Cons: Stock components suck, the design is not optimal.
I got this small amp from a local marketplace. It sounds OK when I got it, too warm, almost no treble.
After I got the schematic and tips from google I did some mods with this baby and now it sings!
What I did:
1. Cut some traces for crosstalk improvement
2. Make better grounding, measure voltage difference between in and out, make sure its not more than 1mV
3. Change the power supply filter cap to low ESR Panasonic 3300uF, 35V
4. Change 2 output caps to low ESR Panasonic 2200uF, 25V
5. Change 2 N Channel Mosfet to IRL510
6. Install 2 5K ohm pots and adjust tube biasing to 13.5V.
7. Install ferrites clamp on the power supply cable
I'm using it with my DT880 600 ohm, it beats XCAN V8 when I compare it in my local "fancy" hifi store. The owner of the shop was really surprised when I said the price was 60$ + 20$ for extra components.