With an unbypassed cathode bias resistor, the 300B will be fine. IMO, without NFB of some kind, too much 2nd order HD is produced. Out of the box, 2A3s are excellent.
It should be obvious that I'm not a fan of beau coup euphony. 😉
Those sweep tubes are rock solid but I think a 2A3 will sound more interesting.... at a price.
The OP is in Belgium. I'm not sure if he shares the American "let's do it for two dollars" DIY ethic, even though I appreciate it myself, as a local folk art.
Wanna hear a benchmark low powered SE triode amp?...use a real DHT. I think the additional cost and hassle is worth it. 2A3.
The OP is in Belgium. I'm not sure if he shares the American "let's do it for two dollars" DIY ethic, even though I appreciate it myself, as a local folk art.
Wanna hear a benchmark low powered SE triode amp?...use a real DHT. I think the additional cost and hassle is worth it. 2A3.
I agree with Joe Roberts' 2A3 suggestion. Class "A1" operation will yield 3.5 WPC. If the OP is pleased, he can add Tubelab's PowerDrive, to squeeze a bit more power out in "A2".
The "water" can be tested in stages. Triode wired 6AV5s work with 2A3 designs. The next step would be Chinese bi-plate 2A3s, which are not especially costly. Finally, fancy (expensive) NOS mono-plate 2A3s would be installed.
Undoubtedly, the O/P is used to good bass. Therefore, I suggest the B+ be rectified with high PIV Schottky diodes.
The "water" can be tested in stages. Triode wired 6AV5s work with 2A3 designs. The next step would be Chinese bi-plate 2A3s, which are not especially costly. Finally, fancy (expensive) NOS mono-plate 2A3s would be installed.
Undoubtedly, the O/P is used to good bass. Therefore, I suggest the B+ be rectified with high PIV Schottky diodes.
Well, the OP has been curiously absent in this discussion, so who knows what he is looking for?
I'm using my bud jc morrison's commercial designs as my benchmark for "linear sounding" 300B amps. These use a regulated supply, super low distortion DC feedback circuit, open loop real WE 300B, and a foil secondary output transformer flat from 10hz-75k with no resonances which was recently tested in Japan by Atarashi as having o.045% distortion at 3W.
jc has the Audio Precision 2..I don't know the exact H2 spec, but it is the tube itself generating whatever distortion prevails. These silbatone amps do not sound euphonic, or tubey, or solid state. They are clean and colorful. Might not be quite what they are if 300B did not add a little touch of flavoring.
Hey I like the old pentode drive 91 circuit 300B...sure it has a lot of "character" but many perceive that as a plus. I like all sorts of amps, not too dogmatic on a priori principles but looking for beauty where I can find it.
I'd agree though that a good old 2A3 tends to have a more clean and clear presentation in the simple DIY circuits under discussion. Overall, a tried and true great tube.
I'm using my bud jc morrison's commercial designs as my benchmark for "linear sounding" 300B amps. These use a regulated supply, super low distortion DC feedback circuit, open loop real WE 300B, and a foil secondary output transformer flat from 10hz-75k with no resonances which was recently tested in Japan by Atarashi as having o.045% distortion at 3W.
jc has the Audio Precision 2..I don't know the exact H2 spec, but it is the tube itself generating whatever distortion prevails. These silbatone amps do not sound euphonic, or tubey, or solid state. They are clean and colorful. Might not be quite what they are if 300B did not add a little touch of flavoring.
Hey I like the old pentode drive 91 circuit 300B...sure it has a lot of "character" but many perceive that as a plus. I like all sorts of amps, not too dogmatic on a priori principles but looking for beauty where I can find it.
I'd agree though that a good old 2A3 tends to have a more clean and clear presentation in the simple DIY circuits under discussion. Overall, a tried and true great tube.
Sorry to say but that is also meaningless because it's subjective to individual. What these sound reproducing devices are grated is based on the level of audible fidelity, higher the better, also known as Hi-Fi. For that, it would be something that's low distortion and linear enough to give audible transparency.
What is "low distortion and linear enough to give audible transparency?"
.05%, 1%, 9%?
Is this written down somewhere in numbers or is it the kind of thing you just wake up in the morning and KNOW?
I always thought that listeners can make up their own minds on grading audio gear, but I guess I didn't get the magazine issue you got.
I will say that if super low distortion is your goal, don't build NFB SE amps.
.05%, 1%, 9%?
Is this written down somewhere in numbers or is it the kind of thing you just wake up in the morning and KNOW?
I always thought that listeners can make up their own minds on grading audio gear, but I guess I didn't get the magazine issue you got.
I will say that if super low distortion is your goal, don't build NFB SE amps.
Wow, looks like someone woke up on the wrong side of the bed this morning...
Perhaps Google search will help to lighten your mood if you aren't familiar with audible distortions of amp.
Listeners certainly can make up their own minds. I didn't oppose that, did I?
The title of this thread is "Best SET amp design (>4 Watts)?". Lets stick to SET amp, shall we? So, what is your criteria for judging the quality of sound replying devices such as SET amp?
Not really, I'm happy as a clam this fine day. Drinking some good coffee and listening to a R&B show on local FM. Chillin'.
Just don't see how your definition escapes subjective criteria.
Even if you choose to use objective criteria, the decision to do so is a subjective one.
My criteria for judging amps is based on enhanced communication with the soul of music.
Yes, it is an individual subjective criterion. I really don't care what other people think about my amps and no skin off my nose if somebody likes something I don't care for.
And your definition did imply that one is wrong if they like an amp that doesn't fit the criteria you espouse, which is why I asked what exactly you mean by your statement. You seem to be pointing to an empirical definition, which I think is impossible to pin down and leaves one mired in the swamp of individual subjectivity in the end.
I don't have a problem with this. I think individual subjective criteria are the proper measure. Do you?
I know about distortion but I don't know where to draw the line.
I am not sure there is a knowable predefined line, especially with SE triode amps.
Just don't see how your definition escapes subjective criteria.
Even if you choose to use objective criteria, the decision to do so is a subjective one.
My criteria for judging amps is based on enhanced communication with the soul of music.
Yes, it is an individual subjective criterion. I really don't care what other people think about my amps and no skin off my nose if somebody likes something I don't care for.
And your definition did imply that one is wrong if they like an amp that doesn't fit the criteria you espouse, which is why I asked what exactly you mean by your statement. You seem to be pointing to an empirical definition, which I think is impossible to pin down and leaves one mired in the swamp of individual subjectivity in the end.
I don't have a problem with this. I think individual subjective criteria are the proper measure. Do you?
I know about distortion but I don't know where to draw the line.
I am not sure there is a knowable predefined line, especially with SE triode amps.
This is an issue I have wrestling with for about 20yrs since I accepted that there was something I really liked about SE amp immediacy despite the prevailing thoughts of the day about acceptable distortion levels.. Sadly this kept me away for quite a while despite my familiarity with the writings in Sound Practices on the subject.
Strangely enough given the monotonic nature of distortion in most SE amps, and given how conservatively I run mine I've found that the Western Electric references to 5% thd at full power to be not too far off the mark as a starting place. 10dB below maximum power I generally find the distortion to be under 0.5% or so which given speaker distortions is acceptable to me. I now build fairly big, high voltage, GM70 transformer coupled SE amps for my own use - these do about 6dB better distortion wise at a given power level than my old 300B amps.
I'm not a fan of cathode bias in SE amp output stages which with transformer drive leads to complications. Waiting for a set of custom ITs from Monolith in Belgium.
Arthur L and I used to discuss this issue pretty regularly - we were never really able to get to the bottom of it. Much good wine was shared however.
To the OP you can't really go wrong sourcing transformers from your Belgian compatriots at Monolith Magnetics. (No affiliation other than happy customer, and yes it's a shameless plug) How about some Philips or Adzam dhts which should be available there? Assuming you speak dutch here is a page you might want to look at: http://www.triodedick.com/
To keep this thread random I'll throw in my own ramblings: get the best output transformer you can get or afford rated for the needed power. Pick a tube that works with that transformer. Pick a driver tube that is actually able to drive the output stage. Put a CCS load on that driver, dc couple with stacked supplies, listen to music.
Who's next?
Who's next?
Eli...checked with jc on 300B distortion. Here's the reply
There ya have it. The amps in question sound very clean and not exactly euphonic but not mechanical or washed out sounding either.
In the context of this discussion, I don't think talking about distortion adds much. Pretty sure the Radiotron 2A3 can hit 5% cranked to max but it sounds great.
I'm with kaputt, whether he is serious or not!😀
In some sense it is a bit random, at least in the technical evaluative frameworks many have come to rely on. Live dangerously.
There ya have it. The amps in question sound very clean and not exactly euphonic but not mechanical or washed out sounding either.
In the context of this discussion, I don't think talking about distortion adds much. Pretty sure the Radiotron 2A3 can hit 5% cranked to max but it sounds great.
I'm with kaputt, whether he is serious or not!😀
In some sense it is a bit random, at least in the technical evaluative frameworks many have come to rely on. Live dangerously.
Actually I was both. And I would approach a build as I have stated above. Maybe with a specific change towards a driver with a low enough Rp to use a nickel plate choke but these are details.
The distortion topic you guys opened is interesting. The last power amp I built was quite a challenge to get playing. In an intermediate stage that allowed listening to records it had that spooky quality were the music gave me actual goosebumps (in a nice way). Now that all (most) problems are fixed and the fear of the thing blowing up and taking the walls out is gone that special quality is gone as well. I don't have an idea what to look for to get that back. Distortion? Fear of death? The great unknown?
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Measurement is objective. Once the audible characteristics of amp's distortions are revealed via listening tests, the measurements can correlate to other amps.
Looks to me, you are mixing up the source of sound to judge. What you described is for judging the musical performance as in musicians playing instruments or vocalist singing. This thread is about the device that recreates those performances. The judging of latter is based on its level of fidelity to the original source (musical performance).
See above.
See my first sentence above.
Fact: 0.3% THD is inaudible, with a pure sine wave source. With a complex musical waveform as the source, the point of detectability rises.
From an annoyance/detectability perspective, IM distortion is more noteworthy than HD.
Considerable 2nd order HD is not HIFI. However, some listeners find it highly pleasing. Apples and oranges.
Proper mating of amps and speakers is essential, if a superior result is to be realized. The sort of modest power O/P and damping factors of the stuff being discussed will not do, if speakers such as the AR3 or AR9 are to be used. For that kind of speaker, get a H/K Cit. 2 or McIntosh MC275. By the same token, those amps are poor candidates for connection to high efficiency horn speakers. Can you say over damped?
From an annoyance/detectability perspective, IM distortion is more noteworthy than HD.
Considerable 2nd order HD is not HIFI. However, some listeners find it highly pleasing. Apples and oranges.
Proper mating of amps and speakers is essential, if a superior result is to be realized. The sort of modest power O/P and damping factors of the stuff being discussed will not do, if speakers such as the AR3 or AR9 are to be used. For that kind of speaker, get a H/K Cit. 2 or McIntosh MC275. By the same token, those amps are poor candidates for connection to high efficiency horn speakers. Can you say over damped?
So you are saying that amps that measure the same sound the same. With typical steady state measurements yet?
I do not think experience bears this one out.
I submit that a strict ranking of amps by measured criteria will not map the subjective ranking of those amps. And, if not, what good are the measurements for pre-judging listening quality?
There is too much going on and measurements are just too crude to capture the complexity of the interactions. And that is just on the bench. Add humans listening to music and there is not much science in it.
The fact is that although measurements are empirical (not objective), they are largely based on what and how we can measure. The test signals are not music and the setups do not track transient interactions with a time dimension. But the biggest problem is that there is no "listening brain" plug-in for the meters.
I say that they are not objective because the measurement systems and electronic evaluation criteria are cultural creations. They are not written on tablets handed down from the heavens. We made this stuff up and we agree, more or less, that it is good. But they are "empirical" data, which is what I think you are really meaning to indicate. Solid hard data, right?
Well, I haven't met anybody smart enough to conclusively link those digits to subjective listening impressions beyond general vague statements that have the ring of truthiness and sound eminently sensible in audio forum threads.
And if you believe in strict correlations between distortion and listening satisfaction, I suggest you don't participate in SE amp threads because there is a hella lot of distortion around here!😀
Precisely. I am counting emotional recreation in my evaluation, since that is why I listen to music. Otherwise, I'd just hook my amp up to a scope and watch the traces. Wouldn't even have to waste money on speakers.
Aren't you looking for musical enjoyment above all?
I know what you are getting at, Evenharmonics, but the topic is too deep and critical to be left to generic forumspeak answers. And also too complex, interactive, and granular to be summed up by a few convenient sound card measurements.
Let me ask, which SE amps are you listening to and what is their measured distortion? And do your subjective impressions track the distortion ratings exactly for all of the SE and other amps you've heard and measured?
If not, why not?
Re-reading the OP, it seems that an ideal is what's being requested. Would everybody agree that an ideal, spare-no-expense, SET include a regulated power supply about as good as the nominal signal pass stages themselves? As good a bandwidth, especially.
Thanks for any inputs,
Chris
Thanks for any inputs,
Chris
Chris,
I'll stick with Schottky diode rectified B+, for the previously stated reasons. For regulation, a critical current, choke I/P filter should be quite adequate and there will be no concerns about voltage reference noise or active regulator bandwidth. 🙂
The OP is in the EU. For 2A3 "finals", Sowter's SE05 appears to be a prime candidate for the O/P transformer, but it stands to reason that Lundahl (Sweden) will offer some good competition.
Let Joe Roberts provide a nice pentode voltage amplifier. Tubelab's PowerDrive takes care of the Class "A2" operation needed to realize 4+ WPC.
2A3s are known to be fine with AC filaments, but Rod Coleman's filament regulator would not hurt. 😉
I'll stick with Schottky diode rectified B+, for the previously stated reasons. For regulation, a critical current, choke I/P filter should be quite adequate and there will be no concerns about voltage reference noise or active regulator bandwidth. 🙂
The OP is in the EU. For 2A3 "finals", Sowter's SE05 appears to be a prime candidate for the O/P transformer, but it stands to reason that Lundahl (Sweden) will offer some good competition.
Let Joe Roberts provide a nice pentode voltage amplifier. Tubelab's PowerDrive takes care of the Class "A2" operation needed to realize 4+ WPC.
2A3s are known to be fine with AC filaments, but Rod Coleman's filament regulator would not hurt. 😉
This is a case of glass half full vs. half empty. Lack of high order harmonics of SET amp is what attributes to listeners interpreting as more natural sound compared to P-P amp's high order harmonics from crossover distortion attributing to more "sterile" sounding to the listeners despite its lower distortion. Per Hi-Fi definition, more natural sounding device wins.
Indeed. Due to the inherent low efficiency of SET amp, it should be mated with high efficiency speaker for mid and high frequencies and let P-P amp power the bass region.
In fairness, we should remember that this is a supposition.
Thanks, as always,
Chris
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