the definative cd lathe test

Rob i think it really is this simple.

Below a certain level of separation between the power supplies in the cd player, for the various parts of the transport-optics-servo etc, then it can make a difference. Ie less servo tracking = less noise on the PS rails = quieter supply elsewhere.

If you have a decent player with individually regged supplies for the servo etc, then it makes bugger all difference.

But I've blind AB'd this too many time to give a shit what the results say, I can pick out certain discs every single time on my cd player. You are welcome to come round and test me if you'd like.

The Nespa on the other hand, i believe is utter bollocks.

 

I can sort of buy the argument about the servo/psu.
However that would also imply that some discs (perfectly flat and concentric) will show no benefit while others should show some variance from track to track.
I find it difficult to believe that the servo/psu effect is constant during play - there must be periods where the servo is working harder so the effect of lathing shouldn't be audible at certain times. Yet lathers claim universal benefit.

Simply doesn't compute to me.

You certainly shouldn't be hearing this tomfoolery on that excellent 840C!

 

I'm not interested in what the irrational and unwashed claim for it.

On some discs on my cd player I can pick them out every time and at any point during the disc.

On others I can't.

I'm presuming, it's not data content related, which only leaves a physical effect. And the only one that makes sense is where the edge of the disc isn't perfectly concentric with the centr,e and this 'off balance' causes oscillations/precession in sled and the optics which make the servos work harder to track the disc.

The 840 is a great player, my heavily modded version even more so. However it does only have one power supply feed to the transport and shares the transformer for everything in the player. I think that is it's downfall in this instance. I wouldn't be at all surprised to find that adding another traffo for the servo board and transport utterly removed the cd lathe effect.

Its a better DAC than cd player, which could seem to indicate their is PS interaction.

 

Yet lathers claim universal benefit.


Like Ian, I claim it only for my own kit.

 

Sorry, I meant on all discs - not all systems.

I'm still not convinced by any of the arguments.
The Meridian 206 is old (1980s) never serviced and uses a shared PSU. It is certainly less advanced in the PSU department than many even quite inexpensive machines available today.
Yet it gives bit perfect replay and a perfect null on two discs.

Running the test again but deliberately making one of the discs quite unbalanced (by warping etc) might be useful but someone else can try that if they still aren't convinced.

 

I'm up for monitoring/graphing servo currents while we spin lathed/non-lathed discs, if anyone really wants to go that far.

I think it's a plausible mechanism - eccentricity would be a constant load variation that would show-up as LF noise, disc-speed-locked & diminishing in frequency with play across the disc. LF noise is the very hardest to filter, and also possibly the most significant PSU-modulation component to audible jitter. A putative mechanism where a single raw PSU is shared, perhaps.





I would much rather simply listen to music for pleasure tho!

 

Is there total confidence that AB lathe tests have always been done with copies of the same disc? I think you need to confirm that rips match before doing any listening. Rip before and after lathing to be sure.

I think you also have to eliminate the possibility that the digital output can be the same from two discs, but the analogue not.

Paul

 

The AB in this case was with a pair of originals.

I've dug as far as I think necessary but would like to see others (perhaps on the pro lathing side) do some digging to support their ideas.

 

i'd be willing to drive miles with lathed discs and my cd player for testing, both of ability to differentiate the discs and have my player measured.

i'm reasonably confident with both outcomes.

 

What digging?!

In most cases lathing has had a benefitial effect upon my discs, though I'm not sure I'd have said it was night and day in all cases.

I think it fair to say in some cases the improvements were greater than others.

 

Hi Rob

Do you have a DVD player in the house?

Just wondered, it would be another cd player to try. Just a thought... or maybr sq1212123 could drive over ?

 

This test appears meaningless

Okay, I've waited for someone else to mention this. If one disc contains a double album, the other only 1 disc, then that means the 2 discs aren't identical. It would appear they are 2 different versions - one is possibly a digital remaster, for example. So anyone still surprised they sound different?
I'm sure this was a genuine mistake, but to me this makes the test completely invalid. Next time it would be good to get 2 discs that are the same version to start with.
Cheers,
Mort

 

As Sq says, if people want to investigate the effect of lathed and non lathed discs on power supply lines in order to support an argument, I hope they do and would encourage it.

I'm not convinced at the moment by my ears or the measurements that any positive effect exists from lathing and so will kick this into touch until someone can show me something that reignites the interest.
-

 

Mort I think you misread it.
One sleeve had a disk missing - it wasn't a different version.
And both discs null on the same CD player, which in my book makes them the same.

 

In fact, I have just thought of a method to prove the existence of an audible effect:
1. Take both discs (before lathing), and rip the data off both, comparing this raw data will show that both discs start out identical.
2. Perform the comparison test from the digital output of the transport, again the "difference" file should be a flat line.
3. Lathe one disc
4. Repeat steps 1 and 2 above. The raw data should still be identical, but now you should have a difference when ripped through the digital output of the transport. Or not.

QED
Cheers,
Mort

 

Aah, thanks for pointing that out, English isn't my first language, being from up north, I'll get me coat. I thought maybe there was more than one set of discs doing the rounds, to explain the different results.
Cheers,
Mort

 

I do Chris but I've now returned the discs to Pete.

I think sq is in Sheffield so a bit of a trek.

 

Actually, I don't doubt this, and wouldn't seek to undermine it. I've made similar calls on things like Vreg compensation, happenings *way* above the audioband, that I have little / no justification for on paper (or scope) much beyond intimate day-to-day familiarity. There is stll a point at which we choose to (or simply have to) trust our own ears




(not least because building a much better instrument diff. amp will be expensive, and a great hassle!)

 

Originals need not be identical. In this case clearly they are, but what about SQ1414?

I really think it would be surprising if the digital output of the player changed following lathing, what you need to look at is the analogue output.

Whey I say 'you' I mean someone who both believes it works and wants to understand why. So I presume in practice, no one.

Paul

 

Easy enough to attempt a null using the analogue outputs if someone wishes to try.

Thinking around this some more, if 'originals' can and do vary, then it is quite possible for a standard disc to be better than the lathed version.

Has anyone actually looked at the manufacturing quality of CDs?
I'm assuming that they aren't all concentric, but if they are and standards are already high enough......

Also, seeing if any audible lathing effect vanishes when using an external DAC (entirely separate power supplies) would be another idea.