Designing a USB DAC connecting PC and phone

Project Info

Case

The client requested a customized USB DAC that connects a PC to a phone. The design was to be later prototyped and applied for mass production. Its application was intended for the following products:

Application: Smart Cellular Phones, IC-Recorders, Bluetooth Headphones, CD/SACD Players, Network

Audios, USB DACs, USB Headphones, Sound Plates/Bars, HD Audio/Voice Conference Systems, AV Receivers

Challenges

Such DACs are available in the market. The main problem with the design was client’s request for using three special ICs to do the work and no other replacements. He had also These ICs were:

  1. AK4492 which is a 32-bit 2ch DAC with VELVET SOUNDTM technology. It has six types of 32-bitdigital filters, realizing simple and flexible sound tuning in a wide range of applications. The AK4492accepts up to 768 kHz PCM data and 11.2MHz DSD data.bitdigital filter
  2. AK4205: This is a stereo headphone amplifier corresponding to high resolution with a built-in analog switch for Hi-Fi mobile. One of the main features of this component is that it can save the mounting area of the board by adding resistors for gain adjustment and a low-pass filter.AK4205
  3. This cheep is a USB 2.0 high-speed audio processor that supports the latest USB Audio Device Class V2.0 and high-definition audio processing applications. Besides, it has an embedded 8051
  4. The other challenge was that the enclosure was already made by the client and therefore the shape of the PCB was to be made in a way that it could fit into the enclosure.
  5. The components had to be chosen for THM (Through Hole Mounting) and not SMT (Surface Mounting) in a way that the final board could fit the enclosure.

Solution

The main challenge in doing this work was making it with the give components. There were many options that were more cost-effective and easier to prototype and manufacture. Also, the given components were not generally available with many suppliers or online sellers. Therefore, the first stage, i.e., coming up with a memorandum of understanding with the client took a lot of time and finally a circuit design that was satisfying with the client was agreed on. In order to resolve all the requirements, we used some of the modules that were suggested by the supplier for the design including the following module that we used to connect AK4205 (stereo headphone amplifier) to AK4492 (2 channel DAC)

module

Also, after making the original design, and testing it, we made the design in a way that it could fit into the enclosure. This was also a challenging part of the project because using through-hole components would lead to oversizing the board that was not acceptable by the client. The reason was that:

THM requires the drilling holes that take more space

THM also limits the available routing area

Therefore, we agreed with the client to replace some of the connections with their SMT equivalents and managed to fit the board into the given enclosure.

Description

The final result complied the client’s requirements. It included all the components he needed and also its size was 40mm x 70 mm as requested by the client. After two months of work, it was finally submitted to him for the prototyping.

Client:
J. Brad
Date:
May 4, 2018
Location:
NY, USA
Category:
Electrical and Electronic Engineering