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Digital Audio Converter (DAC)
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DAC Model 3
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Last revision on july 2004
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Clic here to enlarge the picture
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- 24 bit resolution
- Switchable digital filter (Non oversampling to 8 x oversampling)
- Zero feedback line stage
- Bipolar solid states (MPSA18)
- Parallel regulated power supply
- Hight toroidal power transformer (300VA)
- Small capacitors power supply
- Analog deemphasis (for non oversampling mode)
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Design by Thierry Caritoux & Eric Juaneda
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Switchable digital filter
The DAC Model 3 include two switchable digital filter.
- A first conventional digital filter (DF1704 or DF1706) with 8 x oversampling. (4x ou 8x with DF1706)
- A second one with few logical function and 8 bit shift register alowing non oversampling digital filter.
Bit meter
The bit meter gives indications about signal quantization (16, 20, 24 bits data audio). It is not a level meter.
Why 24 bit data audio ?
Because real quantization of standard CD audio (CDDA) is more than 16 bit.
see Real quantisation of CD audio.
Using any other multibit DAC
If you goal is to design a non oversampling DAC, you can adpat schematic diagram to use any other DAC by changing serial shift register.
[PCM63, PCM1702, AD1862, PCM56, AD1856, AD766]
As outputs the CS8421/8414 generates 32 SCK periods per audio sample (64 per stereo sample).
For format 0 or 1, CS8412/14 outputs 24 bit data audio, MSB first, left justified.
Any DAC wait for XX bit data MSB first right justified.
For 24 bit DAC, inserting 8 bit shift register align data audio (32 - 24 = 8). For a 20 bit DAC, you need
to use 12 bit shift register...
Data bit |
| Shift register |
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| 24 |
| 8 |
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| 20 |
| 12 |
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| 18 |
| 14 |
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| 16 |
| 16 |
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shift register size to use other DAC
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