What makes a good DAC? - Page 1
Forum section: electronics / general

author: Halcyon
author_rank: Unknown
timestamp: August 29, 2015, 05:23:44 am
content: So I just helped a friend of mine move house, he handed me what was a $6000 CD player. Nothing more, just played standard audio discs. Granted it did have balanced audio out along with the standard RCA analog outputs.It got me thinking... WHY!?! His response was "Oh it has an awesome DAC in it, you'd be amazed". What makes this DAC any better than whats in a regular CD player or a PC sound card? Why would that CD player be any better than playing a disc through my computer or playing a wave file through decent speakers and an amp?Just another audiophool or is there something in this?

author: NiHaoMike
author_rank: Super Contributor
timestamp: August 29, 2015, 05:37:20 am
content: You'll be amazed how expensive pro audio gear gets. Some of that is very good build quality, some of that is premium parts, but it's mostly (relatively) low demand and the pros willing to pay high prices that keeps prices high.That said, I'd be surprised if the analog signal path component cost even add up to $50. I designed a headphone DAC/amp with an analog signal path that is under $20 if produced in volume and you'd be hard pressed to do very much better.

author: retrolefty
author_rank: Super Contributor
timestamp: August 29, 2015, 05:42:49 am
content: Quote from: Halcyon on August 29, 2015, 05:23:44 amMusic listening is a very subjective and emotional experiance. Typical speakers and room acustics will have the most influence on audio 'quality'. Asking others their opinion will again only get you other subjective and emotional experience.So does a $6K CD player sound better then any other CD player? Only a well designed double blind test will tell the facts, but I suspect not.There is a whole high-end golden-ear audio equipment industry selling equipment for ridicules prices too people who have the disposable income and perceive that electronic music reproduction is like wine testing, where the opinion of others 'experts' count more then measurements beyond human perception. Tell the golden-ears that and they will just say you aren't measuring the right thing(s). Ask them to participate in a transparent double blind test and they will have some other excuse to invalidate such testing.

author: DrGeoff
author_rank: Frequent Contributor
timestamp: August 29, 2015, 06:01:13 am
content: Depends on when it was made. Around 1985, CD players were about $600-$800. The technology was different to what is used today. 16 bits resolution was a big deal at 44.1kHz stereo along with anti-aliasing filters. Delta-sigma converters started being used a bit later I think, with oversampling used to allow for less brutal filtering for aliasing components. The CD player you mention may have used very expensive components (at the time), along with better power supplies and balnced outputs. The market would also have been very small for such a player, so to recoup the development and tooling costs the prices tended to be high. This has beed the case with a lot of pro level gear in the past. Nowdays the components are better performing and much cheaper, so prices are a lot less for similar quality.

author: Rasz
author_rank: Super Contributor
timestamp: August 29, 2015, 06:42:27 am
content: Quote from: Halcyon on August 29, 2015, 05:23:44 am-placebo effect-confirmation bias-post purchase rationalizationand few others, Im sure it sounded AMAZING to him after he forked over $6000!

author: Richard Crowley
author_rank: Super Contributor
timestamp: August 29, 2015, 06:52:46 am
content: I hope you got the $2000 power cord for it! It will sound horrible unless you use the $2000 power cord. Oh, and the special audio cables. Only $3000 for a matched pair! And be sure to observe the arrows on the magic cable. You don't want to install it backwards or the audio won't flow properly.Why do you think they call them audiophools?

author: BradC
author_rank: Super Contributor
timestamp: August 29, 2015, 06:57:07 am
content: For $6k with balanced outputs it sounds like a professional grade unit that was originally designed for studio use. Not built down to a price, and not all about the DAC.You want a unit that is guaranteed to go the distance in a 24/7 professional environment for years, you need to pay for it.

author: Richard Crowley
author_rank: Super Contributor
timestamp: August 29, 2015, 07:32:53 am
content: Even the kind of CD players made for heavy-duty broadcasting applications didn't carry price tags like that.$6K puts it squarely into audiophool territory.

author: helius
author_rank: Super Contributor
timestamp: August 29, 2015, 08:26:30 am
content: Prices used to be higher when the technology was newer. But broadcasting CD players are still expensive.http://www.bhphotovideo.com/bnh/controller/home?O=&sku=885003($4K)

author: PChi
author_rank: Frequent Contributor
timestamp: August 29, 2015, 08:32:57 am
content: I along with a friend did compared some CD players many years ago. If the test is carried out carefully by matching the levels between the CD players to a fraction of a dB I couldn't hear any differences. My friend could hear a slight difference which turned out to be the filter that Mission had added to the output of a Philips designed CD player attenuating the bass slightly. This was testing with large floor standing loudspeakers with good bass extension. The difference probably wouldn't have been audible with typical 2 way stand mounted loudspeakers.However loudspeakers are all different and possibly spening $6000 might be worth it.

author: German_EE
author_rank: Super Contributor
timestamp: August 29, 2015, 08:56:03 am
content: The balanced outputs indicate that whoever designed and built this unit may have taken some care. Six thousand dollars? probably a little too high but I would be interested to see inside.So, what makes a good DAC?1) Low noise2) Linear Output, double the number going in and you should see double the voltage.3) Close matching between the left and right outputs4) No switching spikes, some DAC chips have a voltage spike in the middle of their range5) Perfectly flat frequency responseNow all you need to do is make sure all the circuitry surrounding the DAC is built to a similar specification, including the power supply.

author: Halcyon
author_rank: Unknown
timestamp: August 29, 2015, 09:35:08 am
content: Quote from: DrGeoff on August 29, 2015, 06:01:13 amIt's a modern unit, within the last 5 years or so.Quote from: BradC on August 29, 2015, 06:57:07 amDefinitely a "consumer" unit. The only thing professional about it are the XLR connectors on the back. It's not rack mountable and is clearly designed to be shown off in ones entertainment unit. Only very basic features too in terms of functionality.I've seen actual professional units cheaper than this that do a whole lot more.

author: GoldSrc
author_rank: Contributor
timestamp: September 02, 2015, 04:12:59 pm
content: Audiophoolery at its best.But you know, the placebo effect is a powerful thing, and you will probably are never going to make him accept that.I have an old CD player from 1988-89 and it sounds good, and if you take into account that DACs are better than what they were back then, you don't need to spend much to have good sound.

author: kosmonooit
author_rank: Contributor
timestamp: September 03, 2015, 06:18:47 am
content: "I think therefore I am"René Descartes, 17th Century

author: Rasz
author_rank: Super Contributor
timestamp: September 03, 2015, 07:37:30 pm
content: Quote from: kosmonooit on September 03, 2015, 06:18:47 amhow would that fit here? full quote is dubito, ergo cogito, ergo sum, Show me an audiophool that questions ze truth of the Lamp?

author: Mechanical Menace
author_rank: Super Contributor
timestamp: September 04, 2015, 04:31:52 am
content: Quote from: Halcyon on August 29, 2015, 05:23:44 amIf said PC has a decent PSU and you're not using the cheapest leads between the PC and the amp almost certainly nothing, and in any kind of objective measure probably worse. My main test of a sound source is how well it recreates the recorded sound, not how subjectively 'better' it sounds, and the well overpriced stuff tends to do terribly at this. To make it sound 'better' they're almost always too bassy compared to the real world source. Now if your personal preference is lots of bass I'm not saying that's a bad thing. But that's what tone control and/or equalisers are for*.*Well maybe not what equalisers are meant to be for but what they tend to get used for lol.

author: BradC
author_rank: Super Contributor
timestamp: September 04, 2015, 05:56:54 am
content: Quote from: Mechanical Menace on September 04, 2015, 04:31:52 amExcept most PC sound has a very high noise floor, despite however many million dB dynamic range is stamped on the box. My PC hooks into my receiver/amp with a toslink cable. No additional noiseI'm with you on sound subjectivity. I like my EQ flat. My wife hates the sound in my car, which has been tuned to be as flat as is practical across the board. She calls it "lifeless and tinny". If I wind the treble down to nothing and wind up the bass and sub, she thinks it sounds great.A bit like my CRT TV's. I loved Blaupunkt because it has the best accurate colour rendition, but all my friends told me it looked dull and boring. Coming from an exposure to broadcast equipment from a very young age, I grew to appreciate accuracy over sensationalism.

author: coppice
author_rank: Super Contributor
timestamp: September 04, 2015, 05:59:50 am
content: Quote from: BradC on September 04, 2015, 05:56:54 amMost PC sound used to have a horrible noise floor, but that hasn't been true for several years. Its unusual to find a bad example these days.

author: DrGeoff
author_rank: Frequent Contributor
timestamp: September 04, 2015, 06:10:01 am
content: Quote from: BradC on September 04, 2015, 05:56:54 amExcept, of course, it isn't "flat". The space into which the drivers project contributes significantly to the response of the drivers. You will find horrible LF peaks and troughs (maybe your wife is sitting where the LF null is) and HF flutter echoes in most listening environments that have not been appropriately treated. Perform a response plot for the room at the listening position and you will see what I mean. The dips and troughs of an untreated space can easily be +/-20dB. Only acoustic treatment can fix this, eq is useless for fixing room acoustic problems.It always amazed me when audiophools would spend huge amounts of money on ridiculously specified audio components and ignore the single most significant factor in the audio reporoduction environment.

author: BradC
author_rank: Super Contributor
timestamp: September 04, 2015, 06:50:11 am
content: Quote from: DrGeoff on September 04, 2015, 06:10:01 amSorry, when I said flat I meant by actually using an Audessy EQ DSP that compensates for quite a bit of that using multi-point EQ and time correction. I have 2 curves. One is just for me and compensates pretty closely for my head position and the second is a compromise between my head position and the passengers head position. It's actually pretty good, and far better than just a multi-point EQ. I spent a great deal of time with a reference mic setting it up to make the best job of it both I and the software would allow.Coupled with material changes in the vehicle, and extra treatment behind the door skins, it's not perfect, but it's a crap load better than an average vehicle sound environment.

author: DrGeoff
author_rank: Frequent Contributor
timestamp: September 04, 2015, 07:13:38 am
content: Quote from: BradC on September 04, 2015, 06:50:11 amYou sound like you have gone to a lot of trouble. Stock vehicle environments have always been too boomy for me, but make a great check for translation of material after mastering. You can certainly tell when the HPF is not enabled!The problem with EQ compensation is that it only requires head movement of a few centimeters to be out of the sweet spot for which the compensation was performed. Probably the best you can hope for in a car, but definitely not much use for room compensation.

author: BradC
author_rank: Super Contributor
timestamp: September 04, 2015, 09:03:37 am
content: Quote from: DrGeoff on September 04, 2015, 07:13:38 amI spent about $600 on the whole stereo and considerably more than that on the vehicle interior. Cost/benefit says interior mods give better returns, and I'd rather spend a couple of hundred $$ on new head lining material than a bigger sub or extra amp. Head position is important, but it turns out I don't tend to move my head that much. Between the sculpted head-rest and the mirror position I'd be lucky to vary more than 50mm in any direction and then not often.Quote from: DrGeoff on September 04, 2015, 07:13:38 amYes, I have a mate with the Audessy system in his home theater receiver, and it sounds great in his seat but not so crash hot elsewhere in the room.Back to the topic at hand, I've listened to some pretty impressive systems over the years and aside from laptops and motherboards I've been hard pressed to tell a quality DAC from a quality DAC (where quality implies the DAC itself cost more than about $4 qty/1). I've heard some considerable difference between CD players, but none of it is related to the digital signal path and all of it is related to cheap (and I mean *cheap*) consumer gear with the cheapest of cheap analog paths.Unfortunately, with the advent of compressed audio (in both senses of the word) any pretence in accuracy has gone out the window and most people are no longer interested in what the recording engineer intended it to sound like, because the mastering engineer has ruined the dynamics anyway.

author: Mechanical Menace
author_rank: Super Contributor
timestamp: September 04, 2015, 09:30:26 am
content: Quote from: BradC on September 04, 2015, 09:03:37 amCrafted albums dying and going back to the bad old days of them just being a way to resell singles probably has a lot more to do that than compressed audio, especially with how much better (sizewise) lossless codecs are getting and how popular they're becoming. And at least DRM on them where relevant doesn't mangle the audio like it did with CDs.And when it comes to the mixing recording and mastering engineers, or any sort of sound tech when live, have never and will never listen to what the performers want if they can avoid it.

author: Bassman59
author_rank: Super Contributor
timestamp: September 04, 2015, 05:57:10 pm
content: Quote from: Mechanical Menace on September 04, 2015, 09:30:26 amSpeaking as a professional live sound engineer, I can tell you that we ALWAYS listen to what the performers want. Because if we didn't, then we wouldn't be on the gig. If the band wants it loud (My Bloody Valentine, anyone?) that's what they get.Now, also speaking in that capacity, all too often the mix person is at the mercy of the system du jour. I can approve or disapprove of a system in advance, but until I get to the venue, I have no idea whether it is installed properly. There is only so much one can do with equalization. If the boxes aren't aimed at the audience or set up correctly, it's game over before it even begins. All one can do at that point is to make it sound "as good as possible," which is as frustrating for the mix-person as it is for someone in the audience in a bad location. (Did I mention that sometimes mix position is in the worst spot in the house? Under a balcony! Please, just kill me now.)And there are some rooms that should not be hosting shows at all (Wilbur Theatre in Boston, Aragon Ballroom in Chicago, Terminal 5 in NYC, Wellmont Theatre in Montclair, NJ, Electric Factory in Philly, etc etc). Big empty barns with no acoustic control, absolute nightmares.Note I haven't even mentioned what happens when the band's stage volume is out of control.And my friends who mix and master recordings professionally? They all, without exception, hate the loudness wars, but they do what is asked of them by the client. Because there's always someone willing to do the work.

author: kosmonooit
author_rank: Contributor
timestamp: September 04, 2015, 06:03:39 pm
content: Quote from: Rasz on September 03, 2015, 07:37:30 pmSomeone mentioned the placebo effect ...

author: BradC
author_rank: Super Contributor
timestamp: September 05, 2015, 01:07:27 am
content: Quote from: Bassman59 on September 04, 2015, 05:57:10 pmI've spent years doing bands, but I've only done small (nobody) bands in smallish venues (or massive outdoor areas, so no environmental acoustic issue). I'm also a guitarist/bassist and have played live for about 20 years so I know that side of the fence as well. Because I've only done small bands I've not had to contend with the situation where the band has more pull than the promoter, and so I've always dealt with the bands stage volume with the threat if the guitarist touches his volume knob I'll progressively put a foot through each speaker cone until I get the volume under control. He's always the worst offender, and that threat seems to keep the rest of the band in line.As a muso, engineers love me because I know they'll make me sound better than I'm capable of doing myself from the stage so I just do whatever they ask.

author: Marco
author_rank: Super Contributor
timestamp: September 05, 2015, 01:15:30 am
content: Quote from: helius on August 29, 2015, 08:26:30 amAnyone still using one is pretty foolish as well ... the only player necessary is the one in the computer you rip it with.

author: Mechanical Menace
author_rank: Super Contributor
timestamp: September 05, 2015, 04:51:19 pm
content: Quote from: Bassman59 on September 04, 2015, 05:57:10 pmMy experience is nowhere near that level I'll have to admit.Quote from: BradC on September 05, 2015, 01:07:27 amThat's who I was. Quite popular locally, big enough to headline a couple of thousand people venue but a nobody band. I played guitar and trumpet but the biggest problem was always trying to get the vocals audible. Same when we tried getting an EP together. Ended up doing the mixing ourselves just so it didn't sound like an instrumental.

author: Galenbo
author_rank: Super Contributor
timestamp: September 06, 2015, 11:36:43 am
content: Quote from: Halcyon on August 29, 2015, 05:23:44 amIt can be the first CD player that ever existed, price is cheap for that unit.All CD players have a pretty good DAC, so he's right on that. Wasn't it 14bit?

author: linux-works
author_rank: Super Contributor
timestamp: September 06, 2015, 04:33:53 pm
content: one thing not mentioned is how the actually implement the d/a phase.I've seen a rash of cheap 'dollar dac' chips (from TI, even) that have some major gibbs flaws in them. ie, as the average level gets very close to 0db (or, hell, just sits at 0db; thankyou loudness war, sigh..) the internal math overflows and you get clipping or even worse, flipping! an ESS chip (a dollar dac from their line) does the phase inversion problem and some of us who were working on that system had to abandon it once we learned that it does not deal gracefully with high levels (digitally). nothing to do with the analog-out drivers, its all about the digital filtering and overflowing registers.some dacs now have an 'anti clip' feature; wolfsons to dac chips have this and you can lower the output by 1 or 2db, which you will never 'miss' but by them doing this before they send it to the 'math engine' there is much less chance of the gibbs phenom happening. I've never heard a wm8471 dac chip clip, for example, but the pcm5102 and es8023 (iirc) were the crap chips that NEED digital attenuation before you send the signal to them. ie, they're 'cell phone dac chips' where the audience does not care as much and there will definitely be digital processing and atten before the chips ever see it.there's also impulse response. many dacs differ on how well they deal with fast changes.how good is their dc performance? audio is ac by nature and audio dacs often can do poorly as you get lower in freq and approach pure dc.more a problem in receiver chips, but how well do they reject jitter? do they reclock with a fifo? do they have local clocks or derive from spdif? the high end ess chip does poorly on jitter rejection, for example, even though its considered one of the better chips out there.at the other end of the spectrum, an associate of mine creates his own dac chips at the fpga level, not using any ess, akm, ti or wolfson/cirrus chips at all. he has a dac that natively decoded dsd (even 4x dsd) and his spdif receiver is all home-grown fpga as well as the usb uac2 receiver chip. THAT dac is a $10k dac and the designer has the pedigree to demand that pricing from his customers. but off the shelf dac chips are not expensive and not overly hard to design a board for, so its rare that a dac system could justify anything over, say, $1k.and as for implementation details, the better dacs have independant power supply sections for the different functions, sometimes as many as 8 psu sections. that costs board space and money and if done right, lots of r/d time to actually benefit from that level of design detail.would all that be inside a cd player? I doubt it, personally. bd player perhaps, as there is the option of 'high res' audio but on redbook 44.1 cd players? almost a joke that someone would spend that much, in today's money, on a standalone cd player!

author: NiHaoMike
author_rank: Super Contributor
timestamp: September 07, 2015, 07:21:36 am
content: Quote from: linux-works on September 06, 2015, 04:33:53 pmIf you want to "break" a DAC, what waveform would you use? Out of the various audio DACs I have worked with (a high end TI part, some Cirrus parts, and various Realtek, VIA, etc. onboard DACs), I never saw that happen even when I played full scale sine and square waves of various frequencies for testing purposes.My current favorite DAC chip is the PCM1792A. It goes really well with OPA1612 to get balanced audio out along with TPA6120A2 to drive headphones. Would be nice if TI could make a single chip with essentially all three inside for portable applications but maybe the processes differ enough that doing so would compromise too much on performance...https://github.com/NiHaoMike/OpenDAC-HD

author: SteveyG
author_rank: Unknown
timestamp: September 07, 2015, 11:37:02 am
content: Quote from: NiHaoMike on August 29, 2015, 05:37:20 amI don't agree, I started (still need to finish) a multi-channel DAC - I've already spent around £400 on components. Some of the op-amps are serious overkill, but contribute to almost £150 of that cost.

author: JuKu
author_rank: Frequent Contributor
timestamp: September 07, 2015, 12:45:56 pm
content: Quote from: retrolefty on August 29, 2015, 05:42:49 amA double blind experiments give only negative results: If there is no difference, the only conclusion is that the test people, with the test material used, with that equipment and room, could not hear a difference on test day(s). It can't rule out that with some other people could hear a difference in some other environment on a better day. In other words, double blind tells you "Yes, there is audible differences" or "There could well be audible differences, although they did not show up on this particular test." It can't say "No, there are no audible differences."I have yet to measure two audio DACs from different manufactures with identical results.Audible differences? Anywhere in scale "certainly" - "likely" - "maybe" - "minor if any", but by definition, never "certainly not". Ok, with same DAC chips, same output buffer chips and same filter topology and corner frequency, the differences might be subtle enough to say "not likely".

author: retrolefty
author_rank: Super Contributor
timestamp: September 07, 2015, 01:06:27 pm
content: Quote from: JuKu on September 07, 2015, 12:45:56 pmYou sir do not understand the test nor the scientific method. The results are if you can detect a difference or if you cannot hear a difference. Just because you won't commit to a binary question does not invalidate such a test method. Best to stay with wine tasting events.

author: NiHaoMike
author_rank: Super Contributor
timestamp: September 07, 2015, 03:59:36 pm
content: Quote from: SteveyG on September 07, 2015, 11:37:02 amWhat exotic opamps are you using? The OPA1612, despite its 136dB SFDR, costs under $3 each in quantity.Now if you're using electrostatic headphones, the high voltage opamps are indeed very exotic and expensive. Or tubes, which are also somewhat expensive (but considerably cheaper than HV opamps) and have a rather limited lifetime.

author: linux-works
author_rank: Super Contributor
timestamp: September 07, 2015, 05:14:31 pm
content: Quote from: NiHaoMike on September 07, 2015, 07:21:36 amuse very near-0db audio, not test tones. this is clearly audible by listening.I was listening to some lorena mckennit (sp?) music that I own on cd and ripped to flac. her later work is pushed so close to 0db and it stays there for too long. the gibbs problem happens when enough high-level signal sustains for too long and bad implementations overflow, causing major math errors and resulting in output noise or even phase reversals.there is a thread on diyaudio (search for 'audio widget') where the es9023 (iirc) dac chip was used and then a 5102 chip was used. both of these had the gibbs bug and with 20 year old cd's (before they insisted on nearing 0db all the damned time), any dac can play that without overflows. but the newer releases of music is so heavily weighted toward being near 0db and sustaining it, that this causes many dacs to 'flip out' (literally)its the reason why some dac chips now offer an anti-clip feature. before this happened to me, I could not understand what the anti-clip was about (seemed silly) but now I get it. its one way to work within lower precision math and not have overflow errors when 'loudness war' style content (also 'internet radio') is played.I was one who found this somewhat early and we basically abandoned 2 chips due to this. in my own build, I decided to not have a local dac and, instead, just send out spdif (i2s->spdif chip) and let the next box worry about itbut anyway, this is something to be realized. if you plan to use a newer dac chip for audio, be aware and test for 'very loud music' (sigh) and see if you hear strange artifacts like clipping or flipping of the waveform. some dacs just force YOU to have to pre-attenuate in the digital domain so that you create your own anti-clip safe region for the low-quality dac.

author: JuKu
author_rank: Frequent Contributor
timestamp: September 07, 2015, 08:52:29 pm
content: Quote from: NiHaoMike on September 07, 2015, 07:21:36 amFor math errors, I'm not sure if this is even the worst case, just easiest to understand: Imagine a sine wave 1/6th of sampling frequency. First sample is 0, second is somewhere on the rising slope, third is somewhere on the falling slope, fourth is zero again, fifth and sixth mirror the second and third on the negative half. In degrees, first sample is at 0*, second at 60*, third at 120* and so on. Now, the peak of the reconstruction of this waveform is higher than any of the samples. If the samples are already at full scale, the DAC should be able to generate a signal 1.1dB over full scale. So, the DAC breaker signal is 0, Fs, Fs, 0, -Fs, -Fs, 0, Fs, Fs, 0, -Fs, -Fs ...Very few DACs can do this, unless they have a digital attenuator or other digital processing that safeguards for this (which has its own pitfalls). Some clip nicely, some behave catastrophically (mirror or worse).In real life, these kind of signals are results of naively done leveling that looks only the maximum sample value, sets that to full scale and scales all other samples accordingly. Audio engineers are not educated enough to leave a couple of dBs headroom when leveling, and I'm not aware of any leveler that calculates the reconstructed signal peak value.

author: JuKu
author_rank: Frequent Contributor
timestamp: September 07, 2015, 09:02:31 pm
content: Quote from: retrolefty on September 07, 2015, 01:06:27 pmI miswrote: I meant to say that double blind test only gives positive results, i.e. These samples sound different. A negative result means no difference detected, it does not mean there are no audible differences.Please refer from personal insults in future comments.

author: retrolefty
author_rank: Super Contributor
timestamp: September 07, 2015, 10:24:13 pm
content: Quote from: JuKu on September 07, 2015, 09:02:31 pmSir, I did not mean to insult you but rather question your understanding of a well designed double blind test and what the results can and cannot determine.The test is to see if a subject can tell the difference between two different sound sources. By double blind even the test administrator does not know which source is being sampled at each random test step A, B, or X. The test isn't designed to test if there is a absolute difference or not but rather that the subject can guess significantly better then random chance.The decision to buy a $6k CD player may be for valid reasons other then there being a sound difference, heck it might be gold plated and worth every penny. But it should not be because it's PROVEN to 'sound better' unless it can pass a double blind test. Human judgement is just too subjective to other influences and music enjoyment is or at least can be an emotional experience.If your point is that even two CD players of the same model/brand can never have exactly the same exact identical performance (component tolerances, etc) then you are missing the point. The test is not to test the equipment in question but rather the human being administrated the test. Engineers already know how to test the equipment already. An engineer may tell you one unit has .005% THD and the other .001% THD, but he/she cannot tell you if you will hear a difference.A double blind test is not your enemy nor am I in the question of what sounds better to someone unit A or unit B? There can be a scientifically designed test to answer that if one really wants to know the truth. Otherwise like I said it's just more like wine tasting then science.

author: JuKu
author_rank: Frequent Contributor
timestamp: September 08, 2015, 01:14:45 pm
content: Quote from: retrolefty on September 07, 2015, 10:24:13 pmI would claim I understand the test and its limitations better than an average sound engineer. Btw, a good test is not based on samples and especially, not random samples. The results are better when user can take his/her time and use familiar material. Of course, if you meant that at each step the X is random, of course. Nor does the test need to be ABX test. AB test (AA, BB, AB, BA at random) gives a result, too.QuoteThe ABX test doesn't say anything about what is better, it might well be that a non-accurate reproduction sounds better. Of course, the consensus (if in audio, there ever is any) is that closest to accurate reproduction is best. A $6k CD player is partly an emotional experience as well. Still, my point was that passing a double blind test or even many of those, only proves that there wan no reproduction flaw found in those particular tests. Part of the emotional experience is that a $6k CD player is likely done as well as the company possibly can, and is unlikely to fail in real life use, either physically or when the user listen nuances that maybe did not got attention in any tests.QuoteI said: "I have yet to measure two audio DACs fromdifferentmanufactures with identical results." In other words, different designs have rather different characteristics, and the differences are real and measurable, way beyond component tolerance variations.QuoteThe point: There is no test that will tell a positive truth, positive meaning there is no audible error in a device. In some way, there is always an emotional / wine tasting / trust and confidence / aspect in high-level audio, no matter how you word it.

author: Bassman59
author_rank: Super Contributor
timestamp: September 08, 2015, 05:03:04 pm
content: Quote from: NiHaoMike on September 07, 2015, 07:21:36 amFunny, I'm working on a studio monitor controller which includes USB DAC and ADC, and you've chosen the same parts I did for the DAC. (And the headphone amp.)

author: linux-works
author_rank: Super Contributor
timestamp: September 08, 2015, 05:06:03 pm
content: slightly OT, but since you mention it: I have a TPA6120 chip due in this week and a break-out board all ready for it. how do you (who have designs for that chip) plan to deal with (if, at all) the known dc offset issue of that chip? servo or just not care?

author: NiHaoMike
author_rank: Super Contributor
timestamp: September 09, 2015, 03:38:37 am
content: Quote from: Bassman59 on September 08, 2015, 05:03:04 pmThe Asus STX also uses PCM1792A and TPA6120A2, but uses other (socketed) opamps for the IV stage. The Fiio X5 uses PCM1792A and OPA1612, but uses BUF634U for the output drivers.The TPA6120A2 has a few mV of offset. While that might not seem like much, it's enough to make a very obvious click when the output relay engages or disengages. (That caught my friend and I by surprise since the datasheet never mentioned about it!) I used a LT1024 in an active offset correction circuit, bringing the offset to well below what my multimeter is capable of measuring and making the click virtually inaudible.