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Author Topic: freq response and aliasing of Edirol FA-101 at 192 kHz  (Read 1442 times)

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freq response and aliasing of Edirol FA-101 at 192 kHz
« on: August 10, 2004, 02:33:35 PM »
Pulled this off laptop tapers, thought it would be useful archival info.

Take care,
Ben






Message: 1         
   Date: Tue, 10 Aug 2004 13:01:24 +0200
   From: Gianni Pavan <gpavan@cibra.unipv.it>
Subject: freq response and aliasing of Edirol FA-101 at 192 kHz

Hi all,
   I'm testing the new Edirol FA-101 to verify its performances at 96 and
192
kHz.
Performances at 96 kHz are as expected, with a flat response up to 42
kHz
and sharp filtering close to Nyquist.

On the contrary, performances at 192 kHz are really unsatisfactory. The
unit behaves completely different, with a roll-off that begins at 30
kHz
and scarcely attenuates beyond the Nyquist frequency. Frequencies above
Nyquist are poorly attenuated and thus, if they are present in the
analog
signal, they can fold back down to 40 kHz.

Given a sinusoidal input signal of 8Vpp on the LINE INPUT (much less
than
the overload level, of course), by varying frequency I get the
following
response:

30 kHz, 0 dB (arbitrary)
36 kHz, -0.14
39 kHz, -0.22
42 kHz, -0.325
45 kHz, -0.46
48 kHz, -0.64
51 kHz, -0.885
54 kHz, -1.22
57 kHz, -1.66
60 kHz, -2.23
63 kHz, -2.955
66 kHz, -3.85
69 kHz, -4.95
72 kHz, -6.28
75 kHz, -7,87
78 kHz, -9.77
81 kHz, -12.065
84 kHz, -14.855
87 kHz, -18.355
90 kHz, -23.03
93 kHz, -30.375
94 kHz, -34.45
95 kHz, -41.0
96 kHz - difficult to measure

and now, by increasing the input frequency beyond Nyquist, I get the
following values for "aliased frequencies":

(real input freq -> aliased freq, level of aliased freq vs input level)
97 -> 95 kHz, -42.0
98 -> 94 kHz, -36.5
99 -> 93 kHz, -33.485
102 -> 90 kHz, -29.25
105 -> 87 kHz, -27.7
108 -> 84 kHz, -27.35
111 -> 81 kHz, -27.75
114 -> 78 kHz, -28.7
117 -> 75 kHz, -30.07
120 -> 72 kHz, -31.82
123 -> 69 kHz, -33.92
126 -> 66 kHz, -36.34
129 -> 63 kHz, -39.08
132 -> 60 kHz, -42.18
135 -> 57 kHz, -45.58
138 -> 54 kHz, -49.3
141 -> 51 kHz, -53.5
144 -> 48 kHz, -58.3
147 -> 45 kHz, -63.8

By the way, I tested the LynxTwo PCI boards that exhibits very sharp
filters and flat bandwidth up to 90 kHz!

Now I wonder about the performances of the relatively cheap hard-disc
recorders now available, in particular the Fostex FR2: is there
somebody
able to test their performance with ultrasonic signals like I did with
the
FA101 ?

Gianni
--------------------------------------------------------------
Gianni Pavan
Email gpavan@cibra.unipv.it
Centro Interdisciplinare di Bioacustica e Ricerche Ambientali
Universita' degli Studi di Pavia
Via Taramelli 24, 27100 PAVIA, ITALIA
Tel        +39-0382-507874
Fax        +39-02-700-32921
Web       http://www.unipv.it/cibra


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