Ideally the Voltage at the TP. should = ((Supply Voltage/2) - 0.6 volts)

Revised "Feb 18 2004"
REVISED "JAN 31 2007" Better Picture Overlay and Minor Corrections.

R1 sets Gain, typical 470 ohms.
R2 = Feed back Resistance, Typical 47K for flat response
R2/R1 = Gain

Open Loop Gain = 1250 @ 1000 Hz.
1.6 mv in = 2 volts out if supply voltage is 15 volts.

Frequency Response 10 Hz to 50 Khz. if supply voltage is 40 volts.

With a 40 Volt Supply, Distortion = less than 0.03% at 4 volts output,
Increases to 0.2% at 10 volts output.

Not Shown on the Schematic, But on the Board is an Optional Supply Filter Cap,
Also Provisions for an output control and blocking cap.

This is a Very Versatile Preamp and other than the two compensation

networks that are shown, you can create Many Others.

For Example: NATB which is a Tape Compensation,

Or create Greatly Emphanzied Low or High Frequency output,

Or Reverse RIAA Compensation.


Etched and drilled PCB's are available,

And the other parts also, If Needed.







 Schematic

 "Circuit Boards"



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 Chemelec 
 *Copyright © 2004 & 2007*