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 15th September 2006, 03:58 PM   #1
matic is offline matic  Yugoslavia
diyAudio Member
 
Join Date: Apr 2005
Location: Subotica
Default Bridge amplifier on 8 om

I have stereo amplifier 2x100w rated 8 oms. Transformer is 300VA. Can i brigde this amplifier so i can have 200 w on 8 om?
I know for rule that if amplifier rated for 4 oms in bride must have 8 om speaker.
  Reply With Quote
Old 15th September 2006, 05:50 PM   #2
anatech is offline anatech  Canada
diyAudio Moderator
 
anatech's Avatar
 
Join Date: Jun 2004
Location: Georgetown, On
Hi matic,
It depends on the amplifer as to how it will react to this. If the amplifer is not designed to be bridgeable, assume that you may cause it to fail.

Question for you. Why do you want to bridge this amp?

-Chris
  Reply With Quote
Old 15th September 2006, 05:53 PM   #3
MikeB is offline MikeB  Germany
diyAudio Member
 
MikeB's Avatar
 
Join Date: Apr 2004
Location: GŁtersloh
Matic, i think you gave yourself already the correct answer...
For bridging into 8ohm the amp must be capable of handling 4ohm.

So the answer is: NO

(btw, an amplifier rated 8ohms only is always suspect to me)

Mike
  Reply With Quote
Old 15th September 2006, 06:01 PM   #4
anatech is offline anatech  Canada
diyAudio Moderator
 
anatech's Avatar
 
Join Date: Jun 2004
Location: Georgetown, On
Hi Mike,
Quote:
(btw, an amplifier rated 8ohms only is always suspect to me)
Well, yeah. I didn't want to depress the guy though!

-Chris
  Reply With Quote
Old 15th September 2006, 06:05 PM   #5
MikeB is offline MikeB  Germany
diyAudio Member
 
MikeB's Avatar
 
Join Date: Apr 2004
Location: GŁtersloh
Ooops,

Mike
  Reply With Quote
Old 16th September 2006, 08:49 AM   #6
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Hi,
an amp rated for 8ohm duty is no stigma.

Depends on the criteria adopted by the designer.

If I were rating an amp for 8ohm duty, my criteria would be.

Stable into 4r
Stable into 8r//test caps
Heatsink sufficient for continuous power at -10db for domestic and -3db for PA.
4r power rating >= 3 * 16r power rating. i.e. <=-1.2db on Load Voltage
Output stage rated to 8ohm and 60degree phase angle at typical maximum operating temperature on one second or longer SOAR.
Protection system to allow transient and long term overloads to be survived.

I suspect an 8ohm amp built that way may be more able than many 4ohm amplifiers out there in the market place.
__________________
regards Andrew T.
  Reply With Quote
Old 16th September 2006, 04:45 PM   #7
matic is offline matic  Yugoslavia
diyAudio Member
 
Join Date: Apr 2005
Location: Subotica
This is what i have:1 toroidal transformer 400VA, 2x39Volt which is, by some formula, enough for 2x120W at 8 oms. If i wanted to drive this amp at 4 oms (2x240W) then transformer would have to be at least double, 800VA.
Output for 120w at 8 om is 31volt which gives I=3,875. Because "I" is limited by transformer then, i think that teoretical, this amp can drive 4om only by 1/2 watt then for 8om? P=R*I2=4*(3,875*3,875)=60W. Based on this i think that in bridge this amp can drive 8 om. If not, please don't throw wegetables at me
  Reply With Quote
Old 16th September 2006, 05:02 PM   #8
MikeB is offline MikeB  Germany
diyAudio Member
 
MikeB's Avatar
 
Join Date: Apr 2004
Location: GŁtersloh
It's so much fun to throw vegetables after someone...

You're right, if the power is limited by the power supplys ability to deliver current, the poweroutput would half for 4 ohms compared to 8ohms.
This means, if the current ability is limiting, you will not get any more amperes through your speakers resulting in having the same outputpower again when bridging.

BTW, doubling the outputpower increases the volume by 3db, barely noticable. It's more interesting how effortless an amp can deliver the rated power without compressing and maintaining dampingfactor.

Mike
  Reply With Quote
Old 16th September 2006, 09:44 PM   #9
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Hi,
If I were designing an amp back to front and starting with the available transformer, then your 400VA can support about 260W of output.
130W+130W into 8r is about the maximum you can get from this transformer. The 39Vac just about matches the DC voltage (about 56Vdc to 57Vdc) requirement for 130W
Alternatively, you could do a 250W into 4r monoblock, but all parameters would need to be optimised to achieve this from 39Vac.
As I said back to front.
__________________
regards Andrew T.
  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
How I Can Bridge This Power Amplifier??? broka Solid State 2 10th December 2006 10:43 PM
Bridge SE amplifier croccodillo Tubes / Valves 3 17th February 2006 01:58 AM
TDA amplifier , Bridge , 600 W . darkm4n Chip Amps 0 29th March 2004 12:48 PM
how to bridge an amplifier MV Car Audio 1 25th March 2004 05:11 PM
How do you bridge two bridged amplifier? thylantyr Solid State 41 15th October 2003 10:30 PM


New To Site? Need Help?

All times are GMT. The time now is 12:05 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