The Monoprice Pure Tube Stereo Amplifier is available for the paltry sum of $359.

Monoprice Pure Tube Stereo Amplifier

Before reading any other part of this review, contemplate that first sentence again. This all-tube integrated amplifier costs less than a fancy pair of interconnects or speaker wires. And it includes a phono input. If you’re one of the young “vinylistas” for whom your turntable is your totem, this could be the amplifier for YOU!

The Monoprice Pure Tube Stereo Amplifier offers an introduction to true tube sound for a ridiculously low price. The styling is both retro and futuristic, and in that vein, includes retro inputs (phono and line-stage) and futuristic ones (Bluetooth wireless). But one does give up a few amenities like remote volume control, a headphone jack, and a thorough owners’ manual. It’s still a great bargain, but for only a bit more money, it could have been untouchable!

Highlights

Monoprice Pure Tube Stereo Amplifier

  • Striking styling
  • 10 Watts per channel is enough to drive most loudspeakers
  • Can be used as a tube preamplifier only
  • Onboard Bluetooth allows streaming from APTX devices
  • Moving-magnet phono input
  • Induced hum can be a problem unless precautions are taken
  • Miserly price makes this one of the least expensive tube integrated amps available

Monoprice Pure Tube Stereo Amplifier Side View

Introduction

As to the Monoprice Pure Tube Stereo Amplifier (henceforth the “MP”), let’s dispel the biggest misconception first: I can just hear the voices of the unwashed mob screaming “ONLY 10 WATTS?!?” Yes, it truly has only 10 watts-per-channel output. And even that is measured only at 1KHz, not 20-20kHz.

But do you REALLY need more? The average loudspeaker sold in 2020 is highly sensitive (normally from 90 to 94dB / 1W/1m). Now get out your cell phone, download a free sound pressure level app, sit in your listening chair, and start cranking up the music. Yes, that’s it – crank it up some more. Beginning to get uncomfortably loud, yes? Now you’re approaching 90-ish decibels. THAT’s the volume you get from ONE watt. More loudness increases the wattage demands very quickly, but for most listeners, the first watt alone will suffice, and the remaining nine will easily handle any unexpected crescendos.

The MP will, admittedly, not play at stadium levels. But if you’re listening at those levels, sound quality is academic anyway because you’ll soon be deaf. The MP will play loud enough for your home just fine. The occasional raucous holiday party excepted; 10 watts will get you where you need to be. Period.

So, explain to me again why you need that gazillion-watt AVR that sounds like badly wounded cats fighting?

The Monoprice Pure Tube Stereo Amplifier is built in China and sold by the ubiquitous Monoprice.com here in the USA. It seems of sturdy construction for the most part, and mine was easy to use.

MONOPRICE PURE TUBE STEREO AMPLIFIER SPECIFICATIONS
MODEL:

Pure Tube Stereo Amplifier, Product #27222

INPUTS:

Bluetooth (BT), Line-Level (Aux), & Phono-Level (Phono)

FREQUENCY RESPONSE:

20Hz – 20kHz (-2dB)

TOTAL HARMONIC DISTORTION:

1% @ 1kHz

RMS POWER OUTPUT:

10 Watts / channel (4-ohm load @ 1kHz)

OUTPUT IMPEDANCE RANGE:

4 – 8 ohms

INPUT IMPEDANCE:

47k ohms

INPUT SENSITIVITY:

450mV

SIGNAL TO NOISE RATIO:

≥ 85dB

TREBLE ADJUSTMENT RANGE:

+6dB

BASS ADJUSTMENT RANGE:

+6dB

INPUT VOLTAGE:

100-120 VAC @ 60Hz

FUSE RATINGS:

T2AL @ 125V

TUBE TYPES:

EL84 (4) & 6N3 (3)

BLUETOOTH VERSION:

4.0 with aptX audio codec

BLUETOOTH RANGE:

32ft (10m)

BLUETOOTH ID

MP TUBE 27222

DIMENSIONS:

10.7 x 5.9 x 12.4in (272 x 150 x 315mm)

WEIGHT:

16.1lbs (7.3kg)

PRICE:

$359 USD

Company:

Monoprice

SECRETS Tags:

pure tube stereo amplifier, vacuum tube, integrated amplifier, budget component, low power, Monoprice, Amplifier Review 2020

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Design & Setup

The setup of the MP is easy, but the owners’ manual contains at least one error and omits at least one important caution.

Monoprice Pure Tube Stereo Amplifier Rear View

The owners’ manual clearly states:

“The output level of the PRE-OUT jacks is unaffected by the volume knob.”

This is incorrect. On both my review sample and at least one other unit owned by an online amigo, the pre-out jacks are volume controlled. This allows the use of the MP as a standalone tube preamplifier or allows the user to drive one or more subwoofers from the pre-out jacks.

However, the volume available on the pre-out jacks may be insufficient to drive some amplifiers (mostly pro amps that need more input voltage) to full volumes. This should not impede the average user, but a potential purchaser should be aware of it.

Another important factoid not mentioned in the owners’ manual is that those pre-out jacks are full-range and that the speaker outputs are also full-range, regardless of whether subwoofer(s) are used with the main speakers. This means that there will be no way to eliminate bass frequencies from the satellite speakers (or the amplifier’s output tubes) despite having subwoofer(s) on the pre-out jacks.

The owners’ manual also clearly states:

“Do not turn on the amplifier without first connecting a pair of 4-8-ohm speakers.”

This is true insofar as it goes, but fails to address the situation where an owner wants to use the MP as a tubed preamplifier only. If the pre-out jacks are being used to drive an external power amplifier, there may not be any speakers connected to the MP’s terminals. This is a problem and could conceivably lead to damage of the MP.

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If the owner wishes to use the MP as a preamp only (and without attached speakers), then a dummy load must be connected to each pair of speaker terminals. A single 10-ohm, 10 Watt resistor (available via Amazon – you’ll need two – one for each channel) should be connected across each pair of speaker terminals (red to black for each channel) to avoid damage to the EL-84 output tubes. When speakers are reconnected to the MP, remove the dummy resistors.

The MP provides three modes of input –

  • Auxiliary (typically used with CD players, streamers, tuners or other line-level analog sources)
  • Phono (typically used with raw moving-magnet phono cartridges – no upstream RIAA equalization or line-level converters, please)
  • Bluetooth (via supplied antenna)

I used the Auxiliary and Bluetooth inputs and then loaned the MP to an audio amigo, Mr. David Sonnier, for testing with his phonograph. I was particularly satisfied with the ease of setting up the Bluetooth. With my cell phone, I was streaming in minutes.

Monoprice Pure Tube Stereo Amplifier Front View

The front panel of the MP includes a VU meter that I consider a total waste of money on this product. I would much rather have seen Monoprice include any or all of the following:

  • A remote control with volume
  • A headphone jack
  • A built-in USB DAC
  • A cutoff switch to protect the output tubes when the MP is used as a preamp only

But it is what it is. If any of these omissions is a deal-breaker for you (some are for me), then you’ll need to spend more money on another product. The VU meter, by the way, was working when I received the review amplifier but stopped working during the course of the review.

These missing features are not trivial. Since there is no remote volume control, I would normally consider this amp to be a headphone amplifier for a computer system (where the listener would be in close proximity to the amplifier’s volume knob at all times), but the amp has no headphone jack. Of course, one could manage via some adapters to connect headphones to the MP’s speaker terminals, but the MP’s output transformers are intended to drive low impedance loads (4-8 ohms). With higher impedance headphones, who knows how this would sound?

So, if you want to use this amplifier in a living room system, plan on getting up to adjust the volume knob routinely. If you’re listening to vinyl, a single adjustment at the beginning of each disc side may be sufficient, but if you’re streaming digital, different cuts often have WILDLY different volumes, meaning that you may be rushing from your listening position to the amplifier very frequently to adjust the volume. This alone, unfortunately, disqualifies the amplifier for use in many people’s listening rooms.

Monoprice Pure Tube Stereo Amplifier MCM Remote

However, there is an after-market device that might allow remote control volume for an additional $39.99. That would be the MCM Custom Audio 50-8394 Line Level Volume Control with IR Remote. Although this would work ONLY with the Aux input of the MP (or in the pre-out section if the MP was used as a preamp only), it would allow for remote volume control, and with pretty good sound. This unit is available from Amazon.

Associated Equipment Used in this Review:
  • MacBook Pro running Roon streaming software over Ethernet to
  • AURALiC Aries Ethernet streamer using the coaxial digital output to
  • Black Ice Audio FX Tube DAC (review to come) to
  • Audio-gd Vacuum XLR tube preamp
  • Audio-gd HE-1 solid-state preamp
  • MCM 50-8394 remote volume control
  • Emotiva PA-1 monoblock amplifiers
  • Heathkit 12W amplifiers
  • Ashly FTX-2001 pro power amp
  • Emotiva T2 tower loudspeakers
  • Klipsch RP600M bookshelf speakers
  • Klipsch Cornwall IV speakers
  • Emotiva Airmotiv S-15 subwoofers
  • Emotiva / Audioquest / Afford-HiFi interconnects
  • Carnare speaker wire (bi-wire configuration)
In Use

My equipment rack has a wide variety of transformers and badly tangled wires behind it. When the single-ended RCA interconnects on the inputs of the Monoprice Pure Tube Stereo Amplifier come anywhere close to this rat’s nest of transformers and wires, induced hum becomes audible at the speakers. So, we’ll have hum, hum, hum till her daddy takes the tube amp away! (With apologies to the Beach Boys).

Careful dressing of interconnects will eliminate most of the hum, but even then, and with the shortest possible cable lengths, a slight bit of hum seems likely. With most speakers, this will be inaudible, but with ultra-high sensitivity models like the Klipsch Cornwall IVs, you may have to work with amplifier placement to avoid audible hum.

Monoprice Pure Tube Stereo Amplifier Front Angle

The MP also sports bass and treble controls with a full 12-decibel range (plus and minus 6dB for both bass and treble). On most systems, I’m a fan of tone controls, but on this particular amplifier, I sincerely believe the tone controls may cause more problems than they fix. The treble controls are probably benign since most users don’t add much boost or cut. But the bass control has the potential to be really problematic. If any significant bass boost is applied, the amp’s 10-watt power capacity will be quickly exceeded causing audible clipping.

Despite this, the tube output stage of the MP is far less likely to cause speaker damage than any solid-state amplifier in similar clipping mode. Solid-state clipping can quickly fry tweeters. But it is still a good idea to use the bass boost of the MP in very small doses (no more than plus 1 or 1.5dB) and to avoid cranking up the volume significantly while the bass is boosted.

And so… How does the Monoprice Pure Tube Stereo Amplifier sound?

In the treble, it’s just slightly rolled-off but not too blurred – very much like a traditional tube amplifier (think Dynaco Stereo 70, for example). For many of today’s speakers, this will not be an impediment, but a blessing. The forgiving treble will also make many an otherwise harsh piece of music more listenable. It will also hide a multitude of Bluetooth sins, and make wireless streaming a more pleasurable experience. It does not sound as extended in high-frequency response as many contemporary tube amplifiers, but again – this can often be complementary to many sources.

In the midrange, the MP amplifier comes into its own! Yes, the MP is slightly warm and sweet and yes, it may also slightly exaggerate spatial and imaging clues in the music, but overall, the effects are most positive. If you’ve never heard a tube component before, this would be an ideal one to try. If you like the tube effects, you can move up, and if not, you haven’t really wasted your money.

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In the bass, the MP amplifier is less than tight and tends to slightly blur bass lines. If you’re a rock music fan, you may never even notice these issues (after all, I’m comparing this modestly priced amplifier against a reference system where cost was of little concern). But if you listen to classical or jazz music, the bass may be more troublesome for you. Because of its output transformer, the MP has a relatively low damping factor (meaning that it may not control the woofer cones as tightly as would a solid-state amplifier that lacks the output coupling transformer).

Now if I’ve given the impression that I don’t like the sound of the Monoprice Pure Tube Stereo Amplifier, I apologize. Despite its sonic shortcomings detailed above, the sound can be captivating, entrancing, and exciting. This will be more so with some program materials than others, but at its best, the MP sounds like a FAR more expensive amplifier! The MP can sound like real music where many (most?) other (solid-state) amplifiers in its price range fall far, far short. This amp will easily trounce many AV receivers that I’ve heard.

Phono Input Impressions of the Monoprice Pure Tube Stereo Amplifier by David Sonnier

Since my review system is totally digital, I loaned the MP to an audio amigo for testing of its phono input. The following comments are generously provided by Mr. David Sonnier who tested the review unit with his vinyl system):

Monoprice Pure Tube Stereo Amplifier With Turntable

This amplifier can drive the Klipsch RF62ii speakers with ease and sounds good while doing it. The bass on M’Boom really hits hard. I’m amazed at how little power one needs to have great sound. The Monoprice Pure Tube Stereo Amplifier is a nice-sounding little integrated amp. I’m blown away at how powerful 10wpc can sound, especially through floor-standing speakers.

Brubeck Time

The Dave Brubeck Quartet “Brubeck Time”

I’m playing an old mono LP from 1955 called “Brubeck Time,” an original pressing – and it sounds NICE!

Gaucho

Steely Dan “Gaucho”

Steely Dan’s “Gaucho” sounds awesome through this amplifier.

Etcetera

Wayne Shorter “Etcetera”

Wayne Shorter’s tremendous sounding jazz LP from Blue Note, “Etcetera” (Blue Note 80th anniversary Tone Poet reissue series) brings on the details. Horns sound fantastic through this amplifier, and it sounds nice at low volumes too.

A remote would be nice, but at times I felt like I was right there with the band, surrounded by musicians. This amplifier was also auditioned with the Pro-Ject Tube Box phono stage (through the AUX input). The Tube Box sounds better than the built-in phono preamp in the Monoprice, but for the money, it should!

Monoprice Pure Tube Stereo Amplifier Aux and Bluetooth Inputs Review by Glenn Young

The Demon Diaries

Parov Stelar “The Demon Diaries”

“The Demon Diaries” by Parov Stelar is a bit of a disappointment compared to the band’s live performances on YouTube, but still offers an interesting mix of brass and synth. I do wish that the band would offer their YouTube performances in Blu-ray or 4K video with at least CD-quality audio. I’d buy those discs! But I digress…

Even listening at somewhat louder than normal volumes, the MP handled this material with aplomb. I’d expected to hear some clipping in the bass, but no – the 10 watts of the MP was enough to rock the room when playing my tower speakers full-range.

Monoprice Pure Tube Stereo Amplifier With Speakers

Out of curiosity, I did hook up subwoofers to the pre-out jacks of the MP for part of this two-disc set, and everything worked perfectly. The MP played my speakers through its speaker terminals, and the subs kept up through the pre-out jacks. Wonderful!

Basket of Light

The Pentangle “Basket of Light”

Next up was the Pentangle’s classic live album “Basket of Light,” streamed through the Bluetooth antenna of the MP. The string bass can be wooly on this album, but the voices should be lovely. The harmonies and vocal rounds used by the Pentangle have never sounded better in my system than with this amp. A couple of previous equipment configurations have tied the performance of this amplifier for midrange beauty and imaging, but none has startlingly exceeded the MP’s performance.

When we (again) consider its modest $359 list price, I don’t see how any other product could possibly match the value for the money it exhibits. What a bargain!

Conclusions

The MONOPRICE PURE TUBE STEREO AMPLIFIER offers unique and amazing value for its modest price. Despite its lack of a remote, it is HIGHLY recommended!

Likes
  • Sweet and dimensional midrange
  • Built-in phono section
  • Bluetooth streaming with easy setup
  • Compact and stylish appearance
  • Tone controls included
Would Like To See
  • Remote volume control
  • Headphone jack
  • More restricted range of boost for the bass tone control
  • Switch to disable output tubes when the unit is used as a preamp only
  • More thorough and accurate owners’ manual

For the tube-curious and those on entry-level budgets, I know of NO other all-tube integrated amplifier for anywhere NEAR the bargain price of the Monoprice Pure Tube Stereo Amplifier. If you’re willing to live within its 10-watt limitations, and particularly if you’re a “vinylista” who needs a phono stage, I don’t think you can do better (in an all-tube design) than this amplifier.

Besides, if you decide that you need more power later, you can still use the MP as a tubed preamplifier (with Bluetooth and Phono Stage), and use the pre-out jacks to drive the power amplifier of your choice. Put the MCM 50-8394 remote volume control between the pre-out jacks of the MP and the power amplifier of your choice, and you now get all the benefits plus remote volume control as well!