CCS for PP Class A output stage? - 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 22nd January 2004, 09:17 PM   #1
diyAudio Member
Join Date: Jan 2004
Location: Minnesota
Default CCS for PP Class A output stage?

I need to build a SS CCS to run at 120mA for my 6B4G PP output stage.

Bipolar or depletion MOSFET??? Cascode or not?


This is of course instead of my shared bypassed cathode resistor.

  Reply With Quote
Old 23rd January 2004, 01:08 PM   #2
diyAudio Member
Join Date: Dec 2000
Location: Germany
Default ccs for output stage

are you working on the ideas of Allen Wright, me to.
Come back to you later. Look at
Think there are useful ccs`s.

  Reply With Quote
Old 23rd January 2004, 03:43 PM   #3
diyAudio Member
Sch3mat1c's Avatar
Join Date: Jan 2003
Location: Milwaukee, WI
Send a message via ICQ to Sch3mat1c Send a message via AIM to Sch3mat1c
Uh.. either will work fine. What do you want to know?

Seven Transistor Labs, LLC
Projects and Resources / Electronic Design and Consultation
  Reply With Quote
Old 23rd January 2004, 03:57 PM   #4
diyAudio Member
Join Date: Jan 2004
Location: Minnesota
Default looking for schematic

just looking for a good schematic...

probably use those DN2540 things...
  Reply With Quote
Old 23rd January 2004, 04:08 PM   #5
316a is offline 316a  England
diyAudio Member
316a's Avatar
Join Date: Dec 2002
Location: West London
Default Re: CCS for PP Class A output stage?

Originally posted by AudioGeek
I need to build a SS CCS to run at 120mA for my 6B4G PP output stage.

Bipolar or depletion MOSFET??? Cascode or not?


This is of course instead of my shared bypassed cathode resistor.

Hello ,
I've been using cascoded DN2540 sinks for the past six months , previously just using a single DN2540 device under output stages . The difference is not too great . Never tried bipolar high-current sinks to make comparisons though . I suppose battery biased mosfets are another possibility , there are plenty of designs on Gary Pimms site to use as reference . For low mu valves like 6B4G I find it best to use variable grid bias from a negative supply and drop about 20V across the sink . This way sink dissipation and HT wastage is reduced . A centre reading meter is connected via resistors between the cathodes so the output stage can be balanced avoiding DC in the output transformer . The scheme sounds far better than any other biasing scheme used to date , I don't use anything else now .

ps Filamant transformers for the 6B4G will need an electrostatic screen otherwise the leakage capacitance will affect operation of the sink

  Reply With Quote
Old 24th January 2004, 02:58 PM   #6
diyAudio Member
Gary P's Avatar
Join Date: Apr 2002
Location: Portland OR

I have been playing with differential output stages for several months now. The versions Iíve been working on use pentodes and local feedback from the plate to the grid of the output pentode.
In this configuration the output stage works as a I to V converter and has the input stage doing the duty of V to I converter. With this setup I'm getting sound quality that is really great. Super fast, clean, and dynamic range that my SE300B amp can only dream about. Frequency response of the differential amp is flat from single digit numbers to -3dB at 165Khz.

One thing to keep in mind when building/tweaking series connected (differential) output stages is that if either tube goes into cutoff the whole output stage current loop breaks. This means that you will want to run the output stage in deep class A, possibly at a higher bias current and lower plate voltage that your would used in a single ended amp. This is just the opposite of the way most P-P stages are setup. The goal is to make sure that when the output stage clips, the clipping happens to the tube approaching saturation. We want the tube approaching cut off to still have a good amount of current flowing to maintain integrity of the output stage current loop.

The amp that is currently under construction will be used to learn more about the interactions in the output stage in differential amplifiers. It will be using EL84's initially. This makes it a better choice for dinking around with than the 47P-P amp. Tubes are much easier to come by and can be operated at any angle.

There are a few CCS designs on my web page that will work for 120ma or more. The mosfets used are good for 50 watt dissipation so are much tougher than the DN2540's 15 watt rating. I also sell the boards to build the CCS's on. There are 2 new versions that have not been added to the web page yet. A new battery biased CCS that uses 27A 12V alkaline batteries that snap into battery clips instead of the lithium cells that solder into the board. And a small footprint CCS (same as the battery biased CCS's) that self-biases using the voltage reference from the Rev 5 CCS.

Here is a picture of the newest CCS's in the family
Click the image to open in full size.
Gary P's DIY page
  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
Testing Class B Output stage Mark245 Solid State 7 27th January 2009 10:23 AM
Aikido + class D in the output stage jmartins Tubes / Valves 2 6th June 2006 08:51 PM
Class A with AB Output-stage ManUtd Solid State 14 1st December 2003 05:49 PM
Class A output stage for CD Player PTSOUNDLAB Digital Source 0 30th December 2001 12:04 PM
Class h or g output stage? Opie Solid State 1 24th October 2001 09:30 PM

New To Site? Need Help?

All times are GMT. The time now is 12:33 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