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beat dis 28th November 2008 09:21 PM

lm 4563 balanced mic preamp
is there any scheme or complet project of good (studio condenser) mic balanced preamp with lm 4562?
thanx for any information.

Keith Taylor 30th November 2008 12:18 PM

The FET input LM4562 op amp would not be a good choice for a balanced microphone preamp. Noise performance tends to be the critical factor and bipolar transistors give lower noise figures than FETs for the source impedances presented by microphones. You should investigate chips that have been designed as preamplifiers for microphones by makers such as THAT Corp and Analog Devices/Texas Inst'

Two that come to mind are THAT1510 and Texas INA163
There are more specialist forums than this one dealing with this subject. One is the Prodigy Pro forum and another is

sparcnut 30th November 2008 03:33 PM

Isn't the LM4562 BJT-input?

Keith Taylor 1st December 2008 10:18 AM

Sparcnut, you seem to be right, but this is not something that NS are very helpful about. Douglas Self has it described as BJT input, and the bias current figure at 10nA seems to indicate this. What led me astray was that some owners of the Linkwitz Orion speaker were trying LM4562's in place of OPA2134 in the active crossover, perhaps bedazzled by the low distortion figures but not realising that substituting BJT input op amps in circuitry designed for FET's is not a good idea.
The remarks about choosing purpose designed op amps still apply, however.

beat dis 1st December 2008 02:56 PM

thank you keith.i didn t know that.friends told me this chip is practicly noiseless,so i thought it will be good idea.

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