The EH's are supposedly Sylvania style 6CA7's . I have a Pair of Mesa str 416 EL34/6CA7 in my JVM 410 , what a difference from the EL34 svets it came with . Less noise , quite a bit tighter for the chuga chuga . Way bigger bottom end and yet still tight. The attack seems quicker .Im really in love with these style of tubes . Yes the EL34's are a bit more fluid and have a hell of a roar but, the 6CA7's are just huge and crushing . Plus just the pair cut so much FIZZ out of the JVM . I wanted to mod the Marshall for 6550 or kt88's . The 6CA7's will do just fine without the mod . Thank you Yontz from Mad Science Works here in Raleigh , he suggested that I try the tubes out . Luckly, I somehow found a pair to try out .
Z