Edit: this questions is for the LM3886
Do you really need a input cap with a resistor to ground? I guess it acts like a low-pass filter, right or wrong?
I didnt use it in my first, exprimental, gc but i have added it to the one i use now, and i think that my first one sounded way better. Specially in middle and high frequensys. And it isnt present in the National datasheet.
And i have also added a 220pF cap (Cc in Nationals datasheet) between leg 9 and 10, as suggested in the datasheet (did that on my first amp to) and it made the amp more friendly to my ears.
But, if i still need a input cap with a resistor to ground, how do i calculate the requierd values for it? And regarding the cap between leg 9 and 10, does a bigger cap (470pF for example) means that it let thrue higher freq. and a smaller cap (100pF maybe?) means that it cuts earlier?
Best regards, Carl-johan...
Do you really need a input cap with a resistor to ground? I guess it acts like a low-pass filter, right or wrong?
I didnt use it in my first, exprimental, gc but i have added it to the one i use now, and i think that my first one sounded way better. Specially in middle and high frequensys. And it isnt present in the National datasheet.
And i have also added a 220pF cap (Cc in Nationals datasheet) between leg 9 and 10, as suggested in the datasheet (did that on my first amp to) and it made the amp more friendly to my ears.
But, if i still need a input cap with a resistor to ground, how do i calculate the requierd values for it? And regarding the cap between leg 9 and 10, does a bigger cap (470pF for example) means that it let thrue higher freq. and a smaller cap (100pF maybe?) means that it cuts earlier?
Best regards, Carl-johan...
Actually that would be a high pass filter. You dont need it if your 100% confident your not going to be getting any DC on your input signal. The equation for the cut off frequency it 1/(2piRC)
So lets say you use a 10uF cap and 100kohm resistor you will have a cutoff frequency (or 3dB down point) of about 1.5Hz. This will block any DC and will not affect your passband range.
So lets say you use a 10uF cap and 100kohm resistor you will have a cutoff frequency (or 3dB down point) of about 1.5Hz. This will block any DC and will not affect your passband range.
Deltat said:
In fact it wasn't fine. The amp lost it's life with those values
But now whit the new values it's alive and kicking again
The hig's and middle is way more seperated and it's a clear sound. Just the way i like it. Before, all the middle, high and sometimes lower frequens allmost floated together.The only thing to adjust now is the bass, witch hopefully will be more sharp after some power-adjustements.
my target RC cutoff frequency is 2hz. this would be low enough that there will be effectively no phase or amplitude effects above 20hz. though really, a low cutoff of 10hz or more probably won't matter. In most of my designs i try to limit the largest resistor to 50kohm, and typically use 50kohm for my input so i can use a 1uF film cap on the input. it gives me 3.18hz for the cutoff, which is fine for my purposes. if it were a subwoofer amp, i'd concider using a larger cap or resistor, but probably would accept 3.18hz as a good cutoff.
It's a 10uF cap and a 100k resistor. But now im not shore if it was so good at all.. gha i need to test some more... maybe it was better with my former setup.jaudio said:
Yea i have thought about that. The brand of my elyt-cap's is all Jamicon, because that was the best we had at my work. The decopling-cap's is WIMA. The input-cap now is a bi-polar 10uF Jamicon, but before that it was a 1uF WIMA.Nordic said:
Any suggestion about brands for caps? Black Gate? Or other. Please post. Im thinking about doing some serious shopping before i continue testing
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