SFAF RAM School of Audio Educational Initiative Class - Basic Lab Techniques
LOTS OF FUN ON A RAINY DAY, by Ori Mizrahi
Saturday 12/3 was one long cloudy and rainy day. On a day like that you don’t have many choices. You can sit at home and watch the US soccer team knocked out of the World Cup by Holland. Or get on some audio forum where you are sure to get a headache trying to figure out what’s real and who’s a big zero with a very active keyboard… You can watch the Trump Diaries, but that’s a bigger headache yet… Or you could have taken the chance and joined our SFAF class in San Jose.
Take a chance? Well, the class description talked about ohm’s law, multimeters, scopes and soldering irons. That kind of topics can give you a headache in no time. But not on this Saturday!
SFAF started the educational classes a while back but there is a reason why we call them “learn and listen”. All the classes so far were serious, but did not skimp on the FUN FACTOR!
We don’t have a mandatory curriculum or a board of supervisors. If we find an interesting topic, we expand on it and forget the published agenda. Add to that the afternoon listening session that always brings in interesting gear, esoteric (to some extent) music and last-minute unscheduled changes to the “program”, and you are guaranteed to come out of the long day tired but nevertheless happy…
This class was held once again on the ZAG company premises, thanks to Jim Hunton. I can attest to how busy Jim was in the last week. I went twice to the office and saw him only for a split second. Jim took the time on Friday after 5PM to set up for the event and showed up early in the morning in pouring rain to open the door. I can’t thank him enough!
GETTING TECHNICAL
Despite the heavy rain, I was pleased to see all the people that registered to the class, and they were not all San Jose residents… The agenda listed ohm’s law and using a multimeter for the first one hour. We started with some simple calculations, but that is quite dry stuff. I figured that a class like this should focus on Audio and improvise here and there. At the conclusion of this class, we covered DC vs AC, the different “kinds” of AC (power outlet, audio signal) and the concept of a hybrid signal: an AC component “riding” on a large DC component. If you’re reading these terms for the first time in your life they probably sound like gibberish, but it’s amazing when you realize how simple these principles are.
We touched on the practicality of a DC “bias” in tube and transistor circuits, to keep the amplifying device in a linear mode of operation. We even talked a little about capacitors in the signal path and RC time constants, which determine to an extent the frequency response of an audio stage. To the best of my knowledge there were no rocket scientists in the room but I believe they all actually comprehended the light theory. It makes sense why circuits are designed the way they are if you understand the basics!
The class started a bit late and the topics of AC/DC and multimeters expanded beyond the very basic stuff, so we found ourselves at 11am ready for the next topic with only one hour left. The original agenda included a one hour introduction to signal generators and oscilloscopes, which I already decided to cut to 30 minutes due to time constraints, but then we had to make a choice: split one hour between the scopes and a very quick “hi and bye” soldering demo, or change the agenda. And change we did.
This is not the last class we’re running and it was more important to run a proper soldering demo and have at least half an hour of soldering lab. We used the soldering kits SFAS bought to solder a small audio level gadget with 10 LEDs that light up based on the level of audio at the input, pretty cool stuff…
At the same time, we used the multimeters, also supplied by SFAF, to check component values. It was the right decision to cut down on theory and do some hands-on lab work. We had a group with various experience levels, from people that put together kits to a retired doctor that can probably cut you open with a scalpel in two seconds but has never held a soldering iron in his (long) life… Jim is confident enough now to try new caps in his $$$ speakers.
At the end of the morning class, I felt that the class had achieved its primary goals and then some. People actually understood more about amplifier circuits to the point that you cannot sell them rumors and myths anymore. They were asking serious questions during the class and I have no doubt they will use what they learned for a long time. In addition, nobody was electrocuted or burned by a hot soldering tip… I’d call that success!