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Review and (unofficial) measurements of Thomann SSSnake Cat Snake 3FB and 3MC (Analog cable snake over Category 5/6/7 cable)

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Rja4000

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I found the use of the very specific J-test signal a bit irritating and misleading, that's all.

I thought that was exactly what it was initially meant for:
Why put the 250 Hz square wave in there if we never see it in the output of the real DAC?
When J-test was invented, it was designed to find jitter induced when long runs of AES or S/PDIF cables were used.
The toggling would cause all the bits to shift from one value to another, exaggerating sources of jitter there.
 
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Rja4000

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Low level SINAD test
Those tests are performed with Low Level signal (5mV rms)

NB: To optimize Low level signal, I follow the methodology I described in this post.

Path is as follows:
1. RME ADI-2 Pro fs R (19dBu range, both channels)
2. Radial Engineering SAT-2 Passive attenuator
3. Radial Engineering JDI Duplex - Passive Transformer DI
4. Y XLR cable, summing the 2 channels
5. "Cable" (or direct XLR)
6. Millennia HV-3C Mic Preamp (Max gain)
7. E1DA Cosmos ADC (6,7V mono)
Measurements are performed with Virtins Multi-Instrument 3.9.5

Measured level just before "cable" is 5,004mV rms
Measured level after mic preamp is around 5,13V rms (Preamp gain measured at 60,2dB)

"Direct"
5mV_Direct.png


Through "cable"
5mV_Cat.png


Comment

This measurement, being very low level, is more subject to random external factors,
so 0.4dB SINAD difference is probably to be considered within testing error.
 
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Rja4000

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Another attempt to
Low level SINAD test
Those tests are performed with Low Level signal (5mV rms)
NB: To optimize Low level signal, I follow the methodology I described in this post.

In this second attempt, I pushed further the preamp gain, by chaining the 2 channels of the mic preamp,
and using the RME as an ADC, allowing up to 24dBu input range


Path is as follows:
1. RME ADI-2 Pro fs R (19dBu range, both channels)
2. Radial Engineering SAT-2 Passive attenuator
3. Radial Engineering JDI Duplex - Passive Transformer DI
4. Y XLR cable, summing the 2 channels
5. "Cable" (or direct XLR)
6. Millennia HV-3C Mic Preamp (Max gain -3dB on one channel, Min=9dB gain on second channel)
7. RME ADI-2 Pro fs R (24dBu range, both channels averaged)
Measurements are performed with Virtins Multi-Instrument 3.9.5

Measured level just before "cable" is 5,004mV rms
Measured level after mic preamp is around 10V rms

"Direct"
5mV_2_Direct.png


Through "cable"
5mV_2_Cat.png


Comments

Here, we see more clearly a difference.
4dB is becoming significant.
It's mainly linked to some mains harmonics though.

Don't forget we compare 2 paths, the later with adding 30m of cable, on a 5mV rms signal.

Noise floor measurements in initial post are probably more relevant than this exercise.

NB: "Measured Level" at 5.1280Vrms is not correct in above graphs
 
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KSTR

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I thought that was exactly what it was initially meant for:
Why put the 250 Hz square wave in there if we never see it in the output of the real DAC? When J-test was invented, it was designed to find jitter induced when long runs of AES or S/PDIF cables were used. The toggling would cause all the bits to shift from one value to another, exaggerating sources of jitter there.
Ah, I see the confusion ;-)
To test for jitter, we have to examine either the D-A converted analog signal or use a jitter analyser directly on the digital output (after long cable, vs. short cable).
Whereas you looked at it after conversion from cable signal to digital source signal which is equivalent to looking on the source signal itself (source file) unless we had significant data corruption (flipped bits).
 

KSTR

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Path is as follows:
1. RME ADI-2 Pro fs R (19dBu range, both channels)
2. Radial Engineering SAT-2 Passive attenuator
3. Radial Engineering JDI Duplex - Passive Transformer DI
4. Y XLR cable, summing the 2 channels
5. "Cable" (or direct XLR)
6. Millennia HV-3C Mic Preamp (Max gain -3dB on one channel, Min=9dB gain on second channel)
7. RME ADI-2 Pro fs R (24dBu range, both channels averaged)
Measurements are performed with Virtins Multi-Instrument 3.9.5
I see more difference in the harmonic profile than expected (expected: none).
That might be an effect of different loading on the DI box (but, why did you need a DI in the first place, hum problems?)
If you put the attenuator after the DI the loading of the source side is effectively constant. Using the pad on the DI should keep HD in bounds.

After years of trying, I think that simple periodic signals looked at in the frequency domain are not ideal for finding extremely subtle changes... time-domain with complex signals has more chances to reveal anything. As noted I did not yet find anything that cables would do other than simple linear effects.
 
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