And now, the actual context of reading club 21. Homebrewer of the Month, Bruce Berman of Long Island, NY from sound practices issue 13. I again presume that it was written up by Joe Roberts. In contrast with last week, there is more in the pictures and diagram than in the words. But worth studying nonetheless.
teaser quote: ‘A system like this is one man’s audio dream made real through hard work, […] he turned a pile of old cast off junk and raw materials into a custom high-performance music system unlike anything you can buy anywhere.’
my take
While checking out the article I noticed a paradox. Still today, more than 13 years after publishing, it is impossible to to buy a system like this off the peg. Yes, you can go out and buy good turntables; single-ended preamps and power amps using octal tubes, 300Bs and external power supplies, and you can buy horn speakers. However Bruce’s system has a quality in design and implementation that beats anything from the high-end store: tube-rectification everywhere; plenty of chokes in the power supply and not weenie high-DCR types; banks of oil caps. The combination of the Altec speaker components with the custom, high-class crossover is beyond what can come economically out of a factory. You will have to build it yourself or pay a craftsman to build it for you.
So far, so special. But now for the paradox. The system we see here is also incredibly orthodox, in ultra-fi terms. Although I am sure that it is very musical, has ‘lifetime’ value and surely show the hand of its creator, it is also wholly conventional, even a bit of a yawn, in its conception. So special, yet so boring. Well OK, the WE 262B is special enough that I had to go and look it up, over at the Western Electric support page.
Checking the out diagram from a system point of view, I noticed that the modular preamp strategy as described by Bruce has resulted in what looks like a sub-optimal signal path for phono. Assuming that the 6J5s in the phono preamp are kathode followers, there are still six cascaded tubes with gain between the cartridge and the grid of the 300B and that is one tube too many.
Sorting it out involves designing the line preamp and the power amp gain stages together so that there is the right range of gain for the DAC, tuner and the tape deck. After that the gain design brief for the phono preamp is clear. Thinking a bit more we should look for ways how the phono amp can be interfaced in a privileged way with the line amp, avoiding the need for a kathode follower at the end of the phono pre. Looks like Joseph did something like that last week. Or we could go further and make the phono preamp even more privileged and interface it directly to the power amps, giving it its own volume control and bypassing the line preamp altogether.
Now go and read the article, see you next week.
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