Conrad Johnson DA2b Digital/Analog Converter Vacuum Tube Digital Processor

I am not new to AudioGon but this is my first time selling but you can check my feedback on ebay under victor3D...I am a power seller with 100% feedback rating.

This unit has just been serviced by Conrad Johnson, one capacitor replaced and everything else gone over. The unit has been fitted with an upgraded power cord and is in superb condition. I have two identical units both serviced by CJ and am selling one off. I love mine. CJ has supplied a printed manual that will come with the unit. My price is firm at $1,000 and I will pay UPS shipping in USA. World Wide you pay shipping. Paypal is extra if you prefer it. Has to be a 9+. Those who have one would not part with it. I was informed by CJ that according to the serial number that this is one of the last units that was produced and superior sound to the newer ones (in the technicians opion based on his listening tests)

The D/A-2b

A digital processor accepts the data stream from the transport and converts the numerical data back into music. Several circuits are involved in this process. Of these, data conversion, analogue filtering and power supplies are particularly important to faithful music reproduction.

We have chosen to use bit-stream DAC chips for these processors because we find that they offer by far the most musical performance. The edgy, unmusical sound that we typically find with multi-bit DACs is probably attributable to a type of crossover-notch distortion which is intrinsic to these designs, and absent from bit-stream converters. This distortion is essentially invariant to signal amplitude, making it most noticeable on delicate musical passages, obscuring ambience information, tonal nuance, and harmonic subtlety The bit-stream approach reproduces these important elements of musical information far more naturally

The final stage of any DAC is the analogue output stage. This stage is a low-pass filter, designed to remove high-frequency (supersonic) artifacts of the conversion process. In the majority of units presently on the market, this critical function is performed by an IC op-amp, with much the same result as would be expected from using that device in a preamplifier. In contrast, the output stages of the D/A-2b and D/A-3 are designed and executed in much the same way as our preamplifier circuits, using discrete devices - the D/A-2b using vacuum-tubes, the D/A-3 using field-effect transistors.

Always important, power supply des critical to the musical performance of a tal processor, because of the need to isolate the sensitive analogue audio stages from the very high-frequency noise generated in the digital sections. In the D/A-2b and the D/A-3, dc voltage is supplied to the audio stage by a discrete regulated power supply, designed to offer vanishingly low impedance at all audio frequencies. These power supplies use polypropylene and polystyrene capacitors exclusively A similar, separate regulator supplies DC to the analogue circuits in the DAC chip - the origin of the audio signal.

The DR-1, D/A-2b and D/A-3 have been designed and produced with care to transform digital sources into a musically rewarding experience. These digital playback systems offer depth and focus of soundstage, tonal accuracy, and an ability to convey nuance in musical performances that many audiophiles have felt would not be possible from compact disc.

Specifications:

Sensitivity: 1.0 VRMS output at 0 dB (maximum output)

Distortion: less than .05% THD

Bandpass: 5 Hz to 20 KHz, +0, -5 dB

Hum and Noise: 92 dB relative to 1.0 V output

Phase: 0, 180 degrees of phase shift switch selectable

Inputs: One RCA coaxial, one BNC coaxial, one TOSlink optical. ST Glass optical input is optionally available.

Digital Output: one BNC coaxial

Dimensions: 14.375D x 19W x 3.315H inches

Weight: 19 tbs.