I’ve had similar problems . The best buy , unless you want to spend 2K $ on NOS (which may not be same) Sylvania 6550’s is to to buy a matched quad from "the tubestore.com " This Canadian firm is honest
and does a good job .I got a Quad of KT 88 from them few months back to replace 6550’s only to see the sound difference . In My AES-25 Super Amp the 88’s are a bit clearer which I like .
The 6550’s ran for 4 years and are still fine . tubestore calls these quads "Preferred" , only few bucks more .
and does a good job .I got a Quad of KT 88 from them few months back to replace 6550’s only to see the sound difference . In My AES-25 Super Amp the 88’s are a bit clearer which I like .
The 6550’s ran for 4 years and are still fine . tubestore calls these quads "Preferred" , only few bucks more .