Tube DIY Asylum

Do It Yourself (DIY) paradise for tube and SET project builders.

Use this form to submit comments directly to the Asylum moderators for this forum. We're particularly interested in truly outstanding posts that might be added to our FAQs.
You may also use this form to provide feedback or to call attention to messages that may be in violation of our content rules.

You must login to use this feature.

Inmate Login

By default, logging in will set a session cookie that disappears when you close your browser. Clicking on the 'Remember my Moniker & Password' below will cause a permanent 'Login Cookie' to be set.

Moniker/Username: The Name that you picked or by default, your email. Forgot Moniker?	Examples "Rapper", "Bob W", "joe@aol.com".
Password:	Forgot Password?
	Remember my Moniker & Password ( What's this?)

If you don't have an Asylum Account, you can create one by clicking Here.

Our privacy policy can be reviewed by clicking Here.

Inmate Comments

From:
Your Email:
Subject:

Message Comments

Original Message

RE: That's not correct

Posted by Tre' on June 15, 2017 at 20:32:20:
The "2" has nothing to do with where you bias the tubes.
It has to do with how hard you plan to drive them.
When the driver stage is up to the task you can drive the output tubes into grid current (grid positive WRT the cathode). That's the "2" part.
"With the tubes barely on" is Class B (or at least what they call Class B).
The "barely on" part is just to keep the notch distortion down.
True Class B (rarely used for audio) is when the tubes are both in cutoff (not just in the cutoff region but in real cutoff ie; no current flowing) in the absents of input signal.
Now, just to start a flame war, in true Class A the tubes are never allowed to enter the cutoff region (the region approaching cutoff where the linearity of the tube goes to sh_t or the non-linear region close to saturation).
Class of operation is more than just the bias point. It's how the tube is biased, how the tube is loaded and how hard the tube is intended to be driven.

Tre'