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#1
Posted to rec.audio.high-end
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Erratum
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. |
#2
Posted to rec.audio.high-end
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Erratum
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. |
#3
Posted to rec.audio.high-end
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Erratum
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. |
#4
Posted to rec.audio.high-end
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Erratum
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. |
#5
Posted to rec.audio.high-end
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Erratum
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. |
#6
Posted to rec.audio.high-end
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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 |