Owner's Manual

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Minimum Phase

Filter

20

-

20

-40

iii

-60

~

"'

-80

"0

3

-

~

·

100

~

120

-140

·

160

180

-

200

I

1-

-----t----

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i

--

--1--

I

, I

f-h--

0.1

0.2

0.3 0.4 0.5 0.6

0.

7

frequency/FS (in put sampling

rate)

Frequen

cy

response

i

.

--

-1 --

0.8

0.9

The Minimum

Phase filter

is another

highly regarded audio

filter

that

offers even

lower ripple

in the pass and stop bands.

Unlike

the Linear

Phase filter,

group

delay

is not constant; however, phase

shift

is low

and

the

particular

benefit with this

filter

is

that

the

impulse

response exhibits

no

pre-ringing.

Impulse res ponse

-=Ttl

-

+-1

= ~.

---r

. ' I

--+-

--

---

+--

---1

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--l-

--j-

I

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r--.

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I.

20

40

60

80

100 120

140 160 180

T

ime

(sa

mples)

azur

851C

Steep

Filter

Frequency

response

20

I

0

20

-40

iii

-60

~

"'

-80

'5

.t<

-100

&,

"'

:2'

120

-

140

160

-

180

-

200

0.1

0.2

0.3

0.4

0.5

0.6

0.7 0.8 0.9

frequency/FS

(i

nput

sampling

rate)

Our Steep

filter

is a

linear

phase

filter

that

has been optimised for stop

band attenuation

of

close-in aliasing

images. Here

we

have traded a

little

attenuation

of

the very highest frequency response (-2dB

at

20kHz

for 44.1kHz

material)

and a

little more pre- and post-ringing for a very

steep attenuation

just

outside the pass band. The Steep

filter

is

able

to attenuate aliasing

at

22kHz

by

some

80dB

for 44.1kHz

material

for

instance.

Impul

se

response

-

---1

-i-

--

20

40

60

80

100 120

140

1

60

180

Time

(samples)

Note:

All

filters

exhibit the same

ultimate roll-off

of approximately

140d8.

The following table

shows the

filter

stop band attenuation for 44.1kHz

material:

Linear

Phase

Minimum

Phase

Steep

Roll-off

at

-0.1dB

-0.1dB -2dB

20kHz

Roll-off

at

-10dB -10dB

-82dB

22kHz

Ultimate roll-off

140dB

140dB 140dB

We

encourage you to experiment with the

filters

to determine which

sound best to your ears and using your source equipment/programme

material.

The 851C remembers and

recalls

the

selected filter

type for

each input

individually,

making

it

possible,

for example,

to

select Steep

for the

USB

input and Linear

Phase

for

Digital Input

1, and

so

on.

13

I