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Pro-ject Optical Box E Review (Phono Stage)

amirm

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#1
This is a review and detailed measurements of the Pro-ject Optical Box E phono preamplifier. It is on kind loan from a member and I think costs US $199.

There is not much to look at or control from the front panel:

Pro-ject Optical Box E Review.jpg


The back panel shows what is different and special about this phono stage:

Pro-ject Optical Box E Review back panel digital.jpg


See it? It has a Toslink optical digital output. This means it has an analog to digital built-in. Sadly only optical output is available which would be hard to find on a computer. A much better solution would have been USB. There is also no way to change the gain so you are limited to Moving Magnet cartridges only.

A switch is provided to turn off the RIAA equalization and gain and turn the device into a normal audio interface. I did not test this mode.

Pro-ject Optical Box E Phono Measurements
Let's start with our standard dashboard outputting 5 millivolt signal to emulate a moving magnet cartridge:

Pro-ject Optical Box E Phono Measurements Analog.png


Lack of distortion is very nice. Sadly I could not get rid of the power supply noise no matter how much I tried. This penalized one channel more than the other resulting in an average SINAD:

best phono stage.png


I was excited to test the optical output as I figured this has the potential to reduce noise until I saw the measurements:

Pro-ject Optical Box E Phono Measurements Toslink Digital.png


What a shame. Look at that high second harmonic and a bit of third while leaving as much power supply noise as before. It is strange to have so much distortion despite the signal being so weak (-15 dB below reference).

Frequency response wasn't bad but not good either with some error in both digital and analog output modes:
Pro-ject Optical Box E Phono Measurements Frequency Response Digital Toslink.png


There are two sample rate modes: 48 kHz as shown above and 96 kHz. The latter was a hair worse so I stuck with 48 kHz.

Input saturation occurs earlier than I like which may magnify the effect of pops and ticks from the LP:

Pro-ject Optical Box E Phono Measurements Analog THD+N vs Level.png


Saturation gets worse as frequencies increase:

Pro-ject Optical Box E Phono Measurements Analog THD+N vs Frequency vs Level.png


Sweeping at lower output level shows two problematic peaks and performance that is not a whole lot better than their tube amp:
Pro-ject Optical Box E Phono Measurements Analog THD+N vs Frequency.png


Putting aside noise and just measuring distortion with analog output, performance is very good:

Pro-ject Optical Box E Phono Measurements Analog THD.png


Conclusions
We can buy phono preamps for pretty cheap these days so the Box E lives or dies by its digital output capability in exchange for its higher price. Sadly it doesn't deliver on that promise. So while not really broken, I can't recommend the Project Optical Box E. They could have done better.

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RayDunzl

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#2
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#3
Looks like the cheaper Schiit Mani is a better choice unless of course someone got a very specific need for the digital outputs. It's a bit strange they didn't go all the way and added a USB interface.

Anyway, while the performance isn't that impressive, I'd still like to see a turntable/cartridge setup that can get anywhere near these THD+N figures while playing a record. The best I've ever measured was something like 0.4% THD in the lower midrange/upper bass from a test record, once you go higher in frequency the distortion typically rises to 5-10% at 10-20kHz.
 
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martijn86

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#5
Bought that a year ago, expecting to connect it to a DAC. Pure waste of money. Without measurements but only by ear, I decided I do not want to ear that.

Now I use a Cambridge Audio Duo and an L30.

The story behind is: buy something reviewed in ASR.
What was the idea behind going from ADC to DAC? Did you use a DSP in between?
 

renaudrenaud

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#6
What was the idea behind going from ADC to DAC? Did you use a DSP in between?
The idea was to limit the number of boxes.

I was happy with the DAC directly to the amp and hoped with that little box to be able to listen to the turntable just with one more box.

Sadly, it's just an horror.
 
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#8
Looks like the cheaper Schiit Mani is a better choice unless of course someone got a very specific need for the digital outputs.
I almost got the Mani but I saw that U-Turn came out with a Pluto 2 with solid updates, been working great. I use a MM cartridge. They added "higher gain, active filtering, and an overhauled power supply," which amir had noted was an issue in his review of the Pluto 1.

U-Turn Pluto 2 ($99) Measurements:
  • Input impedance: 47 kΩ
  • Input capacitance: 100 pF
  • Gain: 40 dB @ 1 kHz
  • THD+N: < 0.005% (A-weighted)
  • S/N ratio: 90 dB (A-weighted)
  • RIAA accuracy: ± 0.3 dB (20 Hz - 20 kHz)
  • Crosstalk: -89 dB (20 Hz - 20 kHz)
If my math is correct, SINAD comes out to 84.54 with the A-weighted measurements, up from ~80 measured by amir for the Pluto 1

Schiit Mani ($149) Measurements:
  • Input Impedance: Selectable 47 ohms (typical for MC cartridges) or 47k ohms (typical for MM cartridges)
  • Gain 1 = L, Gain 2 = H (Standard MM Mode)
  • Gain: 42dB
  • THD: <0.008%, A-weighted, at 1V RMS
  • SNR: >82dB, A-weighted, inputs shorted
  • RIAA Accuracy: +/- 0.2dB, 20-20kHz
  • Crosstalk: -75dB, 20-20kHz
  • Sensitivity: 2.3mV for 300mV output
  • Overload Margin: >20dB
SINAD here ~79 I believe, measured to be 74 by amir
 

Phorize

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#9
That’s a shame. I’m not sure how big the market would be for a sensibly priced and featured phono stage with a transparent analogue and adc output, but I’m surprised that project didn’t accomplish this.
 

anon2k2

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#10
The unit that Amir tested is the one I got for my second system. It seemed like a good idea, as it would allow me to directly drive amps from a DAC even with a turntable attached.

In the end, when I got it I could tell even without measurement that it was different from my other phone preamps, and I guessed that the RIAA equalization was off by a bit. Subtle but basically instruments playing notes from about middle C and up just sounded a bit louder than I was used to on recordings I knew well.

Overall, it's going back into my second system because I like the simplicity. It was cool to get it measured though. Thanks, Amir.
 

renaudrenaud

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#11
The unit that Amir tested is the one I got for my second system. It seemed like a good idea, as it would allow me to directly drive amps from a DAC even with a turntable attached.

In the end, when I got it I could tell even without measurement that it was different from my other phone preamps, and I guessed that the RIAA equalization was off by a bit. Subtle but basically instruments playing notes from about middle C and up just sounded a bit louder than I was used to on recordings I knew well.

Overall, it's going back into my second system because I like the simplicity. It was cool to get it measured though. Thanks, Amir.
More or less the same goal, but I am unable to listen to that, even directly form the analog output.
 

phoenixsong

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#12
I noticed this a while back because of its simplicity, but the company's published specs of it seemed lacklustre and I nearly forgot about it since then. Maybe something like the RS2 will perform better
 

Soniclife

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#13
It has a Toslink optical digital output. This means it has an analog to digital built-in. Sadly only optical output is available which would be hard to find on a computer. A much better solution would have been USB.
USB is only better if you are archiving your vinyl, for simply playing it in real time USB is next to useless, the world needs a good simple device like this for an interesting number of systems that are digital input only. Vinyl is the most common analogue format, so it makes sense to be in the phono stage, people with more analogue formats than just vinyl should have a proper preamp.
 
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#15
I almost got the Mani but I saw that U-Turn came out with a Pluto 2 with solid updates, been working great. I use a MM cartridge. They added "higher gain, active filtering, and an overhauled power supply," which amir had noted was an issue in his review of the Pluto 1.

U-Turn Pluto 2 ($99) Measurements:
  • Input impedance: 47 kΩ
  • Input capacitance: 100 pF
  • Gain: 40 dB @ 1 kHz
  • THD+N: < 0.005% (A-weighted)
  • S/N ratio: 90 dB (A-weighted)
  • RIAA accuracy: ± 0.3 dB (20 Hz - 20 kHz)
  • Crosstalk: -89 dB (20 Hz - 20 kHz)
If my math is correct, SINAD comes out to 84.54 with the A-weighted measurements, up from ~80 measured by amir for the Pluto 1

Schiit Mani ($149) Measurements:
  • Input Impedance: Selectable 47 ohms (typical for MC cartridges) or 47k ohms (typical for MM cartridges)
  • Gain 1 = L, Gain 2 = H (Standard MM Mode)
  • Gain: 42dB
  • THD: <0.008%, A-weighted, at 1V RMS
  • SNR: >82dB, A-weighted, inputs shorted
  • RIAA Accuracy: +/- 0.2dB, 20-20kHz
  • Crosstalk: -75dB, 20-20kHz
  • Sensitivity: 2.3mV for 300mV output
  • Overload Margin: >20dB
SINAD here ~79 I believe, measured to be 74 by amir
The U-Turn Pluto 2 looks like good value at $99, I hope Amir gets a chance to do a set of measurements on it in the near future. However I'd say the 100pF input capacitance is a bit high, it will make some cartridges sound bright with a rise of a few dB in the high frequencies and also the 9V power supply is a bit low with 40dB gain, that means it will start clipping probably around 25mV/1kHz input, limiting the headroom to just ~14dB with a 5mV output cartridge.

Also I believe the SINAD for the Schiit Mani was measured to be 81dB, it's part of the comparison chart in the review for this phono pre-amp.
 
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#16
The U-Turn Pluto 2 looks like good value at $99, I hope Amir gets a chance to do a set of measurements on it in the near future. However I'd say the 100pF input capacitance is a bit high, it will make some cartridges sound bright with a rise of a few dB in the high frequencies and also the 9V power supply is a bit low with 40dB gain, that means it will start clipping probably around 25mV/1kHz input, limiting the headroom to just ~14dB with a 5mV output cartridge.

Also I believe the SINAD for the Schiit Mani was measured to be 81dB, it's part of the comparison chart in the review for this phono pre-amp.
Oops, you're right, I was looking at the SINAD in the review before the gain was tweaked. Good analysis on the rest of the specs on the Pluto as well. I'm not so familiar with the ones you mentioned, if you don't mind helping, what does the headroom work out to for the Mani on a 5V cartridge? Enough to make it the better purchase?

EDIT: Just e-mailed Schiit support asking for the input capacitance for the Mani since its not listed on the specs. They said it's 100pF.
 
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#17
I got this a few months back and finally installed it last week. Quite bad ground buzz on left channel, much improved by running some copper wire from the unit’s ground to the metal case of a Behringer A800. It’s okay then. Needed easy way to connect turntable to digital input of Oppo BDP-105, used as pre-pro. I rarely play my vinyl, almost entirely from my teen years, so it does the job without too much faff. The LPs probably sound better than on the Sony music centre I used to play them on back in the day.
 

AudioSceptic

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#19
USB is only better if you are archiving your vinyl, for simply playing it in real time USB is next to useless, the world needs a good simple device like this for an interesting number of systems that are digital input only. Vinyl is the most common analogue format, so it makes sense to be in the phono stage, people with more analogue formats than just vinyl should have a proper preamp.
Many Macs, such as my 2012 MacBook Pro, have a combined analogue/Toslink audio input, so the Optical Box E would be suitable in this case. There is also the Record Box E, which has ADC and USB output, and also caters for MC <https://www.project-audio.com/en/product/record-box-e/>. For more money, the AD Box S2 Phono offers the same functions with (supposedly) better performance and nicer case <https://www.project-audio.com/en/product/ad-box-s2-phono/>.

I've said it before, but Pro-Ject makes too many similar products with small variations in facilities.
 

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