This is a detailed comparison, Review and Measurements of Sony PHA-1 and Teac HA-P50 Portable DAC and Headphone Amplifiers. They are on kind loan from forum member. The Sony retails for $250 and seems was released back in 2013. The Teac is likewise being sold on Amazon for $200. Both have that "cool" rack-mounted style albeit in tiny packaging. Here you see them on my Keysight/Agilent bench power supply for scale:Between the two, the Sony feels more solid. On the test unit, the headphone jack on the teac is all but lose. It could barely hold the headphone jack. With owner's permission, I plan to open it up and see what is going on.Both have high/low gain. I tested only the high gain.Plug-and-play worked on Windows 10 Creators edition with no driver install for either unit. For my testing, I used ASIO4ALL virtual ASIO interface as that is the only one that my Audio Precision APx555 understands.Let's get into measurements and see how they did.As usual, we start with the dashboard view. Unlike DACs though, I could not run these at full output as the teac I think clipped pretty badly. So these are reduced levels down to what typical DAC outputs at 2 volts or so:First, Sony PHA-1:Pretty decent results although worse than Topping NX4 DSD . As an example, SINAD was 104 dB on NX4 DSD, beating the Sony by some 14 dB!Here are the Teac HA-P50 results:So a few db worse in SINAD department. More worrying though is the channel imbalance that is clearly visible in the scope output and in the RMS voltages. I should say the volume control was very loose on the teac, not inspiring confidence.Jitter test shows a pretty clean output on Sony but with quite a few modulations for the Teac:The noise floor is much higher than the Topping NX4 DSD and hence the difference in THD/SINAD scores.Let's get into all important measurement, distortion+noise versus output voltage at different loads. Here, I test from 300 ohms to 150, 100, 50 and 33 ohms:The downward sloping part of these curves means noise is dominant. The sudden sharp uptick means distortion is dominant. The corner of that graph is what I call onset of clipping and where I like to measure power.As we see, the Sony has lower noise up to about 2 volts output regardless of load. So for more sensitive headphones, that is the winner.Above 2 volts, the teac takes over with more and more output until it clipes at 3.5 volts. As usual, to compute the available power, square the voltage on the graph and divide by impedance. I have done that for the two units at 300 ohms, showing that the Teac produces 3X more power for 300 ohm headphones such as Sennheiser HD-650s.The news unfortunately on output impedance is not very rosey:The teac clocks at 33 ohms which is the highest I have ever measured! The sony is not near as bad at 10 ohms but gets schooled badly by Topping NX4 DSD at just 0.9 ohms. The higher output impedance means the frequency response of the headphone can be changed resulting in different tonal quality which you may or may not like.To show channel imbalance based on position of volume control, I run my special test where I vary the volume manually and then plot in real-time the output voltage (vertical axis on the left) and channel deviation (vertical axis on the right). Here is the Sony PHA-1:At mid-settings there is a channel drift as much as 1 dB. Oddly at the other two extremes it is not too bad. So decide what output voltage/power you listen, plot it in the red curve and then look at the blue graph for amount of error.Here is the Teac HA-P50:Peak error is now as much as 1.6 dB.Sorry, there is no subjective review.I am so far behind testing products that I just don't have the time for level matched listening tests. Depending on when the owner wants them back and if I have time, I can do some listening. Otherwise, please ask the owner what he thinks.If you don't need the extra power of Teac HA-P50, the Sony PHA-1 is the winner. It is a more proper implementation with no warts. That said, high output impedance is a problem for both and the much newer Topping NX4 DSD at $160 with shipping included remains my recommended choice.As always, questions, comments, corrections, etc. are welcome.-----If you like this review,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 ).