The original wall wart was 9VAC, which is rectified inside the chassis with small SMD diodes in a full wave bridge configuration. Even as audio design is not my primary sphere of interest, the recent transition to LP records and my effort to do the de-claudization and return to analogue "value" starting form the beginning of this year, made me interested in the improvement of the existing gramophone pre-amplifier. the fact that I got a built-in preamp with the Pioneer PLX500 gave me the freedom to upgrade the ART DJ-PRE II that I get as a reserve. As you see, the DJPRE II has "low cut" filter switch together with input capacitance selector (100 or 200 pf). It also has a clipping indicator and variable gain switch.

G'day all, the ART like many similar designed phono stages uses the 'non inverting op amp voltage stage with gain' approach and whilst that approach works well enough in practical terms the reality is that it cannot provide the intended 'ongoing 6 db/octave rolloff in the treble range required in the original RIAA specification. A-weighted signal to noise ratio ("SINAD") is 83 dB for DJPREE II beating the 80 db for Pluto. Both companies spec 90 dB. 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.

DJPRE II: Phono Preamp for Modern DJs!

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. It seems that many modern phono stages have inadequate overload margins, but far better noise performance than vinyl replay justifies. I would much rather see a S/N ratio of, say 70dB but a 25dB overload margin, than 80dB of S/N ratio and less than 20dB overload margin. 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): I have the ART DJPre II and Cambridge Audio 551P. The ART is exceptional value, especially with the features it offers, but for sound-quality I would go for the 551P, which in my experience has a more full-bodied sound. There's probably little point in paying the extra for the 651P, unless you want an MC input in the future.[/quote]

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. The DRJPRE II has a clipping indicator. I find out that it lights up at just 0.01% so pretty conservative. added 1000uF alu-polymer cap on opamp pins (I assume they have the same rails so doesn't matter which one) 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. The ART DJPRE II is a great bargain here. Other than some strange phase shift at low frequencies and lower input dynamic range, it actually beats the more expensive u-turn Pluto in the rest of the measurements.

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. Both 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. 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. With the capacitance of the tonearm cable, interconnects, and the Djpre II internal loading capacitance of 100pf, I was getting a resonant peak at roughly 11.4khz give or take, which was readily apparent in listening tests.

I was a bit skeptical of the difference these changes would make, but listening tests confirmed what others have noticed. Finally, let's look at distortion and noise of a 1 kHz tone with 5 millivolt input but without a-weighting:

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The ART QC engineer consulted the Design engineer who both shared their knowledge of this circuit and helped me to get rid of that last 100pf load capacitance, which in turn got rid of the resonant peak (at least to my ears).

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.When selecting the low-cut filter on DJPRE II, we indeed get a low cut (not as steep as Pluto though) but also a high-cut above 19 kHz or so. Not sure that is a bad thing but it is not what the button says it is doing. I posted this about my observations after setting the gain on the Art to -6db on another forum, and wanted to include it here also: Another added bonus is on this receiver (TX-870), the CD input has a "CD Direct" setting, which allows you to bypass the receiver preamp and associated tone controls. So, if you are in a listening situation when you desire a perfectly flat audio response, just switch to "CD Direct". Otherwise, you can adjust all the tone settings as usual.