Copyright © 2006-2011 AudioNote Kits
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Page 55
Section 7: Installing the Digital PCB
Digital Board Overview
The Digital Board is supplied with the kit built and tested. The board was originally designed for use in the DAC1.1 Kit,
which had the analog filter and IV circuitry. This circuitry is removed now and you will notice tantalum resistors located in
R34 and R35. These resistors are at the output of the DAC chip. In order to use the IV transformers we also need the
820pf capacitors in parallel with these resistors and you can see them installed in locations R44 & R43.
The Board was originally designed to support 75 ohm RCA input (CON1) and XLR 110 ohm (CON2). We are finding that
now with the USB option there is a third choice. So what the board allows you to do is use any two of the three and you
can switch between them. Most customers would either use RCA or XLR but not both so what we do then is use the USB
on the other channel. The switch at S1 allows you to select which input. Currently this switch needs to be set on the
board. The switch can also be hardwired in one way if you are always only going to be using just one input source.
On the Digital Signature Board we include the AN Toroidal input transformer and we custom install this on the channel
that you require (RCA or XLR)
Typical scenarios today are people using RCA 75 ohm and also USB
– So we are using the CON2 as the USB channel
and you will notice that we have wired two of the three inputs together
– the wired two are the GND for the SPDIF input
(same as the RCA input signal and GND) - So you will want to connect the signal from the USB to the hole that is the
large OVAL (not soldered) and the GND to either of the two remaining holes that are connected together
You will notice that when using the USB input on the “former” XLR input we have changed the value of R36 to 75 ohm –
(it would be 110 ohm for XLR operation)
If you ever want to change this back to XLR operation you can install the 110-ohm resistor back in this position.
IMPORTANT NOTE:
It is important that all five of the spacers and
screws are used to secure the digital board in
place.
One of these screws (see picture opposite) is
used to earth the digital board directly to the
chassis. If this 'connection' is not made
securely, a great deal of hum and RF
interference can result.
