Portable GC/? - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Chip Amps Amplifiers based on integrated circuits

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 1st August 2005, 08:36 PM   #1
diyAudio Member
Join Date: Dec 2004
Location: Illinois
Default Portable GC/?

I need to make an amplifier that can supply 2 x 20w @ 6 ohms, and a seperate amplifier that can supply 1 x 30w @ 4 ohms, that can run off the same power supply.

I need this to be as cheap as possible, and quality is a secondary concern (it's for a gift, and I am broke ).

If possible can I run this off a wallwart?
  Reply With Quote
Old 2nd August 2005, 01:57 AM   #2
Stocker is offline Stocker  United States
diyAudio Member
Join Date: Dec 2003
Location: Austin
That would be one hefty wallwart! Think about 2" x 2" for the transformer alone.

If by portable you mean, plays unplugged from the wall, then it gets a little complicated. If you mean, not stuck permanently on a shelf, your task is to follow the well-worn path of Gainclone builders before you.
Jesus loves you.
  Reply With Quote
Old 2nd August 2005, 02:38 AM   #3
diyAudio Member
Join Date: Mar 2007
u can try locating ST micro chips they do have three channel chips may be working on 12V batteries like TDA7386 which is a 4 channel poweramp.
  Reply With Quote
Old 2nd August 2005, 03:04 AM   #4
diyAudio Member
Join Date: Dec 2004
Location: Illinois
I originally wanted it to be portabile, i.e. be able to be powered outside the wall, but I am starting to think that is improbable.

I want it to be inside of this:

My girlfriend wanted a small "cute" system that could play her music, and I didn't want her to get a bose sounddock, so I came up with this, and there is a 4ohm woofer in the base of it, and (not shown) a heat sink on the rear.
  Reply With Quote
Old 2nd August 2005, 03:31 AM   #5
diyAudio Member
Join Date: Jun 2005
Location: Seal Beach, CA
If you want to do this, a standard wall wart will almost certainly not do the job.

My idea is to make a DIY power brick that would feed the power into the amp. Put it inside one of the many available plastic enclosures and make sure to mount everything very securly inside it as it most certainly will get jostled around.
  Reply With Quote
Old 2nd August 2005, 09:03 AM   #6
evo is offline evo  England
diyAudio Member
evo's Avatar
Join Date: May 2004
Location: England
Something like this?

  Reply With Quote
Old 2nd August 2005, 06:39 PM   #7
Join Date: Mar 2003
Location: Lisbon, Portugal
Originally posted by bjackson
I need to make an amplifier that can supply 2 x 20w @ 6 ohms, and a seperate amplifier that can supply 1 x 30w @ 4 ohms, that can run off the same power supply.
  Reply With Quote
Old 3rd August 2005, 05:29 PM   #8
diyAudio Member
Join Date: Jun 2005
Location: USA
Send a message via AIM to ThSpeakerDude88
I have experience with the TDA7264. 2x25 watts RMS @ 4 ohms with +/- 16 volt power supply. Im useing a printer power supply.

You can try the TDA7265, same chip basically accept it has externally adjusted gain and can be bridged. 2 of these chips would give you 2x25 watts + 1x50 watt BTL. Both configurations will run off of +/-16 volts.

Also you might want to look into STA543SA. it's 7wattsx2 + 1x26watt BTL in one chip, runs off of 6.5-18 volts, nominal voltage is 12-14 volts ( single supply)

I agree about not overpaying for a sounddock. My entire 4-H electronics project display was about that, the audio indusrty preying on people that want small and portable. They usually are a cheap design with very low power.Mind you, most sound very good, lacking a lot of bass but still sound very good. The thing is because its "new" and "portable" and "compatable with an iPod" they mark them up to reddiculous prices- ie bose sound dock ( which does sound wonderful for its size) Sorry though, I'm not going to pay 80 dollars for a JBL sound stage that has a total output power of 4 watts @ 10% THD or 140 dollars for an altec lancing that has a total output of 2 watts. Its insane. You can hook your iPod up to headphones right? then why can't you hook it up to a sound system like you would your cd player?

sorry, had to put in my 10 cents :-P

hope I was able to be of help!

  Reply With Quote
Old 4th August 2005, 05:25 AM   #9
PRR is offline PRR  United States
diyAudio Member
PRR's Avatar
Join Date: Jun 2003
Location: Maine USA
> 2 x 20w @ 6 ohms, and a seperate amplifier that can supply 1 x 30w @ 4 ohms, that can run off the same power supply.

Assuming "perfect" amplifier, each output is 10.95V RMS, 31V peak-peak, so you need a 31 volt (or +/-16V) power supply. Given losses, I would think at least 24VAC CT for +/-18V power.

Using a rule of thumb for DC current, I get total 3.5 Amps DC. The transformer's AC current rating must be 1.6 to 1.8 times higher, say 6 Amps AC. This is 150 VA.

There are nearly no 150VA wall-warts. I have seen some in the 100Watt range but they were switchers, output odd voltages, and very expensive.

Remember that 10 times the audio wattage is barely twice as loud. It works the other way: 20W+20W+30W might be nice, but 5W+5W+7W will be almost as "loud" and a lot less expensive. It still comes to about 40VA, a very large wart. Ignoring the wart: start with a 12VAC 3A CT transformer. Or if you don't mind capacitor-coupling all three speakers (probably a bad idea for a 4 ohm woofer), you don't need the center-tap. You may be able to find a 12VAC 2A wall-wart and just accept that the supply rail will sag in clipping. As a "portable" or dorm-room system, I think a wart is an utter nuisance and the power should be in the box. But this means you need to be VERY careful with your line-wiring: burning down your girlfriend's room would be bad for the relationship.

BTW: after decades of DIY, I do not think DIY makes a good gift. Most folks don't get it.
  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
Wanted: External, portable CD-ROM or DVD drive; decent USB DAC, portable speakers. Spasticteapot Swap Meet 0 31st May 2006 02:13 AM
Portable DAC Prune Digital Source 1 5th December 2003 06:22 PM
Portable CD/MP3 Prune Digital Source 1 3rd December 2003 02:49 AM
Portable LPS Prune Everything Else 2 4th October 2003 04:17 AM

New To Site? Need Help?

All times are GMT. The time now is 09:48 AM.

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