3dzapper Posted May 11, 2005 Share Posted May 11, 2005 Here is an image of a sine wave recorded using 24 bit encoding at low level to illustrate the noise floor of the equipment under test. Notice the much better symetry than the 16 bit trace. http://forums.klipsch.com/idealbb/files/BURFIG5.jpg Quote Link to comment Share on other sites More sharing options...
sfogg Posted May 11, 2005 Share Posted May 11, 2005 This is the digital audio scope trace I mentioned above. I made this scope picture on a Pioneer DVD-A player that I added a non-protected 192kHz capable S/PDIF transmitter which would pass DVD-A. The top trace is the bit clock. Middle trace is the actual digital audio. In this picture the DAC is being fed Right Justified 24bit audio data (there are 3 ways DACs can take data). I believe I was feeding the DAC fullscale (0dBFS) pink noise for this picture.The MSB is to the left, LSB to the right. If you watch them in action they look just like a VU meter. The louder the signal is the more bits it uses. The blank 8 bits at the start of each channels sample is where the preamble information would go. That is data about the feed but not the audio data itself. Bottom trace is the Left/Right clock. Off the top of my head I can't recall if that being high was for the left or the right channel in this setup. Not shown is the master clock as it really doesn't show much and is too fast to see it and the other traces at the same time. Shawn Quote Link to comment Share on other sites More sharing options...
Spkrdctr Posted May 12, 2005 Share Posted May 12, 2005 Shawn, awesome pics, but you have to get out more! You are making me actually think about this stuff. I'd rather just remember that I have forgotten most of it. All in all, great O'scope shots. Quote Link to comment Share on other sites More sharing options...
colterphoto1 Posted May 12, 2005 Share Posted May 12, 2005 you guys, this makes my head hurt. Michael Quote Link to comment Share on other sites More sharing options...
3dzapper Posted May 12, 2005 Share Posted May 12, 2005 That is a great image Shawn. One is able to count the 24 bits in the second trace. In the two graphs I put up of the low level signal, it looks like the first square looking trace at 16 bit resolution has 6 reference points (bits) while the 24 bit has approx 13. Doesn't this equate to the better sound of the 24 bit format no matter the level? Rick Quote Link to comment Share on other sites More sharing options...
sfogg Posted May 12, 2005 Share Posted May 12, 2005 Rick, "In the two graphs I put up of the low level signal, it looks like the first square looking trace at 16 bit resolution has 6 reference points (bits) while the 24 bit has approx 13. " I don't think it should be. A signal at -90dB on a 16 bit format should be basically using a single bit. On a 24 bit system a signal at -90dB should be using about 9 bits. If by 'reference points' you mean samples keep in mind the bits have nothing to do with that. However many samples there are in a wave is totally decided by sampling rate... and there only needs to be more then two per period. At 44.1kHz sampling a 1000hz wave is sampled 44.1 times per period, at 96kHz (what the 24 bit trace is probably running at) it is sampled 96 times per period. Obviously we aren't seeing 44 or 96 'steps' in either picture. "Doesn't this equate to the better sound of the 24 bit format no matter the level?" It equates to better theoretical signal to noise level no matter what the level. 24 bit signal has a lower theoretical noise floor then a 16 bit signal (-144dB compared to -96dB). A signal at -90dB (from full scale on each) is further away from the noise floor on the greater word length signal. The point I have been 'harping' on though is that is a theoretical difference. There isn't a player out there that actually gives full 24 bit resolution because their own analog circuitry and the DACs aren't quiet enough. For it to actually have a true 24bit resolution their signal to noise ratio must be at or over 144dB. They aren't. The 'best' stuff currently is in the 110 to 120dB SNR range. 120dB SNR is 20 bits of resolution. And also be careful as some equipment is designed such that when it sees 'digital zeros' (part of a test signal for SNR tests) it actually mutes/grounds it's output to artificially inflate SNR test results. From the look of that scope trace you posted of the 24bit source it doesn't appear that it has full 24 bit resolution. The trace is still being distorted by noise... do you know the SNR of that player? And if the rest of the system "isn't up to snuff" from a SNR standpoint then the difference between 16 and 24 bit noise floors really is not an issue as the rest of the system (which includes the room) can't support the difference because the rest of the system is limiting the SNR of everything. Also except for test CDs there really isn't anything out there that uses much more then 40dB of dynamic range. Now... don't get me wrong.... I don't think moving to 24bit is a bad thing. I just don't think it is this major issue that some/many have made it out to be. It tends to be looked at in isolation by itself. But really it should be thought of as part of the bigger picture including the rest of the equipment, the room and what you are hoping to reproduce with it. For a person with a quiet system (total SNR better then 96dB) and an *incredible* room (and I know one guy that has a single digit noise floor in his very very very custom built room) it is possible to build a system with more dynamic range then 16 bit gives you. In other words it is possible to reproduce anything put on a CD without killing the low level stuff from other noises. And in doing so the max playback level is still at a realistically possible listening level. With 24 bits, that quite simply isn't possible. Shawn Quote Link to comment Share on other sites More sharing options...
3dzapper Posted May 12, 2005 Share Posted May 12, 2005 "This is as close as John Atkinson came in his technical review. The Bermester web site does not specify S/N. "Channel separation (not shown) was better than 115dB in both directions below 10kHz, with just a slight decrease evident above that frequency. Fig.2 shows spectral analyses of the player's balanced outputs while it decoded a dithered 1kHz tone at -90dBFS with 16-bit, CD data (top) and 24-bit external data (bottom). The increase in bit depth drops the noise floor by 15dB or so in the treble, implying DAC performance close to 19 bits, which is excellent. There might be a faint hint of some second-harmonic content, but the traces in this graph are otherwise free from spuriae and power-supply spikes. Good engineering" On you comment above JA states: . "Such gamesmanship is not unknownwitness how many CD players mute their outputs when they sense "digital black" data, in order to give an unrealistically good measured signal/noise ratio. But it's hard to see how something similar could be done with the Miller signal without affecting performance elsewhere.John Atkinson " Remember, this Bermester 001 is a $14,000 CD player. Most of us are not in a position to approach that cost. Rick Quote Link to comment Share on other sites More sharing options...
sfogg Posted May 12, 2005 Share Posted May 12, 2005 Rick, " The increase in bit depth drops the noise floor by 15dB or so in the treble, implying DAC performance close to 19 bits, which is excellent. " That actually tells a bit (pardon the pun). 19bits of resolution is 114dB SNR so this has a little below that. That he specifies it as being in the treble implies it has more noise at lower frequency. "this Bermester 001 is a $14,000 CD player. Most of us are not in a position to approach that cost." Cost alone doesn't tell you much. There has been plenty of insanely expensive junk out there too, not claiming this is in that catagory or not. There has also been very well engineered equipment for a lot less money. For example by all accounts this: http://www.benchmarkmedia.com/digital/dac1/ Is an extremely well done unit. Given the same test as the Bermester at 24bit its wave looks cleaner. Note the larger vertical scale, redone to the same scale as the Bermester and it would look smoother yet. This DAC has closer to 20bits of resolution. Though for things like DVD-A or future standards it isn't useful as they don't give access to the digital data directly to be able to pipe it into an external DAC. In both cases neither unit is acheiving anywhere near 24bit performance because of noise within the units themselves. Shawn Quote Link to comment Share on other sites More sharing options...
sfogg Posted May 12, 2005 Share Posted May 12, 2005 "http://www.benchmarkmedia.com/digital/dac1/ Is an extremely well done unit." Forgot to mention price.... the sales tax (in RI) on the first unit would buy the second unit..... Shawn Quote Link to comment Share on other sites More sharing options...
sunnysal Posted May 12, 2005 Share Posted May 12, 2005 no doubt, that benchmark unit is a giant killer! regards, tony Quote Link to comment Share on other sites More sharing options...
Spkrdctr Posted May 13, 2005 Share Posted May 13, 2005 ---------------- On 5/12/2005 12:11:40 PM sfogg wrote: Rick, I just don't think it is this major issue that some/many have made it out to be. It tends to be looked at in isolation by itself. But really it should be thought of as part of the bigger picture including the rest of the equipment, the room and what you are hoping to reproduce with it. Shawn ---------------- Shawn, you stumbled into a very wise statement that can be applied to most any piece of audio gear. We should save the above statement and post it to every topic. A real gem! Quote Link to comment Share on other sites More sharing options...
Audio Flynn Posted May 14, 2005 Share Posted May 14, 2005 no doubt, that benchmark unit is a giant killer! regards, tony +++++++++++++ Anyone done a side by side with the MSB LINK with upsampling? Quote Link to comment Share on other sites More sharing options...
Fish Posted May 14, 2005 Share Posted May 14, 2005 Wow!I'm impressed,Athough I'm with Colter,makes my head hurt.This kinda reminds me of reading instructions to put something together then you just say screw that and look at the picture on the box,lol. On a digital note,I saw someone mentioned never hearing more than 2ch on cd format.I have a few cds when played in a dedicated cd player output 6ch through the digital cable and my pre/pro indicates dts.If this is an answer to a ? nobody ask,please disregard. Finally....this is a great discussion and I can only add that after listening to lps for 30+yrs,cds 20+,hi rez for 5yrs,I have heard all sound great and all sound bad.There's just something about good lps that really sound hifi,no doubt.I also have many very well recorded cds that can sonically compete and a few(mostly left overs from the 80s) that are a disgrace to any recording.I also have a few dvd-audio disc that in 2ch can rival or surpass any album I've ever heard but will agree the format is in a jeopardy,too bad.We now return you to your regularly scheduled programing. Quote Link to comment Share on other sites More sharing options...
sfogg Posted May 14, 2005 Share Posted May 14, 2005 "On a digital note,I saw someone mentioned never hearing more than 2ch on cd format.I have a few cds when played in a dedicated cd player output 6ch through the digital cable and my pre/pro indicates dts." Yup.... sorta. Technically those aren't CDs since the CD format is for PCM audio at 16 bit 44.1kHz. The DTS Music Discs are made to mimic CDs (so that regular CD players will play them) but their data is actually lossy compressed multi-channel. If you ever tried listening to one through your CD players analog output it is just a lot of noise/hash. The DTS on the DTS Music Discs is not quite the same as what is on DVD. On DVD it is a dedicated/flagged DTS track that isn't trying to hide in a PCM track. They data rate on DVDs for DTS is also usually lower then it was on DTS Music Discs. Shawn Quote Link to comment Share on other sites More sharing options...
sunnysal Posted May 15, 2005 Share Posted May 15, 2005 no shootout for me yet, no one down here has a benchmark, but I did hear a system up in NYC with the benchmark DAC and it was a fine sounding system. The owner had dumped an MSB Platinum DAC for it and seemed quite pleased with the benchmark. for now I am quite happy with my MSB. regards, tony Quote Link to comment Share on other sites More sharing options...
Audio Flynn Posted May 16, 2005 Share Posted May 16, 2005 The owner had dumped an MSB Platinum DAC for it and seemed quite pleased with the benchmark. for now I am quite happy with my MSB. regards, tony +++++++++++++++++ I remain very happy with my MSB as well. Upsampling makes it just a bit better on cymbals, snare drum and other instrumental nuances. Quote Link to comment Share on other sites More sharing options...
Benesesso Posted May 30, 2005 Share Posted May 30, 2005 I've been trying to follow this thread, but I'm not sure I really understand it. In my case, I would think that whatever waveform I get beyong ~15k Hz wouldn't matter, because I don't think I can hear up there anymore. So, what can I expect different CD players to dound like with the same "regular" CD in them? Right now I'm using a little JVC XL-P81 portable CD player. Would something with a tube output sound noticably better? If so, why, because from what I've read here the waveforms on the CD will be faithfully reproduced on the JVC. FWIW, I cannot hear any differences when I roll tubes in my Wright 3.5's, driving Khorns. Quote Link to comment Share on other sites More sharing options...
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