Bill and Will's Synth Construction
Matching Transistors

Here's how we matched transistors using the MOOG Transistor Testing circuit we built per the thread on the electro-music.com forum describing the matching technique from the Minimoog manual.

It was an interesting little process. Tedious - kind-of. Time-consuming - yeah, but I'm used to tedium (it was harder on Will).

We started out measuring the 547 NPN and 557 PNP transistors for the EMS Diode Filter. Everything we've read warns about temperature sensitivity - so we used pliers to handle the transistors into the tester. Even so, in many cases, we waited 30 or so seconds for the millivolt measurement to stabilize.

Warmer results in a lower measurement. As an experiment, after obtaining a stable measurement, we would grab the transistor with our fingers and immediately the measurement would plummet 10 or so millivolts. After about five seconds we released our grip and then it would take five or more minutes to return to the prior measurement.

We even considered the "Observer Effect" and "Schrödinger's cat" - leaving the room - not even thinking about the transistor - for half an hour and jumping back in suddenly to see if the measurement changed before the transistor knew we were in the room. We tried singing to it - sending it loving or angry thoughts. No effect.

But when we breathed on it from six inches away, we could lower the measurement by a miillivolt.  Sensitive little guys and gals - just not to thoughts and emotions - or at least not measurably in volts.

We had a magic smoke experience - one of the PNPs gave up it's spirit rather odiferously and visibly. We could find no reason for it. There had been no warning - no suicide note - no history of depression - although it was a bit of a loner.

Measuring the Transistors

PNP transistors:

NPN transistors:

We sorted them into little cups as we tested them:

Here's how the transistors stacked up:

We bagged them up for later: