Audio Asylum Thread Printer

Get a view of an entire thread on one page

FAQ / News / Events

Tubes Asylum

RE: The most expensive 12AX7s - TFK, Mullard, GEC.....

92.184.100.96

ivan_terrible

In Reply to: RE: The most expensive 12AX7s - TFK, Mullard, GEC..... posted by andy evans on July 01, 2024 at 08:57:53

Nothing special.
Yet another scam.*

Another is trying to palm them off for 500 quid a pair with this speel.
this is a valve to die for!
xxx is proud to have some of these rare gems

GEC didn't make many 12AX7, preferring to use their own numbers like Brimar. eg. B339

ie.
Why compete with Mullard who made bazillions of the darn things?

There are also the 7025 and the multi .ax7s in the 12 pin TV valves like the Compactrons used in Ampex etc or in the 7247?
They cost peanuts & are excellent quality.
Bet not many people have tried to use them.

Other things were made also.
eg.
The Mullard ECL83, or UCL83 which is not a well known pentode - considered to be for cheap old record players/TVs etc, was actually made with Brimar-called the HN3x9, with a 12V heater for car radios. (I have a few NOS).

The pentode section has a gain somewhere close to the old 6V6, but with much lower Pa than the (noval) xBW6 and half the height.
It's the half height bit is the attraction.

They always ran HOT, but the pentode can be wired as a power triode, which of course is undocumented like most interesting stuff.

As a power triode, the UCL83 thing will drive a 600 ohm type line no worries,-great for headphones!

The actual triode section is similar to the 12AX7 or more like the 5751, but with Ra of 34K ohm. That's high gain low impedance -

The 12AX7 is double that at 62k ohm, while the 5751 is lower at 58K ohm.
All will sound quite different if wired into a similar circuit.

Probably the most interesting .ax7 oides are found in the 6EU7, which is a much better quality valve - but requires rewiring the socket.

FYI, some nut tried to sell me some diode/rectifiers claiming the sound was astonishing with them.....
Here is the claim:-
"22DE4 Raytheon NOS Vacuum Tube - Proven working - Beyond rare."
yea right!

*Beware!
The scammers are out there, claiming everything is rare and exciting!
There is no scammer worse than an EBAY scammer!

Follow Ups:

Where's My Thumbs-Up Button? (nt) - Triode_Kingdom 02:14:15 07/02/24 (2)
nada aqui
- RE: Where's My Thumbs-Up Button? (nt) - ivan_terrible 08:52:07 07/02/24 (1)
  Thumbs up/down....
  ha, you wanna see the stuff I found on the DB110 thread and more!
  
  It's the case, that under test, very few amplifiers actually deliver the claimed performance - these being from so called "golden era".
  
  I rest my case against all the scamming going on for both the amps and the valves.
  The amps typically always deliver about HALF the claimed output with double the claimed distortion - particularly IMD.
  
  I wouldn't like to imagine anything from PRC or modern RU production....
  
  When I buy brand new NOS stock supposedly "pure gold"(made in England).
  The production spread was enormous.
  
  eg.Out of 250 NOS pentodes, I get static idle currents varying from 50-150% and these were GEC best ever.
  Making matched pairs is real mess.
  
  Same from STC MIL SPEC beam tetrodes. 2 of them arced over at startup.
  Out of 15 NOS I could just about make a matched quad, with 2 rejects.
  oh well!
  
  here's a good NOS one that worked sitting next to it's perfect 70yr old JAN friend from the 40s.
  The 254m has a smaller top cap so alu foil has to make up the size diff.
  
  Here of course was another (EBAY) numpty who sold me this DOA KT8.
  
  When I ran the other 4, (supposedly new but not) the ceramic had expanded and torn the wires out of the base pins, requiring total dismantlement, resoldering etc to stop the constant intermittent contacts taking place.
  (drove me crazy for my 250 quid spent!)
  
  'nuff said eh?
  - Yep, Been There - Triode_Kingdom 14:56:00 07/02/24 (0)
    I lost a good deal of money on defective NOS 211 tubes about 20 years ago. I've been a lot more careful since then, and in conjunction with eBay's revised return policies, haven't experienced anything like that again. About the older gear, you are correct of course that much of it didn't meet the output power claims. The situation worsened when all the major manufacturers moved to solid state, which is why the FTC eventually got involved here in the U.S. Personally, I don't care much whether a 60-year-old tube amplifier makes 20 watts instead of 25 watts. It's the sound I want. :)

Post a Followup:

FAQ

Post a Message!

Forgot Password?

Moniker (Username):
Password (Optional):
	Remember my Moniker & Password (What's this?) Eat Me
E-Mail (Optional):
Subject:

Message:	(Posts are subject to Content Rules)

Optional Link URL:
Optional Link Title:
Optional Image URL:
Upload Image:
E-mail Replies:	Automagically notify you when someone responds.

To view your new posting or follow-up, click on the RELOAD or REFRESH button on your browser.

This post is made possible by the generous support of people like you and our sponsors: