Left and Right channel D to A stages
The Wolfson WM8740 stereo DAC requires +5V(A) and a +3V3 supply along with the Digital Audio data lines already described in this guide.
The Left channel output only will be described in this section as all audio output stages are the identical (all six channels of a DV79) apart from the HDCD gain switching for L + R only.
IC400B and associated components for a 2nd order Bessel filter with a differential input and a gain of 1 this follow by a output buffer IC401B, the gain of IC401B is control by the switching chip at location IC402, in normal use the Gain of IC401B is set to 1.1 but in HDCD mode the IC402 switches a second 10k resistor in parele with R413 and the gain is set to 2.2 allowing for the higher audio output required by the HDCD standard.
C436 is a A.C coupling capacitor used to remove the few mV of offset that the DAC produces, D400 provides protection against from ESD.
The all output relays are under control of the Vaddis V chip but will also mute the outputs instantly under mains failure conditions. Switching drive is provided by TR401 (MUTE_BUF) and TR400 (AC_PRES) the relays are in mute mode if either the input to TR401 is Low or if the input to TR400 is high.
Please note: The Scart left/right audio is fed from the outputs of the left/right audio stages.
Video Encoder
The video encoder at location IC703 is an Analogue devices ADV7310 video encoder, supporting interlaced and progressive scan video. Please note the 0.1% tolerance components around this stage. IC703 runs on a 2.5V supply provided by REG700 the voltage reference for the chip of 1.225V is provided by REF700 and should be seen on Pin 46.
The Data lines into the encoder arrive as VIDP0 – 19 from the outputs of the VADDIS V chip.
The external current setting resistors for the internal DACS are seen as
The encoder gives out 6 video signals, for composite,
The six analogue output signals are seen as.
oDAC_A = Composite o DAC_B = SVID Y
o DAC_C = SVID C
o DAC_D = Y or Green o DAC_E = U or Blue o DAC_F = V or Red
Please note: When the player is in Progressive scan mode the composite and
The Video outputs from IC703 are filtered by six identical filters. For instance if we look at the Composite stage we will see a very slow roll off filter comprising of C719, C721 with L701 and L703 the
The outputs are driven by the Video
These signals now travel to the COMMS and Video extension card on Con 901.
SCART Output
RGB and Composite video signals as well as left and right audio signals are all present on the SCART output socket. As the RGB and YUV signals share the same output port at the Vaddis V the player must be set to RGB SCART operation to have a RGB output on the SCART. Please note: When in RGB SCART mode the RGB does not contain a Sync signal and the sync must be taken from the Composite out (4 wire RGB).
Also present at the Scart are a number of control flags for the monitor these include 2 GPIO control lines direct from the Vaddis.
oENABLE_AV o 16/9
These are seen at the SCART output pins as.
oO/6/12
oRGB STAT
The 0/6/12 line (SCART pin 8) is used to inform the monitor of the screen format being sent by the player as set in the video
oStandby = 0V
o16:9 aspect ratio = 6V o 4:3 aspect ration = 12V
The RGB status line (SCART pin 16) will be seen as 0v = no RGB and >1v is RGB present.
