He is under the thumb of Big Vinyl.
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Review and Measurements of Benchmark AHB2 Amp
- Thread starter amirm
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God save vinyl..
Is making vinyl records environmentally responsible?
If Buddha was about today he would stream his audio.
Is making vinyl records environmentally responsible?
If Buddha was about today he would stream his audio.
maty
Major Contributor
Tell us what recordings you are using for the evaluation.
Sometimes I listen to some recordings that are unbearable because of their poor quality because my second system is now very resolutive and does not forgive the wrong doing. Songs that I enjoyed many years ago I am unable now.
Bruckner, recording? Year? The current orchestral recordings I can not stand because they are excessively bright because they use a very high tuning.
Just a thought.. could it be that the "cleaner" system ends up being played at a louder level without knowing because there is less distorsion? That might give a headache.
invaderzim
Senior Member
Is running massive server farms environmentally responsible?
I know I have a potentially biased interest in this but here is my view FWIW.
Use a sig gen and apply a 450kHz 250mV rms sine to a speaker and see what you get out in the audible or ultrasonic bands. Sweet Fanny Adams.
if it doesn't generate any response it can't acoustically intermodulate. The problems potentially created in measurement systems are not the same issue.
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I know I have a potentially biased interest in this but here is my view FWIW.
Use a sig gen and apply a 450kHz 250mV rms sine to a speaker and see what you get out in the audible band. Sweet Fanny Adams.
Yes, but the question is if there are "leftovers" further down in frequency. I guess it's theoretically possible, but I also doubt it. It's curious that people have been debating this for some time, but I have yet to see any measurements on it either way.
GrimSurfer
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Big Vinyl? [thinking....]
Oh, you must mean Little Vinyl!
It was pretty easy to see where this guy was going from the start. Make a mildly absurd comment. Then feign hurt to personal feelings when the comment is de-bunked as a means of generating pity/social capital. Then leverage the social capital to introduce more silliness.
Not very sophisticated.
No that's the point I have just made. A speaker simply will have no response to a 450kHz signal. It can't have a non linear response when the response is zero. All it sees is the audio band signal.
Not seeing any measurements is a fair point. Two points to make here. When using dummy loads we see no in band issues with class D. Quite the contrary in fact, it's extremely clean. So the only question is can the acoustic (not electrical feed) output of a speaker show a problem? Well on a theoretical basis I would immediately say no, as we know a speaker will have no response at 450kHz. However we should test this and measure a real output.
I will try and get time over the weekend to perform an acoustic test.
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That goes without saying. My point was rather that the amplifier itself may send out some frequencies which are lower than the switching frequency. As far as I understand it, that's the claim @John_Siau was making in that application note. A loudspeaker can obviously not be demodulated by a 450khz signal, but can it be demodulated by noise between 20 and 40-50 khz, for example, if it's present?
Awesome, thanks!
A potential issue exists for intermodulation in the amplifier if we have an amplifier input signal close to the switching frequency. Ie say a 449khz signal getting into an amp with a switching frequency of 450kHz could produce a 1 kHz spuria.
However this is RF range signals. Any competent amp should not be letting that in and should have an input RF filter. Mine do.
Note that this sort of IM would be easily measurable with normal in band measurements of the type Amir does. It's not dependant on a speaker being attached. It's just not something that you see.
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Try me, you'll lose. I thought this place was different.
Self moderated
Grim, Scott is the last person who needs to be white knighted, but I think you have no idea who he is. Scott designed a large proportion of the best opamps out there (AD712, AD797, AD540...), is an Analog Devices Fellow, and may be the single best analog designer alive- though he might defer to his buddy Barrie Gilbert. Not to embarrass him, but he is one of the two smartest people I've ever known, and I say that as someone who has worked with Nobel Prize winners. His depth of knowledge on analog, digital, mixed signal, metrology, and signal processing exceeds everyone on this forum put together and tripled.
If I were you, I'd pay careful attention to what he says. You may not always agree, but you'll get a cogent, coherent, and intensely honest answer from him.
OP
- Thread Starter
- #719
Let's not make enemies out of each other over nothing. Please move to other threads if this is bothersome.
GrimSurfer
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Good for him. I'm not disrespecting Scott but responding to posts which are apparently incomplete (or I'd be able to clearly discern where he's going... other than along the same path of tortured illogic that we've all seen before).
The thread is measurement of the AHB2. Amir's tests showed astonishingly good results, including a very low noise floor and low THD. Both of which are unquestionably preconditions for good sound.
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