Detailed and Dry. - Page 3 - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs 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

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 9th April 2004, 06:52 PM   #21
diyAudio Member
Join Date: May 2003
Location: Midwest
Default Yes Sy

Might call it a constant (although no tube is perfect). u=gm rp shows that, help our newbie friends. If we can keep u and gm constant, then rp will remain the same and the load lines in quadrant 1 would look great, quadrant 3 transfer characteristics would also be a straight line. Both would have great significance.

By contrast, typical tubes, and more revealing, variable mu or remote cutoff pentodes are variable in that all three parts of the formula are changing because of design considerations of the tube. Any good tube manual will explain the processes envolved if one wants to delve more deeply into it.

Anyway, back to work.

Good info to bring up Sy. Thanks and take care.

  Reply With Quote
Old 9th April 2004, 07:00 PM   #22
diyAudio Senior Member
fdegrove's Avatar
Join Date: Aug 2002
Location: Belgium

Any good tube manual will explain the processes envolved if one wants to delve more deeply into it.
Varying the grid wire pitch is what triggers the variable mu.

  Reply With Quote
Old 9th April 2004, 07:15 PM   #23
diyAudio Member
DrDeville's Avatar
Join Date: Mar 2004
Location: Tucson AZ / Saugatuck MI
Originally posted by EC8010

Hello, thoriated. But can you afford probes that maintain that 500MHz bandwidth to the probe tip? (I can't.)

As Frank says, grid-stopper values are heavily dependent on layout. I recently had to resort to 10k on a point to point layout (great for audio, less great for RF), whereas the PCB equivalent got away with a few hundred Ohms...
Hi EC,

So how do you select your grid-stopper values? By ear, scope, both?

Thanks for an interesting discussion.


George Ferguson
  Reply With Quote
Old 10th April 2004, 12:26 AM   #24
EC8010 is offline EC8010  United Kingdom
diyAudio Moderator Emeritus
EC8010's Avatar
Join Date: Jan 2003
Location: Near London. UK
Originally posted by DrDeville
So how do you select your grid-stopper values? By ear, scope, both?
Good question. Both. My oscilloscope claims 300MHz bandwidth at its input BNCs, and the (original) probes claim to extend that bandwidth to the probe tip, but a few pF can make a huge difference to a circuit that's on the edge of oscillating at 100MHz. Fortunately, circuits that oscillate at more than 100MHz tend to be affected by anything that contacts them, and if you listen to their audio output whilst touching them with a probe (or even the blade of an insulated screwdriver) they tend to make more crackles and pops than you would expect, and that can be a pointer that something nasty is going on that your 'scope can't quite see.
The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...
  Reply With Quote
Old 10th April 2004, 06:48 PM   #25
diyAudio Member
Join Date: Nov 2003
Location: flyover country
Hi, ec8010 -

Sorry for the delay in responding, but the scope probes I used came with the 500Mhz scope, so I presume they're good for the full bandwidth.
  Reply With Quote


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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Detailed plans for 206, 207 or Jordan johnb Full Range 31 8th August 2010 11:18 AM
Where can I get a detailed descriptiong of PWM in Class D xuhaoz Class D 0 1st November 2006 08:00 PM
Fast and detailed midbass unit Rocky Multi-Way 35 22nd May 2004 07:35 PM

New To Site? Need Help?

All times are GMT. The time now is 12:42 PM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2