Sorry, i was wrong informed. The Lepai does use the TA2020. So you found the TA2024 better then either the 2020 or 2021? In what regard?
In another time, place and implementation, the stock TA2024 amps seemed a little smoother on the mids and highs when used with HE full range driver speakers. In less revealing situations (e.g., 2-way speakers), I'd be challenged to detect a difference.
When modifications are made where power supplies, caps and inductors are upgraded, it's hard for me to state one is clearly better than another. The TA2020 and 2021b have a slight power advantage and afford a little more flexibility in choosing speakers. In the end, they are small t-amps and share the characteristic great bass and suspect highs (IMO). Again, I find the Lepai tone controls to be helpful with taming the highs. Air core inductors seem to help the highs as well, but can cost more than the stock amp.
They are impressive for very low prices and should be celebrated for what they are... highly efficient and enjoyable little music makers. The wooden boxes NSMT employs are undeniably cool and makes me want one.
