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Pro-Ject Tube Box S2 Review

A few months ago I bought my first ever tube phono preamp to use with my turntables.

The Pro-Ject Tube Box S2.

And I thought it was time to give it an honest review.


The Pro-Ject Tube Box S2 combines drama and engagement with warmth and smoothness. A versatile and fantastic sounding preamp perfect for those that are looking for a good tube phono preamp that doesn’t cost two months of hard-earned salary.


  • Warm and smooth sound
  • Great punch and details
  • Drama and enjoyment
  • Versatile
  • Feels very well built


  • Doesn’t look that great
  • A pricy preamp for the casual vinyl spinner


  • Tubes: 2 x ECC83 (12AX 7A)
  • Supports MM and MC
  • Adjustable gain
  • Adjustable load
  • Subsonic filter (20Hz)
  • Available in silver or black
  • Tube rolling possible

Click here to check current price on Amazon.

The Pro-Ject Tube Box S2

The Tube Box S2 features a fully discrete circuit design (no use of op-amps) and has replaceable tubes that allow for tube rolling and sound shaping.

I have not seen the circuit schematics myself, but I have seen several audiophiles state that the tubes are used in the amplification output stage and not just for buffering.

The Tube Box S2 supports both MM and MC cartridges, has adjustable gain and many settings to adjust input impedance. So it should work great with about any system and phono cartridge out there.

Below is a quote from Stereoplay’s review of the Tube Box S2 in 2018:

Value blast! Flexible adjustable phono stage with interchangeable tubes. Doesn’t softer, but excites with a dynamic, punchy sound and great spatial representation.

Here is a review of the Tube Box S by Techmoan on YouTube. An interesting watch if you have the time.

Why I choose the Pro-Ject Tube Box S2

Prior to my purchase of the Pro-Ject Tube Box S2 I did a lot of research on affordable tube preamps and it seemed to me that the Pro-Ject Tube Box S2 more or less represented the entry point for decent tube phono preamps.

There are many cheaper tube phono preamp options available, but I didn’t find enough evidence that they were good sounding and good quality preamps. They all seemed to receive quite mixed reviews. So I ended up dismissing all the popular options I found that cost less than the Pro-Ject Tube Box S2.

There are, needles to say, much more expensive options as well. Many hardcore vinyl enthusiasts that fancy tube amplification use tube phono preamps that costs many times what I paid for the Tube Box S2. And would probably not even consider the Tube Box S2 a “real” tube phono preamp.

I wanted a tube phono preamp of decent quality, but I don’t really have the budget to throw thousands of dollar on a preamp.

The Pro-Ject Tube Box S2 stood out as the perfect balance between cost and performance for me.

And I am quite impressed with how it performs. More on that in the sections below.

I think the Tube Box S2 is a tube phono preamp of interest for many vinyl lovers that care about sound but don’t have astronomic Hi-Fi budgets. Like myself.

Cheaper Options

The other tube phono preamps I research includes the Nobsound Little Bear T7, the Bellari VP130 and the Nobsound Little Bear T11. They are popular phono preamps that are discussed a lot in the vinyl community. And they are all significantly cheaper than the Pro-Ject Tube Box S2.


The Tube Box S2 comes in a nice box that includes everything you need to use it and it unboxes perfectly. It is fully assembled at delivery so there are no need to mount the tubes or anything like that.

I guess most people buy this for the sound, not for the unboxing experience.

So I leave it with that.

Look and Feel

The Tube Box S2 looks ok but not great. It will probably not be the most eye catching component in your stereo rack.

There are more stylish looking tube preamps out there.

So it seems like the engineers at Pro-Ject haven’t put their development and manufacturing budget into making something flashy, but rather focused on performance. Which is probably a good thing.

When it comes to feel the Tube Box S2 feels solid like a rock. And heavy. I will not drop it on the floor but it feels like it could take the beating if I did.

Set Up

Before you start using the Tube Box S2, you will have to set the input impedance (loading) and adjust the gain to your desired level.

You will find the recommended loading in the specification for your cartridge. Then you have to refer to the user manual for the Tube Box S2 to set up the matching input impedance on the preamp using the switches underneath. It is quite straight forward.

For the gain settings, you should start with one of the lower settings if you use a MM cartridge and one of the higher settings if you use a low-output MC cartridge. And adjust it from there until the volume level seems right.


The solid-state preamp I have used for sound comparison is the award-winning solid state (transistor based) Rega Fono Mini A2D.

And my Rega Planar 2 turntable with a Rega Exact cartridge upgrade.

If you have read some of my other preamp related articles here on Vinyl Restart, you probably know that I am a big fan of the Rega Fono Mini A2D that has been my trusted preamp for a long time.

The Rega Fono Mini A2D is a very good solid-state preamp that costs about half the price of a Pro-Ject Tube Box S2.

So, how do the Tube Box S2 sound compared to the solid-state Rega Fono Mini A2D?

Does the Tube Box S2 make the music sound smoother and warmer?

Yes. Definitely.

The Tube Box S2 makes the music richer, more pleasant and enjoyable to listen to in my ears. And basically without any downsides. The Tube Box S2 fully match the impressive dynamics and precision of the Rega Fono Mini A2D, but adds more warmth and character.

The Rega is quite warm sounding solid-state preamp in my opinion. But the Tube Box S2 take it to the next level.

In short, the Pro-Ject Tube Box S2 does exactly what I hoped a relatively affordable tube phono preamp would do. It adds warmth and character without taking away clarity, precision, or punch in the low end.

The sound difference between two decent solid-state (transistor based) phono preamps are usually marginal, in my opinion.

A solid-state phono preamp is a quite basic circuit, and if it is of good quality, there is not much more to gain by replacing it with a different or more expensive one.

The difference between the solid-state Rega Fono Mini A2D and the Pro-Ject Tube Box S2 is, however, not marginal.

They sound quite a bit different.

The level of extra warmth and character that was added by the tubes of the Tube Box S2 honestly surprised and impressed me.


The Pro-Ject Tube Box S2 is a versatile, well-built and great sounding tube phono preamp that can give you the benefits and characteristics of tube amplifications in a much more affordable fashion than with many other audiophile rated tube phono preamps on the market.

Related Topics

Tube Preamps vs. Solid-State Preamps

A tube preamp uses vacuum tubes to increase the amplitude or power of a signal.

While a regular (solid-state) preamp use transistors and operational amplifiers to do that job.

In a tube phono preamp the circuitry needed to amplify and RIAA correct the PHONO signal is built around vacuum tubes. While this circuitry is built around transistors (or operational amplifiers) in a regular solid-state phono preamp.

Affordable tube phono preamps, like the Pro-Ject Tube Box S2, are usually hybrids. Which means that the circuitry includes both transistors and tubes.

Tube amplifiers respond differently from transistor amplifiers when signal levels approach and reach the point of clipping. In a tube amplifier, the transition from linear amplification to limiting is less abrupt than in a solid state unit, resulting in a less grating form of distortion at the onset of clipping. (Source: Wikipedia)

And this is the main reason why so many studio musicians, guitarist and home stereo enthusiast prefer tube amplification. The softer clipping that tubes provide results in a warmer and more pleasant sound character.

Another difference between the two technologies is that tube phono preamps usually work with tubes from a variety of different manufacturers. And different tubes often have quite different sound characters.

So, with a tube phono preamp you will have the option to roll tubes to change and balance the sound of your stereo. An option you won’t have with a regular solid-state phono preamp.

Not having that option may save you a lot of money over time, by the way…

If you want to read more about the pros and cons of a tube phono preamps, please visit my Pros and Cons of Tube Phono Preamps article.

Does an expensive phono preamp sound better?

As with most home audio components, more expensive usually means better.

When it comes to phono preamps, you will find very well performing solid-state preamps in the $100 to $400 price range. And in my opinion there is unnecessary to pay more than that for a solid-state phono preamp until your other stereo components are of very high quality.

When it comes to tube phono preamps, which are more complicated designs and more expensive to manufacture than solid-state phono preamps, my current opinion is that the entry point for high quality options is higher than for solid-state phono preamps. For tube phono preamps the entry-point for very well performing options seems to be in the $200 to $400 range and upwards.

You can also check out my Does an Expensive Phono Preamp Sound Better article.

Does a tube phono preamp sound better?

Tube amplification is known to add warmth, richness and smoothness to the sound. And are preferred by many vinyl enthusiasts and audiophiles for that reason.

When it comes to home audio and sound it is always an argument between better sound and different sound.

Better vs. different.

We can objectively say that tube amplification sound different. If it sounds better is more subjective.