed to be the end of the process. Spent half an hour trying to see whether this was a known problem. It’s a little confusing because this was a fresh installation rather than an upgrade, and I found several references to failure messages in upgrades and ideas for how to fix the problem, as this was apparently quite common with 10.12, but not for new install.

Armed with a few very unlikely seeming ideas I restarted the machine intending to wipe the drive and start again . . . and then realised that the error message seemed to have come up at the point where the installer tried to load a message to say, we’re done for now and please restart to complete the installation. And it completed the installation. This took a while but it’s now up and running.

(I say it took a while but really it took far less time than it used to, swapping floppy disks in and out. It just seemed longer since there was nothing to do but watch.)

more →

I managed to lay my hands on a secondhand Behringer 2600 ‘Gray Meanie’. I’ve never been fortunate enough to have a go on an original ARP . . . any original ARP . . . but from what I’ve seen and heard this seems to be sonically quite close to the original, but smaller, 19″ rackmountable, and even when new, significantly cheaper than any of the older or more recent clones of the ARP 2600. And it has some extra features. So they are perhaps becoming popular.

There are more reviews and videos of the different versions of this than I can count; so many that I’d never get time to play the thing if I watched them all. So I’m not going to cover the detail, just note a few things that come up and see how it works out.

Once past the first hump or two of working out which things have to be turned up to make sounds, this synth seems to have lots of things waiting to be found. Still, after a couple of days with it, I’m a little disappointed to have not found more. Compared to other synths . . . but that doesn’t mean there’s no more there; it’s just how to get at it. In particular the Ring Mod is surprisingly uninteresting compared to others I’ve used; but maybe there’s more options I haven’t tried. The combination of the three VCOs synced is very interesting though. I also find that it’s capable of making some very nice bass tones which don’t reproduce well on small speakers. For which reason, this first sample video I’m doing is best listened to with good headphones or perhaps a PA.

The KM‑50 is a simple metronome made by Korg in around 1983–84. I have never seen one in real life, or photographs apart from catalogues from the period. And now this.

It’s a very basic device, simpler than the earlier Korg RT‑10, consisting of a timing pulse with a higher-frequency sound as a bar pulse. It also has a needle timing indicator like a miniature physical metronome. The timing range is set with a rotary switch, from 40 to 208bpm. The bar pulse can be from 2/4 to 6/4 or off. And it has a tuning pitch, which varies from an unusual 439 to 444Hz, the frequency set with the same linear switch as the bar pulse. The frequency is pretty accurate but wavers very slightly. It takes 9V DC external power or can be powered by a battery. (Unusually for products of this age it seems to work quite well with a rechargeable battery.)

Like many other metronomes, the sound it makes from its built-in speaker is quite irritating and I doubt I would be able to focus on music with that going on. Unfortunately, while the sound can operate without the needle, the sound can’t be switched off separately, unless a cable is plugged into its signal output. It has a 3·5mm TS jack for this, and this rather more interesting. Checked on the oscilloscope, the normal signal is a +8V rectangular pulse which fades out slightly at the end. The bar pulse seems to go through a resonant filter.

I won’t be using this as a metronome in the ordinary sense, but a stepped +8V pulse generator means a timing source that could be run into one or more synth clock inputs, with appropriate attenuation and/or inversion, and even though this seems extremely rare in the secondhand market, it was cheaper than the majority of simple Eurorack timing clocks I’ve seen. I don’t have any specific plans at the moment but it’ll probably be useful at some point.