This is a review and detailed measurements of the Project Polaris Headphone Amplifier. It is on kind loan from a member. Researching it, I was surprised that it is the brainchild of the member, @solderdude!
From what I understand a US outfit makes these either as kits or finished products. I received the latter:
There are a myriad of jumpers to set gain, bandwidth, output impedance, LED status, etc. I tested the combination of first two.
The design goals seem to be around very high output level but with "tube like" distortion profile (and output impedance if wanted).
Headphone Amplifier Audio Measurements
Let's see our dashboard view with 2 volts in, 2 volts out:
That is fair bit of distortion but is second harmonic dominated as tubes are said to be.
Was dismayed to see almost 1 dB of channel imbalance. Testing for that shows fairly large discrepancy at low volume levels:
Signal to noise ratio was surprisingly good at full volume:
But not so good with just 50 millivolt output:
Intermodulation distortion versus output level shows a ruler flat incline in distortion which I assume is on purpose:
Frequency response shows that the two lower settings are made for people who want rolled off highs:
Since even the medium setting rolls off at 20 kHz, for my testing I chose the high bandwidth mode. It made very little difference in other measurements anyway.
Here is the all important THD+N versus power at 300 ohm:
There is fantastic amount of power available despite the high impedance at whopping 720 milliwatts! This should enable the polaris to drive high impedance headphones with ease. In this regard it reminds me of tube amps with their unusually high output voltages. Unlike them though, plenty of output power is available at much lower impedance of 33 ohm:
I did my testing at the lowest setting of the output impedance:
So quite good and able to drive even low impedance headphones without varying them. There are two other settings to more emulate the tube amp high output impedances.
Listening Tests
With both my Sennheiser HD650 and DROP + MRSPEAKERS ETHER CX headphones, the Polaris amplifier was able to get scary loud even in low gain mode. There is ample power available to create a very high dynamic range. I don't have time to perform careful AB tests. In casual listening, the audible distortion was not obvious especially at low to reasonable levels. At much higher output power I thought the highs got grungy but this may be placebo.
Conclusions
The Project Polaris Headphone Amplifier appears to build a tube amp without any of their weakness of tube aging, low power in low impedances, high heat and power consumption. On all of those, it wins. So if you are itching to have a tube-like amplifier, the Polaris makes a much better substitute in my opinion. It won't replace my low distortion amplifiers so I can't give a person recommendation.
------------
As always, questions, comments, recommendations, etc. are welcome.
This is my second review today. There is just so much gear here to review that I am having to work overtime (going from 2 hours to 4). So I hope I get some overtime money from you all by donating using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
From what I understand a US outfit makes these either as kits or finished products. I received the latter:
There are a myriad of jumpers to set gain, bandwidth, output impedance, LED status, etc. I tested the combination of first two.
The design goals seem to be around very high output level but with "tube like" distortion profile (and output impedance if wanted).
Headphone Amplifier Audio Measurements
Let's see our dashboard view with 2 volts in, 2 volts out:
That is fair bit of distortion but is second harmonic dominated as tubes are said to be.
Was dismayed to see almost 1 dB of channel imbalance. Testing for that shows fairly large discrepancy at low volume levels:
Signal to noise ratio was surprisingly good at full volume:
But not so good with just 50 millivolt output:
Intermodulation distortion versus output level shows a ruler flat incline in distortion which I assume is on purpose:
Frequency response shows that the two lower settings are made for people who want rolled off highs:
Since even the medium setting rolls off at 20 kHz, for my testing I chose the high bandwidth mode. It made very little difference in other measurements anyway.
Here is the all important THD+N versus power at 300 ohm:
There is fantastic amount of power available despite the high impedance at whopping 720 milliwatts! This should enable the polaris to drive high impedance headphones with ease. In this regard it reminds me of tube amps with their unusually high output voltages. Unlike them though, plenty of output power is available at much lower impedance of 33 ohm:
I did my testing at the lowest setting of the output impedance:
So quite good and able to drive even low impedance headphones without varying them. There are two other settings to more emulate the tube amp high output impedances.
Listening Tests
With both my Sennheiser HD650 and DROP + MRSPEAKERS ETHER CX headphones, the Polaris amplifier was able to get scary loud even in low gain mode. There is ample power available to create a very high dynamic range. I don't have time to perform careful AB tests. In casual listening, the audible distortion was not obvious especially at low to reasonable levels. At much higher output power I thought the highs got grungy but this may be placebo.
Conclusions
The Project Polaris Headphone Amplifier appears to build a tube amp without any of their weakness of tube aging, low power in low impedances, high heat and power consumption. On all of those, it wins. So if you are itching to have a tube-like amplifier, the Polaris makes a much better substitute in my opinion. It won't replace my low distortion amplifiers so I can't give a person recommendation.
------------
As always, questions, comments, recommendations, etc. are welcome.
This is my second review today. There is just so much gear here to review that I am having to work overtime (going from 2 hours to 4). So I hope I get some overtime money from you all by donating using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/