High Quality simple design
20V to 30V supply Circuits.
Circuit diagram
Parts:
P1_________________10K Log.Potentiometer (Dual-gang for stereo)
P2________________100K Log.Potentiometer (Dual-gang for stereo) (See Notes)
R1,R2_____________100K 1/4W Resistors
R3,R6______________15K 1/4W Resistors
R4_________________10K 1/4W Resistor
R5_________________22K 1/4W Resistor
R7__________________1K 1/4W Resistor
R8________________560R 1/4W Resistor
C1,C2,C5____________2µ2 63V Electrolytic Capacitors
C3________________470µF 35V Electrolytic Capacitor
C4__________________1µF 63V Polyester Capacitor
C6_________________47nF 63V Polyester Capacitor
C7_________________22µF 25V Electrolytic Capacitor
IC1_______________TL072 Dual BIFET Op-Amp
SW1________________DPST Switch (Optional, see Notes)
Comments
This preamplifier was designed to cope with CD players, tuners, tape
recorders etc., providing an ac voltage gain of 4, in order to drive
less sensitive power amplifiers. As modern Hi-Fi home equipment is
frequently fitted with small loudspeaker cabinets, the bass frequency
range is rather sacrificed. This circuit features also a bass-boost, in
order to overcome this problem. You can use a variable resistor to set
the bass-boost from 0 to a maximum of +16dB @ 30Hz. If a fixed, maximum
boost value is needed, the variable resistor can be omitted and
substituted by a switch.
Notes:
- Schematic shows left channel only, but R1, R2, R3 and C1, C2, C3 are common to both channels.
- For stereo operation P1, P2 (or SW1), R4, R5, R6, R7, R8 and C4, C5, C6, C7 must be doubled.
- Numbers in parentheses show IC1 right channel pin connections.
- A log type for P2 ensures a more linear regulation of bass-boost.
- Needing a simple boost-in boost-out operation, P2 must be omitted and SW1 added as shown in the diagram.
- For stereo operation SW1 must be a DPST type.
- Please note that, using SW1, the boost is on when the switch is open, and off when the switch is closed.Electronics Circuit Application
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