rossini cd player rev 2 · 2020. 11. 19. · rossini cd player rev 2.0 6 / 7 measurements as first...

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Rossini CD Player REV 2.0 1 / 7

Issue Date: June 2008

AUDIO FUTURA spa

Research & Development

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Rossini CD Player REV 2.0



Introduction

Even if the Rossini CD Player REV2.0 has the same look of the previous revision it is completely different inside. With the REV2.0 we have created a unit where the

vacuum tube technologies and the best digital technologies could be perfectly mixed together. The circuits we have used come from a long research expecially for the

original vacuum tube output stage that is the strong point of this CD Player. The results we have had have been ever higher then the target we would reach. In particular the listening sessions shows that the Rossini CD Player REV2.0 has a

“different “ and “original” sound compared to other CD Players. The Rossini CD Player REV2.0 is a starting point because it demonstrates that the

vacuum tube and newest technologies union has to be developed. We must run new streets, try new circuital solutions, go over the old configurations without falling in the mistake of a “too much microelectronic” approach.



Unit description

1. Digital Input

2. Digital Analog Conversion Section

3. Output Stage

4. Anodic Power supply

333

444

111

222



1. Digital Input

The S/PDIF signal is taken from the Cd Mechanism. We have used a CD ROM

mechanism specifically developed for the audio

application (We even contributed to the design for the firmware test part

and for the mechanical stability tests). In fact the

maximum speed has been reduced compared to the

standard CD ROM mechanisms, and the reading procedure has

been made more “Jitterless” and sturdy. To avoid any interference from ground returns we have

isolated the S/PDIF CD mechanism output from the main board by a transformer. The SPDIF signal is then send to the DA conversion PCB.

2. Digital Analog Conversion Section

The circuits performing the digital to analog

conversion are placed on a board physically

separated from the main board. That’s to avoid any interference on the analog

signals due to the return currents of the digital

parts of the DAC and transceiver. On the board there are:

the transceiver, the DAC and all their frameworks

including their power supply voltage regulators and capacitors. The

voltage for the “DAC board” is obtained by a

dedicated secondary of the transformer and a dedicated voltage regulator. The regulated voltage is then filtered by a RC filter. Then that voltage is used to produce the voltages for the transceiver and DAC by two voltage regulators. The components

on the “DAC board “ are predominantly SMD reducing the length of traces carrying high frequency signals to avoid irradiation effects. From the “conversion board” the

voltage DAC output is sent to the main board.



3. Output Stage

The output stage is an original circuit designed by the Audio Analogue

R&D office to emphisize the sound propertyes of

the vacuum tube and to take vantage of the solid state technology. It is an

inedited DC coupled low feedback three stage

structure where the vacuum tube is the first

one. The amount of feedback has been choosen not only on the

base of measurements but on the base of listening tests too. What we have tried to do is a balance of the

vacuum tube “coloring” and DAC “cleanliness”. The output stage’s gain is such that we have 1.9Vrms output for a 0dBV track.

4. Anodic Power supply

The output stage used is not based on a differential

input so the noise on the anodic supply is not

reduced by the circuit. That’s why we have worked on the anodic

power supply to make it as clean as possible. The

voltage for the anodic power supply is obtained by a high voltage

dedicated secondary and then regulated with a

discrete components voltage regulator. The regulator output is then filtered by a RC filter with a very low time constant (less then

1.24).

All the components used are high quality and low tolerance. The Board that is often a

neglected “componet” has been designed in respect of all noise reduction techniques expecially for the current return parts and power supply traces.



Measurements

As first I want to point out that the frequency axis scale in the following graphics is logharitmic. In such way is possible to see the low frequency noise due to the power

supply. Often the related measurements have a linear frequency axis scale. In such way the low frequency part of the spectrum is not visible. Perhaps this is expressly

done to not show low frequency noise. Anyway the 50Hz noise component due to the AC Power supply and the 100Hz component due to the effect of the rectification of the AC power supply are the cause of the loudspeaker “hum”. That’s why they must be

reduced in every audio devices.

Note: All the measurements performed with a Audio Precision System Two Cascade.

Misura dello spettro con apparecchio in stop.



Misura dello spettro per 1Khz 0dbv

Misura dello spettro per 1 KHz -10dbv.

rossini cd player rev 2 · 2020. 11. 19. · rossini cd player rev 2.0 6 / 7 measurements as first...

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