PP CATHODE BIAS WITH "CCS" - 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
Reply
 
Thread Tools Search this Thread
Old 4th April 2013, 08:40 PM   #1
tim614 is offline tim614  United States
diyAudio Member
 
tim614's Avatar
 
Join Date: Jun 2008
Default PP CATHODE BIAS WITH "CCS"

HELLO TUBES WORL,
Cathode Bias with a Counstant Current Source
so, i been doing some reading on cathode bias with CCS and found the artical on tubecad web site.
As i understand from reading the artical. Why is this not more common in tube amp designs? as it seem to be a win win if you want class A with more wattage compare to SET type tube amp?
__________________
Tim
" perfect imperfection "
  Reply With Quote
Old 4th April 2013, 09:18 PM   #2
45 is offline 45  Italy
diyAudio Member
 
45's Avatar
 
Join Date: Dec 2008
Location: UK
Quote:
Originally Posted by tim614 View Post
HELLO TUBES WORL,
Cathode Bias with a Counstant Current Source
so, i been doing some reading on cathode bias with CCS and found the artical on tubecad web site.
As i understand from reading the artical. Why is this not more common in tube amp designs? as it seem to be a win win if you want class A with more wattage compare to SET type tube amp?
Many things that look ok on paper and even on the bench then really don't sound good enough. I really don't like CCS and similar "restrictions" at the power stage. A good power supply with fixed bias (DC coupled cathode follower or source follower or fixed bias with interstage transformer) is the best solution for me. This is especially true for low power (10W or less) amplifiers where I tend to avoid feedback as well.
The main reason is that I want to use all their power and I don't want hard clipping.
  Reply With Quote
Old 4th April 2013, 09:26 PM   #3
diyAudio Member
 
Shoog's Avatar
 
Join Date: Aug 2002
Location: Eire
It works remarkably well, though requires a big cap for bypassing. I have done it many times and generally bypass the cathodes to each other using back to back capacitors to create a differential output stage.
My experience is that in this differential configuration going the extra mile to fixed bias only offers marginal improvement.

A theoretical issue which has been raised is that this only offers DC balance in the output stage and that AC balance maybe worse than with resistive self bias - but I have not found this to be an issue personally.

Shoog
  Reply With Quote
Old 4th April 2013, 10:22 PM   #4
tim614 is offline tim614  United States
diyAudio Member
 
tim614's Avatar
 
Join Date: Jun 2008
thanks guys!
i will try this ccs thing and see what i think. its seem to be worth a try.
__________________
Tim
" perfect imperfection "
  Reply With Quote
Old 5th April 2013, 02:56 PM   #5
tim614 is offline tim614  United States
diyAudio Member
 
tim614's Avatar
 
Join Date: Jun 2008
CCS installed.
The amps are PP kt120 with IT phase splitter.
CCS are set at 86ma per tube, didn't have time today to give it a good listen.
Will report back as soon as I get more playing time.
__________________
Tim
" perfect imperfection "
  Reply With Quote
Old 5th April 2013, 04:23 PM   #6
Yvesm is offline Yvesm  France
diyAudio Member
 
Yvesm's Avatar
 
Join Date: Jul 2004
Location: Ardeche
Had a check at cathode voltage when running at continuous hi power, you may be surprised !
The worst situation is while you measure max power

I usually add a Zener of appropriate power in parallel with each CCS at about 1.5 times the quiescent cathode voltage.

Yves.
  Reply With Quote
Old 5th April 2013, 04:52 PM   #7
tim614 is offline tim614  United States
diyAudio Member
 
tim614's Avatar
 
Join Date: Jun 2008
i have two ccs in parallel for the job to dissapate edaquately.
__________________
Tim
" perfect imperfection "
  Reply With Quote
Old 5th April 2013, 09:00 PM   #8
Yvesm is offline Yvesm  France
diyAudio Member
 
Yvesm's Avatar
 
Join Date: Jul 2004
Location: Ardeche
Right, but I said: beware of the VOLTAGE accross the CCS
  Reply With Quote
Old 5th April 2013, 09:28 PM   #9
diyAudio Member
 
Shoog's Avatar
 
Join Date: Aug 2002
Location: Eire
Your CCS need to be well heatsinked. In many cases this can be just bolted to an aluminum case.
I generally use DN2540 or the IXY 600V or 900V chips for robustness.
I have also had success with TL783 which is a 120V version of the LM317.

I mess about with direct coupled amps and in this configuration the initial voltage spikes at switch on can go to the +B which will take out any lesser CCS. It can be very frustrating when one blows.

Its generally better not to have your CCS the weakest link in the overall chain.

Shoog
  Reply With Quote
Old 5th April 2013, 09:40 PM   #10
tim614 is offline tim614  United States
diyAudio Member
 
tim614's Avatar
 
Join Date: Jun 2008
thanks for all the advice. as i do need it.
this is what i use from k&k
http://www.kandkaudio.com/accessories.html
Cascode Current Source Kit attachable to an external heat sink (up to 20 watts with adequate heat sink)
__________________
Tim
" perfect imperfection "
  Reply With Quote

Reply


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
Balancing the PP cathode bias Tyimo Tubes / Valves 5 5th December 2010 06:49 PM
Triode PP OP stage combining Blumlein Garter and CCS bias - anyone tried this? ray_moth Tubes / Valves 19 27th August 2010 12:43 AM
Gary Pimms "self bias ccs" - guide for dummies andRookie Tubes / Valves 1 13th September 2009 11:03 PM
EL34 pp "fixed" bias is wandering OzMikeH Tubes / Valves 14 6th May 2008 02:17 PM
CCS for p-p cathode bias ? Jozef Tubes / Valves 0 9th January 2004 06:11 PM


New To Site? Need Help?

All times are GMT. The time now is 03:56 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2