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Review and Measurements of Monoprice Hybrid Tube Amp

amirm

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#1
This is a review and detailed measurements of the Monoprice Hybrid Tube Power and Headphone Amplifier. It is on kind loan from a member who sent it to Monoprice to be fixed twice. It costs US $199 from Monoprice direct. I can't find it on Amazon but there is a "Rockville" amp that looks identical and it goes for even less at US $149.

When I first reached for this amplifier, I thought it was a high-end, $1000 headphone tube amp or something. Imagine by shock that it turned out to only cost $199 or even lower per above. They have nailed all the signature bling of a much more expensive amplifier:

Monoprice Stereo Hybrid Tube Amplifier Audio Review.jpg

In person it looks even better than it does in above picture (available light late at night). We have a rather heavy unit, with fine feeling volume control, VU meter and those signature rings around the tubes. Heck, it even came with plastic covering the plastic/wood looking sides! I don't understand the economics of these things at all. Do they grow them in dirt and dig them and ship them? Can't imagine anyone building these from scratch yet selling them thousands of miles away for so little money.

The one usability I didn't like is lack of detent for the tone controls at 0 dB. I sort of eyeballed it in the middle.

The power button has a nice sold feel, belying the cost of this unit.

I won't cover the rest of the unit (including its Bluetooth functionality) here and will post a review from Z that explains it all.

Here is the back panel in case you are interested:

Monoprice Stereo Hybrid Tube Amplifier Back Panel Audio Review.jpg

Let's get into the measurements and see how it performs.

Audio Measurements
I didn't test the bluetooth functionality leaving me with standard RCA input which is labeled as CD. This is our dashboard with 2 volt input and power adjusted to be 5 watts using 4 ohm load:

Monoprice Stereo Hybrid Tube Amplifier Dashboard.png


Where to start.... First there is all that hum and power supply noise. I tried grounding the input to it and while that reduced the 60 Hz hum, it made the rest of the spectrum worse so I left it alone. Still, that is not the worst of our problems. That lies in very high levels of harmonic distortion. And no, it is not a "tube distortion of 2nd harmonic." It is distortion at all harmonics! THD+N and hence SINAD puts it in dismal category and at the bottom of the list:

Best Audio Amplifier Reviewed 2019.png


After creating these two slides I went back to my measurement software, only to notice things had gotten worse:

Monoprice Stereo Hybrid Tube Amplifier Dashboard after warm up.png


One channel was clipping on and off, bringing the THD+N to whopping 10%. It is asynchronously clipping. I captured and created the above slides and went back to the measurement software only to see this now:

Monoprice Stereo Hybrid Tube Amplifier Dashboard after warm up +1 minute.png


Now both channels are busted! Can you spell garbage? I knew you could....

Humoring ourselves, and bringing every bit of motivation, I continued the testing with frequency response:

Monoprice Stereo Hybrid Tube Amplifier Frequency Response Audio Measurements.png


Good thing I am not the type to bang his head against the wall or I would have a concussion about now. I get that there is tone control but the channels don't match either.

The owner wanted to know about noise. Z review says the hum is there on power on. This is what I measured it half-way through testing:
Monoprice Stereo Hybrid Tube Amplifier Idle Noise.png


And SNR:
Monoprice Stereo Hybrid Tube Amplifier SNR Audio Measurements.png


The amplifier is advertised as having 50 watts of power. But the owner told me it is 25 watts which is much closer to the truth:

Monoprice Stereo Hybrid Tube Amplifier Power into 4 Ohm Audio Measurements.png


We are getting 1% distortion at 20 watts.

Intermodulation distortion picture is not pretty:
Monoprice Stereo Hybrid Tube Amplifier IMD Audio Measurements.png


Conclusions
The monoprice hybrid tube amplifier nails the looks and aesthetics. The mechanical engineer and material procurement people deserve an A. The electronics designer know, gets a failing grade if he though this is a hi-fi product. Poor guy though was likely told to build this for nothing.

Congratulations are in order then for Monoprice to have produced probably the most faulty, and poorly measuring audio product I have tested to date. This would be good as a conversation piece on your desk and that is about it.

NOT recommended.

------------
As always, questions, comments, recommendations, etc. are welcome.

Good news: the pink panther strike is over! So my favorite model is back to posing business as you see in the review picture. I like to take the whole gang out for dinner (steak and lobster) to celebrate. Please help fund that by donating generously using:

Patreon: https://www.patreon.com/audiosciencereview), or
upgrading your membership here though Paypal (https://audiosciencereview.com/foru...eview-and-measurements.2164/page-3#post-59054).
 

daftcombo

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Feb 5, 2019
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#3
Hi Amir,
Splendid unit! :)
Any chance to have you make a little listening test?
Because the subjectivers can still reject your conclusions you know!
 

mickeyd123

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Feb 25, 2019
Messages
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#6
Thanks Amir — this has been the most entertaining review so far :D:facepalm:
This is a review and detailed measurements of the Monoprice Hybrid Tube Power and Headphone Amplifier. It is on kind loan from a member who sent it to Monoprice to be fixed twice. It costs US $199 from Monoprice direct. I can't find it on Amazon but there is a "Rockville" amp that looks identical and it goes for even less at US $149.

When I first reached for this amplifier, I thought it was a high-end, $1000 headphone tube amp or something. Imagine by shock that it turned out to only cost $199 or even lower per above. They have nailed all the signature bling of a much more expensive amplifier:


In person it looks even better than it does in above picture (available light late at night). We have a rather heavy unit, with fine feeling volume control, VU meter and those signature rings around the tubes. Heck, it even came with plastic covering the plastic/wood looking sides! I don't understand the economics of these things at all. Do they grow them in dirt and dig them and ship them? Can't imagine anyone building these from scratch yet selling them thousands of miles away for so little money.

The one usability I didn't like is lack of detent for the tone controls at 0 dB. I sort of eyeballed it in the middle.

The power button has a nice sold feel, belying the cost of this unit.

I won't cover the rest of the unit (including its Bluetooth functionality) here and will post a review from Z that explains it all.

Here is the back panel in case you are interested:


Let's get into the measurements and see how it performs.

Audio Measurements
I didn't test the bluetooth functionality leaving me with standard RCA input which is labeled as CD. This is our dashboard with 2 volt input and power adjusted to be 5 watts using 4 ohm load:

View attachment 25966

Where to start.... First there is all that hum and power supply noise. I tried grounding the input to it and while that reduced the 60 Hz hum, it made the rest of the spectrum worse so I left it alone. Still, that is not the worst of our problems. That lies in very high levels of harmonic distortion. And no, it is not a "tube distortion of 2nd harmonic." It is distortion at all harmonics! THD+N and hence SINAD puts it in dismal category and at the bottom of the list:

View attachment 25967

After creating these two slides I went back to my measurement software, only to notice things had gotten worse:

View attachment 25968

One channel was clipping on and off, bringing the THD+N to whopping 10%. It is asynchronously clipping. I captured and created the above slides and went back to the measurement software only to see this now:

View attachment 25969

Now both channels are busted! Can you spell garbage? I knew you could....

Humoring ourselves, and bringing every bit of motivation, I continued the testing with frequency response:

View attachment 25970

Good thing I am not the type to bang his head against the wall or I would have a concussion about now. I get that there is tone control but the channels don't match either.

The owner wanted to know about noise. Z review says the hum is there on power on. This is what I measured it half-way through testing:
View attachment 25971

And SNR:
View attachment 25972

The amplifier is advertised as having 50 watts of power. But the owner told me it is 25 watts which is much closer to the truth:

View attachment 25973

We are getting 1% distortion at 20 watts.

Intermodulation distortion picture is not pretty:
View attachment 25974

Conclusions
The monoprice hybrid tube amplifier nails the looks and aesthetics. The mechanical engineer and material procurement people deserve an A. The electronics designer know, gets a failing grade if he though this is a hi-fi product. Poor guy though was likely told to build this for nothing.

Congratulations are in order then for Monoprice to have produced probably the most faulty, and poorly measuring audio product I have tested to date. This would be good as a conversation piece on your desk and that is about it.

NOT recommended.

------------
As always, questions, comments, recommendations, etc. are welcome.

Good news: the pink panther strike is over! So my favorite model is back to posing business as you see in the review picture. I like to take the whole gang out for dinner (steak and lobster) to celebrate. Please help fund that by donating generously using:

Patreon: https://www.patreon.com/audiosciencereview), or
upgrading your membership here though Paypal (https://audiosciencereview.com/foru...eview-and-measurements.2164/page-3#post-59054).
I supplied the unit, it is the 25 watt version and cost me $99 on sale. The hum drove me crazy and this is the second return under their warranty, so luterally this is the 3rd unit. I did not open this one but sent it unopened to Amir, hoping that we got lucky on the third try. It is indeed beautiful lit up in a dark room as audio sculpture/furniture, just don't listen to music. I told Amir to keep it, as it is not worth paying to ship it. Thanks for the review, hope it saves others the hassle.
 

mickeyd123

Member
Patreon Donor
Joined
Feb 25, 2019
Messages
33
Likes
45
#10
Someon
This is a review and detailed measurements of the Monoprice Hybrid Tube Power and Headphone Amplifier. It is on kind loan from a member who sent it to Monoprice to be fixed twice. It costs US $199 from Monoprice direct. I can't find it on Amazon but there is a "Rockville" amp that looks identical and it goes for even less at US $149.

When I first reached for this amplifier, I thought it was a high-end, $1000 headphone tube amp or something. Imagine by shock that it turned out to only cost $199 or even lower per above. They have nailed all the signature bling of a much more expensive amplifier:


In person it looks even better than it does in above picture (available light late at night). We have a rather heavy unit, with fine feeling volume control, VU meter and those signature rings around the tubes. Heck, it even came with plastic covering the plastic/wood looking sides! I don't understand the economics of these things at all. Do they grow them in dirt and dig them and ship them? Can't imagine anyone building these from scratch yet selling them thousands of miles away for so little money.

The one usability I didn't like is lack of detent for the tone controls at 0 dB. I sort of eyeballed it in the middle.

The power button has a nice sold feel, belying the cost of this unit.

I won't cover the rest of the unit (including its Bluetooth functionality) here and will post a review from Z that explains it all.

Here is the back panel in case you are interested:


Let's get into the measurements and see how it performs.

Audio Measurements
I didn't test the bluetooth functionality leaving me with standard RCA input which is labeled as CD. This is our dashboard with 2 volt input and power adjusted to be 5 watts using 4 ohm load:

View attachment 25966

Where to start.... First there is all that hum and power supply noise. I tried grounding the input to it and while that reduced the 60 Hz hum, it made the rest of the spectrum worse so I left it alone. Still, that is not the worst of our problems. That lies in very high levels of harmonic distortion. And no, it is not a "tube distortion of 2nd harmonic." It is distortion at all harmonics! THD+N and hence SINAD puts it in dismal category and at the bottom of the list:

View attachment 25967

After creating these two slides I went back to my measurement software, only to notice things had gotten worse:

View attachment 25968

One channel was clipping on and off, bringing the THD+N to whopping 10%. It is asynchronously clipping. I captured and created the above slides and went back to the measurement software only to see this now:

View attachment 25969

Now both channels are busted! Can you spell garbage? I knew you could....

Humoring ourselves, and bringing every bit of motivation, I continued the testing with frequency response:

View attachment 25970

Good thing I am not the type to bang his head against the wall or I would have a concussion about now. I get that there is tone control but the channels don't match either.

The owner wanted to know about noise. Z review says the hum is there on power on. This is what I measured it half-way through testing:
View attachment 25971

And SNR:
View attachment 25972

The amplifier is advertised as having 50 watts of power. But the owner told me it is 25 watts which is much closer to the truth:

View attachment 25973

We are getting 1% distortion at 20 watts.

Intermodulation distortion picture is not pretty:
View attachment 25974

Conclusions
The monoprice hybrid tube amplifier nails the looks and aesthetics. The mechanical engineer and material procurement people deserve an A. The electronics designer know, gets a failing grade if he though this is a hi-fi product. Poor guy though was likely told to build this for nothing.

Congratulations are in order then for Monoprice to have produced probably the most faulty, and poorly measuring audio product I have tested to date. This would be good as a conversation piece on your desk and that is about it.

NOT recommended.

------------
As always, questions, comments, recommendations, etc. are welcome.

Good news: the pink panther strike is over! So my favorite model is back to posing business as you see in the review picture. I like to take the whole gang out for dinner (steak and lobster) to celebrate. Please help fund that by donating generously using:

Patreon: https://www.patreon.com/audiosciencereview), or
upgrading your membership here though Paypal (https://audiosciencereview.com/foru...eview-and-measurements.2164/page-3#post-59054).
Sound quality- the two units I returned had audible hum even before headphones were plugged in, and distortion during headphone listening. I did not connect any speakers but no reason to think it would have been better.
 

Timbo2

Senior Member
Joined
Feb 27, 2018
Messages
332
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205
Location
USA
#17
What's the tube complement? For the package alone, for someone like me this might be worth buying and fixing the circuit.
Funny I was going to suggest the same thing!

Wow, that thing is broken.
 

SIY

Technical Expert
Technical Expert
Joined
Apr 6, 2018
Messages
3,267
Likes
6,062
Location
Phoenix, AZ
#18
Wow, that thing is broken.
If my guess is correct, the fixes are pretty easy. I dropped a note to Amir about sending it to me.
 
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