1510/1512 Audio Preamplifier
Demonstration System
THAT
1510/1512-DEMO
Description
The THAT 1510/1512 Demo Board is a self-
contained circuit board that simplifies the evalua-
tion of the THAT1510 and THAT1512.
Completely assembled and tested, this system
comes with XLR connectors for signal input and
output, and 3 pin headers for standard and
phantom power.
J1 is a Female XLR connector that accepts a
balanced (or unbalanced) input signal, while P1,
a male XLR connector, is connected for an unbal-
anced output. An external ±15V power supply
for the IC should be connected via header P3,
along with an external +48V phantom power
supply connected via header P2.
C5, C6, and C10 shunt unwanted RFI
currents to chassis ground. The "T" arrangement
of these components minimizes CMRR degrada-
tion at higher frequencies resulting from any
mismatch between C5 And C6; (the shunt paths
for each input share C10, and C10's contribution
to the effective shunt impedance of each side
dominates that of C5 and C6).
When phantom power is applied, there is the
potential for the phantom power circuitry to
attempt to take the IC's inputs above the rail and
outside the common mode input range of the
THAT 1510/1512. This demonstration system
has phantom power soft start that remedies this
situation. In this portion of the circuit, Q1 acts
as an emitter follower, and the time constant of
R6 and C12 determines the instantaneous rate at
which the phantom power rises. D7 is included
to keep the base-emitter junction of Q1 from
being damaged by being reverse biased. When
phantom power is disconnected, D1 also closes
the path for the residual charge stored on C1 and
C2 to discharge through R6 and R7.
4-40 Threaded
Standoff (4 pl)
THAT 1510/1512
Demo Board
Phantom
Power
Circuit Design © 2002
THAT Corporation
R14
R15
SW1
1 2 3 4
ON
Gain
+10
+20
+40
+60
R2
1
R7
R6
D7
GND
P2
+
+ C9
R24
OUT
Q1
+
C5 R1
C12
3.500
C2
+
R9
C10 R11
+
C1
R8
R13
R12
R16
P1
D6
D4
R4
R3
U1 C3
R5
TP4
3.100
C6
D5
D3
C4
C24
J1
IN
R21 C23
R20
U21
OPTIONAL
SERVO
C21
D2
C22
R23 TP2
D1
TP1
+
P3
C7
V+
Y1
Y2
TP3
+
R22
C8 1
V-
.200
3.600
4.000
Figure 1. THAT 1510/12 Demonstration System Layout
0.200
THAT Corporation; 45 Sumner Street; Milford, MA 01757-1656; USA
Tel: +1 508 478 9200; Fax: +1 508 478 0990; Web: www.thatcorp.com
Copyright
©
2005 - 2012, THAT Corporation; All rights reserved. Document 600038 Rev 03
Document 600038 Rev 03
Page 2 of 4
THAT 1510/12 Audio Preamplifier
Demonstration System
All integrated circuit mic preamps are
vulnerable to phantom power faults. There are
two primary situations where these faults
typically occur:
In the first situation, the
phantom power is applied but the input of the
mic preamp is unconnected and floating. There
will be +48V (relative to chassis ground) on C1
and C2.
If the mic preamp is accidentally
connected to a line driver output in another
device, the positive sides of these capacitors are
driven to the potential of the positive rail of the
line driver. C1 and C2 will instantaneously
behave as batteries, and attempt to drive the
inputs of an unprotected mic preamp to some
minus potential, typically -25 to -30 VDC. This
will typically result in destructive currents
running through parasitic junctions in the IC.
The second scenario results when a mic preamp
is connected through a patch bay. If phantom
power is applied, and the tip-ring-sleeve connec-
tor is either inserted or removed, destructive
currents will flow as the tip and ring of the
connector are dragged across the contact which
is intended to connect the sleeve to ground.
The THAT 1510/1512 demo board has
protection diodes to address these scenarios.
These diodes shunt potentially destructive
currents to the rail before they can turn on
junctions inside the IC. R8 and R9 limit the
maximum current without severely affecting noise
performance. Note that 1N4148s and the like will
not work in this application, since they are not
rated for the peak currents that can be expected.
Likewise, back-to-back zeners won't work for the
same reason. Either the currents are too high, or
R8 and R9 must be increased to the point that
their noise contribution becomes an issue. Using
larger zeners or tranzorbs will typically introduce
distortion due to their non-linear input
capacitance.
SW1 allows the gain of the THAT1510 or the
THAT1512 to be switched in discrete steps of
zero dB, 10dB, 20dB, 40dB, and 60dB. Values
for a given gain resistor (shown in Table I of the
schematic) were derived using the equation
A
V
=
1
+
A
V
=
1
2
10k
R
G
5k
R
G
for the THAT1510 and
for the THAT1512.
+
There is a large electrolytic capacitor in
series with the gain resistor network which helps
avoid "thumps" when switching gain.
This
component is one of the largest components the
circuit, and in SMT implementations, it may take
up as much as 40% of the board area. Addition-
ally, it serves as a good antenna for picking up
unwanted noise due to its size. We've included
the circuitry (unpopulated) for an optional servo
which can replace this capacitor. Table II of the
schematic shows the parts required to implement
the servo circuitry.
To ease prototyping of specific applications,
spare circuit board area is perforated with plated
through holes. This makes this board particu-
larly useful for experimentation.
With a THAT 1510/1512 Demo Board and
standard audio cables, an engineer can begin to
evaluate the performance of the THAT 1510/1512
microphone preamplifiers in seconds, and start
trying out new circuit ideas in minutes.
THAT Corporation; 45 Sumner Street; Milford, MA 01757-1656; USA
Tel: +1 508 478 9200; Fax: +1 508 478 0990; Web: www.thatcorp.com
Copyright
©
2005 - 2012, THAT Corporation; All rights reserved.
1
Rev
Description
Date
2
3
4
5
6
Approved
This document and the data disclosed herein or herewith is not to
be reproduced, used, or disclosed in whole or in part to anyone
without the written permission of THAT Corporation.
+48V Phantom Power
P2
Q1
2SC1815
R6
22k1
R7
100k
SW1-4
SW1-3
V+
SW1-2
SW1-1
None
2
1
3
2
1
A
A
Header 3x1
Closed
60 dB
40 dB
20 dB
10 dB
0 dB
IN-
RG1
7
Document 600038 Rev 03
Input
J1
XLR-F RA
D7
1N4148
Gain
C12
22u
63V
Phantom
Power
Protection
R8
10R0
D3
1N4004
R15
SW1
Table I
C9Tables I & II
R14
Table I
R13
Table I
DIP4
Gain
R24
Table II
R22
Table II
2
3
5
2
1
3
C28
22u
63V
R1
6k81
C1
Table II
R16
V+
V-
D5
1N4004
R12
Table I
R4
Table II
C27
100p
Table II
8
6
1
R2
6k81
D4
1N4004
D8
1N4148
U1
1510P08-U
V+
5 4 2 3 1
C3
100n
V+
OUT
REF
6
Output
P1
XLR-M RA
1
2
3
TP5
B
C10
R11
Not Used
Table I
1
2
3
4
8
7
6
5
C5
470p
NP0
R3
Table II
C26
100p
Phantom C25
Power
220p
Protection NP0
TP4
R5
100R
8
3
1 3 2 4 5
B
47p
NP0
C2
R9
10R0
D6
1N4004
Optional
Input
C21
Servo
V-
Table II
R20
Table II
R21
Table II
C6
470p
NP0
RG2
IN+
V-
4
5
TP3
Y2
0R
Ref Lift
D9
1N4148
C4
100n
V-
Page 3 of 4
RFI
Protection
C
U21A
Table II
TP1
V+
C23
100n
U21B
Table II
C24
100n
Table I
V+
C
C22
Table II
R23
Table II
Power
P3
C7
22u
7
Figure 2. THAT 1510/1512 Demonstration System Schematic
Ground Lift
Y1
V+
V-
4
3
2
1
D1
1N4004
0R
THAT Corporation; 45 Sumner Street; Milford, MA 01757-1656; USA
Tel: +1 508 478 9200; Fax: +1 508 478 0990; Web: www.thatcorp.com
Copyright
©
2005 - 2012, THAT Corporation; All rights reserved.
C8
22u
TP2
V-
Table II
R12
R13
R14
R15
R16
C9
THAT 1510
Demo
Board
10R0
100R0
1k10
4k64
-
3300u /10V
THAT1512
Demo
Board
4R99
49R9
549R
2k32
10k0
6800u /6.3V
Release Approvals
Proj. Eng.:
Title:
Header 3x1
D2
1N4004
V-
D
THAT Corporation
FWT
Production:
JJG
QA:
Date:
Date:
45 Sumner Street
Milford, MA
508-478-9200
D
Unless otherwise noted:
1. All resistors are 1/4W, 1%, M.F. types.
2. All capacitors are 20% tolerance.
3. All NPO capacitors are 5% tolerance.
4. Refer to Table I for 1510 and 1512 specific component values.
5. Refer to Table II for optional input servo values.
R3, R4
R20, R21
R22, R23
R24
C1, C2
C9
C21, C22
C23, C24
U21
Without
Optional
Servo
1k15
-
-
-
47u/63V
See Table I
-
-
-
With
Optional
Servo
100k0
2M21
100k0
0R
2u2/ 100V
-
100n MY
100n
LT-1012
2/22/02
2/12/02
ADW
3
4
Date:
Size:
151x Demo Board
B
2/22/02
5
Drawing Number:
Date: 10/6/2010
File:
Drawn by: RB
Revision:
Sheet 1 of 1
THAT 1510/12 Audio Preamplifier
Demonstration Sysytem
1
2
6
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