[audioengr]

I have never been able to hear any difference using different inputs cables to the SM, but based on customer feedbacks, I took some measurements. The jitter distribution plots are all very similar, so instead I post the frequency spectrum of these where you can see differences.  All use my reference output cable:

Cheap BNC input cable:



First spike at 1MHz is fairly small.

Plastic Toslink input cable:



The center peak is about 1/2 the height of the cheap BNC, but it is about twice as wide.  Some new wiggles at 300kHz.

Belden 1694A input cable:



Belden is about the same as the Toslink.

Empirical Audio Reference BNC used as input cable:



This is significantly better.  Center spike around 3MHz is not very tall and very thin. 1MHz spike seen in the other plots is gone.  Noise floor much lower but there is a large spike at 6MHz that the other cables do not have.

It's clear from these that the jitter at higher frequencies is definitely affected by the quality of the input cable.  The difference between the $20 cheap BNC and my $499 reference BNC cable is not significant though.  I will do some listening tests to see if I can hear any difference.

Steve N.

[Speedskater]

Do all three coax cables use the same 75 Ohm BNC connectors?

[audioengr]

Do all three coax cables use the same 75 Ohm BNC connectors?

The cheap BNC uses 50 ohm connectors on a 75 ohm cable.  The 1694A is soldered to RCA's.  Only the Empirical Audio cable has 75 ohm BNCs on a 75 ohm cable.

I don't believe its the connectors causing the difference between the cheap BNC and the Reference BNC.  It's the cable.

I do believe that the RCA's are probably mucking-up the 1694A, not so much because of the connector, but the method of termination screwing-up the impedance.  The cable itself is not great either.

Steve N.

[FullRangeMan]

Wow dramatic results
Its nice when an manufacturer have this clear results, an easy choice.

[audioengr]

Wow dramatic results
Its nice when an manufacturer have this clear results, an easy choice.

Dramatic, yes, relevant, maybe.  The differences are all at MHz frequencies.  There is almost no difference up to 300kHz.

We will find out soon if the MHz  differences are audible or not. Stay tuned.

Steve N.

[FullRangeMan]

Dramatic, yes, relevant, maybe.  The differences are all at MHz frequencies.  There is almost no difference up to 300kHz.

We will find out soon if the MHz  differences are audible or not. Stay tuned.

Steve N.

Do this diference located at hi freq are audible when custumer use an OTL amp as Atma-Shere which bandwith reach 1MHz?

[audioengr]

Do this diference located at hi freq are audible when custumer use an OTL amp as Atma-Shere which bandwith reach 1MHz?

Possible, but depends on the bandwidth of your DAC and preamp too.  At this point I recommend at least a BNC broadcast cable with true 75 ohm connectors, used with my 75 ohm RCA adapters. This is only $20 including shipping from Markertek:

https://www.markertek.com/product/dsb-b-3/double-shielded-premium-75-ohm-bnc-broadcast-cable-3ft-black

What I want to determine is whether it is necessary to spend any real money on the input cable.

Steve N.

[FullRangeMan]

Oh Nice its a great value/price cable

[Speedskater]

Lots of uncontrolled variables in the above experiment, not exactly a good test.
Not with one cable having 50 Ohm BNC's, one with RCA's and one with 75 Ohm BNC's.

* * * * * * * * * *
A good test would have:
a] All cables have the same Radio Frequency Characteristic Impedance.
b] All cables be the same length.
c] All cables use the same connectors.

[paul79]

Steve, when are you going to build me some AES/EBU cables to try out? Figure out what make these tick would ya??

Guys, Steve's $250 SPDIF Cable is the real deal and easily betters everything I have tried. I cannot wait to try the Reference!

[audioengr]

Steve, when are you going to build me some AES/EBU cables to try out? Figure out what make these tick would ya??

Guys, Steve's $250 SPDIF Cable is the real deal and easily betters everything I have tried. I cannot wait to try the Reference!

I have some 110 ohm wire here, but it's copper with Teflon insulation.  I wish I could find the same thing in silver with expanded Teflon...  The other problem is XLR connectors that are not 110 ohms...

BTW, the Standard BNC cable is now $275.

Steve N.

[audioengr]

Lots of uncontrolled variables in the above experiment, not exactly a good test.
Not with one cable having 50 Ohm BNC's, one with RCA's and one with 75 Ohm BNC's.

* * * * * * * * * *
A good test would have:
a] All cables have the same Radio Frequency Characteristic Impedance.
b] All cables be the same length.
c] All cables use the same connectors.

It delivered the results I was after.  The objective was to determine how a wide variety of input cables might affect the jitter.  This was not about apples to apples comparison to determine the best cable of a particular type. 

This would make sense for the output cable or a second round with the input cable, assuming that any sound quality differences are audible between a $20 BNC and a $500 BNC cable.  This is the first thing to determine.  If there is no difference, then it makes no difference whether one uses a cheap BNC cable with 50 ohm connectors or and expensive BNC cable with 75 ohm connectors or a plastic Toslink for the input cable.

Steve N.

[audioengr]

Listening test results:

Every plot that looked better also sounded better, but the differences were small, mostly in the very high frequencies.  One track I like to use is The Doors "Riders in the Storm", which has rain in the background and some not so good thunder.  The rain is very lifelike when I use the Standard BNC as input cable.  I could barely make out the raindrops when using the plastic Toslink.  Also, some of the cymbol work was not obvious.   I tried a good glass Toslink and the raindrops were audible, but not as clear as the Standard BNC.  Most of the cables sounded similar for the vocalist in the track, but the Standard BNC was much more 3-D and lifelike.

Based on these results,  my recommendation for optimizing the Synchro-Mesh is to use the Standard BNC as input and the Reference BNC as output for optimum results.

Steve N.