I'm currently working on a amplifier project and in the datasheets the IC i have choose it says "use with minimum 8 ohm speaker".
now modern amplifiers support both 8 and 4 ohm and all between, so my question is is there some circuit they use to adapt to the load applied or is it just as simple as "don't max the volume stupid". been looking all over but honestly i don't even know what i'm looking for or what it is called. can someone point me in the right direction?
/MrZ
now modern amplifiers support both 8 and 4 ohm and all between, so my question is is there some circuit they use to adapt to the load applied or is it just as simple as "don't max the volume stupid". been looking all over but honestly i don't even know what i'm looking for or what it is called. can someone point me in the right direction?
/MrZ
No load adaption is performed. An amplifier rated for 4 ohms is exactly that, it has the voltage and current ability to deliver its rated output into that impedance.
A chip specified for 8 ohm operation will probably be fine with a nominal 4 ohm loading but it will not be able to deliver its maximum voltage swing into that impedance. It would also be sensible to derate the supply voltage to suit.
What's the chip you are looking at ?
A chip specified for 8 ohm operation will probably be fine with a nominal 4 ohm loading but it will not be able to deliver its maximum voltage swing into that impedance. It would also be sensible to derate the supply voltage to suit.
What's the chip you are looking at ?
Currently looking at TDA7293 in Bridge configuration. and in the datasheet is mentions it is best to use 8+ ohm load.
I'm also have speakers in the works and the elements i choose isn't 8 ohm that is why i am looking for solutions.
kin of new to electronics but i'm the "learn by doing" kind of guy. though i also tend to overthink things.
been thinking about maybe build 2 outputs where the base is driven by a bridge of 200w and use just one chip for the mid+tweeter. but it's just an idea if i cant fully figure this out.
I'm also have speakers in the works and the elements i choose isn't 8 ohm that is why i am looking for solutions.
kin of new to electronics but i'm the "learn by doing" kind of guy. though i also tend to overthink things.
been thinking about maybe build 2 outputs where the base is driven by a bridge of 200w and use just one chip for the mid+tweeter. but it's just an idea if i cant fully figure this out.
The balanced outputs of a bridged amplifier each do "see" 4 ohms,
so that's why the total output-to-output load must be 8 ohms.
Think of it as two 4 ohm speakers in series, connected across the
balanced outputs (which you could also do). The center connection
of the series pair remains at AC ground, even though it's not
connected to anything else.
Last edited:
Yes, a bridged design changes everything although I never like the widely accepted terminology of each side of a bridged amp 'seeing half the impedance' of a non bridged design. So in your case this implies the amp 'sees' a 2 ohm load.
That is simply incorrect if you think about it. The impedance (in your case) is still 4 ohms, it is just that for a given output voltage per amplifier, the current is doubled. The load impedance remains the same. If the load were reactive (a cap) then a 0.1uF is still a 0.1uF no matter whether single ended, bridged or paralleled. The impedance remains the same.
Example, a single ended stage outputting 10 volts into 10 ohms sees 1 amp flow. A bridged output sees 10 volts from one amplifier and -10 from the other putting 20 volts across the load. The load is still 10 ohms, but now the current is 2 amps.
In practice and for a 4 ohm load you would be far better with a non bridged design, and perhaps even should look at a parallel circuit that would deliver twice the current over the single ended stage.
That is simply incorrect if you think about it. The impedance (in your case) is still 4 ohms, it is just that for a given output voltage per amplifier, the current is doubled. The load impedance remains the same. If the load were reactive (a cap) then a 0.1uF is still a 0.1uF no matter whether single ended, bridged or paralleled. The impedance remains the same.
Example, a single ended stage outputting 10 volts into 10 ohms sees 1 amp flow. A bridged output sees 10 volts from one amplifier and -10 from the other putting 20 volts across the load. The load is still 10 ohms, but now the current is 2 amps.
In practice and for a 4 ohm load you would be far better with a non bridged design, and perhaps even should look at a parallel circuit that would deliver twice the current over the single ended stage.
Figured I would contribute, so found this article from sengpielaudio dot com
Amplifier loudspeaker ohm impedance output input voltage bridging impedance no matching speakers no matching ohms speaker amp 4 - 8 - 16 resistance ohms connection of power amplifier to speakers There are no 4 ohm or 8 ohm amplifiers convert - sengpi
Amplifier loudspeaker ohm impedance output input voltage bridging impedance no matching speakers no matching ohms speaker amp 4 - 8 - 16 resistance ohms connection of power amplifier to speakers There are no 4 ohm or 8 ohm amplifiers convert - sengpi
Yes i just found the parallel design just before reading your comment. and i think i will follow that advice it looks like it will serve my goal much better. will read up on this and see what can build.
thank you for taking your time to help me. 🙂
- Status
- Not open for further replies.