Johan Potgieter said:
Johan;
my fault: living in Randburg and working in Sandton I did not bother to learn Africaans so I can't explain you better that I meant exactly the same you write, i.e. if to speak of optimum we have to speak of criteria of optimization before.
30 years ago I was young and stupid and invented Watt*Procent, i.e. power multiplied by THD to compare apples and oranges, now I don't think this measure is valid because harmonics need to be weighted, i.e. they need to have own coefficients of nastiness, and the higher is power the more excusable are distortions.
So, this will be better: WD = (L2*k2+L3*k3 + ...)/P
where L is power of the harmonic, k is coefficient of nastiness, WD is coefficient of Weighted Distortions. For the beginning, k may be equal to the number of the harmonic.
So, if to simplify, WD = ( L2*2 + L3*3 + L4*4...)/P
Curves for different amps would be interesting to see (power horizontally, WD vertically). The ideal amplifier should have always WD as close to 0 as possible.
Edit: typos corrected
Contentious stuff indeed!
I'm trying to remember what the connection was on the PP EL34 BBC amplifier. I'm sure I have a diagram somewhere, but laying hands on it might be difficult.
In a slightly different application, I remember seeing an amazing (well, I was amazed by it in 1983) audio amplifier at an HF transmitter site. The transmitter used anode modulation, so there was an output transformer the size of a small wardrobe coupled to a pair of output valves each the size of a large bucket. These were driven by rather smaller valves (perhaps only the size of a German beer mug), preceded by even smaller valves (212?). Finally, this lot was driven by a Leak T/L12+. Yup, ultra-linear. I don't know what that proves, but it certainly surprised me to see the dinky T/L12+ surrounded by the monsters in the transmitter hall.
phn said:
I'm trying to remember what the connection was on the PP EL34 BBC amplifier. I'm sure I have a diagram somewhere, but laying hands on it might be difficult.
In a slightly different application, I remember seeing an amazing (well, I was amazed by it in 1983) audio amplifier at an HF transmitter site. The transmitter used anode modulation, so there was an output transformer the size of a small wardrobe coupled to a pair of output valves each the size of a large bucket. These were driven by rather smaller valves (perhaps only the size of a German beer mug), preceded by even smaller valves (212?). Finally, this lot was driven by a Leak T/L12+. Yup, ultra-linear. I don't know what that proves, but it certainly surprised me to see the dinky T/L12+ surrounded by the monsters in the transmitter hall.
Re: Contentious stuff indeed!
Engineers have done some stupid things, indeed. The Church of Positivism, anyone? But we have to make some distinction or we end up in La-la-land of Stereophile, where everything is of equal/zero value. Eclectic, or junk, postmodernism, Jean-François Lyotard calls it.
UL or pentode connected is a step above debating the merits of cryogenics of OFC.
I'm not surprised. It seems UL caught on later on continental Europe. But by the 1960s it seems like everybody had gone UL. I googled UL not too long ago. And according to what I saw, the UL fans consider UL the one solution to all the ills of the world. So did the positivists and every other fanatic that has ever lived. That is, after all, pretty much the definition of fanaticism. Some even create religions.
Bandersnatch said:
Engineers have done some stupid things, indeed. The Church of Positivism, anyone? But we have to make some distinction or we end up in La-la-land of Stereophile, where everything is of equal/zero value. Eclectic, or junk, postmodernism, Jean-François Lyotard calls it.
UL or pentode connected is a step above debating the merits of cryogenics of OFC.
EC8010 said:
I'm not surprised. It seems UL caught on later on continental Europe. But by the 1960s it seems like everybody had gone UL. I googled UL not too long ago. And according to what I saw, the UL fans consider UL the one solution to all the ills of the world. So did the positivists and every other fanatic that has ever lived. That is, after all, pretty much the definition of fanaticism. Some even create religions.
Sorry Douglas, been too busy. I can't remember all the attempts or exact details but most either had a CCS on the driver plate or very high resistance (>500k) and current in the driver was adjusted to compensate for that in the e-linear resistor. A 9002 driver into 6BQ5 and 6CW5 were certainly tried. UL tap and output plate were tried. Always DC coupled e-linear, RC coupling between driver and output. In general any degeneration sufficient to make a significant difference in gain or low harmonic distortion components was accompanied by raised harmonics say ~ 5th and up. Far be it for me to botch implementation 🙄, any design guidelines appreciated.
A second apology! If you can recall some of the background regarding noise vs. gNFB it would be greatly appreciated. Sounds fascinating. Re: UL, I agree with you completely regarding its benefits, it's just I can accomplish my needs without and avoid (sorry) gNFB, which to my ear in my implementations always pulls phantom images towards the speakers. I can live with the mild deviations in frequency response caused by moderate Zout since the room is many times worse but once having heard it not without the huge sense of expansiveness from a no gNFB amp. Not saying it's a one-one relationship either, however I don't yet know how to get there any other way.
hey-Hey!!!,
I have only had good results from cascode diff amps in the E-Linear circuit. Pentodes work OK, but the g2 current counts in the cathode but doesn't contribute to the load/signal so I stick with cascode( and I don't do SE ). The upper grid( actually gate) node gets referenced to the cathodes. Voltage set with appropriate divider and cap bypassed on the lower one( between cathode and upper grid/gate ).
I never got results I liked the sound of with triode E-Linear, though I tried many, as it is a bit simpler. A friend measured some of the triode E-Linear driver amps and they dispalyed the same sort of distortion results you described.
My favourite is a triode/MOSFET cascode. Triode on the bottom, and MOSFET on the top. I get a spread of taps in for the output TX's. Currently the Peerless S265Q I get from Heyboer come with 20, 30 and 40%. In an 807 amp, we put 40% to the g2 and used the 20% for the E-Linear front end( 6H30 and FQP1N50 ). Very sweet!
cheers,
Douglas
I have only had good results from cascode diff amps in the E-Linear circuit. Pentodes work OK, but the g2 current counts in the cathode but doesn't contribute to the load/signal so I stick with cascode( and I don't do SE ). The upper grid( actually gate) node gets referenced to the cathodes. Voltage set with appropriate divider and cap bypassed on the lower one( between cathode and upper grid/gate ).
I never got results I liked the sound of with triode E-Linear, though I tried many, as it is a bit simpler. A friend measured some of the triode E-Linear driver amps and they dispalyed the same sort of distortion results you described.
My favourite is a triode/MOSFET cascode. Triode on the bottom, and MOSFET on the top. I get a spread of taps in for the output TX's. Currently the Peerless S265Q I get from Heyboer come with 20, 30 and 40%. In an 807 amp, we put 40% to the g2 and used the 20% for the E-Linear front end( 6H30 and FQP1N50 ). Very sweet!
cheers,
Douglas
Re: Re: Contentious stuff indeed!
The reason UL took off is simply engineers of that time understood what they were looking at and could see the advantages. To be fair too many of the negative and problem comments regarding UL topology is simply with today's culture there aren't engineers who really understand it and are prepared to work out the output stages and transformer problems, even though many of todays o/p tranny vendors make a better job than their ancestors did. We have to understand that a better product implies better bandwidth and so come other problems. To be fair, one of the critics of UL, is one really needs a scope and know what one is looking at in the amplifier. I rate UL 10/10.
richj
phn said:
The reason UL took off is simply engineers of that time understood what they were looking at and could see the advantages. To be fair too many of the negative and problem comments regarding UL topology is simply with today's culture there aren't engineers who really understand it and are prepared to work out the output stages and transformer problems, even though many of todays o/p tranny vendors make a better job than their ancestors did. We have to understand that a better product implies better bandwidth and so come other problems. To be fair, one of the critics of UL, is one really needs a scope and know what one is looking at in the amplifier. I rate UL 10/10.
richj
No doubt, Douglas!Bandersnatch said:
Loading a triode on very-very low dynamic resistance you got the 2'nd harmonic distortion of the highest possible level, that's why it sounds sweet! 😀
Also, it intermodulates well adding some richness to the sound it did not contain. 😎
Cascoded triodes were used in UHF frequency converters exactly because they minimized impact of Miller capacitances and maximized intermodulation of received and heterodyne signals. Multi-grid converters had better modulation with less intermodulation, but were too slow because of capacitances for such frequences, so cascodes were used instead.
ummmm, it is a PP amp, front end included, so there is not much 2HD. Also, the term 'sweet' is a general adjective for good. It isn't used to specifically describe any performance attributes.
cheers,
Douglas
cheers,
Douglas
Anatoliy,
Your post #161: No problem with your writing; I just did not get to what you meant immediately. You actually worked here?? When was that?
Regards.
Your post #161: No problem with your writing; I just did not get to what you meant immediately. You actually worked here?? When was that?
Regards.
rdf said:
Hi rdf,
In my data sheet the max. Ia for EL34 triode operation is 75 mA (you quoted quiesc. current). That gives one 33V bias, with the max. signal per tube 33.9V. OK, still seems to be positive, but I have RCA data giving the same specs, stating that max. G1 drive is taken "just before the onset of grid current." I find other small like discrepancies in other Mullard data sheets; perhaps someone just left off the decimal point, perhaps ..... I find it hard to believe that a tube manufacturer would purposely mislead; they sell tubes, after all, not circuits.
Regards
Edit: Sorry, you also made the remark "How else could UL, with less feedback around the output, have less distortion otherwise?" I fear I do not quite understand that. Less distortion than? .... and less feedback around the output, how?
More regards
Johan Potgieter said:
Feb 1999-Feb 2000, NetActive (Pty) Ltd. Still, what do you think of Weighted Distortions' curves?
Some further remarks (repetition?),
On rereading somewhat, I think the point must be made that nobody (at least not this body), is waving a flag for UL or organising a petition. Simply .....
The point hopefully has been made that for similar ra and distortion than triodes, about twice the output is available. The similar ra to triodes carries with it similar performance on the whole, specifically regarding loudspeaker loads. Relative load independance has been demonstrated by graphs. E.g. for a greater than 4:1 variation in load impedance, a typical measurement showed thd to be 2% at only 2.5k (p-p), 1.5% at 4K, 1% at 6K, 0.4% at 9K and 0,5% at 11K. Power output varied by only 13% over this range of Zload. Pentode behaviour varies by more than 10x (distortion) and 2x (output power) over such a span of Zload apart from other disadvantages; triodes behave not significantly better than UL. The output transformer should hardly be more expensive than for simple triodes (but I have not looked up).
So, yet again, I cannot understand why there should be resistance by some. One simply gets very similar performance to an equivalent triode circuit, but with a margin of watts to spare. So where is the problem?
Hearing experiences by some and the tendency regarding industrial amplifiers are valid arguments. But hearing is subjective (medically proven; it is not a shortcoming or a shame), while industrial amplifiers do not have high fidelity as their first priority. Still, if they don't use it, why not? ...go ask those designers!
The fact that "it is not fully understood" seems to convey some cloak and dagger fear with it, as if it might suddenly explode in one's face one dark and stormy night. (I like dark and stormy nights.) Fully understanding it is to me for physicists; I understand enough to enable me to use it to good and predictable effect. I still have to read any reason as to why not to use it. (I would be the first one to adopt a different topology as soon as that is motivated properly. Until then ....)
Regards.
On rereading somewhat, I think the point must be made that nobody (at least not this body), is waving a flag for UL or organising a petition. Simply .....
The point hopefully has been made that for similar ra and distortion than triodes, about twice the output is available. The similar ra to triodes carries with it similar performance on the whole, specifically regarding loudspeaker loads. Relative load independance has been demonstrated by graphs. E.g. for a greater than 4:1 variation in load impedance, a typical measurement showed thd to be 2% at only 2.5k (p-p), 1.5% at 4K, 1% at 6K, 0.4% at 9K and 0,5% at 11K. Power output varied by only 13% over this range of Zload. Pentode behaviour varies by more than 10x (distortion) and 2x (output power) over such a span of Zload apart from other disadvantages; triodes behave not significantly better than UL. The output transformer should hardly be more expensive than for simple triodes (but I have not looked up).
So, yet again, I cannot understand why there should be resistance by some. One simply gets very similar performance to an equivalent triode circuit, but with a margin of watts to spare. So where is the problem?
Hearing experiences by some and the tendency regarding industrial amplifiers are valid arguments. But hearing is subjective (medically proven; it is not a shortcoming or a shame), while industrial amplifiers do not have high fidelity as their first priority. Still, if they don't use it, why not? ...go ask those designers!
The fact that "it is not fully understood" seems to convey some cloak and dagger fear with it, as if it might suddenly explode in one's face one dark and stormy night. (I like dark and stormy nights.) Fully understanding it is to me for physicists; I understand enough to enable me to use it to good and predictable effect. I still have to read any reason as to why not to use it. (I would be the first one to adopt a different topology as soon as that is motivated properly. Until then ....)
Regards.
Wavebourn said:
Absolutely. I have not graphs in front of me; I remember that Crowhurst and another wrote about this all of >40 years ago? What I do know and appreciate (and am trying to keep out of my designs, especially SS), is the serious listener fatigue that can occur as a result of high order harmonic distortion (rather the same thing). If I recall correctly, it was about when (30 years ago?) Peter Walker realised that something was the matter with his early transistor amplifier, that this came to be established. Some researchers came up with the suspicion that some discordant combinations seem to affect the brain even when on or below the threshold of hearing. [This is not so fantastic, as it is known to medical science that the brain can detect undesirable sound "stimuli" below the hearing threshold. Such stimuli can cause discomfort (e.g. a headache) even when not consciously audible as a sound, e.g. a 30 Khz loud enough signal.]
I must not start, but I was briefly involved in research regarding nerve deafness and other associated auditory matters in the 70s, also visiting several medical centres in the USA. A most interesting field in which I would dearly have loved to continue - but my boss had other ideas .....
Regards.
Johan Potgieter said:
Sorry, I was in stupid mode. EL34 triode mode p-p outperformed UL, it was the EL84 which demonstrated superior UL performance according to Mullard. 8 and 3 can be confusing. 🙄 I do find the choice of operating conditions chosen for the EL84 triode example - 24ma standing current, less than 7 watts quiescent diss - curious. Some variance between manufacturers is expected but I've never seen an EL84 minimize the third harmonic at lower currents. Many samples of the EL86 on the other hand have a pronounced 3rd order minima near those figures.
By feedback I meant local, from plate to screen. Pentode mode has none, triode drives 100% of the plate voltage back into the screen, UL is in-between.
Hi RDF,
Did you mean many samples of EL34 on the other hand have a third order minima near those figures?
Did you mean many samples of EL34 on the other hand have a third order minima near those figures?
Re: Re: Re: Contentious stuff indeed!
Then I guess the engineers at Altec, Telefunken and Klangfilm never understood UL. (I'm pretty sure they had a scope.) And if they didn't, then I cannot see what there is to understand. Again, I value the opinions of the engineers at Altec, Telefunken and Klangfilm a lot higher than I do the opinions of the home audio manufacturers. Companies like Telefunken not only made amps, they designed and manufactured the tubes used in their amps! They supplied the transformers as well. Telefunken, at least Siemens, was the Intel or AMD of its time. I would think the engineers at Intel and AMD know microprocessors just as well as Telefunken knew tubes.
What exactly did madmen Saul Marantz and Frank McIntosh know that some of the finest engineers in the business didn't know and Ken Shindo still doesn't know?
richwalters said:
Then I guess the engineers at Altec, Telefunken and Klangfilm never understood UL. (I'm pretty sure they had a scope.) And if they didn't, then I cannot see what there is to understand. Again, I value the opinions of the engineers at Altec, Telefunken and Klangfilm a lot higher than I do the opinions of the home audio manufacturers. Companies like Telefunken not only made amps, they designed and manufactured the tubes used in their amps! They supplied the transformers as well. Telefunken, at least Siemens, was the Intel or AMD of its time. I would think the engineers at Intel and AMD know microprocessors just as well as Telefunken knew tubes.
What exactly did madmen Saul Marantz and Frank McIntosh know that some of the finest engineers in the business didn't know and Ken Shindo still doesn't know?
Re: Re: Re: Re: Contentious stuff indeed!
You forgot Philips 😀
But ... wasn't this UL topology patented ?
Perhaps didn't they just want to pay royalties 😎
Not being an engineer, I fell better with stable screen supply !
Yves.
phn said:
You forgot Philips 😀
But ... wasn't this UL topology patented ?
Perhaps didn't they just want to pay royalties 😎
Not being an engineer, I fell better with stable screen supply !
Yves.
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