Smaller transformer for lm3886 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 5th April 2003, 04:30 PM   #1
ted is offline ted
diyAudio Member
 
Join Date: Dec 2002
Location: Chicago, Il
Default Smaller transformer for lm3886 amp?

OK, I made an LM3886 amplifier and worked out the bugs, and is powered by a large transformer, 400watts, making the whole thing big and heavy. So I was thinking it may be interesting to reduce the size/weight by doing something like what Carver did since for a lot of power, the transformer sure seems small when I compare a Carver 1.5 with something like a Phase Linear 400 transformer.

So the question is. Is there something special about a Carver type transformer? Since a triac is used before the transformer, to switch power on/off, can the transformer be connected directly to the mains? Additionally, and most important, can an off the shelf transformer be tricked to have similar properties, if there are any special properties?

Just an idea....
Thanks.
  Reply With Quote
Old 5th April 2003, 08:09 PM   #2
Account Disabled
 
Join Date: Jul 2002
u can us in a switched transformer....

very small
  Reply With Quote
Old 13th April 2003, 12:00 AM   #3
ted is offline ted
diyAudio Member
 
Join Date: Dec 2002
Location: Chicago, Il
I assume that when you say "switched transformer", that it's a "flyback" or buck-boost derived switchmode converter technique?

The thing that sent me down the trail was that most switchmode converters run from a ~20Khz->50Khz oscillator, and not 60Hz as I assume that a Carver does since I do not find the typical forementioned switching frequency? But obviously Carver got it to work.

Since I have little desire to design a switchmode supply running at 60Hz, Iíll just have to find a better way to optimize the power supply requirements of my lm3886 amplifier.

Thanks for the information.
  Reply With Quote
Old 13th April 2003, 09:46 AM   #4
trwh is offline trwh  United Kingdom
diyAudio Member
 
trwh's Avatar
 
Join Date: Apr 2002
Location: UK
Ted, have a read through of this thread:

http://www.diyvideo.com/forums/showt...5&pagenumber=1

I think 400W is overkill for a 2xLM3886 amp.
  Reply With Quote
Old 13th April 2003, 05:20 PM   #5
Nisbeth is offline Nisbeth  Denmark
diyAudio Member
 
Nisbeth's Avatar
 
Join Date: Jan 2001
Location: Denmark
If you look at the datasheet for the 3886, i think you'll find that the max. consumption is ~150-160W (per chip), so a 300VA should be acceptable for all practical purposes. Since you're (presumably, hehe) only playing music and not test tones at full amplitude, I think you can get away with a bit less than that, say 220-250 VA. You might run out of power a bit earlier, but for normal listening levels it should be OK.

/U.
  Reply With Quote
Old 13th April 2003, 10:58 PM   #6
ted is offline ted
diyAudio Member
 
Join Date: Dec 2002
Location: Chicago, Il
I use a 400 watt transformer since it's powering 5 X lm3886 where the rail voltage is ~38+/- volts. I get about 50watts/ch into 8 ohms with all 5 channels running. I know the transformer is to small if I were to use 4-ohm speakers, a.k.a. why I was thinking of a smarter power tub.

I have been sufficiently discouraged in constructing a 60hz switchmode supply, so I am now thinking of attacking the weigh / size by reducing heat sinking. The reduced heat sinking would be theoretically possible if I use an unused tap on the transformer (30vac / ct [20vdc +/-]]). Then feed the ln3886's with the lower supply, then if let's say there is 5v on the output, kick in the presently used 38+- volt rails. To keep things really simple, any one of the lm3886's, that exceed 5v's, would cause all the others to see the larger supply voltage also.

I know lots of amplifiers that use this trick, but I am not sure how much a lm3886 would like the dynamic voltage switch.

Thanks for all the advice.
  Reply With Quote
Old 14th April 2003, 02:41 PM   #7
diyAudio Member
 
Join Date: Jan 2002
Location: Sweden
Send a message via ICQ to Christian
Quote:
Originally posted by ted
I use a 400 watt transformer since it's powering 5 X lm3886 where the rail voltage is ~38+/- volts. I get about 50watts/ch into 8 ohms with all 5 channels running. I know the transformer is to small if I were to use 4-ohm speakers, a.k.a. why I was thinking of a smarter power tub.

I have been sufficiently discouraged in constructing a 60hz switchmode supply, so I am now thinking of attacking the weigh / size by reducing heat sinking. The reduced heat sinking would be theoretically possible if I use an unused tap on the transformer (30vac / ct [20vdc +/-]]). Then feed the ln3886's with the lower supply, then if let's say there is 5v on the output, kick in the presently used 38+- volt rails. To keep things really simple, any one of the lm3886's, that exceed 5v's, would cause all the others to see the larger supply voltage also.

I know lots of amplifiers that use this trick, but I am not sure how much a lm3886 would like the dynamic voltage switch.

Thanks for all the advice.

Hi Ted!
I'm building a 5 channel power amp using the LM3886 chips to! Do you have any pics or more info on your'e amp?
Are you using it in a surround system?

/Chris
  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 LM3886 Stereo Amp. w 12-0-12VAC Transformer Andreq Chip Amps 27 1st May 2011 05:32 PM
transformer for LM3886 dual mono kit gonzalez Chip Amps 16 11th October 2008 09:55 AM
Transformer for LM3886 marcusdeming Chip Amps 25 10th January 2008 01:44 PM
LM3886 w/transformer $100 plus shipping nodiak Swap Meet 0 22nd July 2006 11:53 PM
LM3886 - What Transformer ? HarryK Chip Amps 19 12th March 2005 07:51 AM


New To Site? Need Help?

All times are GMT. The time now is 01:33 PM.


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