Differential amplifier with 12AX7

[zafira1981]

Hello people,

I'm looking for some theory. I want to design a pre-amp with dual power supply and differential stage.

I need some theory, do you have any document explaining how to design a diff amp with tubes? I know how to do it with transistor, but not with tubes.

What about the constant current source? Any circuit of a current supply with tubes?


thanks a lot
Jorge.

[ErikdeBest]

Hi Zafira

Search for baby huey. This is a project from a fellow member, actually a whole power amplifier, but it uses a diff pair with ECC83, which you can use for inspiration.

Erik

[Wavebourn]

Originally posted by zafira1981
Hello people,


What about the constant current source? Any circuit of a current supply with tubes?


thanks a lot
Jorge.

I use transistors. PNP for plates, NPN for cathodes of differential stages.

[zafira1981]

Originally posted by Wavebourn


I use transistors. PNP for plates, NPN for cathodes of differential stages.

I dont understand. I supose that you use the transistors for the current sources, right?



ErikdeBest: thanks, i will search for "baby huey"

[Wavebourn]

Originally posted by zafira1981


I dont understand. I supose that you use the transistors for the current sources, right?



ErikdeBest: thanks, i will search for "baby huey"

No, for breakfast.

[tubelab.com]

There have been several threads here dealing with current sources for vacuum tube circuits. Search around and you will find them.

A current source can be built entirely with vacuum tubes (or with a simple pentode) but they require considerable voltage across them to function. Offten the behaviour is less than ideal.

Many people use solid state current sources in vacuum tube circuits. There is a common circuit that uses two transistors (I am at work so I don't have it handy). There are several current source IC's that are often used. The LM334 (National Semiconductor) and the IXCP10M45S (IXYS) are the ones that I use.