Cathode Bypass caps - how to choose? - Page 2 - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

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 23rd December 2008, 05:05 AM   #11
diyAudio Member
dsavitsk's Avatar
Join Date: Jan 2005
Location: Hartford
Originally posted by SY
The LEDs, besides being excellent voltage sources (and very quiet) also give a nice visual indication that current is running through the stage.
They also cost just a few pennies each, and they sound better than even the best electrolytic bypass.
  Reply With Quote
Old 29th December 2008, 08:19 PM   #12
JesseG is offline JesseG  Canada
diyAudio Member
JesseG's Avatar
Join Date: Jul 2005
Location: New Westminster, BC
So, LED bias is as simple as putting a string of LEDs in series to get the desired voltage drop? No Caps?

"If we crashed our cars as often as we crashed our computers, we'd all be dead!"
  Reply With Quote
Old 29th December 2008, 09:19 PM   #13
diyAudio Member
Join Date: Oct 2005

I've been quizzing the helpful folk here on exactly the same thing - read this:

LED cathode bias - how to pick LED?
  Reply With Quote
Old 29th December 2008, 10:14 PM   #14
diyAudio Senior Member
fdegrove's Avatar
Join Date: Aug 2002
Location: Belgium
Originally posted by dsavitsk

They also cost just a few pennies each, and they sound better than even the best electrolytic bypass.

Even better than a thousand uF worth of filmcaps too...
Even twenty five years ago you'd replace electrolytic bypass caps on small signal tubes (2 to 6V drop across the cathode R) with solid tantulum caps or did away with them altogether and used alterantive methods for biasing the grid.

As for leds, you'd better stock up on the older ones. The newer brighter ones aren't all that great. (See EC8010's post on the topic of LED cathode bias, I only confirm his findings).

  Reply With Quote
Old 30th December 2008, 12:17 AM   #15
SY is offline SY  United States
diyAudio Moderator
SY's Avatar
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 2
Frank, as EC said, the new Agilent jobs are quite bright, but have excellent performance. I'm not as convinced as he is that "bright," "new," and "higher impedance" correlate. I've measured about a dozen different kinds of red LEDs and found high and low impedances in new ones, old one, bright ones, and dim ones.
“Instead of Rational Law, objective truths perceptible to any who will undergo the necessary intellectual discipline, Knowledge will degenerate into a riot of subjective visions. . ." - Auden
  Reply With Quote
Old 30th December 2008, 12:55 AM   #16
diyAudio Member
zapnspark's Avatar
Join Date: Sep 2006
Location: Midwest
How about my wildman approach to creating a completely isolated negative (or positive) bias voltage?


  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
cathode bypass caps suggestions please for newbie tmhajw Tubes / Valves 8 7th March 2008 08:19 PM
HELP! Cathode bypass caps keep going... aletheian Tubes / Valves 13 2nd August 2006 03:45 AM
Non-Polar caps to cathode bypass s2kov Tubes / Valves 4 13th September 2004 08:39 AM
Cathode bypass caps? SHiFTY Tubes / Valves 18 21st August 2002 07:27 PM
Cathode bypass cap ? woody Tubes / Valves 2 19th May 2002 05:53 AM

New To Site? Need Help?

All times are GMT. The time now is 09:42 AM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2015 DragonByte Technologies Ltd.
Copyright ©1999-2015 diyAudio

Content Relevant URLs by vBSEO 3.3.2