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Pro-Ject Tube Box S2

Vacuum tube phono preamplifier for moving magnet and moving coil cartridges

Item # 252TBBXS2B

This beauty offers the warm, natural, expansive sound that vacuum tube preamps are famous for.

This beauty offers the warm, natural, expansive sound that vacuum tube preamps are famous for.

Item # 252TBBXS2B

Ships free

On backorder

Expected: 8/4/2023


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About the Pro-Ject Tube Box S2

Eric A.

Warm vacuum-tube sound for your beloved vinyl

The Pro-Ject Tube Box S2 offers the warm, natural, expansive sound that vacuum tube preamps are famous for. Not coincidentally, that's exactly the sound I want when I listen to my favorite records. And tube preamps like this one are excellent at eliminating unwanted noise, so you hear only the music.

Warm vacuum-tube sound for your beloved vinyl

The Pro-Ject Tube Box S2 offers the warm, natural, expansive sound that vacuum tube preamps are famous for. Not coincidentally, that's exactly the sound I want when I listen to my favorite records. And tube preamps like this one are excellent at eliminating unwanted noise, so you hear only the music.

This versatile preamp features adjustable input capacitance settings for moving magnet and high-output moving coil cartridges, plus gain-setting options to better match your cartridge to your system. A switchable subsonic filter protects your amplifier and speakers from power-wasting low-frequency rumble below 20 Hz.


Product highlights:

  • dual-mono design using two dual-triode ECC83 (12AX7A) vacuum tubes for optimal channel separation
  • compatible with moving magnet and moving coil phono cartridges
  • front-panel selectable amplifier gain (40, 43, 50, 53, 60 or 63dB)
  • adjustable input capacitance and impedance via dip switches on bottom of unit
    • impedance settings: 10, 100, 1k, 2k ohms
    • fixed 47k ohm input impedance setting for high-output MC cartridges
    • capacitance settings: 147, 267, 367, 487, 587 pF
  • subsonic filter reduces low-frequency rumble and wasted amplifier power (-18dB/octave at 20 Hz)
  • audiophile-grade polypropylene capacitors
  • aluminum/metal sandwich chassis for improved shielding from vibration and electromagnetic interference
  • gold-plated RCA stereo input and output pairs
  • RIAA response accuracy: 0.4dB (20-20,000 Hz)
  • THD: less than 0.05%
  • 5-3/16"W x 4-11/16"H x 4-1/16"D
  • weight: 14.4 oz.
  • warranty: 2 years
  • Our 60-day money-back guarantee
  • MFR # 9120071658588

What's in the box:

  • Tube phono-preamplifier (2 tubes installed)
  • AC power adapter (attached 4' DC cord)
  • 3 AC plug inserts (US/EU/UK)
  • Instructions For Use

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Pro-Ject Tube Box S2 reviews

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More details on the Pro-Ject Tube Box S2

Stacey B.

Features & specs

Cartridge Type MM, MC
Subsonic Filter Yes
Cartridge Loading Selectable
Adjustable Resistance Load Yes
Adjustable Capacitance Load Yes
Vacuum Tube Yes
RCA Inputs 1 Pair
XLR Inputs No
RCA Output 1 Pair
XLR Output No
USB Output No
3.5mm Output No
Optical Output No
Coaxial Output No
Signal-to-noise Ratio (MM) 80
Signal-to-noise Ratio (MC) 80
The Pro-Ject Tube Box S2 replaces these items:

Product Research


Tube Phono Preamplifier: The Pro-Ject Tube Box S2 is high-quality tube preamplifier that features a fully discrete circuit design without using any operational amplifiers (OpAmps). The Tube Box S2 includes two replaceable tubes (ECC83) for tube rolling and sound-shaping. This gives the customer many options to pick from and alter the sound signature to his or her preference. It also features precise RIAA equalization, ultra-low noise circuitry, and dual-mono circuitry for optimized channel separation. The Tube Box S2 will give a full and relaxed laid back sound with lush mids, just like you would expect it from a much bigger high-end tube phono pre-amplifier.

MM & MC Cartridge Support:  The Tube Box S2 offers support for both MM and MC cartridges and comes with a variety of settings for your type of turntable and catridge.

  • Input Gain: Input Gain can be adjusted to 40dB, 43dB 50dB, 60dB, or 63dB for MM or MC cartridges. The Input Gain buttons are located on the front-panel
  • Input Capacitance: Input Capacitance can set to 147pF, 267pF, 367pF, 487pF, and 587pF for MM cartridges. There is also a 47pF setting for high-output MC cartridges. Input Capacitance can be configured using the dip-switches on the bottom of the unit.
  • Input Impedance (for MM only): Input Impedance can be set to 10Ω, 100Ω, 470Ω, 1000Ω, or 2000Ω for MM cartridges only. Input Impedance can be configured using the dip-switches on the bottom of the unit.

Subsonic Filter: The Subsonic filter helps to reduce low-frequency rumble and wasted amplifier power. The Subsonic filter button is located on the front-panel.

Gold-Plated RCA Connections: The Pro-Ject Tube Box S2 is equipped with a pair of gold-plated RCA connections for the output stage and input stage. The gold-plated RCA connectors offer corrosion-free signal transfer.

Power Requirements: The Pro-Ject Tube Box S2 tube phono preamplifier operates off of standard household current using the included external power supply. The outboard power supply helps reduce noise and interference.

  • Input: 100-240V~50/60Hz, 0.6A
  • Output: 18V AC, 1.0A.

Aluminum/Metal Casing: The Pro-Ject Tube Box S2's aluminum/metal casing protects against vibrations and electromagnetic interferences for superior sound.

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Customer Q&A

7 questions already asked

If I run this through a vintage solid state amplifier (HK 730 Twin) will I be defeating the benefit of the tube sound?
[ JEFF  Jan 29, 2023 ]
1 answer
Absolutely not, Jeffery. Using the fantastic Pro-Ject Tube Box S2 can fatten up the sound of your vinyl with any amplifier combo!
[ Bo  Jan 29, 2023 ]  Staff
I just hooked it up and there is a really bad fast low end pulse. Also, the tube on the right is red and the left is orange. ???
[ JIM  Dec 22, 2022 ]
1 answer
I do apologize for that frustration Jim, but we can help! If you are having any issues with items purchased from us, please call our Technical Support team at 1-888-292-2575 and we can try to help. That lifetime support is baked into every purchase from Crutchfield.
[ Bo  Dec 22, 2022 ]  Staff
I've had this preamp for 4 days and have had it turned on the entire time. Records have been played maybe 50 times and I would like to know how long these rebranded EH tubes are going to open up? The sound is muddy with no top end.
[ Duane  Mar 12, 2022 ]
4 answers
My two cents - I ditched the included tubes and replaced with two Genalex Gold Lions. Way better sound for both top and bottom end, even after minimal opening up time.
[ JUSTIN  Mar 18, 2022 ]
I think you may have something either set up wrong or it may be defective. I had to return one. Call Crutchfield their tech guys are great and can help with the set up and troubleshoot. You may have the switches wrong. Hope this helps. You may also make sure that your turntable doesn't have a built in preamp that you have to turn off. Usually switch is below the platter. Same with your receiver, if you have it plugged into the phono input try the aux or CD.
[ LARRY  Mar 14, 2022 ]
Hi, mine sounded really good at initial set up. Maybe the preamp isn't set correctly for the cart you are running?
[ CHRIS  Mar 14, 2022 ]
I have no problem with mine, perhaps is that we all have different hearing
[ NORBERTO  Mar 14, 2022 ]
What make are the vacuum tubes uses in the S2 project preamp ?
[ Len  Dec 08, 2021 ]
4 answers
The tubes are Pro-Ject branded, but I have read that they may be manufactured by JJ Electronics, but I can't verify that. I swapped them out for a pair of matched pair of Genalex 12AX7 Gold Lions.
[ MICHAEL  Dec 10, 2021 ]
The tubes are a pair of standard "12AX7" type which is the common configuration for pre-amplifier and phono-stages. As to the specific brand used here, the stock tubes that came with my unit were of Russian manufacture, labeled Electro Harmonix, but I'm told by someone I know to be a "tube" expert they are essentially a reproduction of the original JJECC83 design. In today's solid-state world, new tubes like these are now being made almost exclusively in Russia or China. These have a nice overall performance, they open up especially after 30-50 hrs of use. I think most people will be very pleased with the sound. However it's easy to change out (tube roll) the stock tubes for other brands of 12AX7 if you want to experiment. Matched pairs can be purchased new or vintage NOS, but the latter option can get very expensive. Search online and you'll get the idea. I bought a matched pair of new Mullards which I really liked as they improved the midrange and bass response. I also was fortunate to obtain a pair of vintage Telefunken tubes from my expert buddy and that's what I'm currently running in this unit.
[ A  Dec 10, 2021 ]
They are ECC83 (12AX 7A) tubes marked with the project audio systems logo. 22J0 is etched into the glass opposite the logo.
[ Andrew  Dec 10, 2021 ]
They are branded Project but the design looks similar to JJ tubes. I am using the original tubes that are just breaking in at about 30 hrs use. I would try the original equipment before purchasing high end tubes as the originals have a nice warm sound with good separation.
[ KEVIN  Dec 09, 2021 ]
What settings should I use for a Sumiko Rainier cartridge?
[ Liam  Oct 24, 2021 ]
5 answers
I have the Sumiko Moonstone but the manufacturer specs on capacitance are similar to your Rainier. Your cartridge is a Moving Magnet (MM) so the only dip switches (bottom of unit) you need concern yourself with are 1-3. The Tube Box S2 comes preset with a load of 47p and Sumiko recommends a range of 100-200. I have mine set to 147p by selecting only switch 3 in the "on" position and switch 1 & 2 in the "off" position. While this seems to be in the middle the suggested range, bear in mind that your phono cable interconnect also adds to this number. Usually between 50-80 p, depending on the length and construction of your cable. Without a meter it's hard to know exactly how much but I have a Pro-Ject cable and I'm happy with the load set at 147p. As for the gain setting, that is a bit more a matter of preference. If you want to go down the rabbit-hole on the internet, there are formulas to calculate the "ideal" setting based on the cartridge output specs and the sensitivity of your amp inputs. I've done that and the number generally comes back just above 50 dB. I have mine set generally at 53 dB with a good result. Occasionally when listening to some albums that were cut "hot" (many of my 80's collection) I'll adjust that down to 50 dB. The good news is that you can adjust this on-the-fly, while listening to the music, and with some trial and error you'll find what sounds best to you. You can also give your unit at least 50 hrs of playtime and then re-evaluate as, the tubes do break in a little and the sonic signature changes a bit (for the better).
[ A  Oct 31, 2021 ]
47k ohms/220 pF
[ KEVIN  Oct 28, 2021 ]
Set the third dip switch (100pF) to on. All other dip switches should be off. Set the gain to 43.
[ JOSE E  Oct 28, 2021 ]
Not familiar with the Rainier cartridge. Mini is a blue 2, and is set with all switches off except 7 on.
[ NORBERTO  Oct 28, 2021 ]
Dip switches: 3on, the rest off.
[ RONALD  Oct 28, 2021 ]
What does this do that my receiver doesn't do?
[ SCOT  Apr 05, 2021 ]
4 answers
I assume you are using the phono input on your receiver or your TT has an amplifier option. Either way these are both less than quality preamp. With the Tube box you also dial it in with the brand cartridge you are using. I've had mine for some time now and totally happy with it. Thorens TD160 TT Emotiva. XPA Gen 3 amp. N A D c 165BEE pre (now a Hegel H390) Bryston A2 speakers Power conditioner and upgraded wires
[ GUY  Apr 06, 2021 ]
It amplifies sound through vacuum tubes. My vinyl never sounded so good. I did have to plug it in to the auxiliary input on my receiver because the phono input has a built-in pre-amp.
[ BENJAMIN  Apr 06, 2021 ]
Has adjustability for all phono cartridges, provides a cleaner signal and some tube sound warmth
[ SCOTT  Apr 05, 2021 ]
Depends on your receiver, but most built-in preamps on receivers and turntables are the bare minimum when it comes to delivering optimal sound from your vinyl. With this you are able to set it up specifically for the stylus you're using so you're tailoring it to your turntable. You also get more power and warmer tones through the tube amp. It seems like something like this wouldn't make much of a difference, but it was night and day for me after installing this. I would say though if your turntable is subpar, you should use the money to invest in a premium turntable before adding other accessories like this.
[ DONALD  Apr 05, 2021 ]

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Pro-Ject Tube Box DS2
Vacuum tube phono preamplifier for moving magnet and moving coil cartridges
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Upgraded performance and connectivity

The Pro-Ject Tube Box DS2 offers these features:
  • RIAA response accuracy: 0.2dB (20-20,000 Hz)
  • THD: less than 0.04%
  • two sets of gold-plated RCA connectors for connecting two turntables
  • pre-mounted Cool Dampers lower distortion and increase tube life span
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