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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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In Reply to: Help needed to determine capacitor purpose posted by banpuku on April 9, 2014 at 06:12:41:
The circuit is obviously an older design using a floating or self balancing paraphase phase inverter. The designer chose to use a very low cutoff freq for the phase inverting triode that requires a large value coupling cap. In the old days, caps of the nec value were either leaky electrolytics or somewhat less leaky paper types. What you see in the schematic is a trick used to mitigate the leakage issues while still maintaining an effectively large value coupling cap. While the highlighted portion will act as a form of a HP filter, that effect is incidental to the primary purpose of effectively producing low leakage coupling using inherently leaky parts.
The easy refurb approach would be to replace the caps with = values but of the greatest sonic neutrality...you be the judge of neutrality. I'd be looking a high quality PP at a min.
If you're more adventurous, you can model the circuit to determine the composite response and design a circuit using only 1 cap and 1 resistor that mimics it. This is how the circuit would be implemented today with modern, low leakage caps.
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- RE: Help needed to determine capacitor purpose - Steve O 11:14:18 04/09/14 (0)
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