Home

Hardware->

Stereo
width controller

English

Česky

Stereo width controller

Menu

Introduction

Circuit
description

Schematics
diagram

Chassis
wiring

Assembling

Component
view

Printed
circuit board

Photos

Parts

Links

End

Updates

Introduction

One friend ask me for creating of circuit which allow regulation of stereo
width. I doesn't designed circuit by myself because it exists on the internet
in more copies for example on Elliott Sound Products page
or in Texas Instruments example document. I designed for him printed circuit
board and simple dual power supply. Circuit allows on the one side regulation of
stereo width to pure mono signal. On the opposite side of regulation we get
suppression of signal, which exists in both channels. We can control width of
stereophonic base when for example are instruments expanded to a pointless
width. Effect is specially audible with headphones where is missing natural
mixing of channels in a space around listener and channels are completely
isolated. Some records are in this situation unhearable and "pull" the ears. I
designed for this circuit simple dual
power supply for max. 2x 100mA current.

Circuit description

On the input of circuit is connected operational amplifier IC1A and IC2A in
noninverting configuration and on his output is second IC1B and IC2B in
inverting configuration. Between their outputs is linear potentiometer whose
output is mixed with output of second channel. When the potentiometer is in
central position that on his central pin is zero volts and circuit practically
doesn't modify final sound. When the potentiometer is in one end position, that
on his output is present noninverted output of one channel and is mixed with
noninverted output of second channel. With this we get on both output same mixed
mono signal. In opposite end position is mixed inverted signal of one channel
with noninverted signal of second channel. We get on the output signal, which
completely supresses sound which was identical in both channels. This effect is
mostly used in karaoke systems where is supressed voice of singer which usually
sings in a center of space. Capacitors on the input block eventual DC current
and resistors 100R on the output prevents oscillations.

Schematics diagram

schematics
in Eagle 6 format

Chassis wiring

Chassis
wiring in Eagle 6 format

Assembling

First we check if all holes are correctly drilled. We begin with two wire
wraps and all resistors. Next we continue with precise IC sockets for operating
amplifiers (if we used them) and next we assemble all capacitors. Beware of
polarity! All electrolytic capacitors are oriented in a same direction. On the
end we assemble connectors and potentiometer. It can be soldered directly to the
board or we can connect them with wires. For connecting of power supply and
signal wires is better to use connectors, but we can also solder wires directly
to the board. Parts with SMD casing was not used now that soldering of
components is much simpler specially for amateurs without experience.

Component view

Printed circuit board

Board is designed single-sided with a big ground area and two wires. It
allows to create them in amateur conditions. I ordered it at small local company
Kohout Spoj.

PDF
format Eagle6
format

Photos

Parts

Almost all components are usually available. I ordered operational amplifiers
OPA2134 at Farnell company. In circuit we
can probably use NE5532 which doesn't have too much brilliant parameters but
they are much cheaper.

List of parts

name

value and type

quantity

R1, R2

10k 1%

2x

R3-R14

100k 1%

12x

R15

dual ganged 10k/N

1x

R16, R17

100R

2x

C1, C2

1uF/63V foil RM5

2x

C3-C8

10uF/50V electrolytic RM2

6x

IC1-IC3

OPA2134 DIL8

3x

J1-J2

Molex 4pin PSH02-04P

2x

J3

Molex 3pin PSH02-03P

1x

Socket IC1-IC3

Precise socket DIL8

3x

Links

http://sound.westhost.com/project21.htm
Stereo Width Controller

http://www.ti.com/litv/pdf/sloa064
A Differential Operational Amplifier Circuit Collection

http://www.ti.com/lit/gpn/opa2134
OPA2134 datasheet

http://www.ti.com/lit/gpn/ne5532
NE5532 datasheet

Dual
power supply 2x 12V 100mA

End

Circuit works according to expectations and produced special sound effects
according to potentiometer position. It allow nicely change width of
stereophonic base and analyse record mixing. Sound was without hearable
distortion and interference.

Updates

-

©2012 pavouk[at]pavouk.org