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Vincent PHO-8 Phono Stage Review

amirm

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#1
This is a review and detailed measurements of the Vincent PHO-8 Phono stage/preamplifier. It is on kind loan from a member. The PHO-8 costs US $249 on Amazon with free shipping.

The PHO-8 comes in a two-box configuration with separate linear power supply which I did not expect to see in this price range:
Vincent Pho-8 Phono preamplifier stage Cartridge Moving Magnet Movie Coil Audio Review.jpg

The package has an elegant, albeit small, presence that you don't usually find in budget audio components.

There is only one control for moving magnet and moving coil gain setting.

The back panel is as you would expect:

Vincent Pho-8 Phono preamplifier stage Cartridge Moving Magnet Movie Coil Back Panel Connector...jpg

There is even a timed delay turn on in the phono stage with a relay activation after which the LED lights.

Everything here feels like a $500 device. That is with the exception of that likely phony "QC Passed" sticker.

Phono Stage Audio Measurements
Let's start with 5 millivolt, 1 kHz signal fed to the unit with RIAA reverse equalization in moving magnet setting:

Vincent Pho-8 Phono Cartridge Moving Magnet Audio Measurements.png


Performance is dominated by the 60 Hz mains hum which is typical of phono stages. Ignoring that, distortion is buried below noise level. We can tease it out using signal processing however:

Vincent Pho-8 Phono Cartridge Moving Magnet THD Audio Measurements.png


This is excellent and essentially distortion-less compared to the source (cartridge/LP).

Here is our dashboard using moving coil setting:

Vincent Pho-8 Phono Cartridge Moving Coil Audio Measurements.png


Don't go by SINAD as that is determined entirely by the mains hum which can be higher or lower in your system (I managed to reduce it a bit in my setting with playing with grounding).

So far so good until we get to frequency response:

Vincent Pho-8 Phono Cartridge Moving Magnet Frequency Response Audio Measurements.png


Ah, this is a shame. We have a built-in EQ with slight boost in bass and more so in high frequencies. I upped the source impedance from 20 to 600 ohm and that made it slightly worse but the variation is still there. There is also slight channel mismatch.

Clipping point and hence overload is quite high:

Vincent Pho-8 Phono Cartridge Overload Margin THD vs Level Clipping Audio Measurements.png


This is twice as high as some other phono stages I have tested.

Finally, changing the frequency and level shows no frequency dependent distortion source in audible band:
Vincent Pho-8 Phono Cartridge Moving Magnet THD vs Level vs Frequency Audio Measurements.png


You just lose some headroom but given how much you have to start with, it is not an issue.

Conclusions
The Vincent PHO-8 comes dangerously close to nailing objective measurements. Unfortunately it doesn't correctly implement RIAA equalization. Since that is critically audible, I can't look past it. Specification is for +--0.5 dB so maybe this is an outlier. But maybe there are some worse than this.

As it is, I can't recommend it but you have the data to decide if it fits your needs.

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

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amirm

amirm

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Thread Starter #3
The Cambridge Duo has a flat frequency response which makes it superior:



DJPre was also good in this regard but doesn't nearly have the same headroom. This means pops and clicks may be more audible.
 

milosz

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#5
I would love to see some S/N and distortion measurements from an actual vinyl rig playing an actual test LP.
 

Frank Dernie

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#6
The Cambridge Duo has a flat frequency response which makes it superior:



DJPre was also good in this regard but doesn't nearly have the same headroom. This means pops and clicks may be more audible.
And it has a high pass filter, essential for a record player.
An RIAA stage without one is defective and built by a company that does not understand seismic transducers :)
 

miero

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#7
Regarding the 60Hz in the measurement: Would it help to move the power supply further from the preamplifier (as far as power cable allows)?
 

Joachim Herbert

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#8
Wonder if this is sounding on purpose. More analog, you know.

The hum is due to associated equipment, I guess. Or would this be one of the rare cases for battery power?
 

sergeauckland

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#9
Although I agree that the frequency response isn't as good as it could be, it's not that bad at all. The spec is +-0.5dB, which means a variation of 1dB between the lowest and highest points of the graph. If you look at the graph, with the exception of a bit above around 18kHz, the frequency response stays within the 1dB window, just not centred on 1kHz.

Considering all the other gross errors that vinyl playback is prone to, I wouldn't be too upset about that sort of variation in frequency response, although, as I said above, it could easily be better. Noise, overload margin and distortion are all otherwise good.

S.
 

AnalogSteph

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#10
IMHO, a phono preamp review should also include information about:
  • input capacitance (not specified here but critical for MM, as the owners of misc. AT cartridges will be able to attest - resulting deviations tend to be far greater than +/-0.5 dB)
  • noise when confronted with a good approximation for cartridge impedance
For MC, splitting the last resistor in the IRIAA may be enough for a decent approximation of cartridge impedance, as they don't seem to have that much inductance. Resistance seems to vary between as low as 10-20 ohms to >100 ohms, so maybe two splits even.

For an MM simulation, however, adding maybe 450 mH worth of inductance in series (and perhaps a few more hundred ohms on top of that) would seem advisable. I think a lot of MM carts are somewhere between about 600 ohms and 1.3 kOhms DC with 440-500 mH of inductance. I'm normally using 750 ohms and 450 mH (Ortofon OMxx). Implementing such an inductance in a way that doesn't invite lots of stray magnetic fields may be another matter. (Maybe a large shorted coil all the way around, at a distance low enough to ensure low coupling? The more conventional mu metal enclosure?)

I am stressing this because real-life MM cartridge impedance tends to be well in the double-digit kOhms by 10 kHz, making input current noise rather important. An ohmic source of a few hundred ohms is never going to reveal issues in this area. People have been brave enough to make MM phonopres using the likes of LT1028 or LT1115 in the past (super low voltage noise but terrible for current noise, especially with unbalanced impedance as typical for a phonopre).
 
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anmpr1

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#11
1) There is really no excuse for gross FR errors. Even at this low end price. Unless it is deliberate--a 'voicing' to make the thing sound different.

2) No way to manipulate capacitance/impedance, but at this price you might not expect that.

3) Front panel switch for gain is nice. I've seen some units with back panel switching--ergonomically poor. Maybe the idea is that putting the switch on the back will keep someone from accidentally making the gain change when the unit is in use. I doubt many folks will be using this with a MC, but who knows?

4) There should be a rule that all stand-alone phono oriented preamps have a switchable subsonic filter.

5) For a hundred dollars you can get a Project Phono Box that has MC. If I was slumming the low end that is probably where I'd be looking.
 

sergeauckland

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#13
1) There is really no excuse for gross FR errors. Even at this low end price. Unless it is deliberate--a 'voicing' to make the thing sound different.
Yes, but with an error as small as this, i.e. less than 1dB, I can't see it being audible. I fully accept it shouldn't be there these days, but don't see it being deliberate 'voicing' when it's not likely to be audible.

S
 

Tom C

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#14
For the first set of measurements, the graph is labeled correctly (MM). But the type just above it says “moving coil.”
 
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amirm

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Thread Starter #17
Regarding the 60Hz in the measurement: Would it help to move the power supply further from the preamplifier (as far as power cable allows)?
No. With the very high gains of these preamps, it is so easy for it to create that hum.
 
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amirm

amirm

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Thread Starter #18
noise when confronted with a good approximation for cartridge impedance
Given strong presence of hum, noise measurements are not of much value.
 
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amirm

amirm

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Thread Starter #19
For the first set of measurements, the graph is labeled correctly (MM). But the type just above it says “moving coil.”
Thanks. Corrected.
 

scott wurcer

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#20
Given strong presence of hum, noise measurements are not of much value.
I have a worn AT cart soldered directly to an RCA male connector as a test input, the hum is greatly reduced.
 
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