Both models, 3.21SE and 3.21 signature, have received significant improvements.
The signature model now has two coolers
SE — one cooler.
Both models received a new top cover with a logo and holes on the sides. This greatly improves heat dissipation.
Both models also received a more powerful tube rectifier 5U4 that powers the current-voltage converter circuit.
Many more minor changes have been made to improve thermal stability and reliability.
Signature version:
SE Version:
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