EC-2 96kHz A/D/D/A upgrade • appendix A
A-6 EC-2 Manual

Connect the PCBs

13. Connect the daughterboard to the Input and
Output PCBs: Line up the connectors to the
bottom (D/A) and top (A/D) PCBs, make sure
all the pins line up, then gently push the
daughterboard to the rear of the HD24 using the
plastic ribbon cable headers as pressure points,
making a connection between all three PCBs.
The connectors will only line up in one orientation.
Verify that there are no pins unconnected or exposed.
14. Put the remainder of the washers and nuts on
the jacks of the input and output connectors and
tighten them all down (total 48 jacks).
15. Install the new DC power cable, connecting the
power supply, main PCB, daughterboard, and
hard drive PCBs as shown in the illustration on
the previous page. Run it from the
daughterboard to the main PCB to the power
supply, then back from the power supply to the
two drives. Make sure the connectors snap into
place securely.
16. Replace the top panel.

To test for proper installation

After installation, you will be able to select
ANALOG input as well as DIGITAL with SAMPLE
RATE set to 88.1 and 96kHz.
1. Plug the unit back in to AC power and turn on
the HD24.
2. Select or create an 88.2kHz or 96kHz song.
3. Press INPUT SELECT until the “INPUT” group in
the alphanumeric display indicates
“ANALOG”. This confirms that the HD24 has
detected the EC-2’s presence.
If it’s not detected, unplug the unit and check all
connections carefully, disconnecting and connecting
each, then trying again to see if the EC-2 is detected.
Contact Alesis Product Support or an authorized
service center if the cards are still not detected.
Using the EC-2
For important information about high-resolution
operation of the HD24, see Chapter 7 of your
ADAT HD24 owner’s manual (page 65).

About 96kHz/88.2kHz Sampling

Operation

An ADAT HD24 with EC-2 upgrade boards
installed operates identically to a “stock” HD24
with respect to input arming, selection, and routing
(or “normalling”). The only difference is that you
will be able to use analog inputs and outputs when
the system is set to 88.2kHz or 96kHz sampling
rates. (Without the EC-2, you must use the ADAT
Optical digital inputs and outputs with an external
88.2/96kHz converter to record at higher sample
rates.)
• About 12-channel operation at high
sample rates
When recording and playing back any Song that has
been initialized at the 88.2 or 96 kHz sampling rates,
the HD24 is limited to recording a maximum of 12
channels.
• Analog input channels 13-24 will be ignored.
•Analog output channels 13-24 will duplicate
output channels 1-12.
•Digital inputs and outputs are grouped in fours
instead of eights: tracks 1-4 on the HD24’s ADAT
OPTICAL 1-8 ports, tracks 5-8 on the HD24’s
ADAT OPTICAL 9-16 ports, and tracks 9-12 on the
HD24’s ADAT OPTICAL 17-24 ports. For more on
operation of the ADAT Optical port, see page 66
of the HD24 manual.
When using an HD24/EC-2 at the standard 44.1kHz
or 48kHz sampling rates, you will still be able to
record and play back all 24 tracks. The only
difference from the original boards will be
improved audio performance, due to the higher
quality converters and analog circuitry of the EC-2.