RCA ecc83

Hi guys !

I've won an auction for these tubes, hope these are not crap. Seller claims they are from late 50's, D-getter, 30 degrees.
What's you opinion ?

Thanks !

Hi Crane,

those appear to be the classic RCA Blackplates. I have a few. I like them for their clean tone, very sweet. Some might find the edge on their dirty tones to be less than creamy, but it's dependent to some degree on the circuit they run in, they will like life better in a head than a combo, they can get microphonic if they have had a lot of use or on/off cycles. FWIW, the Raytheon long blackplate round getter halo is more resistant to microphonics than the RCA blackplate, and they have a very articulate, pretty tone palette to them.

Hi Crane!

Mavguy knows those tubes well. Watch for microphonics (or use as phase-inverter if microphonic). If not microphonic, they do have very clear cleans. Nice fat lows, good, robust mids, bright highs that stay articulate - excellent valves. I actually am learning to prefer these to long-plate Mullard 12AX7, since the RCA carry the heavier lows without accentuating nasal low-mids that the l-p Mullards do (I'm more sensitive to that now, and the Mullards are back in storage). In certain amps, the early breakup of the b-p RCA can be too raw and thick. They've given me an icky feel, kind of like ripping thick construction paper, when driven hard in certain amps. So try in several positions in different amps. You'll find a place for them, no doubt.

Now those are mid-'50s black-plate RCA. There are also RCA 12AX7 from the late-'40s (RCA produced the first 12AX7) that have a really wide D-shaped getter wire; almost as wide as the mica disk. They have thinner lows, don't break up as easily, and are very, very clear/articulate. Excellent tubes, but a different sort of character. Another identifying feature of these earliest versions is that the black plates are not dull/flat finish, like the '50s version. Nor are they shiny, like Sylvania and Raytheon black-plates. These earliest RCA 12AX7 have a semi-gloss finish (or is it eggshell? :wink: ) that is unique.

- Thom

Thanx guys for your answers. Can't wait to try them in the TA and several DIY amps ! (I'm on a Mesa/Fender 3 channel amp project that will soon be finished).
Just won yesterday another auction on Philips 12ax7, 1966

Thom.... JUST SEND ME THOSE MULLARDS !!!! :mrgreen:

They often sound great in bass amps and as stated fantastic for cleans.

Those are the real deal alright...I grew up looking at those, and most other US and Euro brands of preamp tubes when my father (who got me into Ham radio and electronics at an early age) had a desk drawer full of hundreds of these.

He kept them for decades and then, just a few years ago, threw them out without talking to me first.
(You guys may remember this story from an earlier post).
When I told him what they were worth, his jaw dropped to the ground. Now he calls me before he throws out anything electronic! :shock:

Oh well...live and learn. At least I still have my Telefunkens and Amperex's!
Enjoy!

I think you'll like them - I have some RCA 7025's in my heartbreaker and really love them

ty

RCA 7025's are badass!

I bought a repair mans NOS box of five. They were from 1967 date code BL.
These tubes tested great. One had matched triodes @ 99%/1.2 mA emissions
with triodes 1/1700 2/1700uMh, with a noise grade of phono grade on my Ampli At-1000.
Three others were very close to these, I mean 98/97% and 1600ish to 1700 ish ect.
The fifth one triode 1 Was 92%/1.1 mA 1330 triode 2-88% 1.2 ma 1290.
Just barely missing phono grade which is still perfect for most any preamp tube.
I have one in V2 of my road king, I find that although the tube is quiet, the tone
isn't what I like in V1, yet dropping one in the second socket really helps the noise from the high gain
in third gain stages of all four channels. Still have two for later dates
/cheers


Yet the ones on ebay could be bad tubes, poor repair pulls, at any price a tube is NOT a good deal if it is a bad tube.
No matter what brand, year, model, a bad tube is a bad tube, so if you put those blackplates in your amp
please do not judge them if they sound "thin" "weak" "noisy" ect, if you dont buy known good tubes! You MAY
score a deal, but alot often end up with a pull from a repair. I know some have claims of finding a few treasures cheap, but for every one of those there are probably 100 very poor ones people bought.
There are some great sellers on ebay, yet there are some that are repair people selling pulls. Some indicate that, some don't.
Some even give you a single button test, it might be better than no test, but those single button testers that say "good'
mean very little.

I can learn to co-exist
with anything but frustration

LerxstLee said:

I bought a repair mans NOS box of five. They were from 1967 date code BL.

Click to expand...

Though there were long black-plate 7025 made by RCA, the ones you are talking about would be short gray-plate. The black-plate and gray-plate RCA 7025 sound quite different from each other.

It helps prevent confusion to identify which type you're discussing.

- Thom

Timbre Wolf said:

Hi Crane!


Mavguy knows those tubes well. Watch for microphonics (or use as phase-inverter if microphonic). If not microphonic, they do have very clear cleans. Nice fat lows, good, robust mids, bright highs that stay articulate - excellent valves. I actually am learning to prefer these to long-plate Mullard 12AX7, since the RCA carry the heavier lows without accentuating nasal low-mids that the l-p Mullards do (I'm more sensitive to that now, and the Mullards are back in storage). In certain amps, the early breakup of the b-p RCA can be too raw and thick. They've given me an icky feel, kind of like ripping thick construction paper, when driven hard in certain amps. So try in several positions in different amps. You'll find a place for them, no doubt.

Now those are mid-'50s black-plate RCA. There are also RCA 12AX7 from the late-'40s (RCA produced the first 12AX7) that have a really wide D-shaped getter wire; almost as wide as the mica disk. They have thinner lows, don't break up as easily, and are very, very clear/articulate. Excellent tubes, but a different sort of character. Another identifying feature of these earliest versions is that the black plates are not dull/flat finish, like the '50s version. Nor are they shiny, like Sylvania and Raytheon black-plates. These earliest RCA 12AX7 have a semi-gloss finish (or is it eggshell? :wink: ) that is unique.

- Thom

Click to expand...

Those look just like an RCA I bought a few days ago.
It did sound great but the microphonics kept getting worse so i pulled it out and put a jj in it's place and I don't like it very much.
So.... If I put the RCA in the phase inverter slot, it won't squeal? How much does the phase inverter slot effect tone? Is it the only slot that isn't affected by a microphonics tube?

Tmuggie said:

So.... If I put the RCA in the phase inverter slot, it won't squeal? How much does the phase inverter slot effect tone? Is it the only slot that isn't affected by a microphonics tube?

Click to expand...

You'll be able to tell a difference if you use it in your phase inverter. That's the most sure position that won't exhibit microphonics, but there may be others, between V1 and the PI. Just try your RCA there, and let your ears (and sense of touch) tell you all you need to know about whether it is right for you.

- Thom

RCA's are awesome. I just replaced all the JJ's in the preamp section of my VHT with
some RCA's and the PI now has a NOS Mullard CV4024 in it. Sounds soo much better,
smooth, organic. Love'm. I have some old Sylvania's that sound really good too. Now,
as soon as my Weber Bias Rite arrives, I intend to replace the JJ EL34L's and really
bring it to life. Haven't decided which power tubes yet. Back to the thread, if you
find some good RCA's they are definitely worth it!

Sorry, still haven't had time to test them, I've left my band and had a lot of work for now, and "pour courroner le tout" (in french) I'm on an amp conception and construction. But as I've read your comment I'm so excited (yes) to test them !

Oups... never gave a feedback about those fantastic tubes !
Great great cleans, well balanced, no harsh highs, and kind of raw overdrives in a simple circuit. They open up the sound compared to current production, long plates are probably involved in that.

crane said:

Oups... never gave a feedback about those fantastic tubes !

Click to expand...

That was a long pause between breaths! :wink:

- T

Timbre Wolf said:

crane said:

Oups... never gave a feedback about those fantastic tubes !

Click to expand...

That was a long pause between breaths! :wink:

- T

Click to expand...

It was a long time .... :wink:

Glad that they are well liked! Two thicknesses of one inch heatshrink over the sides of the bottle helps the microphonic situation after running 10 minutes or so. The material gets more rubbery and damp-y when it gets hot. Some of the tube coolers out there do a good job at reducing microphonics, notably IERC and Pearl.