Listen AmpConnect621 User manual

PN: 8072 Rev 042622
AMPCONNECT 621 USER MANUAL
© COPYRIGHT 2020 - 2021 LISTEN, INC.

Rev 042622

AmpConnect 621TM Instruction Manual Contents i
Contents
Contents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i
Limited Warranty. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii
Product Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Front Panel Indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Back Panel Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
System Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Test Connections and Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Microphone Array - Power Averaging. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Single Loudspeaker Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Two Loudspeaker Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Microphone Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Hardware and Calibration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
SoundCheck Hardware Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Latency Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
AmpConnect 621 Hardware Configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Listen Hardware Tab. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
SoundCheck Calibration Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Self Test Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Amplifier Calibration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Microphone Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
AmpConnect 621 Message Step . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
USB Control Via SoundCheck . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
AmpConnect 621 Message Step . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Digital I/O Message Steps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Digital I/O Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Digital I/O Message . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Digital I/O Write Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Digital I/O Read Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Contents

ii Contents AmpConnect 621TM Instruction Manual
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Equipment Ratings and Approvals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
CE Declaration of Conformity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Important Safety Precautions And Symbol Explanations . . . . . . . . . . . . . . . . . . . 43
Vigtige Sikkerhedsforskrifter Og Symbolforklaringer . . . . . . . . . . . . . . . . . . . . . . 45
Explications Importantes des Symboles et des Précautions de Sécurité . . . . . . 47
Wichtige Sicherheitsvorkehrungen und Symbol-erklärungen . . . . . . . . . . . . . . . 49
Información de Seguridad y Símbolos . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Listen Software License Agreement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
INDEX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

AmpConnect 621™ Manual Limited Warranty iii
Limited Warranty
LISTEN, Inc., a Massachusetts Corporation, having its principal place of business at 580 Harrison Ave,
Suite 3W, Boston, MA 02118 (Manufacturer) warrants its AmpConnect 621TM products (the Products) as
follows:
1. Limited Warranty.
Manufacturer warrants that the Products sold hereunder will be free from defects in material and
workmanship for a period of one (1) year from the date of purchase. If the Products do not conform to this
Limited Warranty during the warranty period (as herein above specified), Buyer shall notify Manufacturer in
writing of the claimed defects and demonstrate to Manufacturer satisfaction that said defects are covered
by this Limited Warranty. If the defects are properly reported to Manufacturer within the warranty period,
and the defects are of such type and nature as to be covered by this warranty, Manufacturer shall, at its own
expense, furnish, replacement Products or, at Manufacturer's option, replacement parts for the defective
Products. Shipping of the replacement Products or replacement parts shall be at Buyer's expense.
2. Other Limits.
THE FOREGOING IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT
NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE. Manufacturer does not warrant against damages or defects arising out of
improper or abnormal use of handling of the Products; against defects or damages arising from improper
installation (where installation is by persons other than Manufacturer), against defects in products or
components not manufactured by Manufacturer, or against damages resulting from such non-Manufacturer
made products or components. Manufacturer passes on to Buyer the warranty it received (if any) from the
maker thereof of such non-Manufacturer made products or components. This warranty also does not apply
to Products upon which repairs have been effected or attempted by persons other than pursuant to written
authorization by Manufacturer.
3. Exclusive Obligation.
THIS WARRANTY IS EXCLUSIVE. The sole and exclusive obligation of Manufacturer shall be to repair or
replace the defective Products in the manner and for the period provided above. Manufacturer shall not
have any other obligation with respect to the Products or any part thereof, whether based on contract, tort,
strict liability or otherwise. Under no circumstances, whether based on this Limited Warranty or otherwise,
shall Manufacturer be liable for incidental, special, or consequential damages.
4. Other Statements.
Manufacturer's employees or representatives' ORAL OR OTHER WRITTEN STATEMENTS DO NOT
CONSTITUTE WARRANTIES, shall not be relied upon by Buyer, and are not a part of the contract for sale
or this limited warranty.
5. Entire Obligation.
This Limited Warranty states the entire obligation of Manufacturer with respect to the Products. If any part
of this Limited Warranty is determined to be void or illegal, the remainder shall remain in full force and
effect.

iv Limited Warranty AmpConnect 621™ Manual
page intentionally left blank

AmpConnect 621™ Manual Product Overview 1
Product Overview
AmpConnect 621™ simplifies your multichannel audio test in a single USB-connected unit. With sample
rates up to 192kHz, it is ideal for the measurement of high resolution audio devices.
6 inputs with independent control of microphone power for each channel
2 Line Outputs
Single amplifier output with switchable binding posts
Unique high accuracy impedance measurement independent of your input channels
Digital I/O
Plug-and-play setup with SoundCheck and TEDS support
Error-free operation with all control via SoundCheck - no buttons!
Clear visual level indications on front panel
Excellent ground loop immunity compared to discrete components
Rugged and rack-mountable for demanding production environments

2 Product Overview AmpConnect 621™ Manual
Front Panel Indicators
AmpConnect 621 must be connected to a computer running SoundCheck as all control and audio interface
functions are made via the USB 2.0 (minimum) connection.
When Inputs 1 through 6 are routed to the internal audio interface channels the front panel level indicators
show the signal state at those inputs. This gives you a visual indication to show if the input is overloaded or
underloaded (low signal level that is too close to the noise floor of the system).
See AmpConnect 621 Message Step on page 21. Also see Max FSD In in the SoundCheck manual.
Back Panel Connections
Saved State: The state of AmpConnect 621 is saved every 30 seconds. This allows the device to power on
in it's last used state. Note that this will be overwritten by Hardware Startup Defaults set in the System
Hardware.
AmpConnect 621™
Power
Input Levels Output Levels Amplifier
Output Enabled Level
1
2
3
4
5
6
1
2
A
B
Figure 1-1: Front Panel Level - Monitors the peak signal level and state of the amplifier output (All
values are nominal)
• Green indicates amplifier output level is >45 mVrms
• Yellow indicates amplifier output level is >13Vrms
Error Indicator - A blinking red Level LED indicates that the amplifier has
shut off due to an over-temperature or over-current event. The unit needs to
be power-cycled to clear the error state.
Input and Output Levels
• Indicator turns Green when level is > -50 dBFS
• Indicator turns Yellow when level is -6 dBFS
• Indicator turns Red when level is -1 dBFS
Output Enabled
• Shows the status of the back panel amp
binding posts
• Green indicates active
A+
A-
B+
B-
CAUTION: TO REDUCE THE RISK OF ELECTRICAL SHOCK, DO NOT REMOVE COVER. NO
USER-SERVICABLE PARTS INSIDE.
REFER SERVICING TO QUALIFIED SERVICE PERSONNEL .
Input 1
Input 2
Digital I/O
Input: 110-240V~
50 /60Hz 200W
Fuse: T2.5A
Bit 0 Bit 1 Bit 2 Bit 3 Bit 4 Bit 5 Bit 6 Bit 7
+3.3V
Ret.
Amplifier Output
Chassis GND
AmpConnect 621™
Listen, Inc. Made in U.S.A.
Serial No.
USB 2.0
Input 3
Input 4
Input 5
Input 6
Output 1
Output 2
CAUTION: RISK OF ELECTRICAL SHOCK – DO NOT OPEN
ATTENTION: RISQUE DE CHOC ÉLECTRIQUE –
NE PAS OUFRIR
Figure 1-2: Back Panel
Inputs
• Six Inputs,
Single Ended
BNC connectors
Outputs
• Two Outputs,
Single Ended
BNC connectors
Amplifier
• Mono power amp can be switched
to either Output A, Output B,
A and B or Toggle Outputs
Digital I/O
• send or receive signals with external devices
• See Digital I/O Operation on page 27

AmpConnect 621™ Manual Installation 3
Installation
Requirements
SoundCheck 18.1 (or later) is required in order to control AmpConnect 621™ via USB
The SoundCheck computer must have an available USB 2.0 connection
Note: It is recommended that AmpConnect 621 be mounted in a ventilated rack mount enclosure for
proper cooling.
USB Connections
AmpConnect 621 should be connected directly to the SoundCheck host computer USB Port. High quality,
powered USB 3 and USB-C hubs may work but should be tested for stability with AmpConnect 621. The
use of USB 2 hubs should be avoided.
Physical Installation
Power Requirements:
100-240 VAC, 50 or 60 Hz, 140W
Fuse: Requires 2: T2.0A, 250V 5x20 mm Time Lag glass fuses. Suggested replacement: Eaton/
Bussman BK/S506-2.0-R
Connecting AmpConnect 621 to the AC mains supply
AmpConnect 621 must be connected to a 50 or 60 Hz AC mains supply, with an operating voltage within
100 to 240 Vrms. The mains supply is connected to your AmpConnect 621 via the power entry module
located on the back panel. A 3-wire grounded power cord is supplied.
Ground the Instrument
Install SoundCheck first!
Before connecting AmpConnect 621 with the provided USB cable to the SoundCheck host computer,
SoundCheck must be installed. The AmpConnect 621 ASIO driver installation is part of the SoundCheck
software install process.
Windows will indicate that new hardware has been found, which shows that the driver has been
successfully installed. This may be displayed as “AmpConnect 621” or as “New HID Device”.
Caution! Airflow around the heat sink must remain unobstructed during use. DO NOT install
AmpConnect 621 inside an enclosure without a ventilation fan. When installed in a
rack, AmpConnect 621 units should not be installed on top of each other. Leave
airspace for cooling.
Warning! A grounding-type power plug is included with AmpConnect 621. The chassis and
cover must be connected to an electrical ground to minimize shock hazard. The
ground pin must be firmly connected to an electrical ground (safety ground) terminal
at the power outlet. Any interruption of the protective (grounding) conductor or
disconnection of the protective earth terminal will cause a potential shock hazard
that could result in personal injury.

4 Installation AmpConnect 621™ Manual
System Settings
The following settings are recommended to prevent Windows system sounds from inadvertently playing
through a device under test or artificial mouth. A transducer could be damaged by loud system sounds.
Windows Audio Devices
Note: For more information on computer system setup please refer to the main
SoundCheck instruction manual.
1. Click Start and type “Manage Audio Devices” in
the search bar and select Manage Audio Devices
3. Select the Recording tab and set the default record-
ing device to the motherboard sound card or any other
device that is not part of the measurement system
2. Click the Sounds tab and set the Sound Scheme to
No Sounds
4. Select the Playback tab and set the default
Windows playback device to the motherboard
audio interface or any other device that is not part
of the measurement system
5. Click OK and close the remaining Control Panel windows

AmpConnect 621™ Manual Test Connections and Procedures 5
Test Connections and Procedures
Microphone Array - Power Averaging
Figure 3-8 shows how AmpConnect 621 is setup for a 6 Microphone
Array.
Mic Bias - Set to SCM for all channels
Refer to the main SoundCheck manual for details on
Power Averaging in the Post Processing chapter
A+
A-
B+
B-
CAUTION: TO REDUCE THE RISK OF ELECTRICAL SHOCK, DO NOT REMOVE COVER. NO
USER-SERV ICAB LE PA RTS INS IDE.
REFE R SERVICING TO QUA LIFIED SE RVICE PE RSONNE L.
Input 1
Input 2
Digital I/O
Input : 110 -240V ~
50 /60 Hz 200 W
Fuse: T 2.5A
Bit 0 Bit 1 Bit 2 Bit 3 Bit 4 Bit 5 Bit 6 Bit 7
+ 3.3V
Re t.
Amplifier Output
Chassis GND
Am pC onn ect 62 1™
Listen, Inc. Made in U .S.A.
Serial No.
USB 2.0
In put 3
In put 4
In put 5
In put 6
Out put 1
Out put 2
CAUTION: RISK OF ELECTRICAL SHOCK – DO NOT OPEN
ATTENTION: RISQUE DE CHOC ÉLECTRIQUE –
NE PAS OUFRIR
Loudspeaker 1
(DUT)
SCM Ref Mic 6
SCM Ref Mic 5
SCM Ref Mic 4
SCM Ref Mic 3
SCM Ref Mic 2
SCM Ref Mic 1
To SoundCheck PC USB Connection
Figure 3-1: 6 Microphone Array
Figure 3-2: Mic Array
Message

6 Test Connections and Procedures AmpConnect 621™ Manual
Single Loudspeaker Test
Complete test using AmpConnect 621 uses the physical setup shown
in Figure 3-3 and the AmpConnect 621 Message Step shown
in Figure 3-4.
BNC Input 1 routed to Audio Interface Input 1
Gain: +20 dB
Mic Bias: SCM
Amplifier: Output A
This requires that the Analysis Step in the SoundCheck
sequence is configured to use the AmpConnect 621 -
Impedance Channel as shown in Figure 3-5.
See AmpConnect 621 Message Step on page 21.
A+
A-
B+
B-
CAUTION: TO REDUCE THE RISK OF ELECTRICAL SHOCK, DO NOT REMOVE COVER. NO
USER-SERVICABLE PARTS INSIDE.
REFER SERVICING TO QUALIFIED SERVICE PERSONNEL.
Input 1
Input 2
Digital I/O
Input: 110-240V~
50 /60Hz 200W
Fuse: T2.5A
Bit 0 Bit 1 Bit 2 Bit 3 Bit 4 Bit 5 Bit 6 Bit 7
+3.3V
Ret.
Amplifier Output
Chassis GND
AmpConnect 621™
Listen, Inc. Made in U.S.A.
Serial No.
USB 2.0
Input 3
Input 4
Input 5
Input 6
Output 1
Output 2
CAUTION: RISK OF ELECTRICAL SHOCK – DO NOT OPEN
ATTENTION: RISQUE DE CHOC ÉLECTRIQUE –
NE PAS OUFRIR
Loudspeaker
(DUT)
Reference Mic
Back Panel
To SoundCheck PC USB Connection Figure 3-3: Single Loudspeaker Test
Figure 3-4: Message Step
Figure 3-5: Impedance
Analysis Step

AmpConnect 621™ Manual Test Connections and Procedures 7
Two Loudspeaker Test
Figure 3-6 shows AmpConnect 621 setup to test two loudspeakers in
one sequence run using “Toggle Amplifier Outputs”. By using the
AmpConnect 621 Message Step in Figure 3-6, impedance
measurements can be made on both loudspeakers without having to
switch the wiring.
BNC Input 1 and 2 both set to:
Gain: +20dB
Mic Bias: SCM
BNC Input 1 Routed to Audio Interface Input 1
BNC Input 2 Routed to Audio Interface Input 2
Amplifier: Set to Toggle Amplifier Outputs, switching
between outputs A and B on each sequence run. (See Toggle
Amplifier Outputs on page 24)
Impedance Analysis Step: Set the same as Figure 3-5 on
page 6
A+
A-
B+
B-
CAUTION: TO REDUCE THE RISK OF ELECTRICAL SHOCK, DO NOT REMOVE COVER. NO
USER-SERVICABLE PARTS INSIDE.
REFER SERVICING TO QUALIFIED SERVICE PERSONNEL.
Input 1
Input 2
Digital I/O
Input: 110-240V~
50 /60Hz 200W
Fuse: T2.5A
Bit 0 Bit 1 Bit 2 Bit 3 Bit 4 Bit 5 Bit 6 Bit 7
+3.3V
Ret.
Amplifier Output
Chassis GND
AmpConnect 621™
Listen, Inc. Made in U.S.A.
Serial No.
USB 2.0
Input 3
Input 4
Input 5
Input 6
Output 1
Output 2
CAUTION: RISK OF ELECTRICAL SHOCK – DO NOT OPEN
ATTENTION: RISQUE DE CHOC ÉLECTRIQUE –
NE PAS OUFRIR
To SoundCheck PC USB Connection
Loudspeaker
(DUT) 1
Loudspeaker
(DUT) 2
Reference Mic 2
Reference Mic 1
Back Panel
Figure 3-6: Two Loudspeaker Test
Figure 3-7: Toggle Outputs

8 Test Connections and Procedures AmpConnect 621™ Manual
Microphone Test
The Microphone test setup in Figure 3-8 shows how AmpConnect 621
is setup to measure a DUT Mic vs. a Reference Mic as found in the Mic
Substitution sequence included with SoundCheck.
Reference Mic connected to BNC Input 1
Gain: 0 dB
Mic Bias: SCM
DUT Mic connected to BNC Input 2
Gain: 0 dB
Mic Bias: Should be set to the requirement of the DUT Mic
Amplifier: Output A
A+
A-
B+
B-
CAUTION: TO REDUCE THE RISK OF ELECTRICAL SHOCK, DO NOT REMOVE COVER. NO
USER-SERVICABLE PARTS INSIDE.
REFER SERVICING TO QUALIFIED SERVICE PERSONNEL.
Input 1
Input 2
Digital I/O
Input: 110-240V~
50 /60Hz 200W
Fuse: T2.5A
Bit 0 Bit 1 Bit 2 Bit 3 Bit 4 Bit 5 Bit 6 Bit 7
+3.3V
Ret.
Amplifier Output
Chassis GND
AmpConnect 621™
Listen, Inc. Made in U.S.A.
Serial No.
USB 2.0
Input 3
Input 4
Input 5
Input 6
Output 1
Output 2
CAUTION: RISK OF ELECTRICAL SHOCK – DO NOT OPEN
ATTENTION: RISQUE DE CHOC ÉLECTRIQUE –
NE PAS OUFRIR
Back Panel
To SoundCheck PC USB Connection
Reference
Loudspeaker
DUT Mic
Reference Mic
Figure 3-8: Microphone Test
Figure 3-9: Mic Substitution
Message

AmpConnect 621™ Manual Hardware and Calibration 9
Hardware and Calibration
SoundCheck Hardware Configuration
The Hardware Configuration in SoundCheck must be setup for use with AmpConnect 621 before
attempting a measurement. The Plug and Play feature in SoundCheck ensures that all the required
Hardware Editor channels and Calibration Editor signal paths are established when AmpConnect 621 is
connected to the computer.
Plug and Play
“Automatically create Signal Paths for Listen Devices”
recognizes Listen Hardware and loads the correct input
and output Vp values stored in the AmpConnect 621 audio
interface memory.
The Vp value defines the maximum peak voltage that
corresponds to 0 dBFS (Full Scale Deflection).
Settings are found in SoundCheck Preferences > Launch.
This is enabled by default.
See the main SoundCheck manual > SoundCheck Main
Screen > Preferences for more information on
“Automatically create Signal Paths for Listen Devices”.
Driver Selection
AmpConnect 621 should be set to use the preferred ASIO driver
as shown in Figure 4-2. AmpConnect 621 can also be used with
WASAPI drivers.
Swapping Devices
If you swap one AmpConnect 621 for a different AmpConnect 621
while SoundCheck is open:
Open the SoundCheck Hardware Editor
Click Refresh. The editor will update to show the serial
number of the new unit in the Device field as well as the
new Vp values. The Listen Hardware Tab will also
update and show that the new interface has replaced the
old one.
Figure 4-1: Hardware Editor
Figure 4-2: Refresh Hardware
Editor

10 Hardware and Calibration AmpConnect 621™ Manual
Hardware Editor
The sample rate for AmpConnect 621 is set to 44.1kHz by default. Click on the drop-down arrow in the
Default Sample Rate column and select from the available rates. This will update all input and output
sample rate fields for the device.
Latency - The Latency value for each sample rate is preset for AmpConnect 621. Generally these values
should not need to be adjusted. For default Latency values see the tables on page 12.
Latency is the round trip time delay between input and output channels on a single audio interface when
operating in full-duplex mode (record and play simultaneously). Consistent latency is essential for sample
accurate measurements such as Absolute Phase. Refer to the SoundCheck Manual > Hardware
Configuration > Latency Adjustment.
The following process should be followed if you find that latency is slightly
different than the default hardware step included with SoundCheck. This could
be due to differences in motherboard or driver version.
1. Open the Hardware Editor. Since Latency is Sample Rate dependent,
click on the Default Sample Rate drop down to select the desired rate.
2. Click on the drop down arrow next to the value in the Latency field of the
Hardware Editor. Select Edit and the Latency Table will open.
3. Set the Latency for the desired sample rate to 0 (zero) and click OK.
4. Make sure the sample rate of the audio interface has updated. Change the
ASIO Buffer/USB Streaming mode for the audio interface in the ASIO
Control Panel (if applicable). Typically there is no buffer control for WDM /
WASAPI.
5. Run the Self Test sequence from the Calibration folder in SoundCheck.
This will give you the Latency for the new Buffer size or Sample Rate.
(Some audio interfaces may require “fine tuning” of the Latency value by
following Step 5 and then repeating Step 4.)
6. Enter this value in the Latency field of the Hardware Editor Sample Rate/Latency Table. Repeat this
process for other required Sample Rates.
Figure 4-3: Hardware Editor - Audio Tab
Figure 4-4: Sampling
Rate
Figure 4-5: Edit
Latencies Table

AmpConnect 621™ Manual Hardware and Calibration 11
7. All channels, analog or digital, must have the same latency value per sample rate for that audio
interface. This ensures the system will work correctly if they are used simultaneously in a
sequence.
Latency Changes
Latency is the round trip time delay between input and output channels on a single audio interface when
operating in full-duplex mode (record and play simultaneously). Consistent latency is essential for sample
accurate measurements such as Absolute Phase. Refer to the SoundCheck Manual > Hardware
Configuration > Latency Adjustment.
The following process should be followed if you find that latency is slightly
different than the default hardware step included with SoundCheck. This
difference can be due to motherboard or driver changes.
1. Open the Hardware Editor. Since Latency is Sample Rate dependent,
click on the Default Sample Rate drop-down to select the desired rate.
2. Click on the drop-down arrow next to the value in the Latency field of the
Hardware Editor. Select Edit and the Latency Table will open.
3. Set the Latency for the desired sample rate to 0 (zero) and click OK
4. Make sure the sample rate of the audio interface has updated. Change the
ASIO Buffer/USB Streaming mode for the audio interface in the ASIO
Control Panel (if applicable). Typically there is no buffer control for WDM /
WASAPI.
5. Run the Self Test sequence from the Calibration folder in SoundCheck.
This will give you the Latency for the new Buffer size or Sample Rate.
(Some audio interfaces may require “fine tuning” of the Latency value by
following Step 5 and then repeating Step 4.)
6. Enter this value in the Latency field of the Hardware Editor Sample Rate/Latency Table. Repeat this
for other required Sample Rates.
7. All channels, analog or digital, must have the same latency value per sample rate for that audio
interface. This ensures the system will work correctly if they are used simultaneously in a
sequence.
Figure 4-6: Sampling
Rate
Figure 4-7: Edit
Latencies Table

12 Hardware and Calibration AmpConnect 621™ Manual
Default Latency
Windows Default Latency in Samples for Typical Sample Rate and Buffer Values
USB Connection 44.1 kHz 48 kHz 88.2k 96 kHz 176.4 kHz 192 kHz
ASIO/USB Buffer 512 / Safe 512 / Safe 1024 / Safe 1024 / Safe 2048 / Safe 2048 / Safe
Samples / ASIO 1364 1429 2641 2765 5250 5494
Samples / WASAPI 1382 1494 2675 2895 5754 5754
Enter the Samples value in the Hardware Editor Latency field for the selected Sample Rate.
Figure 4-8: Windows Latency in Samples
Important! After importing the stock HAR file (C:\SoundCheck xx\Steps\Hardware\Approved
Hardware\AmpConnect 621 WASAPI.Har), the Latency values for WASAPI must be
manually edited using the values from Figure 4-8 following the steps noted in
Latency Changes on page 11.
macOS Default Latency in Samples for Typical Sample Rate Values
USB Connection 44.1 kHz 48 kHz 88.2k 96 kHz 176.4 kHz 192 kHz
Samples 1202 1302 2320 2510 4612 4985
Enter the Samples value in the Hardware Editor Latency field for the selected Sample Rate.
Figure 4-9: macOS Latency in Samples

AmpConnect 621™ Manual Hardware and Calibration 13
AmpConnect 621 Hardware Configuration
The Vp values for the AmpConnect 621 are factory-programmed, and are automatically loaded into the
Hardware Editor when “Automatically create Signal Paths for Listen Devices” is turned on. See Plug
and Play on page 9.
The Calibration Editor is also updated with the correct signal paths for the associated hardware. See
SoundCheck Calibration Configuration on page 15.
If AmpConnect 621 is added to an existing SoundCheck configuration, the channels will automatically be
displayed in the hardware editor after the pre-existing channels.
Important! Do not use different input and output driver types for an audio interface,
e.g.: ASIO for inputs and WASAPI for outputs. Doing so will result in an
Acquisition Step error.
WDM Drivers
WDM drivers are available in the Hardware Editor for AmpConnect 621. WDM drivers only allow access to
Input Channels 1 and 2 of AmpConnect 621.
Note: WDM drivers do not allow for consistent Latency and require that you use Auto Delay or Auto
Delay+ in any Analysis Step. WDM drivers should not be used when making Absolute Phase
measurements.
Figure 4-10: Hardware Editor Vp Values

14 Hardware and Calibration AmpConnect 621™ Manual
Listen Hardware Tab
AmpConnect 621 is automatically recognized by SoundCheck according to serial number. Each device is
added to the Listen Hardware page and automatically named. If simply exchanging one AmpConnect 621
for another, the Device ID remains AC621-1 and the Serial # field updates.
Right-click on the Device ID to change the following:
Rename - Change the Device ID field to a
unique name. The example in Figure 4-11
shows the Device ID of AmpConnect 621 is
set to: AC621-1
Delete - Remove the selected item from the
list
Assign Startup Default - Set the initial
settings that the device will adopt when
connected to this SoundCheck system
Startup Default
The startup default editor, shown in Figure 4-12, initially contains settings commonly used for loudspeaker
testing, explained below. These can be modified to suit your test requirements.
Note: The Self Test sequence will return AmpConnect 621 to factory default settings. Restore your
Startup Default settings by clicking Apply in the editor show in Figure 4-12 or restart
SoundCheck. See Self Test Sequence on page 16.
Inputs
Source: All BNC inputs are routed to the their respective Audio
Interface channels, e.g.: BNC Input 1 routed to Audio Interface
Input 1
Gain: All channels set to Mic Bias set to Voltage with +20 dB of
gain
Mic Bias: All channels set to SCM for use with Listen’s SCM
reference microphones
Switching Mic Bias on or off with an AmpConnect 621
Message Step during a sequence run may require a Wait
Time of 2 seconds in the step to allow for settling time.
Amplifier: Always routed to Amplifier input of Audio Interface.
Gain is set to 0dB.
Impedance: Always routed to Impedance of Audio Interface. Gain
is set to 0dB.
Outputs
Output 1 and 2: The Audio Interface Outputs are routed to the BNC outs respectively. This allows
for the use of an external amplifier if more channels are required.
Amplifier: Power Amp Output routed to Binding Post Output A
Full details on settings and use of the Message Step are covered in AmpConnect 621 Message Step on
page 21.
Figure 4-11: AmpConnect 621 Setup
Figure 4-12: Startup
Default