• Registered: 2020-10-05
  • Posts: 287

Topic: SPDIF(coax) bass heavy vs bass light

Hi there smile a misc question.
This weeekend I've tested two cd players against the same dac. All sources 16 bit 44,1kHz and not upsampled.
Same cd burned twice to test. Not true blind AB test done since coax cable needed be switched
Regardless I seemed to have found one seems more pronounced in vocals and with lighter bass and another with stronger bass and more forward positioning.
I'd say 1's and 0's are all same. What could cause this diff or is it just my perception?

ADI2, Digiface, ARC
  • waedi
  • DAW Mastermind
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  • From: Swiss Zürich
  • Registered: 2020-12-08
  • Posts: 4,451

Re: SPDIF(coax) bass heavy vs bass light

With a cable loopback recording you can do a null-test.
Then you have a measuremet.
Without measure it is perception.
Technically it is impossible to have a difference when the signal is transferred.
You also should perform blind tests, another person changes the cables randomly and write it on a paper.

M1-Sequoia, Madiface Pro, Digiface USB, Babyface silver and blue
  • jusu
  • ADAT user
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  • Registered: 2023-02-11
  • Posts: 15

Re: SPDIF(coax) bass heavy vs bass light

waedi wrote:

Technically it is impossible to have a difference when the signal is transferred.

Well, according to some meassurements we did, this can be caused by a bad cable in deed when there is much reflection and noise from external sources disturbing the signal. S/PDIF always requires clock recovery and even if the PLL of the sink does not get out of clock it will though forward that introduced jitter into the system if not propperly cleared.

I see some (most consumer) Systems having a simple PLL and a short sample buffer mapping the phase noise into the lower audible range because there is a lousy design.

Well howevery this jitter is typically small and generally hardly audible.

Strong differences are mostly generated by hidden resampling or drop out compensation (digital artifacts indeed taking place and recovered by the device).

You should (let) scan the SPDIF with an Oscilloscope, exchange cables and the sink and / or use TOSLINK optical to get an impression which device is the problem.