I Have a long discontinued amp by SJB Audio 'Ant'. It was a 30 Watt amp with 4 6V6 in the power section, but its the preamp thats causing the confusion. The valves are laid out parralel to one another 4 6V6 too the front and the peramp valves at the back. Preamp layout is as follows, looking from the back and going left to right. Ge 5751, 12AU7, ECC81, 6u8a (ECF82) It should be pointed out that that amp has both reverb and tremolo. Heres the rub : Which is the first valve a signal see's the 5751 or the 6u8a ? Out of ignorance, I've assumed the 5751 is the first..But what if it's actually the 6u8a instead ? I've made a few observations that I'm hoping will help anyone able to help. These are: exchanging the 12AU7 for 12AT7 increses gain, the same result can be obtained by fitting Ecc83 (12AX7) in the place of the 12AU7, it should be noted that occilation occurs at high master volume settings with this type I've found minimal changes by exchanging the other valves, athough removing the 6u8a results in no sound at all So.. is the 6u8a (ECF82) the first or the last and what is it doing? The amp has no choke either and uses what I believe to be current limiting resistors, what on earth does this mean? I'm sorry for such along post but am at a loss as to how to understand this quaint but toneful amp, and any and all advise recieved greatfully!