12ax7 vs 5751

hiya mikirob, i`ve had those on my mind too! i`ve liked the ehkt88`s in there but when i bought them i`d only done limited research into all the tubes. i`m doing a much more in depth research now. i ordered a matched pair of ge5751 black plate d getter 1950`s tubes today. once they`re sorted i`ll start researching the kt88`s. i wont rush my research like i did when i first got the amp. this has been such a fantastic learning curve researching all these tubes and reading other peoples experiences with different tubes. i still can`t get over the differences made by swapping the brimar/rca vt231 combination. i honestly didn`t think there`d be any difference at all by swapping them around in v1 v2 v3 v4 positions. that was an eye opener for me! all my neighbours were out earlier today so i was able to crank the volume up! i`m endlessly impressed by what i hear now. the only thing i think this amp lacks now is soundstage depth and i`d like to inject a little warmth into it. not much just a little.

i ordered a pair of ge5751wa black plate d getter tubes and a matched quad set of shuguang black treasure kt88-z`s. the ge`s are coming from china and the black treasure are coming from hong kong so i guess i`ll have a bit of a wait.

i`m excited to know how these will fair along with the brimar 6sn7gty cv1988/rca vt231`s combination. the brimar/vt231 combination have so far opened up the sound extremely on my system. at some point in the future i`ll be ordering the Sylvania JHS 5751WA Gold Label triple mica blackplates but i`ll have to start saving! i`ll also see how i get on with the ge5751wa`s first.

meantime, the sound is still improving on my system so i guess the brimars are still breaking in as they are nos tubes. i still can`t get over the huge difference they`ve made in my system. i`ll update next when the tubes i`ve ordered arrive. the only thing i`m not that thrilled about is the break in time for the black treasures. 300 hours!!! they`ll take forever!!!

Joes tube lore is far from the authority on 12ax7/5751( or anything else)The performance of a tube is going to be application dependent. Any one whos rolled tubes can tell you what works in one amp doesnt always work well in another. A 5751 can be quieter in the phono position on some amps but you wont necessarily find them to image better. You could buy used tubes on ebay and experiment using your ears or you could buy from a knowledgeable dealer Im sure this group can recommend reliable dealers, upscale audio comes to mind. Ive heard good and bad examples of almost every tube Joe listed, to experience the general character of a specific brand type you have to listen to several examples in a variety of applications. Brent Jesse's site has good info on a lot of tubes.

Joe states all that in his Lore article; but if you are new to tubes it is a good, worthy place to start.

meantime, the sound is still improving on my system so i guess the brimars are still breaking in as they are nos tubes. i still can`t get over the huge difference they`ve made in my system. i`ll update next when the tubes i`ve ordered arrive. the only thing i`m not that thrilled about is the break in time for the black treasures. 300 hours!!! they`ll take forever!!!

Well the good news is they will only sound better as the hours count down. Personally I found with any new tube you need at least 200 hrs before making any judgements.