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This is a review and detailed measurements of the xDuoo TA-10 DAC and Tube headphone amplifier plus pre-amplifier. It was kindly sent to me by the online store, Xtenik Audio . The TA-10 costs US $290.I must confess, my impression of xDuoo is one of ultimate budget products, with looks and performance to go with that. So I was hesitant to accept this review when Steven from Xtenik Audio reached out to me. I warned him that I would write the review as I see it, bad or good. To my pleasant surprise, he was perfectly OK with that. So here we go.Everything I thought about xDuoo as a brand went out the window when I pulled the unit out of the box and noticed its attractive and high build quality:The rotary control feels nice and very responsive. The gold accent on the 1/4 inch headphone jack adds some interest to the black face. The XLR output is for convenient, not for "balanced" output as testing will show later. There is a balanced version of this unit with two tubes to provide differential output.The paint feels slippery in a nice way.There is quite a bit of heft to the unit, again giving a feel of quality.The back panel shows a wealth of functionality not obvious at first:In addition to the standard USB input, there are two analog inputs. This is music to my ear as I have an analog source (Reel to Reel) and I am so annoyed to have use a pre-amp because the DAC doesn't have such an input. If you have a turntable, you can integrate it easily just as well. Or a portable music player.The volume control is implemented using a TI chip so it is able to control the output of the pre-amp in addition to the DAC. You will get perfect channel balance in this regard but likely at the expense of some noise than if it was implemented in the DAC (and hence not working with analog input).There is S/PDIF output allowing the TA-10 to act as a USB to S/PDIF bridge as well.Yeh, there is that tube. Does it destroy the performance of the nice looking unit like this? Let's find out.Given the line outs, I started my testing just measuring the DAC portion independent of the headphone amplifier:Wow, what do we have here? Surely this can't be going through the tube with its excellent THD+N and hence SINAD (signal over noise and distortion). The TA-10 easily lands in the second tier of all DACs tested, credit going to the good implementation of AKM AK4490 DAC chip:Output level is a bit low though at 1.7 volts. Which they had juiced this up a bit more to meet our nominal requirement of 2 volts.Orderly measurements follow in other tests such as frequency response:And jitter:Surely they screwed up linearity:Nope. That too is excellent.How about intermodulation distortion versus level?Performance parallels the excellent Topping DX3 Pro but with some penalty in noise department (and a bit on distortion). As I predicted, the TI volume control is adding its own (small) layer of distortion and noise. But hey, this is still very nice performance as most DACs struggle to match or beat the DX3 Pro.So clearly the tube is out of the loop on DAC output. Let's all cheer at once!Let's start with measuring power versus distortion and noise using 300 ohm load:Ouch! The tube does a number here creating the typical rise of distortion at less than 1 milliwatts of output. That is heavily offset though by tons of output power, producing nearly 1/3 of watt.Going down to 50 ohm and measuring both connectors we see identical performance there:Most if not all the tube headphone amps I have measured fall apart with low impedance loads. They have high voltage output so do well with high impedance loads. But have little current and hence do poorly when the load impedance goes down. Not the case with TA-10. It motors on producing whopping 1.5 watts of power here!Stepping down even more current hungry load of 33 ohm we get:Now we are peaking over 2 watts of power! Nice. But yes, distortion is through the roof compared to solid state designs.Frequency response remains ruler flat:Channel imbalance is non-existent due to use of digitally controlled analog IC volume control as mentioned in the review:While you can get this type of performance in DACs with volume control, you have very few options to do the same for analog inputs that TA-10 has.Output impedance is decent:Note: original review had this measurement incorrectly as 47 ohm.I happen to have my son over again with his undisturbed high frequency response that I lost years back. We matched levels with a Topping DX3 Pro as best as we could using ear (electronic matching is not very effective due to high output impedance of TA-10). Using HD-650 headphones, my son could not tell the difference. I thought I heard some subtle changes but really, nothing that I can swear to be able to tell consistently. And certainly not if I listened to TA-10 by itself.Just listening with the HD-650, the TA-10 had thundering amount of power, detail and fidelity, belying its poor measured performance. Power erases many sins here.Switching to Hifiman HE-400i allowed me to hear some subtle differences. What there is though, is hard to describe as it was highly content dependent. I thought sometimes I heard slightly brighter but more detailed sound out of DX3 Pro as compared to TA-10. But really, the difference if there, is small. My son could not hear any difference.We then tried the AKG N700 in passive mode. It too sounded too close to tell the two units apart.Note that highly precise volume matching was needed to arrive at these outcomes. Just half or full dB of level differential titled the balance easily in favor of one or the other.As with all of my previous testing, there is no tube magic here, no widening of sound stage, "warm glow" or other nonsense. What you hear is what is in your music if you test in controlled manner.They say don't judge a book by its cover and I sure was guilty of that going into this review. The xDuoo TA-10 is competently designed and engineered both from mechanical and electronics point of view. The DAC implementation is quite excellent and feature set unique and highly desirable.The tube section does add copious amount of distortion. Alas, listening tests showed them to be highly masked by the content. What is not masked is very high power output stage enabling the TA-10 to drive headphones to distortions of their own, well before its own sets in. You get full flexibility to use wide range of headphones and still get to ear bleeding levels. Sure, there will be some change its frequency response. Hopefully that will tilt in favor of your preference, not the other way around.If you ever get tired of the tube headphone out, you can use its line out to drive different amps due to its excellent DAC implementation.If you are itching to have a tube headphone amplifier with least amount of compromises elsewhere, I am happy to recommend the xDuoo TA-10. Someone really knew what they were doing when designing this unit. Lesson to other companies that use the excuse of a tube and destroy the performance of the product in every other way.------------As always, questions, comments, recommendations, etc. are welcome.The panthers are complaining that I always take their pictures nude and are demanding to buy clothes to wear. Have you shopped for outfits for panthers lately? They don't come cheap! 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