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Why are digital streaming equipment manufacturers refusing to answer me?

I have performed double blind tests with the most highly regarded brands of streamers and some hifi switches. None have made any difference to my system on files saved locally. I have asked the following question to the makers of such systems and almost all have responded with marketing nonsense. 
My system uses fiber optic cables. These go all the way to the dac (MSB). Thus no emi or rfi is arriving at the dac. On top of this, MSB allows me to check if I receive bit perfection files or not. I do. 
So I claim that: if your dac receives a bit perfect signal and it is connected via fiber optic, anything prior to the conversion to fiber optic (streamers, switches, their power supplies, cables etc) make absolutely no difference. Your signal can’t be improved by any of these expensive pieces of equipment. 
If anyone can help explain why this is incorrect I would greatly appreciate it. Dac makers mostly agree, makers of streamers have told me scientific things such as “our other customers can hear the difference” (after extensive double blind testing has resulted to no difference being perceived) and my favorite “bit perfect doesn’t exist, when you hear our equipment tou forget about electronics and love the music”!
mihalis

Showing 2 responses by welcher

welcher's avatar
welcher
106 posts
 
I can provide some clarification on what you are hearing. My experience comes from developing communications and signal processing software. Including developing custom Ethernet drivers for signal processing.

The following discussion is for the analog transmission of a digital signal (PCM/DSD). Specifically Ethernet cables and switches. Note it does not apply to the analog transmission of analog signals (ie interconnects and speaker cables.)

An Ethernet frame is transmitted as a series of pulses. The transmitting Ethernet transceiver will generate a pulse for each bit in the frame. The receiving Ethernet transceiver will transform each pulse into a 1 or zero bit. The bits will be accumulated into a frame and the checksum validated. If there was an error in generating the correct bit value from a pulse then the Ethernet transceiver will request a frame transmission. If there are no errors the the frame, its contents will be copied into some form of buffer data structure. Processing on those buffers will be initiated by an interrupt or polling algorithm. At this point in time you have an exact replica of the original transmitted signal.
The well tempered computer dot com web site has a graphic depicting a pulse signal. It does not depict the aberrations in rise time introduced by clocks/crystals. If any of the pulse problems (overshoot, ringing, droop or undershoot) caused by EFI/EMI or clocking errors result in a bit error then the frame will be re-transmitted.

So you are correct that well designed Ethernet cables and switches do not effect the quality of the sound. If the receiving device (DAC/streamer) allow electrical noise from the Ethernet cable to affect the sound then you have a poorly designed DAC/Streamer.
Also one should not confuse Toslink with Ethernet fiber optic cables they are completely different animals. Note that an electrical signal on an Ethernet cable will travel about 1/100th the speed of an optical signal on a fiber optic cable. Fiber optic cables are used primarily for speed and system security. They will not make a difference in the sound quality.
welcher's avatar
welcher
106 posts
 
HI yyzsantabarbara

Both Qobuz and Tidal use the Rest API for streaming. The following is a generic example of a streaming session using Qobuz/Tidal; Audirvana and a streamer/DAC using UPnP/DLNA.
Audirvana will issue a REST request over HTTP to the Qobuz/Tidal server. Your computer will create an TCP/IP connection to the Qobuz/Tidal server and transfer the request after the connection is established. Your computer will also use Ethernet to transfer the HTTP, TCP and IP protocol data units to your router for transmission over the internet. The Qobuz/Tidal server will respond to the REST/HTTP request over the TCP/IP connection. Once the response is complete the TCP/IP connection will be closed.
TCP/IP will provide error free sequenced packet delivery between Audirvana and the Qobuz/Tidal server. If any packets are lost it will automatically re-transmit them. Ethernet will provide error free frame delivery between your computer and a switch/router.
Audirvana uses the UPnP protocol suite to transfer the media content received from Qobuz/Tidal server to your streamer/DAC. It will use HTTP, TCP/IP, UDP,  Ethernet and other protocols.

You will get error free delivery from Qobuz/Tidal to your streamer. There can be reduced band width on your connection due to network congestion/errors.
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