12ax7 vs 5751


hi all,
i need some advice. i`m very new to tube amplifiers and i`ve been doing some tube rolling.

i currently have a pair of grant fidelity matched psvane 12ax7t`s in my amp which sound fantastic.

what i`d like to know is which are the better tubes, 12ax7`s or 5751 tubes. i`ve been looking at forums and there are folk out there that say 5751 tubes are better than 12ax7 tubes.

can i have your thoughts on this please and also which are the good 5751`s to go for.

i really like the psvanes but if they can be bettered i`d go for it as my next line up of replacement tubes.

my amp is a yaqin mc100b. the tubes i have installed at the moment are.....
2 x psvane 12ax7t`s
2 x brimar 6sn7gty/cv1988`s
2 x sylvania 6sn7gtb`s
4 x electro harmonix kt88eh`s

many thanks in advance guys.
grayf
hiya guys these are great feedbacks and you`re all helping so much. can`t thank you all enough.

well i also ordered some jan philips 5751`s and got them this morning. of course i put them in straight away!

ok my initial impressions so far and also keeping in mind that these are nos tubes so they will need breaking in. i really like them. they have an added warmth and are just as detailed as the psvane 12ax7t`s. i seem to have lost a little soundstage width but gained some depth. also i`ve lost the added punch in the bass that the psvanes had but the bass is still very seductive, deep and pleasing. listening to adeles cd her voice still has that natural dryness but with these tubes there`s an added warmth and to me there seems more detail and depth to her voice. in the soundstage there is also more precision than the psvanes but less seperation due the soundstage not being as wide but i`m not talking by much. i do have one criticism though, one of my very favourite cd`s steve hillage green, some of the synth notes seems dull and less involving as does his voice on a couple of tracks. i use this cd to check out the high frequencies and these tubes pass with flying colours! every bit as pleasing as the psvanes but it`s such a shame about those synthesiser note and his voice but as i`ve said, these tubes only have about 4 hours on them and they`ll more than likely open up at some stage and that`s going to make this experiment much more interesting! so far if i had to choose between the psvanes and the philips the psvanes would just about edge it so lets see what happens when the philips tubes open up!

the tubes i`m currently waiting on now are the ge tubes, sylvania 5751`s and the kt88-z treasure tubes. this is all getting so interesting. i`ll keep you all posted at every stage. i have to say too that i bought the jan philips 5751 tubes from a uk vendor and ordered them over the phone. this guy was fantastic and very knowledgable about tubes in general. we spent the best part of an hour discussing tubes and being given all kinds of advice. i`m having the time of my life even though this is sucking the hell out of my finances!!! you gets what you pays for i think! more to come soon guys :)
oh and one other thing i`d like to mention about the jan philips 5751`s, they run silently with no signs of being microphonic.
just another quickie update. with just 7 hours on the jan philips tubes and things have changed! wow and i mean WOW! everything sounds much clearer, as if they didn`t sound clear enough before! the extra clarity makes each instrument sound as if they are in their own spot within the soundstage and you get the sensation that you can see right into the recording. i don`t hear any extra information on the cd`s but the information that is there is far more pronounced and set naturally into the soundstage. just listened to dave gilmours on an island cd and this is by far the best i have heard this cd. throughout the cd his guitar has the most amazing tones that have real bite. i have to say this is a damned good recording that i`m totally addicted to listening to! no doubt there`ll be more to come soon.
Yes, when you change out the EH KT88s you will get more improvement.
Best of luck in getting the best out of your system.