So it's (at least!) time to talk about the....

Audio Analogue PAGANINI CDplayer

However, talking about the Paganini is quite the same that talking about the Maestro, the "higher price" CD player of the Audio Analogue: in fact about 90% of the work (the mechanics, the servo circuit, the DSP, the display, in other words the whole digital section; plus the case, the front panel, etc.) is exactly the same in the two CD players. The only relevant differences are in the DAC section (Crystal 24 bit and op-amp post filtering in the Paganini, Burr Brown 24 bit and discrete components in the Maestro) and in the (one more) transformer for the analog power supply.

These differences, In My Opinion, lead to a factory cost of about 20% higher for the Maestro.

Oh, well, there is another difference too: the Paganini has been designed by the two original designers and founders of the Audio Analogue: Mr. Santo Pratticò and me (Federico Paoletti)!



Well, let us now have a look at the Paganini CDP; this being a very complex project I ask you to relax before proceeding.


Are you ready? OK, let's GO.

The drive mechanism
First of all, you need a drive, and the world is divided in two guidelines: the Sony and the Philips.
Yes, I know there are other interesting brands like Teac and so on, but if you need to start a design buying a low quantity of pieces you have only the former choice.
The relevant fact is that with the Sony you have a complete chip-set that needs only to be wired, with the Philips you need some form of DSP to be programmed with some exotic language in order to obtain some stupid functions (e.g. press "open" and the tray does it).
So we made some tests, and we decided for Sony; we made only an aesthetic alteration: the plastic bridge that support the magnetic centering mechanism has been replaced by an aluminium one, with the Audio Analogue logo printed over it (someone says this is the reason the Paganini plays better).



The selected drive is a Sony KSL-2101ABM with the following items "on-board":

SLED motor

FOCUS coil

LASER diode
RF diode

DISC-IN / DISC-OUT switches
LIMIT switch



All these signals are brought out with four connectors, named as:

J201,  white colour,  8 wires  (RF diode, TRACKING diode)
J202,  red colour,     8 wires  (LASER diode, CURRENT LASER diode, TRACKING SERVO coil, FOCUS coil)
J203,  white colour,  6 wires  (SPINDLE motor, SLED motor, LIMIT switch)
J204,  white colour,  5 wires  (DISC-IN / DISC-OUT switches, LOADING motor)



We used the following Sony chip-set in the CD:

CXA1782Q (RF Signal Processing Servo Amplifier for CD players)
This takes care of the LASER power and positioning; driving the diode, the coils and some motors; it also recover the Radio Frequency signal to be processed by the DSP.
CXD2508Q (CD Digital Signal Processor)
It reads and demodulates the RF signal, recovering various signals from the EFM modulation stream; it buffers data into a FIFO memory creating the SPINDLE motor signal; it talks with the system controller; gives as output the signals for the DAC.
CXP1042Q (System Controller for Compact Disc Players)
It is the interface between the user and the rest of the circuits, via the keyboard and the display.
Ancillary chip is the Rohm BA6395FP, nothing but a power interface driving coils and motors.



Some of the signals needed for the mechanics are created by IC201 - CXA1782Q (Focus and Tracking coils, Sled and Spindle motors); others are generated by IC203 - CXD2508Q (the Forward and the Reverse controls, and some enable/disable data).

The diagram
Yes, you now MUST download the whole diagram of the Paganini CD player! As usual, it's a poscript zipped diagram; once you've "unzipped" it you need some form of poscript reader, e.g. GSVIEW32.exe. Or simply send it to a poscript printer.

The digital circuits

The Sony CXA1782Q is the chip that reads the quadrant photodiode (ABCD) and the tracking error photodiode (EF), and from these signals extracts the RF signal (that contains the audio data) and a lot of other signals that are used locally for reading the CD or used by the DSP (IC203).

<--Here the PDF (762k)
Some of the local signals are the Focus Error (FEO), the Tracking Error (TEO), the Center Voltage (it is half of the power supply), the Automatic Power Control (APO), the Sled Motor (SLO); other signals are present on a serial bus connected to the DSP (e.g. pins 19 to 25).
Some errors on the component's value are present in the Sony data-sheet (e.g. C226 has a real value of 2n2, not 22nF; as well as C224 that is 2n2 again and not 47pF).



The Rohm BA6395FP is a 5 channel driver and V/I converter specified for CD player motors and actuators; we didn't use the internal regulator (pin 5 and 6); the voltage at pin 19 fixes the disc loading/unloading speed (the higher the voltage, the faster the movement).

<--Here the PDF (187k)
The signals amplified from this chip are: SLED, SPINDLE and LOADING motors; TRACKING and FOCUS coils.



The Sony CXD2508Q is the DSP; the main task is to read the RF signal and to extract (Eight to Fourteen Modulation) some important data.

<--Here the PDF (604k)
These are:
There is also a digital filter and a D/A 1bit converter in this chip, but they aren't used.

Some of the above signals are used by the SPDIF interface chip (Crystal CS8402A), a biphase-mark encoder whose output signal is activated by SW201 on the rear panel.
<--Here the PDF (307k)
This chip is used in "Consumer" mode: data are LSB justified, 16 bit, 44.1 kHz; output characteristics are 0.5 Vpp / 75 Ohm via the isolation transformer T201



The end of the digital chain is the Sony CXP1042Q (click for the 561k PDF), a 4 bit single chip microcomputer that incorporates programs for CD operations. The job of this chip is to interface between the keyboard, the IR remote control, the display and the rest of the CD player.

Not all the possible functions are implemented in the Paganini, at least on the front panel operation; more freedom is left to the owner using the infrared remote control.
About this latter, the format is NEC and the code is AACD (Audio Analogue Compact Disc).
Over the little PCB that supports IC301, in the back of the front panel, there is the LCD display unit and the IR receiver (IC303).
Backlighting for the display is obtained with four SMD Hewlett-Packard LEDs.



The converter
DAC DATA from IC203 are also used for driving the CS4390 24bit Crystal D/A converter.
We consider this chip one of the "best sound" available on the market at the moment of designing this CD player (about 1998).
The ability of reaching 96kHz clock data is worth nothing if you don't have it! What is important is the true linearity and the dynamic range, in order to obtain a value as close as possible to the theoretical 16bit limit from the disc you're playing.
In this sense it's a good rule to use a 24bit DAC, even if you're dealing with 16bit stream.
So the Crystal CS4390 was one of the first chips to reach this limit, and it was suited over the maximum clock frequency used in domestic appliances: the 48kHz of the DAT recorder.

<--Here the PDF (978k)
Some interesting features of this chip are the 97dB THD+N, low clock jitter sensitivity, Delta/Sigma 1bit DAC, "in-chip" switched-capacitor low pass analog filter. This latter is a linear phase design, and a great care must be used to the design of the external filtering system: although a Bessel type should seems the best choice, extensive tests show that a "maximally-flat" Butterworth filter reduces the error at 20khz with negligible phase deviation in the audio band.
<--Here the PDF (73k)

Selecting the output operational amplifier is not a simple task; we tested a very nice operational amplifier like the Analog Devices AD797 (it is defined as "Ultralow distortion, ultralow noise"), and we found it very promising as "first of the class"; unfortunately it was marginally stable, so we turned to the ubiquitous Texas TLE2071CP, as used in the BELLINI preamplifier.
Anyway you'll notice the presence of C5/C105 (defined as "optional" on the diagram): it was foreseen for the use of the AD797.
There is a resistor in series with the signal (more on this later), needed for damping capacitive loads and for not short-circuiting the operational amplifier when the muting relay RL1/RL101 is activated.

The power supply
It remains to talk about the power supply: this is not esoteric, but employ some simple rules for avoiding cross-talk between digital and analog circuits.
In detail: the main power supply is filtered with FL401, then controlled by SW401 general switch, located in the rear; circuit signal ground (SGND) is connected to the earth (TP401) via the 10 Ohm resistor R401, avoiding ground loops with other electronics. This resistor has in parallel four capacitors (C454 to C457): these act as short circuit for high frequencies bringing the SGND to earth potential for non-audio signals.
Two toroidal TALEMA transformers supply current to circuits: T401 for the analog side (split supply mode) and T402 for the digital circuits (secondary windings are in parallel).
Conventional three terminals ICs are used, and while all the analog section is always "on" (at least when the back mains switch is on too!), the digital section is divided in two: IC404 supply power to VSTBY, and is always "on"; all the remaining supply ICs are powered only if the CD player is not in Stand-By condition.
The Stand-By is one of the "bullet" switches on the front panel: pressing it pulls down pin2 of IC409 (NE555 timer) and this toggle the out (pin 3) for a time RC (R406/C443); this in turn force a change of state at the output of IC410A (the LED goes off and the darlington Q403 starts conducting, powering the rest of the digital circuit). During the first power-up IC410A is forced with "Q" low by the pair R407/C444.

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