4
1. Basic informations
1.1 Mechanical construction
The case is fully made of aluminium. The audio-connectors are all gold plated to minimize electrical losses
and provide long lasting perfect contacts.
1.2 Power supply
Drive and digitalaudio circuitry (CD8, CD8T) have each a power supply of their own: Two toroidal
transformers together with nearly 30.000µF of capacitance supply the power. All voltages are well regulated
to avoid hum and are additionally buffered by large capacitors directly in the circuitry where they are needed.
1.3 The drive
The disc is read by a drive especially made for CD. It can theoretically read CDs at 2 times the normal
speed. Thus the positioning of the laser pickup and the focus regulation can act very quick. So the drive
never comes to it’s limits when reading audio CDs at normal speed. Besides normal audio compact discs the
drive can also read CDROMs and some CDRWs.
The drive is mounted in a capsule made of aluminum plates. This ensures optimal mechanical isolation of
the drive and reduces dramatically the influence of external vibrations.
1.4 Tube output stage CD8T
The CD8T is equipped with a tube output stage. We use one double triode for each channel. The triodes are
operated fully balanced. They operate with grounded gates and are fed via the Cathodes. This circuit design
ensures very quick reaction without sound degrading feed back. The tubes are heated with about 2 Watts of
power. This ensures a very long life and constant characteristic over the whole lifetime.
Thanks to the wide operating range and the balanced operation mode the CD8T has a very good dynamic
performance and offers -in respect to the excellent CD8 - even a further step ahead in musical quality.
The tube output of the CD8T has it's own power supply. It uses a 25 VA toroidal transfomer and a
combination of capacitors and chokes for smoothing the DC voltage. The high voltage for the tubes is
generated by an additional power supply which is fed by a precisely regulated DC voltage. A 300 Hz sine
generator followed by a power stage and a toroidal transformer generate the regulated high voltage. This
power supply operates fully independent of the unstable mains voltage and thus the tubes can always
operate at a stable bias point.
1.5 Digital- / analogue conversion (CD8, CD8T)
The CD8 / CD8T are equipped with upsampling circuitry and highly precise a/d converters. The theory of
function will be described in the following text. If You are not interested in technical details, skip these
chapters and simply listen to the music. You will discover Your CD collection anew! And that is what we want
to achieve. Because application of new technologies is not just a gimmick but offers audible and measurable
advantages to the listener.
1.5.1 Quantization noise
The quantity of information on a CD is defined by the audio format of 44,1 kHz sampling rate and 16 bits of resolution.
Additional informations (i.e. higher resolution or bandwith) cannot be created by any electronic circuitry playing back such
a CD. It is a fact that conventional d-/a converter systems do not fully reproduce the given information. This has several
reasons: Converting a digital signal to an analogue signal produces analogue noise. This is because the digital
(quantized) values which represent the signal are discrete with a very fine – but nevertheless limited - resolution.
Therefore exist slight deviations in respect to the analogue original signal which was continuous (means infinite
resolution). These deviations are random and cause an additional noise to the original signal when it is converted from
the digital domain to the analogue domain. This kind of noise is called quantization noise.
