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FAQs
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Which
audio formats can be archived and replayed
1) Can I archive MP3 or other compressed
music files ?
The Ti48 was designed to archive only CD quality data (16 bits /
44.1kHz) and then to replay this with upsampling in order to extract
the most out of the CD audio format.
2) Can I record from the internet ?
Not directly into the Ti48, which does not have a modem built-in.
3) Can I record from other digital sources ?
Not at this time but we are working on a software upgrade that will allow the Ti48 to record into the hard-disks using
the digital ( S/PDIF) input.
4) Can I archive from analogue sources e.g.
LP or tuner?
The software upgrade mentioned in (3) will also allow the recording of an analogue signal into the Ti48 using a suitable analogue-to-digital
converter .
5) Can I playback SACD or DVD-A ? What about
DAD 24/96 discs from the audiophile labels such as Chesky or Classic
Records?
The Ti48 in its initial version will only play back and archive Red
Book CD audio. In future, an upgrade to DAD and/or DVD-A capability
may be possible depending on demand, due to the use of a DVD-ROM
transport. The Ti48 cannot be upgraded to play SACDs due to the
hardware configuration mandated by the SACD license.
How do I operate the Ti48 archiving transport and Ar38 DAC
6) Do I need a monitor or TV plus keyboard to
use the Ti48 ?
The Ti48 was designed as an audio-only source. Therefore it is operated using just the supplied remote control and the built-in screen as the user
interfaces. A separate computer monitor or TV are not required.
7) Can I plug in a monitor and keyboard to
manage my music files ?
Not at the moment though it may be a possibility should enough
customers request it. The remote control and built-in screen allow a
great deal of hard-disk file management.
8) How do I enter the album and artist names
of the CDs that I archive ?
With most mainstream and audiophile music releases, the CDs will be recognised by the
Ti48's database and the artist and album names and track titles will be
automatically saved when a CD is archived. When a CD is not
recognised, text entry can be made in the same way as with a mobile
phone, using the alphanumeric keys on the remote control.
9) How does the Ti48 recognise CDs ?
Pre-loaded into the hard-disk drives is a compressed version of the FreeDB
database called EmDB. This database, which is constantly being expanded, currently contains the album titles, artists
names and track titles of over 500,000 CDs submitted and catalogued by
the members of the public . You can read about FreeDB here : www.freedb.net
10) How can the CD recognition database be
updated ?
A CD-ROM will be available on a quarterly basis from Zero One Audio that
will contain the latest updated FreeDB database in a compressed
format. This CD-ROM will be self-booting, so the Ti48 will be able to
update itself using the disc. In the near future, this website will
have a page that will allow the download of the compressed database
from Zero One Audio's server into your computer. From your
computer, you can then burn your own CD-ROM and load the database into
the Ti48.
11) Can I use my own DAC with the Ti48 ?
Yes. The Ti48 also has an S/PDIF digital output. The data sampling rate
will be limited to 24 bits/96kHz via S/PDIF as this is the limit of the S/PDIF standard (whereas the Zero One Audio I2S data
transfer allows a sampling rate of up to 24 bits/192kHz to be sent to
the Ar38).
In order to further improve the performance of a DAC connected by S/PDIF,
the Ti48 has 3 user-selectable dither options (see 19 below).
12) Can I use my own transport with the Ar38
?
Yes. The Ar38 has a digital (S/PDIF) input. The Ar38 can accept
digital audio data from any compliant source up to 24 bits/96kHz. It
will upsample all acceptable digital audio data to 24 bits/96kHz using
its own sampling rate converter.
13) Can I plug another digital source into
the Ar38 ?
Yes. See (12) above. This means you can also feed the (stereo only)
digital output from a DAB radio or DVD player to the Ar38. The Ti48 can be plugged
into the Ar38 using the I2S link at the same time. A switch on the
back panel of the Ar38 selects either I2S or S/PDIF input
14) Can I increase the hard-disk capacity of
the Ti48 myself ?
The hard-disks are encoded and therefore, they cannot be replaced by
off-the-shelf hard-disk drives. We are currently looking into lossless
compression software which would increase the storage capacity by up
to 30%. If and when this software is available, it will be made
available as an upgrade on self-booting CD-ROMs or as a download from
this website. Please check back here for more news.
What
does the Ti48 digital audio processing software do
15) What is upsampling ?
Upsampling and oversampling are forms of sample rate conversion (SRC),
where one sampling rate (like the 44.1kHz of CD) is converted to
another. With oversampling, the source rate is stretched out to an
integer multiple (eg. 4 times to 176.4kHz) by mathematical
interpolation. The term upsampling tends to be used when conversion of
the audio data is to a non-integer multiple of the source rate (eg.
96kHz). SRC produces more output than input bits, so
devices such as the Ti48 increase the bit depth of the data to improve
the accuracy of the processing and output.
Neither upsampling nor oversampling adds data that did not already
exist on the CD being played back. The benefits of the process mainly
result from pushing the digital images that arise as part of all
digital sampling processes further away from the audio band. With a
sampling frequency of 44.1kHz, digital images of the data would appear
directly after the valid audio data (at 22.05kHz). A very steep filter
(commonly referred to as a "brick wall") would be required to remove
the ultrasonic mirror images perfectly, but the ringing that such
filters introduce may affect the sound quality.
By upsampling to for example, 176.4kHz, the digital images of the data
would be pushed out beyond 88.2kHz allowing the use of a digital
filter with a gentler slope to reduce the ringing and phase changes.
Another possible benefit of having less steep digital filters is that
these filters allow some ultrasonic noise to reach the D-to-A
conversion chips. The ultrasonic noise may be acting as dither which
would help to optimise the performance of the chips.
The Ti48 has a choice of three digital filters ( "upsampling modes")
powered by a 2GHz processor. Our custom software computes the
audio data with 64-bit double-precision floating point arithmetic for
high level accuracy. . Because the Ti48 is not based around a fixed
piece of silicon, the digital filters can be upgraded at a later date
to offer higher performance as the technology advances.
16) When setting the Ti48, which upsampling
frequency should I use
There is no one setting that will suit all preferences, hence the
selection available. When paired with the Ar38 via I2S, we would
recommend setting the upsampling frequency to 176.4kHz. When
paired with a DAC using S/PDIF, it is worthwhile trying a higher
sampling frequency, up to a maximum of 96kHz, if your DAC is capable
of accepting higher sampling rates. In our tests, we found that
88.2kHz improved the performance of some DACs compared to using
standard 44.1kHz.
17) When setting the Ti48, which upsampling
mode should I use
The upsampling modes refer to the various user-selectable digital
filters available in the Ti48 menu. Digital filters are a standard
part of modern digital audio design but the way they are implemented
can have a significant effect on the quality of audio reproduction.
The four modes : Purist, HQ1, HQ2, HQ3 indicate increasingly more
complex, steeper digital filters.
In general, the Purist mode offers better low level ambience,
transparency and musicality whilst at the other extreme, HQ3 mode
might be more suited to rock music. The actual effect will depend a
great deal on the rest of your playback system. We recommend that you
run-in the Ti48 using HQ2 and then experiment with the other settings
using a number of different styles of music.
18) Which wordlength should I use
The dither wordlength should ideally be set to the maximum wordlength
which the DAC can receive and use. In the case of the Ar38, it can be
left at 24-bit. If you use a standard 16-bit DAC, the wordlength
should be set to 16-bit.
19) Which dither type should I use
Dither is the addition of digital noise to the audio signal in order
to improve the linearity and low level resolution of the system. For
the technically inclined, the three dither options available in the
Ti48 are :
TPDF - traditional triangular distribution dither
Nyquist - high frequency noise at the end of the spectrum
NShape - second order noise shaping tilted toward the high frequencies
The different dither types can be used to tailor the sound and to
improve the performance of a DAC when using the S/PDIF connection.
We would recommend running in the Ti48 without any dither set and then
experimenting with the different dither types till you find a
preferred one. |
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