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Author Topic: Vishay T63YB trim pot inside a U87ai  (Read 884 times)


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Vishay T63YB trim pot inside a U87ai
« on: May 01, 2020, 10:25:14 PM »

A fellow studio owner in Albuquerque recently lent me his U87ai for comparison to mine. Inside I found a Vishay T63YB 10k trim pot. What might be the purpose of this component?



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Re: Vishay T63YB trim pot inside a U87ai
« Reply #1 on: May 01, 2020, 11:04:42 PM »

That's one way to arrive at the optimal bias point for the FET. The trimpot takes the place of the fixed source resistor, and is adjusted for the lowest distortion/lowest noise when you feed in a 1K signal into the gate of the FET.
The other way: use a trimpot to find the quiescent point of the FET, and then install that value as a fixed resistor. Advantage: it won't drift like the trim pot tends to.
Klaus Heyne
German Masterworks®


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Re: Vishay T63YB trim pot inside a U87ai
« Reply #2 on: May 02, 2020, 11:17:01 AM »

...and does not introduce distortions like some trimpots do.
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