C.mon ,that Hypex diagram show what is show , precise&clear non-linear THD plot in function of output power , measured with fairly good AP instrument,
btw, very important to note is that most of measuring diagrams for many D class amps don`t (intentionally) shows what`s the spectrum high above 20Khz , where we can found to much RF noise generated by amp.
Please, as made clear in post one, it is an assessment that simply looks at several technical factors to determine the overall design/technical quality of the amp - not sound quality or anything subjective. That has been specifically excluded from the system because it is a personal preference that determines what sound you like. Can I make it any clearer? There will be no subjective sound quality parameters measured in this system. None. Zero.
Once again, why is this being proposed? Because there is a mad dash by almost every designer for 0% distortion and little or no consideration for other things - I pointed out an example from this forum from a month or two back. Secondly, if you focus exclusively on just one parameter, manufacturers, and DIY builders, will quickly home in on that and at worst game the system to get the best result in that one parameter: THD. What about stability? What about load drive capability? How does the amp deal with complex loads? Does it have basic protection? does it hum because the internal wiring and PCB layout are bad?
This thread is thrashing around here because people are trying to make the tool something it is not intended to be. There is no confusion, the concept is clear. If you have numbers to add or discuss constructively, put them on the table.
We = anyone willing to contribute constructively within the framed parameters of the tool and participate in the initiative. If you do not like the concept or think it doesn't meet your needs, skip it and don't consider yourself part of the 'we'.
Test number 4 -> THD+N
"This test is measured at 1 dBV so the output signal is 2.8V pk~pk."
1dBV is 3.17Vpp
Only amps with low voltage gain (10x or less) can have low THD+N at low power levels.
A good amplifier has, say, 1uV input referenced noise. At gain 30x, the output unweighted noise is 30uV (bandwidth 20k). 30uV is -90.5dBV
So at 1dBV output, THD+N cannot be less than -91.5dB => 0.00266%
"This test is measured at 1 dBV so the output signal is 2.8V pk~pk."
1dBV is 3.17Vpp
Only amps with low voltage gain (10x or less) can have low THD+N at low power levels.
A good amplifier has, say, 1uV input referenced noise. At gain 30x, the output unweighted noise is 30uV (bandwidth 20k). 30uV is -90.5dBV
So at 1dBV output, THD+N cannot be less than -91.5dB => 0.00266%
Since you've decided to answer only one of the questions I've asked to PMA for him... okay. Thanks for that. Now, let's go through the rest of your rant ...
I fully and completely support "not sound quality". However, YOU should be clear that any ratings you choose to assign are not based on your idea of what can be heard or not heard then. You've repeatedly said that certain things are audible or not. If they're audible, they by definition affect sound quality. So, once again, you find yourself in a conundrum. Address it nor not, your call.
Consider me no longer part of the "we". I can't tolerate nonsense.
I wish you the best of luck,
Patrick
I disagree with the "anything subjective" part, but we've beat that horse to death. As mentioned repeatedly, I still support the overall concept.
I fully and completely support "not sound quality". However, YOU should be clear that any ratings you choose to assign are not based on your idea of what can be heard or not heard then. You've repeatedly said that certain things are audible or not. If they're audible, they by definition affect sound quality. So, once again, you find yourself in a conundrum. Address it nor not, your call.
Yay you. You found one example, and yet almost EVERY designer is clamoring for 0% distortion. Just be honest about what you're trying to drive. It's really okay. Hyperbole isn't necessary. My perception is that you'd like people to design, market, and sell, products more in-line with your design philosophy and you want to steer the market that direction with a published metric. No harm in that.
Agreed 100%, and I've said so repeatedly. So, I'm not sure why you thought otherwise.
Well, sure you can. Because there are a number of people that have repeatedly posted that they'd like them included. Not I.
As a lump, where have I indicated anything but my full support for this overall concept. Perhaps what I think are constructive thoughts are not.
I agree. What I've made an attempt toward is providing some thoughts around how your metrics and scoring might align better with your stated goals. Yes, I've also put in some suggestions that would selfishly make it more useful for me (and by extension some others also), but the intent was and is to make your vision closer to reality.
You actually answered one question. Thanks.
Consider me no longer part of the "we". I can't tolerate nonsense.
I wish you the best of luck,
Patrick
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I do not agree. Low noise is important, for decades S/N and THD+N has been measured as a rule at 1W/8ohm, 2.828Vrms. 10W and 100W may be considered optionally. Average listening power is for sure near to 1W and not 10W. And even lower than 1W if we listen to classical music recordings with 60dB dynamics.
Occasional crescendos in classical orchestral music - which test represents these these kind of signals? Hifi is about replaying at original levels I think. 8th row can be up to 110 dB peaks at times... let's consider a speaker 90dB/1m/1w sensitivity and 4 meter distance to sweet spot!?
1W/90dB/1m -> 80dB/4m
110dB-80dB=30dB
1W -> 30dB up -> 447 watt acc to: http://www.mh-audio.nl/Calculators/SoundPressureLevelAndAmplifierPower.html
//
1W/90dB/1m -> 80dB/4m
110dB-80dB=30dB
1W -> 30dB up -> 447 watt acc to: http://www.mh-audio.nl/Calculators/SoundPressureLevelAndAmplifierPower.html
//
Exactly so ! , because within that 0-1W region low distortion is very important for the reason of reproduction of the finest musical details undistorted, by the finest musical details I also mean the finest and very small level harmonics of various musical instruments as well as the human voice, which are characterized by a specific tone color.
Tube and no-global-feedback amplifiers have large deviations due to their output impedance. This is IMO the single biggest reason why tube and no-global-feedback amplifiers sound "different".
I personally miss the slew rate measurement, but I agree that it is irrelevant as long as IMD is good.
I am amazed that given all the attention to THD, no-one has noticed that placing the power transformer between the two channels may not be the best arrangement. 😉
Agreed - S/N is underrated. I measure peak power levels of 100mW with 83dB/W speakers. At that power, low distortion is easy but being quiet is hard.
Ed
One of the tests is into a complex load at high power where THD is measured so it’s a dBr measurement. That’s the one for high power testing of distortion with a real world load IMV. You could add in the noise so it would be a single high power test that does complex load capability, distortion and noise from highly loaded PSU.
THD + N at 1 watt test also in the assessment gives a result in absolute numbers so it allows direct comparison. It is an already standard test as PMA indicates.
Hope fully this covers the bases.
THD + N at 1 watt test also in the assessment gives a result in absolute numbers so it allows direct comparison. It is an already standard test as PMA indicates.
Hope fully this covers the bases.
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Ed, what will you do with a tube amp or a CFA amp that don’t slew limit? The high power IMD will catch gross HF non-linearity (see Cordell et al for example for details on this).
Re the transformer 😉 yes often not optimal but if the loop areas are managed well -115dBr on 15W class A is achievable 😉
Re the transformer 😉 yes often not optimal but if the loop areas are managed well -115dBr on 15W class A is achievable 😉
The slew rate measurement assumes that the amplifier is susceptible to slewing (i.e. constant current source charging a capacitor). Slew rate does not apply to tube amplifiers.
The CFA is susceptible to a tug-of-war between the complementary halves. That may not result in measurable slewing, but the VAS current becomes excessive.
Ed
The CFA is susceptible to a tug-of-war between the complementary halves. That may not result in measurable slewing, but the VAS current becomes excessive.
Ed
What good is comparison of a meaningless number? It says little to nothing about the DUT's suitability for its intended purpose.
EDIT: Not only are there different harmonic structures, there are also different kinds of white noise that sound different. A little hiss, a sizzling frying noise, and or popping impulse noise may all be white. White only means that the future state of the noise is not dependent on its prior state, which implies a flat frequency distribution given enough time. It doesn't mean the noise is 'smooth' just because it looks that way on an FFT, particularly on an averaged FFT.
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Yeah. I have MJL15030/31 in the VAS Darlingtons in their 2nd stage.