24 bit 192kHz DAC with AK4396
A DAC, or digital to analog converter, converts digital signals into analog signals. DACs are built into CD and DVD players, and other audio devices. The DAC has one of the most important jobs for sound quality: it creates an analog signal from the digital pulses stored on a disc or other digital media, and its accuracy determines the sound quality of the music we hear. The most common use of an external DAC is to upgrade the DACs in an existing CD or DVD player without replacing it, extending its useful life. Other uses for an external DAC include upgrading the sound of the music stored on a PC. In short, it's an effective way to upgrade the sound quality of many audio sources without replacing them.
The reason to consider having an external DAC is simply that it may be better than the DAC circuitry inside your existing unit. It is a relatively easy way of gaining more performance but without the expense of a full upgrade. So how can a DAC make such a difference?
- It has its power supply, so the power is not shared with
any other parts of the circuit hence is usually cleaner and has less
grunt behind it. The power is completely separated for analog and
digital parts, and both are well filtered with very low noise regulator
circuits.
- Other features of DAC’s can include re-clocking, where the digital signal is re-clocked and this can also add another level of improvement. What this means exactly is that the digital signal has its timing controlled inside the DAC itself. The other way is to generate a clock signal from the digital input itself and use that to drive the circuitry. Which is best can also depend on how good the clock in your transport is.
- The crucial analog output stage is where most of the extra
quality goes and this has a direct effect on the sound. In the case of an
external DAC, the analog output stage are made from better components,
and a well designed
On this page, I would like to present a very simple DAC.
Background: I start to design my own DAC based on PCM1794+DIR9001+SRC4192, but in meantime, I bought a DAC based on PCM1796 circuit (Carat Ruby II made by Style Audio, a South Korean audiophile company). Another option was to design with the famous AD1865, but is almost unavailable. One member from audiodiyers.hu forum recommended a DAC kit from ebay, called DAC2496, highlighting its clear and warm sound and indicating the eBay page, where can be bought.
Later I found endless forum-discussions about this design, the most
important one can be found on www.diyaudio.com.
The picture of pre-soldered PCB:
On the net also you can find the schematic, but below you can see my final, modified one:
List of my modifications/changes made compared to original PCB:
- all 7XXX regulators (U4, U9, and U10) were changed into LM3X7 type, adding 2-2 resistors + 1-1 capacitor for the same voltage setting. Reason: have less noise,
- with all electrolytic in the power section in parallel were mounted one 22nF/50V NPO/C0G capacitor - those are not presented on schematic!
- the output operational amplifiers were changed from NE5532 into OPA4562 ones,
- main filter capacitors (C23,C24, and C25) were changed from 2200uF/25V with 3300uF/35V Rubycon type,
- analog part capacitors C38 and C39, 220uF/25V were changed to 1500uF/25V Panasonic,
- C3, C28, and C29 (all were 10uF) were replaced with Sanyo OSCON 150uF, 100uF, and 68uF capacitors,
- C14 and C17 received 2 extra capacitors in parallel (operational amplifier power part, near to IC): 2x100uF/25V Elna SilmicII, C101, and C102,
- were made an input selector circuit with SW101, R107, and U101 as TORX176 optical receiver, FB101 and C101. This receiver are powered from +5vA, well filtered,
- all extra components received notations from 100, ex. R1xx or C1xx.
Final assembled PCB with old (NE5532 TI) operational amplifier:
Later I changed the OPA with OPA4562, and the sound became more lovely, dynamic, and very detailed.
The front of the finished digital-analog converter, with optical and SPDIF input selector (was made for AK4393 - but the front panel was not corrected for 192kHz).
Final assembled PCB with old (NE5532 TI) operational amplifier:
The DAC received a small USB to SPDIF module based on CM6631A (24/32 bit 192/384 kHz - but I use just the 24 bit 192 kHz part because of CS8416), is USB2.0 compatible, means does not require any driver for Win 10 (I use the 64-bit version), and are powered from PCs or laptops USB source. Are connected to DACs SPDIF via 100nF capacitor directly, no any source selector switch inserted. The module can be purchased on ebay or AliExpress for 24-26$ under "CM6631A USB to Coaxial Optical fiber SPDIF I2S Converter" name.
The USB to SPDIF module can be seen below:
The module on the picture has already extra soldered capacitors on it: 2 pcs of dry electrilytic (OSCON), and 3 pcs of Ta type.