that1512 THAT Corporation, that1512 Datasheet - Page 6

• Manufacturer Part Number: that1512
• Description: Low Noise, High Performance Audio Preamplifier Ic
• Manufacturer: THAT Corporation

Page 6
in order to limit peak currents enough to protect the
zener diodes. In such cases, these resistors will limit
the noise performance of the preamp. The ultimate
floor is set by the impedance of the microphone, but
any additional series resistance further degrades per-
formance.
Input Impedance and Line Input Configurations
desirable (compared with that of Figures 2 and 3),
especially when a mic pre-amp input is configured to
double as a line receiver. The circuit of Figure 4 also
accommodates this objective. In this circuit, R1 and
R2 are increased to 10kW, boosting the low-frequency
common-mode input impedance from 500 W to about
2 kW. A value of 2.7 kW for R9 keeps the differential
input impedance at 2 kW without reducing the com-
mon-mode input impedance.
A higher common-mode input impedance may be
A line input can then be added by connecting
-In
+In
6k8
C2
470p
47p
470p
R6
C1
C3
+48V
THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA
Tel: [phone]; Fax: [phone]; Web: www.thatcorp.com
2k7
R9
Figure 4. Recommended 1510 / 1512 Circuit with Phantom Power
R5
6k8
47u
47u
C5
C4
4R7
4R7
R3
R4
Copyright © 2007, THAT Corporation
+15
1N4004
1N4004
D4
D3
D1
1N4004
1N4004
D2
5.1 kW resistors from the line input’s + and - input
terminals to the positive and negative inputs, respec-
tively, of the 1510/1512 of Figure 4. This increases
the differential line input impedance to ~12.2 kW,
and results in a net attenuation (pad) of
mately 15.7 dB between the line input and the output
shown in Figure 4. Since, in many pro audio appli-
cations, the minimum pre-amp gain is 10 dB, the
pad effectively cancels out this minimum gain while
adding an additional 6dB of attenuation, which al-
lows the resulting line input to accommodate high
line level signals.
Reference Terminal
signal, and is normally connected to analog ground.
If necessary, the “Ref” pin can be used for offset cor-
rection or DC level shifting.
source resistance will reduce the IC’s common-mode
rejection (CMR) by the ratio of 10 kW/R
The “Ref” pin provides a reference for the output
-15
10k
R1
10k
R2
THAT 1510 / 1512 Audio Preamplifier IC
RG
-In
RG1
RG2
+In
-15
V-
+15
V+
100n
Ref
C9
A non-zero reference
100n
C6
Out
THAT
1510/1512
U1
REF
.
Out
approxi-