Owner`s manual

2 of 12
Inputs
I
2
S (5-pin mini-DIN)
Balanced (AES/EBU)
Unbalanced (Coax (S/PDIF)
USB
12V DC
I find it a bit unusual that it is missing an optical input (Toslink), but there is only so much room on the panel. There needs to be a BNC too, at
some point.
Outputs
I
2
S (5-pin mini-DIN)
Balanced (AES/EBU)
Unbalanced (Coax (S/PDIF))
Under the Covers
The 1A consists of three main subsystems (see photo at right), an Anchor USB micro controller, the Analog Devices 21065L SHARC DSP
engine, and the Crystal CS8420 sample rate conversion (SRC) chip.
The Anchor is responsible for controlling the operation of the 1A. This includes front panel
buttons, displaying LED status, and interacting with the SHARC and SRC chips. The
SHARC performs all of the resolution enhancement, word-length adjustment (re-dithering),
and speaker/room correction. The SRC, as its name implies, converts from one sampling
rate to another.
The 1A can transcode from one format to another. For example, you can use the I
2
S
input and output S/PDIF, or vise versa. All internal processing is actually done in the I
2
S
format. If you use the I
2
S input (meaning an I
2
S connection from the transport to the 1A),
then you cannot upsample the signal. The reason is that the SRC can only handle up to
96 kHz. If you want to pass a 192 kHz signal through the 1A you must bypass the SRC.
When you bypass the SRC, you still get all of the other 1A features.
All of the software or algorithms are stored in flash memory (EEPROM). The flash is
updated by using the USB port and your PC. You will be able to download new software
from the Perpetual Technologies website, including speaker and room correction and then transfer the software to the 1A with your PC. This is
the first hi-fi product that I am aware of that offers a USB port.
The 1A also has some very serious power supplies! The 1A comes with a wall-wart adapter, but you can add an optional beefier outboard
supply. The 1A board also has a ground plane, which is necessary to keep the noise low. Some of you EEs might be saying, "Ground plane,
don't they all have one?" Duh! Well, let me tell you that not everyone uses a ground plane. The power supplies on the 1A are so good, that if
you plugged it into mud (providing mud could deliver AC), it would be able to completely filter out the garbage!
What exactly does a sample rate converter do? By increasing the sampling rate (upsampling), it helps out the DACs reconstruction filters later
on. If you select 96 kHz as the output sample rate, then all incoming sources, typically a 44.1 kHz signal, are converted to 96 kHz. Upsampling
from a 48 kHz source to 96 kHz is a direct integer upsample, i.e., it creates new samples in-between the original samples. This will be the case
with PCM data on DVD, DAT, and DSS. For CDs, which are 44.1 kHz, it is performing non-integer-based upsampling. What that means is that
it is no longer a direct integer of the original sample rate. This requires that the interpolation algorithms create all new samples.
Non-integer-based upsampling requires a lot of DSP horsepower to do it correctly.
I wish that the P-1A and P-3A offered the ability to perform direct integer sample rate conversion on all incoming sources (output 2x the sample
rate). You would get 96 kHz from 48 kHz and 88.2 kHz from 44.1 kHz. With that said, I did prefer the sound of the 96 kHz to the original 44.1
kHz. (Note from JJ: I spoke with Mark Schifter a few weeks ago about this, and they plan to offer integer upsampling software if you want
88.2 kHz instead of 96 kHz.)
User Interface
The UI of the 1A is very Audio Alchemy, and programming of the 1A is a four-step process. You first select the input, and then the program,
sample rate, and finally the output word-length. I am not really sure you could actually program it if you did not see the manual. You could get it
to work alright, but you would not know what it was doing. It takes a little fiddling, but once you understand the buttons, it is fine.
During and after programming, you have to pay attention to the LEDs that are active and their color. You also have to press both buttons at the
same time for part of the programming.
Scenarios
There are various applications for the 1A. One of the most common uses is to insert it between your CD/DVD player and your DAC. This is a