I have a relatively new 451 and bought Nordic’s digital interconnect and we also set up with optical output. I hear no difference between the two . Is there an actual difference or are they producing the same sound.
The digital output specifications on my RS151 are Coaxial PCM 24bit/384kHz and Optical PCM 24bit/192kHz. So, theoretically the Coaxial cable is able to handle double the samples, and also the Optical requires signal converters from electrical to optical and back again.
That said; I used to connect an outboard DAC from my old CD player and having used both Optical and Coaxial digital interconnects I concur with you that I couldn’t hear a difference…they both sounded great.
I’ve always held that as long as the interconnects are well constructed and use quality parts you should be pleased with the results. In other words, if you are pleased with what you hear, congratulations and enjoy the music.
To make it short:
No, with bit-perfect transmission and the same sampling rate there is no sound difference between an optical (Toslink) and a coaxial (Coaxial) digital output/input.
Both are purely digital interfaces that transmit the same zeros and ones. The phenomenon of people hearing differences there is usually in the realm of psychoacoustics or stems from faulty peak matching.
Here is the technical reality without “snake oil” voodoo:
The technical data compared
|Feature|Optical output (Toslink / fiber optic)|Coaxial output (Cinch / SPDIF)|
|Signal type|Light pulse (LWL)|Electrical impulses (voltage)|
|Max. Sampling rate (standard)|96 kHz / 24-bit (some modern devices can reach up to 192 kHz)|192 kHz / 24-bit (sometimes even higher)|
|Guaranteed bandwidth|Lower (limited by the sending/receiving diodes)|Higher (problem-free for high Hi-Res rates)|
|Galvanic separation|Yes (no electrical connection)|No (copper cable)|
|Susceptibility to grinding slippage|Zero|Possible|
|Susceptibility to jitter|Minimum higher (due to power conversion from electricity → light → electricity)|Minimum lower [1]|
Why some believe to hear a difference
There are exactly two technical nuances that play a role in extreme borderline cases, but have nothing to do with “better sound”:
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Jitter (timing jitter): During optical transmission, the electrical signal must be converted back into a current in light and in the DAC. This process can theoretically generate minimal jitter. However, modern DACs have such extremely good internal clocks (timing signals) and buffers that they completely eliminate this jitter. It lies far below the human perception threshold.
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Ground hum (humming loop): When you connect your PC to the system via a coaxial cable, you connect the electrical grounds. This can cause a noticeable hum or whine (e.g., from the graphics card). This is optically advantageous because optical fibers do not conduct electricity and the devices insulate perfectly.
Conclusion for your practice
As long as you listen to music in normal CD quality (44.1 kHz / 16-bit) or usual high-res (96 kHz / 24-bit), the same signal arrives exactly to your DAC via both cables. A difference is not physically or biologically audible.
Only when you want to play extremely high-resolution files at 192 kHz should you go for the coaxial cable, because many optical Toslink connections (especially on older televisions or mainboards) will drop out at this data rate and cause dropouts. However, if it works and doesn’t drop out, it sounds identical.
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