In Reply to: RE: 26 tube filament ripple posted by sony6060 on January 27, 2017 at 21:24:13:
Sure - you can just use chokes in filament bias. Thomas Mayer does just that and he was the guy the popularised filament bias in the audio community. Look at his site Vinylsavor.But I still prefer a combination of Rod's regs and choke input. I don't think you can go too far towards overkill with filament bias. You really need a smooth supply. And Rod's regs are also about impedance matching, which is an added benefit.
As for LT1085 regs, they can be a bit noisy and Rod's regs are much more evolved with better parts. They're pretty cheap as well - really worth using. He's now on the 7th evolution of his regs. See Lyrima.com
The best 26 design currently is probably Ale Moglia's, as shown - with filament bias. See Bartolo Valves website. His Gyrator is really good. And again, like Rod's regs comes on an easy to build PCB. Cheap and well worth using. You can see from the 850mA supply that the 26 is used in "starved filament" mode which can give gains in lower distortion and longer tube life. I've been building 26 preamps since 2009, and I would use the gyrator in preference to an OPT. More detail and generally a more immediate sound.
The 26 circuit is in essence extremely simple. But the gyrator and Rod's filament regs - while a lot more complex than other options in terms of parts count, though as above on handy PCBs - really brings the last ounce of excellence out of the 26. The alternative is the 01A which is almost identical to the circuit shown and which you can find on Ale's site as 01A Gen 2 preamp. That's the one I use myself and Ale prefers it too.
Edits: 01/28/17 01/28/17 01/28/17
This post is made possible by the generous support of people like you and our sponsors:
Follow Ups
- Yes - Thomas Mayer uses choke supplies - andy evans 01:56:26 01/28/17 (0)