Let us now praise famous analogs

credit where credit is due

First, a Mea Culpa. It should be pretty obvious that my preeminent love and passion is invested in DIY. By and large, I make my instruments myself*. I am not a craftsman. My work is not even remotely well crafted. All of my time and attention goes into the design, and in my heart of hearts I really find the process of actually building the damn thing rather tedious. This is why my heart really sinks when one of my contraptions breaks. There are few times during which I hate myself more than when I have to weed through my own mess to find a problem and fix it. The blame is all on me. I have no scapegoats. My two mentors: Rich O’Donnell and Grant Richter are meticulous craftsmen of the highest order, in addition to being brilliant and visionary designers.

But the fact that I suck at the craft of building electronics by no means blinds me to the myriad practical virtues and BEAUTY of a well-built machine. This essay resulted from the experience of checking and maintaining a well-built machine; one of my most-treasured ‘store-bought’ instruments, the Oberheim Xpander.

I was a newlywed in 1984, but I saved a little each month until I had enough to buy my Xpander new. I was enthralled with its capabilities then, and I remain so now, 40 years later. It’s design is brilliant and deep. It is capable of those sumptuous timbres for which Oberheims are justly famous. But beyond that, its self-triggering LFOs and Envelopes allow the programmer to design intricate patches that ‘play themselves’ and yield barrages of complex, kaleidoscopic motifs without requiring any external controls. It’s more fun than a barrel of monkeys. And I could wax loquacious about any of its feature for many paragraphs. But my theme here is workmanship.

It is important to keep in mind that the Xpander was designed in a very different era than our present one. (this being 2024). The Xpander was the first Oberheim designed to use the then brand new MIDI interface(!). The practice of storing patch data on computer media was still a couple of years beyond the leading edge of technology. The Xpander stored its patches using the then-common method of storing data as an FSK-coded audio tone on cassette-tape(!). Also, It utilizes an internal 3-Volt battery to retain its patch data when the power is off. My Xpander is 40 years old, and that battery is thus at least a 40 year old battery… it has been cycling power to the Xpander’s memory for nearly a half of a century. My Xpander is still working perfectly. But I grew concerned that my policy of ‘if it ain’t broke don’t fix it’ was going to outrun it’s aphoristic luck.

But before I could open up this revered instrument. Prudence demanded that I make damn sure I have a working backup of the patch-data on my Xpander. I have hundreds of hours invested in the design of those patches and it would be heartbreaking to lose all that work to a careless fumble with a screwdriver. As I mentioned earlier, the Xpander was designed before MIDI SyEx dumps to computer media were de rigeur**. The Xpander’s primary data backup method uses a coded audio tone that’s recorded and played-back on a standard cassette tape recorder. I have kept a 1980s Radio-Shack cassette recorder sealed-up in a box for exactly this purpose. But naturally it makes me nervous to unearth a Radio-Shack relic from 1984 and depend on it for the preservation of hundreds of hours of work. But Oberheim’s wisdom manifests in a utility on the Xpander that checks the cassette recording against the stored data and verifies that the data matches completely.

It works.

I made three cassette backups and all three of them verified exactly as the manual described. They don’t make ’em like they used to! And I must tip my hat to good ol’ Radio Shack too.

Now, armed with three verified backups in hand, I decided to open the hood, and test that battery. Here’s what I found:

The 40 year old, 3-volt battery in my Xpander measured at 3.115 volts….. wow!

The battery is soldered on to the circuit board. It is not designed to be replaced by the user. So this measurement is the nominal expected result. But I wonder if the designer imagined that his or her choice of methods and components would be tested fully four decades after it’s production. Intentions notwithstanding, I’m here to report that the design works. That 40-year old battery is still doing it’s job. Consider how this compares to the batteries in our much-younger smartphones or laptops.

Also, while I was inside the old beast I had an opportunity to confirm or refute a rumor. (Geek Alert!… This topic is pretty technical) It concerns the integrated circuit chips and how they are connected to the Xpander’s printed circuit boards.

There are hundreds of IC (integrated circuit) chips on the printed circuit boards (PCB) inside the Xpander. There are many ways that ICs can be electrically connected together. Each method has pros and cons.

One way is to solder the IC’s pins directly to the PCB. This method has the advantage of a very strong physical and electrical bond. The downsides are that the IC is subjected directly to the heat of the soldering process during installation and, that if the IC fails, multiple pins have to be UNsoldered, often simultaneously, in order to remove the failed IC and replace it. Unsoldering multiple solder joints is a difficult and messy process that requires specialized and expensive tools to do with minimal risk to the PCB.

An alternative method is to solder a CHIP-SOCKET to the PCB (instead of the chip itself) and insert the pins of the IC into the receptacles of the socket. The IC is then pressed into the socket by hand; sort of ‘snapped in’. Thus, the chip itself is never subjected to the heat of soldering. And if it fails, and needs to be replaced. it can be removed easily by hand. The downsides are that adding sockets adds cost. And the electrical connection of the IC pins to the socket receptacles is a potential point of failure if the receptacle’s contact with the IC pin is not solid and constant.

Oberheim used chip sockets in the Xpander and I have seen several reports on internet discussion forums complaining about the TYPE of sockets they used.

Socket housings are plastic. The housing has a hole for each pin of the chip. (see figure A) The receptacles are a metal part into which the chip pins are inserted. These receptacles can be of two types, “Double Leaf” in which the metal is folded in a way that squeezes the chip-pin on two sides, or “Single Leaf”, which has only a single fold and presses against only one side of the chip pin. Double Leaf sockets are slightly more expensive but are significantly more robust and reliable. Single Leaf sockets tend to be much less reliable and are used only in the cheapest equipment.

The Xpander has hundreds of ICs inside and thus, hundreds of sockets. The rumors I saw circulating claimed that, due to the number of sockets required by the design, that Oberheim economized by using the cheapest single-leaf sockets available. This rumor always concerned me and…. I can’t declare that every Xpander in existence is made exactly like mine but I can declare that all the sockets in MY Xpander are Double-Leaf, and they are in fine shape.

Case-Closed.

So Oberheim wrote a happy ending to this story. The old cassette-based backup scheme works. The memory-support battery still works. And the slanders against the chip sockets are rebuffed. All of this good news is still true nearly half a century after its production. My venerable store-bought flagship is still seaworthy and armed to the teeth! Three cheers for Oberheim and long-live the 1980s!

*And, for the record there are several commercially-made synth designs that I admire. Chief among them are Wiard and Makenoise.

**the Xpander was updated to be capable of MIDI SysEx in later software revisions but I never felt that the original cassette-based system was insufficient.