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In Reply to: RE: Digital improving -final posted by J. Phelan on April 13, 2016 at 11:06:04
Hi,
> One, CDs, as manufactured, were far from perfect.
> Hence the improvements heard by burning to CDR
> (gold ones were better) or using optical treatments
> (like Optrix).
Again, it is crucial to understand the how and why all these things make an impact.
> Hard-disk also made improvements over CD-drives.
Not really. Head over to the computer audio asylum if you don't believe me.
> All of these point to problems with read-in.
> More power supplies help, but the problem still persists.
Unless CD's are badly mangled, the "read-in" is bit-accurate.
The problem is crosstalk via power supplies. How do I know? I designed a CD-Player that was impervious to "burning CD's to CDR" and Optrix etc... And yes, the trick is power supplies - solely - separating power supplies as much as possible.
> Any modern-engineer working with magnetics will tell you they're
> not easy to shield !
Then these "any modern-engineer" should all be fired to the last man.
In the 1930's, 1940's, 1950's, 1960's, 1970's, 1980's and 1990's Magnetic components were easy to shield. In fact they still are as easy to shield today. I implemented shielded mains transformers in HiFi gear in the 2000's. It is not only possible, but also cheap, relatively speaking, but it is not free.
These days I work with magnetic components for high frequency power supplies and guess you what - they are also shielded, from the factory. Yes, they cost a few cent more than unshielded types, but they are readily available off the page.
> Feedback might very well be an issue -as reported by engineers
> working today. Ayre, DarTZeel and Hegel claim it and I believe it.
I have been using "non-nfb" circuitry for ages. Also circuitry with feedback. Both can be made to work well, you just have to understand the requirements of the circuit.
I will decline to comment on specific products or brands...
> And in these reviews, they discuss "downsampling". Do some reading.
I have. These reviews discuss using Asynchronous Sample Rate Conversion (ASRC), with the output sample rate set to or near 96kHz. And it is an old hat, a specific Pro-audio DAC resampled everything to 100kHz as of appx. 2005. Others like it were fairly common at the time, even in super cheap DAC's there was an ASRC. The manufacturers just forgot to claim downsampling as feature...
This may be because for CD standard Audio you get UPSAMPLING, not downsampling. Yes, with 176.4kHz and 192kHz you get downsampling - doing that if you have 768kHz capable DAC should probably be considered the same sort of thing as putting antifreeze into wine.
Personally I cannot say I am a great fan of ASRC and prefer any Audio Format to be rendered with as little digital processing as possible (which would be non).
Seems the UPSAMPLING/ASRC craze of the early 'oughties is doing a second coming, this time called DOWNSAMPLING, because by now we all know "upsampling = bad".
> Jitter creates -unwanted signals- in the chain
Generally Jitter does NOT create any direct signals that are independent of the actual signal. If you play digital silence there is no erroneous signal created by jitter. It creates increased noise with signal and added distortion, mostly of the IMD type.
> It was not "timing" -clocks are extremely accurate !!
Clocks of any kind have many imperfections. The ones commonly found even in so-called super-clocks are neither very accurate long term (this is called wander), short term (this is called jitter) or in an absolute sense (clock frequency), if compared (say) to a Stanford PRS-10.
> The "rounding errors" were discussed by American engineers,
> in several interviews.
This does not make it true or relevant.
If a digital filter is 24 Bit and it's design is competent (a supposition that I will agree may not automatically assumed to be true) the rounding errors will be in 24th bit, or, as no-one has made a 144dB dynamic range DAC in the DAC's noise-floor.
Even if someone made such a DAC, the rounding error would drown in microphone noise of the recording
> With many co. opting not to use "apodizing", they may be right.
Apodising, as I said refers simply to a filter with a cutoff lower than classic half-band. This kind of filter is a very british thing. The inventor, main proponents and/or main implementers are all british.
Apodising filters are currently available as standard only with DAC Chip's from one small british manufacturer. Any other implementation of such filtering would require bypassing the internal digital filter in the DAC Chip and performing the filtering externally in DSP.
Apodising was proposed by Peter G. Craven and for a specific reason. During recording the ADC typically includes a lowpass filter. Since the late 80's this filter is always digital and almost always a sharp rolloff half-band filter (AKA brickwall filter).
By using a lower filter cut-off during playback the playback filter will dominate the impulse response of the system and may be chosen to be very different to the recording filter, optimised for subjective performance. The downside, you loose a few kHz high frequency extension with CD Standard signals.
The benefits or not of apodising or not are indeed debated. I included apodising filters in one product I helped to design - I still prefer to avoid digital filters entirely and to use only analogue domain filtering instead (a british/japanese gig that few others have gotten in on, which does not make it invalid).
> Although it appears that many DACs were not reaching their
> potential, as you noted. But I replaced it with a new point.
I noted that some DAC Chips (very few) had THD & N with high signal levels that was substantially less than the CD Specification even though their noise levels (and/or -60dBFS Dynamic Range) is close to or matches CD Specification.
These kind of DAC Chips used to be very rare in quality equipment, though they had a bit of a renaissance due to publications in Musen to Jikken Magazine by Kusonoki San who showed the first modern "non-oversampling" DAC using these precise chips as "proof of concept".
Those who cannot really design but only copy have since been elevating these chip's in copies of Kusonoki San's designs (in my view incorrectly) to "high end" status.
Finally, please look at some early "Flagship" CD-Players and DAC's (mid to late 80's - say Sony DAS-R1 or Marantz CD/DA-12) and then tell me which of your claimed problems actually plague them and where they are materially worse than a modern CDP/DAC with your supposed improvements if playing 44.1kHz/16 bit material.
Ciao T
At 20 bits, you are on the verge of dynamic range covering fly-farts-at-20-feet to untolerable pain. Really, what more could we need?
Follow Ups:
Optical playback is dead in high-end audio. For a reason. It wasn't complaints over convenience of CD (vs. LP). It was sound, son. Disc treatments and disk drives were better. If you can afford the Esoteric transports, then this changes things. But not too many can stretch for this.This is not a debate over magnetic shielding. My point stemmed from linear power supplies, which have problems. That's why we (now) have Hynes regulators, Bybee shunt devices and (in the last 10 years) the 'switch' to SMPS by many names in audio. Benchmark at the low end of price, and co. like Soulution on the high. SMPS have transformers but are much smaller.
Then, it's not difficult to shield magnetics ? Benchmark engineer said so -but let's say he's wrong, look at the measures they take with hard-disk drives and MRI machines. They do it -but it's not "easy".
On jitter -I'll let you disagree with engineers who say that it's -very much- a separate, undesirable noise. If it's a timing problem, how does this hurt the amplitude/frequency spectrum ? Which it clearly does. And why are outboard clocks better ? The designers will tell you lower noise.
And it's hard to find -anyone- out there who says "clocks are not accurate". You are saying strange (and foolish) things...
Edits: 04/14/16 04/14/16 04/14/16 04/14/16 04/14/16
Now look Mate,
Other than observing the death of optical disks (or rather the progressive disuse of physical objects to store writings, music and video and more and not just in the high end), you are talking utter bollox (as they say on planet anagramia) and spout misinterpreted and misunderstood sales propaganda and buzzwords as science fact.
I mean goodness gracious me, you did not just drink the cool aid, you exhausted their supply and asked for more. Technically speaking your assertions are generally just not sustainable. I am not again going into details, I already did.
Your main gig seems to be that some magic new tech (even if it is the same old wine in new skins or even older spoiled wine in bad skins sold as the latest gimmick) suddenly redeemed CD Standard audio.
It does not do any such thing.
The best playback of the best recordings was always pretty good.
And the worst playback of the worst recordings... Lord have mercy.
I have been exposed (not complete list) to LP, Half track Master Tape, heck, Metal Tape with Dolby HX on my Sony "Buduh Khan" K7 walkman (also had the pro for on site recording, bloody decent on a TDK 60min Metal tape), early PCM on Betamax Tapes, Decca's digital system, true TOTL Flagship early CD Machines, the best early DVD Players on DVD Audio.
Given a good recording - any of them gave musical pleasure and while they all (of course) sound different, preference often was more down to what format the music was available on, rather than the format.
Heck, someone once played me 78 master acetates on a system designed to work with these.
Fuk Mi, I always thought of 78's as "well below No-Fi" until then...
Sure I have favorites, but most if not all of these rule ok.
I own (and occasionally record with) a BBC spec Sony PCM-F1 set, sold to me as "Alan Parson owned this one" with some backing documentation (so he might, or might not have owned/used this unit - I am skeptical but the price was right either way).
That is a "pre CD" digital recording system. The late and great Peter Baxandall declared this device (it is not stock, but modded to final BBC spec which was a diverse set of mods addressing both audio and usability is studio settings) to be "transparent".
It does not oversample, downsample, clocks are generically crystal, the core ADC/DAC Chip is "90dB" only. Yet it is true multibit, filters are analogue (so minimum phase), much of the circuit is discrete (and very clever and by today's High End Doctrine even revolutionary) and does a good job.
I cannot fully agree with Peter Baxandall (read I can hear this mother in a loop - but I actually don't mind it being there, more than I can say for a BBC Studer or K7 or LP).
With a way to get the converted data out of the box and the playback back in (modded with extra SPDIF I/O it rather antedates SPDIF) it is bloody decent and despite predating CD and being "only 15 Bit" it kicks the proverbial out of many of the modern, newlyfangled "High Rez" recording systems.
It is bested handily by a Pacific Microsonic Model 2, but they are so rare and expensive, I cannot justify owning one (if anyone has one going cheap or free - I'll have it - pretty please).
In fact, I have heard nothing looped in between Mic/Mic-Pre & Level Controller/Monitors that betters the PM2 and not a heck of a lot that beats a BBC Spec Sony F1, to my ears and tastes. The Merging Horus also makes a very nice PCM ADC/DAC, never tried the Grimm DSD ADC, supposedly it is also nice in DSD, who knows.
Playback only, CD-Standard material only, the Philips LHH1000/Marantz DA-12 bests Sony F1, as does Sony DAS-R1, Accuphase DP-80 is also very good (that uses a discret-ish current steering DAC).
And of course anything that matches the PMM2 design and is decent (read HDCD Digital filter, Ultra-analogue current-output DAC, good analogue stages ) - think Audio Synthesis DAX UA version - literally matches PMM2 for playback only.
Most later "Flagship" units actually loose out to the early originals and only in the oughties did we see a return to something not miles off the sonic performance of these 20'th century classics in the absolute high end, at (excluing PM) 10 to 100 times the sales price of those original flagship units.
Nothing Delta Sigma comes close to my ears, good hybrids run in PCM do. Some things I worked on in the last decade or so, that dispense with any digital filtering - well, I like them better still.
Never having spend time with it, I think the TotalDAC stuff should be RAD, as should be the top of the line stuff from MSB, but my name is not DeBeers or KruegerRand...
I still f...king miss my heavily modded Shanling CD Player (including SPDIF In) with HDCD Filter, filterless option, dual PCM1704 per channel, passive I/V conversion (shinko Tantalum resistor), non-feedback WE 396A tube analogue (yes, real WE's) with audio note silver coupling cap's, which fed-ex "lost" in the early 2k's.
Sure, insurance paid up, but I could never find another machine of that vintage and those silver caps were Japanese originals, the wire I used too, I really hated to loose this unit. Hope whoever ended up with it enjoys it. Hoping against hope I'll get it back...
Stuff I currently help designing at its best is not that far off that unit, but still.
Of course - different strokes for different blokes. I know which mast I nail my colours to, though.
TL:DR
Ciao T
At 20 bits, you are on the verge of dynamic range covering fly-farts-at-20-feet to untolerable pain. Really, what more could we need?
You make me want to dust off my Sony 507ESD and give it a try again. It was not TOL, but sounded good to me, especially considering it was a late 80's player.
Dave
I wonder if you have listened to half the things you talk about?
Big J
"... only a very few individuals understand as yet that personal salvation is a contradiction in terms."
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