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:
The back panel shows what is different and special about this phono stage:
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:
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:
I was excited to test the optical output as I figured this has the potential to reduce noise until I saw the measurements:
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:
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:
Saturation gets worse as frequencies increase:
Sweeping at lower output level shows two problematic peaks and performance that is not a whole lot better than their tube amp:
Putting aside noise and just measuring distortion with analog output, performance is very good:
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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As always, questions, comments, recommendations, etc. are welcome.
Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
There is not much to look at or control from the front panel:
The back panel shows what is different and special about this phono stage:
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:
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:
I was excited to test the optical output as I figured this has the potential to reduce noise until I saw the measurements:
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:
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:
Saturation gets worse as frequencies increase:
Sweeping at lower output level shows two problematic peaks and performance that is not a whole lot better than their tube amp:
Putting aside noise and just measuring distortion with analog output, performance is very good:
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.
------------
As always, questions, comments, recommendations, etc. are welcome.
Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/