A little more information

The two main activities in my life: Helping the hungry in the late hours of the night and helping guitar players sound better one amp at a time.

I always try to remember that in order to do good one has to take action and actually do something.

I was born and raised in Los Angeles. I have watched the city and Southern California change for well over half a century.

I can be found on facebook at www.facebook.com/mylesr or on twitter at www.twitter.com/myles111us or on my own Guitar Amplifier Blueprinting website at www.mylesrose.com

Los Angeles Architectural History

Los Angeles Architectural History
1935 Art Deco at some of its finest: No. 168 - Griffith Observatory- (click on the photo for information)

Friday, February 24, 2012

Tube Test - 12AX7 Tung Sol Reissue

This was the last run in January 2012 of the Tung Sol Reissue that I performed at the request of Dan Boul over at www.65amps.com

This is the current "Tung Sol" tube from New Sensor.  This is the tube which was tested
To see the full story click on "read more" below

These are actual Tung Sol 12AX7 tubes
New Sensor has purchased the rights to use many of the great tube makers names from the past.  Tung Sol is one.  The name Mullard, Svetlana, Gold Lion are just a few of the others.

Generally, I have found that the tube from New Sensor bears little resemblance to the original design.  Is this good or bad?  That is your own point of view.  From my point of view I would not care what name was placed on a tube if it were a good tube.  

The New Sensor "Tung Sol" is something of an offshoot of the older Electro Harmonix 12AX7.  Groove Tubes used to sell that tube as the 12AX7R3.  It was one of the best current production 12AX7 tubes at the time but sales slowed due to high cost compared to some other 12AX7 tubes.  When sales slowed New Sensor gold plated the pins of the 12AX7EH and raised the price again but some folks bought the tube in the new gold pin form.  As a side note, gold pins are vacuum plated, ultra inexpensive to do and offer no benefit as any slight corrosion that might develop on some tubes in long term moist storage will be scraped away during insertion.  The plating is also so thin that the dissimilar metals of the pins and the socket pins will not be helped by gold pins on the socket side as it is scraped away.  If you are concerned about corrosion use a proper product on the pins to clean them such as De-Oxit.  Spending many more dollars on the same tube with gold pins in my own opinion is just foolish. 

Sales slowed on the 12AX7EH so with a few minor tweaks the 12AX7 Tung Sol reissue was born.  Compare it physically to the 12AX7EH and you may see many similarities.  Compare either to the long plate actual Tung Sol and other than them both being glass tubes with nine pins there is little to compare physically.

By the way, for about $10 more than non gold pin version you can have the same  tube in a gold pin version.
Bottom line though is that the current tube performs nicely and is one of the best current 12AX7 tubes on the market.  It still does not compare to NOS in specs, consistency or life but sonically it is an articulate and neutral tube that works quite nicely in many applications.

If you click on this image you will see a larger version

Thank you to the folks at 65 Amps for being as picky as they are about the tubes they put into their amplifiers and requesting tests such as this one.
The original Tung Sol 12AX7 data sheet can be viewed here:

There are a number of tube suppliers out there.  These are a few of the folks that I personally use and trust.  They have good prices and test properly.



  1. What equipment is being used to collect this data?

  2. Various vacuum tube development and engineering devices. If you are familiar with things like the RCA WT-100, Tektronix curve tracers, HagTech and these types of devices than you will understand some of the procedures.

  3. If you are in the Los Angeles area I would be happy to have to look at the procedure as I do the various tests.

  4. I just posted some links and photos on my facebook wall that gives a lot of info on some of the tools and procedures I have used for many years.

  5. That's kind of you to offer, but I'm a little far from LA, in Cincinnati. I was interested in how accurate your data maight be, and it sounds like you have some good tools to do this testing. IMO this is the way to put pressure on the manufacturers, and so much the better if it's comming from amp manufacturers who consume a large number of tubes. It would be useful to calculate standard deviations for the measured parameters and express variation that way, along with the mean shift (in std dev) from the target spec.


    Martin Manning

  6. Martin,

    I have run these tests and reports since 2002 when I would do them at Groove Tubes. The reports are available to the manufacturers and JJ and Shuguang used to take them into account on a regular basis.

    The design specs are defined and have been for decades. If the makers want to shift the spec then they need to call a tube something else rather than used a defined label such as 12AX7.

    Some tubes meet spec today once in a while. By accident. The tubes produced are above spec and below spec, all over the map. No QA no QC.

    In your area there is a fellow who I have known for many years who is a great friend, Michael Zaite. He is the owner and founder of www.drzamps.com (Dr. Z Amplifier) who is also somebody I work with on a regular basis as I do with the folks at 65 Amps and a number of other amp makers and audio folks.



  7. Z is a few hours north of here, but I've crossed paths with him a time or two on-line. Seems like a great guy.

    Here's a slightly different look at the TS reissue data you collected:

    The mean of the sample relative to the spec values is:

    Ia -13%
    gm -5%
    ra -7%
    mu -12%

    Using standard deviations corrected for small sample size, one could predict that 95% of the production would fall within the following percentages of the true production averages:

    Ia +/-27%
    gm +/-12%
    ra +/-14%
    mu +/-5%

    Not too much different, but this suggests a little wider spread than the range "QA" that you reported.

    Have you ever had the chance to do similar testing on a sample of NOS 12AX7's?

    Martin Manning

  8. Martin,

    There are different ways to input the data and do the math. The bottom line is to try to be consistent.

    On NOS tubes... you bet I have done this. The list is growing all the time. I plan on publishing that list in the near future.



  9. Myles test's are both trusted and respected by the Dr Z gang for sure...
    I know, I am one of them.

    We consider his extensive tube knowledge, and posted data on various tubes a value add to the site for sure.

    Keep up the fine job Myles!
    You have earned our respect


  10. Scott,

    Thank you for the kind words.


  11. Finally a good review.
    Thank you !