Amplifier White Noise

[Edu Silva]

Cal Grant wrote:
>
> I would personally go with a extra low noise opamp, such as the LT1128 or
> LT1028, or cheaper, the OP27. The LT1124 is also a good choice. There's
> always the  5534, which is cheaper. All these units can be run on single
> supply if carefully biased, respecting traditional low noise electronic
> design rules.
> 
> Whatever, keep input sources resistance low and any feedback resistors as
> low as possible as well.

OK, but seems that the main reason Scott choose a FET was the high Zin
he needs, to load properly the contact mic. A crystal unit, I guess. I
had built these things as preamps for acoustic guitar pickups, and FET's
sounds better here, not only due to the high input Z, but because of
it's (kind of) soft distortion when overexcited. Even FET-input opamps
need to be selected with care: not all (if any) can give the same smooth
sound a single FET can.

Edu Silva
ES2 Audio
http://audiolist.cjb.net