Gary Mattis
Active Member
I have been doing a lot of research lately on These 3 Output tubes and other than their heater currents and the typical applications there is not any real way of comparison other than amp designs and peoples opinions. I know that all 3 tubes have their own sounds, 6L6 bright, 7591 detailed, EL 34 seems to have a little bit of both with it's own smooth voice or tone. 7591 tube data is very limited and as far as I can tell 16.5 is the gain factor - if what I read was correct ? . Heater current is certainly something to consider when going from 7591 to EL 34 , but not so much on 6L6. But if the PT can handle it for say 4/hours without meltdown it is not that big of a deal unless you do not ever turn your amp off. Max PT ma. specs are not that easy to find. From my research most pre amps can easily handle the change from 7591 to 6L6 or EL 34 tubes. This seems to be over exaggerated as something that you should never do ! . I understand why they say it , they think the low heater current and max gain 5791 tube specs are everything, that is their opinion , not that I really agree with it , but I can respect it as educated also ! . The fact is 7591 tubes were given up on by most tube amp builders for some reason ? . EL 34 and 6L6 tubes are still used in just about everything with 40 watts and up ! . Which of the 3 tubes is actually the best tube ? To me The EL 34 Mullard is the best sounding tube ever made , I know that is just my personal taste and my opinion ! But I do not go directly to 6L6 or 5791 after EL 34 , Vintage Mullard, RFT, Amperex, Telefunken and Vintage Tesla. I go to 6V6 next as a little EL 34 tube. 20 to 30 watts 6V6 is my choice, Small Class A at 5 to 10 watts up to say 15 watts two EL 84 tubes I like. At 40 watts I like 6L6 tubes. At 50,75,100-130 watts I like EL 34 tubes the best. The 7591 tube has never really been on my list of favorite tubes. The Vintage Telefunken tubes though very detailed lack color or tone sometimes and can be very sterile sounding and even noisy in Phase inverters and in certain amplifiers . I have noticed Mullard 12AU7 and 6X4 have way too much bass in some amplifiers. One person can love a tube in their amp and another person can hate the exact same tube in their amplifier. I do not want to go by tube brands or amplifier companies but by overall ability and design of which tube has the best overall proven design !. Sense each tube requires fine tuning and design change it is important to know which tube is actually the best and why the 7591 was abandoned by most amp builders and tube makers !
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