I'm interested in building some sort of single-ended triode tube amplifier, probably in a mono power amplifier format. I know enough to know that 15W is a lot to ask of a SET amp, but not enough to know how feasible or infeasible it is. If my expectations need readjusting, then please, adjust away.
A 300B, no, 10 watts is pretty much the max unless you run it into A2, or up the max limits, but I don't think most of the current production ones will take that kind of punishment. A 211, 845, GM70 or triode-wired 813, no problem. You just have to be prepared to deal with 1000+ volt power supply. If you're not an experienced DIYer that's a risky proposition. Also, SE amps with big transmitting tubes get complicated, expensive and heavy. You need a hefty DC supply for the filaments, and ALL your power components, including wire, caps and resistors, power tranny, chokes and output transformer have to be rated for transmitter level voltages.
That said, it can be done and a lot of people have, but it isn't cheap or easy. I have built SE 845 monoblocks, twice, for friends. By the time I was done I had no desire to do it anymore. ;-) I'm now a PP guy pretty much for that reason.
If this doesn't seem doable for you, consider a PP 300B. You get a good dose of the 300B sound with the advantage of more power, better bandwidth, better speaker control, quieter operation and cheaper components. It's a very good sound. I'm working on a PP 300B Williamson amp right now and pretty much have it nailed down, just waiting for some more components. The only downside is the price of 300Bs, but some of the Chinese ones go for $60 and aren't half bad at all. That's about the same as a KT66 these days.
That said, it can be done and a lot of people have, but it isn't cheap or easy. I have built SE 845 monoblocks, twice, for friends. By the time I was done I had no desire to do it anymore. ;-) I'm now a PP guy pretty much for that reason.
If this doesn't seem doable for you, consider a PP 300B. You get a good dose of the 300B sound with the advantage of more power, better bandwidth, better speaker control, quieter operation and cheaper components. It's a very good sound. I'm working on a PP 300B Williamson amp right now and pretty much have it nailed down, just waiting for some more components. The only downside is the price of 300Bs, but some of the Chinese ones go for $60 and aren't half bad at all. That's about the same as a KT66 these days.
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10 watts from a 300B isn't a big deal. You just have to pick from the myriad of SE 300B designs out there. ;-) And fixed bias will probably get you closer than cathode bias. The output transformer is the critical component here. The more you spend the better it will sound, but a Hammond or Edcor will yield decent results. You can always upgrade later.
What speakers do you have?
Personally I like a power tube driving the 300B, it makes for a more robust sound and has no trouble swinging the necessary volts to the 300B.
This is an old design that I'd probably go with if I were to go back to a 300B amp. It looks complicated but it really isn't, the odd drawing just makes it seem that way. It's a triode-wired EF86 driving a triode-wired 6V6 driving the 300B. The triode-wired 6V6 has a beautiful sound and imparts that to the 300B.
https://www.bonavolta.ch/hobby/en/audio/300b_7.htm
Personally I like a power tube driving the 300B, it makes for a more robust sound and has no trouble swinging the necessary volts to the 300B.
This is an old design that I'd probably go with if I were to go back to a 300B amp. It looks complicated but it really isn't, the odd drawing just makes it seem that way. It's a triode-wired EF86 driving a triode-wired 6V6 driving the 300B. The triode-wired 6V6 has a beautiful sound and imparts that to the 300B.
https://www.bonavolta.ch/hobby/en/audio/300b_7.htm
What's an example of a more spendy transformer?
@kmtang That wouldn't convert the amp to a push-pull?
For the most part it was a positive note saying it isnt that hard to do.
1627SEA is a healthy chunk of iron for up to 30 watts.
I dont know if Edcor even has a big enough core that will touch it.
They were limited years ago with core size and couldnt build what I wanted at the time.
Hammond engineers were pretty keen on their interleaving. Being few more steps ahead
of many, when speaking to the engineers.
Depending on how far your romance goes with triodes, as beautiful as they are.
pretty standard 6550 beam tetrode should reach as much as 20 watts depending
on your distortion goals. Likely higher distortion from the tube than the iron at that point.
Kmtang has the right idea: 2 X 300B in parallel http://4tubes.com/2-SCHEMATICS/BY-BRAND/Audio-Note/Conquest/conquest.gif
AudioNote did this 19 years ago
AudioNote did this 19 years ago
A more spendy transformer would be Monolith Magnetics, or Tamura, or Hashimoto and Finemet or another of the high-end transformers. Think anywhere from $600 to $1200 or more a pair.
A parallel SET amp with two 300Bs in parallel would not be push-pull, just two tubes in SE mode thereby doubling the power. It's a possibility.
I agree. I've never tried an indirectly-heated SE amp. I have a friend who bought an early version of Dennis Had's Inspire stereo SEUL amp and he thinks it's lovely, and I believe him. My argument would be, at that point, why not go push-pull? Yes, you lose a tiny bit of the directness but you gain so much more.
Some don't like paralleled triodes due to the interactions between the tubes. An alternative which I advocate is to use a stereo amp, but wire the output transformer secondaries in series. A pair of 8 watt per channel stereo 300B amps then becomes a pair of 16-watt monoblocs.
In addition to having much less interaction between the tubes, there are a few other advantages:
* You can start with one stereo amp, and determine whether you really need the added 3dB before spending the money for a second.
* You can bi-amp easily if you change your mind
* Your choice of circuits is wider
In addition to having much less interaction between the tubes, there are a few other advantages:
* You can start with one stereo amp, and determine whether you really need the added 3dB before spending the money for a second.
* You can bi-amp easily if you change your mind
* Your choice of circuits is wider
Might want to checkout Skunkie Designs KT 120se monoblock build and video series.
https://www.skunkiedesigns.com/kt120-monoblock
https://m.youtube.com/playlist?list=PLtEhh3UpOsiDh6orcLPoJjPWSy--6g675
Not pure triode and UL strapped, but will give you the power single ended in a simple amplifier.
Dan
https://www.skunkiedesigns.com/kt120-monoblock
https://m.youtube.com/playlist?list=PLtEhh3UpOsiDh6orcLPoJjPWSy--6g675
Not pure triode and UL strapped, but will give you the power single ended in a simple amplifier.
Dan
