Low Noise Designs
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About a year ago I decided it's time to enjoy again my vinyl collection. I bought a second hand VPI HW19 turntable with an Audioquest PT-9 tonearm and a Benz Micro Silver high output MC cartridge, upgraded to the Aries inverted bearing and platter. I enventually replaced the Audioquest tonearm with a SME Series III tonearm (with damping trough, to accomodate low compliance cartridges) and added a Benz Micro Gold MC low output (0.4mV) cartridge and a Clearaudio Wood MM (3mV) cartridge.
The first challenge after purchasing the turntable was to find a RIAA phono preamp. I got originally a NAD PP3 phono preamp, paying $150 for essentialy a couple of 5532 opamps in a small metal case. After a little listening, I was having difficulties plotting the fastest course to BayBloor Radio to return the thing...
So, not willing to pay $1000+ for what it is supposed to be a decent phono stage, I decided to DIY one. This project the became (as usual, I would say) a challenge... How far can we push a phono preamp performances? How large should be the headroom (the usual tubes guys catch)? Are distortions important? What are the best grounding and layout methods?
Oh, and I hate hiss and hum. In 90% of the current high end phono stages, hiss is clearly audible in 96dB horns from 1 meter, not to mention a faint hum, even with the inputs shorted. Two phono stages were though close to what I was looking for: the Vendetta Research and the Pass XONO, both in the multi-thousands price range. Can it be done for less and with even better performances?
And here I got a series of projects, under the common name of High Performance phonoStage (or shortly HPS). From the 1nV/rtHz noise HPS 1.0, then down to the 0.7nV/rtHz HPS 2.0 and then the HPS 3.1 with 0.32nV/rtHz noise, 0.01% distortions, 32dB headroom (clips at 20mV input at 60dB gain) and zero caps in the signal path. And finally the fully bipolar HPS4.1 with virtually zero input bias current, 47Kohm input impedance, 0.28nV/rtHz noise, 80ppm distortions over the entire audio band and output levels up to 40Vpp, and 32dB dynamic range.
So enjoy this journey in the Land of Silence.
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