U-Turn Pluto 2 Review (Phono Preamp)

[amirm]

@amirm,

I have a completely view of it. There is nothing pure about the THD plot.

The test stimulus is a Farina sweep.

No, I don't use Farnina sweep for electronics. These are stepped sine measurements with AP prescalar fully optimizing for each level. As a result, the THD levels are quite accurate.

 

[Angsty]

I think the diodes 1-4 are a "full wave voltage doubler" in which case it all makes sense. As far a ripple goes it looks like filter caps were kept to a minimum to save money.

I'm not an electronics designer, but why choose to do rectification and regulation on the board versus sourcing a switching power supply that puts out DC and then working on the board to reduce ripple? Is that a substantially more expensive design choice?

 

[DualTriode]

@amirm

Continuous sweep or discrete steps, what difference does it make?

The software takes the magnitude of H1 the fundamental test stimulus and sums H2, H3, H4 and on up to calculate THD.

Take a look at the FFT on the dashboard for the 1kHz test frequency, the only thing to measure at 2k, 3k, 4k and on up is noise not distortion.

 

[levimax]

I'm not an electronics designer, but why choose to do rectification and regulation on the board versus sourcing a switching power supply that puts out DC and then working on the board to reduce ripple? Is that a substantially more expensive design choice?

Not a designer either but it is probably a combination of cost and marketing. For marketing many people buying a phono stage want a linear PS and you can make a linear supply like this with a handful of very cheap parts.

 

[sergeauckland]

Not a designer either but it is probably a combination of cost and marketing. For marketing many people buying a phono stage want a linear PS and you can make a linear supply like this with a handful of very cheap parts.

I agree, that's probably the reason. I'm constantly amused (and irritated in equal measure,) by those who buy something perfectly adequate, then spend twice as much on a linear power supply and claim 'night and day' improvements.

S.

 

[amirm]

@amirm

Continuous sweep or discrete steps, what difference does it make?

Log sweeps use windowing functions that distortion the measurements to some extent due to lobing/spectrum leakage. This is not a big deal with the distortion order is low and amplitude high, but as we get to higher order ones, accuracy gets lost. For this reason, stepped sine wave is more accurate. The down side is that you only get data at some specific points and measurement is slower. So classic compromise between speed and accuracy.

 

[Jmudrick]

I was looking for a phono preamp that would work well through the analog input of my Paradigm PW-Link streamer/ARC. Flipped a coin between the Schiit and the Pluto 2, Pluto 2 won and with my AT150MLX cartridge the gain is perfect and it's dead quiet. Quite happy with the setup.

 

[milosz]

I hope we will some day see some SINAD measurements of actual vinyl playback. The results are likely to be so much worse than test results of any phono stage that I think many people will be shocked.

 

[anvias]

The Pluto 2 seems to perform a bit worse than the original Pluto, which seems odd. Both perform less well than the Schiit Mani at about the same price point; the Mani costs about $30 more. The ART DJ Pre II also performs better for even less money.

The only reason I see to buy this preamp appears to be convenience when bundled with a non-preamp equipped Orbit.

I recently switched from the Mani to the Pluto 2 because my apartment has severe RF interference from a mobile transmitter tower on the roof immediately above me. The Mani was picking up a significant amount of interference, clearly audible in quiet sections of a record, whereas the Pluto is dead silent. So the Pluto may have better RF shielding, which for me is worth it.

 

[Cwopete5]

I owned the Pluto 2 for three days and returned it. Compared to my Emotiva XPS-1 GEN 2, the Pluto 2 was dull and lifeless. While I can see the Pluto 2 has good measurements and is on the "recommended" list, from a listener perspective, it lacks the dynamics of the Emotiva.

 

[cgallery]

Any idea how difficult it may be to reduce gain to somewhere around 34 or 35db on one of these?

I imagine there are two to four resistors that may need changing?