Introducing the Symphony Receiver
The Symphony Network Audio Receiver, is a device for playing high-fidelity, low-latency, multi-room audio on existing passive speaker setups, stereo systems, or headphones.
Symphony is my current project, and will be the motivation of many future blog posts. Let’s dive in!
The overall design goal is to produce high-fidelity, “audiophile” quality audio, from any source regardless of device ecosystem, free of vendor lock-in, and empowering the user to listen how they like with no gimmicks. User freedom is important to me so the device API, protocol, and client apps will be fully open source and specified. Software will be discussed in a later post.
On to the specs!
The receiver will play up to 192kHz 32bit Stereo audio streams from any of the following sources:
- WiFi (802.11b/g/n/ac on 2.4GHz or 5.0GHz bands)
- Ethernet (RJ45)
- Bluetooth (4.2)
- SPDIF (Optical TOSLINK)
- USB (Type C connector)
As you can see, many of these sources aren’t actually network connections, so the full name is a bit of misnomer.
The following outputs are available on the receiver and are used exclusively from each other:
- Headphone (3.5mm Jack)
- Stereo Speakers (Spring Loaded Binding Posts)
- Line-Out (3.5mm Jack)
The Headphone amplifier is capable of a maximum of ~500mW/channel when high-gain is enabled. Power and loudness calculations will come in a future post.
The Speaker amplifier is capable of a maximum of 50W/channel (110W/channel peak), but the total power will be effectively limited to the power adapter’s maximum power rating.
The receiver’s front panel will focus on simplicity with the following controls and indicators:
- Volume Knob/Cycle Input (Turn for Volume, Push for input toggle)
- Headphone Jack (3.5mm)
- Input Selection LEDs (4x White)
- Volume Level LEDs (14x White)
- Power/Status LED (RGB)
The receiver will be fully configurable via a graphical web interface, and a REST API for developers.
There is no power switch, the device sleeps when not in use and wakes automatically when audio is played. All LEDs are automatically dimmed based on ambient lighting conditions, and off when sleeping.
The receiver must be powered through an external 24V AC adapter if the Stereo Speaker outputs are used. Otherwise, all other outputs may be used on USB power exclusively. Power supplies are hot-swappable with respect to the previous limitation.
The dimensions of the receiver are 135mm x 40mm x 137mm (Length x Width x Depth).
The specs above are a short summary of the capabilities of the Symphony receiver. However, the objective of this blog is to get technical and to explore things in-depth.
My vision is to discuss the requirements, design process, trade-offs, theoretical performance, and eventually, real-world performance of each part of the receiver’s hardware design. Upcoming articles will be focused on the audio sections. Those should turn up in the coming weeks. Not wanting to exclude the rest of the system, other interesting design aspects will be discussed briefly along the way.
My goal for the Symphony series of blog posts is for readers to come away learning something new from electronics, software, or product design. With that, hope you enjoy the ride!