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

Testing tube for noise
Testing tube for noise
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 November 2007, 10:32 AM   #1
rotation is offline rotation  Slovenia
diyAudio Member
Join Date: Oct 2005
Default Testing tube for noise


I need some EF83 (or EF86) for my tube preamp. When i bought this small pentodes before, i noticed that some of them were very noisy and needed some testing.
This time i found another seller who offers testing so i will ask him to test noise (and maybe microphonics) for me.

I would like to know more about how this test; how it is done, can it be done with the tube tester etc...
  Reply With Quote
Old 7th November 2007, 11:01 AM   #2
Geek is offline Geek
diyAudio Member
Geek's Avatar
Join Date: Sep 2004

The noise test is done by taking a sample from the anode load resistor (or CCS) and amplifing the output to a speaker (or eye tube).

Some testers have settings for this test that more resemble actual operating conditions, rather than "full throttle current" as typically done for life-test.

That simple

  Reply With Quote
Old 7th November 2007, 11:10 AM   #3
rotation is offline rotation  Slovenia
diyAudio Member
Join Date: Oct 2005
Thanks. I expected simple procedure.

But what are the "values" of noise for this kind of tubes? Datasheet for EF86 only tells noise voltage at certain frequencys...Should i ask him to simply send me tubes that showed lowest noise?

  Reply With Quote
Old 7th November 2007, 11:40 AM   #4
jackinnj is offline jackinnj  United States
diyAudio Member
jackinnj's Avatar
Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
Testing tube for noise
with a simple amplifier setup and an RMS voltmeter measure the A.C. output with the input open and shorted -- calculate the ratio take its logarithm multiply by 20 etc. gives you the voltage signal to noise ratio in dB.

Good discussion of tube noise here:

if you were doing this commercially you would probably want to bandwidth limit the measurement -- say from 22 Hz to 22kHz -- or ITU-CCIR486-ARM or A Weight the measurement. Beyond the scope of this discussion.
  Reply With Quote
Old 7th November 2007, 01:13 PM   #5
Tubes4e4 is offline Tubes4e4  Germany
diyAudio Member
Tubes4e4's Avatar
Join Date: Jul 2005
Location: Leverkusen
Hi rotation,

Here is a Link to a DIY tube microphonics tester, in German language, though.

Regards, Tom
If in doubt, just measure.
  Reply With Quote


Testing tube for noiseHide 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
Testing Gm without tube tester zigzagflux Tubes / Valves 20 25th November 2013 05:05 AM
Testing for tube shorts Zero Cool Tubes / Valves 3 31st May 2008 09:48 PM
Tube testing questions zigzagflux Tubes / Valves 3 24th April 2007 12:52 PM
testing distortion/noise on a X'd amp? rif Pass Labs 1 18th August 2004 07:23 PM
learning, building and testing tube amp fragman56 Tubes / Valves 103 11th March 2003 11:53 PM

New To Site? Need Help?

All times are GMT. The time now is 11:22 PM.

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