Testing Tubes

[Spectrum13]

1313,

 

When a tube tests on a Hickok... say a 12ax7 if it says Min+1250 Max+ 3000

 

say it reads 1675/1675 is that saying the increased voltage is within specs but 3000 would be the greatest increase in voltage so 1675 is like some % >50 of total boost? Lower = less head room and the output tubes work harder?

 

What position and on what type of amp does a well balanced tube work best?

 

You appear to be pretty knowledgable, TKS in advance.

[slider313]

1313,

 

When a tube tests on a Hickok... say a 12ax7 if it says Min+1250 Max+ 3000

 

say it reads 1675/1675 is that saying the increased voltage is within specs but 3000 would be the greatest increase in voltage so 1675 is like some % >50 of total boost? Lower = less head room and the output tubes work harder?

 

What position and on what type of amp does a well balanced tube work best?

 

You appear to be pretty knowledgable, TKS in advance.

 

The Min 1250 is the low end number of a good tube and the Max 3000 is the high. This shows the tube is within spec, with consideration to working parameters of a 12ax7. I find the higher the number, the more microphonics show up and the earlier the tube will break up. The lower the number, the more headroom and usually less microphonics. There is no increase in voltage from a tube, only from different components in an amps circuit and while one 12ax7 may sound great in a tweed Deluxe, it may sound terrible in a Deluxe Reverb. The only real way to tell how it will sound and work best is to install it in the amp and A/B it with what's in there now.

[Steiner]

The Min 1250 is the low end number of a good tube and the Max 3000 is the high. This shows the tube is within spec, with consideration to working parameters of a 12ax7. I find the higher the number, the more microphonics show up and the earlier the tube will break up. The lower the number, the more headroom and usually less microphonics. There is no increase in voltage from a tube, only from different components in an amps circuit and while one 12ax7 may sound great in a tweed Deluxe, it may sound terrible in a Deluxe Reverb. The only real way to tell how it will sound and work best is to install it in the amp and A/B it with what's in there now.

 

I thought the function of the preamp tubes (12AX7, etc) was to provide a voltage gain.

 

I concur with the empirical test. The same tube in different amps will give different results; that's what makes those noisy heaters (amps) so special!

 

Spectrum13, I know you addressed triskaidekaphobia-squared but the short answer is the first valve position (V1) will grant the greatest sound variation to various preamp tubes. You can swap them out while the amp is in stand-by without harming the circuit. Have fun! Experiment!