percy said:
Hi.
To give an easy example :-
Any capacitor acts as a microphone to a certain extent (hence 'capacitor microphones').
Therefore any vibration will cause the capacitors to introduce 'noise' into any circuit to which they are attached.
Reduce the induced vibration - reduce the induced noise - QED.
Andy
Capacitor microphones are designed specifically so that one plate acts as a very thin diaphragm, while the other plate is fixed. Then, air pressure changes can change the distance between plates, and hence, the capacitance, voltage, etc.
That said, capacitors used for audio applications are not "designed" to do this, and I can't imagine that typical vibrations will change the capacitance by any significant amount (i.e. enough to hear). If someone has tried inducing vibrations to measure this effect, by all means, let me hear it. But, I really doubt that anyone can offer anything more than hand waiving arguments based on something they read in Stereophile or some other audiophile pub.
Something that potentially could cause problems are vibrations that effect the crystal timing.
That said, capacitors used for audio applications are not "designed" to do this, and I can't imagine that typical vibrations will change the capacitance by any significant amount (i.e. enough to hear). If someone has tried inducing vibrations to measure this effect, by all means, let me hear it. But, I really doubt that anyone can offer anything more than hand waiving arguments based on something they read in Stereophile or some other audiophile pub.
Something that potentially could cause problems are vibrations that effect the crystal timing.
Re: Re: How do vibrations in a CD player/transport cause jitter ?
I realize that noise in the clock's signal and power lines can be held accountable for jitter, but are you saying that the mechanical vibrations from the drive are strong enough to create microphonics from capacitors ? which in turn are strong enough to pollute the clock lines ??
poynton said:
I realize that noise in the clock's signal and power lines can be held accountable for jitter, but are you saying that the mechanical vibrations from the drive are strong enough to create microphonics from capacitors ? which in turn are strong enough to pollute the clock lines ??
ezkcdude said:
I only gave the capacitor as an example since capacitor microphones exist. Yes, I know that they are not built to the same design as audio caps but they exist and therefore it is a fact that vibrations in caps can induce spurious voltages however small. When you discharge a flashgun cap., a noise is produced (try it) and the reverse is obviously so. Enough of caps. , it was an example ! Try Tubes / valves - also microphonic. Try flexing a phono-preamp pcb - you get a noise.
Many more examples exist - whether they increase jitter, I do not know but they can introduce noise.
Andy
Vibration modulates the *shared* power supply through the servo circuitry. If the disc moves, the laser has to track it. Motors draw current, etc.
I can tell you that the best transport I have heard was a relatively old and cheap CD player where someone had given a lot of attention to this. There was no part of the original chassis remaining. The transport mechanism was on a sprung platform. Worth doing.
I can tell you that the best transport I have heard was a relatively old and cheap CD player where someone had given a lot of attention to this. There was no part of the original chassis remaining. The transport mechanism was on a sprung platform. Worth doing.
I think that it's mostly for the disc, if there are less vibrations, it has less tracking, focusing, etc. job to do, and less chances to skip.
Maybe the clock would be affected, but if a shock could change it's output, then an high-pass filter could remove it.
Also, I think that a lot of them are made by persons that want to make $$$, usually accompanied with a looong fake theory seeming a bit plausible. See : CD Demagnetizer, right next in the products page to $60 plugs, green CD markers, CD flashers, $125 system enhancer CDs and $10k/foot speaker cables, or the Clever Little Clock.
http://www.gcaudio.com/cgi-bin/store/showProduct.cgi?id=190
http://www.machinadynamica.com/machina41.htm
Maybe the clock would be affected, but if a shock could change it's output, then an high-pass filter could remove it.
Also, I think that a lot of them are made by persons that want to make $$$, usually accompanied with a looong fake theory seeming a bit plausible. See : CD Demagnetizer, right next in the products page to $60 plugs, green CD markers, CD flashers, $125 system enhancer CDs and $10k/foot speaker cables, or the Clever Little Clock.
http://www.gcaudio.com/cgi-bin/store/showProduct.cgi?id=190
http://www.machinadynamica.com/machina41.htm
this is probably an interesting arcticle
http://www.6moons.com/industryfeatures/lurne/lurne.html
IMO our knowledge (at least mine) is insufficient to understand all effects within digital audio translation to music that effects its quality. There are a lot of partial theories, with various kinds of measurement/statistical backup. It comes down to 'what you want to believe'.
Henk
http://www.6moons.com/industryfeatures/lurne/lurne.html
IMO our knowledge (at least mine) is insufficient to understand all effects within digital audio translation to music that effects its quality. There are a lot of partial theories, with various kinds of measurement/statistical backup. It comes down to 'what you want to believe'.
Henk
so basically a cheap flimsy transport will not really corrupt the data, it will still send the correct 1's and 0's, but it just messes up the clock with jitter because of the vibration it produces. Right ?
As quoted from the article -
"..we built a large prototype to conduct lengthy measurements that would help us understand the mechanical and optical phenomena associated with such a device."
I'd be interested in knowing what were the results of these lengthy measurements ? Does a typical consumer level cd player transport corrupt the original "data" from the disk in any way or does it get retreived verbatim - stritcly speaking in terms of completeness of the data for now, and not including other problems associated with vibrations and jitters.
I'd imagine then a pc based music system would certainly be at an advantage in this respect(?) i.e. files ripped to an uncompressed/lossless format are played from the harddisk via USB or Firewire DAC.
As quoted from the article -
"..we built a large prototype to conduct lengthy measurements that would help us understand the mechanical and optical phenomena associated with such a device."
I'd be interested in knowing what were the results of these lengthy measurements ? Does a typical consumer level cd player transport corrupt the original "data" from the disk in any way or does it get retreived verbatim - stritcly speaking in terms of completeness of the data for now, and not including other problems associated with vibrations and jitters.
I'd imagine then a pc based music system would certainly be at an advantage in this respect(?) i.e. files ripped to an uncompressed/lossless format are played from the harddisk via USB or Firewire DAC.
percy said:
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Vibration damping aims to minimise microphony, which may or may not cause serious time shifts (jitter) in the signal. So many posters seem to blame everthing on jitter that it is difficult to debate the subject. Impedance mismatches and other factors can be just as important and should not be 'lumped' into one thing called jitter. Worse still, the computer guys use 'jitter' with a different menaing altogether; jkust like they call software 'engines'
percy said:
Hi.
Re-reading Percy's original question and his subsequent comment.
Percy,
What do you mean by 'jitter'?
A cheap, flimsy transport WILL corrupt the data more easily than a better built one which explains the popularity of the early Philips swing-arm CDM-0 , CDM-1.
Several factors come into play before the data reaches the dac.
The laser must remain in focus
The laser must track the disk
The disk must rotate at a constant angular velocity
The HF signal should be as noise free as possible
A good quality transport and servo system ensures the first three, good design should ensure the last. ( do a google for 'Kenwood DP-100SG' to see anti vibration measures - mainly in Japanese)
Vibration will and does affect the first 3.
The early cd-players, eg Philips CD100, CD104, had an error light. Place one of these players on top of a speaker and watch it light up! An overkill example but valid. They removed the led on later models as people complained!!
Chassis damping etc reduces the effect of vibration on the laser system and so reduces the errors.
Andy
I don't think the hardware isolation is for jitter control exactly.
I agree with the previous post that mentioned that vibration damping is for LASER tracking reliability... The whole microphonic influence, though it may have some merit in some other discussions, seems to miss the mark here.
I've seen this in nearly every drive I've examined ( don't assume that's really very many). Assuming that it's there to keep drive influences away from the nearby electronics IE; Jitter control, seems quite backwards.
Why would a Manufacturer want to isolate the the drive and laser portion of the unit? The laser head guide has a very small focusing coil mechanism that has a finite adjustment range in which it can compensate for track alignment variations on the disk. If the tray is rigidly attached to the CD player case, any extraneous bumping would affect the mass of the moving laser head and cause it to possibly fall off track and interrupt the audio stream.
Think of what happens when CAR CD player is playing and you drive over a Speed Hump at 20 MPH. Laser Head moves beyond normal extremes due to the G forces exerted by hitting the bump and you get an interruption.
Can someone post some scope shots of what happens when they tap their crystals with a hammer or just place some form of a vibrator against the circuit board to document vibrational influences on a clock source?
I agree with the previous post that mentioned that vibration damping is for LASER tracking reliability... The whole microphonic influence, though it may have some merit in some other discussions, seems to miss the mark here.
I've seen this in nearly every drive I've examined ( don't assume that's really very many). Assuming that it's there to keep drive influences away from the nearby electronics IE; Jitter control, seems quite backwards.
Why would a Manufacturer want to isolate the the drive and laser portion of the unit? The laser head guide has a very small focusing coil mechanism that has a finite adjustment range in which it can compensate for track alignment variations on the disk. If the tray is rigidly attached to the CD player case, any extraneous bumping would affect the mass of the moving laser head and cause it to possibly fall off track and interrupt the audio stream.
Think of what happens when CAR CD player is playing and you drive over a Speed Hump at 20 MPH. Laser Head moves beyond normal extremes due to the G forces exerted by hitting the bump and you get an interruption.
Can someone post some scope shots of what happens when they tap their crystals with a hammer or just place some form of a vibrator against the circuit board to document vibrational influences on a clock source?
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