DIY Valvecaster. Tube selection problem.

[nguitar12]

Hi everyone I am going to DIY Valvecaster tube booster circuit



This circuit is originally using 12AU7 tube. Just wonder if 12AX7 will also work in this circuit? What I mean is can I socket the tube and experience both tube Dose they share the same pinout? Many thanks.

[PRR]

> if 12AX7 will also work

Probably not.

This is VERY low voltage, you need a very fat pipe to get enough current to do any good.

Of course you WILL socket the tube. Not just because tubes fail, but because careless soldering on tube pins will crack the seals and let the magic vacuum out.

[nguitar12]

> if 12AX7 will also work

Probably not.

This is VERY low voltage, you need a very fat pipe to get enough current to do any good.

Of course you WILL socket the tube. Not just because tubes fail, but because careless soldering on tube pins will crack the seals and let the magic vacuum out.

So 12AU7 is selected just because this is a low voltage circuit and  12AU7 can be run off low voltage. Beside from the operating voltage. Can12AU7 and 12AX7 replace with each other?

[amptramp]

So 12AU7 is selected just because this is a low voltage circuit and  12AU7 can be run off low voltage. Beside from the operating voltage. Can12AU7 and 12AX7 replace with each other?

They can be plugged into the same socket but that's about it.  The 12AX7 is a high-gain low current tube with a µ of 100 and plate currents of 0.5 to 1.2 mA.  The 12AU7 is a medium-gain tube with a µ from 17 to 20 and plate currents of typically slightly over 10 mA.  Another good choice would be a 12AT7 with a µ of 60  and plate currents from 3 to 10 mA.  The 12BH7 is a higher-power tube with twice the heater current that can be run at low voltages.  In fact, I have seen a design for a 12BH7 grid-dip oscillator that was designed to operate off a 12 VDC supply for use with automotive mobile radio operations but there were no plate resistors - it used coils.  There are a number of car radio tubes from the 1950's that operate strictly from 16 or 30 volt maximum plate supplies and the 12U7 is one of these with a µ of 20.

One tube worth trying would be a 20EZ7, a clone of the 12AX7 with a 20 volt 0.1 amp heater.

[nguitar12]

So 12AU7 is selected just because this is a low voltage circuit and  12AU7 can be run off low voltage. Beside from the operating voltage. Can12AU7 and 12AX7 replace with each other?

They can be plugged into the same socket but that's about it.  The 12AX7 is a high-gain low current tube with a µ of 100 and plate currents of 0.5 to 1.2 mA.  The 12AU7 is a medium-gain tube with a µ from 17 to 20 and plate currents of typically slightly over 10 mA.  Another good choice would be a 12AT7 with a µ of 60  and plate currents from 3 to 10 mA.  The 12BH7 is a higher-power tube with twice the heater current that can be run at low voltages.  In fact, I have seen a design for a 12BH7 grid-dip oscillator that was designed to operate off a 12 VDC supply for use with automotive mobile radio operations but there were no plate resistors - it used coils.  There are a number of car radio tubes from the 1950's that operate strictly from 16 or 30 volt maximum plate supplies and the 12U7 is one of these with a µ of 20.

One tube worth trying would be a 20EZ7, a clone of the 12AX7 with a 20 volt 0.1 amp heater.

It sound complicated. I will stick with the 12au7 at suggested. Thanks