quiet 12AX7

[ajaxon]

I need to find a super quiet tube for my SWR Bass750. Any suggestions as to what brand?

Also is there any difference in a 12AX7 and a 12AX7A?

Thanks

 

[Rick Auricchio]

All tubes will vary in their noise level. It may take some experimentation to find the quietest one from a batch. Even in the same brand there will be variations.

There are a dozen variations of the 12AX7/ECC83 tube. The "A" is typically the low-noise version.

Here's a good comparison chart: Invalid Link Removed

 

[okcrum]

More than that, all tubes will get noisier with use. I would go with true NOS Mullard if you really need the lowest noise, but you're gonna pay through the nose for it. You could save 60-80% of your money and get some eBay "NOS" that's 90% as good IME.

 

[Exploiter8]

Here's a good comparison chart: Invalid Link Removed

GREAT link! Thanks for posting.

X8

 

[AwkwardLoudness]

Old stock 12AX7/ECC83 tubes labeled '7025' are spec'd for low noise. I've used GE and Sylvania brand 7025 and they are great. You can't go wrong with old Blackburn Mullards though.

 

[Rick Auricchio]

GREAT link! Thanks for posting.

Google is my friend.

 

[Ben Clarke]

I have an old RCA tube manual that says the "A" suffix indicates that it can be used in parallel filament applications. Whatever that means... Nothing to do with noise.

Look for old GE 5751 as well as 7025.

 

[GeoffByrne]

The current Jan Phillips 5751's are also pretty decent.....

 

[madmachinist]

it may be possible, to sub tubes w/ less gain (12au7 , 12at7,
5751 , etc) without altering the preamp's tone significantly.

also, tubes w/ short and welded plates are said to be less
microphonic than long plate/crimped seams.

 

[MAMMOTHvolume]

go for mil spec

 

[Bassmec]

go for mil spec

Quite so in fact the mil spec Mullard CV4004 is a ruggedized all copper pin all copper traces variant with awesome noise figures
and there is no better 12ax7 or Ecc83 variant.
Expect to pay big bucks as the hi fi nuts are after them.

 

[ajaxon]

What does NOS mean?

 

[okcrum]

New Old Stock - old, but in theory unused.