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In Reply to: What the 45 does best posted by njjohn on March 2, 2007 at 16:43:04:
I am very currious about the 45 amp. Since you brought it up :Can you suggest three 45 amps worth checking out? These can be kits, used, or new production.
Can you recommend a minimum efficiency requirement for speakers? Let's assume a speaker with a reasonable impedance curve (an uncomplicated load) and a medium size listening space (13'x20'x8'). Let's also say that you can easily get the average volume up to 90-93dB on the spl meter. That's loud enough for me.Can you name three places that consistently sell 45 tubes for replacement? Are they hard to come by?
Follow Ups:
I cannot say I am all that familar with what is out there. My guess it that it is an open field. I think the territory is more new and open than people are giving credit too.The opts are quite important, as are the various possible driver tubes and the types that they are such as dht, pentode, and idht, and various other ingredients that can be combined in so many ways. And it all interacts with the rest of the system.
I don't know how much exploration has been done so far. But the 45 does shine through as described by someone as very linear, and I would describe it as the 'reality tube'. It is worth the pursuit of getting the highest possible effeciency in speakers for it.
Some of the broadest classifications I can do is what are the opts, driver tubes, ac on all of the filaments vs. on some, level of simplicity, brand of 45 tube, etc.
I think it's anyone's ballgame who can tease out all these variables the best, or who can luck into it. There are apparently some master builders out there, and/or some great circuits and possibilities.
It would seem almost impossible to buy something without extended listening to it. The 45 is not so easy to get right, say like a 2a3 amp, or it can be pulled in various directions.
It can kind of be like the rest of audio. It could take some time to find the best, or what one likes the best, and/or complete satisfaction.
Bottlehead Paramour II configured for 45s with iron and cap upgrade.100 dB.
Sophia 45s.
You could spend $2300 on the Yamamoto A-108 kit a friend has(from Venus Hi-Fi), $1200 on the Welborne DRD-45 which I had and didn't like much with its 6N1P driver, or $1200 in parts on the Simple 45 that I built and am nuts about.With help from pal Steve Brown we substituted a Gary Pimm design CCS and 5AR4 rectification to tame the 500 volt start-up surge. EML makes a great 45 but my choice are National Union engraved base I've found on E-Bay in the $150/pair range. Crystal clear mids and treble; tight, if not authoritative bass.
In my 24x15x8 room it drives 97 dB BR/horn speakers to 90 dB or so with okay headroom. For head-banging or really loud symphonic you'll want to get 100dB or more sensitivity.
"...In research as in life one is far more likely to find what one looks for than what one neglects."
-The Modern Researcher; Jacques Barzun & Henry Graff
Harcourt Brace Jovanovitch, Inc. third edition 1977
Hello,
Nice amp. Could you share a schematic of the version of CCS you are using in the 'Simple 45'?
I've never tried to link a picture before, lets see how this works. At any rate, the work on the CCS design is a credit to Gary Pimm, who used to have a site with all this, but I have no idea what happened to it, or to him. Hope he checks back in with all of us sometime soon.I built Bill's CCS on perf board from Radio Shack. The parts are easy to source from Mouser or Digikey. The set resistor R1, is figured by (IIRC) 21/I. In the case of this amp, you want to have 10ma so I becomes 200 ohms or so. It is adjustable via the pot. We go for 150v on the driver plate. This CCS is way fancier than what you need, but has outstanding performance.
I'll second Square's comments about the outstanding quality of this amp, and I think the nod goes to 3 factors that come together nicely here: the 45 itself, the overall quality of iron (MQ Parafeed stuff), and the simplicity of the design - heck there are more parts in the CCS than the rest of the whole amp! I'd also strongly support the idea of using a valve rectifier. I've heard it with both SS and Tube rectifier (Damper diodes, 5AR4 and 5U4) and prefer every tube variation we found to the SS stuff. It also seems to be much easier on those poor old 45's to ramp up the HV a bit more slowly.
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