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I've been comtemplating dipping my toe into the Tube waters and was wondering if anyone has a few good books to recommend on the A to Zs of tube designs from the novice (but not dummy) level through evaluating design tradeoffs.
I've been cruising the net looking for tube designs and seem to have some strange attraction to building an 845-based SET amp (or 300Bs if I can find a good quality, high efficiency DIY speaker project).
Another interesting issue concerns the manner in which the input stage, driver stage, and output stages are coupled together (direct, RC, transformer). Anyone have any experienced-based insights here??
Thanks, Eric
I've been cruising the net looking for tube designs and seem to have some strange attraction to building an 845-based SET amp (or 300Bs if I can find a good quality, high efficiency DIY speaker project).
Another interesting issue concerns the manner in which the input stage, driver stage, and output stages are coupled together (direct, RC, transformer). Anyone have any experienced-based insights here??
Thanks, Eric
There's a lot of good info available,if you can wade through it all. One definite recommendation would be Beginner's Guide to Tube Audio Design by Bruce Rozenblit. It's hard to find just the right level of info. Some books assume you know nothing about electronics and start right from scratch. Some start at at a level that's too advanced and leave you in the dust with a bunch of formulas. I tend to learn by doing and I imagine there are others who feel the same. I would recommend finding a working piece of gear and study it. Get a schematic for it, see how the different parts of the circuit work together, maybe do some modifications. I think there's a lot to gained with this approach. The amp doesn't have to be anything fancy. I was given an old Fisher 400 receiver as the first piece of tube gear and things haven't quite been the same since. I learned more from the second piece - a Harman Kardon integrated amp. The other thing to do is look for used book stores, tag sales, and ham fests. Tube manuals and all kinds of interesting items can be found.
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Hi Eric,
If you haven't already seen it a great site for tubes is http://www.tubecad.com
Heaps of articles, design examples and theory.
I also reccommend the utilities written by the owner of the site.
TubeCAD and SE Amp CAD are great design aids for a relativly small outlay (see http://www.glass-ware.com).
Regards,
Tim
If you haven't already seen it a great site for tubes is http://www.tubecad.com
Heaps of articles, design examples and theory.
I also reccommend the utilities written by the owner of the site.
TubeCAD and SE Amp CAD are great design aids for a relativly small outlay (see http://www.glass-ware.com).
Regards,
Tim
Do a search for "tube" or "valve" at www.partsexpress.com and you should be able to find a bunch of tube amp design/construction books.
Good luck!
Good luck!
Eric said:
Eric,
the Radiotron Designer's Handbook covers all the theory and math and does so in an understandable way, atleast to me (mechanical engineer).
The Valley-Wallman book has only about 100 pp relevant to audio directly, but this is about most-advanced tube circuitry from the militrary labs which was never grossly published or used in audio circuits (solid state came in between
). This book is audiophile dynamite!Also easy to understand. The interesting chapter is "DC-coupled amplifiers".
TMK both books are avaible as reprint. The RDH 4 you also have good chances to find on ebay.
See to get your hands on oscillscope manuals from 50ies and 60ies Tektronix and Hewlett-Packard. If you see them, buy them and muse about the circuitry, there you find heaps of application of the circuitry from Valley / Wallman "Vacuum Tuibe Amplifers". Possible source: ebay, you local surplus store.
The Morgan Jones book is brilliant to get into tubes and avoids to load you with unnnecessary math. And the Allen Wright book gives you an extended insight in design philosphy, how to do and and why.
Concerning the interstage coupling : believe your own ears only !!!
How to do it proper is in the books, how it sounds to you is your taste.
You have to try it out yourself.
Point is: textbook theory and sonic relity are not the same here and if nowadays an author approaches the issue from the engineering tactics and theory side, he is tempted to condemn the theoretically inferior IS trannies to RC coupling with "perfect" caps of nowadays.
Both Morgan Jones and Allen Wright suffer from that.
Therefore I recommend the RDH 4thed from 1953 or so. Unbiased authors.
If you use RC coupling, be careful to use the best caps only for that.
You also can observe Dave Slagle's contributions on the SET forum, he is deep into use of IS trannies.
One warning: if you tend to complain about output trannie retail prices, then please avoid interstage trannies, they tend to cost atleast the same. Reason is: heaps of OPTs available but few ISTs were manufactured (bach then as well as today) and vintage stuff is rare.
Greets,
Bernhard
P.S.:
Some opionated hints
Most of the fellows of the Munich Triode Mafia however (including me) seem to prefer inductive coupling (IS trannnie) despite the theoretical drawbacks of such a device. Iron man Thomas Mayer has 9 signal transformers in his current system and it is one of the best systems I ever heard, with heaps of detail resolution the trannies usually are claimed to unable to produce and no perceivable distortion.
My own preamp design uses no coupling caps at all (input trannie, output trannie, the rest is dc-coupled), and my power amp design uses two "coupling caps" as I had to let a speaker XO happen somewhere and decided to do it right in the amp with 200V across the caps. However I plan to try out interstage trannies myself, got my hands on a beautiful pair of UTC LS-21.
Bernhard
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Eric,
for a start, better go with a 211. An 845 wants to see the driver swing 300V p-p and its grid is not of lowest capacitance. It will need either a complex driver circuitry like fancy 600V mu followers or cascodes with added cathode followers. A classic way would be something like a 300B with an interstage trannie.
A 211 needs 100V of swing. A task demanding enough for the 1st steps.
If you want to do it with style, look at the last issue of SoundPractices where iron man Thomas Mayer described his 211-driven 211.
Thomas is a buddy of mine, his amp is just gorgeous.
While typing this, I look at the UTC PP amp from 1949, using 845s, completely differential, having three 3 stages and 4 signal transformers tucked around them, yielding 100 Watts @5%THD.
I bet it sounded gorgeous, too.
Eric said:
Eric,
I was where you are about a year or so ago -- the books by Morgan, Rosenblitz, and Wright are the 3 i found most useful.
And there is no substitute for getting a cheap amp and figuring out how it is wired together. i found that a good amp to start with is an old console amp -- these can be had cheap and if you let the smoke out, it's not going to set you back too much.
And there is a TON of info on the web.
dave
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