©2001 Jeremy Epstein. No reproduction, retransmission or web distibution without prior written permission.
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The "Darling" amplifier experiments
After hearing about Bob Danielak's experiments with cheap, fun triode amps using the 1626 output tube for a while, I wrote to him and we began a long process of experimentation, some done in tandem, some seperately. His original "Darling" design, published in the pages of Sound Practices magazine, used 8532 (a high mu single small-signal triode) to drive a single 1626 per channel.
1626 is an indirectly heated power triode which was developed for ship-to-shore radio transmitter service. Using a single 1626 per channel power outputs are on the order of 3/4W, or as Bob likes to put it "seven hundred and fifty milliwatts!"
Bob Danielak maintains a page with great information about the "Darling" series, including versions done by some other experimenters, and this page shows some of the things we came up with together.
I was using speakers of moderate efficiency at the time and I was skeptical about the results I would get using such a small power amp, so we started discussing the idea of using two 1626's per channel in a parallel/single ended arrangement. I built up several experiments including a transformer phase-splitter push-pull version, an IT coupled version, and a few more. I ended up with the version shown here.
Later on I learned how to make this amp in a direct-coupled version, which was pretty cool. This amp has recently been modified to use the "Free Lunch" topology, I will draw up a schematic for that one at some point.
I wrote an article (intended for Sound Practices magazine but never published) about our ongoing lovefest with this basic design, and you can see it here.
I just want to mention two things here:
Bob always ends like this: