Digital Drive Upsamplers, DACs, jitter, shakes and analogue withdrawals, this is it.

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RE: CD tweaks

Posted by Thorsten (M) on June 17, 2015 at 09:13:23

In Reply to: RE: CD tweaks posted by genungo on June 17, 2015 at 06:17:37:

Hi,

> Which "CD Tweaks" have been measured so far?

Those tests were done over ten years ago, while developing CD-Players. What I tested were the following (memory) and they were tested with the CD playing in a reasonably silent room and with an acoustic signal, common Marantz "Audiophile Tuned" CD-Player:

Ceramic CD-Mat
CD-Flop (basically a 5.25 Floppy Disk cut to CD Size)
CD Tuning Stickers
Green Pen
CDR vs CD
CDRW vs CD
Demagging CD (no measurable result, non audible either)

All had been previously considered offering material changes duriing Audio Club Meetings in tests mostly semi-blind but some sighted (demagg listeing was sighted).

> Do they all produce a measurable impact on servo current

They do unless noted, precise result depended somewhat on the precise CD (excentricity, thickness, flatness etc) and the tweak. But generally two identical CD's one "au naturelle, the other tweaked, reliably measured different and showed recognisable (read correlated) patterns.

> and/or clock jitter performance?

The tools I had than were somewhat limited (AP2 and HP Digital Storage Scope) and I still lack gear that would give me better access to what is happening than I had than (plus, in 2015 I could not give aa flying french coitus about CD), but using enough averages on the AP2 J-Test from CD and a suitable acoustic signal exciting the CD (takes more ime to run the test than to manually grind the coffee in a handcranked mill and traditionally made a decent cup of filter coffee) showed reliable corellation (unsurprisingly, we are dealing with physics here).

Others were much harder to link, but the logical chain of "many CD-Tweaks reliably modulate servo current" and "modulated Servo Current can be reliably shown to exist as correlated clock jiitter in the analogue output from the CD-Player" passes occams razor as does concluding that hence CD-Tweaks can change the jitter pattern of the analogue output and people have been convicted of murder in courts by a jury on less.

Do I have a smoking gun, Photo of defendent firing said gun, photo (full frame) of bullet from defendents gun hitting the victim? No I do not.

Using measurements and blind listening tests again correlated measurable changes with audible ones. Paradoxically, subjective preference was not always for lowest jitter/least servo modulation, but easily measurable differences generally made it past the listening test noisefloor.

I think there are in principle a few dissertations in this, but as said, CD is SO 1980's, just as the Mullet Haircut and Duran Duran, so who cares?

Thor

At 20 bits, you are on the verge of dynamic range covering fly-farts-at-20-feet to intolerable pain. Really, what more could we need?

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