7 Temmuz 2010 Çarşamba

Preamplifier

What is a preamplifier?

A preamplifier is the first stage of input in an audio system. It selects the input, amplifies the input signal, adjusts volume, balance, tone and then outputs the signal to the power amplifier and other devices like headphones or recorders. The preamplifier is also a buffer to the power amplifier and adjusts impedance levels of the inputs and probably provides some protection.


A Beautiful NAD Preamplifier

Patrick's preamplifier, which is all of the above except that it does not do any balancing, is built of audio grade high quality parts all around. It's op-amp based (Burr-Browns all the way) and has a Baxandall type tone control. The circuit is based on Rod Elliott's "Hi-Fi Preamplifier". Rod Elliott's pages are the first address I check before building anything.

The preamplifier is of course hidden inside the body of Patrick where his Adam's apple would be located. Only the volume adjustment pot is outside on the cabin. Tone controls are left inside the cabinet, I don't think they will need much fiddling. 

The gain of the preamplifier is 6 V/V. Gain has been kept a little high because the device will be used with MP3 players which usually have very low output levels. Did you know that an iPod has a maximum RMS level of 0.33 Volts?

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