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Post by buelligan on Sept 25, 2008 23:15:23 GMT
I'm about to dip my toe in the modding pool and I had a question:
If the input impedance of the X-CANv3 is 100 KOhms, isn't a 10 uF cap quite oversized? In fact, wouldn't it actually pass DC for a short time?
If my math is right (a BIG if!), even a 2 uF cap would give a 3dB down point of about 0.8Hz.
Wouldn't a 2uF cap be more than enough?
Comments (and math corrections) welcome.
Thanks.
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Deleted
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Post by Deleted on Sept 25, 2008 23:44:30 GMT
Buelligan
No, it wouldn't pass DC for a short time. Where electrolytics are concerned, the idea is to eliminate any effects of distortion in the audio pass band. In the case of a transistor input stage, it also helps to minimise the source impedance "seen" by the input transistors. This appears to be more recent thinking. Apparently it's more about reducing noise. If the input capacitor is not an electrolytic, and the input impedance is quite high, as in this case, then reducing the value of the input capacitor as you have suggested, probably wouldn't make much (if any) difference.
SandyK
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Post by buelligan on Sept 26, 2008 1:26:07 GMT
Dear SandyK,
Thanks for your prompt response. I can't say I follow how an electrolytic would eliminate distortion in the audio band.
As far as I knew, the X-CAN v3 uses tubes in the voltage gain stage. I should have mentioned that I'm driving the X-CAN with the X-10 v3 buffer, so the input stage should see a pretty low impedance.
I guess my question is, would some 2 uF Auricaps cause any loss of bass extension?
Thanks again,
Buelligan
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Deleted
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Post by Deleted on Sept 26, 2008 1:58:50 GMT
buelligan
It is the much higher capacitance chosen for the electro,that helps reduce the distortion in the audio band. Obviously, an electrolytic can never sound as good as a high capacitance capacitor such as a polypropylene, but they are big physically, and more suited for speaker crossover networks etc. where physical size isn't a problem.
When used with the X-CAN V3 , because of it's high input impedance, the 2uF Auricap should be suitable. What type of capacitor does it use at present? I will email an explanation from Silicon Chip magazine.
SandyK
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rickcr42
Fully Modded
Rest in peace my good friend.
Posts: 4,514
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Post by rickcr42 on Sept 26, 2008 4:32:46 GMT
DC (DIRECT CURRENT)=0 Hz HZ stands for "cycles per second" therefore an AC signal is an ALTERNATING current so not DIRECT which is a straight line plot  |
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