A Simple Chart

The CV4004 was a British military spec 12AX7 (not the new production type, where the designation means nothing). It was a rugged, high performing low noise tube, usually featuring "box plates". Both the Mullard & Brimar CV4004's are great tubes, though like with any tubes the two types sound a little different (both very good). I really like the Brimar CV4004 in the V2 position of my 4 hole amps. Here (the middle V2 tube) you can see the "box plate" structure WP_20130306_14_40_03_Smart.jpgvery different to the ribbed plates of the (RTC branded) 163 series Mullard tubes on either side of it.
Good call on the GE 12AX7 Cadorman, great sounding tube & very reasonably priced for NOS. They do well in the V1 position of moderately high gain amps.
The Sylvania 12AX7's are another very good performing type that can be had NOS at a decent price. I have a mix of red & green text, medium plate length Sylvania's IMG_20190518_084850.jpg in my 2204/Caswell #39 type amp & they sound really good, great harmonic content. I would recommend both GE & Sylvania to anyone looking for quality NOS 12AX7's at reasonable cost. Cheers
 
Some of the GE tubes are great....in a lot of cases they were made by other manufacturers and rebranded. Learning to read codes and identify unique physical characteristics opens a lot of doors in the NOS tube department.

Regarding 12au7 tubes, I have found them useful in microphone preamps on a few occasions.
 
Trelwheen said:
Some of the GE tubes are great....in a lot of cases they were made by other manufacturers and rebranded. Learning to read codes and identify unique physical characteristics opens a lot of doors in the NOS tube department.
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Re-branding was done by many valve manufacturers, becoming much more common practice in the 70's when a lot of manufacturers we're gearing down. I very much agree on "know your codes & physical attributes".
I have a duet of GE branded Blackburn Mullard (single halo getter) xf2 EL34'sIMG_20190108_073614.jpgIMG_20190124_094533.jpg
The Blackburn code etching can be see on the left tube in this pic. I also have a Philips Miniwatt branded Blackburn EL34 duet, a Valvo branded Blackburn f32 GZ34 & several RTC branded Blackburn 163 series 12AX7's. A re-branded tube usually can be had for less $'s than its manufacturers branded counterpart. Unless buying NOS tubes from a supplier that has bulk tubes, ie boxes of 100 etc, I suggest buying NOS/NIB. Cheers
 
ivan H said:
Re-branding was done by many valve manufacturers, becoming much more common practice in the 70's when a lot of manufacturers we're gearing down. I very much agree on "know your codes & physical attributes".
I have a duet of GE branded Blackburn Mullard (single halo getter) xf2 EL34'sView attachment 32136View attachment 32137
The Blackburn code etching can be see on the left tube in this pic. I also have a Philips Miniwatt branded Blackburn EL34 duet, a Valvo branded Blackburn f32 GZ34 & several RTC branded Blackburn 163 series 12AX7's. A re-branded tube usually can be had for less $'s than its manufacturers branded counterpart. Unless buying NOS tubes from a supplier that has bulk tubes, ie boxes of 100 etc, I suggest buying NOS/NIB. Cheers
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You make a great point regarding rebranded pricing. It really helps bring prices down to earth.

I will never stop being amazed at how many NOS tubes are still out there. We are fortunate that manufacturing really began to outrun the demand for tubes toward the end of the era.
 
Yes, there really is still a lot of NOS tubes out there. Luckily, we weren't a disposable society back then, things were made to last & be serviced & repaired rather than replaced, & audio tubes had so many applications. Also, while the consumer market was moving toward solid state, military's were still using tubes for quite a good while (they'll still work after a nuclear event, & equipment is easily serviced). Cheers
 
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