I'm about to put up some info on the PrimaLuna website about this. First, in preamps all the small signal tubes have an equal effect on the sound and you can change out just one pair if you want.
On power amps and integrated amps the two 12AU7 (in older models 12AX7) that are in the center are the input tubes and they have gain, so they will make the most difference.
I've spent a lot of time on this. The stock tubes are surprisingly good sounding. Fabulous. The French-made 1962 vintage Cifte's will have a little more extension on top, and that's why the mids are not as up-front. But that will change in time. They have a lengthy break in period. I would say a couple hundred hours. But really it takes longer than that.
I've been running 60's vintage Mullard M8136 and they are really nice. I don't know if they are for me exactly. They have more body. The mids are fuller and pretty. But the reason it sounds this way is because it's more laid-back on top.
I've also tried some British-made Brimar CV4003. These are hard to find, but we recently scored a nice quantity of perfect ones. I've always liked them. They are between the two above.
I have customers with really good ears tell me that they love the stock tubes and I agree. I hope this helps. If you guys have questions on this it's really great to put them up here or audioasylum as others DO benefit even years later from your data.
On power amps and integrated amps the two 12AU7 (in older models 12AX7) that are in the center are the input tubes and they have gain, so they will make the most difference.
I've spent a lot of time on this. The stock tubes are surprisingly good sounding. Fabulous. The French-made 1962 vintage Cifte's will have a little more extension on top, and that's why the mids are not as up-front. But that will change in time. They have a lengthy break in period. I would say a couple hundred hours. But really it takes longer than that.
I've been running 60's vintage Mullard M8136 and they are really nice. I don't know if they are for me exactly. They have more body. The mids are fuller and pretty. But the reason it sounds this way is because it's more laid-back on top.
I've also tried some British-made Brimar CV4003. These are hard to find, but we recently scored a nice quantity of perfect ones. I've always liked them. They are between the two above.
I have customers with really good ears tell me that they love the stock tubes and I agree. I hope this helps. If you guys have questions on this it's really great to put them up here or audioasylum as others DO benefit even years later from your data.