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Author Topic: So you need a preamp - here are your options  (Read 45040 times)


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Re: So you need a preamp - here are your options
« Reply #30 on: April 08, 2008, 02:55:31 AM »

I have a few different setups myself , however , here is the real deal a power amp requires 1 to 2.6 volts to operate correctly. most of the new stompbox multi effect monsters(Roland , Digitech) can put out up to 2 volts , plenty to drive any good power amp.

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Re: So you need a preamp - here are your options
« Reply #31 on: May 03, 2014, 08:42:32 AM »

From the NatSemi datasheet;

Low Voltage Audio Power Amplifier

General Description
The LM386 is a power amplifier designed for use in low voltage
consumer applications. The gain is internally set to 20 to
keep external part count low, but the addition of an external
resistor and capacitor between pins 1 and 8 will increase the
gain to any value from 20 to 200.

The inputs are ground referenced while the output automatically
biases to one-half the supply voltage. The quiescent
power drain is only 24 milliwatts when operating from a 6 volt
supply, making the LM386 ideal for battery operation.

n Battery operation
n Minimum external parts
n Wide supply voltage range: 4V–12V or 5V–18V
n Low quiescent current drain: 4mA
n Voltage gains from 20 to 200
n Ground referenced input
n Self-centering output quiescent voltage
n Low distortion: 0.2% (AV = 20, VS = 6V, RL = 8W, PO =
125mW, f = 1kHz)

note: comes in two versions;
low LM386N, M-1 12Vsup/0.75Wout, and
high LM386M-4 18Vsup/1.5Wout.

Vsup = 12V
Voutpk = 6V

Av = +26dB (from datasheet)
dB = 20 * log10(Av)
10^(26/20) = 19.95262315 times

Gain = x20

6/20 = 0.3V or 300mVpk in for full output.
If you say theory and practice don't agree you haven't applied enough theory.
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