13/16

When the ratio of original signal and echo is changed, R5, R6, R9, R11 are also changed, and the characteristics of LPF

change too. Therefore, it is necessary to change all the constants of LPF. In the case, to precisely measure the ratio of

original signal and echo, remove R7, input signal around 500Hz without the influence of LPF from MIX IN, and compare

it with the output of DALPF OUT.

As for C,R, tolerance should be below 5%. Note: If measurement is made by attachment a probe oscilloscope it might

load the oscillator and reduce the oscillation frequency.

* The set values in this document are for reference only. In the actual set, characteristics may change according to board

layout, wiring, types of parts used, and therefore, in actual use, carry out sufficient verification with the actual devices.

IN

OUT

R4

R11

C4

C8

R6

R10

R5

R9

C5

C7

－

＋

9

R

5

R

11

R

4

R

2

A

1

A

9

R

11

R

2

A

5

R

4

R

1

A

0.7

Q

4

C

5

R

4

R

5

C

6

R

5

R

4

R

5

R

4

R

1

Q

5

R

4

R

5

C

4

C

2

1

fc

×

×

=

×

=

=

=

+

=

π

=

エコ－信号増幅率

ぐらい

は一般的に

Fig.35 LPF and echo system gain

Q generally about 0.7

Echo signal amplitude ratio