[sdiy] mixer

[Antti Huovilainen]

On Thu, 1 Nov 2001, Glen wrote:

> Isn't that excessively high? Remember, the higher the input resistance value,
> the higher the background noise will be. All the line-level equipment that I

Not quite. The higher the source resistance looking at the amp is, the
higher the noise. Source resistance consists of driving stage output
impedance in parallel with the mixer input resistance. So if the source
has low impedance, the input impedance looking at teh mixer op-amp is
dominated by that. So if the input resistance is 47k and the driving
impedance is, say 1k, then the total resistance is about 0.98kohm ~ 1kohm.
The rule of thumb is to have input impedance >= 10 x driving stage output
impedance.

Antti

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 How can you have any pudding if you don't eat yer meat!?"
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