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Highest true gain production 12AX7 tube


myles_rose

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I just completed a series of tube tests on a number of current production 12AX7 and ECC83 types.

 

Most conventional tube testers do not measure actual gain. They measure things such as emissions or transconductance. Unless one can also measure the plate resistance one cannot know the actual true gain.

 

As a side note, the VTV tube tester which has a scale marked "gain" does not measure actual gain. This scale is some sort of scale that has no actual relationship to any conventional engineering spec.

 

Engineering spec on a 12AX7 states that in a circuit with a TC of 1600, a DC plate current of 1.2 millamps, a plate resistance of 62.5k ohms, and 250 volts on the plates and a 2 volt bias the gain will be 100. Your TC can be lower if your plate resistance is higher and maintain gain as a side note, and visa versa.

 

Typical production 12AX7 tubes today show a gain on average of 75-85 with average typical gain in the low 80s.

 

The JJ ECC83S in this batch (over 100 tubes were tested) had gain of over 90 in most cases, and there were a number of tubes with gain of over 100 in the range of 108+

 

http://www.groovetubes.com/assets/2177_JJ-ECC83S_040507.jpg

 

 

Myles S. Rose

www.guitaramplifierblueprinting.com

www.la-economy.blogspot.com

www.facebook.com/mylesr

www.twitter.com/myles111us

 

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Ok, Myles, in English for use ignorant players..

 

How does the gain factor in to real world timbre adjustments. Does it simply add more distortion for those in love with hi-gain amp sounds or are there other considerations that make increased gain from the tube desirable in instances other than balls-to-the-wall, hard rock/heavy metal guitar sounds?

It's easiest to find me on Facebook. Neil Bergman

 

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Ok, Myles, in English for use ignorant players..

 

How does the gain factor in to real world timbre adjustments. Does it simply add more distortion for those in love with hi-gain amp sounds or are there other considerations that make increased gain from the tube desirable in instances other than balls-to-the-wall, hard rock/heavy metal guitar sounds?

 

It sounds more closely to what the amp was designed to sound like in the case of vintage amps. In the case of some new amps with their noisy and complex circuits ... mmany of these moderately priced amps were designed around current production tubes that are sub-par.

 

In any case ... to me, they always sound better, are more fun to play and more lively and touch sensitive.

 

Myles S. Rose

www.guitaramplifierblueprinting.com

www.la-economy.blogspot.com

www.facebook.com/mylesr

www.twitter.com/myles111us

 

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Is higher gain actually "better"...or just another "flavor"?

 

Not sure if it's a relative comparison....but a lot of guys like high output pickups...I prefer lower output pickups.

 

See my post reply above

 

Myles S. Rose

www.guitaramplifierblueprinting.com

www.la-economy.blogspot.com

www.facebook.com/mylesr

www.twitter.com/myles111us

 

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Ok, Myles, in English for use ignorant players..

 

How does the gain factor in to real world timbre adjustments. Does it simply add more distortion for those in love with hi-gain amp sounds or are there other considerations that make increased gain from the tube desirable in instances other than balls-to-the-wall, hard rock/heavy metal guitar sounds?

 

It sounds more closely to what the amp was designed to sound like in the case of vintage amps. In the case of some new amps with their noisy and complex circuits ... mmany of these moderately priced amps were designed around current production tubes that are sub-par.

 

In any case ... to me, they always sound better, are more fun to play and more lively and touch sensitive.

 

Valuable information. :thu:

 

Thanks, Myles. :wave:

Don

 

"There once was a note, Pure and Easy. Playing so free, like a breath rippling by."

 

 

http://www.soundclick.com/bands/pagemusic.cfm?bandID=574296

 

http://www.myspace.com/imdrs

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