That may account for a recent experience involving a couple of Pass Labs 600w amplifiers, some large electrostatic speakers and vinyl. Very expensive system. I think think the owner was stunned when after a few seconds of listening I said, "this has a lot of 2nd order harmonic distortion." And, did it ever. Don't know where all the contributions came from, but after a few more of my observations he promised to get the optical phono cartridge working, and warm up all the equipment for much longer before we tried it again. The power amps apparently take a good hour of warm up time to sound their best, but produce too much heat to leave turned on all the time. Maybe around half an hour warm up time the day I listened.
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At this time I have a new power amplifier prototype in a box, waiting for me to test it. I hope to make it almost 2'nd harmonic proof, being fully complementary and cascodes provided throughout the gain stages. Will it sound better than my previous reference with some residual 2'nd harmonic? I hope it will, but for other reasons, like a more linear output stage, 1 1/2 times the power supply capacity, ultra regulation of both noise and RF from the power supplies, etc. We shall see. It will certainly NEVER measure as low as a contemporary IC op amp, but I really don't believe that it has to, given my experience with audio design. This is because with IC op amps, the PRIMARY way to achieve low (static) distortion is through lots and lots of negative feedback.
I will also have a lot of negative feedback, in fact I might choose to remove some of the primary gain to make the amp sound better. It is well known by successful audio designers that the distortion (THD) amount is highly dependent on its order, etc. It is only people here who are not audio designers who think they know better, and that includes you Scott!
I will also have a lot of negative feedback, in fact I might choose to remove some of the primary gain to make the amp sound better. It is well known by successful audio designers that the distortion (THD) amount is highly dependent on its order, etc. It is only people here who are not audio designers who think they know better, and that includes you Scott!
And probably even more didn't really care about 20khz performance in a stadium.
That is a good point, thank you. Could be one of the reasons amplifiers and dacs with measured distortion around -100dB still aren't good enough. I think we could probably count up reasons for dacs why even -120dB measured distortion is not good enough to satisfy some listeners. That being said, I don't want to get into debating re all the possible factors, magnitude of likely effects of each, quality and or replicability of old research, etc. Debate never resolves strongly held beliefs, anyway. As always, you would be very welcome to come by for a visit. Have a nice day.
In a Linear Audio I got, they did cap testing for film. The metallized caps have distortion ranging to 120db-140db across the range. The non-metallized are across the board 140db. To me they sound different and my favorite are non-metallized. Metallized bring out a little "detail" if you're setup is lacking it, but it's not authentic (like SET's, grounding boxes, etc).
I think at this point I'd say the bar is -140db to be sure of everything, if not even lower. But then again I listen the most with an amp that can regularly hit 1% THD and the audibility of everything is very easy, including the caps. So to me it seems like different things have different requirements. I have no ultimate answer for priorities or what things need what distortion levels except in capacitors. If you can't make a non-metallized capacitor sound good, you're doing something wrong.
It's hilarious worrying about distortion with phono, have you seen the data?
I know the're bad. When I was I kid I could not stand to listen to 45 rpm pop records. Even then they were unlistenable by me. I think I mentioned that here before. I assumed the problem was with our home playback equipment quality, only later to find it was because of how the records were cut during mastering as part of the loudness wars to affect radio play popularity.
That does not explain any damping. I am affirming Lenz Law.
The example you supply does not actually happen as a mechanism in this instance, not the way you attempt to try to explain. Perhaps too hard to go into here, but you are making assumptions that don't apply here. You have to ask serious questions as to what happens when one voltage source faces another voltage source? A reduction in current. Nothing wrong with Lenz Law, but its application has to be properly understood with regard to the circumstances. They have to be defined first.
Very simple indeed. But what does that number mean? It means that you have contrived a number. How does it fit the circumstances, what is the mechanism? The beginning of knowledge is to ask questions.
Thanks for the compliment.
Wrong place? Odd that you should say that. Best place ever! I am actually at the best place on the planet for this stuff.
Where was the notion of DF first mooted (and quickly rejected). It was Sydney, Australia, in fact Sydney University, the home of Thiele-Small Parameters.
F. Langford-Smith, born in Sydney, was the first one to use the DF phrase. Then he rejected it on the same grounds that I reject it too, as I was also once a believer (now a long time ago).
It was here, in Sydney University, in 1975 that I raised the subject with the Richard Small and he was the first one to set me straight. And he was right, the subject really annoyed him. I got to understand his maths better and saw the light. DF has no meaning. It was he who set me straight, because I had not asked the right questions.
Would you like me to go into the maths? I mean actually post an equation that proves there is no such thing as DF in loudspeaker alignments? I would be happy to, but will you have an open mind, as I did, when you are shown it?
It is DF that is the claim: Your claim!
What would you call something which has no relevance? Irrelevant?
I must say that is rich. I know that you are trying to provoke me. Very rich indeed.
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I loved them ceramic cartridges and all, still do. Just last night I left a negative comment on Youtube because someone replaced the audio of Steve Marriott's "Itchycoo Park" with some digitally "restored" version ickypoo!
Now that I would like to see. I assume this will all work its way back to what is and what is not current drive. There is actually a trivial experiment to show damping on a speaker, displace the cone and measure what happens when you suddenly release it with the voice coil open and with it shorted. They are different.
At the time I was interested in an actual measurement. I tied a 50g reference weight to a string and rested it on the dust cap then pulled it off suddenly just to get the same stimulus in each experiment. The DC resistance of the VC does limit the difference as do suspension stiffness/damping. Then there is the Carver challenge for those that think DF is meaningless.
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Another case is a bass combo amp placed in the sound room.
With my hifi playing the 12" speaker cone vibrates in sympathy with the in room sound.
With the bass amp turned on the cone vibration decreases significantly but not fully still/stable.
Amplifier DF is the cause of the 'braking' of the cone, but how well does the amplifier provide this current (energy) dumping/quenching and what are secondary effects of this energy presented to the amplifier output terminals ?.
IOW how well to typical amplifiers cope with externally applied energy ?.
Dan.
With my hifi playing the 12" speaker cone vibrates in sympathy with the in room sound.
With the bass amp turned on the cone vibration decreases significantly but not fully still/stable.
Amplifier DF is the cause of the 'braking' of the cone, but how well does the amplifier provide this current (energy) dumping/quenching and what are secondary effects of this energy presented to the amplifier output terminals ?.
IOW how well to typical amplifiers cope with externally applied energy ?.
Dan.
Yeah we used to have the coloured tape on the floor in the lab to mark the phases. But Ed has the problem that he's plugging together things hundreds of feet apart where bad stuff(tm) not only can but WILL happen.
Suddenly fibre optics seems the greatest invention ever!
A quote I heard from a humble expert in his specialised field is "I know f*** all about everything and every thing about f*** all ".
My mantra nowadays too, though I am still getting to the knowing everything about f*** all, and I accept in the grand scheme of things all of us know f** all about everything.
Dan.
When I was a kid I used to race slot cars, 'slotties'. At that time a lot of technological changes were happening, one being dynamic braking of the perm magnet DC motor.
When controller was released it disconnected voltage and shorted tracks supply rails, hence very strong braking.
I believe these things now rev to > 100,000 with insane current draw, have ground effect and of course, dynamic braking.
You could say, high damping factor
No matter what your pursuit is, there's a rabbit hole to go down, check em out:
YouTube
When I was 3 yr. old (1953) my father brought home a Variac to run my Lionel train rather than the rheostats that they usually used.
Hi Scott, happy to:
Qes = (2Pi*Fs*MMs*Re)/(Bl^2)
The Re is the DC resistance of the voice coil. If the Re changes by 10%, such as adding an output impedance (of the amplifier), then it supposedly has a DF of 10. But in actual fact, the Qe has increased by 10%. The amplifier decreases damping, does not increase it.
I have talked at length on this topic, to a number of physicists, one who is also a world-recognised speaker designer/physicist/scientist.
In fact, the above equation has as author Neville Thiele and Richard Small. It was on the basis of this equation that Small changed my mind. I started to look at it from multiple angles, further discussions and could only see one conclusion.
Please note I choose my words very carefully:
Every amplifier, no exceptions, has an output impedance, hence based on the above equation, the amplifier cannot add damping, it can only decrease damping.
It is ascribing a quality to the amplifier it does not have. The amplifier could be used to decrease damping to the speaker, not the other way around.
Richard Small is still around, I wouldn't be typing this out and make myself out to be a liar. Thiele passed away in 2012.
The only thing that could improve damping would be for the amplifier to have a negative impedance. Of course, motional feedback could do that, but that is not really the topic here, right?
Small pointed me to the fact that there are clearly instances where less damping is desirable, when something is already over-damped. So the amplifier is useful to decrease damping, not increasing it. I was not saying this, he said that. Manipulate the Re was entirely acceptable to him. I am somewhat reluctant to do that and told him so.
It's really not about voltage versus current drive. I am so over that. Even if you have a voltage source, it is the current in the coil that causes the necessary motion. They say, follow the money, I say, follow the current. The source impedance of the amplifier doesn't change that. Besides, we have ways of cancelling out the output impedance.
I am very much familiar with the open circuit idea. It sounds very convincing.
But the conclusion is wrong since an open circuit only means that Re has become infinite. That means that there is no electrical Q and hence we are left with the mechanical Q of the driver, so there still will be some resistance to movement.
Nobody is saying that a connection to an amplifier is not needed. The fundamental thought here is that the voice coil needs to see its own impedance, that is the default position in T-S Params.
It is a question of the simple argument that the amplifier would need to have a negative impedance for the amplifier to improve damping. If it was zero, we would have the best available and that is the limit - the best an amplifier can do is not to make the damping worse. The above equation makes that clear.
Besides, the amplifier can only see one impedance at a time (at any one frequency). It cannot see its own output impedance as separate to the Re of the driver. Hence the divide between the two is not something that the amplifier can act upon.
Finally, and perhaps the real physical clincher, you mention motion and when motion of the coil in the magnetic gap, we now have a voltage source. Indeed current would flow if a load was placed upon it. But the Re of the voice coil now effectively become the output impedance, so it has to go through typically 6 Ohm for an 8 Ohm driver. Let us say that the amplifier has 0.6 Ohm output impedance and that should sync any current? Fine, but it has to go through 6 Ohm DC before it gets to the amplifier which will see 1/11th at the end of that.
That means, for any current to flow, 91% of the heat gets dissipated in the coil of the speaker.
Nobody is saying there is no damping. The above equation has never been overturned. It is probably used by loudspeaker designers a thousand times each day. They look at the Qe (or Qes) as to how it affects the total Q (Qt or Qts) so as make their alignments work with a wide variety of amps and output impedances, solid state and tubes. Speaker designers rarely give DF any thought, they just want to get the alignment right.
That is what Small taught, it is all about the alignment, the alignment defines the damping, all of it.
Does that help?
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That would have been gold to a 3yo learning control theory lol.
When I was around 7 I had one like this...
With this I learned lot's of things about lamps and motors and voltage and current and power etc and........and dissipation limits and failure modes of items and materials etc lol.
I can still hear the scratchy contact sound of the rheostat and the smells of things cooking, a Variac would have been choice.
Dan.
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