Qudelix T71 USB DAC

Before I start my review, I just want to say that I distrust most "audiophile" reviewers, and the T71 only reinforces this belief. You don't NEED an AMP/DAC unless you need to turn your volume up to 100% to be adequate, so in most cases the only reason to buy a particular model is because of it's features. If you're one of these people with an old or underpowered device, in theory you will get an improvement in terms of volume and bass simply from an AMP/DAC alone.Firstly then, no, the T71 doesn't change how your headphones/IEM's sound by default, which is a good thing. The AMP simply amplifies the signal, while the DAC removes any noise from the source.What differentiates this from others is the little physical additions and the software inside it.Physically, it includes both USB-C and USB-A adapters. On the output side, it supports 2.5mm, 3.5mm, and 4.4mm connections. It has a 1000mAH battery, but as I have it connected to my PC I can't comment on how long it lasts.It also has a built in mic, which I would describe as an average headset mic. Sound quality is okay, but it picks up all the noise around you. If you have noise cancelling software it will be passable, but it's not something I would personally rely on as a mic. It's a nice to have feature that doesn't detract from anything.Software is where the T71 stands out, which is frustratingly what most reviewers neglect. Personally I use EqualizerAPO to EQ my headphones and BS2B for crossfeed, but I wanted an alternative. In all my research, I only found a few devices that specifically have parametric EQ and adjustable crossfeed (the smaller Qudelix 5K being a popular example).The Chrome extension works great, and I've had no issues navigating it and updating the firmware. I would highly recommend this method for configuring the T71, as the hardware buttons are bit confusing.The unique feature of the T71 is the dedicated 7.1 virtual surround sound. I'm not fond of virtual surround sound, but in my brief testing it sounds more natural than Windows Sonic at least. You can adjust the volume, EQ, and apply crossfeed to each channel as well. Stereo audio sounds slightly forward when output as 7.1, which doesn't sound bad, but does reduce the soundstage slightly. You can set this to "Auto" as well, which will automatically switch between stereo and 7.1 depending on the source.The EQ is split into two 10 bands. The logic being you can use 10 bands to EQ your headphones/IEM's, and the other 10 bands to create profiles for different scenarios. Personally I don't care about profiles, so instead I use this as a 20 band EQ, which works perfectly albeit a little unintuitive. I've attached some pictures which briefly explains how to configure this.AutoEQ has been abandoned, so I'd highly recommend learning how to navigate squig.link. Different reviewers (good and bad...) can upload their own frequency response measurements and EQ curves. Personally my preference is "Harman In-room Flat" with "Harman 2018 Filters" for headphones, and "JM-1" with "Harman 2018 Filters" for IEM's.Finally, the crossfeed (or xfeed). Crossfeed is a very contentious feature, but I think this is because most people have only heard poor implementations. Qudelix's algorithm uses a 0-50 scale, with 0 being off and 50 sounding like the audio is inside your head. I would highly recommend something between 10 and 25. 10 being subtle, and 25 being the limit before losing detail.Overall, I was pleasantly surprised with this device. With most reviews neglecting half the features, or making claims about audio enhancements with no measurements (seriously, why are there no measurements for headphones with and without an AMP/DAC???) I was half expecting to waste £200 on a fancy USB adapter. If you're looking for a hardware solution to EQ and crossfeed (and 7.1 virtual surround sound), there's nothing else like this. Once configured properly, it's one of the few AMP/DAC's that actually does improve your audio. The fact the developers also acknowledge squig.link means they really are paying attention to the community as well (for better or worse!).