ART DJPRE II Phono/Line Pre-Amplifier

Product Information

Frequency Response: This ranges from 10Hz to 50KHz, with a +/-.5dB tolerance that is enough for the size and functionality of the Pro Audio DJ PRE II. Many owners of this unit report that it sounds much better on battery power, or as reported in this post it can sound just as nice with a good quality regulated supply. Here is a "dashboard" view of how the two perform using 1 kHz tone at 5 millivolts, with A-weighting filtering of the output (making it more perceptually relevant):

Spec do not show its en(Equivalent Input Noise) value but it si perform better then 3-4nV/√Hz devices on 10, 100 and 1kHz so it have to be below 4nV/√Hz. The next characteristic of the TS972 is a THD (no noise, distortion only) of 0.003% which means that the first next harmonic will be 3.0E-5 weaker than the carrier signal which is only -90dB, if you think that is a lot add to this value and noise and gain and there you are in the audible range of below -70/80dB. But wait THD value is for AV=-1 only.

Tech Specs

ART products have earned the trust of clients' trust worldwide, whether in recording studios, nightclubs, arenas, auditoriums, churches, rehearsal halls, basements, or garages. Our illustrious past displays our genuine love of music and the creative process. added 1000uF alu-polymer cap on opamp pins (I assume they have the same rails so doesn't matter which one) As you see, the output is 0.306 millivolts which corresponds to a gain in db of 35.6 or so. This matches the specification of Pluto and is within the range that DJPRE has.

I think that both these items show a failing in modern Phono preamps, that of limited headroom. Preamps need an absolute minimum of 20dB above their nominal sensitivity, which needs to be in the range of 3.5mV to 5mV for 500mV output, and therefore with a maximum output of 5V before clipping.Also, I know these particular stages are budget stages, but why don't the more upmarket ones provide balanced inputs as standard? One gets unnecessary balanced inputs on line stages and domestic power amps, yet unbalanced inputs on the only items where they would be fully justified. The ART DJ Pre II provided a very flexible and clear way of boosting the phono signal to match the volume of the AppleTV. Unlike many other phono preamps, this one has an easy gain knob that lets you dial in a specific amount of amplification. All in all, since this post was long enough to make it a little shorter, I tore out all the Op.Amps, Ordinary electrolytic capacitors and thoroughly reworked the power supply with the necessary addition of components. The DJPRE II, which is housed in a metal chassis somewhat more significant than a DI box, contains a gain-trim knob and a dual-color signal/clip LED on the front panel in addition to the two switches as mentioned earlier. The machine may be powered through USB, the included converter, or any DC source ranging from 7 to 12 volts or any AC source ranging from 9 to 12 volts. There is no USB cable included; however, any regular USB cable will work.

The original wall wart was 9VAC, which is rectified inside the chassis with small SMD diodes in a full wave bridge configuration. So for a good solution we need any bipolar Op.Amp that can give at least SVR of -110/120dB, and below 8nV/√Hz at 10, 100Hz and even at 1kHz (and not in the ultrasonic range at 100kHz like TS972). 220p input, and the treble peak wants to eat your ears for breakfast (though it sounds clean otherwise, so I doubt it's the stylus - I bought a spare just in case). Originally the cable would have been much shorter, and the phono input in the amplifier that went with the unit had 47 pF of input C, bringing the total close to the upper end of the recommended 100-200 pF load range. Log(THD-N/100)+ 20x Log(AV) ---> -136.478+40 => -96.478dB which is translated to NJM specs equal to 100% * 10Both devices are remarkably the same with one significant difference: the pluto bleeds noise from its power supply rectifier into its output. You can see this in harmonics of mains 60 Hz in blue. The DJPRE II actually has higher mains hum at 60 Hz, but it is otherwise much cleaner relative to power supply noise. DJPRE II's distortion spec is <0.01% and we are getting less than that at 0.007%. So good on them for being conservative.