I am building an amplifier based on instructions found in “A Complete Guide to Design and Build A Hi-Fi LM3886 Amplifier.” I am designing my own PCB, since I have not found a commercial one that will fit my existing heatsink and chassis. The design calls for a 4.7 µF input coupling capacitor. I am debating between using a quality electrolytic (Nichicon UFW) or a film type (MultiCap) mounted vertically – horizontal mounting is not a option due to board size constraints. The film type is probably preferred, but I am concerned about the vertical mounting. Any thoughts or advice would be appreciated.
Cheers,
ceulrich
Cheers,
ceulrich
You can vertically mount it, but it´s good Engineering to "fix" it to the board with some kind of glue (hot melt/contact cement/electronics grade silicone) to protect it against vibration.
Since it´s a relatively heavy component, and mounted on edge hanging from just one flimsy leg, vibration may eventually break it, so the glue avoids that.
Since it´s a relatively heavy component, and mounted on edge hanging from just one flimsy leg, vibration may eventually break it, so the glue avoids that.
Thanks everyone for your comments.
JMFahey: Yes, I will definitely do that.
rayma: I do not understand the reason for the spacer. My first thought is that this would make the component less stable. Could you please clarify?
scottjoplin: I never thought about that. Would it make any difference if that lead was wired to be the input or the output of the capacitor?
DF96: Yes, good thought. The design calls for 4.7µF with an input resistance of 20K, which puts the -3dB point at 1.69Hz, probably a bit of over kill. I happen to have some 3µF MultiCap units in my parts collection, so I was going to use them. That would put the -3dB point at 2.65Hz, still quite low. I could go down to 1µF for a -3dB point of 7.96Hz, but I still have a component length problem, at least with the parts I have.
Cheers,
ceulrich
JMFahey: Yes, I will definitely do that.
rayma: I do not understand the reason for the spacer. My first thought is that this would make the component less stable. Could you please clarify?
scottjoplin: I never thought about that. Would it make any difference if that lead was wired to be the input or the output of the capacitor?
DF96: Yes, good thought. The design calls for 4.7µF with an input resistance of 20K, which puts the -3dB point at 1.69Hz, probably a bit of over kill. I happen to have some 3µF MultiCap units in my parts collection, so I was going to use them. That would put the -3dB point at 2.65Hz, still quite low. I could go down to 1µF for a -3dB point of 7.96Hz, but I still have a component length problem, at least with the parts I have.
Cheers,
ceulrich
0.47uF for a rolloff around 15Hz might be better.
Alternatively, just use the electrolytic. If you are worried about distortion then use a slightly higher value, say 10uF or 22uF.
I tend to use 10uf or 470nf poly caps on the input.
Never had any problems with either.
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