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

A triode driver example

Posted by Tre' on June 25, 2012 at 15:30:26:
I use a 5687 as a driver for my 6b4g SET.
The 5687 has a plate resistance of about 2500 ohms.
I use a CCS instead of a plate resistor so the output impedance (at the plate) is 2500 ohms.
I use the mu output of the CCS. It's output impedance is about 500 ohms.
This is without considering the grid resistor of the 6b4g.
If I use a 10k ohm grid resistor that will change the drive impedance since it is in parallel with the output impedance of the CCS.
10k//500ohms=476 ohms
If I use a 470k ohm grid resistor the drive impedance will be 499 ohms.
If I take the output off the plate and use a 10k grid resistor the output impedance would be 2.5k//10k=2k and the load line for the 5687 would be more vertical and I would lose gain and the harmonic distortion would increase.
a 470k grid resistor give us 2486 ohms and the load line would stay pretty horizontal.
With any one of those, the Miller is fully driven and the -3db point is more than a decade out of the audio band.

Tre'