Hello,
I'm using an active high pass filter before the amps driving my BLHs to keep out the low lows. In looking at the circuit, I noticed several capacitors in the signal path. After reading much about the effects of caps in the SP, what kind (type, brand) do you think would give the best SQ in this application, or could you eliminate the caps altogether by eliminating the high pass filter and putting a low pass section between the input to the amp and ground? Somewhere I think I read about this approach but can't remember where or any details about it.
I'm using an active high pass filter before the amps driving my BLHs to keep out the low lows. In looking at the circuit, I noticed several capacitors in the signal path. After reading much about the effects of caps in the SP, what kind (type, brand) do you think would give the best SQ in this application, or could you eliminate the caps altogether by eliminating the high pass filter and putting a low pass section between the input to the amp and ground? Somewhere I think I read about this approach but can't remember where or any details about it.
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What is SP ?? It got me years to understand what SQ was, but now, SP ??
Radio frequencies filter is a low pass filter usually found at amp's input.
The coupling cap can/should be changed according to the HP function you want.
For example you have 1 uF cap at amp's input giving about 10 Hz Fc
Reduce it to 1/10 or less according to the formula 1/ 2π RC to have a corner frequency cut at 100 Hz
That should be easy.
Leave the active filter for lowpass for the subwoofer
You are just wasting 100 % signal as those circuitations are useless in that way.
Like you go out for shopping then after you throw everything in the waste.
Is your mind 90° rotated
About the original question, i.e. too many caps, as I interpretated it, you have your black box, the amplifier, and then you put a cap in line before it according to the 1/ 2π RC formula, right ? How much pF are you using ?
Saying that you have looked at the circuit, the amp, you might recall seeing a cap the input ( the coupling cap), so the natural answer to your question is to substitute that cap instead of having two caps in series. That involves opening the black box
Like you go out for shopping then after you throw everything in the waste.
Is your mind 90° rotated
About the original question, i.e. too many caps, as I interpretated it, you have your black box, the amplifier, and then you put a cap in line before it according to the 1/ 2π RC formula, right ? How much pF are you using ?
Saying that you have looked at the circuit, the amp, you might recall seeing a cap the input ( the coupling cap), so the natural answer to your question is to substitute that cap instead of having two caps in series. That involves opening the black box
I think these will better illustrate what I'm trying to do - use an active or passive 2nd order low pass filter between amp input (or buffer output) and ground to shunt low lows to ground and keep them out of my fullrange drivers. Don't know if it's possible, it seems counterintuitive to set the output of the op amp to ground, but, if I knew the answer to such questions I wouldn't have to be bugging you guys.
TIA
TIA
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The circuit in the post above will not work.
go at page 23 of this link and you will have the circuit from Texas Instrument, use polypropylene capacitors and it will work.
https://www.ti.com/lit/an/sboa093a/sboa093a.pdf
This is a classic circuit you will fin many application notes to deal with the values of components.
go at page 23 of this link and you will have the circuit from Texas Instrument, use polypropylene capacitors and it will work.
https://www.ti.com/lit/an/sboa093a/sboa093a.pdf
This is a classic circuit you will fin many application notes to deal with the values of components.
Yes I agree on Polypropylene (MKP with a generous voltage rating is what I use).
Silver-mica can works for very small values as well as C0G MLCC types.
Polystyrene is very good too on this application (somebody said even better) but styrene type caps are VERY temperature sensitive and they have a shorter expected life. This is the reason why they became kind of obsolete.
Silver-mica can works for very small values as well as C0G MLCC types.
Polystyrene is very good too on this application (somebody said even better) but styrene type caps are VERY temperature sensitive and they have a shorter expected life. This is the reason why they became kind of obsolete.
agreed, i find it amazing how people tend to learn snake oils faster than learning how the thing works...
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