Audio Asylum Thread Printer

Get a view of an entire thread on one page

Digital Drive

RE: Slew rate.

72.86.132.8

In Reply to: RE: Slew rate. posted by rick_m on June 02, 2012 at 08:22:51

Okay, I think I see what you are drving at. Yes, given identical slew rates the time required to transition through the reciever switching threshold will be the same. Aside from this, and admittedly not part of my original point, is that the data bandwidth of the lower voltage signal can be greater.
If we take two otherwise identical drivers, the one required to swing less voltage can consequently have a higher slew rate. Amplifier slew rate is a function of a number of parameters, one of which is voltage gain. For a given input signal amplitude, the driver swinging 7V will require 14x the gain of the driver swinging only 500mV. Therefore, the driver having the lower gain can also have a significantly faster slew rate.
What I was intending to indicate is that an AES3 compliant driver could have a higher slew rate if the driver's voltage gain, and thereby, the output signal voltage swing, were reduced. The noise immunity afforded by a whopping 7V signal, while perhaps of benefit in certain noise prone professional environments, is just not needed in the home environment. Said another way, it seems to me that the AES3 driver voltage spec. sacrifices the potential for greater driver slew rate (reducing jitter) for greater receiver noise immunity.
_
Ken Newton

Edits: 06/02/12 06/02/12 06/02/12 06/02/12

Follow Ups:

RE: Slew rate. - rick_m 18:08:35 06/02/12 (0)
"the data bandwidth of the lower voltage signal can be greater."

I'm all in favor of that. Believe me I'm not a fan of bad interfaces, and the scope of my comment was very limited. I certainly wasn't advocating the scheme we were discussing!

Interfaces of all sorts are important and in general I think their lack of adequate definition and control in home audio is the root of most audio oddities discussed on this site.

Rick
Higher slew rates can make interface jitter worse - slider 12:54:21 06/02/12 (1)
But as with many things in audio, it really depends on a variety of unspecified parameters. Jitter is often dominated by waveform distortion products, so higher slew rates necessitate a wider bandwidth interface, and the jitter may actually become worse in a bandwidth-limited interface. Some have actually improved performance by limiting the transmission slew rate, and clock filters are even sometimes useful in D/A convertors.
- RE: Higher slew rates can make interface jitter worse - knewton 05:16:43 06/03/12 (0)
  Impedances need to be matched throughout the interface. If the driver output, cable, connector, and receiver termination impedances (not to mention the power supply decoupling) are not correct, then there's little that simply increasing slew rate can do to improve the situation. It may make things worse, as you suggest. Our discussion of reducing interface jitter by increasing driver slew rate assumes that the related interface parameters have been properly addressed.
  _
  Ken Newton
  
  Edits: 06/03/12

Post a Followup:

FAQ

Post a Message!

Forgot Password?

Moniker (Username):
Password (Optional):
	Remember my Moniker & Password (What's this?) Eat Me
E-Mail (Optional):
Subject:

Message:	(Posts are subject to Content Rules)

Optional Link URL:
Optional Link Title:
Optional Image URL:
Upload Image:
E-mail Replies:	Automagically notify you when someone responds.

To view your new posting or follow-up, click on the RELOAD or REFRESH button on your browser.

This post is made possible by the generous support of people like you and our sponsors: