What do you know and how do you like the RCA 5963 Black Plates?

I know this is an old thread - 5963, yeah I like this tube in place of 12AU7. RCA’s black and gray plates are very good sounding. For me, they should be limited to use in power amp slots only. They tend to be very microphonic in preamp and phono stage slots. These tubes were not "designed" for audio applications (the upside of this - they're still relatively affordable)! Quite alike the old 6SN7GT in the microphonics respect, actually (though 6SN7GT was designed for audio, it is very old). I guess if you’re dedicated you can sift through enough tubes to find a quiet set for your preamp.

RCA 5963 black plates used to be the tube of choice for VAC amps (circa 2000s), before they switched to 6SN7 front-ends for most of their amps.

I generally like tubes better than solid state. But sometimes a good SS component can surprise me at how good it sounds, and I’m definitely not opposed to mixing 1 or 2 into my systems. But an all-SS system - no way. I’d by far rather go all-tubes.

mulveling, did you compare various RCA blackplates from 50s to Raytheon blackplates from the same time period ? I really like the RCAs in the driver section and how they work together with 12AX7 Mullards in the preamp. I was thinking about trying both Raytheon blackplates and Mullard 12AU7 at some point, though there is no need really.

@inna I have not, sorry. My experience with 12AU7 types is much less than 12AX7, and I've had very few Raytheons of any type (strangely). I do very much like the RCA 5963 (either black or gray plates) in 12AU7 amp driver slots, though. I currently have them in a Rogue Stereo 100, driving Tung-Sol 7581A tubes. 

mulveling, I see. I thought you had all VAC electronics, or this is your second system.

Yes, the 2nd system / office rig is sort of my "sandbox" system. That’s where the ST100 is. I have VAC Master monos and premap in the bigger loft rig. Also got a VAC Statement 450S floating around lol. Speakers have been Tannoy Canterbury GR in the loft for years; recently re-introduced my old Canterbury SE in the office rig.

So, RCA 12AX7 black plates from 50s are not microphonic, I understand, I might want to try them too instead of Mullards, though I would not anticipate the improvement, but who knows ?

I mean they can be microphonic - all tubes can. But in practice, yeah my RCA 12AX7 (including 1950s black plates) have generally been usable even in phono stage slots. In fact I used black plate RCA 12AX7 in a Rogue Ares phono stage, several years ago. I liked them a lot there. And right now I've got them in the ST100's V1 slots, in front of 5963. It's a good all-around tube. Definitely not bright, and not too warm. Mullards ended up being a bit "thick" for my liking (12AX7/CV4004, 12AU7/CV4003, EL34). And I'm a guy who loves SPUs and Koetsus - so I don't know why Mullards turn me off like that, but they do. Somehow those come off as "too thick" and syrupy, whilst Koetsu and SPUs come off as "full bodied", "natural", "energetic", and "organic". But you really just have to try for yourself. The Mullards are fine tubes to be sure. I just never end up leaving them in for long.