Russian K40Y-9 PIO Capacitor inside photo

September 5th, 2010

I open up a defective Russian PIO K40Y-9 PIO capacitor (6800pf 200V) and here is two photos:

Caution to use: Do not heat up the leads close to the metal body for too long or else the internal oil will leak out!

D1V33 from Olivier – France

August 25th, 2010

This is some picture and description of the D1V33 kit from Olivier – France to share with DIYers.

– concerning the 24 bits mod. Here find a link to a photo i did. Instead to cut the PCB, solder a wire, i removed the P10 pin and soldered a wire from P10 to the jumper “GND”. Easier for me…¬†

– i put a trigger in my casing. In this way, the DAC switch on automatically when my DIY preamp is on. I like it !

– i connected the GND of your DAC to the earth of the IEC through a 10R (in mine 18R because i was stock out….) 3W resistor. I don’t have any “humm” or any noise with this way

– an finally i put your name on my backplate. ūüėČ

PCM1794A DAC – Version 1, PCM1794

June 27th, 2010

The DAC is base on the circuit of the hardwire version with some additional features.

  1. Digital Input: I2S (via pin header), SPDIF РRCA, AES and Toslink (optical); selected by two pins 00/01/10/11 for all 4 inputs.  Default input is RCA РSPDIF without selector sub-pcb.
  2. Output: RCA Left and Right (about 1.5Vrms); mute by relay shorting output signal to ground
  3. Display: 3 LED –¬†Mute, 48k, 96k; Fs display is for 8416 only!
  4. For Analogy Balance output, two pcb are required and one pcb jumpers will be set to Mono L and the other set to Mono R channel.  I2S flat cable is reqired to connect the source pcb to the slave pcb.  To be tested!
  5. Power input: 18V x 2 0.5A and 9V x 1 0.5A AC

This is the first version and thus there are few minor errors on the pcb: Optical input reversed pin 1 and 3 connection, no mounting holes for optical receiver, no mounting holes for XLR female socket, and non-optimized ground path.  Thus some cut trace and jumper wires are reqired on the bottom of the pcb.  But anyway the FFT measurement is quite satisfactory after error corrections.   Here are the photos and FFT measurements.

1794 DAC V1 FFT

From the FFT, you can see the noise floor is about -135dBV (-138dbr).  It is about 5dB better than the hardwire version.

1794 DAC V1 FreqResponse & Distortion

Distortion and frequency is about same for both hardwire and Pcb version 1.

Update: June 30, 2010

One pcb is install in the casing and use a better transformer.  The FFT is ploted again and 50Hz hum is not seen anymore.

D-A FFT DAC 1794 V1 log (Case set1)

PCM1794A DAC – Hardwire version PCM1794

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

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: