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In article ,
(Andre Jute) wrote: Reply to message Yo, John The key thing you say in your post is 'local NFB similar to the 14 dB or so that is inherent in the 300B at one of the operating points you suggested'. How did you calculate this number or where did you come by it? Hi Andre, Because my 300B data sheet is buried somewhere out of reach, and because I wasn't able to find the necessary data quickly on the web, I just held my finger to the wind to get that number based on very rudimentary specifications for the 300B, and by guessing at the details of your operating point that you haven't yet posted. My method is to build two spice simulations of the amplifier in question, one with a normal model for the 300B, or other output triode, and a second one where the model for the 300B has the anode voltage used in the internal anode current equations replaced by the value of the DC plate voltage used, feed into the model on a fourth pin. The difference in the gains of these two models represents the amount of "NFB" internal to the triode. I have now found the data necessary to create a spice model of the 300B, so if I can find my spread sheet that builds the triode spice models from the tube data, I should be able to replace my finger to the wind estimate with a more precise number for the amount of "NFB". I think it would be a waste of time to wait for Pinkerman's so-called design. Well before his latest debacle in the NFB thread which dissipated (pun intended) your remaining faith in him, Patrick patiently demonstrated (at greater length than Hugh Hefner's 'philosophy', and in my threads -- don't do it again, Patrick; once is funny, twice calls for pistols at dawn) that Pinky doesn't really have much idea of Class A amps either. This poor gatecrasher's insistence on an emitter follower was just about the final straw for everyone, and he knew it for he took his foolish promise away for 'tests'. Therefore I suggest that if your interest has been piqued, you publish the design you found on your netsite and then those interested can discuss it without reference to Pinky's aborted efforts. I was one step ahead of you there, I had already placed the article on my web pages, and posted a notification to that effect under the subject "KISSASS 'The Transistor Amplifier'" Truth is, I think you're all on a hiding to nothing though, one never knows, you might find the journey entertaining. My own moment of revelation in Class A discrete transistor amps may amuse mildly. The zero-return point of marginality in transistors arrived when I realized that for the price of the heatsink I was having cast I could build an entire and very nice tube amp. On a very hot day in a foundry that was it. I cancelled the order and was out of tranny DIY for good. I agree, the necessary heat sinks are one of the more bothersome mechanical features of solid state amplifiers. Regards, John Byrns Surf my web pages at, http://users.rcn.com/jbyrns/ |
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#3
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Andre Jute wrote: Reply to message Yo, John The key thing you say in your post is 'local NFB similar to the 14 dB or so that is inherent in the 300B at one of the operating points you suggested'. How did you calculate this number or where did you come by it? **** Indeed, I have wondered about the internal FB number myself. Maybe I could answer the question myself. Let us suppose the 300B was a hypothetical perfect pentode, with a screen to prevent any FB at all. Then the Ra would be infinite. But you'd still have a device with a fixed gm And gain, A, for all tubes = u x RL / ( Ra + RL ) also, u = gm x Ra for all tubes. So we can say A = (gm x Ra) x RL / ( Ra + RL ) Trouble is, this only works for finite values of Ra, and where infinite values of Ra exist, its too darn hard to work out what to do to make a simple formula work, but when we measure nearly perfect pentodes with Ra = 1M or greater, and gm say 5 to 10 mA/V, we find A = gm x RL, near enough, where RL = say 10k The maximum gm of the 300B occurs when the load is a short circuit, and there is thus no anode voltage change, and hence no internal applied electrostatic negative feedback. At Ea = 400v, and Ia = 80 ma, Ra = 670 ohms, and u = 5, so gm = 5 / 670 = 7.5 mA/V. So we could say that if the RL was say 5k, then the hypothetical pentode gain would be 5,000 x 0.0075 = 37.5. But in practice with a real 300B triode we get triode u = 5, Ra = 670 ohms so gain = 5 x 5,000 / (5,000 + 670 ) = 4.4. We see a gain reduction with a 5k load of 4.4 / 37.5, or about 8.5 times, so that's about -18dB. So what is causing the reduction of gain from 37.5 to 4.4? Its the NFB of course. So what amount of series voltage FB would have to be applied to a current source with gm = 7.5 mA/V to give a gain reduction of 18 dB into a 5 k RL? If you had a normal resistor network to deliver conventional NFB to the hypothetical 300B pentode, we would have to ignore the loading effects of the resistance network, so let's have a hypothetical divider, so we can establish what the B is for the feedback network, B being the fraction of the output voltage fed back in series with the input to the grid. The gain with FB applied is A' = A / (1 + [ A x B ] ). Thus we get 4.4 = 37.5 / ( 1 + [ 37.5 x B ] ). Therefore, 37.5 = 4.4 + 165B. B = 0.20. Therfore, if we had a perfect pentode, gm = 7.5 mA/V, and a divider network so that 0.2 x the anode voltage was applied in series with the grid voltage at the cathode, you'd have the equivalent circuit for a 300B triode. So if you have +122 vrms at the 5 k load, ( 3 watts ), and you had a perfect pentode, you'd have -24.4 volts of NFB applied to the cathode, and 3.26 vrms applied between the grid and cathode, so you'd need -27.66v at the grid. 122 / 27.66 = 4.4, the gain of the triode, so I have verified the hypothetical operation. The Ra of a pentode is reduced by the NFB so that Ra' = Ra / 1 + [ u x B ] ). Infinity doesn't rest well in our equations, so let's choose Ra = 20k... u = gm x Ra = 0.0075 x 20k = 150. So Ra' = 20,000 / 1 + [150 x 0.2 ] ) = 263 ohms This result is what we'd expect with a 6550, set up as a tetrode, with a 20% CFB winding..... In practice we see the Ra of the 300B resting at 670 ohms, ( Svetlana data ) What if Ra = 10 M? Surely this would be close enough to a perfect pentode. u = 10,000,000 x 0.0075 = 75,000. Ra would remain at 0.0075 A/V. Ra' = 10,000,000 / ( 1 + [ 75,000 x 0.2 ] ) = 666 ohms Now this is the value of the 300B triode Ra, so we could assume the 300B was in fact like a perfect pentode/tetrode, but with all this NFB inside it. The load determines the gain of any tube, but what if the load was say 1M? Then its very close to a CCS. Then if you consider the 300B as a perfect pentode with NFB, and B = 0.2 within it, and note that this B figure is 1/u, where u is the triode u, then the pentode gain without NFB would be a gi-normous figure. So even with only 0.2 of the output fed back in series with the input the gain reduction is a huge number, so you get the maximum benefit of the very large amount of NFB applied within the 300B when the load = CCS, or a huge number of times of the triode Ra. Triodes are not perfect, and nor does a perfect pentode actually exist, let alone a hypothetical one, since the electrode structure and the bts holding it in place are never perfect. There are stray electrostatic effects as well as the main ones we are theroretically dealing with. The relationship of plate current vs plate voltage isn't a linear one. The plate data curves show this non linear increase in plate current for a given increase of plate voltage. Yet its this very non linear function on the tube which delivers the voltage feedback within the triode. So one might expect that with so much NFB within a triode when a CCS load is used that the non-linearity of the divider element delivering the NFB would be eliminated. IN practice we see that indeed the triode attempts to do this, but the process isn't perfect, and infact some distortion still occurs with a CCS load, but its a tiny fraction of what you get with a normal power tube load where RL = 4 Ra. That's the other benefit of NFB. Any nonlinearity of the active elements in a chain enclosed by a FB loop tend to be compensated for by the NFB loop. So the thd of a driver stage and the output stage is equally reduced if the loop of NFB includes the two cascaded stages. Let's see what sort of figures you guys come up with. Patrick Turner. PS, I don't have pistols for a dawn shoot-out any more. I have so many holes in my feet I can hardly stand up. So I gave them away to a brash young man who didn't survive long....... The rest of this is smalltalk, of merely transient interest. Yeah, I think you definitely had Pinkerton confused with someone else. We were all misled by the fact that he rode in on Arnie's coattails into believing he would at least know something about transistors. I do actually know that transistors cannot operate in Class A1; that was my very first disappointment with them. I was just making a mild funny at the expense of a humourless twerp who stormed into RAT and immediately offered a pale shadow my current project, which he couldn't deliver, and then started hurling racist abuse at me, backed up with long-discredited Magnequest Scum smears. I think it would be a waste of time to wait for Pinkerman's so-called design. Well before his latest debacle in the NFB thread which dissipated (pun intended) your remaining faith in him, Patrick patiently demonstrated (at greater length than Hugh Hefner's 'philosophy', and in my threads -- don't do it again, Patrick; once is funny, twice calls for pistols at dawn) that Pinky doesn't really have much idea of Class A amps either. This poor gatecrasher's insistence on an emitter follower was just about the final straw for everyone, and he knew it for he took his foolish promise away for 'tests'. Therefore I suggest that if your interest has been piqued, you publish the design you found on your netsite and then those interested can discuss it without reference to Pinky's aborted efforts. Truth is, I think you're all on a hiding to nothing though, one never knows, you might find the journey entertaining. My own moment of revelation in Class A discrete transistor amps may amuse mildly. The zero-return point of marginality in transistors arrived when I realized that for the price of the heatsink I was having cast I could build an entire and very nice tube amp. On a very hot day in a foundry that was it. I cancelled the order and was out of tranny DIY for good. Well, a little twenty minute opamp amp now and again hardly counts as an addiction. Andre Jute John Byrns wrote: In article , (Andre Jute) wrote: Those aren't my rules, John. Iain Churches, who invited this rude fellow Pinkerton to submit a design in return for a little courtesy (which we haven't seen) set the rules. I'm merely supplying information to fit the rules Iain made. The rest of your remarks come down to a suggestion that I retroactively alter the design of the KISS 300B I am embarked on to suit the needs of an interloper. That's a bit tortuous! I think I'll just stick to the straight and narrow of my business and ignore the PinkyTron Borg'o'Blaster until it comes to its inevitable fall. Hi Andre, I went to the trouble of rummaging through many of the posts in the sub threads that I hadn't read, it appears to me that Iain Churches only made the suggestion that Pinkerton should design a transistor KISS amplifier to contrast with your vacuum tube design, it appears that the detailed specifications for the transistor KISS amplifier were provided by you when you stated, "the main parameters he should match are single-ended output, 3W, all of it in Class A1, zero negative feedback". Needless to say my faith in Pinkerton's ability to design a suitable transistor KISS amplifier was badly shaken by his recent demonstration of a lack of understanding of the workings of "NFB". I think I may have had Pinkerton confused with someone else. I was not at all suggesting that you redesign your KISS amplifier to eliminate the feedback that is inherent in triode tubes, what I was suggesting was that the transistor KISS amplifier also be allowed to use local NFB similar to the 14 dB or so that is inherent in the 300B at one of the operating points you suggested. Also class "A1" operation applies to vacuum tubes and does not make sense in connection with transistors, better to simply say the transistor KISS amplifier should operate in class A. I would sum a specification for the transistor KISS amplifier up this way, "the main parameters a transistor KISS amplifier should match are single-ended output, 3W, all of it in Class A, with only local negative feedback at audio frequencies." As an example of a transistor KISS amplifier I will have to scan the old article from Audio magazine that I mentioned and put it on my web site for all to comment on. The design has a number of problems, including the use of late 1950's transistors, and a very high damping factor, but it is a starting point for a design that would eliminate these problems and others. Regards, John Byrns Surf my web pages at, http://users.rcn.com/jbyrns/ |
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#4
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And in addition to what I just said in the previous post about
the amount of NFB in a 300B, the actual dB of applied NFB varies with load. I said 18 dB for a 5 k load, John says 14 dB, but maybe that's for 3.5k. Notice the applied dB of FB falls with load, so that with RL as a short circuit the applied FB = 0 dB. B still remains = 1/u = 0.2 for the 300B. Patrick Turner wrote: Andre Jute wrote: Reply to message Yo, John The key thing you say in your post is 'local NFB similar to the 14 dB or so that is inherent in the 300B at one of the operating points you suggested'. How did you calculate this number or where did you come by it? **** Indeed, I have wondered about the internal FB number myself. Maybe I could answer the question myself. Let us suppose the 300B was a hypothetical perfect pentode, with a screen to prevent any FB at all. Then the Ra would be infinite. But you'd still have a device with a fixed gm And gain, A, for all tubes = u x RL / ( Ra + RL ) also, u = gm x Ra for all tubes. So we can say A = (gm x Ra) x RL / ( Ra + RL ) Trouble is, this only works for finite values of Ra, and where infinite values of Ra exist, its too darn hard to work out what to do to make a simple formula work, but when we measure nearly perfect pentodes with Ra = 1M or greater, and gm say 5 to 10 mA/V, we find A = gm x RL, near enough, where RL = say 10k The maximum gm of the 300B occurs when the load is a short circuit, and there is thus no anode voltage change, and hence no internal applied electrostatic negative feedback. At Ea = 400v, and Ia = 80 ma, Ra = 670 ohms, and u = 5, so gm = 5 / 670 = 7.5 mA/V. So we could say that if the RL was say 5k, then the hypothetical pentode gain would be 5,000 x 0.0075 = 37.5. But in practice with a real 300B triode we get triode u = 5, Ra = 670 ohms so gain = 5 x 5,000 / (5,000 + 670 ) = 4.4. We see a gain reduction with a 5k load of 4.4 / 37.5, or about 8.5 times, so that's about -18dB. So what is causing the reduction of gain from 37.5 to 4.4? Its the NFB of course. So what amount of series voltage FB would have to be applied to a current source with gm = 7.5 mA/V to give a gain reduction of 18 dB into a 5 k RL? If you had a normal resistor network to deliver conventional NFB to the hypothetical 300B pentode, we would have to ignore the loading effects of the resistance network, so let's have a hypothetical divider, so we can establish what the B is for the feedback network, B being the fraction of the output voltage fed back in series with the input to the grid. The gain with FB applied is A' = A / (1 + [ A x B ] ). Thus we get 4.4 = 37.5 / ( 1 + [ 37.5 x B ] ). Therefore, 37.5 = 4.4 + 165B. B = 0.20. Therfore, if we had a perfect pentode, gm = 7.5 mA/V, and a divider network so that 0.2 x the anode voltage was applied in series with the grid voltage at the cathode, you'd have the equivalent circuit for a 300B triode. So if you have +122 vrms at the 5 k load, ( 3 watts ), and you had a perfect pentode, you'd have -24.4 volts of NFB applied to the cathode, and 3.26 vrms applied between the grid and cathode, so you'd need -27.66v at the grid. 122 / 27.66 = 4.4, the gain of the triode, so I have verified the hypothetical operation. The Ra of a pentode is reduced by the NFB so that Ra' = Ra / 1 + [ u x B ] ). Infinity doesn't rest well in our equations, so let's choose Ra = 20k... u = gm x Ra = 0.0075 x 20k = 150. So Ra' = 20,000 / 1 + [150 x 0.2 ] ) = 263 ohms This result is what we'd expect with a 6550, set up as a tetrode, with a 20% CFB winding..... In practice we see the Ra of the 300B resting at 670 ohms, ( Svetlana data ) What if Ra = 10 M? Surely this would be close enough to a perfect pentode. u = 10,000,000 x 0.0075 = 75,000. Ra would remain at 0.0075 A/V. Ra' = 10,000,000 / ( 1 + [ 75,000 x 0.2 ] ) = 666 ohms Now this is the value of the 300B triode Ra, so we could assume the 300B was in fact like a perfect pentode/tetrode, but with all this NFB inside it. The load determines the gain of any tube, but what if the load was say 1M? Then its very close to a CCS. Then if you consider the 300B as a perfect pentode with NFB, and B = 0.2 within it, and note that this B figure is 1/u, where u is the triode u, then the pentode gain without NFB would be a gi-normous figure. So even with only 0.2 of the output fed back in series with the input the gain reduction is a huge number, so you get the maximum benefit of the very large amount of NFB applied within the 300B when the load = CCS, or a huge number of times of the triode Ra. Triodes are not perfect, and nor does a perfect pentode actually exist, let alone a hypothetical one, since the electrode structure and the bts holding it in place are never perfect. There are stray electrostatic effects as well as the main ones we are theroretically dealing with. The relationship of plate current vs plate voltage isn't a linear one. The plate data curves show this non linear increase in plate current for a given increase of plate voltage. Yet its this very non linear function on the tube which delivers the voltage feedback within the triode. So one might expect that with so much NFB within a triode when a CCS load is used that the non-linearity of the divider element delivering the NFB would be eliminated. IN practice we see that indeed the triode attempts to do this, but the process isn't perfect, and infact some distortion still occurs with a CCS load, but its a tiny fraction of what you get with a normal power tube load where RL = 4 Ra. That's the other benefit of NFB. Any nonlinearity of the active elements in a chain enclosed by a FB loop tend to be compensated for by the NFB loop. So the thd of a driver stage and the output stage is equally reduced if the loop of NFB includes the two cascaded stages. Let's see what sort of figures you guys come up with. Patrick Turner. PS, I don't have pistols for a dawn shoot-out any more. I have so many holes in my feet I can hardly stand up. So I gave them away to a brash young man who didn't survive long....... The rest of this is smalltalk, of merely transient interest. Yeah, I think you definitely had Pinkerton confused with someone else. We were all misled by the fact that he rode in on Arnie's coattails into believing he would at least know something about transistors. I do actually know that transistors cannot operate in Class A1; that was my very first disappointment with them. I was just making a mild funny at the expense of a humourless twerp who stormed into RAT and immediately offered a pale shadow my current project, which he couldn't deliver, and then started hurling racist abuse at me, backed up with long-discredited Magnequest Scum smears. I think it would be a waste of time to wait for Pinkerman's so-called design. Well before his latest debacle in the NFB thread which dissipated (pun intended) your remaining faith in him, Patrick patiently demonstrated (at greater length than Hugh Hefner's 'philosophy', and in my threads -- don't do it again, Patrick; once is funny, twice calls for pistols at dawn) that Pinky doesn't really have much idea of Class A amps either. This poor gatecrasher's insistence on an emitter follower was just about the final straw for everyone, and he knew it for he took his foolish promise away for 'tests'. Therefore I suggest that if your interest has been piqued, you publish the design you found on your netsite and then those interested can discuss it without reference to Pinky's aborted efforts. Truth is, I think you're all on a hiding to nothing though, one never knows, you might find the journey entertaining. My own moment of revelation in Class A discrete transistor amps may amuse mildly. The zero-return point of marginality in transistors arrived when I realized that for the price of the heatsink I was having cast I could build an entire and very nice tube amp. On a very hot day in a foundry that was it. I cancelled the order and was out of tranny DIY for good. Well, a little twenty minute opamp amp now and again hardly counts as an addiction. Andre Jute John Byrns wrote: In article , (Andre Jute) wrote: Those aren't my rules, John. Iain Churches, who invited this rude fellow Pinkerton to submit a design in return for a little courtesy (which we haven't seen) set the rules. I'm merely supplying information to fit the rules Iain made. The rest of your remarks come down to a suggestion that I retroactively alter the design of the KISS 300B I am embarked on to suit the needs of an interloper. That's a bit tortuous! I think I'll just stick to the straight and narrow of my business and ignore the PinkyTron Borg'o'Blaster until it comes to its inevitable fall. Hi Andre, I went to the trouble of rummaging through many of the posts in the sub threads that I hadn't read, it appears to me that Iain Churches only made the suggestion that Pinkerton should design a transistor KISS amplifier to contrast with your vacuum tube design, it appears that the detailed specifications for the transistor KISS amplifier were provided by you when you stated, "the main parameters he should match are single-ended output, 3W, all of it in Class A1, zero negative feedback". Needless to say my faith in Pinkerton's ability to design a suitable transistor KISS amplifier was badly shaken by his recent demonstration of a lack of understanding of the workings of "NFB". I think I may have had Pinkerton confused with someone else. I was not at all suggesting that you redesign your KISS amplifier to eliminate the feedback that is inherent in triode tubes, what I was suggesting was that the transistor KISS amplifier also be allowed to use local NFB similar to the 14 dB or so that is inherent in the 300B at one of the operating points you suggested. Also class "A1" operation applies to vacuum tubes and does not make sense in connection with transistors, better to simply say the transistor KISS amplifier should operate in class A. I would sum a specification for the transistor KISS amplifier up this way, "the main parameters a transistor KISS amplifier should match are single-ended output, 3W, all of it in Class A, with only local negative feedback at audio frequencies." As an example of a transistor KISS amplifier I will have to scan the old article from Audio magazine that I mentioned and put it on my web site for all to comment on. The design has a number of problems, including the use of late 1950's transistors, and a very high damping factor, but it is a starting point for a design that would eliminate these problems and others. Regards, John Byrns Surf my web pages at, http://users.rcn.com/jbyrns/ |
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#5
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"John Byrns" wrote
My method is to build two spice simulations of the amplifier in question, one with a normal model for the 300B, or other output triode, and a second one where the model for the 300B has the anode voltage used in the internal anode current equations replaced by the value of the DC plate voltage used, feed into the model on a fourth pin. The difference in the gains of these two models represents the amount of "NFB" internal to the triode. I have now found the data necessary to create a spice model of the 300B, so if I can find my spread sheet that builds the triode spice models from the tube data, I should be able to replace my finger to the wind estimate with a more precise number for the amount of "NFB". Model of 300B is widely available. You don't have to make one, even if you could. So your calculation is based on a comparison with an imaginary device? I take back what I said about your fawning: you clearly need to. Not everyone has an imagination, you could find consolation in that. cheers, Ian |
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#6
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"Patrick Turner" wrote
...[snip]... You seem to have sunk out of sight while I was away, Patrick. I am sorry, I thought your fan club would help. This new lot of friends won't help you to sell much, I fear. I know some say that bad publicity is better than none at all, but I don't think that's always true. Babble away. cheers, Ian |
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#7
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#8
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snip a bunch of crap
It's also the case that the final design is unlikely to be posted before Easter, since this is not a trivial exercise, the holiday season is upon us, it's only a hobby, and much real-world testing is required before arses are laid on the line! :-) -- Stewart Pinkerton | Music is Art - Audio is Engineering look people, just face it already, solid state will NEVER sound as good as tubes, not even close, nor will NFB designs EVER sound as good as those with NONE. please give up! PS - here is an amazing testament, my friend Paul was having problems, all his favorite music was giving him headaches over the last year, when played with any decent volume at all, on an expensive audiophile amplifier as well as on every other device in his house. And his ears would ring for days after listening to it, and the headaches would persist. So I gave him a Dynaco ST-70 to use and the headaches and ringing disappeared for good! Now just imagine if I gave him a DHTSE amp with no NFB? he would probably become obsessed and be out on the street, having spent the family's food and rent on some 110 db exponential horns. Let's stop all the engineering BS and just face the facts, the greatest amps in the world, with price as no object, are less than 3 watts maximum output, and schematics of the best amps on the earth can be found at vt52.com here is what you engineers need to learn, if you ever want to experience the ultimate sound in audio 1. the best sound is in the first watt, it's all downhill from there 2. most all of the best sounding tubes were designed before 1930 3. all of your engineering numbers, and THD measurements,etc. cannot fool the human ear, it is like telling someone that sex with a beautiful woman does not feel good, because your measurements and analysis and oscilloscopes show that it should be better with a big lard-ass fat chick. Sorry, our senses tell us different. please STOP THE INSANITY |
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#9
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"Patrick Turner" wrote Andre Jute wrote: snip... a bunch of crap look people, just face it already, solid state will NEVER sound as good as tubes, not even close, nor will NFB designs EVER sound as good as those with NONE. please give up! PS - here is an amazing testament, my friend Paul was having problems, all his favorite music was giving him headaches over the last year, when played with any decent volume at all, on an expensive audiophile amplifier as well as on every other device in his house. And his ears would ring for days after listening to it, and the headaches would persist. So I gave him a Dynaco ST-70 to use and the headaches and ringing disappeared for good! Now just imagine if I gave him a DHTSE amp with no NFB? he would probably become obsessed and be out on the street, having spent the family's food and rent on some 110 db exponential horns. Let's stop all the engineering BS and just face the facts, the greatest amps in the world, with price as no object, are less than 3 watts maximum output, and schematics of the best amps on the earth can be found at vt52.com here is what you engineers need to learn, if you ever want to experience the ultimate sound in audio 1. the best sound is in the first watt, it's all downhill from there 2. most all of the best sounding tubes were designed before 1930 3. all of your engineering numbers, and THD measurements,etc. cannot fool the human ear, it is like telling someone that sex with a beautiful woman does not feel good, because your measurements and analysis and oscilloscopes show that it should be better with a big lard-ass fat chick. Sorry, our senses tell us different. please STOP THE INSANITY |
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#11
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On Thu, 16 Dec 2004 09:33:56 -0500, Jon Yaeger
wrote: look people, just face it already, solid state will NEVER sound as good as tubes, not even close, nor will NFB designs EVER sound as good as those with NONE. please give up! Why, when you are this full of crap? PS - here is an amazing testament, my friend Paul was having problems, all his favorite music was giving him headaches over the last year, when played with any decent volume at all, on an expensive audiophile amplifier as well as on every other device in his house. And his ears would ring for days after listening to it, and the headaches would persist. So I gave him a Dynaco ST-70 to use and the headaches and ringing disappeared for good! Now just imagine if I gave him a DHTSE amp with no NFB? he would probably become obsessed and be out on the street, having spent the family's food and rent on some 110 db exponential horns. Wow, and I bet even his hamster could hear the difference from the kitchen................. Probably true actually, since nearly all horns sound like ****. Let's stop all the engineering BS and just face the facts, the greatest amps in the world, with price as no object, are less than 3 watts maximum output, and schematics of the best amps on the earth can be found at vt52.com BWAHAHAHAHA! Well, at least you have retained a sense of humour........... :-) here is what you engineers need to learn, if you ever want to experience the ultimate sound in audio We already are - we don't use tubes! 1. the best sound is in the first watt, it's all downhill from there There's some truth in that, but WTF has this to do with tubes? 2. most all of the best sounding tubes were designed before 1930 Most all of the best sounding amplifiers use transistors that were designed after 1990. It's called progress. 3. all of your engineering numbers, and THD measurements,etc. cannot fool the human ear, it is like telling someone that sex with a beautiful woman does not feel good, because your measurements and analysis and oscilloscopes show that it should be better with a big lard-ass fat chick. Sorry, our senses tell us different. That's right, and all really good amps sound the same, because they sound just like the input signal. SETAs do *not* sound the same as each other, therefore they do *not* sound like the input signal, therefore they are crap, however 'nice' they sound. Please note that this has nothing to do with 'numbers', just with properly controlled *listening*. please STOP THE INSANITY Excellent idea! Instead of banging on about tubes, try some properly controlled level-matched blind *listening* tests. It's always fascinating how you 'subjectivist' guys crap your pants at the idea of *really* trusting your ears................. Kinda reminds me of the commercial where a fellow stuck his naked arm in a fishtank full of mosquitoes . . . . Gee, if you really wanted to sit by the fire, you should have cross-posted to R.O.A. And copied Arny and Pinkie directly. I don't subscribe to r.a.o, too many assholes like 'cowboy' in there. -- Stewart Pinkerton | Music is Art - Audio is Engineering |
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#12
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In article , Stewart Pinkerton
wrote: You might care to consider that my initial response was to the general condition, where my statement was entirely true. 'Valvies' have an intriguing need to quote a particular condition of high open loop THD combined with a very specific amount of NFB, when the rules involving IMD do indeed change somewhat. Desperate defence of an indefensible position, or what? :-) And my response was also to the "general condition", it is not true that the mechanism under discussion occurs only under a "particular condition of high open loop THD combined with a very specific amount of NFB". NFB will create higher order harmonics in the output of the amplifier with feedback, that weren't present in the output of the amplifier without feedback. It only appears that this isn't occurring because unlike the mechanism creating second harmonic distortion, it is the result of a higher order function, so when the open THD is low, the higher order harmonics created by the feedback become very low in level and are lost in the noise floor. If you are an *honest person*, and since I do not know you, this is a straight inquiry, you may care to compare your scorn at my lack of picking up this *very* specific NFB condition, with your lack of scorn that Patrick (whom I acknowledge is a very skilled designer) failed to remember that a single-ended amp is limited to its bias current, not twice that amount (since he snipped this out of his response to my post, I assume that he knew this, but was embarrassed by his brainfart and chose to dishonestly bury it), and by your lack of scorn for Andre's *innumerable* innacuracies. First as I said this effect isn't limited to a "*very* specific NFB condition", it occurs under virtually all conditions of "NFB" when there is distortion present in the open loop transfer function, you may just not notice it under some conditions. As far as what Patrick may have said, or not said, I can't be held responsible what Patrick says, and in any case there are way too many posts in the various "KISS amp" threads to follow them all, I have probably been reading at the very most 10% of the relevant posts, so it is entirely likely that I didn't even read the post you are referring to. I am pretty much reading only Andre's "KISS amp" posts, and the various posts relating to transistor "KISS" amps, I am not following what Patrick may be saying about "SE" triode amps in these threads. BTW, in terms of who said what first, I do claim precedence for the term KISASS (Keep It Simple, And Solid State!). It should be obvious that those who followed with KISSASS, both missed the point and were tempted into trying to score a cheap pun. I fully realize that you originated the "KISASS" moniker, and I don't believe I have claimed otherwise. In regards to my changing it from "KISASS" to "KISSASS" it wasn't an attempt on my part "to score a cheap pun", but was rather due to the fact that I couldn't find the message where you used "KISASS", and I wrongly assumed that it was "KISSASS" that you had used, which I thought stood for "Keep It Simple Stupid, All Solid State", so that is what I mistakenly used and the rest is history. I guess I take precedence for the term "KISSASS" even if it was by accident that I created it. And what's wrong with cheap puns, they are the best kind? In conclusion, I've also decided that a true KISASS amp should maintain the simplest possible circuit, but should address the properties of the active devices employed, rather than simply apeing the valve equivalent. Hence, it may employ emitter followers, and it may even employ push-pull operation. It will however have a minimum total parts count, it will operate in Class A (there are no sub-classes for SS amps, despite Jute's ignorance of this), and it will not employ global NFB or iron. Anyone who considers this to be heresy is free to state their case - but it would be nice if that case contained logic, rather than the kind of prejudicial content-free posturing which characterises Jute's posts. I have nothing against emitter followers, or "iron" for that matter, a minimum parts count is the main goal from my point of view, with the secondary goal of making it an "SE" amp. Reading between the lines it sounds like you plan on making the "KISASS" a PP design. I agree that once you do away with the "iron" there is little reason from an engineering perspective not to make it push pull, in fact there are many reasons that argue for a push pull design, but there is more than engineering, and bean counting, to be considered. Regards, John Byrns Surf my web pages at, http://users.rcn.com/jbyrns/ |
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Stewart Pinkerton wrote: On Thu, 16 Dec 2004 14:58:33 -0600, (John Byrns) wrote: In article , Stewart Pinkerton wrote: You might care to consider that my initial response was to the general condition, where my statement was entirely true. 'Valvies' have an intriguing need to quote a particular condition of high open loop THD combined with a very specific amount of NFB, when the rules involving IMD do indeed change somewhat. Desperate defence of an indefensible position, or what? :-) And my response was also to the "general condition", it is not true that the mechanism under discussion occurs only under a "particular condition of high open loop THD combined with a very specific amount of NFB". NFB will create higher order harmonics in the output of the amplifier with feedback, that weren't present in the output of the amplifier without feedback. It only appears that this isn't occurring because unlike the mechanism creating second harmonic distortion, it is the result of a higher order function, so when the open THD is low, the higher order harmonics created by the feedback become very low in level and are lost in the noise floor. Well yes, but we are now in the field of mathematics, since there's no way that you'll be extracting those miniscule artifacts from the depth they're buried beneath the noise floor. Ergo, who cares? The artifacts produced by moderate amount of NFB up to say 20 dB in amps with high open loop thd, say 10% where the measurments are taken, the artifacts are way above the noise floor. And even if things are a bit noisy, it isn't to hard to filter out the single harmonic one is after with a high Q filter, even if its "in the noise" at say -80 dB. The products can all be worked out mathematically, but not by me, not this week, but perhaps some dude has produced a simulator program which does it all for us after we have dialed in the open loop gain, thd spectra, bandwidth. If you are an *honest person*, and since I do not know you, this is a straight inquiry, you may care to compare your scorn at my lack of picking up this *very* specific NFB condition, with your lack of scorn that Patrick (whom I acknowledge is a very skilled designer) failed to remember that a single-ended amp is limited to its bias current, not twice that amount (since he snipped this out of his response to my post, I assume that he knew this, but was embarrassed by his brainfart and chose to dishonestly bury it), and by your lack of scorn for Andre's *innumerable* innacuracies. First as I said this effect isn't limited to a "*very* specific NFB condition", it occurs under virtually all conditions of "NFB" when there is distortion present in the open loop transfer function, you may just not notice it under some conditions. I'm an engineer, not a scientist, so if it's too small to be detected, I don't worry about it! :-) But a shirtload of artifacts produced by the application of NFB may add up to be a noticeable amount of noise. As far as what Patrick may have said, or not said, I can't be held responsible what Patrick says, and in any case there are way too many posts in the various "KISS amp" threads to follow them all, I have probably been reading at the very most 10% of the relevant posts, so it is entirely likely that I didn't even read the post you are referring to. I am pretty much reading only Andre's "KISS amp" posts, and the various posts relating to transistor "KISS" amps, I am not following what Patrick may be saying about "SE" triode amps in these threads. Fairy snuff. I have been reading them all, but that's because it's become an interesting series of threads - apart from Jute's 'contributions'. BTW, in terms of who said what first, I do claim precedence for the term KISASS (Keep It Simple, And Solid State!). It should be obvious that those who followed with KISSASS, both missed the point and were tempted into trying to score a cheap pun. I fully realize that you originated the "KISASS" moniker, and I don't believe I have claimed otherwise. Indeed not, but others have. In regards to my changing it from "KISASS" to "KISSASS" it wasn't an attempt on my part "to score a cheap pun", but was rather due to the fact that I couldn't find the message where you used "KISASS", and I wrongly assumed that it was "KISSASS" that you had used, which I thought stood for "Keep It Simple Stupid, All Solid State", so that is what I mistakenly used and the rest is history. I guess I take precedence for the term "KISSASS" even if it was by accident that I created it. And what's wrong with cheap puns, they are the best kind? Certainly, there are few expensive ones in the world! And I wasn't having a go at you personally in this regard. Chap goes into a music store, asks if they have anything by the Doors. Yes, says the manager, we have the fire extinguisher and a bucket of sand................................ In conclusion, I've also decided that a true KISASS amp should maintain the simplest possible circuit, but should address the properties of the active devices employed, rather than simply apeing the valve equivalent. Hence, it may employ emitter followers, and it may even employ push-pull operation. It will however have a minimum total parts count, it will operate in Class A (there are no sub-classes for SS amps, despite Jute's ignorance of this), and it will not employ global NFB or iron. Anyone who considers this to be heresy is free to state their case - but it would be nice if that case contained logic, rather than the kind of prejudicial content-free posturing which characterises Jute's posts. I have nothing against emitter followers, or "iron" for that matter, a minimum parts count is the main goal from my point of view, with the secondary goal of making it an "SE" amp. Reading between the lines it sounds like you plan on making the "KISASS" a PP design. I agree that once you do away with the "iron" there is little reason from an engineering perspective not to make it push pull, in fact there are many reasons that argue for a push pull design, but there is more than engineering, and bean counting, to be considered. Agreed, it's just that if you avoid an OPT, then most SE designs would incorporate a CCS, which involves a 'gain stage' with similar parts count to a P-P output stage. Then of course you have the 'in-between' approach of the 'active load' as used by Nelson Pass and J L Linsley Hood. So far as I can see, the only difference in KISS terms is that the use of a P-P output stage lowers distortion without employing feedback. Hey, maybe that's why it was invented back in the '20s! Before PP was used, and to save power, ( especially in the BBC mobile recording vans ), choke and transformer coupling was used wherever possible. So if we get rid of CCS and PP, we have parafeed instead for the output. That just leaves the minor problems of how to drive the power bjt with only one other bjt and the use of no NFB. OTOH, I also agree that P-P would immediately result in a red card from the SET brigade, so although it provides higher performance for minimum problems, it should perhaps be avoided for this exercise. This is just idle speculation at this point, as I've packed my slide rule away for the festive season. To convey music, one lone 300B and a single other driver triode is all that is needed for the active circuitry. We wait until his highness has finished the turkey, ham, puddings, and servings of port so that in the fullness of time a working sample of a simple two transistor amp will be presented. Patrick Turner. -- Stewart Pinkerton | Music is Art - Audio is Engineering |
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On Fri, 17 Dec 2004 21:51:33 +1100, Patrick Turner
wrote: Stewart Pinkerton wrote: On Thu, 16 Dec 2004 14:58:33 -0600, (John Byrns) wrote: In article , Stewart Pinkerton wrote: You might care to consider that my initial response was to the general condition, where my statement was entirely true. 'Valvies' have an intriguing need to quote a particular condition of high open loop THD combined with a very specific amount of NFB, when the rules involving IMD do indeed change somewhat. Desperate defence of an indefensible position, or what? :-) And my response was also to the "general condition", it is not true that the mechanism under discussion occurs only under a "particular condition of high open loop THD combined with a very specific amount of NFB". NFB will create higher order harmonics in the output of the amplifier with feedback, that weren't present in the output of the amplifier without feedback. It only appears that this isn't occurring because unlike the mechanism creating second harmonic distortion, it is the result of a higher order function, so when the open THD is low, the higher order harmonics created by the feedback become very low in level and are lost in the noise floor. Well yes, but we are now in the field of mathematics, since there's no way that you'll be extracting those miniscule artifacts from the depth they're buried beneath the noise floor. Ergo, who cares? The artifacts produced by moderate amount of NFB up to say 20 dB in amps with high open loop thd, say 10% where the measurments are taken, the artifacts are way above the noise floor. And even if things are a bit noisy, it isn't to hard to filter out the single harmonic one is after with a high Q filter, even if its "in the noise" at say -80 dB. The products can all be worked out mathematically, but not by me, not this week, but perhaps some dude has produced a simulator program which does it all for us after we have dialed in the open loop gain, thd spectra, bandwidth. If you are an *honest person*, and since I do not know you, this is a straight inquiry, you may care to compare your scorn at my lack of picking up this *very* specific NFB condition, with your lack of scorn that Patrick (whom I acknowledge is a very skilled designer) failed to remember that a single-ended amp is limited to its bias current, not twice that amount (since he snipped this out of his response to my post, I assume that he knew this, but was embarrassed by his brainfart and chose to dishonestly bury it), and by your lack of scorn for Andre's *innumerable* innacuracies. First as I said this effect isn't limited to a "*very* specific NFB condition", it occurs under virtually all conditions of "NFB" when there is distortion present in the open loop transfer function, you may just not notice it under some conditions. I'm an engineer, not a scientist, so if it's too small to be detected, I don't worry about it! :-) But a shirtload of artifacts produced by the application of NFB may add up to be a noticeable amount of noise. As far as what Patrick may have said, or not said, I can't be held responsible what Patrick says, and in any case there are way too many posts in the various "KISS amp" threads to follow them all, I have probably been reading at the very most 10% of the relevant posts, so it is entirely likely that I didn't even read the post you are referring to. I am pretty much reading only Andre's "KISS amp" posts, and the various posts relating to transistor "KISS" amps, I am not following what Patrick may be saying about "SE" triode amps in these threads. Fairy snuff. I have been reading them all, but that's because it's become an interesting series of threads - apart from Jute's 'contributions'. BTW, in terms of who said what first, I do claim precedence for the term KISASS (Keep It Simple, And Solid State!). It should be obvious that those who followed with KISSASS, both missed the point and were tempted into trying to score a cheap pun. I fully realize that you originated the "KISASS" moniker, and I don't believe I have claimed otherwise. Indeed not, but others have. In regards to my changing it from "KISASS" to "KISSASS" it wasn't an attempt on my part "to score a cheap pun", but was rather due to the fact that I couldn't find the message where you used "KISASS", and I wrongly assumed that it was "KISSASS" that you had used, which I thought stood for "Keep It Simple Stupid, All Solid State", so that is what I mistakenly used and the rest is history. I guess I take precedence for the term "KISSASS" even if it was by accident that I created it. And what's wrong with cheap puns, they are the best kind? Certainly, there are few expensive ones in the world! And I wasn't having a go at you personally in this regard. Chap goes into a music store, asks if they have anything by the Doors. Yes, says the manager, we have the fire extinguisher and a bucket of sand................................ In conclusion, I've also decided that a true KISASS amp should maintain the simplest possible circuit, but should address the properties of the active devices employed, rather than simply apeing the valve equivalent. Hence, it may employ emitter followers, and it may even employ push-pull operation. It will however have a minimum total parts count, it will operate in Class A (there are no sub-classes for SS amps, despite Jute's ignorance of this), and it will not employ global NFB or iron. Anyone who considers this to be heresy is free to state their case - but it would be nice if that case contained logic, rather than the kind of prejudicial content-free posturing which characterises Jute's posts. I have nothing against emitter followers, or "iron" for that matter, a minimum parts count is the main goal from my point of view, with the secondary goal of making it an "SE" amp. Reading between the lines it sounds like you plan on making the "KISASS" a PP design. I agree that once you do away with the "iron" there is little reason from an engineering perspective not to make it push pull, in fact there are many reasons that argue for a push pull design, but there is more than engineering, and bean counting, to be considered. Agreed, it's just that if you avoid an OPT, then most SE designs would incorporate a CCS, which involves a 'gain stage' with similar parts count to a P-P output stage. Then of course you have the 'in-between' approach of the 'active load' as used by Nelson Pass and J L Linsley Hood. So far as I can see, the only difference in KISS terms is that the use of a P-P output stage lowers distortion without employing feedback. Hey, maybe that's why it was invented back in the '20s! Before PP was used, and to save power, ( especially in the BBC mobile recording vans ), choke and transformer coupling was used wherever possible. So if we get rid of CCS and PP, we have parafeed instead for the output. That just leaves the minor problems of how to drive the power bjt with only one other bjt and the use of no NFB. OTOH, I also agree that P-P would immediately result in a red card from the SET brigade, so although it provides higher performance for minimum problems, it should perhaps be avoided for this exercise. This is just idle speculation at this point, as I've packed my slide rule away for the festive season. To convey music, one lone 300B and a single other driver triode is all that is needed for the active circuitry. That is of course a misdirection - you need an output transformer, and a smooth supply rail. Speaking of 'cheating', isn't it convenient how when you count the parts for this KISS amp, you guys miss out the massive, expensive and inherently nonlinear, but *essential* if you're using a 300B, additions of an output transformer and a choke-filtered HT rail? It's the sheerest hypocrisy for you to go all hissy fittish about the substitution of a simple CCS 'active load' in the low-impedance BJT equivalent which does not need these 'passive' components. Or do you always insist on using your chisel as a screwdriver? -- Stewart Pinkerton | Music is Art - Audio is Engineering |
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In article , Stewart Pinkerton
wrote: On Fri, 17 Dec 2004 21:51:33 +1100, Patrick Turner wrote: Stewart Pinkerton wrote: OTOH, I also agree that P-P would immediately result in a red card from the SET brigade, so although it provides higher performance for minimum problems, it should perhaps be avoided for this exercise. This is just idle speculation at this point, as I've packed my slide rule away for the festive season. To convey music, one lone 300B and a single other driver triode is all that is needed for the active circuitry. That is of course a misdirection - you need an output transformer, and a smooth supply rail. He did say "active circuitry" after all. True an output, or matching, transformer is generally required with tubes, but the same type of current source, or "active load" circuitry, that you propose for your solid state design can also be used with tubes to reduce the sensitivity to supply rail ripple. Also don't forget that your solid state design will require a humongous output coupling capacitor to isolate the speaker from DC voltages. Speaking of 'cheating', isn't it convenient how when you count the parts for this KISS amp, you guys miss out the massive, expensive and inherently nonlinear, but *essential* if you're using a 300B, additions of an output transformer and a choke-filtered HT rail? The transformer non linearity that you speak of doesn't seem to amount to a hill of beans in the real world, for years many of the world's finest recordings were made with dozens of transformers in the audio path. As far as the need for a choke filtered power supply, that can be dispensed with in a tube amplifier by employing the same methods as you are proposing for your solid state design. Once an "active load" is in place a common 70 volt to voice coil transformer will suffice to match a low impedance tube to the speaker voice coil. Several European radio manufacturers actually used this "active load" scheme, and even used a high impedance speaker to eliminate the need for a matching transformer. Here in the US Sylvania suggested such a circuit in the tube data for one of their high current low voltage pentodes. It's the sheerest hypocrisy for you to go all hissy fittish about the substitution of a simple CCS 'active load' in the low-impedance BJT equivalent which does not need these 'passive' components. Or do you always insist on using your chisel as a screwdriver? It is interesting to speculate on the circuit you are considering for your "KISASS" design. From the above statement it is clear you are contemplating using an "active load" rather than a simple current source, which effectively makes it a class A push pull amplifier. I have no trouble with push pull as long as the "KISS" maxim is followed. You said in another post that your intention was "to string together a two-stage BJT amp with not a stitch of global NFB, and which *is* useable and listenable." I am suspicious of your use of the word "stage" here, by which I suspect you don't mean a single active device, or even two in a push pull configuration. You have mentioned Darlington transistors several times which leads me to suspect that you are considering a Darlington pair to be a single stage. You say that you aren't going to use any global negative feedback, but it is hard to conceive of a two transistor amplifier, excluding the current source, with local feedback, and the necessary voltage gain, small though that may be, where the local feedback isn't the same thing as global feedback. It also isn't entirely clear how you would achieve the needed gain if you only use a Darlington pair as an emitter follower, which you have mentioned previously. Since Andre's specifications for the "KISS" amplifier are spread across several posts I would like to review them here, as I understand them up to this point. Power output of at least 3 Watts. 2 volt input to drive the amplifier to a 3 Watt or greater output Input impedance of 10k Ohms or greater Class A operation No negative feedback Single Ended output stage "KISS", along with good sound is the primary criterion of this design. If it were up to me I would make the following amendments to Andre's specifications. I would delete the no negative feedback and Single Ended output requirements, and let the proof be in the listening. I would restrict the number of discrete active devices to no more than a total of four, including those in any current source or "active load" that might be employed. I would require that the amplifier be capable of delivering a minimum of 3 Watts into an 8 Ohm load when driven by a 2.0 volt input. I would further require that nothing more than a simple voltmeter should be required for a home constructor to achieve proper performance from the design. I think these amendments better recognize the reality of transistor application, as well as closing a few loop holes. The final judgment comes down to a combination of "KISS", hence the limitation to four active devices, and good listening qualities, hence the elimination of the dogmatic prohibitions against push pull circuits and negative feedback. To summarize, my "KISS" requirements would be as follows: Power output of at least 3 Watts into an 8 Ohm load. 2 volt input to drive the amplifier to a 3 Watt or greater output Input impedance of 10k Ohms or greater Class A operation No more than four discrete active devices No restrictions on circuit topology or feedback Regards, John Byrns Surf my web pages at, http://users.rcn.com/jbyrns/ |
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