D-A; S6 D-A - Alesis QS Series Service Manual

2.40 D-A

The D-A sections of the QS Series vary slightly from unit to unit. These variations are
minor so the circuits are relatively similar, especially on the digital side of the IC. Most of the
analog differences depend on the D-A Device used. Both devices are made by AKM and come
from the same "family" (43XX Series). The main differences between the two are in the power
supply filtering required by these two devices. There are also internal differences resulting in
slightly better noise characteristics for the 4319.
As Aux Outputs are functionally identical the unit's main outputs, only the mains will be
discussed here.

2.41 S6 D-A

The S6 Digital-to-Analog Converter is an AKM4318A (U3). A bit clock (BICK) of 3.072
MHz, buffered by an inverter (U18B), is sent from the FX ASIC (U11). This clock signal is sent
to pin 13 of the DAC which is used to latch the serial data on SDATA (pin 14) into the device.
The LRCK (pin 12) input is the left and right channel clock. This 48KHz clock signal is
originated from the FX ASIC at pin 11. SMUTE mutes the analog outputs and is controlled by
the H8 processor (pin 53).
The analog supply (+5V) is filtered by C28 and C29. The digital supply is provided via
D4 and D5 (for approximately a 1.4V drop) from the +5V supply and filtered by C22 and C21.
The DAC outputs are balanced and are routed through differential amplifiers to the unit's
output jacks, via the analog output circuitry (See Section 2.20).
Alesis QS Series Keyboards Service Manual V1.00
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11/19/06