How To Optimize Digital Streaming With Optical Fiber

A Better Way To Stream

Digital-to-analog converters,
Music servers and computer audio,
Digital cables
How To Optimize Digital Streaming With Optical Fiber

All Is Not Well In Paradise
All was well and good until about mid-2018, when my system started having frequent problems with dropouts and streaming interruptions. I finally traced the problem to a recently installed Wi-Fi-connected video doorbell. When the doorbell’s motion sensor was triggered, it would usually result in drop-outs and interruptions in my digital stereo system. The situation became so bad that occasionally I couldn’t get a single song to play all the way through without disruption.

At this point, I decided that it would be worthwhile to consider running a direct physical LAN connection from the Mac Mini in the study to the network bridge in the audio rack. This should result in better connectivity, I thought, as I had read in a support bulletin from Sonore that a direct Ethernet connection from the server to the network bridge would result in better overall performance, as well as higher audio quality than Wi-Fi. Around this time, I also become aware of a new product from Sonore called the OpticalRendu, which used “optical Ethernet.” Further research showed “optical Ethernet” is an optical fiber often used for very long runs (in the 100m to 1km range) of Ethernet connectivity, as it has significantly less insertion loss than copper Ethernet. 

Advantages of Optical Fiber
Putting my scientist hat on, I went into full research mode and started reading everything I could find about digital streaming using copper Ethernent versus optical fiber. Here’s what I learned.

Consumer-grade computers contribute significant high-bandwidth RF and impulse noise from their CPUs and GPUs that audibly impacts and degrades the sound quality of a stereo system. Additionally, this high-bandwidth noise can be picked up by many speaker cables (most of which are unshielded for sound engineering reasons), which literally function as antennas for high-bandwidth noise components that are then fed backwards into the power amplifier, to be amplified as noise. Moreover, any smart devices in the home (mobile phones, Wi-Fi routers, tablets, non-audio computers, video doorbells, thermostats) also contribute to the high-bandwidth RF and impulse noise in listening rooms. Consequently, one of the most significant things you can do to improve your digital audio system is to move any computer-based music servers (laptops, Mac Minis, Intel NUCs, etc.) out of the audio rack and well away from the main system, as these devices are very dirty with respect to the noise they create. The inverse-square law pays big dividends here. 

The “el cheapo” clocks in consumer-grade cable modems, network routers, Ethernet switches, and fiber media converters also contribute notable clock phase noise to the analog square wave voltages that actually comprise the digital bitstream, and the more of these devices in the configuration, the more the original signal is degraded. 

The dreaded switch-mode power supply (aka SMPS)—the ubiquitous device that powers almost everything from a computer’s internal power supply to streamers, network bridges, routers, NAS’s, external hard drives, switches, fiber media converters, etc.—are very dirty and nasty sources of noise, as they create both low-impedance and high-impedance AC leakage currents, which travel down DC power busses and lines, and ultimately into our DACs. High-impedance leakage currents arising from SMPS are particularly insidious, as they cause increased jitter and clock phase noise.  

Copper Ethernet cables are also susceptible to a number of noise factors, including RF, EMI, and the low- and high-impedance leakage currents described above; in addition, they suffer from a lack of galvanic isolation and common-mode noise rejection. In particular, shielded Cat 7 and Cat 8 Ethernet cables that are connected at both ends actually serve as conductors for high-impedance leakage currents. 

A good mitigation strategy for these problems is to use a run of optical fiber between the music server and the network bridge, streamer, or DAC. Optical fiber has a number of advantages over copper Ethernet: It is inexpensive, thin, flexible, and very easy to route. Most importantly, because the digital signals are transmitted as light, optical fiber is immune to RF and EMI and will not pass high-impedance leakage currents from computers, NAS’s, and routers to network bridges, streamers, and DACs. This results in a significant reduction in noise across the entire chain of streamer components, and notably cleaner, quieter, more transparent, and more natural-sounding digital music reproduction. 

The nice thing is that it’s easy and straightforward to set up an optical-fiber-based network connection. All you need are two fiber media convertors (FMCs), optical transceivers (if not provided with the FMCs), and a length of OM-1 specification optical fiber to run between them.