Can someone please help with the equation at the bottom of the diagram?
I have some headphones with a frequency response of 16Hz to 22kHz and and impedance of 24 ohm's, but no matter how I manipulate the equation, I can't seem to work out the output cap value (C2).
Thankyou.
Chris.
I have some headphones with a frequency response of 16Hz to 22kHz and and impedance of 24 ohm's, but no matter how I manipulate the equation, I can't seem to work out the output cap value (C2).
Thankyou.
Chris.
Attachments
You don't need to manipulate the equation, just stick in your values. They're assuming an LF cut-off frequency of 10Hz, I'd go a bit lower myself as a 10Hz -3dB point introduces phase distortion below 100Hz.
But assuming you want to follow their equation then C2 (in microfarads) is 1E6/(2*pi*10*24) which my calculator says is 663uF. I'd be inclined to use 2,200uF myself.
<edit> don't forget to heatsink the LM317
But assuming you want to follow their equation then C2 (in microfarads) is 1E6/(2*pi*10*24) which my calculator says is 663uF. I'd be inclined to use 2,200uF myself.
<edit> don't forget to heatsink the LM317
Last edited:
Hi,
Its just a re-arrangement of R=1/(2piFC) for a 1st order filter.
I do not see why "must" comes into it, 2,200uF will be fine
for any headphones (the min is 8 ohms & any higher value).
/Sreten.
Its just a re-arrangement of R=1/(2piFC) for a 1st order filter.
I do not see why "must" comes into it, 2,200uF will be fine
for any headphones (the min is 8 ohms & any higher value).
/Sreten.
Doh!!!!
Thank's, it was giving me a headache. I (stupidly???) assumed that the calculation gave the answer as farad's as opposed to uF's. That's why I couldn't see it.
I'm using 470uF at the moment. Will this be too low, and if so, how will it affect the circuit/sound?
Chris.
Thank's, it was giving me a headache. I (stupidly???) assumed that the calculation gave the answer as farad's as opposed to uF's. That's why I couldn't see it.
I'm using 470uF at the moment. Will this be too low, and if so, how will it affect the circuit/sound?
Chris.
470uF just means that you'll get more bass roll-off, and I guess that subjectively the bass will sound 'slower' than with 2,200uF. The bigger value I imagine will 'tighten' the bass.
Hi,
Its actually quite the opposite with manipulating bass roll offs.
FWIW 470uF is a fine value for typical walkman type headphones.
They are around 32 ohm, yours are lower than typical but will
still be fine with 470uF. Only if you want 8ohm compatibility
do you need to increase it, to between 1,100uF and 2,200uF.
And FWIW the equation is wrong, it should read C(uF) = ....
/Sreten.
Last edited:
So you've listened and found that a smaller cap tightens the bass and a bigger one slows it down? Which 'phones did you hear that with?
Hi,
No I've done it with hifi systems, higher up I admit, but I cannot see why it would change lower down.
/Sreten.
So you're saying the opposite to what I said is true, based on speakers and at higher frequencies?
Whereas I've worked with digital systems which correct for phase distortion at low frequencies and together with colleagues (on speakers) have clearly heard improvements in bass when LF phase distortion is corrected. The subjective effect is tighter bass.
<edit> ever noticed a difference in bass tightness between a ported and an IB speaker?
Whereas I've worked with digital systems which correct for phase distortion at low frequencies and together with colleagues (on speakers) have clearly heard improvements in bass when LF phase distortion is corrected. The subjective effect is tighter bass.
<edit> ever noticed a difference in bass tightness between a ported and an IB speaker?
Last edited:
Duly fitted with Elna Silmic II's, bypassed with 1uF Wima Poly caps, and it sounds fine. No flabby bass, and the treble is very, very sweet.
Chris.
Chris.
- Status
- Not open for further replies.