Posted by SteveBrown [ 198.151.41.203 ] on July 21, 2008 at 18:52:47:
Sometimes I surprise myself by re-learning stuff I already know. Last night my wife and I were listening to my 300B mono blocks and I thought I'd do a quick rectifier swap from the 5AR4 that was in them, to a 5U4. I didn't really expect any great sonic difference but for both of us there was an immediate and profound difference in the sound. The 5U4's gave a much more "wooly" sound, really poor compared to the 5AR4's. Due to greater B+ drop across the rectifier? Due to one being indirectly heated as opposed to directly heated? Hmm... we also tried a 5V4, which is a nice rugged rectifier but uses a bunch of heater current. No real noticable difference between it and the 5AR4. Anyway, for those who may have discounted the difference that a rectifier can make, give it a try. Reconfirms for me just how much the power supply influences the sonics of the amp.
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