Current Source <- how to optimize? - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

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 12th July 2004, 10:32 AM   #1
EE is offline EE  Germany
diyAudio Member
 
Join Date: Oct 2003
Default Current Source <- how to optimize?

To the audio gurus:

I'm just learning audio circuit design. For the input stage of a power amplifier, I need a constant current source. I know I can use a simple resistor, but this will not be optimal I guess.

The picture below shows the simplest possible approach. How can this be improved / optimized (only regarding sound)?
Attached Images
File Type: jpg temp.jpg (6.5 KB, 1930 views)
  Reply With Quote
Old 12th July 2004, 05:16 PM   #2
KlausB is offline KlausB  Germany
diyAudio Member
 
KlausB's Avatar
 
Join Date: Dec 2003
Location: Dresden
Hi EE,

the way you set up the CS looks OK. Adding a cap parallel to the zener diode might reduce noise. If you want the CS even more stable you can add a cascoding transistor. But I cannot tell you if this really would improve the sonic quality.


Regards
KlausB
  Reply With Quote
Old 12th July 2004, 05:51 PM   #3
jam is offline jam  United States
diyAudio Member
 
jam's Avatar
 
Join Date: May 2001
Location: Auburn, CA, USA
Replace R2 with a current source and the zener with a string of diodes.

Jam
  Reply With Quote
Old 12th July 2004, 06:46 PM   #4
OliverD is offline OliverD  Germany
diyAudio Member
 
OliverD's Avatar
 
Join Date: Nov 2002
Location: Germany
I prefer LEDs as voltage references in a CCS. Noise and temp. coeff. are better than a zener or string of "normal" diodes.

A simple current source for the reference element can be built using a FET and a resistor. If you need two current sources, one on each rail, you can of course use this for both sides.

Generally, a high hfe for T1 improves performance. A darlington might help. The 2SA1376 is a good choice, I think.

Here's the current source from my preamp which I like very much:
Attached Images
File Type: jpg ccs_pre.jpg (7.3 KB, 1877 views)
  Reply With Quote
Old 12th July 2004, 10:59 PM   #5
jaycee is offline jaycee  United Kingdom
diyAudio Member
 
Join Date: Apr 2004
Location: Norwich, UK
http://www.4qdtec.com/csm.html

I generally use figure 3 in my designs.
  Reply With Quote
Old 29th December 2004, 03:28 PM   #6
diyAudio Member
 
Join Date: Dec 2004
Location: gent
I'm doing some research on this topic to design my first amplifier. After reading a lot it I came to the conclusion that a two transistor constant current source is the best option, for an image I refer to my website http://users.pandora.be/jef_patat/au...t%20source.htm

kind regards, de jef
__________________
Visit Jef's Palace at http://www.jefspalace.be to comment my personal project
  Reply With Quote
Old 30th December 2004, 12:18 AM   #7
diyAudio Member
 
darkfenriz's Avatar
 
Join Date: Jun 2004
Location: Warsaw
OlivierD

for me it is hard to imagine more sophisticated current source than yours

but do them REALLY metter as far as sound quality is concerned?
  Reply With Quote
Old 30th December 2004, 03:32 AM   #8
diyAudio Member
 
LineSource's Avatar
 
Join Date: Sep 2003
Location: SiliconValley
For symmetrical dual differential front-end stages a minor DC offset can be nulled by tugging on the two current sources. This avoids summing the amplifier feedback with an opamp integrator as is often done.
Attached Images
File Type: jpg cs_offset.jpg (39.6 KB, 1932 views)
  Reply With Quote
Old 30th December 2004, 07:32 AM   #9
diyAudio Member
 
Join Date: Dec 2004
Location: gent
Default does it REALY matter?

I'm not for sure if it makes a lot of difference, I just started designing my first amp.
It only appears to me that the current source I will use gives best results so I think it's the best choice, and beside 4 resistors one cap and two transistors is not the end of the world.
It matters slightly in psrr and cmrr so I stick to my choice.

kind regards, jef
__________________
Visit Jef's Palace at http://www.jefspalace.be to comment my personal project
  Reply With Quote
Old 30th December 2004, 07:49 AM   #10
Electrons are yellow and more is better!
diyAudio Member
 
peranders's Avatar
 
Join Date: Apr 2002
Location: Göteborg, Sweden
Blog Entries: 4
Default Re: Current Source <- how to optimize?

Quote:
Originally posted by EE
To the audio gurus:

I'm just learning audio circuit design. For the input stage of a power amplifier, I need a constant current source. I know I can use a simple resistor, but this will not be optimal I guess.

The picture below shows the simplest possible approach. How can this be improved / optimized (only regarding sound)?
You can check some of my stuff but if you use these searchwords

current source

current source cascode

current source cascode wilson mirror

MAT02

Use these words in different combinations when you are using www.google.com you come up with tons of info. Sorry not to be at much help right now. It's a big topic.
__________________
/Per-Anders (my first name) or P-A as my friends call me
Tube Buffered Gainclone in work |Thread || Diamond buffer |Thread for the group buy | Wiki
  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
BOZ with current source? Decker Pass Labs 2 9th May 2007 03:06 PM
Low Current Source gingertube Tubes / Valves 5 15th November 2005 09:48 PM
Aleph-type current source, but source follower this time tschrama Pass Labs 4 29th July 2005 12:55 PM
Source follower electret mike -> use with current source? capslock Solid State 1 28th February 2003 12:54 PM
R21? and Current Source AC Current Gain macka Pass Labs 9 20th May 2002 08:58 PM


New To Site? Need Help?

All times are GMT. The time now is 03:08 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