High Power - Output transformer - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps

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
Reply
 
Thread Tools Search this Thread
Old 26th February 2004, 08:18 PM   #1
diyAudio Member
 
Join Date: Apr 2003
Location: New York
Default High Power - Output transformer

Purely theoretical at this point.

I'm wondering about the following method of
obtaining a higher output. The output of most chips is
limited by the rail voltage. In case of a lm3886 with e.g.
+/- 30V supply you could get 30-40 watts into 8 ohms.

What if you would use a tranformer after the output
and double the output voltage. This means of course
that in order to supply the current, the impedance the
chip sees drops. This could be solved by
putting multiple of these transformers in series.
The advantage could be that small DC offsets would not
matter. In addition maybe matching of components
would not be as critical.

With a bridged design you may quadruppel the power
again and get up to 500W into an 8 ohm speaker.
(Although at the cost of 8 chips).

Has anybody done something similar considered this?
Or is my idea flawed?

Harry Andree
  Reply With Quote
Old 26th February 2004, 08:35 PM   #2
AGGEMAM is offline AGGEMAM  Denmark
diyAudio Member
 
AGGEMAM's Avatar
 
Join Date: Jul 2002
Location: Copenhagen
Default Re: High Power - Output transformer

Quote:
Originally posted by h_andree
Or is my idea flawed?

Flawed? Nah! You have just invented the perpetual motion machine! Again!

You can't get higher power out by using transformers (or other witchcraft). The end.
__________________
Hmm .. no .. I really haven't got anythig cool to say ..
  Reply With Quote
Old 26th February 2004, 10:11 PM   #3
diyAudio Member
 
Join Date: Apr 2003
Location: New York
Default Missed the point?

I'm not trying to create power here.

If 2 chips bridged cap put out 100 W bridged at 8 ohms
then 8 chips bridged parallel can put out 400 W at
2 ohms.

You should be able to use a transformer to get the
output to be 400 at 8 ohms.

Now by putting many chips in parallel I
should be able to sustain the higher current that
is required for the higher voltage.

Harry
  Reply With Quote
Old 26th February 2004, 10:14 PM   #4
diyAudio Member
 
bigparsnip's Avatar
 
Join Date: Apr 2003
Location: Cambridge
Why not build an amplfier that is designed for these sorts of output powers, there are plenty out there, and they will be a lot cheeper than trying to find a suitable transformer (in terms of frequency response as well as power ratings), and will give a far better frequency response overall.

It just seams like trying to make a chocolate teapot when you would be far better off going for something a little better suited to the task at hand.
  Reply With Quote
Old 27th February 2004, 10:00 PM   #5
maylar is offline maylar  United States
diyAudio Member
 
Join Date: Jun 2003
Location: Connecticut
What you're asking for can be done, theoretically. But transformers are big, expensive, and have losses. Finding a 400 watt transformer to go from 2 ohms to 8 will cost you more than a 400 watt amplifier.
__________________
dave
  Reply With Quote
Old 28th February 2004, 07:42 AM   #6
AGGEMAM is offline AGGEMAM  Denmark
diyAudio Member
 
AGGEMAM's Avatar
 
Join Date: Jul 2002
Location: Copenhagen
Default Re: Missed the point?

Quote:
Originally posted by h_andree
If 2 chips bridged cap put out 100 W bridged at 8 ohms
then 8 chips bridged parallel can put out 400 W at
2 ohms.
No, actually if one chip can output 50 watts in 8 ohms, then 8 chips in parallel can output 400 watts in 8 ohms.

You don't need the output transformer if you parallel the chips! Just feed them all with the same input (possibly needing a buffer) and the same supply voltage, and add the outputs together. Voila, done.
__________________
Hmm .. no .. I really haven't got anythig cool to say ..
  Reply With Quote
Old 28th February 2004, 08:11 AM   #7
diyAudio Member
 
analog_sa's Avatar
 
Join Date: Aug 2002
Location: Sofia
Quote:
No, actually if one chip can output 50 watts in 8 ohms, then 8 chips in parallel can output 400 watts in 8 ohms.
The above is correct only as far as the multiplication result goes. Or was it a joke?

The idea of the transformer is not so wild but difficult to implement and expensive. Some of the difficulty comes from the requirement the transformer to have a step-up ratio. Otoh you don't need a lot of primary inductance.

It may be interesting to test this with a mains rated transformer with 1:2 step-up. I seem to recall someone manufacturing similarly speced step-down transformers for OTL tube amps. The response to those was mixed.
  Reply With Quote
Old 28th February 2004, 06:34 PM   #8
Steven is offline Steven  Netherlands
diyAudio Member
 
Steven's Avatar
 
Join Date: Oct 2003
Location: The Netherlands
In most Public Address amplifiers this is just routine. In Europe PA amplifiers have a standardized voltage output of 100Vrms at full output, in the USA this is 70V. PA loudspeakers are also standardized to these voltages, so you just connect many of these speakers in parallel up to the specified max output power.
The amplifier uses an output transformer to get an isolated 100V output and the loudspeakers use an input transformer to step down to the voltage that matches the actual speaker.
Because most PA amplifiers should also be able to deliver their output when running from a battery (often 24V) instead of mains, the actual supply voltage in the amplifier is very low. While running from mains the supply voltage is often around 28V and the 24V battery is connected to the supply voltage via a diode. If the mains fails, the battery acts as a secondary power supply and takes over automatically. The diode protects the battery from being (over)charged from the mains and avoids that the battery is loaded while the mains is still present.
You can buy 480W amplifiers that run from 24V (supply current 30A). http://www.pacat.co.uk/PDFs/Plena/Bo..._32412.pdf.pdf

Steven
__________________
The Analog Art shows no sign of yielding to the Dodo's fate. The emergence and maturation of monolithic processing finesse has perhaps lagged a bit behind the growth of the Binary Business. But whereas digital precision is forever bounded by bits, there is no limit excepting Universal Hiss to the ultimate accuracy and functional variety of simple analog circuits. - Barry Gilbert, 1973
  Reply With Quote
Old 2nd March 2004, 05:45 PM   #9
diyAudio Member
 
Join Date: Apr 2003
Location: New York
Default Source for these transformers

Does anybody know a source of
high-end transformers for this purpose?

Harry Andree
  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
Wanted - High Power, High Voltage, Audio Frequency Transformer Manual. kimbal Tubes / Valves 4 11th May 2009 08:05 PM
high DCR secondary (power transformer) jarthel Tubes / Valves 2 16th June 2007 09:44 AM
Class D high frequency output transformer Bazukaz Class D 1 21st January 2006 03:24 AM
Transformer for high power amp kon_udorn Solid State 4 8th April 2004 05:07 AM
high power output instrument amp fezz Instruments and Amps 3 14th September 2003 09:56 AM


New To Site? Need Help?

All times are GMT. The time now is 08:58 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