Introduction

Getting started - getting in

Apparently, Willow Vale have not been contactable recently so I am indebted to Mike Mears for locating another source, namely Dutch West Distributions, tel - 01434 32 32 32. The manual appears to be slightly cheaper from them.

• Opening the case

  Remove the seven T10 screws which secure the lid to the rest of the casing and remove the lid. Remember to have a suitable container to keep all the screws and other small parts in so that you don't lose any.

• Removing the CD board

  • Disconnect the wire coming from the transport PCB to the chassis, the ribbon cables between the transport PCB and the power supply PCB.
  • Remove the two screws securing the whole transport assembly to the chassis and carefully remove it from the case.
  Make a note of their relative position as you will need to make sure that they are reassembled correctly.
  • Remove the single screw which secures the PCB to the transport mechanism and remove the PCB by unclipping it.

• Removing the AF board

  • Disconnect the cable from the transformer to the power supply PCB.
  • Remove the screws securing the digital and phono sockets of the AF board to the rear of the case and the one securing it to the base.
  • Disconnect the cables which connect the PCB to the control panel PCB and the headphone PCB. You can now remove the AF PCB from the case.

Modifying the power supply section.

1. Replace the four IN1003 diodes (6253-6256) with UF4002 types.

   This reduces the power supply noise floor.

2. Replace the 3300 microfarad capacitor (2258) with a 4700 microfarad. I replaced both the large caps with 4700 ufd/16v (Elna RJH) but to get them to fit under the transport PCB I had to fit them in a horizontal position.

   This balances the loading of the mains transformer windings and allows for slightly higher current dissipation.

3. Bypass both the 4700 microfarad capacitors (2254, 2258) with a 0.1 microfarad capacitor (polyester/polypropylene). I used polypropylenes and had to fit them under the PCB.

   This improves the filtering of HF noise from the mains supply.

4. Short out resistor 3260 with a wire link.

   This is only needed to protect against excessively high input voltage and is not needed in countries where there is a stable mains supply.

5. Connect a 1K resistor between pins 2 and three of the 7805 voltage regulator (7251).

   This provides correct current feedback biasing for the regulator and ensures that neither the zeneer diode nor the regulator over-dissipates under short circuit loads.

Modifying the DAC and audio out sections.

1. Replace the three 100 ohm resistors (3502, 3503 and 3504) with 22 ohm values.

   This reduces the jitter on the signal going to the DAC and also improves the wave shape.

Modifying the audio output section.

1. Remove the 1n ceramic capacitors (2529, 2530).

   These were originally introduced to reduce HF noise level but they do nothing and are best removed.

2. Replace the NJM4560D opamp (7505) with a Signetics type NE5532.

   This improves the sound performance over the much faster NJM which seems to get confused by the out-of-band noise.

3. Replace the 220 picofarad capacitors (2509, 2510) with 470 picofarad polystyrene versions.

   This improves mid-band to top details and also improves the -80db wave shape.

4. Replace the 47 microfarad output capacitors (2511,2512) with 10 microfarad low ESR or bipolar types and bypass these with 0.22 microfarad polyester/polypropylenes.

   This speeds up the bass end of the player while still allowing it to reproduce very low frequencies. Bypassing further increases the speed.

5. Add RLC notch filters on the output. These consist of a 470uh inductor (standard Philips type) and an 820 picofarad polystyrene capacitor. The position of the filters is shown by the green lines on the circuit diagram above. Please note that the caps 2513 and 2514 (470 pF) in parallel with the outputs are to be removed if you add 820 pF + 470 uH to form an RLC filter. Thanks to Massimo Pessina for pointing this out.

   This improves the rejection of out-of-band signals which cause a ringing effect in the upper frequency response.

6. If the headphone facility is not to be used, leave the cable to the AF board disconnected.

   This removes the extra loading of the connecting cable and improves audio performance.

7. Not really a modification but worth looking at. Check the value of resistors 3537 and 3538 (RC filter with caps 2521 and 2522 in the PS of the dual opamp). They should BOTH be 220 ohm. In many units, one of these resistors is 1.2k. Again, thanks to Massimo Pessina for this tip.

Modifying the CD transport PCB.

1. Remove capacitor 2890 by either snipping it out or de-soldering.
2. Remove the resistor 3896 and replace it with a wire link (or just short the terminals).
3. Remove resistor 3897 by either snipping it out or de-soldering.

These modifications clean up the waveform which is output by the transport.

• Change R3896 to 390R
• Change R3897 to 91R
• Remove C2890

Improving the digital output.

• Change C2541 to 0.47uF (probably not necessary)
• Remove transformer 5801 and fit links on the pcb between pins 3 & 4 and 1 & 6
• Replace R3556 with a link
• Remove C2543

What else?

1. The simple way to provide an inverted DC voltage to the negative voltage input of the opamp and grounding the positive signal terminal. This allows fine offset control but eventually drifts.

• 1) New Clock (Tricord?)
• 2) Analogue Stage with LM6182 and a DC offset circuit to allow direct coupled outputs. For this the feedback loop capacitor and the LC circuit were removed. The Lowpass was realised AFTER the LM6182 100 ohm Output Resistor with 22nF to ground.
• 3) 120VA torroidal Transformer plus Schottky Diodes, low Z Electrolytics supply regulated via LM317/337 supplying +/-15V for the Analogue Stage, good local decoupling for the Analogue Stage. A seperate 5V supply tapped off the +15V for the TDA1545 DAC.

UPDATE