Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

Very basic grid question????
Very basic grid question????
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Thread Tools Search this Thread
Old 7th January 2011, 07:12 PM   #1
Hilly-wa is offline Hilly-wa  United States
diyAudio Member
Join Date: Feb 2005
Location: Virginia
Default Very basic grid question????

Please look at this data sheet: [URL="http://www.tkhifi.com/datablade/6C45P.pdf"]

The grid is pins 2 and 8, the diagram says pin 2 goes to one side of the grid and pin 8 goes to the other. Are there really "sides" to the grid?

I see lots of schematics that have "grid stoppers" connected to pins 2,8.

What doses 2,8 mean?

If I short pins 2 to 8 and "stop" with a 330 ohm resistor from the short, don't I short out the grid?
Or do I add two resistors, one from pin 2, and another from pin 8?
Or do I have one resister from either pin 2 or pin 8, depending on how my physical layout lends itself to the resistor leads?

I hope this isn't too basic of a question, but I'm at a loss. About a year ago, I cobbled together a 6C45 spud and I shorted pins 2 and 8 and "stopped" with a 220 Ohm resistor. Now when I revisit the schematic, I'm at a loss why the grid isn't shorted out. I no longer have the bread boarded amp to cut the short to see if there is a difference.

I'm never too proud to show my ignorance!

  Reply With Quote
Old 7th January 2011, 07:36 PM   #2
DF96 is offline DF96  England
diyAudio Member
Join Date: May 2007
Yes, most valve grids have two sides, corresponding to two support rods. In most cases the external grid pin is attached to just one of these - this is sufficient as the whole grid is metal anyway. Some high frequency valves, intended for grounded grid operation at VHF/UHF, have two or more grid connections externally in order to reduce the inductance of the grid connection - this improves gain and stability.

When such a valve is used for audio it is usually necessary to add a grid stopper in order to deliberately reduce its RF gain and so avoid instability. Many people use both grid pins for audio and then a grid stopper is needed for each pin. I don't know why they do this, as I think a single connection and single stopper is sufficient.

Connecting pin2 to 8 externally is, at audio frequencies, merely paralleling an existing internal connection so does no harm or good. You can use either pin for the grid. 220 ohms seems a bit too small for a stopper - I would use at least 1K. There was some nonsense on here a few months ago about small value stoppers being better, and that seems to have sent people off down the wrong path. If you use both pins then you need a stopper on both pins.

I wonder whether your confusion is caused by the fact that the standard way of drawing a valve grid makes it look like a set of separate bits of metal when in fact it is all connected together. If you use a meter you will find a dead short between pins 2 and 8.
  Reply With Quote


Very basic grid question????Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Question: grid current related iko Tubes / Valves 3 5th August 2009 03:02 PM
Pentode grid question... Brouilly Tubes / Valves 10 28th March 2009 07:02 PM
Grounded Grid wiring question ultrachrome Tubes / Valves 4 17th October 2004 03:36 PM
Grounded Grid Trafo question ultrachrome Tubes / Valves 3 21st November 2003 03:53 AM
screen grid decoupling cap question.... Morse Tubes / Valves 10 21st April 2003 12:29 AM

New To Site? Need Help?

All times are GMT. The time now is 03:14 AM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright ©1999-2017 diyAudio