He was a brilliant* mathematician with some of the issues that can come with that. He did indeed do lots of work before he died on MLP (Meridian Lossless Packing) which was Bob Stuarts first attempt to hold the audio world to ransom. DVD-A didn't really take off so he's had a second attempt with MQA.
*Other real mathematicians may not agree and my maffs is not good enough ot be sure I am correct here.
You said it, "Back-EMF = 25 Ohms Part B of impedance". The amplifier sees 42 Ohms pure resistance there is no back emf by any normal understanding.
Is see now 42 is the answer.
I have a question for you. Take a speaker, crossover, and an ideal voltage amplifier (you used it twice now so I can) that has a flat SLP vs frequency as best you can do. Now take that same speaker and add parallel networks to flatten it's impedance keeping the output the same. Now looking at nothing but the two outputs how do you tell them apart?
This is intriguing, it lowers THD?
I maybe have a possible explanation, but I don't want to sound dogmatic about it. Being passionate can get you into trouble.
But it is an intriguing thing you are pointing to. So what we are seeing is an increase in source Z of the amplifier and moving it down the road of the current drive, just a Terry said. That is what the circuit looks like doing.
When I see things like that, I think there must be a mechanism that explains it. Maybe that is unconventional, I don't know, only that it sounds logical to me.
Before long we may have an explanation, but we know an increase in source Z limits the current phase angle of the amplifier. Eventually, that impedance becomes high enough and you get to full-blown current drive. By then the phase angle goes completely to zero.
I think this is the key. My intuition somehow tells me that if you get the current phase angle to zero, this is the actual reason why current drive sounds better? I think there are strong clues there. Pavel (PMA) has already shown that current drive decreases at least some distortions at some frequencies.
I am above all asking questions. Maybe there are answers?
It is known that constant current amplifier reduces speaker distortion at higher frequencies/inductive frequencies ie above the Z min (Z valley) which is above the driver resonance frequency. This is the frequency range of investigation to compare amplifier types, resistive flattening or RC flattening for distortion changes and is area of maximum hearing sensitivity, ie 300Hz-3.5kHz or so. Pavel's test graph of 40Hz>300Hz is driver non/low inductance region so in this case is not useful test to differentiate measured distortion or subjective distortion.
Dan.
Dan.
What is a constant current amplifier and where is the evidence of this 'known'?
EDIT: Saying a test is not useful when you can't even manage a loopback consistently is also a bit rich.
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If you are trying to force current and voltage out of the amplifier to be in phase by adding some sort of flattening network across the load you can do the same by using current drive.
But, on my limited understanding of amplifier operation, any decent amp has no problem in supplying power with very large phase angles (to within the power handling capability of the OPS) with no effect on distortion other than those mechanisms that are well understood - like LSN for example. As discussed in a previous post, you would need an extraordinary amount of return energy (back EMF) to force an amplifier to lose control of the load. As JN has pointed out, this would be exemplified by the inductive return energy from the load driving the amplifier output beyond its rails. Not really something that will happen under normal circumstances.
But, on my limited understanding of amplifier operation, any decent amp has no problem in supplying power with very large phase angles (to within the power handling capability of the OPS) with no effect on distortion other than those mechanisms that are well understood - like LSN for example. As discussed in a previous post, you would need an extraordinary amount of return energy (back EMF) to force an amplifier to lose control of the load. As JN has pointed out, this would be exemplified by the inductive return energy from the load driving the amplifier output beyond its rails. Not really something that will happen under normal circumstances.
Not that hard, take Joe's example with a 42 Ohm peak in impedance. On 20V rails a voltage amplifier would have no problem with 6V out (don't know if that's rms) while a 1A out current amp on 20V rails would clip.
Transformer out valve amps have that pesky problem of transforming impedance, you know like some blow up if you yank off the load. I had a friend who had to pad the outputs of his amps because at parties folks that wanted to chat near a speaker would just disconnect it.
Yeah - tube amps are a bit different because of the OP transformer. Any decent SS amp will do short term current peaks of 30 A (my big one does 60A for 20ms - I actually test it with a fixture I built) - the amp will just sink return current.
He keeps saying he's talking about speakers but he's talking about amps, but he will deny it. Don't be confused by his confusion like John and Richard seem to be although I suspect they just like to add to the confusion.
Dan, I have already explained why I have shown the range 40 - 300 Hz, just because of the microphone placement near the woofer to prevent incorrect measurements. Please re-read above.
I have shown 40 - 300Hz, however I measured 20Hz - 20kHz. Though the plots are not nice above woofer cone critical frequency and due to crossover frequency and phase interactions between woofer and tweeter, distortion is same for the speaker with and without "impedance flattening" in the whole range 20Hz - 20kHz. This procedure of impedance flattening is the dead horse in case that a standard solid state amplifier with voltage output and very low output impedance is used and of course capable to drive the complex load.
Dutch & Dutch 8c active loudspeaker system Measurements | Stereophile.com
It's a lot of money at $12.5k a pair but seems to be preferred to the Kii3 by some. Of course as per the Kii will be hated by audiophiles as takes a digital input and then gets on with it. No tweaking or synergistic amp swaps. Just lovely accurate music.
It's a lot of money at $12.5k a pair but seems to be preferred to the Kii3 by some. Of course as per the Kii will be hated by audiophiles as takes a digital input and then gets on with it. No tweaking or synergistic amp swaps. Just lovely accurate music.
This is rich, the idiot who thinks goop is audible and obviously knows little about EM insults a Phd in physics who is just trying to help him understand. No wonder SY and others have left this forum.
I meant the forum known as diyAudio, there's a whole other world out there......
I linked to this earlier Current Drive
There are handy references at the bottom of the page
I linked to this earlier Current Drive
There are handy references at the bottom of the page
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