This is a review and detailed measurements of the PS Audio Sprout100 integrated DAC, headphone and power amplifier. It is on kind loan from a member. The Sprout100 is an upgrade over the original Sprout and costs USD $599.I remember the first time I saw the Sprout at an audio show. I thought it was utterly cute! It is small and handsome little package with a ton of functionality:As you see, in addition to functions I mentioned, it even has Bluetooth included. And moving magnet turntable input. It is a dream product for a frustrated marketing guy in a high-end audio company like PS Audio, wanting mass market product that appeals to the "younger audience."The volume control is a rotary encoder with a built-in switch that powers the unit on and off. If you hold the button down, the LED color changes from purple to white, indicating bass boost is on. The rotary encoder is poorly programmed to have linear and slow response, making it very, very slow to change volume. To go from low to high volume you may have to turn it seven or eight times! We live in a digital age with music that is fast to access and comes at all levels. Having the ability to quickly change volume is important.Input selection is old school mechanical selector. I like the clear labels.The backside shows how much is crammed in there:I did not test sub out but it has sensor that automatically activates that output (and rolls off the mains?).In addition to USB input, we also have toslink optical which is nice in case of ground loops.The nicest bit is included power supply in such a small package. Kudos for managing to fit that in there and reduce clutter.There is protection circuit for both power amplifier and headphone. During testing I found it to frequently activate which simply turns off the unit. It caused a lot of head scratching until I discovered the latter action.It is also I think underdesigned from cooling perspective. When I started my DAC testing, I had the dummy load connected to the unit as well. After a few minutes of testing I noticed the signal went away. Then I realized per above it had shut down. Went to touch the power button and it was hot as heck. As was the rest of the enclosure which was super hot. Even the top "wood" panel was hot to touch. I would not rely on the 100 watt rating into 4 ohm to be a continuous rating for any length of time.The Sprout100 is rated at 100 watts into 4 ohm and according to PS Audio uses ICEPower modules.I should tell you that I hate testing multi-function devices like this.Every subsystem takes as much time as reviewing another product with just that functionality. In the interest of getting the review done, I did not bother to test the Vinyl input. I also did not touch the sub out or toslink.The inclusion of line out allows us to test the DAC subsystem independently so let's start with our dashboard there:The output was variable so I adjusted it to 2 volt. Per my review notes above, the power amplifier was on and was whaling away into the dummy load at the same time.PS Audio rates Sprout100 as having less than 0.01% THD+N distortion from line out. We are beating that although that is such a low bar. Equivalent rating in SINAD (signal over noise and distortion) puts the Sprout100 in our bottom quarter of DACs reviewed:Not a good place to be although probably fits the performance target they created for themselves for "lifestyle product" like this.Back to our THD+N rating, we can separate the components of distortion and noise and get this ratio:They are both contributing to the final THD+N but the noise is a bit more dominant. Likely in this small enclosure the could not get enough isolation for the DAC subsystem to reduce noise levels.The high noise level makes the jitter graph "pretty" with almost no spikes visible but that is because the noise floor is so elevated:Best in class DACs put that noise floor down to the bottom of the graph.Same noise problem manifests itself hugely in linearity test:That smooth, exponential rise indicates random noise polluting the voltage reading at each level. Noise-free performance then stops around 80 dB or 13 bits -- quit a bit shy of 16 bit performance of CD. In this day and age, I like any DAC to at least do justice to CD format, bringing fully transparency to 96 dB.Intermodulation test shows similar higher noise floor but also pretty early rising of distortion levels:Similar story for THD+N versus frequency:Dynamic range of the DAC is as spec'd:Note: all amplifier testing except when noted, is with an AUX-0040 Audio Precision filter in place to reduce high frequency components given the fact that this is a switching amplifier design.As usual, for amplifiers I test with 5 watt output. The trick is to know what to use for input level and volume control. With digital input that was easy as I set the level to 0 dBFS. But then I thought we want to know the performance of the amp alone so we better test with analog input and here is what I got:With digital input I could get over 80 dB by the way. But no combination of input and volume level could get us there with analog input. In some sense then the amplifier is good enough for the performance of the DAC.Frequency response showed different response in each channel:I swapped my loads and the curve did not change, indicating that the variation is due to the amplifier (filter) design, not differences in my loads. Clearly the channel in blue is resonating around 50 kHz, causing that large boost of nearly 20 dB! What you get with your speaker load and its wiring is unknown. The red channel is more behaved. We saw the same discrepancy between channels in the SINAD in the dashboard.Poking our noise into the design using high-bandwidth spectrum (FFT) analysis, we see this:Note that this is a raw test with the external filter removed. We clearly see the switching frequency around 600 kHz peaking up to almost -20 dB. You can have your own AM station if you like.We have an early rise in noise before 100 kHz which is due to some kind of noise shaping. There are a lot of other spikes which one could examine to see what is going on but I am too lazy to do so. Regardless, these amplifiers are not pretty to look at as far as performance above audible band. It is the price you pay for having 100 watt/channel amplifier squeezed into a little box.Speaking of power, let's measure that into 4 ohm load:We get 82 watts with both channels driven which is shy of the 100 watt specification. Noise and distortion is lower than Topping TP60 ($200) amplifier. And there is more power.Signal to noise ratio is "OK":Let's jump right in with power versus distortion and noise at 300 ohms:We have competent level of power but much more noise and distortion than our reference Topping DX3 Pro ($220 when not on sale). I like to see at least 100 milliwatts here and the Sprout100 delivers.Here is the picture at 33 ohm:We have 420 milliwatts of power until the Sprout100 shuts down causing the graph to shoot back to the left. In other words, the unit is distortionless until it shuts down.Output impedance is a bit high at 5.7 ohms:I started my testing with Sennheiser HD-650. There was enough power there for a very good experience. I could not detect any onset of distortion.Switching to Hifiman HE-400i, I got a bit more power and again, clarity and power until the end.Dedicated headphone amplifiers will produce more power but there was enough here with either headphone to give a bit of tingling to my ear lobes during bass so I was happy.I could not get the Sprout100 to shut down with the HE-400i so in practice this may not be a serious problem.The reviews I read prior to testing the Sprout100 all point to how great it is that a "high-end" company like PS Audio has produced such a mass market product. And that this association must be translating into excellent sound. Our objective measurements show that this is not the case. Performance of such subsystem as the DAC and headphone amplifier is nothing to write home about.Subjective aspects though are good: lots of power from the headphone amp and to some extent, from the power amplifier.The miss from usability is the super slow to change volume control. In many cases I could move it a notch and nothing would happen to the output in my analyzer let alone the ears.So where do we land? From objective performance I can't say that the Sprout100 lives up to the promise of the brand. From full functionality point of view at $599 it seems to be there though although I have yet to test many products in this category. For this reason, I am going to withhold giving or holding back a recommendation. Let the data guide you in that regard.------------As always, questions, comments, recommendations, etc. are welcome.The sun is out and temps are starting to rise so I need to buy seeds and planting soil to start our garden. 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