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Preamplifier 2012-part 1-capacitors

HiFi, LoFi, Tubes, Transistors, ICs, Commercial, DIY

Postby rob g » Sun Apr 22, 2012 12:00 am

For optimum electrostatic screening, the polarity of an axial capacitor at the input of sensitive amplifiers is often such that the outer electrode is connected to the equipotential common//earth side of the circuit. The markings in Figure 4 suggest that C1 and C2 might have their outer electrode connected to ground, but that C26 and C27 might not. At least one, and possibly both cases, do not follow past best practice described in my first sentence. Is past practice relevant to present-day low impedance circuits? I do not want to waste more time with a LCR meter sorting capacitors to identify the outer layer. Can any reader throw some light on this topic?
rob g
 
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Postby thijsbeckers » Mon Apr 23, 2012 12:00 am

Hi Rob,

Please have another close look at the photograph (Figure 4, april edition). Disregard the orientation of the characters printed on the C's (C1, C2, C26 and C27), but note the cylindrical markings on them. They are all on the 'inside', which means their outer electrodes are all connected to ground.
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Postby rob g » Tue Apr 24, 2012 12:00 am

You are correct- capacitor labelling in my print copy is somewhat unclear but the downloaded article clearly shows the outer layer marked. The 100 mark on C27 is reversed, possibly mirrored but most likely by a batch change.
Rob G
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