If you read my tube rolling thread you'll see that I feel like I'm getting a good feel with how the KT88 Firebottle amp changes with different kinds of tubes. I'm still going a little crazy when I add my active preamp though. It changes in ways I can't figure out.
I loved the Sylvania 6sl7wgt/Sylvania 7c5 combo so much I decided to try it with my new preamp. I put in a pair of grey glass 14n7 tubes and WOOOOSH! Super smooth and lush. Just creamy sounding. Voices were hauntingly real and massed strings were just a dream. But there was no bass. The entire sound changed radically and the bass was MIA. This preamp uses output transformers so it shouldn't have any weird loading issues so what's going on?
I realized that I had yet to break out the expensive tubes I had starting hoarding for this preamp. I found a NOS tube of the "bad boy" Sylvania 12sn7 tubes. Time to see what the fuss is about. Ooh, that's nice! Lushness retreated but vividness got cranked up. Bass is a little better. On a whim I replaced the 6sl7wgt in the amp with a tall 7n7 and I got back a lot of the bass and lost a lot of the lushness.. Now I feel like I'm getting the "rightness" of the 6sl7wgt/6v6 combo but the sound is bigger and richer.
This is what I had in mind when I splurged on this preamp! I'm still scratching my head on the tube combos and how things are working together. The tube compliment on the amp sounds totally different with a passive preamp vs. the active. Hope I'll be able to figure out the pattern.
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