Tube Rolling w/Crack

[Paul Birkeland]

A microphonic tube in a headphone amp usually isn't an issue.

[jboehle]

I can hear it ring(?) sometimes when I reach over and grab and turn the volume control, even when music is playing.  It only rings for a second or two, but it's kind of annoying.  I don't have this problem with either of the 6080 tubes I have.

[Paul Birkeland]

Yeah, that isn't particularly abnormal. 

[jboehle]

Alright, my ignorance and this being my first tube amp is showing through   I defer to the great Bottleheads and will give it another chance

[JamieMcC]

I can hear it ring(?) sometimes when I reach over and grab and turn the volume control, even when music is playing.  It only rings for a second or two, but it's kind of annoying.  I don't have this problem with either of the 6080 tubes I have.

This is par for the course and the  GEC's are a little more sensitive than others. I don't normally need to change the volume once set so its not a problem and am happy to live with a few idiosyncrasies with these tubes for the results they give.

[Strikkflypilot]

Hey guys, just bought this tube off the bay.
Supposedly a military GEC CV 2523.

[JamieMcC]

I have one just like it 

I took a stab at looking up the codes this is what I think they refer to
 
CV is the common valve name/type

The broad arrow is the UK Government issue mark,

I think the letter codes on the side under the arrow are date of manufacture July 1965

X denotes Director of Electronics Research and Development (DERAD) AIR approval.

Z denotes place of manufacture MO Valve Company, Hammersmith

[Loon]

Bought these a few days ago.

[JamieMcC]

Are they the ones Skylab (headfi) had listed?

[Loon]

Yep.  Also got a nice pair of 5998s from him

[Strikkflypilot]

Thanks, guys, I guess Im in for a treat:)
Will post images when I get them!

Good Job on deciphering the markings, Jamie.
MO is Marconi, right?

[rlyach]

By the way... I hope I didn't waste my money but I purchased this Mullard 6AS7G. I wanted stay pretty close to the original design and I liked the look of this NOS NIB tube. I won't have much to compare it to but I like the getter at the bottom rather than the top. I have not figured out what the extra wide ring is at the top. Anyone know?

[Chris65]

At least the seller listed it as Russian, which is probably what it is. Don't think Mullard themselves made a 6AS7 as that an American designation.

[mcandmar]

They did re-brand tubes, i have a pair of Mullard 6DN7's which they obviously didn't manufacture, but curiously they don't have any country of manufacture written on them.

I would lay money on them being Sylvania tubes, so i assume they were made in the US.

[Paul Birkeland]

Yeah, that Mullard 6AS7 looks identical to your average RCA 6AS7G.