Scanning; Synthesis Asic; D-To-A Converter - Kurzweil sp5-8 Service Manual

Printed Circuit Boards
Function Overview
U3 is a NAND Flash chip, which is very similar to what is used in memory cards and USB
"thumb" drives. It holds the operating system code, sound programs and setups, and user
data (user sound programs and MIDI sequences). The capacity is 64MB.
U2 is system RAM. After bootup, the operating software executes from system RAM. It also
holds currently used sound programs and MIDI sequences.

Scanning

Software in the operating system also performs scanning of the player controls (keyboard and
pedals) and the user interface (UI) controls (buttons, LEDs, Spin knob, sliders, and wheels).
This is accomplished through a simple, Kurzweil standardized, interface called ScanPort (J7,
page 3, zone D1). Most of the circuits for scanning are actually on the Right and Left Front
Panel PCBs; only a couple of buffers (U6, U8), an analog amplifier (U9), and decoding logic
(U11) are on the Engine PCB. See the Right and Left Front Panel PCB descriptions for more
details about ScanPort operation.

Synthesis ASIC

Page 2 has the MARA synthesis ASIC, U5. This proprietary, Kurzweil designed VLSI chip
integrates the following synthesizer circuits:
• 64 sample playback channels, each with independent playback rate
• 64 amplitude envelope blocks
• 256 DSP processors, each with independent envelope
• Effects processor with 16 processing blocks
• Patching array for interconnecting the above resources
• Digital audio formatting circuits
The instrument sound samples are stored in Sound ROM (page 4, zone 5D). The standard
SP5-8 has 64MB (only U13 installed) of Sound ROM. Other products using the same Engine
PCB may have additional Sound ROM installed at U14.
The effects processor also uses an external Delay RAM (U12, page 3, zone A4). Pops, audible
crashing sounds, and other extraneous noises are often caused by defective Delay RAM or
connections to it.

D-to-A converter

U15 (page 4, zone D1) is a digital-to-analog converter. It connects directly to MARA on the
digital side and directly to the Audio Out header (J11) on the analog side. Amplifiers and
reconstruction low-pass filters are on the Left Front Panel PCB. Although U15 is an 8-channel
DAC, only the first two channels (L1 and R1) are used in the SP5-8.
A separate MUTE signal comes directly from the CPU to suppress pops and clicks during
power-up and power-down. MUTE must have a low logic level (less than 0.8V) to enable
audio on the Left Front Panel PCB.
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