Jan, I was NOT trying to change the subject, I just did not want to address it 'head on' as you were trying to 'entrap' me, by demanding absolute proof of my working hypothesis that FM distortion is generated in solid state designs. You want 'peer reviewed' detailed papers, and I can't provide them now. However, like so many early ideas, I suspect that they will follow as a PhD thesis by someone brave enough to tackle the challenge.
This is how TIM first got started in a formal way, back in 1966, in an IEEE paper.
The first thing that we have to establish is the difference between tube and transistor input impedances with frequency and voltage across other parts of the solid state device. That is why I chose Ed Oxner's quote on the input impedance variations of power mosfets as a start. It is from a textbook, so that should have pleased your sense of credibility, as you don't believe me, directly.
Then, when it is well established that solid state input impedances are complex and non-linear, a test could be formulated to measure FM artifacts (if any) that could be generated by each and every solid state device.
Finally, this could be correlated to separate biological evidence that the human ear-brain system is sensitive to these artifacts, as small and as hard to measure as they are.
I am doing all this, JUST to show you and SY, one of the important reasons that I feel that tubes have an inherent advantage over solid state devices, and why successful solid state designers like, Charles Hansen and John Curl, have to be so careful in making our designs, if we are to continue to get listening awards for our design efforts. One slip, and we are off the 'A' list. I have experienced this myself on at least 2 occasions.
This is how TIM first got started in a formal way, back in 1966, in an IEEE paper.
The first thing that we have to establish is the difference between tube and transistor input impedances with frequency and voltage across other parts of the solid state device. That is why I chose Ed Oxner's quote on the input impedance variations of power mosfets as a start. It is from a textbook, so that should have pleased your sense of credibility, as you don't believe me, directly.
Then, when it is well established that solid state input impedances are complex and non-linear, a test could be formulated to measure FM artifacts (if any) that could be generated by each and every solid state device.
Finally, this could be correlated to separate biological evidence that the human ear-brain system is sensitive to these artifacts, as small and as hard to measure as they are.
I am doing all this, JUST to show you and SY, one of the important reasons that I feel that tubes have an inherent advantage over solid state devices, and why successful solid state designers like, Charles Hansen and John Curl, have to be so careful in making our designs, if we are to continue to get listening awards for our design efforts. One slip, and we are off the 'A' list. I have experienced this myself on at least 2 occasions.
Tube amps can have, at times, quite magical speaker driving abilities - that would not - could not be predicted by theory.
My dpa300B amps, zero feedback differential with 300B output tubes and a measured output impedance of around 6 ohms should be a terrible match to anything other than a dead flat impedance curve speaker - yes?
But fire it into any ESL with their typical horrific impedance curve (typically 30 ohms to one ohm), Quads, Acoustats, Martin Logans etc and what comes out?
Beautiful music, with all the apparency of totally flat response, bottom to top, that's what.
A review of these amps by Roy Gregory in HiFi+ said to his complete surprise, they were a PERFECT match for the new full range Martin Logan CLX. The review is available on my site.
The only speaker they have failed to drive are my Apogee Scintillas, with a near perfectly flat impedance curve - unfortunately at one ohm!
Regards, Allen (acuum State)
My dpa300B amps, zero feedback differential with 300B output tubes and a measured output impedance of around 6 ohms should be a terrible match to anything other than a dead flat impedance curve speaker - yes?
But fire it into any ESL with their typical horrific impedance curve (typically 30 ohms to one ohm), Quads, Acoustats, Martin Logans etc and what comes out?
Beautiful music, with all the apparency of totally flat response, bottom to top, that's what.
A review of these amps by Roy Gregory in HiFi+ said to his complete surprise, they were a PERFECT match for the new full range Martin Logan CLX. The review is available on my site.
The only speaker they have failed to drive are my Apogee Scintillas, with a near perfectly flat impedance curve - unfortunately at one ohm!
Regards, Allen (acuum State)
Why do tube amps get such flack about driving difficult loads? I have always found that the only way that I could stand to listen to any ESL, was with a tube amp. Quad's just sound lifeless without tubes to drive them, IMO. Scintilla's are a difficult load for even for the original Krell amplifiers
That’s a very good question Dimitri and if it was measured I wonder how those measurements were done.
Cheers
Dimitri,
I said "apparency of totally flat response"
And no, I cannot support this with measurements. 1/ I have no speaker measuring gear, and 2/ I personally have no need or interest to do so.
Anyone who comes to my shop will hear these amps driving Acoustat Spectra 11 ESLs, and no one has ever complained about lack of audible bandwidth, or frequency response skewing. Most are extremely enthused by the sound they hear.
Regards, Allen (Vacuum State)
I said "apparency of totally flat response"
And no, I cannot support this with measurements. 1/ I have no speaker measuring gear, and 2/ I personally have no need or interest to do so.
Anyone who comes to my shop will hear these amps driving Acoustat Spectra 11 ESLs, and no one has ever complained about lack of audible bandwidth, or frequency response skewing. Most are extremely enthused by the sound they hear.
Regards, Allen (Vacuum State)
There can be very well existing synergistic aberrations introduced on the forward and power response by the voltage divider between output impedance and load's impedance shape. Especially in dipoles creating a more complex than average monopole's near/far field power response blend. Mixing ESLs (especially vintage ones) with high Zout valves and room acoustics, along with psychoacoustics, is talking many parameters. Traditional audiophile slang word for it is ''marriage''.
Well most audiophiles are deaf. 6 ohms output impedance will give really well controlled bass with any loudspeaker too
This is a great contrast to the cables thread, where <0.1dB variations are being bitched over.
Thank you Allen for your honest reply.
Request toCan you please kindly ask Allen to open his own thread in Manufacturers portion, where he can promote his commercial designs? This is not manufacturer's thread.
Allen can apply to the administration if he wants a forum, he is welcome for that. For the time being I will ask him not to continue speakers talk and valve amps in this line level thread especially not without providing engineering content arguments. BT thread is long and arguably had many OT, had become even customary to OT, but lets try to contain that tendency at least from now on. Thank you gents.
This is the situation: An electrostatic speaker should be relatively immune to amplifier source impedance until high frequencies are approached. Then there should be a mild rolloff caused by the amplifier impedance. This could sound pretty good in many cases.
This is what I think is important not to compare it to a direct radiator response to a 6 ohm source, for example.
This is what I think is important not to compare it to a direct radiator response to a 6 ohm source, for example.
Measurements are irrelevant here. Measurements are useful during design and production, however, measurements are irrelevant to listening, since we cannot know by measurements alone how any audio device sounds.
I see such a HUGE varity of topics taken up here, that I do not understand what is wrong in my answering a question regarding tube amps, and getting censored by a moderator for it. When so many outright rude personal attacks are let go.
And as this is my hobby as much as my business, I find a complaint that I am being commercial is just silly, most of us in this thread are audio pro's, and I would never expect to sell something to a DIY forum member anyway.
Regards, Allen
And as this is my hobby as much as my business, I find a complaint that I am being commercial is just silly, most of us in this thread are audio pro's, and I would never expect to sell something to a DIY forum member anyway.
Regards, Allen
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