Erratum
dave a wrote:
Sonnova wrote:
On Thu, 16 Jul 2009 02:05:31 -0700, dave a wrote
(in article ):
Sonnova wrote:
I recently replaced a pair of Burr-Brown
OPA134s in my 24-bit D/A converter with the LME49710NAs and heard a big
improvement, especially in the noise floor and perceived distortion.
You must have a lot of noise or very, very good ears. Most noise floors
are way below most folks hearing.
It doesn't really manifest itself as "noise" in the traditional sense. It's
more like the music emerges from a "deeper black" background. I know that
this may well be my imagination, but I noticed it right away on one of my own
24-bit/96 KHz recordings. I thought I knew this particular recording
perfectly, but never had the background been so velvety quiet. There was
always some sound even when the ensemble was not playing, rustling music
sheets or squirming in their chairs. But not any more... Not at all
scientific, but there it is.
Good to know the new op amps got rid of the background noise. I didn't
know they could do that.
These are very very different type opamps. The OPA134 is a high impedance
input, low bias and offset current device, the LME49710 is a low
impedance device best used with a source impedance of say 1K ohm. The current
noise of the LME49710 is vastly higher. Most DACs are low impedance
devices, so the LME49710 makes sense. Its voltage noise is 2.5nV per root Hz versus
8 nV per root Hz for the OPA134, which is about 10 dB. Both are excellent
devices for their intended uses.
Doug McDonald
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