Computer Audio Asylum

Music servers and other computer based digital audio technologies.

Use this form to submit comments directly to the Asylum moderators for this forum. We're particularly interested in truly outstanding posts that might be added to our FAQs.
You may also use this form to provide feedback or to call attention to messages that may be in violation of our content rules.

You must login to use this feature.

Inmate Login

By default, logging in will set a session cookie that disappears when you close your browser. Clicking on the 'Remember my Moniker & Password' below will cause a permanent 'Login Cookie' to be set.

Moniker/Username: The Name that you picked or by default, your email. Forgot Moniker?	Examples "Rapper", "Bob W", "joe@aol.com".
Password:	Forgot Password?
	Remember my Moniker & Password ( What's this?)

If you don't have an Asylum Account, you can create one by clicking Here.

Our privacy policy can be reviewed by clicking Here.

Inmate Comments

From:
Your Email:
Subject:

Message Comments

Original Message

RE: The beans have been spilled!

Posted by Tony Lauck on April 29, 2012 at 17:15:52:
Link to image was busted...
Your friend is right. With most, if not all, DACs the differences from moment to moment are likely to be much greater than the difference between A and B. However, over a period of time these differences average out and it would certainly be possible for analog measurement apparatus to detect the differences by using sophisticated averaging techniques. What's rather more amazing is that some audiophiles can do this by ear.
If you do null tests in the analog domain you will get different results each time because the digitization of the analog output happens with a separate clock. The relative phase of the the two clocks constantly changes, invalidating the null tests. It may be possible to slave the two clocks, but jitter noise will still be different.
With ladder DACs the waveform output by a DAC will not vary from play to play, except for noise, voltage and temperature changes. With a delta-sigma DAC there is a new source of randomness, the state of the delta-sigma modulator, which is a pseudo-random number generator. If the modulator is given the same set of input bits on two separate occasions it will not produce the same set of output bits to convert to analog. That's because the modulator is a digital feedback circuit which retains a history of it's previous activity. This is easily shown to be the case if one experiments with these modulators with software. One gets a completely different pattern of output noise when feeding them two constant input signals that differ by one in the least significant bit. The ability to hear these differences (especially in the DC case) must be taken as a fault in the DAC, not a "resolving" feature.