well I believe it doesn't involve personal taste at all. I wasn't asking which is better.
maybe I should have been clearer.
feedback on the type of sound. like more bass, high are exagerated. things like these. And these description doesn't involve personal taste at all. these are facts that someone can hear.
maybe I should have been clearer.
feedback on the type of sound. like more bass, high are exagerated. things like these. And these description doesn't involve personal taste at all. these are facts that someone can hear.
Very strange question - a tube doesn't 'sound', an amplifier as a whole does. There are far too many variables, otherwise we'd be just changing the output tube and never mind all the other parts (like drivers, caps, transformers, not to mention the eternal musings over cables, 'magic' capacitors and resistors). Every tube has it's own peculiarities (at the very least regarding different major specs), that have to be taken into account when designing an amp as a whole, so it is impossible to compare on truly equal grounds. When you change a design from a popular DHT to a triode strapped pentode or BPT, you usually have to change the power supply, output transformer and driver circuit, all of which heavily influence the sound. Compared tot hat the fact that the output device is a DHT or a strapped pentode is actually of lesser signifficance, witness that all 300B amplifiers do not sound teh same even with the same actual 300B. Other than that, a pentode strapped as triode is a triode, as one member already wrote in this thread. After that you have to contend with it's triode parameters, just like you would with any other triode.
All tube types and their brand, vintage, have a characteristic tone. A well known trait. Quality and attention to cathode chemicals and metals, assembly precision and vacuum formation all count. A vintage 5 star Amperex is by no means an early 90's Shuguang.
Apart from that a design can incorporate, exemplify, offset, bypass some traits in an up to spec tube. But it can never add some missing intrinsic linearity. An excellent design manages better with an excellent tube element invariably. As for DHT vs Triode strapped beam tetrode or pentode, there are findings of an even more benign distortion amount and pattern in low gain DHT tubes. They certainly sound a bit more open and natural. The law of diminishing returns strikes heavilly, so choosing to depart from a triode mode KT88 to a 300B in SE or PP is rather a purist choice. DHTs require some care and cost for filament powering also, since hum appears easier in their case..
Apart from that a design can incorporate, exemplify, offset, bypass some traits in an up to spec tube. But it can never add some missing intrinsic linearity. An excellent design manages better with an excellent tube element invariably. As for DHT vs Triode strapped beam tetrode or pentode, there are findings of an even more benign distortion amount and pattern in low gain DHT tubes. They certainly sound a bit more open and natural. The law of diminishing returns strikes heavilly, so choosing to depart from a triode mode KT88 to a 300B in SE or PP is rather a purist choice. DHTs require some care and cost for filament powering also, since hum appears easier in their case..
NOt really. Compare a default pseudo-triode with a pseude-triode with additional screen circuit to separate ac and dc paths -- not a subtle difference in sound; I'm too untechnical to give you an explanation but this could point the way: http://www.vaughnaudio.com/carina-FAQ.html#Q14
Simon
Hi Simon,
Sorry, that sounds just like some maketing mumbo jumbo buzzwords collection - no hard facts given.
By all means, a screen grid tied to the anode just gets part of the anode, and no, neither Langmuir/Child theorem nor the electrons in space charge cloud do object to this.
Regards,
Tom
Sorry, that sounds just like some maketing mumbo jumbo buzzwords collection - no hard facts given.
By all means, a screen grid tied to the anode just gets part of the anode, and no, neither Langmuir/Child theorem nor the electrons in space charge cloud do object to this.
Regards,
Tom
I already tried to answer this in another forum, but I'll throw it in here too for people to argue about:
The reason, possibly the ONLY reason, why those antiquated DHTs from eighty + years ago are still popular and still produced, is because they are amazingly linear. Just have a look at the plate curves for a 300B or 2A3 and compare them with those of a triode-strapped pentode or beam tetrode, and you'll see what I mean - the difference is quite dramatic.
The consequence of this is that a triode-strapped pentode/tetrode produces more odd-order harmonic distortion. A DHT has plenty of second-order and a much lower amount of third-order, and that's about it. A triode-strapped pentode/tetrode produces also 5th and 7th order distortion, which can make it sound harsher. I don't believe the bass sound is any better or worse, but at the middle and treble frequencies the difference would be audible with a decent speaker and SET fans tend to be particular about this sort of thing!
The reason, possibly the ONLY reason, why those antiquated DHTs from eighty + years ago are still popular and still produced, is because they are amazingly linear. Just have a look at the plate curves for a 300B or 2A3 and compare them with those of a triode-strapped pentode or beam tetrode, and you'll see what I mean - the difference is quite dramatic.
The consequence of this is that a triode-strapped pentode/tetrode produces more odd-order harmonic distortion. A DHT has plenty of second-order and a much lower amount of third-order, and that's about it. A triode-strapped pentode/tetrode produces also 5th and 7th order distortion, which can make it sound harsher. I don't believe the bass sound is any better or worse, but at the middle and treble frequencies the difference would be audible with a decent speaker and SET fans tend to be particular about this sort of thing!
Hi ray_moth,
Just have a look at the plate curves for trioded EL83, 6V6, even 6L6 instead, I could name more. Too small? Just have a look at trioded 813.
For small signal tubes, f.e trioded EF86 and EF184 even rival, if not beat hands down, 6SN7 for linearity.
Compare them with some real triodes like, say, ECC81/12AU7 or 6AS7, I could name more, and you'll see what I mean - the difference is quite dramatic.
What was your point again?
Regards,
Tom
P.S.: Interestingly enough, when I held my "lecture" on triode-strapping pentodes in front of some real experts at the European Triode Festival ETF06 meeting, nobody stood up and said: "But real triodes inherently are more linear!". Instead, they had a good laugh when I (wink, wink) mentioned that I intentionally had worsened an example loadline plot of trioded EF184 so it wouldn´t upset the "real triode guys"
Just have a look at the plate curves for trioded EL83, 6V6, even 6L6 instead, I could name more. Too small? Just have a look at trioded 813.
For small signal tubes, f.e trioded EF86 and EF184 even rival, if not beat hands down, 6SN7 for linearity.
Compare them with some real triodes like, say, ECC81/12AU7 or 6AS7, I could name more, and you'll see what I mean - the difference is quite dramatic.
What was your point again?
Regards,
Tom
P.S.: Interestingly enough, when I held my "lecture" on triode-strapping pentodes in front of some real experts at the European Triode Festival ETF06 meeting, nobody stood up and said: "But real triodes inherently are more linear!". Instead, they had a good laugh when I (wink, wink) mentioned that I intentionally had worsened an example loadline plot of trioded EF184 so it wouldn´t upset the "real triode guys"
Those are not particularly linear triodes but they're also not DHTs either, so that's beside the point. I would agree that a triode-strapped EF86 or 6AU6, for instance, would probably be more linear than any of those IDH triodes and probably better than 12AX7 too. However, these are small signal pentodes, not power tubes, so that is also beside the point.
I still maintain that 300B and 2A3 are more linear than triode-strapped power pentodes/tetrodes - that was my point.
Hi dsavitsk,
6V6 ist not DH, so I don´t understand your point. I thought the point was more like "triode strapped" vs. "real triode"?
Anyway, have a look at triode strapped direct heated 813 pentode and then in turn show me a comparable real triode (DHT or not) of that class that does better regarding linearity.
Sadly, there are only very few direct heated pentodes of smaller power classes, which is natural when considering the time line of developments, and also when considering why direct heated emitter technology was superseeded at that time by indirect heater technology - what DH emitter afficionados like to ignore because it doesn´t fit in their argumentation. Instead, they just claim that DH is "the real thing" w/o giving hard facts, like for exampley how electrons are able to remember from what type of emitter they emanated, making them so proud that they sing the song with more musicality.
Please note that my point is not to claim that trioded pentodes are better than real triodes in general, but to show, that just repeating/exclaiming over and over "DHTs are superior in linearity to triode strapped pentodes" or just "real triodes are superior in linearity to triode strapped pentodes" doesn´t make a wrong statement true.
Regards,
Tom
dsavitsk said:
6V6 ist not DH, so I don´t understand your point. I thought the point was more like "triode strapped" vs. "real triode"?
Anyway, have a look at triode strapped direct heated 813 pentode and then in turn show me a comparable real triode (DHT or not) of that class that does better regarding linearity.
Sadly, there are only very few direct heated pentodes of smaller power classes, which is natural when considering the time line of developments, and also when considering why direct heated emitter technology was superseeded at that time by indirect heater technology - what DH emitter afficionados like to ignore because it doesn´t fit in their argumentation. Instead, they just claim that DH is "the real thing" w/o giving hard facts, like for exampley how electrons are able to remember from what type of emitter they emanated, making them so proud that they sing the song with more musicality.
Please note that my point is not to claim that trioded pentodes are better than real triodes in general, but to show, that just repeating/exclaiming over and over "DHTs are superior in linearity to triode strapped pentodes" or just "real triodes are superior in linearity to triode strapped pentodes" doesn´t make a wrong statement true.
Regards,
Tom
If you're comparing like with like, then look at directly heated tubes - something like the 2E22 and 1624 in triode. Then there's the 49 and the "almost triodes" like the 46. I personally haven't tried these - can anyone report? The 46 has a high reputation already, the others are less used.
And heres my 2 cents:
Hmm surely its just a DIFFERENT triode? Fact is, a triode strapped pentode or tetrode, is responding like a triode - it has triode like curves. Whether or not it is a GOOD triode is debatable. Like the 6AS7 is a triode but, not a linear one.
I've been looking at this as you probably guessed, and I'll say right now that I am definately NOT a fan of DHT's, but they are maddeningly linear on paper. Closest "pentode as a triode" that I could find is the trusty EL34. Which is what my SE amp is using. KT88 was OK but goes to pot at high signal swings
evidence for this claim is buried in a spreadsheet but here's the conclusions. I used a "typical" transformer impedance, measured the distance between the grid bias curves and took the standard deviation over a "typical" range of input swings. "Scores" were:
300B = 3
6v6 = 3.8
el34 = 4.4 (but 3.3 if you stay well away from clipping)
KT88 = 6.8
6AS7 = between 22 & 33 varies with transformer impedance
Ok I had to make some assumptions and therefore these are not definitive but it demonstrated to me that a correctly biased 300B is hard to beat.
Andy
phn said:
Klimon said:
Hmm surely its just a DIFFERENT triode? Fact is, a triode strapped pentode or tetrode, is responding like a triode - it has triode like curves. Whether or not it is a GOOD triode is debatable. Like the 6AS7 is a triode but, not a linear one.
I've been looking at this as you probably guessed, and I'll say right now that I am definately NOT a fan of DHT's, but they are maddeningly linear on paper. Closest "pentode as a triode" that I could find is the trusty EL34. Which is what my SE amp is using. KT88 was OK but goes to pot at high signal swings
evidence for this claim is buried in a spreadsheet but here's the conclusions. I used a "typical" transformer impedance, measured the distance between the grid bias curves and took the standard deviation over a "typical" range of input swings. "Scores" were:
300B = 3
6v6 = 3.8
el34 = 4.4 (but 3.3 if you stay well away from clipping)
KT88 = 6.8
6AS7 = between 22 & 33 varies with transformer impedance
Ok I had to make some assumptions and therefore these are not definitive but it demonstrated to me that a correctly biased 300B is hard to beat.
Andy
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