Thanks Gerrit Boers for a fresh look at the SET magic 
another interesting article about the last 20 years of low THD
http://www.nutshellhifi.com/library/tinyamps.html
another interesting article about the last 20 years of low THD
http://www.nutshellhifi.com/library/tinyamps.html
Gerrit,
Did you pay attention to the polarity of your speaker? In my understanding, the second order distortion of the SET and speaker can cancel each other, but they can add up too, all depending on how you connect your speaker to the amplifier.
This may explain why you could not reproduce the result of your first measurement, if you connected right the first time but wrong the rest of the time.
Best,
HighVvidity
Did you pay attention to the polarity of your speaker? In my understanding, the second order distortion of the SET and speaker can cancel each other, but they can add up too, all depending on how you connect your speaker to the amplifier.
This may explain why you could not reproduce the result of your first measurement, if you connected right the first time but wrong the rest of the time.
Best,
HighVvidity
whatever "right" and "wrong" may means...
if that's the case, likely he may have accidentally connected them "wrong" (both with "reversed" polarity with respect to what he usually have) the first time he run his test and by chance that way was the truly right one... OK, jokes apart I don't actually believe this is the case... AFAIU he was trying to "test" the ideas of De Lima, thus I guess he knew quite well the importance of relative amp/speaker phase not to double check every measurement with both polarities... (have you done that, Gerrit?)
Yes, I did pay attention to the polarity of the speaker. But there is more to it than just harmonics canceling/amplification. As strange as it may sound, the polarity can also affect the damping of the loudspeaker by the amplifier.
Downside Up, introduction
I'm still working on this, I've got more than 6GB of measurement data that need to be sorted and interpreted.
Also, all previous electrical distortion measurements were voltage measurements. Because speaker are current driven I thought I'd have a look at the current distortion. The attachement compares the results for the NAD C320 solid state amp with my single ended tube amp.
The signal was a multi tone made up of six frequencies. The NAD perform much better in the voltage measurement, but for the current measurement there is hardly any difference.
Of the six tones only the one at 645Hz has a phase angle of 0 degrees for both voltage and current, in fact it is the only frequency in the whole 20Hz-20KHz range where this is the case.
Downside Up, introduction
I'm still working on this, I've got more than 6GB of measurement data that need to be sorted and interpreted.
Also, all previous electrical distortion measurements were voltage measurements. Because speaker are current driven I thought I'd have a look at the current distortion. The attachement compares the results for the NAD C320 solid state amp with my single ended tube amp.
The signal was a multi tone made up of six frequencies. The NAD perform much better in the voltage measurement, but for the current measurement there is hardly any difference.
Of the six tones only the one at 645Hz has a phase angle of 0 degrees for both voltage and current, in fact it is the only frequency in the whole 20Hz-20KHz range where this is the case.
Attachments
Yes and no, no in the sense that I did not further pursue this. Not long after the last post in this thread I completely changed my approach and went from single ended tube amps with single driver loudspeakers to multi way open baffle systems, starting with the Linkwitz Orion, using Class D amps.
I'll be the first to admit that I went over the top in my enthusiasm, I was so full of energy that I was able to quit smoking from on day to the next and I haven't touched a cigarette since. So as far as I'm concerned it was totally worth it
After the initial euphoria the reality sunk in and I started to hear the problems with the single driver approach, coloration (box and driver) and directivity being the most obvious.
At the same time I was playing around with distortion gear for music ( SPL Charisma tube processor) and noticed a similarity with regards to the behaviour of single ended tube amps. Individual instruments and simple arrangements benefit from the effect but 'pad' sounds (choir, strings) and complex arrangements suffer from it. You can add tons of distortion to drum sounds and it will liven them up, use the same setting on a choir and it will just sound broken. In the end I concluded that distortion in the reproduction chain should be avoided.
Building and listening to the Orion system opened my eyes with regards to the importance of directivity and absence of stored energy. In stead of following Linkwitz and building the LX521 I came up with my own design where I tried to optimise directivity and reduce stored energy as much as possible. This became the 'Totem of Tone'. I've been using this system for one and a half years now and as far as I'm concerned this is a 'blameless' system. Of course there are compromises as in any system, vertical directivity being the most obvious, but apart from those compromises I could not hear any faults. This never happened to me before as there was always something that started to nag, once you hear that you cannot 'unhear' it.
Nowadays I don't listen to my system anymore, I listen to the music
regards,
Gerrit
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