Connecting Cables - Page 1
Forum section: electronics / beginners

author: Jon S
author_rank: Newbie
timestamp: March 24, 2017, 11:19:50 pm
content: 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...againActually, 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

author: Jon S
author_rank: Newbie
timestamp: March 26, 2017, 03:14:25 am
content: 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

author: Brumby
author_rank: Unknown
timestamp: March 26, 2017, 04:32:18 am
content: 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.)

author: Jon S
author_rank: Newbie
timestamp: March 26, 2017, 03:41:54 pm
content: 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.

author: alm
author_rank: Super Contributor
timestamp: March 26, 2017, 04:07:45 pm
content: Loss is not likely to be an issue at audio frequencies. TheBelden RG-58 type cablehas 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).

author: madires
author_rank: Super Contributor
timestamp: March 26, 2017, 04:22:41 pm
content: I'd go for RG-174, 50 Ohms BNC crimp connectors, strain relief boots and a proper crimp tool.

author: Ian.M
author_rank: Super Contributor
timestamp: March 26, 2017, 04:44:00 pm
content: 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.

author: Jon S
author_rank: Newbie
timestamp: March 26, 2017, 07:05:11 pm
content: 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. 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.Quote from: madires on March 26, 2017, 04:22:41 pmThank 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.

author: Jon S
author_rank: Newbie
timestamp: March 26, 2017, 07:10:46 pm
content: 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

author: Ian.M
author_rank: Super Contributor
timestamp: March 26, 2017, 07:31:33 pm
content: 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.