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Millennia vs. Grace
Old 3 weeks ago
  #31
The last Grace I saw used the BurrBrown 1N163 instrumentation amp for the mic amp. It's noise specs are not the best.

The HV3 used BurrBrown OPA604 opamps with the now discontinued Analog Devices MAT 04 quad transistor front end chip, rated at about 2.5 nv noise spec, much worse than the MAT 02 dual or the also discontinued MAT 03 PNP transistor pair at .7 nv noise.

The old BB OPA 604 opamp has a lot of distortion, a fft shows a picket fence of harmonics up to the 11th order. Those reside at about -110 dbu, audible.
Old 3 weeks ago | Show parent
  #32
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Jimbo's Avatar
 
1 Review written
🎧 15 years
Quote:
Originally Posted by Jim Williams ➡️
The last Grace I saw used the BurrBrown 1N163 instrumentation amp for the mic amp. It's noise specs are not the best.

The HV3 used BurrBrown OPA604 opamps with the now discontinued Analog Devices MAT 04 quad transistor front end chip, rated at about 2.5 nv noise spec, much worse than the MAT 02 dual or the also discontinued MAT 03 PNP transistor pair at .7 nv noise.

The old BB OPA 604 opamp has a lot of distortion, a fft shows a picket fence of harmonics up to the 11th order. Those reside at about -110 dbu, audible.
Great info, Jim. Always appreciated.
I believe the 1N163 is the same part used in the GroupDIY (I forget the person) Green Pre. Pretty simple stuff!
Grace has fancy knobs though.
Old 3 weeks ago | Show parent
  #33
Gear Addict
Quote:
Originally Posted by Jim Williams ➡️
The last Grace I saw used the BurrBrown 1N163 instrumentation amp for the mic amp. It's noise specs are not the best.

The HV3 used BurrBrown OPA604 opamps with the now discontinued Analog Devices MAT 04 quad transistor front end chip, rated at about 2.5 nv noise spec, much worse than the MAT 02 dual or the also discontinued MAT 03 PNP transistor pair at .7 nv noise.

The old BB OPA 604 opamp has a lot of distortion, a fft shows a picket fence of harmonics up to the 11th order. Those reside at about -110 dbu, audible.
How do you know HV3 used BurrBrown OPA604 and MAT04? I remember the surface is scratched out and heatsink installed...
Old 3 weeks ago
  #34
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David Rick's Avatar
 
🎧 15 years
It's easy to look at a particular part in a commercially-manufactured product and say, "I know a better one, therefore the maker is cutting corners!", but that doesn't make it so. You don't know why the original designer chose that part, but they may well have had a good reason other than the price. For instance, John LaGrou's choice of a '604 family op amp on the back end was because that was one of the only ones available that could run from +/- 24 rails and the extra headroom improved the sound during loud orchestra climaxes. He found this out throught actual listening tests. The MAT04 was one of the only quad-matched low-noise arrays available at the time; there are other choices today, including the THAT Corp 300 series. Originally, John allowed you to order the HV-3B with a potted set of hand-matched transistors instead, but I don't know how many he actually sold.

The Grace mk1 and mk2 preamps should sound different: the latter is fully balanced from input to output like the Millennia. Lots of designers used Burr Brown instrumentation amps on the front end. Where the Grace differed from others was Michael's use of a Current-Feedback Amplifier chip on the back end. These were pretty novel at the time, having been introduced just a few years earlier by Comlinear, located here in Colorado. The claim to fame of a CFA is that it has very high bandwidth (suitable for video signals) and that its bandwidth doesn't change with the gain setting.

David L. Rick
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