Any opinion on this DIY tube preamp design?
strider
Posts: 2,568
Looking for the next project, kicking around ideas with my electrical engineer father-in-law, he suggested this preamp as a good design:
http://diyaudioprojects.com/Tubes/Universal-Tube-Preamplifier/
Anybody have an opinion? I'd build it as it sits, with the exception of having 3 inputs instead of 1. Have already built a tube preamp from a kit, but I think I could pull off a better execution now.
http://diyaudioprojects.com/Tubes/Universal-Tube-Preamplifier/
Anybody have an opinion? I'd build it as it sits, with the exception of having 3 inputs instead of 1. Have already built a tube preamp from a kit, but I think I could pull off a better execution now.
Wristwatch--->Crisco
Post edited by strider on
Comments
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Your father in law's an EE, and you're asking us?!?
;-)
My decidedly nonprofessional opinion - it looks OK; nice to see a choke in the P/S... but the 12AX7 is a (very) high-gain triode and it doesn't have the finesse of lots of other tubes for audio - it's a pretty brute-force solution to the 'problem' unless you really need lots of gain (e.g., MM phono preamp/EQ)... and even then there are, arguably, better-sounding choices.
Adding inputs is a trivial matter - either buy a good stereo switch and wire it up (use good coax for the interconnections) or just cheap out & buy a source input selector like this one:
http://www.mcmelectronics.com/product/50-6170
EDIT: It'd be worth adding a high-quality pot, stepped attenuator, or transformer or autoformer volume control instead of what looks like a pretty generic looking attenuator pot in the photos (I didn't actually look for a BOM for the preamp, so my apologies if I am besmirching what's actually a decent pot).
more at:
http://www.mcmelectronics.com/browse/Source-Selectors/0000000292 -
He understands an electrical circuit backwards, forwards, upside down. Their application WRT audiophile endeavors, not so much. For instance, he took a look at my PassDIY F5 and asked me what 12 year old designed it. Ouch.Wristwatch--->Crisco
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well - in fairness, circuit designers are generally interested in performance, efficiency, low parts count/economy, and elegance of design. Thus, e.g., pentodes and push-pull amplifier topologies trumped triode amplifiers and single-ended topologies many, many years ago. On paper, a single-ended amplifier using a direct-heated triode output stage with no negative feedback is a brutally inefficient and brute-force way to amplify an audio signal. But... we don't listen to paper.
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Nail-head.
He took a look at that Class A amp with it's 20 lbs of heat sinks, toroidal the size of cantaloupe, and parts list littered with devices that are no longer available and I thought his head was going to explode.mhardy6647 wrote: »My decidedly nonprofessional opinion - it looks OK; nice to see a choke in the P/S... but the 12AX7 is a (very) high-gain triode and it doesn't have the finesse of lots of other tubes for audio - it's a pretty brute-force solution to the 'problem' unless you really need lots of gain (e.g., MM phono preamp/EQ)... and even then there are, arguably, better-sounding choices.
Are any of the other variants of the 12A*7 better? The designer says the circuit can use 12AU7, 12AV7, 12AY7, and 12AT7/12AZ7 in addition to 12AX7.Wristwatch--->Crisco -
For a very technical design paper.
"His Master's Noise: A Thoroughly Modern Tube Phono Preamp"
Stuart Yaniger (SY)
http://www.diyaudio.com/forums/diyaudio-com-articles/163570-his-masters-noise-thoroughly-modern-tube-phono-preamp.html -
Arguably the lower amplification 9-pin miniature tubes may sound 'sweeter' (e.g., the 12AU7 or 12AT7) than the 12AX7... but the old-school 6SN7 and 6SL7 octals (and their earlier ancestors; the 6SN7 dual-triode traces back to the 76 single-triode and thence, I think, all the way back to the 27.) are fantastic small signal amplifier tubes.
Here's an interesting link I just stumbled upon; offered strictly "as is" (i.e., not fact-checked by me!):
http://www.nutshellhifi.com/triode4.htmlSpeedskater wrote: »For a very technical design paper.
"His Master's Noise: A Thoroughly Modern Tube Phono Preamp"
Stuart Yaniger (SY)
http://www.diyaudio.com/forums/diyaudio-com-articles/163570-his-masters-noise-thoroughly-modern-tube-phono-preamp.html
I use 6SL7s in the SE 2A3 (power) amp I use (a slightly modified version of the JE Labs/Angela Labs "Simple 2A3" design)as drivers and I luvs 'em to death...
newamp by mhardy6647, on Flickr
