Hello,
I've searched and read everything I can find on transformers but could still use some help understanding the relationship between primary and secondary voltages.
For example I selected a 300va 25-0-25 trafo for my Lm3886 project knowing the max supply voltages from the data sheets and because of unusually high line (127 volts at times) in my area I'm closer to the max(after rectfication) than I want to be,39vdc +/- more or less.
I know that simply choosing a 300va trafo with lower secondary voltage say 20-0-20 will do the job but how do the different secondary voltages available for the same 300va trafo affect the power output?
Also I'm driving relatively friendly 4 ohm speakers which is why I chose the LM3886 for it's better perfomance into 4 ohm loads.
I've read here that you don't want to push to much current at a 4 ohm load or that lower voltage is better for 4 ohms.At any rate this is the other area of the equation I could use some help understanding.
Thanks in advance!
I've searched and read everything I can find on transformers but could still use some help understanding the relationship between primary and secondary voltages.
For example I selected a 300va 25-0-25 trafo for my Lm3886 project knowing the max supply voltages from the data sheets and because of unusually high line (127 volts at times) in my area I'm closer to the max(after rectfication) than I want to be,39vdc +/- more or less.
I know that simply choosing a 300va trafo with lower secondary voltage say 20-0-20 will do the job but how do the different secondary voltages available for the same 300va trafo affect the power output?
Also I'm driving relatively friendly 4 ohm speakers which is why I chose the LM3886 for it's better perfomance into 4 ohm loads.
I've read here that you don't want to push to much current at a 4 ohm load or that lower voltage is better for 4 ohms.At any rate this is the other area of the equation I could use some help understanding.
Thanks in advance!
Mothman just concentrate on the secondary voltage of the transformer you purchase.....the voltage in your house fluctuates depending on the time of day....what you read is the average voltage...there are peaks of 200vac that your meter cant read...because we all know they average out...even a true RMS(root mean square) meter will give you a better idea...my beliefs are when building such a chip amplifier stay closer to the SOA of the chip (less heat disapation) and longer life...these little buggers can stand so much...if you drive the rails up to the max you will enjoy sweet success for a short time LOL
Cheers!!The DIRT®
Cheers!!The DIRT®
Thanks Dirtman,
I'm just trying to make some better informed choices and build my knowledge base along the way.
I'm just trying to make some better informed choices and build my knowledge base along the way.
O.K let me try again.Take a 300va trafo at 18-0-18 it puts out 8.2 amps,at 25-0-25 it's 6.0 amps,30-0-30 5.0 amps and so on.
Higher voltage,less amps.I understand that they all equal the same 300va rating but other than the chips supply requirements what determines the best volt/amp combination.
Higher voltage,less amps.I understand that they all equal the same 300va rating but other than the chips supply requirements what determines the best volt/amp combination.
now your on the right track...calculate the maximum dissaption of the chip VxA and you will derive at the best secondary voltage to use....most data sheets have a graph to show you a derative curve of output/distortion levels and temperature conditions the key thing to look at is in the design criteria is where your going to get maximum performance within the boundaries of the device...thats why I mentioned SOA in my last post if that makes any sense to you
Cheers!!The DIRT®
Cheers!!The DIRT®
Hey Joe,
I understand the concept but the application of the data on the graphs and such is over my head.
What's SOA?
I understand the concept but the application of the data on the graphs and such is over my head.
What's SOA?
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