Service manual

DSP SIGNAL FLOW

The DSP board is the central hub of the signal flow system, the digital signals must find their way to the

DSP board, get DSP’d and make their way out again to the big audio ocean.

Please take a look at the Block diagrams chapter, especially the diagram on page D3, and the DSP

map on the next page. Also see the connectors chapter for details of every connector and pinout.

Signal names (golden rule)

Throughout the console, you will see digital signal names beginning with DR and DT. Anything which

starts with DR is a digital signal on its way to the DSP board, any signal which starts with DT has come from

the DSP board. Do not be surprised to see a few of the signals change name or number as they go from

one board to the next, (but the DT or DR start part will not change).

Analog input signals

Analog audio signals coming from the Line inputs or Mic inputs are converted to digital by the CODEC

board. Each pair of analog signals is combined to form one digital serial stream (DR) sent to the DSP. There

are a total of 12 digital signals (from 12 analog pairs)

Analog audio signals from the Tape cards are converted to digital by the Tape card’s own D/A

converters, and also paired to form digital data (DR) sent to the DSP board. Each Tape card has 8 audio

inputs and this yeilds 4 digital signals per card, or a total of 12 digital signals from the three tape cards.

Digital input signals

Digital input signals coming in from the standard Digital I/O card and the PDI•8 digital I/O card are

passed to the DSP board (DR). The incoming signals are already in the 2 channel digital serial form. The

standard Digital I/O card has 1 digital input, the PDI•8 card has 4.

Digital input and output signals from the effects cards

There are slots for up to four effects cards. Each card can send and receive two digital signals to and

from the DSP board.

DR (data received by DSP)

Digital data received by the DSP board for processing is labelled starting with DR. Each of the 24 DSP

ICs can receive two digital data streams, so you will see DR0_ and DR1_, followed by which DSP IC is used,

such as U1 , U3 or U24.

DT (data transmitted by DSP)

Digital data which is transmitted by the DSP board is labeled starting with DT. Each of the 24 DSP ICs

can transmit two outputs DT0_ and DT1_.

12 digital signals go to the CODEC board to become these analog signals: 8 Buses, Mix L, Mix R, Solo L,

Solo R and 12 Auxes.

12 digital signals go to the 3 Tape Cards (which have their own A/D convertors) to become 24 analog

tape outputs.

8 digital signals go to the 4 Effects cards, 1 goes to the Digital I/O and 4 to the PDI•8 I/O card. The

signals to the I/O cards are not converted to analog, but pass out of the digital output connectors on the

rear panel of each card for digital recording. Note that each signal is still really a pair such as L/R.