U-Turn Pluto 2 Review (Phono Preamp)

[norcalscott]

Thank you for the review, Amir. I own a U-Turn turntable with this built in and I have been very pleased with the performance and these measurements confirm my impressions.

I also highly recommend U-Turn as their customer service has been great for me - I had an issue with my cue dampener and they sent me another one no questions asked and did not ask for the bad one in return. They also sell replacement parts, like belts at great prices.

I don't listen to my vinyl collection much, and SQ is obviously better for digital source through DACs for the most part, but I do have a few albums, like an original Steely Dan Aja pressing that I believe sounds fullest and best in that format. In any event, vinyl is a fun nostalgic experience for me.

 

[JensH]

Not challenging you just trying to learn. How can you tell how the 4 diodes are wired by looking at the top of the PC? Seems like the 4 diodes could either be a regular bridge or a doubler. Thanks.

On the higher resolution picture it is clear that the anodes of D1 and D2 are connected to the ground plane. The cathodes of D3 and D4 are connected to the filter capacitors C31 (electrolytic) and C32 (ceramic) as well as to the input of the 12 V regulator (U2). The diodes D5 and D6 protect the voltage regulator.
So a straight forward design for the positive supply. The charge pump for the negative supply is a bit more unusual, but the switch frequency should be well outside the audio band, so probably not a real issue.

 

[B4ICU]

So, this is a nice review of a budget phono stage - thank you Amir. It does well for its price point and will give budget minded folks some "bang for their buck".
Based on your posting it would seem you have no interest in vinyl record playback. If that is true, then why would you even read up on a phono stage review or really anything to do with vinyl records? This all seems very argumentative to no purpose.

I read them all.

 

[Angsty]

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.

 

[Helicopter]

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.

Agree on relative value...

The circuit board layout is unusually elegant. Fit for an electronics textbook. I might pick it for that.

 

[Rottmannash]

In all the preamps Amir has measured which has the greatest bang for buck value?

 

[Bob from Florida]

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.

From personal experience the Mani overloads easily if the dip switches select hi gain for the first stage. The Pluto 2 is fixed gain so no chance of picking a "bad" combination of gain settlings. Could work well with the right cartridge, etc.

 

[thefsb]

I enjoyed the return of the Jedi, The return of Rocky 75, and many more.
I don't enjoy the return of the LP. It's so wrong...

Everything you wrote about the technical advantages of the CD are correct.

And I feel that the return of the LP is wrong also for environmental reasons. I bought two of them in the last year or so. One is something I could only find as an LP, the other was part of luxury package together with FLAC downloads, a poster and a cassette that I chose because I wanted to support the artist, who was in financial trouble in old age and ill health. Relative to downloading files, the total costs of the LPs are unacceptable.

And yet I still dislike CDs. I have about 2000 of the damn things. As an engineer with much experience in industry standardization, I admire the CD very much. But I dislike them too. I wrote about it a while ago and just now republished the short article.

Compact Disks make you immoral

That was before the new vinyl wave really kicked in. Since then I have come more and more to dislike the nostalgia industry.

 

[sergeauckland]

Everything you wrote about the technical advantages of the CD are correct.

And I feel that the return of the LP is wrong also for environmental reasons. I bought two of them in the last year or so. One is something I could only find as an LP, the other was part of luxury package together with FLAC downloads, a poster and a cassette that I chose because I wanted to support the artist, who was in financial trouble in old age and ill health. Relative to downloading files, the total costs of the LPs are unacceptable.

And yet I still dislike CDs. I have about 2000 of the damn things. As an engineer with much experience in industry standardization, I admire the CD very much. But I dislike them too. I wrote about it a while ago and just now republished the short article.

Compact Disks make you immoral

That was before the new wave really kicked in. Since then I have come more and more to dislike the nostalgia industry.

Environmental issues aren't a problem if you buy used LPs, as I do. You buying them keeps them out of landfill, so a Good Thing.

As to CDs, ditto really. I mostly buy used CDs, or better still, downloads which don't create any more plastic. Where possible, although difficult, I try and get the download from the artists' own website, thus both avoiding plastic and hopefully benefitting the artist more.
Ultimately ALL consumption is bad, but we still have to live, as do the artists/suppliers/everyone else that sells to us.

 

[Lttlwing16]

In all the preamps Amir has measured which has the greatest bang for buck value?

Keep your eyes peeled for the Darlington Labs MM-5 ($179) which was ordered to drop ship to Amir a week or so ago. It may win the "bang for buck" prize. Or not..

 

[thefsb]

Environmental issues aren't a problem if you buy used LPs, as I do. You buying them keeps them out of landfill, so a Good Thing.

As to CDs, ditto really. I mostly buy used CDs, or better still, downloads which don't create any more plastic. Where possible, although difficult, I try and get the download from the artists' own website, thus both avoiding plastic and hopefully benefitting the artist more.
Ultimately ALL consumption is bad, but we still have to live, as do the artists/suppliers/everyone else that sells to us.

Yes, of course, used vinyl is quite a different matter, especially if you get it at a charity store, and I totally get the attraction of browsing and shopping from used record stores, even online.

But when I get an email from, say, Sahel Sounds about a new release and I see the options: download or LP, that's a problem.

I'm not sure about the consumption of art being necessarily bad. It can be but isn't always and doesn't need to be.

 

[thefsb]

In all the preamps Amir has measured which has the greatest bang for buck value?

Bang is subjective. Some want glowing vacuum tubes. Others want something to just work and be invisible. Others want the highest SINAD score. What's your bang?

 

[Rottmannash]

Bang is subjective. Some want glowing vacuum tubes. Others want something to just work and be invisible. Others want the highest SINAD score. What's your bang?

High SINAD, low distortion and linear freq response. Uncolored-vinyl is colored enough on its own.

 

[amirm]

SINAD is not very instructive for these amps since it is dominated by noise, not distortion. I say best measurement to look at is the frequency response. That determines colorations it may add to everything.

 

[Rottmannash]

SINAD is not very instructive for these amps since it is dominated by noise, not distortion. I say best measurement to look at is the frequency response. That determines colorations it may add to everything.

Thanks. Will do.

 

[Angsty]

From personal experience the Mani overloads easily if the dip switches select hi gain for the first stage. The Pluto 2 is fixed gain so no chance of picking a "bad" combination of gain settlings. Could work well with the right cartridge, etc.

But, that also means that there are many MC cartridges you could not try on the Pluto that you could with a Mani. With that being said, I can't think of any new MC cartridge you can buy for the cost of a Mani, but there are several MM cartridges at the cost of a Pluto or less.

 

[Angsty]

SINAD is not very instructive for these amps since it is dominated by noise, not distortion. I say best measurement to look at is the frequency response. That determines colorations it may add to everything.

With that sage advice, perhaps I dismissed the Pluto 2 too quickly relative to the Mani. The Pluto has a reasonably flat frequency response plus a rumble filter, which might prove useful for turntables in its likely partner target range. The Mani appears to elevate subsonic frequencies.

 

[Bob from Florida]

But, that also means that there are many MC cartridges you could not try on the Pluto that you could with a Mani. With that being said, I can't think of any new MC cartridge you can buy for the cost of a Mani, but there are several MM cartridges at the cost of a Pluto or less.

MC cartridges did not work well with the Mani for me. The 47 ohm load is a curious choice as the cartridges that work with that load are usually very low output. I had 2 different MC that did like the loading - at least in theory - Lyra Parnassus and Miyabi MCA. I also tried a Denon 103 - budget MC that needs in my experience 470 ohms load - and it lost a lot of treble with the 47 ohm load. The Mani needed all its gain - 59 db - and it would distort easily with those cartridges. Using a step up transformer - tried 3 different step ups, 20, 24, 28 db - with the Mani set for 42 db / 47K and it worked better. However, I had better results on the Mani with inexpensive MM cartridges and one expensive MM - Sumiko Pearl, Nagaoka mp 110, Clearaudio Maestro 2. Those same MC's worked with a better phono preamp without audibly distorting. All of these cartridges cost more than the Mani or the Pluto - except for the Pearl if memory serves. My point about the Pluto - without testing one - is the lack of adjustability is a plus in its price range. You will choose an appropriate MM or MC with step up transformer / head amp to work with the 47K ohm / 40 db and possibly be very happy. High output MC - such as Hana EH at $450 - is another choice. The Mani worked pretty well for me with the MM cartridges. I suspect the adjustability had more to do with marketing than real world use.

 

[Angsty]

The Mani worked pretty well for me with the MM cartridges. I suspect the adjustability had more to do with marketing than real world use.

No argument there -- I, too, think it is more of a marketing move. 100 ohms would have been a better middle of the road MC loading. Is there even a transformer that makes economic sense to use with a ~$100 phono (either Pluto or Mani)?

I don't really think the Mani is a good choice for most MC cartridges; it just offers the possibility of use. Practically, though, the Pluto could be a better choice for some users.

 

[DualTriode]

That graph is pure THD without noise. So the distortion is rising in lower frequencies as well.

@amirm,

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

The test stimulus is a Farina sweep. The software takes the test frequency and sums the measurements at the harmonic distortion frequencies. This sum is calculated and plotted as “THD”. By summing only the magnitudes at the harmonic frequencies the assumption is that the noise between the harmonic frequencies is excluded making the plot pure THD.

In this case the device being measured is dominated by noise. The software is unable to determine if the magnitude measured at the harmonic frequencies (H2, H3 …H9) is harmonic distortion peaks or noise. The noise at the HD frequencies is summed and incorrectly reported, not as noise but as pure THD.

Take a look at the FFT in the dashboard; the plot is labeled as “No-Distortion”, the distortion if there is any is completely buried in the “Noise- Floor”

Better to stick with THD+N or SINAD if you ask me.

Thanks DT