Pro-Ject's Tube Box S2 MM/MC Phono Preamp Beats the Built In

Pro-Ject Audio Systems is undoubtedly the king of budget friendly, entry-level, high performance analog components. A definite go-to for sub $1000 turntables and bang for your buck phono preamps. Founded in 1991 by Heinz Lichtenegger during the evil reign of the CD, they fought their way to vinyl success and made it!

Overview & Build Quality

The Tube Box S2 is Pro-Ject’s first product to offer a fully discrete, no OpAmp circuit design. It’s also their first product to come with replaceable tubes for achieving optimal system synergy. It accepts the input from both MM and MC cartridges with gain settings on the front panel (adjustable via pushbuttons) of 40, 43, 50, 53, 60, and 63dB. Five variable input impedance settings are available to adjust to any MC cartridge while the 47k ohm input impedance setting is fixed and suited for MM and high output MC cartridges.

Engaging the subsonic filter (also available via front panel pushbutton produces less low frequency rumble, but it also takes from a lot of the energy in the music resulting in an emotionally “flat” sound. Pro-Ject lists the filter as 20Hz with a slope of 18dB/octave however, the “20Hz” part confuses me because the filter doesn’t sound like it starts to drop at 20Hz. In fact, it sounds like it drops off at around 30-35Hz.

The chassis is made of metal with a matte sandpaper feel while the faceplate is made of brushed aluminum that is only visible as brushed when the lighting is near perfect. The S2 is available in black or silver finishes, which judging by the pictures, doesn’t seem to change its overall understated appearance. The build quality is decent for its retail price of $399 but its “liveliness” leaves a bit to be desired. It rings. Not like sheet metal, but still. This can easily be fixed with Audio Additives’ 3M Damping Sheets (placement at your discretion) but some folks may be opposed to sticking something of that nature on their equipment. (more modifications later on) It boasts two ECC83 tubes, dual mono circuitry, “ultra-low noise circuitry with an FET input stage”, and polystyrene capacitors, which Pro-Ject says are used where possible.


Using an Ortofon 2m Red with a recommended load resistance and load capacitance of 47k ohms and 150 - 300pF, I found the dip switches located on the bottom of the unit were already set to accommodate my cartridge. While not technically a “plug and play” design, Pro-Ject’s easy set-up certainly did make it feel that way. In the manual they even provide recommended settings for a few Ortofon cartridges, which I thought was nice: customers can avoid having to search the deepest depths of the internet for their cartridges’ recommended settings. Seeing that tubes come pre-installed, that’s pretty much all there is to set up the S2. Rather boring if you ask me.

First Impressions

When I first sat down to listen and compare the S2 to my Denon AVR-2802’s built-in phono preamp, I was expecting to be floored by this little box’s performance. After all, I had every right to be! I had been weighed down by this system bottleneck for a very long time and it was finally time to listen to a real phono stage. I was excited! Instead, what I heard was a bit anticlimactic. There was a noticeable difference, but certainly not enough to impress me. There was a little better bass, maybe a bit more defined detail (not harsh), a little wider soundstage presentation—though not an added sense of space—and most noticeably, a cleaner, more balanced timbral presence.

But still, these differences were almost miniscule, and something was lacking. Only a few things could be done: send it back, write a bad review, or let it settle in with the system and give it another chance. Well I certainly wasn’t going to just reject a review offer just because of a weak product, and I didn’t want to write a bad review, I just had to hope this whole thing worked out. So, after a few weeks of constantly leaving the S2 on 24/7 and occasionally playing records for background music, I decided judgement day had come...


Dire Straits’ Six Blade Knife (BSK-3266)
Giving the cueing lever on my Pro-Ject Debut Carbon a quick flick and crossing my fingers while running over to my listening chair, I waited… I didn’t know what to expect! Would my expectations be fulfilled, or would I hear what I heard on day one?

Well… actually neither. There was a far greater difference than before, yet still subtle. I started to feel disappointed in the retail price of this unit. At $399, what a waste! I decided to keep listening because I like Dire Straits and the song was relaxing me. Once I calmed down halfway through the song and actually tried listening, I noticed something. Something well… subtle. I started to notice these tiny nuances to which I had never before really paid attention. Almost like adding a pinch of spice to your food only to realize the flavor that had been missing all along.

Knopfler’s Fender seemed to have this percussive bite every time he dug into the strings, yet his tone was so sweet and lush. The expansive reverb started to produce an image I could almost see with my mind’s eye. The image specificity produced as big an improvement as the portrayal of the reverb’s decay. This gave the guitar as well as Knopfler’s voice much better spatial placement and solidity on the soundstage, which made for very involving listening.

Stephane Grappelli / David Grisman Live- Satin Doll (BSK-3550)
This is one of those tracks that can sound thin at times when the mains power is bad or a system’s synergy is off. It relies on the tonal accuracy of a system to sound the way it should. Tiny Moore’s electric mandolin was reproduced here with a rich, snappy tone that was decorated with subtle nuances that made the instrument sound and feel more real. It had a warm, weighty feeling that gave Tiny’s mandolin a lot more emotional expression compared to the Denon’s presentation. The instrumental separation was slightly more defined whereas the Denon kind of mashed everything together, producing what sounded like blobs of image-starved sound. The woody texture of Stephane’s violin and David’s mandolin stood out, giving them a lively, palpable feeling. This extra level of texture really shouldn't be mistaken for an overemphasis on detail, or as additive grain. Instead, the violin was notably smoother than through the Denon, particularly the higher notes. All of this made the Denon by comparison sound grainy and dull.

Herbie Hancock’s Dedication- Maiden Voyage & Cantaloupe Island (GET51282-LP)
This is a “get on down” reissue I bought on Record Store Day in 2019. The first side of the record contains two tracks of Herbie playing acoustic piano solos that if you are even the slightest bit tired will knock you out cold. On the second side he plays more upbeat and chaotic on electric pianos and synthesizers that somehow can still put you into a trance.

Maiden Voyage: Herbie’s piano sounded warm, inviting and timbrally rich. Soft, yet percussive, it flowed together perfectly with incredible sustain and life. I really could feel the emotion pouring through my system and out of my speakers like I have never before felt. “Yes!” I thought. “This is what analog really sounds like!” I have heard videos on YouTube of people playing their records through very nice equipment with good A/D conversion, and while very impressive sounding, the digital conversion mixed with YouTube’s compression and limited frequency range detracts from the presence and weight that with vinyl you can almost feel more than hear. Strange, right? Again, through the S2 there was a slight increase in depth and dimensionality compared to the Denon. Imaging was better, bass was cleaner, the S2 just is a better preamp.

Cantaloupe Island: An ARP Odyssey synth without any reverb or effects was the first instrument through the speakers. Cleaner, more defined—and dare I say with deeper bass—and texture that somehow seemed to make my subwoofer better get along with my speakers and room.

As Herbie’s Fender Rhodes e-piano entered, the wider soundstage kind of tossed the piano around the room as it oscillated between both channels. As Herbie’s ARP PE-IV String Ensemble faded in, the value having a slight increase in depth became clear: the sound was larger and a little more expansive. One downside: the S2’s improved detail retrievel revealed the audible distortion produced by the Debut Carbon’s rather short 8.6” tonearm.

Unable to Check Out the MC Section

I don't have a low output MC cartridge so I was unable to check out the MC section. However I figure most $399 phono preamp buyers will be using it with a MM cartridge. Perhaps when they get an MC they'll be using it "in a pinch" until they can afford a more costly higher performance model, though without hearing it perhaps I'm selling short the S2's MC performance. Maybe I'll try to get a low output MC to review!


New Tubes: Whether you want to buy brand new or NOS, tube rolling is definitely the way to go if you want to fine tune to your specific tastes your system’s synergy.

Audio Additives’ 3M Damping Sheets: these sheets create a damping effect that reduces chassis vibration and greatly reducing resonances, thus improving sound quality and lowering your equipment’s noise floor. It’s a stainless-steel adhesive sheet backed by a “blue proprietary 3M damping material”. They are extremely inexpensive, and unless tapping on your equipment feels like tapping on a tank, every piece of your system should have these installed.

An aftermarket linear PSU: Let’s face it, to keep the cost down to an attractive $399 The Tube Box S2 comes with a crappy class D wall wart power supply. Less than perfect rectification and filtering can create peaks, spikes and ripples in the output (which when powering low voltage DC equipment we all know is never a good thing).

A moderately wide selection of quality PSUs are available on Ebay that utilize toroid transformers with your choice of output voltages. These are certain to give you even clearer treble and quite possibly better dynamics. Some listings even have two PSUs in one chassis meaning you could choose a voltage for your phono stage and your turntable. Be sure to DOUBLE CHECK THE RATED VOLTAGES ON YOUR EQUIPMENT before buying these. The S2 runs on 18V DC. (AnalogPlanet will not be held responsible for any damage to your equipment resulting from this suggestion, but we will happily take credit for any sonic improvement).


So, my experience with this phono stage has been a pretty good one. Albeit subtle, it sounds fantastic and was a step up (no pun intended) from the solid state phono preamp built into my Denon receiver.

Is Pro-Ject’s Tube Box S2 the best preamp out there for the money? I can’t say for sure. I haven’t heard all of the competition, or frankly any of it! I’m new at this. However, considering that this is the first preamp comparison I have done in my system that I know and love I thought the Tube Box S2 performed well. Certainly if you’re an analog “newbie” and looking for your first phono preamp, both the price and sound are right. Watch for more content to come from me in the future!

Associated Equipment
Cartridge: Ortofon 2m Red
Phonostage(s): Pro-Ject Tube Box S2, Denon AVR-2802
Amplifier: Pioneer A-717
Subwoofer: Paradigm PS-1000
Speakers: JBL ARC1000
Speaker/Interconnects/Power Cables: Generic


mraudio's picture

...Caleb Attaway? It that Malachi's imaginary friend? :-)

Michael Fremer's picture
Has previously contributed to analogPlanet. He is a real person.
mraudio's picture

...find one other review by Caleb. I must have missed it, but it was last July.

Meet our newest reviewer, 17 year old Caleb Attaway. Caleb lives northwest of Atlanta, Georgia and is going into his senior year of high school at Living Science Home Studies, Inc., which is half home school and half private school. In the future Caleb will review records and new audio gear.

Ortofan's picture

... dispelled all doubt about the cutoff frequency and slope of the subsonic filter.

How did the sound quality of the Tube Box S2 compare to that of the phono stage built into the Pioneer A-717 integrated amp?

mraudio's picture

...he used the phono stage in his Denon AVR-2802, according to the review copy?

cattaway07's picture

I really should have compared it to the A-717. That amplifier was loaned to me when I compared the S2 and the Denon. I sadly don’t have it anymore but there is a chance I could get it back. If so, I certainly will do a comparison between the S2 -if I still have it- and the A-717’s phonostage. I may be able to do a follow up about the comparison in another review or all alone. This is not certain though. I will see what I can do.

latinaudio's picture

I used to be one of the MD at "El Sistema" where I worked with talented boys and girls who were learning to be musicians. Nothing has been more rewarded in my life than watching the transformation of a child into a brilliant new performer after a few years. Malachi and Caleb Attaway truly are on the same way under your guidance and support. Go ahead and thanks for trying to incorporate new voices in a really small niche as our hobby...

Michael Fremer's picture
The most rewarding part of the job at this point!
Haverchuck's picture

I've had the Pro-Ject Tube Box for a few years now &, for the most part, love it. Your mention of the 3M damping material got me interested in trying it out on my preamp to see how much of a difference it makes. I can't find much info on audio equipment damping online that isn't car-related, so I'm interested in knowing how you'd suggest applying it. Is a strip on the bottom of the preamp enough to damp vibration, or should I actually open it up & place a strip on the inside top of the casing as suggested on the Audio Additives site? What would you recommend for my other gear (receiver, speakers, turntable, etc.)?

teagan85's picture

A poor quality class D wall wart power supply is included with the Tube Box S2. Inadequate rectification and filtering can cause the output to have peaks, spikes, and ripples. In getaway shootout' a game that celebrates absurdity and offers an unparalleled multiplayer experience, discover the sheer delight of uncontrolled rivalry.

stevejobb's picture

The Pro-Ject sound system is really stable, cheap and quality. The first product mentioned is Tube Box S2 capybara clicker