bobkatz wrote on Thu, 08 December 2005 17:20 |
danlavry wrote on Wed, 07 December 2005 20:01 |
BK
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You said: "Ironically, you have to support 192 kHz in order to prove it isn't necessary."
Where is the logic here? Do I have to sell poison pills in order to prove that poison is bad for you? Do I need to support 100MHz sample rate in order to prove that such a
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What I meant, Dan, is that if you believe that ultimately a listening test is required, then you have to have the supporting hardware to test it. I do not see much in your written arguments about why 192 is not necessary regarding issues of the effects of the low pass filters on the ear. The ONLY way to test that is to test (including listening) different low pass filters at 96 and 192K sample rates.
That's what I mean by the irony. In order to prove (by listening tests) that you don't need 192, you have to have a converter that does 192!
I agree that 192 is market-driven, hey it must sound twice as good as 96, right? A powerful argument for people who listen with their eyes.
Yes, I know that the Lavry black does 192. But it isn't a Gold, is it?
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BK[/quote]
First, let me clarify something. The LavryBlack does 192, because most of the newer digital audio receivers and DA IC's do 192K. I did not see any reason to add circuits just for disabling it, but look at the LavryBlack front panel, the unit is designed to indicates that it receives 44.1, 48, 88.2 and 96KHz. I did not include the 2 more lamps that would indicate 176.4 and 192KHz, because doing so would support the 192KHz sampling, which by the way sounds worse and measures worse!
Imagine that, for 2 more lamps I could join the 192KHz hype, "expanding my sales"... What would I use for an excuse? Someone told me: "If I don't do it some else will". I need to respect myself, so I can not do it...
Regarding listening to low pass filters:
At what point does one stop getting the ear into the equation? How about 10MHz filter? Or 100MHz filter?
What would happen if you listened to say 100MHz filter, against a 1 inch of wire? Guess what - an opamp capable of 100MHz bandwidth would sound much worse then one aimed at say good 50KHz operation. What conclusion would that bring? That 100MHz is not wide enough?
Of course 100MHz is way off, but I used that example to demonstrate a point. The point is very specific: one hears what the 100MHz does to just a "sliver" of its bandwidth, the audible frequencies. Therefore, before you conclude that what you hear with a filter is due to increased bandwidth, you must be sure that the opamp used does not have a sound, as well as the caps and all, in a very similar circuit, power supply and "environment".
The proper conclustion is: There is an OPTIMAL POINT. More bandwidth and faster sampling is not better. Too little is not good, too much is not either. So where is the optimum? Not at hearing 96KHz audio (192KHz rate). We both know that.
Having said that, let me add the important facts:
1. The analog filters in modern AD's are made with few poles, in the MHZ range, because the AD modulators work at over sampled speeds.
2. The analog filters in modern DA's can operate very fast as well because the DA's are upsampled, thus the image energy is at higher frequencies.
In fact, most analog filters operate very high, and the margins due to AD oversampling and DA upsampling are so large that most gear makers use the SAME ANALOG FILTERS FOR 44.1KHz-192KHz (both for AD and DA).
All that I staed above mean that we do not need to increase the sample rate to "help filter design". In fact, after I shot the argument "more dots is better", the filter argument came in and I shot it down as well, as I explained above. There were other arguments to shoot down, and at the end there is no single credible argument I saw to support 192KHz.
Again, good honest engineering, science (including listening) would call for a "systematic" approach, beginning with what is the hearing range of the ear (you can add to it "feeling sound with other body parts", I certainly do not mind including say 10Hz if we can precive floor vibrations and so on). To establish what a person can perceive, one does not have to move a whole industry to sample by X2 from where it was. In fact, one should test such theories in the analog domain, eliminating the digital audio variables all together. I would start with mics, micpre, power amp and speakers, all capable of the desired bandwidth to test. Instead of tape, or memory, I would have a sound proof room right next to the sound source (mics near the sound source, speaker at sound proof room....
Perhaps there are other better ways to test the ear. My point is - first they went to 192KHz sampling, with mics and speakers at around 20KHz, then they claim benefits, with no suporting data, no credible theory....
Regards
Dan Lavry
www.lavryengineeering.com