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In Reply to: RE: Removing the input coupling caps?? posted by Tweaker456 on August 19, 2014 at 13:22:00
An input cap blocks DC and it also forms a high pass filter. Many designs from the 50s and 60s had input caps. In the above schematic, the 0.1uf cap and the 33pf are filters. Could you remove them, probably as CD players do not have wide-band noise problems. Should you? You can do whatever you want, modern designs typically do not have input caps unless the first stage is a cathode follower. It is unlikely to blow anything up.
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Looks like triode kingdom answered the ? 10k Tweaker
This removal could in theory allow for hiss type noise in. Thanks for the heads up on this. I'm a bit rusty. Can you tell me what is the crossover point on a .1?? Thanks, Tweaker
no hiss , I mixed up hi and low pass.
it's part of a network. Simplistically, the 0.1uF cap in conjunction with the 470K resistor would form a high pass filter with a -3db point around 4-5 Hz (too lazy to calculate). However, the 47k resistor in series, in conjunction with the little pF value cap in parallel together form a low pass filter, apparently for RF, per TK's post.
The 0.1 is not intended to be a filter, although it does create a slight rolloff in the 10Hz region. Its actual purpose is to block any DC that's present at the source. The 33pF/470k combination is a low pass filter to attenuate RF (broadcast stations, ham radio operators, etc.) It's a little too close to the audio band for my taste, and I would remove it. A 200kHz LC low pass would be a better choice, but only if needed in order to solve a problem in a particular situation.
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Buy Chinese. Bury freedom.
I was addressing any possible stability effects in addition to the DC blocking.
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