Simple Amp for active subwoofer - 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 13th October 2004, 02:41 PM   #1
diyAudio Member
 
Join Date: Aug 2004
Location: perth
Default Simple Amp for active subwoofer

I am looking for a simple cheep amp to make my subwoofer active.


I have designed this very simple amp using darlington transistors such as BDV64 bdv65. but would like to use mosfets instead for a more rugged design.
can any one help?

maybe modify the design to use mosfets instead of bipolar.
Attached Images
File Type: jpg simple_amp.jpg (28.7 KB, 974 views)
  Reply With Quote
Old 13th October 2004, 06:27 PM   #2
MikeB is offline MikeB  Germany
diyAudio Member
 
MikeB's Avatar
 
Join Date: Apr 2004
Location: Gütersloh
Hi !

Your circuit is a bit too simple, you have no biasing for outputstage
at all. Even if it's "only" for a subwoofer, you can't work without it.
You could try at least 3 diodes between the bases of the bjts.
For mosfets this issue is even bigger, they have a much bigger
threshold for biasing.

Mike
  Reply With Quote
Old 13th October 2004, 08:12 PM   #3
ingrast is offline ingrast  Uruguay
diyAudio Member
 
Join Date: Sep 2004
Location: Montevideo
Default Simple SW amplifier

How much power are you planning to handle?

What impedance driver do you have in mind (4 - 8 ohms)?

Do you have an actual Subwoofer output available (e.g. DVD player) with channels mixed and filtered down?

As a matter of fact a chip amplifier will probably be actually simpler to build and cheaper to boot!!

Rodolfo
  Reply With Quote
Old 13th October 2004, 08:34 PM   #4
diyAudio Member
 
acenovelty's Avatar
 
Join Date: Aug 2004
Location: SF Bay Area
http://www.partsexpress.com/pe/showd...number=300-792

$89.95 US

ready to go.

Prosit
  Reply With Quote
Old 14th October 2004, 07:57 AM   #5
diyAudio Member
 
Join Date: Aug 2004
Location: perth
Default the new schematic

Ok i have corrected the schematic. it works fine in the simulation. the output transistors are actually going to be BDV64 BDV65
but the problem is that i really want to use flat pack transistor and also keep the cost down. so the BDV64/65 are onyl about $4 australian each the whole PCB and components will only cost about $15 austalian thats about $11US.
I am going to biulding this amp this wekend just for fun but if anyone can help with a similar design using mosfet , i will go for that design. because the BDV64/65 do not have a good Safe operating area compared to similar priced mosfets.
Any help would be apreciated as I have never designed or biult a mosfet AMP.
Attached Images
File Type: jpg activesub.jpg (51.4 KB, 673 views)
  Reply With Quote
Old 14th October 2004, 10:15 AM   #6
MikeB is offline MikeB  Germany
diyAudio Member
 
MikeB's Avatar
 
Join Date: Apr 2004
Location: Gütersloh
Hi !
One more thing: You also should place a 100kohm resistor from
base of input-bjt to ground, and add a inputcapacitor (~4.7uF mks
or 10-22uf electrolytic). Or you might get some strange inputoffset,
depending on the subwoofer-out from preamp.

Did you zoom into crossoverregion ? (In oscilloscope)

Mike
  Reply With Quote
Old 15th October 2004, 05:07 PM   #7
diyAudio Member
 
Join Date: Aug 2004
Location: perth
Thanks Mike
I have added the input resistor and capacitor as you mentioned.
Actually i have just made the PCB, it is ready for drilling I will know how it sounds over the weekend I hope.
here is a picture of the PCB. the transistors mount flat on the bottom of the board so that the board and the transistors mount onto the heatsink easily.
board is very small only about 9cm x 4 cm or less than 4 inch x 2 inch.
if any one is interested i will post more info after a tial run.
I was hoping to get close to 100 w RMS into 8 ohms with mosfets but I will probably only get about 70 w RMS with the darlingtons.
Attached Files
File Type: pdf amppcb.pdf (20.8 KB, 146 views)
  Reply With Quote
Old 15th October 2004, 05:23 PM   #8
diyAudio Member
 
Join Date: Aug 2004
Location: perth
Also the new schematic
Attached Files
File Type: pdf schematic.pdf (10.2 KB, 212 views)
  Reply With Quote
Old 15th October 2004, 05:29 PM   #9
kinser is offline kinser  Israel
diyAudio Member
 
kinser's Avatar
 
Join Date: Jan 2004
Location: R'aanana
Send a message via ICQ to kinser Send a message via MSN to kinser
Spiro007,
My name is David and im 14 years old,
I like your amp design, its seems pretty simple
I have some questions:
1.Can I use mjw21195/6 on the output?
2.Can the amp handel 4 ohm load? If it can then how much power will it deliver?

Thanks,
Kinser (David)
  Reply With Quote
Old 15th October 2004, 06:04 PM   #10
diyAudio Member
 
Join Date: Aug 2004
Location: perth
Hi david.
Thats some nice transistors you have there. I bought a kit amp using those devices and it sound very good.
The amp i designed doesnt have enough current to drive the mjw21195 devices , but if you added an extra transistor to each of the mjw21194/5 's it would probably work.
i have attached a pdf to explain. but since the mjw21194/5 are quite expensive i would experiment with some cheeper devices, also the sound quality of my amp is only good upto about 1khz.
Attached Files
File Type: pdf david.pdf (10.3 KB, 148 views)
  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
Need help with simple Active preamp. zhopudey Solid State 2 12th September 2007 06:03 AM
Simple ACTIVE I/V for TDA1543 rbroer Digital Source 62 2nd September 2003 06:14 PM
Active crossovers - is it this simple? annex666 Multi-Way 6 24th September 2002 08:43 PM


New To Site? Need Help?

All times are GMT. The time now is 11:23 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright İ1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2