I am slowly building two PPA amps. I had the opportunity to listen to a PPA supplied by JMT for our Central Florida Meet in mid December, ( Thanks JMT) it used BB627's. The overall sound of the amp was extremely clean & neutral. The low end was ok but did not compare with the kick that the Chiarra gives. The mid & high frequencies were good but not spectacular;I attribute this to the overall laid back sound signature of the OPA 627.
Hopefully the PPA will really come alive with more sonically aggressive chips. Not trying to rain on anybodies parade, just calling them as I hear them.