sound practices reading club /26

…and now for something completely different. Today’s system can be found in sound practices issue 14, Homebrewer of the month, Ed Billeci of Portland, OR. I presume it was written up by Joe Roberts. In it, we get to meet—before all—the 3-story 212 amplifiers, but also the horn speaker(s) and the one of a kind turntable.

teaser quote: ‘Very few searchers are hard-bitten enough to stretch out quite so far in pursuit of their personal audio vision. Really, only a handful of audio hobbyists progress to the point where they would even know they wanted something like this—let alone wanting it so bad enough to make it a reality?’

my take

Now the 212 amps hog all the attention and this being the systems topic we are dealing with, that may actually point at an imbalance in Ed’s system (or at an error of judgement, selecting this as a systems article). No matter how cool, the amplifier seems to be a remnant from a previous system, designed for driving power-hungry planar speakers. So where is the rub, you say. Well, there is always extra levels of complicity and compromise involved, in getting in the tens-of-watts league of single ended output power. A first compromise that comes to my mind is the output transformer on this amp: high impedance (212 has 1K9 plate resistance) and high dc current and a large core size for high power handling? A transformer winders’ nightmare.

Meanwhile, what is cool is Ed manufacturing some of his own components, like fibre insulated silver wire and hand-rolled copper caps. A commitment to quality beyond the snake oil prices.

So is Ed listening in mono? I always thought so over the years. But careful reading shows no explicit mention of that. The cartridge on that very charismatic turntable certainly is mono. And the description of the speaker components is curiously singularly phrased. ‘Horns’ could just mean LF + HF horn. I always imagined (in awe) that Ed used the pair of 212 amps to bi-amp a mono horn system.

Now about the ’32 pieces of iron.’ OK, that is 16 per amp, but it is not as outrageous as it may sound. Just thinking of a B+ for the 212 and one for the driver tube, a bias supply and a filament DC supply (both for the 212). Building all of these ‘properly,’ involving a power transformer and 2 chokes for each, gets us to 12 pieces of iron and with an OPT and an interstage transformer we have two more. It simply adds up, no, when you do not cut corners on your supplies?

pop quiz: ‘twenty-watters with lots and lots of headroom’? The 212 with 275 watts plate dissipation will put out 55 watts max in class A1 in praxis (20% rule). 55W is 4.4dB more than 20 watts—a subtle difference—although it looks like a lot more than that on paper.

bonus tracks

Check out the 212 data sheet. Not just the shock and awe of 13+ inches and 84 watts of filament glow, but also the linearity of this (gentle) giant.

Now go and read the article, see you next week.