So far it does sound 'better'. What does that mean? There can be thought of music having layers...... sounds not up front and in your face can be heard more easily.... music in the background... depth or a layer behind the front instruments..... some I never heard before on a well known/played CD. I also heard the treble was up a little louder than before..... Further tests will be done to know if this is from the 1-2dB rise or due to lower distortion.... I suspect lower distortion because of the over-all improvement in clarity. All-in-All, the passive LPF is a benefit with players which have a lot of HF noise above 20KHz. [Note the analog signal from CD player goes to an analog input on the DAC-2]
BUT --- I really want to know if this is a contributor to why HD files off the internet sounds so good compared to stock CD player(s). More work to do.
THx-RNMarsh
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It seems if some would spend even a fraction of the cost of some of these high dollar electronic solutions on their speakers and room set ups and even something like using a program like RePhase or digital room correction many of the things people are attempting to make better in electronics of the components would be far exceeded in sound quality. Chasing the minutia of output above 20khz and up rather than fixing the weak link in every speaker system I have ever seen seems to be a misdirected folly.
I'm not saying that Richard is not seeing noises about 20khz, that may be very true. At the same time it seems that any well designed amplifiers and other electronics in the chain should be able to have a 100khz bandwidth and not affect the sound in our hearing range. Hasn't that been a goal for a long time to have a flat response curve up to 100khz in a power amp so that we don't have to have filters band limiting them and affecting the response in the audible range for decades now?
A passive LPF before the amplifier seems to be a reasonable application but at the same time again doesn't the filter need to be selected so you aren't introducing ripple or changes in the audible bandwidth the ultimate goal here? Why fight so hard to have a flat frequency response and even having speakers that can actually get up to 20 or even 24khz and then mess that up with a preceding filter cutting that same bandwidth off? Something just doesn't compute here.
I'm not saying that Richard is not seeing noises about 20khz, that may be very true. At the same time it seems that any well designed amplifiers and other electronics in the chain should be able to have a 100khz bandwidth and not affect the sound in our hearing range. Hasn't that been a goal for a long time to have a flat response curve up to 100khz in a power amp so that we don't have to have filters band limiting them and affecting the response in the audible range for decades now?
A passive LPF before the amplifier seems to be a reasonable application but at the same time again doesn't the filter need to be selected so you aren't introducing ripple or changes in the audible bandwidth the ultimate goal here? Why fight so hard to have a flat frequency response and even having speakers that can actually get up to 20 or even 24khz and then mess that up with a preceding filter cutting that same bandwidth off? Something just doesn't compute here.
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Seems few people here follow close enough the thread. I've covered this before.
The test is about audio distortion from amps which also have to amp HF junk. Of course, you can get better LPF performance than my simple passive filter. Flat as you like. Doesnt matter at this point in time for my purpose to see if my amps are affected by this HF over-sampling junk. Yours may differ. I'm testing susceptibility with several power amps topologies.
D.Self, if you recall, tested the theory that HF coming thru the power supply could affect distortion of audio thru the amp... he found that it did increase distortion. This is a more direct route and fairly high level.... directly applied to the audio input. Whether your CD player has or does not have such HF garbage to deal with, only you and your player maker can know that.
Of course, I can measure such distortion with and without a LPF, also.
I am also trying to normalize the CD player to the HD download conditions to see if there is an audible difference.
THx-RNMarsh
RNM,
No I am following what you are doing and understand to a point about that. At the same time if the noise you are measuring is below the level of the audio signal I would expect a good power amp to be able to handle that up to a fairly high frequency, but below the bandwidth of the amplifier itself and not cause a problem. Perhaps that is a flawed concept but that is what I have believed any good amplifier should do without introducing any additional distortion products. If the noise is below let's say 80Khz and down at the noise floor I would think it should be benign and not be audible in any real sense.
You of course have the test equipment and knowledge to prove this one way or another so go ahead, I will watch what you say and see what conclusions are drawn. I can imagine if you have RF or other noises above the normal flat bandwidth of a power amplifier that you could be very correct that those frequencies are causing some sort of problems, that makes more sense to me.
No I am following what you are doing and understand to a point about that. At the same time if the noise you are measuring is below the level of the audio signal I would expect a good power amp to be able to handle that up to a fairly high frequency, but below the bandwidth of the amplifier itself and not cause a problem. Perhaps that is a flawed concept but that is what I have believed any good amplifier should do without introducing any additional distortion products. If the noise is below let's say 80Khz and down at the noise floor I would think it should be benign and not be audible in any real sense.
You of course have the test equipment and knowledge to prove this one way or another so go ahead, I will watch what you say and see what conclusions are drawn. I can imagine if you have RF or other noises above the normal flat bandwidth of a power amplifier that you could be very correct that those frequencies are causing some sort of problems, that makes more sense to me.
My way to compensate my power amps is as follows since decades:
- Flat bandwidth with miller cap.
- then low pass input filter added for no overshoot of square waves.
This is the minimal compensation for best measures.
Then, when the amp is connected to the all sytem, I use to increase the value of the input filter cap with carefull listening of music.
I Always find an optimal value: transparency is increased while It filter more HFuntil it reach a point where it has an inpact on the audio bandwidth (Phase or levels ?).
I will have to try more poles in the input filter to see if it helps more.
- Flat bandwidth with miller cap.
- then low pass input filter added for no overshoot of square waves.
This is the minimal compensation for best measures.
Then, when the amp is connected to the all sytem, I use to increase the value of the input filter cap with carefull listening of music.
I Always find an optimal value: transparency is increased while It filter more HFuntil it reach a point where it has an inpact on the audio bandwidth (Phase or levels ?).
I will have to try more poles in the input filter to see if it helps more.
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Not all power amp designs can handle the HF without increased distortion (icluding IM). They may amplify frequencies flat to where-ever but not at low distortion at HF as typical PA rise in distortion as freq increases.
The HF level I showed is not at the noise floor. SOME products are at the noise floor but many sold and used have a lot of HF at moderate levels.
And, yes speakers and listening rooms are a worse offender and I have also spent a lot of time in that realm with plenty of hardware and software etal. Going all the way back to multi-band EQ concept to DSP of many types over the years. Just because I am over at this forum at the moment - don't anyone assume I have not looked into the acoustic side of things A Lot.
Of course, I would suggest everyone use CD players (if they use them instead of LP's) that do not have this HF artifact in the analog output.... hopefully at a price everyone can afford.
THx-RNMarsh
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On current feedback amps, i had most of the time such an overshoot on little square waves signals when Miller is set for max bandwidth just at the limit of a bump at HF. Not "substantial", indeed, as you said
It occures in some players. I have no experience with measuring a large number of CD players for this 'problem'. But if your's does it, it happens every time you play a CD.
I did not know that my player did this until recently. When I compare the HD/Hi Res mastered downloads to a CD, there is quit a large difference in the sound quality. I play a music file from memory and output the music signal via Digital port to digital port on BenchMark-2 digital input. The CD player(s) have the HF noise and the BenchMark does not. but, still the sound quality from downloads is higher quality sound..... even with filter on CD player. So there are other issues still to be found. I havent looked at jitter with jitter analyzer yet.
THx-RNMarsh
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RNM,
Isn't the major difference between the CD and the hi-rez download the actual bit rate differences we are talking about when you say the download is superior to the physical CD? Most CD's are still only Redbook quality so I can imagine on a higher resolving system with good speakers the differences do show up. I would not argue that you can't hear a difference, Nyquist be damned on that, I believe that there is more to it than the minimums that have been the standard up to now.
I don't see it as being the problem of out of band noise as much as the difference in actual resolution of the media that you are dealing with. An experiment would be to take your high resolution downloads and add some high frequency noise intentionally above the audible range and see if in a blind test you could then hear that extra noise as any added distortion. As it is it seems you are comparing apples and oranges.
Isn't the major difference between the CD and the hi-rez download the actual bit rate differences we are talking about when you say the download is superior to the physical CD? Most CD's are still only Redbook quality so I can imagine on a higher resolving system with good speakers the differences do show up. I would not argue that you can't hear a difference, Nyquist be damned on that, I believe that there is more to it than the minimums that have been the standard up to now.
I don't see it as being the problem of out of band noise as much as the difference in actual resolution of the media that you are dealing with. An experiment would be to take your high resolution downloads and add some high frequency noise intentionally above the audible range and see if in a blind test you could then hear that extra noise as any added distortion. As it is it seems you are comparing apples and oranges.
Thank you, Richard, that's about what I figured. Understood that if the player does it, it will do it each and every time without fail.
What promted me to ask is the difference in sound between my old Yamaha CDX 993 and my new NAD C 565BEE players regarding their portreyal of ambient clues in the program material and the quality of their treble response. Of course, there are many differences between them which could be the cause or causes for that, the NAD uses a new gen Wolfson DAC, the Yamaha is from the time when it didn't exist. At first, it seemed to me that the NAD wss simply louder in the high range, until I used an SPL meter which clearly indicated that once set up, the difference was practically nil. So, of it's not the objective loudness, than the new DAC must be doing things better than the old one. I hate to use strong words, but the difference is striking, it's as if there's a difference in focus, so to speak. Razor sharp but not intrusive versus slghtly pastel coloured, soft sound, very pleasnt, but missing out on attack and subjective speed.
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You have a good point. Though some here have expressed the belief that you cannot hear better rez than 16/44k. However I am not sure all HD downloads are from masters at higher than 16/44k. There is also the fact the HD downloads are mastered for the HD download requirements (No compression, extraneous EQ etc) or often need to be REmastered from original source to meet the HD standards at certain sites......
But finding all the differences and normalizing will happen but not if HF or any other anomaly exists in one and not the other.
THx-RNMarsh
HI RNMarsh is rega dac with the wm8742 Minimum phase apodizing filter5 http://web.archive.org/web/20090415.../en/Ultra_High_Performance_DAC_whitepaper.pdf
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