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Blue Circle Audio
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The Custom Shop
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NSC Stereo Preamplifier with DCRN Power Supply Network.
When one of our dealers auditioned the NSL amplifier with his BC107 preamplifier, he was very much impressed with the results but, of
course, asked Gilbert what would an ideal preamplifier for the NSL be like? What could enable it to realize all of its potential. Gilbert’s
response: an NSL integrated amplifier!
Shown optional walnut curly maple front panels
And so, of course, our leader went to work. The chief weakness of a preamp/amp combination is that the two units use their own power
supplies, totally separate from each other. Ideally what is wanted is some way to tie these separate power supplies together, so that,
in Gilbert’s words, “they are seeing the same picture at the same time -- so they are working as one. Electrically the two units would
then be working like an integrated amp.”
DCRN network cable connects between the NSC and NSL power amplifier
The ultimate result is a whole new preamplifier that is both technically superior to the BC107 as a preamp for use with any solid state
amplifier (which can also be retrofitted to work with a DCRN) and an ingeniously conceived mate for the NSL in particular. As a preamp,
the NSC is a considerably upgraded 107, with a much larger external power supply and also increased capacitance -- in effect mini KQ
circuits located in such a way as maximize its ability to both ‘enlarge,’ and better define and refine the sound. As a mate for the NSL,
fitted with the DCRN, it is half of a perfect integrated NSL.
We are not accustomed to talking about sound around here but in this case a few words are probably necessary for those who will feel
a need to justify the expense. Compared with the BC 107, both mated with an NSL, the NSC (at twice its price) produces a weightier,
fuller, richer, and more dynamic sound that has all of the 107/NSL’s clarity but in a more rounded form. Definition has greater dimension,
instruments have more of their distinctive color and substance. Overall, the NSL simply feels more forceful, instruments and voices
seem more forcefully present. Michael Wright in his review of the NSL remarked that in his experience upgrading the preamp made a
significant difference in the performance of the NSL. The NSC is clear proof that this is indeed the case.
The immediate result, born this summer (2016), is what Gilbert calls the DCRN (Direct Current Rails Network). It is effected by a
(removable) umbilical cable running between the two units.
Gilbert has always believed that an integrated amplifier done right, without the usual commercial compromises (smaller power supplies,
etc), is superior to separates; and so his answer wasn’t exactly a surprise. But it wasn’t the answer the dealer was looking for. He
wanted a new preamp to work with the NSL...that would be as good as this imaginary integrated.
Rear panel of NSC preamplifier with built in phonostage
The NSC is available with an optional phono stage that in terms of performance approaches that of the standalone BC 703.
Features and Options

*Several cosmetic options available at additional cost.

Standard features......
*Single Stereo - 31 position Shallco attenuators with 2 level gain switches for a total of 62 settings.
*Gold contacts roatary selector switch.
Optional features...
*Dual decks balanced 47 postion Shallco attenuators with 2 level gain switches for a total of 94 settings.
*Processor bypass loop.
*Remote volume control.
*Wide range of faceplate and cover options.
*Headphone amp and jack output

Measurements
Pre-amplifier
-Residue noise reference to full rated output: >- 100 dB or < 60 uV non weighted
-Residue noise reference to full rated output: >- 110 dB or < 20 uV within audio band
-Tracking error: < +/- 0.05 dB
-Hum below 400Hz: <1.0 uV
-Frequency response at 5V output: 10Hz to 55K Hz +0.00db, - 0.00 dB; -1db, -1db at >100 kHz
-Distortion at 5V output: < 0.0028 %
-Voltage gain: 20 dB
-Maximum output (rms) : 8.5V SE, 15V BAL
-volume control range: -95dB to 0db in 62 steps standard in Shallco attenuators
-input impedance: 100K ohms
-output impedance: 2.5 ohms
Dimensions
-Preamp: 17.5" wide x 3.25" OR 5" high x 15.5" deep
-Power Supply: 5.25" wide x 5" high x 15.5" deep
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Contact:  bcircle@bluecircle.com  /  519-469-3215
   
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Above is the line stage version of the NSC as reflected in the preamp chassis dimensions.
  The photos at top of page reflect the dimensions of the NSC with built-in phono stage.