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

Distortion analysis mu follower
Distortion analysis mu follower
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 6th April 2005, 07:29 PM   #11
docali is offline docali  Germany
diyAudio Member
docali's Avatar
Join Date: Oct 2004
input voltage was 5mV in order to resemble a phono cartridge. Output level is nearly 500mV or less because the mu of 12ax7 is 100 and the mu follower has an amplification of nearly 100, decreasing with decreasing intermediate resistor.

Changing the load resistor to smaller values is a good idea! I will test it...
  Reply With Quote
Old 6th April 2005, 10:20 PM   #12
EC8010 is offline EC8010  United Kingdom
diyAudio Moderator Emeritus
EC8010's Avatar
Join Date: Jan 2003
Location: Near London. UK
Docali, you really should try substantially increasing R5 (and the HT voltage to suit). As a rule of thumb, R5 should drop about 100V.

As it happens, I was testing some 6SL7 today with an active load (similar to a good mu-follower) and typically measured about 0.15% 2nd harmonic at an output level of 14VRMS. All other harmonics were better than 20dB down on the 2nd. Since distortion is proportional to level, I would expect 0.005% 2nd harmonic to be achieved at your test level of 500mVRMS.
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 7th April 2005, 07:54 AM   #13
docali is offline docali  Germany
diyAudio Member
docali's Avatar
Join Date: Oct 2004
Ok, some variations for the mu follower without coupling capacitor:

First, I lowered the load resistor R4 to 100k as proposed and I tried larger intermediate resistor R6. It should be mentioned that for every load resistor the voltage was atjusted to give nearly the same current and the only difference is the voltage to be dropped across the intermediate resistor. This procedure was also used for all previous investigations.

But the result is the same. The second order distortion undergoes a minimum.

What could we learn from this? The mu follower with coupling capacitor with respect to distortion should have an intermediate resistor as large as possible but if we remove the coupling capacitor of the lower stage things change and we have an optimal area of intermediate resistors with respect to second order distortion.
Attached Images
File Type: jpg mu_12ax7_wocc_2nd_l100k.jpg (53.1 KB, 316 views)
  Reply With Quote


Distortion analysis mu followerHide 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
DIY Distortion Analyzer/Analysis? mlloyd1 Equipment & Tools 152 18th November 2016 11:58 PM
Scaling voltage waveforms for distortion analysis okapi Everything Else 1 10th September 2008 02:58 AM
SPICE distortion analysis jgedde Solid State 6 8th February 2008 05:57 PM
Distortion Analysis using an Oscilloscope gingertube Tubes / Valves 5 14th November 2007 05:14 PM
Cathode follower distortion results ashok Tubes / Valves 3 20th October 2004 02:19 AM

New To Site? Need Help?

All times are GMT. The time now is 03:09 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