'58 RCA long black plate 12AX7 quad for my Fisher

My '59 Fisher X100 came back last week from the shop, where it was getting a little TLC. A grounded power chord was added (to remedy a voltage leak to the chassis) and the tech replaced one cap in the preamp section. The fellow I had bought it from had recapped it prior to sale, and my tech confirmed that the work was done properly.

After getting it home and setting it up, I was disappointed; it sounded kind of... lean, slightly harsh, 2-D and quite un-involving. Bass response was lacking too. The next time I turned it on, the right channel was barely audible and there was a loud him in the left channel. WTF?!?

After thinking on it for a day (it was now the weekend and the the shop was closed), I decided to swap some tube pairs between channels. A ha! I quickly figured out that one of the 12AX7s in the preamp section was toast! Fortunately I had a spare Mesa Boogie-branded 12AX7 in my stash, so it was up and running again - but still didn't sound awesome.

Taking a closer look at what was in there, I noted that there was a single GE and a pair of RCA grey plate 12AX7's in there, in addition to the Mesa Boogie (Sovtek?). I have no idea how they measured or how much life there was left, so I decided it was time to wipe the slate clean and just get a replacement quad.

I really don't know the finer points of tube swapping, so I did some reading. GE is apparently not especially well-regarded, and the current production long plate Sovteks have favorable reviews and cost about $50/quad. I almost went in that direction until I found an eBay seller offering a couple of dozen 1958 RCA long black plates that measured well for $25/ea. From what I read, these are considered some of the finest USA-made tubes, and the descriptions I read sound like they have the presentation that I would enjoy.

The tubes were delivered yesterday and I put the strongest-measured pair in the phono section, although they are all closely matched. Blow me down, these tubes make my X100 sound spectacular. The presentation is full and well-balanced, with some real meat on the bones. The bass I was looking for is back again, and it's not flabby either. There's more sparkle on top as well, even though the overall character is "warm" (but not dull). There's lovely midrange bloom, and delicate but extended treble. It's decidedly quicker and more lively than before, and yet has a very smooth, romantic presentation. Imaging is wonderfully transparent, well-defined, and vividly 3D.

In short, the old Fisher has come alive!

This was the best $100 investment I've made in my hifi in a while!

 

Good job! Now be content.



Do not lust for that vintage Telefunken smooth-long plate 12AX7 (ECC83) Quad ....................

 

Stories like that are great to hear! Congrats

 

GE are not well-regarded? Maybe I would prefer (NOS) Mullard or Telefunken in most applications over GE, but I certainly wouldn't consider GE not well-regarded. I would take a GE over a new production Sovtek any day of the week.

I see you went with RCA. Definitely the right choice over Sovtek!

 

The GE tubes are said to not be in the same league as other vintage tubes, and are surpassed by some current production tubes. That's what I read.

I'm real happy with 'em.

 

Surpassed by new production tubes? From Russia or China? Who's saying that? People selling new production tubes? (Not trying to be negative, it may be someone's opinion which is fine, it's just not an opinion I hold).

I'm still happy you found some great sounding RCA's! I consider Mullard, Telefunken and RCA's some of the best 12AX7/ecc83 tubes ever produced.

* Disclaimer - I don't sell tubes, neither old production nor new production.

 

I really like the RCA black plates. I'm using four in my Harman Kardon A500. I use them in my Fishers too.

 

Like I said, I'm still learning the finer points of tube swapping and have to rely on user comments. I'm not really qualified to comment any further.

I went with the RCA black plates because they seem to be universally well-regarded, and it's worked out!

 

I've got those in my preamp section at the moment with some Mazda CIFTEs in the phase splitter. Sounds great with this cartridge setup.

My take on these in my situation are that they really do spotlight the presence area, which is great for most popular music. I find these fill out the mid-bass very well, but do not have that very low end grip that my EIs from the same period have. They also lack a little on top, but with a cartridge with some real world frequency roll off, I feel like they are spot on and staying in for the next while.

 

They're red tipped which means they were considered medical grade tubes back in the day. I just ordered two from the same seller because at that price they are a great deal. In fact I might get a couple of more to keep around. I own Mullards, Telefunkens ( smooth plate, ribbed, short, long ) Bugle Boys, GE, and few other makes but I've always liked the RCA black plates.

 

My 12ax7 in my fisher are by Raytheon from 1957. I think they sound great. Anyone know how they compared the the others being discussed?

 

I use the Raytheon black plates in the phono section of my Fisher 400 receiver. They are my favorite phono tubes.

 

I was wondering about that. Only one of the four I received has the red tip.

 

Keeping it local, eh Mo?

 

Thanks for the tip, I just bought a pair. When I return home next week after several months away on a job, my new Icon Audio PS2 Tube MM phono preamp purchased here on the Forum awaits. Looking forward to hearing these RCA's in it.

 

Red tip or no red tip at 25 a tube that's a worth it IMO.

 

In my phono and I think the fm I have fisher labeled 12ax7, I though about switching with the Raytheon for a comparison

 

That's great! Isn't playing with tube amps fun? A simple swap-out of current input tubes for some nice vintage ones can make a whopping difference. In fact a really significant upgrade -- and it cost you $100. Much more bang for the buck than swapping interconnects I bet!

 

Glad youre happy with the rca's. I did a shoot out myself for my amp's pre amp section. Grabbed one pair of tele smooth plate, one pair of blackburn era mullards, and one pair of those exact rca's you have. All were a nice improvement for sure, with me leaving the tele's just for the edge in transparency overall. The rca's actually went to my 77' marshall jmp for the time being. Great tube

 

That's a great deal. Those 50s RCA Black Plates are just about the lushest sounding tubes you can find.

Raytheon black plates are my favorites. Sadly they are getting pretty pricey now. Personally I think they have the best tonal balance of any 12ax7 and last forever.

As for GE 12ax7. I personally think they suck. The do make some nice 5751s but I think those are way over rated. Though I think pretty much any NOS 12ax7 is better than the new production stuff and they'll last way, way longer.

Some other really great tubes for Fisher gear that arent hugely expensive are real Tung Sol NOS, especially for the phase inverter spots, and Sylvania Black Plates.

 

Glad you' like your RCA's.

I seem to be the lone dissenting voice on RCA black plate 12ax7s and 5751s, but I've never found an application for them in hifi in which I liked those tubes. To my ears they're always way too bassy and overly warm and overly rich in the lower midrange

Plus, in the old days, when they were plentiful as used pulls and even NOS, I went through a bunch of 'em and if they didn't start noisy, a lot of 'em turned noisy so I finally got completely frustrated with the darn things. I still have maybe half a dozen sitting around in boxes, including "Command" series 12ax7 and maybe one or two 5751s with very little use on 'em.

However, back when I was playing a lot of guitar out and doing a bunch of recording, I really liked 'em in Fender blackface and silverface amps which have kind of scooped midrange and can use a little bass and midrange oomph and fatness when you push 'em. That's why I wound up with a bunch of those RCA blackplates in the first place.

There are '50s blackplate 12ax7s that I like a lot -- never heard the Raytheons (I have heard the legendary Raytheon windmill getter 5751, and I think it's everything its reputation says it is, but it's the antithesis of say an RCA blackplate 5751: its quiet, clean and transparent sounding) but I love the Sylvanias, kind of my go-to default 12ax7: dynamic, punchy, extended on the top and bottom, balanced across the frequency range. Some people have suggested they're a little soft on top, but I dunno, not compared to say Mullard '60s long plates. For a long times those Sylvania black plates were also cheap as dirty because they didn't have audiophile cache, no one had written 'em up as some kind of audio unicorn. Now any '50s tubes are getting to be in short supply so the prices are all elevated, though $25 a tube for those RCA blackplates is a great price.

But I guess more people really love the thick, "lush" sound of those RCAs much more than I do.

 

The tubes were delivered yesterday and I put the strongest-measured pair in the phono section, although they are all closely matched. Blow me down, these tubes make my X100 sound spectacular. The presentation is full and well-balanced, with some real meat on the bones. The bass I was looking for is back again, and it's not flabby either. There's more sparkle on top as well, even though the overall character is "warm" (but not dull). There's lovely midrange bloom, and delicate but extended treble. It's decidedly quicker and more lively than before, and yet has a very smooth, romantic presentation. Imaging is wonderfully transparent, well-defined, and vividly 3D.

Vintage tubes strike again...

 

This is my experience also. In two SCOTT 222C amps. I prefer Telefunken 12AX7s by a large margin. But regarding the OP, each amp is surely different in regard to tonal characteristics and my two SCOTTs just love them Teles. I have tried RCA black plates, Raytheon, Sylvania, Siemens, etc

 

What's lean gear mean?