electronics, repairs, service manuals and datasheets discussion community for the repairs professionals and technicians
Audio amplifier limiting output power

Post new topic   Reply to topic    Electronic equipment repair and service manual search discussion Forum Index -> Electronics General
View previous topic :: View next topic  
Author Message

Joined: 21 Oct 2016
Posts: 1

PostPosted: Fri Oct 21, 2016 8:55 am    Post subject: Audio amplifier limiting output power Reply with quote

What I have:
• A transformer rated at 150VA / 30V (center tapped) / 5A
• Speaker rated at 30W / 8 ohms (measured 6.3 ohms with my multimeter)
Will use class AB amplifier:
• LM4780 http://www.kynix.com/Detail/1143170/LM4780TA%2FNOPB.html
• Question:
If I send +30V & -30V to this chip, I will get 45W at 1%THD+N:

Is it possible to keep +30V & -30V but limit the maximum power to 30W? Is it by playing with the gain (feedback resistor value)?
I read somewhere "...power amps at lower gains requires more input voltage to get the same power output, with the same speaker impedance".
How to adjust/calculate the gain so that I get a maximum of 30W output with +30V / -30V power supply? I own the transformer already so I plan to use it as the power supply (+30V / -30V). It is center tapped. It is 30V-0V-30V.

I know that sending +40V/-40V is almost at the maximum (recommended) value of 84V. Is it possible to use more diode to drop the voltage or any other method (I didn't found any regulator that fit my needs)? Maybe I can send 40-0-40 but then my output power will be around 82W and my speaker is rated 30W. In this case, I can lower the gain to 20db to help (minimum value) and add a resistor before the speaker (ie: 4 ohms, but very high watt)? I guess I could add a potentiometer at the input (A-B) to limit the power sent to my speaker right?

from the title of the chip, I think I cannot go higher than 60W in stereo: "Overture Audio Power Amplifier Series Stereo 60W". What will happen if sending 40-0-40?!
if sending 40-0-40 to the amp then the output power per channel will be around 82W. What will happen (an implosion or a black hole)?

I am connecting a line out having 16ohms impedance and 1V RMS signal level. What if I add a potentiometer / volume control at the input of the power amp, thus limiting the amount of signal level going in the amp. Would the power amp consume the 80V even if the signal level is only 500mV RMS (ie)?
Any advice would be much appreciated.
Back to top
View user's profile Send private message

Joined: 29 Nov 2020
Posts: 2

PostPosted: Sun Nov 29, 2020 1:45 pm    Post subject: Reply with quote

I am building 2x15W amplifier based on TA2024. I am also building small Munny speakers based on 1" full-range Tang Band drivers to go with the amp. The drivers are only 4W RMS and 8W max so the amp is way too powerful for them.

Is there an easy way to limit the output power of the amplifier so it does not exceed the speaker specs? This setup is going to my kids room so I am afraid that they may crank the volume all the way up destroying the speakers.

Here are our reviews of the best toys for 5 year old boys to get as a gift. Check them out. List of best toys and gift for five year boy.
Back to top
View user's profile Send private message Visit poster's website
Display posts from previous:   
Post new topic   Reply to topic    Electronic equipment repair and service manual search discussion Forum Index -> Electronics General All times are GMT
Page 1 of 1

Jump to:  
You can post new topics in this forum
You can reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum

eServiceInfo on FB - Service Manuals Free Download - Service Diagrams

Free TV Schematics Download - HARDW.net - Pinout Master - Jabse Search - Jabse.InK  - Pulsator

SnimkiOt.com - Poblizo.com : пътешествия