[Sasha]

Maybe, at this point, someone could provide a laymen's explanation of "jitter".  If I look at Wikipedia it speaks to several kinds of jitter and after several readings I confess to a migraine coming on.  What I can glean is that jitter affects the spectral density, i.e., frequency content of a signal.  I guess the fundamental question here is how does downloadable music using a high quality DAC(Bryston) compare to that from a CD player(Bryston).  It's beginning to sound like CD has the advantage.

Unless the downloadable music is a least equal to a CD it would seem we have now undone what we have have spent $xx,xxx.xx on our systems to achieve.  Many times I have music playing in the background but I don't use my Bryston set-up to do so.  If I want background music I use one of my restored Marantz receivers which provide a very pleasant sound through my Paradigms, but it is not of a quality that I would accept for critical listening.

It may be, as someone noted, that a PC source has the potential to meet or exceed a CD source, with potential being the operative word. This implies that the equality does not exist at present.  At this point it doesn't seem like spending several thousands of $$$'s to provide a sub CD standard of sound makes much sense.  I guess the one up side here is that I could have access to a very large bank of music at a cost far less than what it would cost via CD's.  The down side being it just doesn't sound as good.

So....how far off base am I on this whole thing....or am I?

You are exactly on the point. PC has potential, and you could realize that potential but only as an engineer set to design and execute PC components with specific objectives in mind.
I have no time, money, will and knowledge to do so and I do not think those who claim equal performance had opportunity to hear side by side in the same system the significant differences in performance between top optical player and whatever PC rig they came up with.
I did comparison using Wadia 581iSE player with digital I/O board in my system, so the only variable was tray versa digital signal on Wadia?s digital input. No differences in analog sections of different DACs or anything of that sort.
PC was purposely build, all non-essential HW disabled, lowest OS footprint, Lynx with arguably lowest jitter, completely fanless goes without saying, did not even do ripping on it but on another system just so that I would minimize power consumption, EMI and RFI.
It would require an effort of an engineering group to get PC to output low jitter, for example same effort that Bryston put into design of BCD-1 or BDA-1, that effort is visible in excellent measurements and is very audible.
Now, this does not say that you will hear significant difference in your system between BCD-1 and whatever PC source you came up with. It is for you to hear and decide.

[Sasha]

Dear All,

I am wondering whether you have come across the Linn DS range of sources. I personally run a Majik DS (looking to go for Akurate asap) directly into my 4Bsstsq (it has a digital volume control on board)

The Linn DS products are a hybrid type where you essentially stream packets of information via an ethernet that is easy to set up at home via cat 5/6. You can use a NAS or simply use your pc as the media server. The DS then has a DAC on board for output as phono (unbalanced or balanced as you go up the range). I am not technical enough to understand the advantages of this technology over using USB directly to a DAC. I think one of the advantages might lie in the buffering that the DS does with the PC/NAS. Either way, I have been very pleased with the results.
I have got around the re-wiring situation by using ethernet via mains plugs that incidentally to not degrade the signal quality (to my or anyone on the Linn forums ears)

Anyway - control of all my albums is remotely via my ipod touch with some software that accesses the ethernet remotely via a wireless access point.

Worth considering as an alternative.

Cheers

I would absolutely love to try Linn DS, at least on paper it is the solution, it is only a question of execution.
It is fundamentally what Squeezebox/Transporter is, but those are horribly executed components with very poor performance (had that as well).
If Linn did good engineering job as Bryston did with BCD-1/BDA-1, it would be sort of the ultimate PC source with performance that I have been trying to get out of what was essentially tweaked PC built from readily available components.
I hope to try it eventually.

[Sasha]

Hi,

IIf you want music in every room for ease of play and quality is NOT the priority the digital stored music is he way forward, Quality is Good, often excellent but NOT "high end"

Andy.

I disagree.  Music ripped with error correction fed to a good DAC has the potential to be equal or better than the best spinners.

Steve

Ripping is not an issue, jitter is.
There is no computer based transport that can come close to best optical players, let alone best them.
This is my personal experience and experience of many others who did compare at length best optical players to best purposely built PC transport, paying attention to every conceivable detail in effort to minimize jitter out of PC into an external DAC.
No match, period. PC is inherently inferior in many aspects, it would have to be re-engineered significantly to be able to compete, from its noisy PSU, to noisy mobo and bus.

Hi Sasha,

When doing these comparisons what did people think the differences were.  In other words how did the extra jitter (assuming we can assign that as the fault) manifest itself sonically?

James,
I had 3 pairs of ears over at my place at the time the comparison rig was set up, one also had experience in the related industry and knew how to evaluate components and performance, not just some random listening to unfamiliar tunes of questionable quality.
Keep in mind I spared no money to build PC.
There was agreement on differences among us.
The most glaring difference was in low end, clearly audible, same tune from tray had significantly more definition, you could clearly hear notes of any instrument in that range, precise pitch, good timing.
Same tune ripped and played from PC into the digital input on the same player had undefined low end (not like some terrible room modes, but lack of definition, you could not hear such clearly defined notes).
There was not such obvious difference in higher frequencies. Voices did sound somewhat hard and glary from PC. On some simple tunes that had nothing in low end, just a few instruments, you could not hear any difference.
To prove the point, I burned CD from the ripped files and played that CD in tray again, to make sure that ripping process was correct. Again tray was better.

[James Tanner]

Hi Sasha,

OK thanks - I think putting a sonic character on it makes it much easier for people to understand.

As far as you know is there a jitter figure that most experts agree is below threshold? In other words, tests done to see at what level jitter becomes audible?

I have run my own tests with unsuspecting listeners as well and it is an interesting subject to say the least.

james

[Charles Calkins]

Never met jitter. Don't know who he is or what he looks like. I have to agree with Sasha about PC music versus CD play music. To me PC music seems to have a sharp edge to it. CD play is overall much smoother to my ears.

 But what the hey!!!! PC music is like having a great big Juke Box. I like that!!

                                       Cheers
                                       Charlie

[Sasha]

Hi Sasha,

OK thanks - I think putting a sonic character on it makes it much easier for people to understand.

As far as you know is there a jitter figure that most experts agree is below threshold? In other words, tests done to see at what level jitter becomes audible?

I have run my own tests with unsuspecting listeners as well and it is an interesting subject to say the least.

james

James,

I have no slightest clue what the audible threshold for jitter is.
Keep in mind it does not always manifests itself the same way.
Case and point, I had the same sound card in two different PCs, one that was purposely built for the function and one that was sort of universal, although configuration was correct, for example I made sure I was using ASIO, had proper buffer size, etc.
Essentially the difference was that in other PC I had low rpm fans spinning, more HW components enabled (e.g. USB, NIC, etc.), larger OS footprint.
The difference between two PC transports was absolutely enormous, with the one that was not purposely built not only that I had no definition in low end but throughout the entire spectra, the sound was very diffused, imagining was not precise, kind of warmish, soft sound that some people actually like!
In regard to tests with unsuspected listeners, I do not think it is good way to subjectively measure anything, it can take you either way, listener must be familiar with the tune, it has to be good quality tune played on quality system, and listener must have the brain wired to recognize good from bad.
What is the point to ask for someone?s opinion of a sound quality if person has never or only on a rare occasion heard the sound of live unamplified instruments or singing voices?
Such person has no reference to pass the judgment, only like or dislike preferences.
Are you going to ask for opinion someone who uses iPod or is convinced VBR MP3 is as good as 44.1?

[James Tanner]

Hi Sasha,

Most of the listeners I associate with are crazed audiophiles like myself so they do have a good background in audio. Some are recording engineers so they do have a good feel for live sound.

I guess I have found over the years that I prefer to do 'blind' tests (even on myself) because 'expectations' can really shift the results is the 'expected' direction.

I also tend to do my tests with one person only as I find group sessions can affect opinions of others depending on who the perceived dominant audiophile is.

james

[srb]

Case and point, I had the same sound card in two different PCs, one that was purposely built for the function and one that was sort of universal, although configuration was correct, for example I made sure I was using ASIO, had proper buffer size, etc.
Essentially the difference was that in other PC I had low rpm fans spinning, more HW components enabled (e.g. USB, NIC, etc.), larger OS footprint.
The difference between two PC transports was absolutely enormous, with the one that was not purposely built not only that I had no definition in low end but throughout the entire spectra, the sound was very diffused, imagining was not precise, kind of warmish, soft sound that some people actually like!

No matter how meticulous your dedicated PC build is and no matter how many components and running computer processes you eliminate, without reclocking and buffering the stream into memory with something like the Empirical Audio Pace Car, you won't be addressing jitter reduction.
 
I don't have personal listening experience, but others who have posted on their results of listening tests (like you) using the Pace Car and a superior DAC, have said that it not only sounds as good as the modded high end players, but even the stratospheric players like dCS, Meitner, etc.
 
That is why I used the word potential.
 
Steve

[Sasha]

Case and point, I had the same sound card in two different PCs, one that was purposely built for the function and one that was sort of universal, although configuration was correct, for example I made sure I was using ASIO, had proper buffer size, etc.
Essentially the difference was that in other PC I had low rpm fans spinning, more HW components enabled (e.g. USB, NIC, etc.), larger OS footprint.
The difference between two PC transports was absolutely enormous, with the one that was not purposely built not only that I had no definition in low end but throughout the entire spectra, the sound was very diffused, imagining was not precise, kind of warmish, soft sound that some people actually like!

No matter how meticulous your dedicated PC build is and no matter how many components and running computer processes you eliminate, without reclocking and buffering the stream into memory with something like the Empirical Audio Pace Car, you won't be addressing jitter reduction.
 
I don't have personal listening experience, but others who have posted on their results of listening tests (like you) using the Pace Car and a superior DAC, have said that it not only sounds as good as the modded high end players, but even the stratospheric players like dCS, Meitner, etc.
 
That is why I used the word potential.
 
Steve

Pace Car is also on my one day to try list.
Wish I could borrow it somewhere before commiting to purchase.

[Stu Pitt]

Speaking of jitter...

I gets discussed ad nauseum.  Everyone has a different opinion as to how to address it, how much is audible, which devices have more and less, which connections have more and less, and so on and so on and so on.  Its discussion and disagreements are only surpassed by cable discussions.

Of all the heated jitter debates and discussions, I've never heard anyone describe the sound of jitter.

So I ask all the various people with highly varied opinion of everything jitter related...

What does jitter sound like?

[James Tanner]

From the BDA-1 Literature:

JITTER REDUCTION

Jitter is a mistiming of data being moved from point A to point B in any synchronous digital system. Think of jitter as individual ticks on a clock --however each tick is not occurring at exact one-second intervals. Some are slightly less than a second and some are slightly longer, and they average out so that no actual time is being gained or lost over a large number of seconds. Jitter is the difference between the shortest and the longest second, and in digital audio systems this specification is usually measured in nanoseconds.

Both the frequency and the jitter characteristics of the system's digital clock will affect the accuracy of reproduction. The frequency, if not accurate, can cause the pitch and speed of the music to change, and in some systems cause drop-outs if there is no data available.

james

[srb]

It sounds like bad juju!
 
Sasha has described it as a loss of definition, particularly at bass frequencies.
 
Steve Nugent at Empirical Audio has described it as a film on a clear window.
 
Whatever it sounds like, most chip and component manufacturers are trying their darndest to reduce it as much as they can.
 
In a way, I am tired of hearing about it too, but I'm not going to lump it in with cable talk.  It is a mis-timing of the digital signal and I don't doubt it can result in a "smearing" of that isgnal.
 
Most audio people will agree that the analog format of LPs sounds better.  I myself have done comparisons with the same album on LP vs CD.  And I totally agree that the LP had more fidelity and was truer to the original sound - just sounded better.  But I ditched LPs in favor of CDs because the total "experience"  for me was better - lack of groove and surface noise, lack of pops and clicks, lack of wear through repeated plays and lack of cleaning and maintenance.
 
Now, digital music on hard drives or solid state drives with the proper software is giving me the added pleasure of playlists, random play and even greater ease of use.
 
So I don't know exactly how much jitter contributes to the digital medium's loss of sound quality, but if I can duplicate some DIY guys efforts to tap into the I2S output of a few recommended sound cards out there (my DAC is one of a few that actually has an I2S input on it), I'll report back on how it has affected the sound, since the only thing I would be accomplishing is jitter reduction.
 
The Pace Car and it's options are beyond my budget for now, and even then I would have to try before buy.

[Phil A]

What does jitter sound like?

I have a older (14-15 yr. old) MicroMega DuoPro DAC.  Still sounds really good.  I think it listed for $2.5k in its day.  I traded stuff that was perhaps worth a bit less than $200 for it perhaps about 7-8 yrs. back.  It sounds very similar sonically to the BCD-1 (I compared before I bought the BCD-1).  I currently have it in the basement system which does not get used tons.  When I compared the two, I noticed the bass was a bit sloppier in the DAC but also there appeared to be some smearing of the (mostly the) bass due to timing differences that could be heard on certain recordings.  I don't hear much of those problems when I listen to it (the DAC) in the basement system (B&W P6s that probably start dropping off just below 40HZ) but could easily pick them out in the main system (I had Thiel 7.2s then with 2 Rel subs - have 3.7s now).  I also did not hear those problems with the DAC when I had it in the bedroom system (Thiel SCS2s which probably drop off around the same point as the B&Ws).

[Stu Pitt]

Both the frequency and the jitter characteristics of the system's digital clock will affect the accuracy of reproduction. The frequency, if not accurate, can cause the pitch and speed of the music to change, and in some systems cause drop-outs if there is no data available.

james

James,

Are you saying that it basically sounds like Wow & Flutter, only on a much less degree?

I'm assuming you have some device that intentionally introduces jitter for development and testing.  Have you intentionally introduced jitter into music (not test tones) and listened to its effects vs the same music without it?  What were the results?  Was music more blurry (what I'm equating to smearing), harsh, edgy, etc?

When I compared the two, I noticed the bass was a bit sloppier in the DAC but also there appeared to be some smearing of the (mostly the) bass due to timing differences that could be heard on certain recordings.

Phil,

How can you tell the smearing was due to jitter and not due to something/anything else in the DAC?


For the record, I'm not questioning anyone's findings.  I'm not trying to prove someone wrong or anything like that.  I'm just trying to make sense of it all and come out with some knowledge.  This is honestly the first time I've ever heard anyone attempt to describe what jitter actually sounds like in music.   

[Phil A]

I guess I can't say for certain (w/o measurement equipment) but the problem was consistent and I noticed it before I compared the BCD-1 to it.  I've had a lot of players in the system over a period of time - about 3.5 years back I had a Modwright XA-777ES.  I basically sold it with the decline of SACD along with my Sony TA-P9000ES preamp I used to switch between multi-channel SACD and DVD-A while I could get something for them.  I had a Proceed PMDT as a transport with the DAC at one point (I've probably had at least a dozen and a half different transports hooked to it - right now in the main system I have a LD player, a DVD recorder, two universal players and the BCD-1 - in the basement where I have the DAC at the moment I have a CD recorder, an SACD changer, a LD player and a PS3).  On some things you just notice a timing thing with the bass notes.  Almost sounds like the recording is in phase except for the low bass.  It's not something that would be obvious to most people listening to it for a short period of time.  With various players in the system over a period, including what I owned and borrowed it was something.  As I noted it was very similar sonically to the BCD-1 and it is something that is noticed more easily with a direct comparison between the units.