This is a hard review to write, as for the price it is an excellent bit of kit, however the first one we ordered was a disaster the pots went one by one over just a few weeks and was unusable it was a real disappointment.
I've only ever had to return one other bit of kit I bought form Thomann, and this service is absolutely first class, they replaced the first one and the second one works fine.
Having 4 separate feeds is fantastic for our band we all use IEMs and having a personalised mix to each member of the band makes for better performances.
The sound is OK, but really on stage using IEMs you're not looking for HiFi quality, just a clean signal and the mix you need. Great for stage work or even rehearsal and recording - but not for anything above that.
Although you'd have to question the logic behind anyone buying this type of preamp for HiFi listening, it's great for what it does.
For bands on budget who want to move to personalised IEMs it is a very good investment.