Archive for May, 2010

PCM1794A DAC – Hardwire version PCM1794

Tuesday, May 18th, 2010

This is the PCM1794A DAC I am working on with 24bit/192k digital input format.  Thus it is good for computer, media player or CD/DVD player as digital source.

The basic structure is CS8416, PCM1794A, Discrete transistor IV/buffer, super regulator for IV and 5V/3.3V regulator ICs for digital circuit.  This is a hard wired version and measurement is done with very good results.

1. Distortion: Around 0.02% at 1kHz, 30k BW, 1.45Vrms output level

2. Frequency Response: -0.07dB at 20kHz, 20Hz to 20kHz BW

The transistor IV is a common base with class A buffer and no feedback design.  The output is OCL (output capacitor less) and this ensure very smooth sound and good dynamics of music.

Measurement Results:

D-A FFT DAC 1794 set 2 lin lite

D-A FFT DAC 1794 set 2 FR and Dist lite

Yamaha D2040 Digital Crossover

Tuesday, May 11th, 2010

Yamaha D2040 is a 2 channel input and 8 (not 6) channel output digital crossover.  The input signal can be either digital AES or Analogy XLR.  Some audiophile use this unit as a digital crossover to drive bi amp, tri amp or quad amp with 4, 6 or 8 speaker systems.  This is a really flexible crossover for use.  The only thing I do not like it is that when I use AES digital input, there is no digital or analogy volume control as a master volume.


This outstanding crossover are still widely used by proaudio due to its good sound.  The DAC are all PCM63P-Y with quite standard op-amp design.  The sound is very good and clear and use many audio grade components inside.  Due to its good performance and flexibility, this unit is still very hard to find and cost $600 to $700 usd.  Oh! the price of this unit may be double soon!


Some internal pictures:

Yamaha DA8X 8 channels DAC

Monday, May 10th, 2010

This is Yamaha DA8X which has 8 pcs PCM63p-Y or KY inside.  Not much audio grade resistors in this model but it still have Elna Duorex and Nichicon Muse capacitors. The PCM63 chips are tuned to lowest distortion by two VRs next to the DAC.  No chance to hear how it sounds but the digital filter is NPC SM5803APT (lower grade than SM5842APT).

Price of this from ebay can be cheap as not much studio is using it due to 20bit resolution only.  So it is a good target to get the KY or Y chips inside!  Good luck!


See pictures: 

Yamaha DEQ5 & DEQ5E Digital Equalizer

Monday, May 10th, 2010

This is one of the remarkable 2 channel digital equalizer ever made by Yamaha using lots of audio grade parts – Elna audio cap, RMA resistors and Muse etc…  The digital receiver is YM3436C x 2, YSF210 digital filter and PCM63P-Y x 2.  IV is 5238 and LPF is NE5532.

Both DEQ5 and DEQ5E can be used as a standalone DA converter using AES digital input and thus it is a good reference DA converter but the maximum resolution is only 20 bit.  The sound is wonderful and full which can easily better than many today DAC.

Some internal pictures: