2
Thank you for purchasing the Grace Design Model 801R preamplifier system. The 801R
represents the absolute state of the art in microphone preamplifier technology. With the
combination of unmatched sonic performance, remote control capability, and supreme
reliability the 801R is the ultimate microphone preamplifier solution. We have designed
the 801R to be as easy to use as possible. If after reading this manual you have any
questions please do not hesitate to contact Grace Design. We welcome any questions,
comments, or suggestions that you might have.
Overview
The 801R system consists of an 8 channel preamplifier chassis, a power supply
chassis and an optional remote control unit (referred to as the RCU in the rest of this
manual). The preamplifier chassis contains 8 audio amplifier PCBs, a micro controller
PCB and a front panel LCD display. The preamplifier chassis is equipped with two
Philips I
2
C Bus connectors (D-sub 9 pin) and MIDI IN and OUT connectors. The RCU
contains identical micro controller and display PCBs and has a single Philips I
2
C Bus
connector.
The preamplifier can be controlled by the RCU, via MIDI, or directly from its front panel.
The RCU connects to the preamplifier via I
2
C which provides a bi-directional data link.
I
2
C is a serial buss which makes parallel connections between all of the devices in the
system. In an 801R system, the RCU is the “Master” and all of the preamplifiers are
slaves. The data on the display of the RCU is “echoed” back from the preamplifier so it
shows the actual status of the preamplifier. For instance, when you tell a preamplifier to
change its gain the RCU will send the gain change command to the preamplifier and
then ask the preamplifier what its current gain setting is. The RCU will then update its
own display to reflect the change. This gives the user absolute confidence that what is
visible on the display is exactly what is happening at the preamplifier. If the RCU is
disconnected from the preamplifier(s) the data fields in the display will go blank.
Only one RCU can be connected to a system at any time.
Please Note: The 9pin
I
2
C
is a proprietary interface. It is not compatible with RS-
232, RS-422, or any other 9 pin based serial protocol found in the recording studio
environment.
The RCU can control up to 8 preamplifiers (64 channels) by connecting it to one
preamplifier and then connecting the remaining preamplifiers together with I
2
C cables in
a daisy chain fashion. The RCU can be located up to 1000” (305 meters) away from the
preamplifiers. Using the adapters included with the RCU, standard microphone cable
can be used for this interface.
