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Sonnova Sonnova is offline
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In an earlier post, I mentioned upgrading a Crown IC-150 pre-amp by replacing
the original LM301 op amp with a new National Semiconductor LM4562NA. It's
been a number of years since I owned an IC-150 and I had forgotten that the
LM301 is a SINGLE op amp package and the LM4562 is a DUAL op amp package. The
correct modern, low noise, high-slew rate and symmetrical-slew operational
amplifier to replace the old, noisy, slow, non-symmetrical slew rate LM301
with is the National Semiconductor LME49710NA which is the 8-pin mini-dip
single op amp version of the LM4562. The LME49710NA IS a direct drop-in
replacement for the LM301/LM301A 8-pin mini-dip packaged use in the Crown and
I'm sure that it will noticeably improve the pre-amps performance. Even
though I haven't done this modification, I once did own an IC-150, and I did
replace the LM301 with then new National Semiconductor FET input op amps and
the result was much better sound and 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. So, I'm
pretty confident that replacing the ancient, wheezing LM301s in an IC-150
will yield similar results. I don't actually suspect that my misstatement
has caused anyone any inconvenience, but in the interest of accuracy, I did
want to correct my error.
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dave a dave a is offline
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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.

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Sonnova Sonnova is offline
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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.
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dave a dave a is offline
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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.

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Sonnova Sonnova is offline
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On Thu, 16 Jul 2009 08:55:01 -0700, dave a wrote
(in article ):

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.


No, they don't. I said it mede the silence BETWEEN the playing, rustling of
sheet music, and the musicians squirming in their chairs much darker. The
music appears from a much blacker silence. I don't know how else to describe
it.


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mcdonaldREMOVE TO ACTUALLY REACH [email protected] mcdonaldREMOVE TO ACTUALLY REACH ME@scs.uiuc.edu is offline
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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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