Need help understanding class B output stage capacitor variations - diyAudio
Go Back   Home > Forums > Amplifiers > Headphone Systems
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Headphone Systems Everything to do with Headphones

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 August 2010, 03:11 AM   #1
diyAudio Member
Join Date: Aug 2005
Blog Entries: 1
Default Need help understanding class B output stage capacitor variations

I'm working on designing a better than average op-amp + transistor class B output stage headphone amplifier. There really isn't that much that is special about it, but I want to the design and math to be solid before I order parts and start to build. My design requirements are: * easy to understand, build, and somewhat small in size, * relatively low power requirements to minimize heat, the electric bill, and to allow for possible battery operation (ruling out class A), * flexible enough to drive lower impedance headphones (not very often) but usually my 600ohm AKG's, and * some flexibility in the design for simple experimentation. My electronics experience level is "noob who knows too much", so please keep answers on that level. My health also sucks so I may not be coherent enough to respond everyday.

The final design will look very similar to this: (I wish I had found this starting out)

My question arises from the C3L and C4L capacitors in Figure 1. What value and what configuration leads to optimum performance?

From what I understand, capacitors across the transistor base pins are supposed to help with crossover distortion. But how?

The thing I find confusing is that other similar designs have used other configurations and values...

Headwize shows a single 1nF capacitor across the transistor bases (Figure 11c about half way down the page):
(as opposed to ESP-113's two 100uF's in stacked series paralleled with the diodes)

Like Headwize, this one has a single 22uF across the bases (C6 in the diagram):

The ESP-113 page mentioned the capacitors being paralleled with the diodes, but this explanation doesn't seem to fit a single capacator across both diode designs... so I'm confused a little more.

What is the math to calculate adequate capacitor size? I'm already familiar with "-3db_freq" = 1 / (2 * PI * R * C). Is this used? If so, does R come from the current mirror resistor?

Thanks for the help.
  Reply With Quote
Old 1st October 2010, 05:21 PM   #2
diyAudio Member
Join Date: Aug 2005
Blog Entries: 1
One thing I noticed the other day is that the paralleled capacitors with the diodes is very similar to the capacitors across each diode in a diode bridge to help with on/off noise. Is this similar?

Even though this is a headphone amp, should this be in another forum? Maybe discrete? I'm sure someone has a quick and easy answer for this... somewhere...
  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
Need help on understanding AudioResearch like output stage Cede Tubes / Valves 13 3rd January 2010 01:31 PM
Understanding output stage SOA?? Zero Cool Solid State 8 22nd November 2007 09:57 AM
Onkyo Power Output Stage, capacitor between bases of EF pair? capslock Solid State 5 13th April 2007 03:40 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 12:31 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