Connecting Cables

[Jon S]

Patience please as I'm at the forefront for sure! Returning (after 40 years) electronics lover who has acquired a labs-worth of test gear and discovered HP went through many pains to "design" connecting cables for optimum results is killing me. I want to build my own to connect freq gens, SA's, Audio Osc's, counters etc but really want to do this best I can for the results I'm hoping for. Somewhere I read about 59 vs 11 coax....can't find it now but thought it best to sign on & ask here - never too old to learn...again    Actually, this would be a 1st for me seeings as all the equipment here is HP other than a Tek 465B which just arrived a few weeks ago. It's just returning to room temps after crossing the country. Getting back to cables though...open to suggestions for best I could use. SA's run from .02Hz to 25.5 kHz so this is mainly for audio projects I want to keep for life - mostly Studer & Revox & whatever else acts up along the way as they age. I'll stay tuned and thanks in advance.
Joh

[Jon S]

Surely someone out there has had to make their own...anybody? I looked into many but seem to be zeroing in on H&S 223 stranded low loss - seems good as approx lengths would be 10"- 18" max. Would like recommendations also for BNC/50 quality grade. Really don't want to call Francis to see what they used with Lucifer    

[Brumby]

Be patient.  Not everybody who could help you will have seen this thread yet.  Maybe give it a couple more days.

For the sort of cabling you seem to be talking about, I would not be able to offer much help.

I can offer a comment about RG11 coax, though....  Don't expect much in the way of flexibility.

(If anyone is Sydney is interested, I have two rolls of RG11 (~170m all up, I think) buried in the garage somewhere.)

[Jon S]

What you've seen is me being patient! Most frustrating is forgotten knowledge from a Biotech Eng era that had to be put aside for 40 years putting me in the can't even assemble a cable position. Also fell into a gifted position working along side an electrically inclined scientist (never knew his actual title as he was self appointed) that inspired me to build my own o-scope and dec/hex/octal/binary converter to further study software mapping while maintaining an Ampex FR600....all forgotten material. That will go away though / sunny days ahead! Thanks for the reply & info for RG11. Flexibility wouldn't be an issue. Low to no loss is the goal. The pieces will be racked after filtered cooling is in place.

[alm]

Loss is not likely to be an issue at audio frequencies. The Belden RG-58 type cable has an attenuation at 1 MHz (the lowest specified frequency) of less than 1 dB / 100 m, or .005% for a 2 meter cable. For line level single-ended audio most likely any decent type of coaxial cable, regardless of the impedance, will be suitable. For balanced signals you obviously want a balanced cable (e.g. microphone cable). If you work with low level signals, then you might want to look for now noise cables that produce less noise due to piezo/triboelectric effects.

I do not think you will be able to see much difference in electrical perforamance between 50 Ohm and 75 Ohm coax, or low loss vs standard quality, at audio frequencies. So I would take something that is cheap, ubiquitous and fairly flexible. For example RG-58 or RG-174 (thinner, more flexible), or even the stuff sold as audio cable (not from the Monster or $1000 cable crowd).

[madires]

I'd go for RG-174, 50 Ohms BNC crimp connectors, strain relief boots and a proper crimp tool.

[Ian.M]

For audio frequencies, and up to a couple of hundred KHz you wont have any issues simply using BNC to phono adapters and reasonable quality off-the-shelf phono cables.

[Jon S]

For audio frequencies, and up to a couple of hundred KHz you wont have any issues simply using BNC to phono adapters and reasonable quality off-the-shelf phono cables.  [/quote]

For noise tracing with an audio analyzer? Wouldn't the cables themselves act as antennas? Correct me if my thinking is off center - for example, audio boards (recapping etc ) I'd like to avoid bypass caps if possible so signal seeking needs to be ultra clean. I have several Sig & logic analyzers along with spectrum & audio. Some pieces are 50 while others require 75Ohm is why I ask.

I'd go for RG-174, 50 Ohms BNC crimp connectors, strain relief boots and a proper crimp tool.

Thank you - I'll look into this as first I've heard of 174.  I do like the microphone cable idea Alm mentioned. These spectrum analyzers run from DC or .02Hz to 25.5kHz  I could ( no-probably should) make several sets to compare while learning.

[Jon S]

No worries - Monstercable wasn't $$$$ back when I tried it in the 70's for Phase Linear subs & panels. No difference noticed other than fatter cable with bling connectors. Like smoking was 35cents a pack - never again!

Thanks guys - really appreciate it

[Ian.M]

Noise pickup on phono cables depends on the quality.  If its got braid or lapped strands over foil screening and metal shelled connectors, it wont be much worse below a few hundred KHz than RF coax + crimped connectors.  OTOH if its a shitty cable with a partial coverage screen and badly terminated overmoulded plugs at the end, it will probably be highly susceptible to radiated EMI. 

Cable impedance matching doesn't make a significant difference for cables that are a couple of orders of magnitude shorter than a quarter of the wavelength of the maximum frequency of interest.   You can treat them as simple capacitors assuming they have low enough DC resistance.