ART Precision Phono Pre Review

[aladar]

As there's a fair bit of mains power supply noise, I wonder how much better the SINAD would be if the power supply was changed for a 12v DC supply. Then, all the AC would stay out of the box.

I've noticed this with a few items with external AC supplies, they're quieter if fed DC. Presumably the internal smoothing isn't great so feeding in already smoothed DC helps a lot.

S

I was thinking exactly the same thing….

 

[Helicopter]

Thanks Amir. This is one of my favorite categories, and it is always nice to see a competent piece at such a low price.

Sometimes I use dual inputs with independent volume controls on my audio interface to get balance just right, for example when I do rips for cartridge measurement. My other option is to use a vintage Marantz receiver with a built-in balance control, but that's not as convenient since the interface lets me run a test tone / sweep and look at it immediately in Audacity as I dial it in. The ultimate phono pre would have balance adjustment and spit out a stereo spectrogram.

 

[Angsty]

If I was looking for a phono amp today I think I'd prefer one that offers a few choices of capacitance for the MM input.
My last PS Audio PS III offered 50, 150, and 300 pf.
Surprised we see so little of that today, they also should be loaded a 47k ohms.
I guess if you don't run the audiophile baby MC your needs don't count today?

You would probably be looking at a Schiit Mani 2, then.

Schiit Mani 2 Review (Phono Stage)

This is a review and detailed measurements of the Schiit Mani 2 phono preamplifier. It was sent to me by the company and costs US $149. Naturally the unit looks like other Schiit products and seems to even have the previous Mani skin given the lack of "2" designation in the front. Fortunately...

www.audiosciencereview.com

 

[sarumbear]

The stylus introduces huge mismatch in comparison and this is the point where i would like this dealt with.

That is new information. Can you point us some reference on that?

 

[abdo123]

That is new information. Can you point us some reference on that?

Well In most installations the stylus tracks one side better than the other causing them to be louder.

 

[RigorDude]

Why do the measurements for phono amps include only a 1 kHz tone? Wouldn’t it be useful to see distortion vs. frequency?

 

[sarumbear]

Well In most installations the stylus tracks one side better than the other causing them to be louder.

But why? Maybe you send some reference to studies about the subject? I have worked as lathe operator at EMI and we had never checked the channel balance of our QC system.

 

[sergeauckland]

Well In most installations the stylus tracks one side better than the other causing them to be louder.

The stylus tracks one side better than the other due to bias, as a result of a pivoted arm. It does NOT result in one channel being louder, just that one channel can track higher modulation before mistracking. Bias compensation exists to equalise the tracking ability of the two channels, but is always a compromise setting, and one that depends on the moment-to-moment modulation drag on the stylus, so is only ever an approximate compensation. Much better than nothing, but never accurate.

Only linear tracking turntables avoid bias, although even with those, there is some drag on the stylus due to small swings due to imperfect concentricity of pretty much all records.

S.

 

[Multicore]

Thanks @amirm! Placed an order at B&H $70.11 including tax and shipping. I'll be able to play records through the MiniDSP Flex.

I think it looks cool. What's wrong with Radio Shack anyway? It was a useful shop and I'm sorry it's gone. I was going to get the Pluto if this review turned out bad but it looks too Hi-Fi for me.

What cable wiring do you prefer to connect it to the balanced analog input on the MiniDSP Flex?

 

[abdo123]

The stylus tracks one side better than the other due to bias, as a result of a pivoted arm. It does NOT result in one channel being louder, just that one channel can track higher modulation before mistracking. Bias compensation exists to equalise the tracking ability of the two channels, but is always a compromise setting, and one that depends on the moment-to-moment modulation drag on the stylus, so is only ever an approximate compensation. Much better than nothing, but never accurate.

Only linear tracking turntables avoid bias, although even with those, there is some drag on the stylus due to small swings due to imperfect concentricity of pretty much all records.

S.

Thanks for the reply i have forgot the word for linear tracking turntables. I was looking for them for few minutes but was not successful.

It’s kind of weird they’re not the standard and instead they’re the premium. Doesn’t seem like the complicated thing to make, at least not in 2022.

 

[sarumbear]

The stylus tracks one side better than the other due to bias, as a result of a pivoted arm. It does NOT result in one channel being louder, just that one channel can track higher modulation before mistracking.

That’s what I knew and experienced. Hence, couldn't see a need for a balance control on a phono preamp.

 

[abdo123]

That’s what I knew and experienced. Hence, couldn't see a need for a balance control on a phono preamp.

Most styluses manufacturers (worth their name) publish channel balance specifications. I’m not completely sure how they do these measurements but it’s definitely a thing.

This value typically ranges from 1.5 db and up, so it’s audible in most cases.

 

[abdo123]

@sergeauckland if there is not a really a channel imbalance then what is the cause behind the shift the pseudocenter experiences with records?

 

[sarumbear]

Most styluses manufacturers (worth their name) publish channel balance specifications. I’m not completely sure how they do these measurements but it’s definitely a thing.

This value typically ranges from 1.5 db and up, so it’s audible in most cases.

I expect that is the manufacturing tolerance and the value will differ from unit to unit. How will you know your cartridge’s balance level and how can you then compensate such a small difference using a much wider range balance control?

Finally, why was not that a thing when we only listened to vinyl?

PS. I’m trying to learn, not rebuke.

 

[RigorDude]

Thanks for the reply i have forgot the word for linear tracking turntables. I was looking for them for few minutes but was not successful.

It’s kind of weird they’re not the standard and instead they’re the premium. Doesn’t seem like the complicated thing to make, at least not in 2022.

Turntable designer Pierre Lurné (Audiomeca) has a trenchant discussion of the engineering problems with tangential arms here: http://www.tnt-audio.com/sorgenti/lurne_air_bearing_e.html

This is the key point:

“The major error concerns the Mass Distribution and therefore the Dynamic Properties: clearly an Air Bearing arm behaves like any other arm in the vertical plane only. The head moves up and down, the tube less and the bearing stays about still. In this plane, the Effective Mass is usual, deals correctly with the cartridge compliance and the resonance frequency is kept under control.

On the other hand, the “entirety” of an Air Bearing arm moves on the horizontal plane. The Effective Mass increases a lot, up to 10 times and even more (!), as a result that another frequency of resonance is created. Things are already complicated enough with one single general resonance so close to the troubles of record eccentricity and warp that adding a second one is an open door to tracking problems. The new resonance rings very low in the worse region and far from the well known safe area (9 to 12 Hz approx). More, two working planes are affected because of the 45x45 engraving. Manufacturers consent and EVEN call the attention of the user in their manual! To keep the arm mass low enough, light cartridges and the choice of the smaller counterweight are strongly recommended.”

 

[Thomas_A]

When it comes to channel balance and channel separation, there are individual variations between cartridges of the same type. It relates both to cartridge "motor" symmetry and stylus/cantilever symmetry. The best ones I've had showed 0.25 dB imbalance at 1 khz, the poorest ones around 1.5 dB.

 

[Eldus]

This is a review and detailed measurements of the ART Precision Phono Pre. It was kindly drop shipped to me by a member and costs US $81.
View attachment 212653
The look reminds of Radio Shack equipment of 1970s! So outdated but I guess it keeps their costs down. You get variable gain which is handy together with a low cut rumble filter. Support is provided for both Moving Magnet and Moving Coil cartridges. Power is provided through a 9 volt AC transformer:
View attachment 212655

A bit of loading choice is provided in the back as well (25 vs 100 ohm).

ART Precision Phono Pre Measurements
As usual we start with our dashboard in MM mode:
View attachment 212656
This ranks the unit above average with respect to noise & distortion:

View attachment 212657

It could do better if power supply noise was kept in check more. Here is the Moving Coil performance:
View attachment 212658

Power supply noise dominates even more here.

Most important test here is RIAA equalization implementation:
View attachment 212659

There is a shelving down below 3 kHz or so but rather small. There is channel imbalance though courtesy of that gain potentiometer. Low-cut filter is doing its job but causes a bit of boost before rolling off steeply.

Next important bit is headroom so that pops and clicks don't get amplified due to amplifier clipping:
View attachment 212661

This is better than many phono stages. Finally, here is a rather new/optimized measurement of distortion alone:
View attachment 212664

Normally THD+N is dominated by noise due to high gain of these preamps. Above graph isolates just the distortion so we can keep a handle on it. It has a slope down because due to RIAA equalization, gain is increased in lower frequencies and hence rise in distortion.

Conclusions
The ART Precision Phono Pre gets the basics right at a very attractive price. Flexibility of variable gain is there but you lose some channel matching (mine was set to "0" for above tests). Not much to ask for other than a nicer looking enclosure in a future revision.

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As always, questions, comments, recommendations, etc. are welcome.

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I wonder how their Single ended to Balanced active adapter measures.

 

[sergeauckland]

@sergeauckland if there is not a really a channel imbalance then what is the cause behind the shift the pseudocenter experiences with records?

From my experience it's that not all records are mastered centre-balanced. Especially, vocalists are often ,I assume deliberately, positioned off-centre. Early stereo was notoriously left right only with nothing in the middle. A cartridge's LR imbalance will give the same imbalance on every record, so is easily distinguished from off-centre mixing or mastering.

S

 

[abdo123]

When it comes to channel balance and channel separation, there are individual variations between cartridges of the same type. It relates both to cartridge "motor" symmetry and stylus/cantilever symmetry. The best ones I've had showed 0.25 dB imbalance at 1 khz, the poorest ones around 1.5 dB.

Really? I mean most Ortofon cartridges advertise 1.5dB. How much should you be spending for 0.25 imbalance?

 

[abdo123]

From my experience it's that not all records are mastered centre-balanced. Especially, vocalists are often ,I assume deliberately, positioned off-centre. Early stereo was notoriously left right only with nothing in the middle. A cartridge's LR imbalance will give the same imbalance on every record, so is easily distinguished from off-centre mixing or mastering.

S

Another member suggested that channel imbalance is inherit in the stylus and is not a property of inevitable tracking bias (thus the channel balance specification)

Do you have anything to add to that?