I've had a Recto-Verb 25 for about year and really, really love the sucker. But, recently have been having more opportunities to start cranking it up and it's not nearly as great as I expected on that front. Turning it above about 5-6 on anything other than pristine clean settings adds some serious trebley fizziness that almost sounds like running an amp through a bad attenuator or something. Just really didn't expect this amp to sound better with moderate volume +higher preamp gain than the inverse. Is this a known Mesa design shortcoming that I'm just unaware of or should I start troubleshooting my power tubes?