This is a great amp 1 issue with the amp is it hummed very loud when new tubes where put in so I did the fitz mod no more hum. I did not purchase my amp from Massdrop so the newer stock may not have this issue. My second issue is this amp runs hot and I do mean hot, you can burn yourself if not careful on the tubes. When tube rolling you can also get adapters to use smaller 6922 tubes and variants of that tube type in the front since I had a few from my first hybrid tube amp the Bravo Audio V3 I got off Massdrop. Lots of info on tube rolling on Head-fi for the DarkVoice and info on how to do the fitz mod which is not hard or expensive to do. I just purchased a 220uf capacitor and soldered it in place.