Art Pro Audio Djpre Ii Phono Turntable Preamplifier Review

This is a review, comparing and detailed measurements of Review and Measurements of u-turn Pluto and ART DJPRE Two Phono Preamplifiers. Both fall in the category of budget products with the Pluto retailing for USD $99 and the DJPRE II for just $49 (both include Prime shipping). Of the two, the DJPRE Two has more bells and whistles:

View attachment 13107

As you see, the DJPRE 2 has "depression cut" filter switch together with input capacitance selector (100 or 200 pf). It also has a clipping indicator and variable proceeds switch.

The u-turn pluto on the other hand, is fixed function. No switches, indicators, or annihilation else other than the power LED.

Between the two, I similar the expect of the Pluto improve. The DJPRE II screams hobby project box. And that brilliant blue LED is mortiferous. Needs some black tape to embrace it for certain. It is a sturdy box though so it is just a visual preference.

Both units accept external transformers. Pluto has its own branded unit that has 9 volt Air-conditioning at 670 milliwatts. The DJPRE 2's transformer also outputs Ac at ix volts and one thousand milliwatts. Interestingly enough both are identical in size so not sure about the ratings beingness correct. The fact that these are AC adapters means that rectification to DC is inside each unit.

There is not much else to them. So permit's go into measurements and see how they do.

Measurements
Nosotros are breaking new basis here with our first exam of phono pre-amps so expect future measurements to vary based on feedback to this thread. In addition, I am using my new Audio Precision APx555 and then conduct with me as I refine these graphs and settings over time.

To brand the testing easier, I merely tested 1 channel of each unit. That allowed me to test them simultaneously. For input voltage, I picked v millivolt. Both of these phono preamps are for moving coil and the research I did showed range of cartridge outputs of three to six millivolts. I don't encounter an industry standard for measurement. Let me know if you know of one.

Hither is a "dashboard" view of how the two perform using ane kHz tone at v millivolts, with A-weighting filtering of the output (making information technology more perceptually relevant):
View attachment 13108

I know, lots of data . Let'due south take a bit at a time.

For starters, I adjusted the variable output of the ART DJPRE II to match that of u-plow Pluto. This setting was just past the "zilch" dial (around +i). This is good every bit it means the DJPRE II has expert range of input sensitivity.

As yous see, the output is 0.306 millivolts which corresponds to a proceeds in db of 35.6 or so. This matches the specification of Pluto and is within the range that DJPRE has.

Distortion with this a-weighting is 0.01% on Pluto. Manufacturer rates it at < 0.005%. Maybe at a unlike input level information technology gets closer to that.

DJPRE II'due south distortion spec is <0.01% and nosotros are getting less than that at 0.007%. So expert on them for being conservative.

The DRJPRE Ii has a clipping indicator. I notice out that it lights up at just 0.01% so pretty conservative.

A-weighted signal to noise ratio ("SINAD") is 83 dB for DJPREE II chirapsia the 80 db for Pluto. Both companies spec 90 dB.

See? It wasn't so bad.

Next, let'due south await at frequency response:
View attachment 13109

Hither we have iii graphs: one for Pluto and 2 for DJPRE Ii with its filter switch to Flat and Depression Cutting. When gear up to flat, the DJPRE indeed has a flat response that extends past fifty kHz. The Pluto has a low-cut congenital-in per specification.

When selecting the depression-cut filter on DJPRE II, we indeed get a low cutting (not as steep equally Pluto though) merely also a high-cut higher up 19 kHz or so. Non sure that is a bad thing but information technology is not what the push button says information technology is doing.

Somewhat related to this, I ran a sweep to see how the phase varies based on frequency and got this:
View zipper 13110

Here, information technology is Pluto's turn to smash the stage response with substantially zero difference at all frequencies. The DJPRe Two though starts to accept a negative phase shift below one kHz and it progressively gets worse downwardly to 20 Hz at some 66 degrees. Selecting the low-cut filter makes things ameliorate with a positive phase shift that starts at fifty hz and goes up 20 degrees or so at xx Hz. I am not certain what is going with the DJPRE 2 here. I tin can run across a phase compensation at higher frequencies but not lower.

Next let's sweep the input level from 1 millivolt to 50 millivolt to see when overload occurs:
View attachment 13111

Here, Pluto does amend with onset of clipping at 31 millivolt input level. The DJPRE II on the other manus, starts clipping at 22 millivolts. And so those pops and clicks volition be more obnoxious on the DJPRE Ii bold they rising up to such levels.

Finally, permit's look at baloney and racket of a ane kHz tone with 5 millivolt input merely without a-weighting:

View zipper 13112

Both devices are remarkably the same with one significant departure: the pluto bleeds dissonance from its ability supply rectifier into its output. You lot tin see this in harmonics of mains sixty Hz in blue. The DJPRE II really has higher mains hum at lx Hz, only it is otherwise much cleaner relative to ability supply racket.

I think that is it. It is i:00am then I am going to get to sleep. Leave me feedback on what you remember of these results and I will read them when I wake up.

Conclusions
The Fine art DJPRE Two is a great deal here. Other than some strange phase shift at low frequencies and lower input dynamic range, it really beats the more than expensive u-plough Pluto in the residual of the measurements.

The main fault I see with the Pluto is the power supply noise. A fleck more than attention there could accept hands landed it on tiptop.

Both are groovy bargains from what I can encounter. Personally I detect the DJPRE Two a more than flexible unit so if I had to buy ane, it would be that if I could hibernate it some place.

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Equally always, questions, comments, corrections, etc. are all welcome.

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Source: https://audiosciencereview.com/forum/index.php?threads/review-and-measurements-of-u-turn-pluto-and-art-djpre-ii-phono-preamps.3457/

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