Aphex 1788A Premium Eight Chan Mic Pre - Manual (Page 13)

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MICROPHONE PREAMPLIFIER
Page 13
Instruction Manual
3. INSTALLATION
3.9 COM PORT
This is a standard RS-232 Com Port that runs at a fixed 9600 Baud. It is provided to allow
downloading of new firmware into the 1788A. It has no other purpose. Read ahead
for instructions on this procedure.
3.10 INSTALLING NEW FIRMWARE INTO THE 1788A
Aphex is always striving to improve the performance of its equipment. The firmware that
was programmed into your unit was the latest available at the time it was shipped. There
may be updates to the firmware that were made from time to time. Please check the
Aphex website at www.aphex.com to see if there are any updates made to the firmware
from the time you had purchased or last updated the unit.
Determine your current firmware version by going into Local Control, depressing both Test
Tone buttons and Channel 8 at the same time. The firmware version will appear in the
Global Readout Display. If a new version is available, you may install it on your 1788A as
follows.
NOTE: Do not attempt to download any firmware designed for the 1788A onto older
Model 1788 units.
DOWNLOAD PROCEDURE:
1. Download to your computer the update program from the Aphex web site or other
media that you may have received.
2. Connect a NULL MODEM cable from your computer’s Com Port to the 1788A’s Com
Port.
3. Power up the 1788A while holding down both Test Tone buttons. “Load-A” will appear
in the Global Readout Display.
4. Run the update program on your computer and follow the on-screen instructions.
5. At the end of a successful 1788A download, the computer screen will show the
message: “End of Load”.
6. Cycle the 1788A’s power normally off and on. Verify the new firmware version as
described above. The new version should now appear in the Global Readout Display.
3.11 AUX OUTPUT POST/PRE MODE SETTING
Two Aux Output modes are provided: PRE and POST mic gain control. This mode feature
was created after many requests from users. As the default, the 1788A is normally shipped
in the POST mode. This would normally be considered the “normal” mode except that
many users will find advantages to the PRE mode as will be explained below.
HERE’S THE DIFFERENCE
The POST mode sources the Aux Output signal from the preamplifier’s variable gain stage
just as the Main Output does. Thus, the Aux Output will vary as a function of the preamp
gain setting. This makes the Aux Output pretty much equivalent to the Main Output
except for its own output gain variability. The PRE mode sources the Aux Output from the
preamp’s 20dB first stage, before gain control is applied. This way, the Aux Output does
not respond to variations of the preamp gain adjustment. This is well illustrated in the
figure below.