Peripheral Board Mxh-40A; D/A And A/D Conversion; Analog Volume Control; Line Out Amplifier - Hammond XK-5 Service Manual

• External memory for DSP
– Work memory DDR3 RAM 2Gbit
– Program SPI NOR FlashROM 32Mbit
• Power supply for DSP, Terminal parts
• Device for various I/O
• USB A/B terminal, microSD socket & card, Board to board connector
Connect to MXH-40A with board to board connector J1 and J2.
Updated by inserting the USB flash drive into the USB A terminal which is connected to the
main processor and operate the screen.
The program for main processor is stored in microSD card. The wave data is stored in microSD
card JK4, and the program for DSP is stored in SPI (serial) flash ROM U20.
The power input is 5V and generate the various power source for the internal circuit. The power
source +3.3V and +1.8 of those also supply the power to MXH-40A.

2.2 Peripheral board MXH-40A

There are the various functions as follows.

2.2.1 D/A and A/D conversion

Convert the digital audio signal generated by MGH-106A to the analog signal.
Also convert the analog signal from the vacuum tube to the digital signal.
U3 CODEC performs it.

2.2.2 Analog volume control

Receive MASTER VOLUME and control the volume with the two of the 4ch analog volume
control IC (U26 and U27) via I
L/R, total 5 channels.
The input level is designed to be high in order to improve S/N ratio and start to distort gradually
from the master volume point around 3 o clock when the output of the digital audio data is
maximal.
2.2.3 LINE OUT amplifier
Used NJM4580M for U28 operational amplifier.
The maximum level without distortion is around 27V
To improve S/N ratio, it is adjusted to match the level when the analog volume control IC starts
to distort.
2
C. The channels are LINE L/R, ROTARY, STATIONARY
p−p
10-2
, 9.6V .
rms