ECC81/12AT7 Nos

regardless the device, tubes often influence the downstream signal.

12AT7s are sometimes on the input side of the amplifier and as such will flavor the overall sound one way or some other.

RCAs from the 60s for example which I own, soften up  the audio a tad, adding a bit more relaxed sense of being.

from the same Era, Amperex Bugle boys step up the notes leading edges. and add more bottom end and insightfulness to the music.

I've mixed the rCACs AT7 and Bugle Boys AX7s on the output side, achieving solid dynamics  while still presenting a sense of ease to the music.

with RCAs on either end, things became a bit too soft for my tastes. with Bugle boys on either side things greatly perked up.

its like baking a cake some what... its always a result of the types of tubes being used in conjunction with each other.

its a tad harrowing from time to time trying for a particular 'flavor' and the safest bet IMO is to begin by using the same brand, model and ear of NOS and if not happy wash, rinse, repeat. or try other combinations.

there used to be a website which gave pretty close or accurate accounts on various tube type and era sonic attributes  called joe's tube lore.

good luck

Descriptions of AT7 tubes...

http://www.audiotubes.com/12at7.htm

Should I use for digital source.

Many thanks.

Depends on how you like your digital to sound.  In both my Manley monoblocs and tubed CD player smooth plate Telefunkens can’t be touched for overall naturalness, soundstaging and bass extension.  Phillips “miniwatt” are also very good, but tip the balance upwards.  Siemens triple mica’s even more so.  Raytheon also made a good 12at7 that I like very much in my applications offering good clarity and which can be found relatively inexpensively.  Many 12at7 variants out there also that are worth considering, but don’t fall for the often stated claim that a particular variant is “better” or that a particular variant sounds a particular way.  Depends on the particular manufacturer of the variant; not all examples of that variant.  Good luck.

Thanks!!