Pro-Ject Phono Box DC MM/MC Phono Preamp Review

[DSJR]

You're no fun! ;-)

(You mean that it used to???)

It didn't seem to matter back then, but I was so naive as to business practises. I never worked on commission, so that pressure wasn't there either. In recent times though, seeing once respected and still respected brands increasing prices way over inflation horrifies me.

Fortunately for us in the UK, there's a still healthy used-gear market which has mostly replaced the middle arena, so much as I look in here, trying to gauge performance and so on, I doubt I'll ever buy much if any new gear ever again, even at trade prices.

 

[DSJR]

Not sure, but I doubt it. Mind you, 'splashy' is only a word. If I had to use more, I would add, 'smeary', 'blurry' or 'grainy'. Every time a cymbal would hit, you would hear that the sound was not as a pure shimmering cymbal should sound. There was no sibilance. I ended up getting a Cambridge Solo which offered smooth extended cymbal hits (maybe too smooth).

The Youtube author of the link above has other vids, one of them being of a Linn LP12/Ittok arm and Goldring based Adikt cartridge. There is the most horrendous distortion on rhc sibilance (dirty/damaged stylus and the Ittok's bias-correction/anti-skate is always too low for fancy tips, but this is far worse than that. That £664 AT/Spartan 15 combo (added 95ML stylus) shouldn't be as good

Is that kind of distortion what you meant?

 

[Ken Tajalli]

20mV input at 15kHz causes clip, that is ridiculously low!
A cartridge output is mainly at higher frequencies, and that's where the headamp needs the headroom.
Michael Fidler Spartan 5 (£150) quote 420mV @ 10kHz as opposed to about 27mV that this device can take.
Headroom is vital is headamps.

 

[AudioSceptic]

20mV input at 15kHz causes clip, that is ridiculously low!
A cartridge output is mainly at higher frequencies, and that's where the headamp needs the headroom.
Michael Fidler Spartan 5 (£150) quote 420mV @ 10kHz as opposed to about 27mV that this device can take.
Headroom is vital is headamps.

We can know the cartridge output at a standard velocity, so we can estimate the max voltage produced. <https://pspatialaudio.com/max_velo.htm>. Does the Pro-Ject have enough headroom for *any* MM cart?

 

[amirm]

Good for the price of course. But I would not like the mains frequency hum which is relatively high in the spectrum picture. Not sure whether this is induced by the test wiring? Maybe Amir could comment this?

In some cases the noise is due to product design and no matter what i do with grounding, it remains. I usually note that in the measurement. In other cases, it seems entirely sensitive to how I ground the unit. That was the case here and what you see is the best I could achieve. Your situation will naturally be different and hence the reason I don't penalize the device for it.

 

[Ken Tajalli]

In some cases the noise is due to product design and no matter what i do with grounding, it remains. I usually note that in the measurement. In other cases, it seems entirely sensitive to how I ground the unit. That was the case here and what you see is the best I could achieve. Your situation will naturally be different and hence the reason I don't penalize the device for it.

And once you connect the unit up to an actual arm, with its internal wiring, connected to cartridge, with its pickup coils, interconnects . . .. the situation gets worse!
I wonder why they did not go full balanced mode, in the seventies and beyond! I mean, all they needed was just one extra wire and balanced input stage. They spent thousands and thousands on bearings, extra mass, exotic materials, blah blah, but did not address the one obvious sore thumb.
What am I missing?

 

[Putter]

For the less well versed among us (like myself) what would a high pass filter do for this unit? Prevent unwanted rumble?

Having had a ported speaker (Epicure 11) with a TT back in the 1970's with the 'dancing cones', I wonder if the CD player played a role in the acceptance of bass reflex speakers with its lack feedback rumble.

 

[restorer-john]

I wonder why they did not go full balanced mode, in the seventies and beyond! I mean, all they needed was just one extra wire and balanced input stage.

The turntables, their wiring, the isolation of the outers of the RCAs, no chassis connections and twice the amount of front end active devices in the RIAA stages. Many cartridges also had cold connections to the cartridge body.

 

[restorer-john]

In some cases the noise is due to product design and no matter what i do with grounding, it remains. I usually note that in the measurement. In other cases, it seems entirely sensitive to how I ground the unit. That was the case here and what you see is the best I could achieve. Your situation will naturally be different and hence the reason I don't penalize the device for it.

There's clearly some SMPS noise (16kHz) from the plugpack (I see it's a 100-240V SMPS) and likely some form of capacitive coupling (X cap) to the "cold" from the primary side. I reckon most of that noise and mains spur would disappear with a proper power supply.

 

[rongon]

For readers who can solder and install a circuit board into a small enclosure...
Infrasonic filter project that you could add to the PhonoBox:

Project 99 - Infrasonic Filter

ESP Audio Projects - Subsonic/ infrasonic (rumble) filter. Get rid of massive cone excursions at extremely low frequencies. Suitable for phono preamps and subwoofers, PA systems, etc.

sound-au.com

 

[Doodski]

For readers who can solder and install a circuit board into a small enclosure...
Infrasonic filter project that you could add to the PhonoBox:

Project 99 - Infrasonic Filter

ESP Audio Projects - Subsonic/ infrasonic (rumble) filter. Get rid of massive cone excursions at extremely low frequencies. Suitable for phono preamps and subwoofers, PA systems, etc.

sound-au.com

Thanks I was wondering how a infrasonic filter could be made and this example answers my question(s).

 

[DSJR]

And once you connect the unit up to an actual arm, with its internal wiring, connected to cartridge, with its pickup coils, interconnects . . .. the situation gets worse!
I wonder why they did not go full balanced mode, in the seventies and beyond! I mean, all they needed was just one extra wire and balanced input stage. They spent thousands and thousands on bearings, extra mass, exotic materials, blah blah, but did not address the one obvious sore thumb.
What am I missing?

Most tonearms had five wires. Four for the signal and a fifth to 'ground' the arm-tube, this usually linked to the turntable chassis and carried out to the amp in a separate wire.. I think it was customer ignorance and general 'industry-intertia' that prevented a proper balanced situation happening. Since I estimate that over 95% of domestic sound rigs are single ended with RCA connectors (balanced was deemed unnecessary), no point in adding to the potential confusion.

 

[Ken Tajalli]

Most tonearms had five wires. Four for the signal and a fifth to 'ground' the arm-tube, this usually linked to the turntable chassis and carried out to the amp in a separate wire.. I think it was customer ignorance and general 'industry-intertia' that prevented a proper balanced situation happening. Since I estimate that over 95% of domestic sound rigs are single ended with RCA connectors (balanced was deemed unnecessary), no point in adding to the potential confusion.

Bar microphones and cartridges, single ended is just fine, if one takes reasonable care.
It is those mV and uV that require it only.
God knows how many of those turntables , also used the outer connection of the RCA point as ground too!
At any rate, the extra ground wire did help, but could have used a proper balanced cable all the way to an amp with balanced input, hell they were commonplace for microphones.
I suppose they thought with all that surface noise, distortion etc. who cares about a little hum'n'buzz!
But seriously, people and manufacturers poured a lot of money into so many aspects of the chain, and ignore the elephant in the room! even the high end ones.

 

[AudioSceptic]

And once you connect the unit up to an actual arm, with its internal wiring, connected to cartridge, with its pickup coils, interconnects . . .. the situation gets worse!
I wonder why they did not go full balanced mode, in the seventies and beyond! I mean, all they needed was just one extra wire and balanced input stage. They spent thousands and thousands on bearings, extra mass, exotic materials, blah blah, but did not address the one obvious sore thumb.
What am I missing?

How very true, especially with MC, where you have very low output requiring very high gain in the preamp, and usually very high cost in the cartridge itself (and who's going to use that in anything other than a very expensive TT and arm?).

 

[DSJR]

To be fair, I've used a few older MC active phono stages including those built in to Linn and Naim preamps of old and never had *hum* issues... Hiss yes (Naims used to be terribly hissy on the MC and old 'K' boards) - and an ARC SP14, which many 'enthusiasts' plugged their low output Koetsu's directly into, was unbearably noisy if used that way. Didn't stop the recommendations for such use though.

Thing is, using a gear rack with turntable on top can and could have a cummulative hum effect from all the gear perched underneath...

 

[Balle Clorin]

Nice piece.
What's the moving coil input impedance?
Nick

Why don’t you look it up yourself?should be easy to find when you know the the manufacturer , the manufacturer has a web page , the link to the manual is here and google exists …. And it is given in post 2

 

[welwynnick]

Why don’t you look it up yourself?should be easy to find when you know the the manufacturer , the manufacturer has a web page , the link to the manual is here and google exists …. And it is given in post 2

I was wondering if Amir had measured it, rather than taking the manufacturer's spec (which is the point of the review) and in any case post 2 was a holding post when I replied.

 

[Balle Clorin]

I see. Measuring input and output impedance is not part of the ASR measurement test as far as I can see , you may find such data in Stereophile measurements.

 

[Rottmannash]

Is the term "headamp" synonymous with phono pre amp?

 

[welwynnick]

Is the term "headamp" synonymous with phono pre amp?

Yes