12AX7 What is Mu?

[Justin Thomas]

While I agree that tube operating conditions, etc., can be modified so that their sonic characteristics can be rendered inaudible and indecipherable, tubes <ARE> in sockets, and so are <MUCH> easier to change than the operating conditions...

So, I guess for us peons, it's the only option we have!

That said, I'm not gonna say that all of one sound THIS way and all of another sound THAT way...

Justin

[Enzo]

Alf, I am certain if your meter shows a large difference in the meter reading, you might hear the difference. In my experience, I can tell that by listening, I don't need to get out my tester to know it.

[Jazz P Bass]

This is a picture I found on the internet- Sylvania
This was quality control in the twenties and thirties.


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Sylvania Factory Tour ? Vintage Tube Services

Check out the last photo.
The Tube Crusher.

[Leo_Gnardo]

Check out the last photo. The Tube Crusher.

The good ol' days, no OSHA, no safety goggles, no hearing protection around the pocketa-pocketa machine (noise made as tubes pop.)

[g1]

Check out the last photo.
The Tube Crusher.

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Check out the guys mask... oh yeah, those are for wimps. "pfft, it's only glass dust".

[stokes]

And those pics are just one of the reasons tubes are not produced in this country,lot of toxic waster right there

[Jazz P Bass]

Check out the guys mask... oh yeah, those are for wimps. "pfft, it's only glass dust".

Not to mention thorium, phosphorus, zirconium, titanium, aluminum, magnesium, barium, tungsten, molybdenum, carbon.............

[Alf]

[QUOTE=Jazz P Bass;418733]Sylvania Factory Tour ? Vintage Tube Services

Thanks for that link! Apart from all the obvious health hazards the emplyees had to endure I love pictures and info about tubemanufactoring in the old days.

My hometown is Eindhoven ( NL) where Philips Tube and lighting factories used to be, that might explain my fascination. It's all disappeared now (the tube factories, I mean ).

Here's a picture of the main buildings but there were factories all over Eindhoven.


These were the very best of their El34 production. ( Metal base )



Alf

[km6xz]

And those pics are just one of the reasons tubes are not produced in this country,lot of toxic waster right there

The only reason they are not produced in the US is that there is no viable market worth the investment in tooling and automation. The "toxic" materials are not hard to handle, they are mild compared to the materials used in other more profitable fields. Heck, most toxic stuff is sprayed on all our food products with little or no regulatory oversight. Industries, particularly food additives are only tested by the manufacturers and their internal report of the tests results are good enough for the regulators who don't want to rock the boat and mess up the high paying job waiting for those who cooperate.
With a world wide annual sales of only about 4,000,000 tubes no one is interested in such a small payday.

[Jazz P Bass]

Check out the guys mask... oh yeah, those are for wimps. "pfft, it's only glass dust".

Not to mention the OSHA approved guards on all of the 'pinch points'.

[Steve A.]

About 15 years ago I had an HVAC service call from a local church with a problem with their zone control. It turned out to have Barber-Coleman controls from the 50's driven by two vintage Mullard 12AX7's! I was drooling as I drove home to grab a pair of Chinese tubes that I had pulled out of one of my guitar amps.

Alas, when I tried out the tubes they were nothing to write home about. As I recall the sound was very feeble.

On a positive note, the church did say that their zone system was working perfectly.

Steve Ahola

P.S. I buy used old stock tubes from sellers on eBay who often include tester ratings which supposedly indicate that they have plenty of life left. I take those ratings with a grain of salt although the tubes usually work out fine. (I guess I really should try them out right away since if there are problems noted immediately most sellers will replace them.)
In any case I usually prefer used old stock over the current generation of new tubes. (I spent my 2001 George Bush tax rebate on a whole sh*tload of used tubes from any internet seller including Telefunken and Mullard.)

[Jazz P Bass]

I have no beef with the Chinese preamp tubes.

I find them to be more consistent than the Sovteks.

[Steve A.]

I have no beef with the Chinese preamp tubes.

I find them to be more consistent than the Sovteks.

I'd normally replace the stock preamp tubes in all of my new guitar amps, rolling tubes until I was satisfied with the sound. FWIW back in the late 90's it seemed to me that the Chinese tubes tended to be a bit harsher than the Russian and European tubes (although definitely consistent.)

In the "naughty auties" my favorite new production tubes were the Groove Tube 12AX7M and 5751M tubes made in China. I was just now looking at other Chinese tubes and see that the TAD 7025's are selling for $47.95. Ouch!

Steve

[Leo_Gnardo]

I was just now looking at other Chinese tubes and see that the TAD 7025's are selling for $47.95. Ouch!

For those who think "more expensive = better tone" that's just terrific. I wonder how the sale of "Northern Electric" MIC 12AX7 tubes has been going, last seen about 3 years ago trading at $60 or more.

OTOH I just installed a JJ 5751 in a venerable tweed Super yesterday. Very affordable, sounded clean and clear. Amp owner beamed in approval. just like that!

[Steve A.]

For those who think "more expensive = better tone" that's just terrific. I wonder how the sale of "Northern Electric" MIC 12AX7 tubes has been going, last seen about 3 years ago trading at $60 or more.

I heard how great the high-end TAD preamp tubes were a few years ago when they were selling for around $25. I was surprised to see that they've doubled in price since then. (I judge by my ears, not my pocketbook!)

I just installed a JJ 5751 in a venerable tweed Super yesterday. Very affordable, sounded clean and clear. Amp owner beamed in approval. just like that!

I was very unimpressed by the Sovtek 5751's available 15-20 years ago and stuck with used old stock and the GT5751M's. My Holy Grail tube was a 5-star GE from the late 50's sent to me by an e-buddy- whenever that would work perfectly in a particular amp and position I'd try swapping in other 5751's to see how they'd compare. (If it was 90% as good I'd leave it in.)

So I was wondering how the JJ 5751's compare with old stock tubes, just to add to my list. FWIW I just ordered 4 old stock GE 5751's from an eBay seller for $72.80 shipped and they sound great to me!

Type 5751 Vintage Tubes for Guitar HiFi Vintage Military Issue Many Avail | eBay

Steve Ahola