Little mini amp - 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 4th January 2011, 05:57 PM   #1
Banned
 
Join Date: Jan 2005
Default Little mini amp

After the failed mosfet amp i startedf wondering if the board was even working so i replaced some komponents and reconfigured the drivers to become outpur devices and hooked up a small low voltage psu and after fixing a broken trace i found around one of the drivers, the thing jumped to life.

Pics:
http://i.imgur.com/OZXvd.jpg
http://i.imgur.com/Viop7.jpg

Driven by this:
http://i.imgur.com/ueCSl.jpg

Schematic:
http://i.imgur.com/tOfkk.jpg

The drivers are BD139 and BD140 and the rails are about 15VDC unloaded.

It gives a few watts in 4 ohms and sounds pretty good for beeing biased into class B.

I was suprised the circuit works at all below 35V rails since this was designed for minimum 30V rails.
  Reply With Quote
Old 4th January 2011, 07:06 PM   #2
jaycee is offline jaycee  United Kingdom
diyAudio Member
 
Join Date: Apr 2004
Location: Norwich, UK
Use it for headphones
  Reply With Quote
Old 4th January 2011, 07:56 PM   #3
Banned
 
Join Date: Jan 2005
Im wondering if that broken trace on the base of the low side driver could have caused the 0-5V oscillation and lack of response on the input.

I remember that on the first powerup when i had miswired the vbe multiplier it did something before my current shunt died from the 10+ A that was flowing, afterwards it did the oscillation and nothing else.

I tried replicating this scenario in simulation but it just removes the negative half of the sine and adds some ringing, though simulation doesent include the stray inductance and stray capacitance of a typical board, wires and components needed to make an amp oscillate if something is wrong.
  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
My new mini Class A amp. GK Solid State 58 18th January 2009 04:04 PM
Mini pre amp uhcmos Vendor's Bazaar 1 27th October 2008 04:08 AM
Mini EL84 Amp Done sorenj07 Tubes / Valves 21 25th June 2007 03:26 PM
Mini guitar amp from a Webcor tape amp, is it possible? StiffHand Tubes / Valves 9 28th July 2006 01:31 PM


New To Site? Need Help?

All times are GMT. The time now is 04:52 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