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Digital Drive Upsamplers, DACs, jitter, shakes and analogue withdrawals, this is it. |
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Digital Drive Upsamplers, DACs, jitter, shakes and analogue withdrawals, this is it. |
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In Reply to: Got Jitter? posted by jaydacus on April 2, 2017 at 01:08:06:
Hi
Interesting post!
I have some possible explanations to some of your observations plus have added my own experience..
"-I noticed when I started burning CD-Rs.....The copy just sounded "blurry" especially during a long listening session.
It depends on the write speed used relative to the capability of the media and the writer. Basically you are hearing the effect of read-induced jitter due to imprecise pit "edge" creation. The CD-R organic dye layer has to be perfectly uniform relative to the test area where the laser power is calibrated. The faster the write speed rating, the thinner the layer, but also the higher the "optimum" speed for a write with minimum jitter. "Lowest" speed is not necessarily appropriate for all media. The slew rate of the laser is also a factor (i.e the time taken for the critical temperature of the dye to be reached before the laser has shifted physical position.
With care, CD-Rs can often sound "better" than the original! Rather than doing a direct "on the fly" copy from one disc to another, a better way is to rip the image to memory first then write the image as this will eliminate read-induced jitter and you can then do re-reads and more extensive error-correction.
"-I had an Onkyo CD player that always sounded amazing during the last 25% of the CD. The first 75% sounded good in short bursts, but seemed harsh with an invisible layer of static during long listening sessions."
Again, probably read-induced jitter. The "last portion" of the disc is on the outer edge and the angular speed of the disc has decreased. In theory you might actually get worse performance due to edge wobble and therefore stressing the position and focus servos more. So if you are getting better performance in this region, it suggests that something is not ideal in the transport itself.
"-Most USB DACs no matter how well built probably have huge amounts of jitter. At least synchronous dacs for sure."
A bit of a generalisation! It depends on the DAC design. A synchronous design just requires more effort in the buffering and re-clocking stage. Asynchronous designs rely on the interface IC more, but the data still requires re-clocking for best performance. The problem is that many DACs incorporating Upsampling tend to take the easy way out and simply rely on the Upsampling process to de-correlate the input jitter rather than ensuring that the input data to the upsampling IC has already been buffered and re-clocked.
"-Jitter is not very noticeable in the lower frequencies"
I would agree that the effect of jitter is masked depending on the music and as such, much pop music which is bass heavy tends to not be so discriminating of the playback equipment...
In fact, I find that a very low jitter DAC system has much better bass definition and depth. As in "noticeably deeper" and you can still discern the note/pitch clearly.
I find the soundstage becomes more palpable and the timbre of the instruments/voices becomes more realistic. Due to the effect on the soundstage depth and width, I don't find it necessarily "more detailed", just that everything is in its place with the correct scale and realism. This is noticeable even with Redbook which in my system takes on many of the qualities of High Resolution to the point where I don't bother worrying about the source resolution anymore and I can just enjoy the music.
In equipment reviews I've read where the component being reviewed had very high levels of jitter (of the order of nanoseconds), the comments usually referred to a very "warm" sound with a general lack of definition.
I use a Grimm CC1 reference master clock (primarily for my recordings) but also for reclocking the data to my DAC.
I don't know if a better Master Clock exists these days, but certainly when it was released, it was without peer in terms of jitter level of the output data and made many of the reclockers of the time (such as Monarchy DIPs) to be "merely toys". Not knocking those products - I'm talking about relative performance! I would say that "today" the reclockers available probably get very close to the Grimm CC1 at a fraction of the cost. A very close performer is the Apogee Big Ben which uses DDS to generate clock signals and can convert between different interfaces eg AES to optical etc with fully reclocked data.
Regards Anthony
"Beauty is Truth, Truth Beauty.." Keats
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Follow Ups
- RE: Got Jitter? - flood2 18:13:25 05/28/17 (0)
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