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U-Turn Pluto 2 Review (Phono Preamp)

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amirm

amirm

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@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

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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

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@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

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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

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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.
 
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amirm

amirm

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@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

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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

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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.
 
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