Identify These 12ax7s

[LPMojoGL]

These are the preamp tubes that have been in my 60s Fender Dual Showman for at least since the early 80s, if not forever. I've compared these to several other preamp tubes, and these rock. They make a JJ ECC83s sound weak n wimpy. They have a stronger, clearer and more 3D sound. Especially the one with longer plates.

The one on the left has longer, smooth plates, with no writing except the # 17 written on one of the plates in pencil. It has this metal grid on top, like crosshairs in a scope, that can be felt by touch through the glass.

The one on the right has shorter plates, still longer than JJs, with some ridges on em, and has "U.S.A. 7025 UI" written on it.

Any ideas what tubes these are? Thanks!!!

[BigPapiFan]

Not sure at all. The one on the left looks like a Telefunken smooth plate. Does it have a diamond on the base in the center of the pins? The right one looks like some RCA variant judging by the flattened sides of the micas and the shape of the plates and rods, but the etched 7025 doesn't look quite the same as RCA, more like GE.

[rockon1]

RCA on the right,yep. Tele or Ei on the left. Like BigPapiFan said look for a diamond embossed inbetween the pins -if so its a Tele. Bob

[Timbre Wolf]

The left one is Telefunken - you can tell by the uniquely thicker halo getter wire. The diamond will confirm, but I'm calling it a positive i.d.

The right one is an RCA, as previously stated - the mica disks are cut straight on two sides, to make parallel flat sides; that is unique to RCA.

- Thom

[LPMojoGL]

Checked the bottom of the left tube. It's very faint if there is a diamond stamp. I can almost make one out, but hard to tell. There is a #1 stamped in the middle of the pins, again very faint.

Two more questions from this info: 1. How would these sound in the preamp of a more modern amp like a Soldano (have a Hot Rod 50+ on the way). 2. Where can I get more?

And a big thanks to you guys. I love this forum!!!

Bobby

[59Vampire]

Since you asked, I dont think a telefunken would do so well in a soldano. neither would the rca. Dang master volume amps

[LPMojoGL]

Originally Posted by 59Vampire

Since you asked, I dont think a telefunken would do so well in a soldano. neither would the rca. Dang master volume amps

I've done quite a bit of researching since my last post. Ignorance is bliss!!! I'm kinda freaked out by how many times I've swapped these tubes for comparison. I even broke the pin off a JJ during comparisons in the Peavey Classic. That could've been the TF. ugh And I let a yellow lettered Sylvania go with that amp. Bummer.

I've decided that the tubes pictured above are staying in the Fender. I think it will benefit more from the clean, full spectrum 3D sound of these tubes than a MV amp like the Soldano that pushes em for distortion tones. I'm starting to get what you seem to already know.

[59Vampire]

Originally Posted by LPMojoGL

I've decided that the tubes pictured above are staying in the Fender. I think it will benefit more from the clean, full spectrum 3D sound of these tubes than a MV amp like the Soldano that pushes em for distortion tones. I'm starting to get what you seem to already know.

Good choice. And welcome to the never ending journey of tube swaps. There are alot of great old production tubes you can get for that Soldano that will surely please you. I dont remeber which series it was and im sure TImbre Wolf can point you in the right direction, but there are some nice Chinese tubes that are great sounding in amps like yours. Look for some Sylvania 12ax7s. They are great in high gain applications in V1. There are a lot of others that you can find. Use the fender with its clean design as a test bed and then swap out. Have fun

[rockon1]

Originally Posted by 59Vampire

Since you asked, I dont think a telefunken would do so well in a soldano. neither would the rca. Dang master volume amps

Well interesting you say that. Ive gone thru a 100(literally) different combinations of old stock pre's in my Palomino V32. I keep coming back to my favorite which is V1- RCA short plate V2- 58 Mullard long plate and V3(PI) Telefunken smooth plate.

The RCA introduces less harmonic richness which doesnt clutter up the tone on its way to the Mullard. Sometimes less is more! The Tele just works "best" in the PI keeping the most punch and tightness to the sound.

Timbre Wolf- Good call on the Tele. Shamefully I forgot about the structure of the clearly visible getter wire. Im turning in my slueth badge....lol! Bob

[Timbre Wolf]

Originally Posted by rockon1

Timbre Wolf- Good call on the Tele. Shamefully I forgot about the structure of the clearly visible getter wire. Im turning in my slueth badge....lol! Bob

I'm sure you were just distracted by something more fun goin' on

- T

[LPMojoGL]

Originally Posted by 59Vampire

Good choice. And welcome to the never ending journey of tube swaps. There are alot of great old production tubes you can get for that Soldano that will surely please you. I dont remeber which series it was and im sure TImbre Wolf can point you in the right direction, but there are some nice Chinese tubes that are great sounding in amps like yours. Look for some Sylvania 12ax7s. They are great in high gain applications in V1. There are a lot of others that you can find. Use the fender with its clean design as a test bed and then swap out. Have fun

Thanks for the advice. I'll be looking for a Sylvania. The Fender does seem to easily reveal the differences between these preamp tubes. I will probably start trying out types of preamp tubes, new and old, cause I can be OCD like that.

Thanks again for all the replies!

[rockon1]

Originally Posted by Timbre Wolf

I'm sure you were just distracted by something more fun goin' on

- T

Unfortunately...yes. On Monday two of my cars got vandalized with paint thinner. Fortunately they were my old beaters. (Someone that doesnt like my son actually admitted to it -only to him though). Friday I got a repeat performance and one of my tires was slashed and the hood was paint thinnered again....Hows that for a distraction!

[Timbre Wolf]

Originally Posted by rockon1

Hows that for a distraction!

Not fun. Sorry you're having to deal with a lunatic.

- T

[BigPapiFan]

Anyone have any insights about the strange lettering on the RCA "7025?" The typical RCA 7025 that I have seen have different lettering in an elongated octagon:

[Timbre Wolf]

Originally Posted by BigPapiFan

Anyone have any insights about the strange lettering on the RCA "7025?"

There were two tube companies that used stencil-style lettering/numbering on their tubes: GE and Westinghouse. Generally, Westinghouse seems to have used Sylvania-origin inner assemblies in their own tubes (12AX7 short gray-plate/square-getter), and it is conceivable that they did the same with RCA assemblies - but that is a stretch, and I've not encountered that type to be able to compare the sonic characteristics. I'm 100% confident that the micas are RCA origin - no one else made those. But I can't guarantee that Westinghouse didn't purchase assemblies and do the final production.

- T