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I'm sure you guys are tired of seeing pictures of my solid-state projects, but IMHO the well-rounded audio amateur doesn't restrict himself to any one technology. And the tube DIYer can always benefit from the experience gained playing with transistors.
This is my implementation of the "AAK" dual transistor output pair version of the SymAsym amplifier, described on diyAudio at the link below. When I started building solid-state amplifiers about 35 years ago, the fastest available output transistors had gain-bandwidth products on the order of 4MHz. The output devices in this amplifier have an Ft of 30Mhz. The result is nearly a decade more open-loop bandwidth to play with, giving all kinds of technical benefits.
Things that really strike me about this amp:
- It is dead quiet
- It has authoritative bass
- It throws a wide, deep soundstage
- Its treble is extended, detailed, smooth, and grain-free
- My wife likes the sound
I am now working on plans for a tube line preamp.
Edits: 04/01/12Follow Ups:
I remember looking at a Princeton Applied Research Model 113 preamplifier in about 1970 that had the almost exact topology;1st stage FET npn cascode, followed by a pnp bjt cascode, the Sziklai pair driver is new however. Wish we could have had an amp like this in 1970. Engineers indeed have a unique set of binders on. Ray
"The gift of imagination is a gift of the Gods imparted to a few who receive innumerable kicks in the a$$ their entire life." Le Corbusier (Charles-Édouard Jeanneret)
Transistors are cleaner performers now, easily. But they do not have tube tone. When you live without it like I have now, though, the "warmer" transistor amps with the clear detailing won't make you wondering much about the tube sound loss. If you wean off of tubes, which is hard when you get to like them.
Going in new directions (your own frontiers) is a more exciting way to live.
I have no strong argument with what you say, but I do think it is specious to talk about amplifiers in isolation from the speakers they have to drive. For a low efficiency, low impedance electromagnetic speaker with multiple drivers (if you like that sort of thing), solid state has definite advantages. However, there are many other types of speakers where particular types of tube amplifiers sound best, to my ears. Too many discussions of the relative merits of this or that type of amplifier seem to proceed on the unspoken premise that we can hook up an amplifier directly to our brains. Not yet.
The amp should be a good fit for the speakers.
I have some Magnapan SMGc's . They sounded great with a Samson solid state push pull MOSFET PA amp. I think it was like 275W per channel.
With my Magnavox 2 way horns, much higher EF, a low powered SE tube amp is better fit and sound. But I use C4S on the driver tube, so there are SS devices in the circuit.
I would not mind trying to build a hybrid amp with tube driver and some sort of SE output stage in the future.
Me too. I thought about trying to devise a tube input stage to drive one of Nelson Pass' First Watt output stages. Might do it if Nelson would help.
I also don't mind sand in my amps, but am curious about your comments. Why did you (and dt667 too) suggest a tube input and solid state output? What about solid state driver and tube output stage? Speaker damping?
Speaking for myself only, I have to admit that my preference for a tube input is only based on my preference for tubes vs solid state, in general, and my bias that voltage gain stages are therefore best implemented with tubes. I don't much care about "damping factor" per se, because I use full-range ESL speakers, and ESL speakers do not generate significant back EMF that needs to be countered by amplifier damping. However, a transistor output stage might be advantageous in relation to size, heat generated, and, yes, low output impedance without the need for output coupling transformers. (I have always used OTL tube amps, where output Z is always sort of an issue and where there is no substitute for lots of output tubes to generate sufficient power and reasonably acceptable output Z.) Since the output stage, as I understand it, adds little in the way of gain, solid state devices would be acceptable as a substitute for an OTL tube output stage. Plus, I have always liked Moscode amps and those hybrid Counterpoint amps can sound good as well, athough I have not heard one in 20 years, probably. I know there have been products that do it the other way around: ss input with tube output, but that seems back asswards to me, given my biases and intended use.
I can enjoy great SS amps. I posted before the better SS amps outperform vintage unmodified middle of road tube type amps per my ears for detail and clairity plus are not edgy sounding either.
My best ampifier is a DIY all triode single ended design that were expensive to build. Just the audio transformers cost would buy a fine SS amp. So far this amp does have a performance edge, yet limited to only 3 watts.
Never tire of DIY pix. Nice work.
Hi Henry that is a nice project thanks for posting.It is nice to see new work in here. I am also very weary of the shmeal as well.
Personally, I would gladly trade most of the quasi-religious yammering on this forum for a lot more photo examples of successful DIY audio projects, regardless of the technology.
Notice I'm not passing judgment on anyone else's work.
I'm listening to this amplifier now and it is INSANELY good. Honestly, it might be that swapping in a particular tube amplifier might make it even "better" (or just different?), but, cripes! Who cares?
I suggest you try building one of these for yourself. It'll only set you back about $300 in parts if you don't get ambitious with the casework. Apex Jr. has a nice 600VA power transformer for $50, shipped, and HeatSinkUSA will sell you aluminum extrusions, cut to size, for surprisingly cheap.
"I'm listening to this amplifier now and it is INSANELY good."
Screw the technology used! A good amp is a good amp. All that matters is the music in the listening space. It's not exactly secret that I favor hybrids of "sand" and "glass", in carefully chosen situations.
That's 1st class workmanship. I wish I were that neat.
Thanks for sharing Henry! I'm actually collecting parts for Gary Pimm's Solid State Tabor amp. It's a ways off, but I hope to share it here when I'm done.
Love the metalwork! I see the same nickel plate screws from McMaster-Carr that my friend used.
You could always do another iteration of the front panel using FrontPanelExpress. You'd be amazed at the the capabilities of that CAD
too - for one, it will do both ANSI and DIN countersunk screws. I think
what would be most exciting to use would be the capability to cut inlays
and depths into the front panel. For instance, recessing the power switch
like is done on Audio Research or Threshhold gear of yore. Also, you can
do radius-rounded corners - eliminating those sharp edges!
You could also do wild projects using Front Panel Express - like cutting
out a rounded internal aperture that you could put some cut glass sheet
behind.. Then, you could like the glass - this is an visual idea I'm ripping off from the Moscode amp!
I got the screws from Harvey's Hardware in Needham. No doubt the same parts as from McMaster. Actually, I need to put in an order with McMaster because I've depleted my stock of black flat-head machine screws.
I got the heatsinks anodized at River Street Metal Finishing in Braintree. Really nice guys, and they have no problem with doing cash jobs for hobbyists. The only issue is they use this nasty claw-like thing to suspend the pieces in the anodizing tank and I can't see how you could do front panels that way without marks on the edges.
There's a place in NH called Cam Expert that offers a service like FPE, and I suspect for lower prices, too. Their claim to fame is their CNC router doesn't leave rough edges. They also offer anodizing after milling and other custom services. I haven't done business with them yet, but I'm giving serious consideration to having a nice front panel made for this amp. Also, I need a top cover made -- the one that's on there is just temporary.
He writes a great book on SS amp design. Some really deep material. I think you would like it.
Very cool Henry! Thanks for posting.
I've been dreaming of building a set of low power SS monoblocks...will give the link you posted some reading time later.
More interesing (and also more relevant) than a lot of the chatter here lately
Here's another picture of my audio rack. I'm listening to Vivaldi using my AMB Labs Gamma 2 USB DAC driven from the Mac laptop. Nice stuff.
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