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

6550 plate resistance in triode mode? Calculate?
6550 plate resistance in triode mode? Calculate?
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 4th August 2013, 06:41 PM   #1
Koektrommel is offline Koektrommel  Netherlands
diyAudio Member
Join Date: Jan 2013
Default 6550 plate resistance in triode mode? Calculate?

For some penthodes (e.g. EL84) a value for the plate resistance in triode operation can be found in the datasheet. Does anyone have an idea what this would be for a 6550? Is there an easy way to estimate/calculate?
"A new idea comes suddenly and in a rather intuitive way, but intuition is nothing but the outcome of earlier intellectual experience." - Albert Einstein
  Reply With Quote
Old 4th August 2013, 06:49 PM   #2
daqvin_carter is offline daqvin_carter  United States
diyAudio Member
Join Date: Apr 2007
Location: Denver CO US
Plate resistance is fairly easy to calculate if you have the troide curves.
Think of plate resistance as the slope of the line with more vertical equaling lower plate resistance.
Notice you have voltage on one axis and current on the other. R=Change of Voltage/Change in Curent.
Find some change of voltage and change of current over a small seciton of the curve.
It is also helpful to notice that plate resistance is not constant and can change depending on operating point.
  Reply With Quote
Old 4th August 2013, 09:47 PM   #3
smoking-amp is offline smoking-amp  United States
diyAudio Member
smoking-amp's Avatar
Join Date: Dec 2001
Location: Hickory, NC
Often the triode configured Mu is published in the datasheet. Since this doesn't change much with V or I, it can be used to calculate the triode rp from the pentode gm (which does change noticeably with current, approximately by current to the +1/3 power, so you extrapolate gm from the data sheet to your op point). Then:

Mu = gm . rp or rp = Mu/gm

(Obviously, rp must also vary with current as the -1/3 power to get Mu constant.)
  Reply With Quote
Old 4th August 2013, 10:14 PM   #4
DF96 is offline DF96  England
diyAudio Member
Join Date: May 2007
Some datasheets give 'inner mu', which is g2 to g1. Triode mu will be similar to this. Triode gm will be bigger than pentode gm because you get g2 current too; multiply pentode gm by (Ia+Ig2)/Ia or for a rough estimate just add 20%.

IIRC there is also 'outer mu' which is anode to g2 (i.e. for g2 drive) but few datasheets give this.
  Reply With Quote
Old 5th August 2013, 12:43 AM   #5
stevenrotterdam is offline stevenrotterdam  Netherlands
diyAudio Member
Join Date: Sep 2006
Depending on operating point, 700 to 1400 ohm. Use Ra 3,5...4,5 k.
  Reply With Quote


6550 plate resistance in triode mode? Calculate?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
Triode plate resistance == internal negative feedback? jcx Tubes / Valves 57 21st July 2016 10:06 PM
6550 internal resistance hit parade speakerfritz Tubes / Valves 0 29th February 2012 06:26 PM
How to calculate mechanical resistance added by enclosure. SoulMagnet Subwoofers 0 10th January 2012 06:25 AM
Looking for Schematic 6550 tube amp triode mode more than 35Watt ? calico88 Tubes / Valves 26 10th August 2009 02:49 PM
Using a spdt switch to select between triode mode and pentode mode on a guitar amp. G Instruments and Amps 19 15th March 2006 09:15 AM

New To Site? Need Help?

All times are GMT. The time now is 07:19 AM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio