4
\$\begingroup\$

I want to upgrade my retro game setup from a mix of composite and RF to a mix of S-video and component, with some composite for the really old stuff that doesn't support S-video. How can I distinguish the high quality cables and switch boxes from the low quality stuff? What physical properties make these cables and switches better than others?

Edit: I don't think this question is off-topic. It's about determining, without using an O-scope, impedance tester, or other tool, how to buy cables that will faithfully transmit an analog signal and protect it from interference. This has applications not just to my situation, but to hobbyists and tinkerers who don't have access to these tools and doesn't want to spend too much money on expensive cables. This is even more of a hobbyist question because it's mostly focused on RCA cabling, which in the US is still a very common find at garage sales and flea markets.

\$\endgroup\$

closed as off-topic by brhans, Chris Stratton, pipe, Dmitry Grigoryev, Warren Hill May 14 at 14:05

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Questions on the use of electronic devices are off-topic as this site is intended specifically for questions on electronics design." – brhans, pipe, Dmitry Grigoryev, Warren Hill
If this question can be reworded to fit the rules in the help center, please edit the question.

  • 2
    \$\begingroup\$ Unfortunately it's mostly about the internal fit and finish -- there's not much you can tell from the external look, or from marketing bombast. \$\endgroup\$ – TimWescott May 12 at 23:34
  • 3
    \$\begingroup\$ How many insertion cycles is the product rated for? How tough is the outer jacket? How good is the strain relief? If the cables will be visible, then it would be very reasonable to choose them based on having an appealing appearance. Cables should either meet an industry specification, or have full engineering data published. Otherwise it is impossible to judge the quality of the cables (well, maybe you can judge quality based on a large number of reviews). \$\endgroup\$ – mkeith May 12 at 23:39
  • \$\begingroup\$ It is usually simply marketing, plus a small bit of mechanical protection. \$\endgroup\$ – Someone Somewhere May 13 at 0:43
  • 1
    \$\begingroup\$ "impossible to judge" but not impossible to measure and Transfer Impedance is the ONLY way to measure performance here. !! PERIOD. \$\endgroup\$ – Sunnyskyguy EE75 May 13 at 16:46
  • 1
    \$\begingroup\$ Updated question with reason why question is on topic. It's about judging the quality of components, which seems to me like a design question more than a use question. If the community rules that EE Stack Exchange was the wrong place, what would have been the right place? I looked at the other boards and none of the others seemed like they'd be the right place for a question that is essentially about how go to a store or website and buy cables that will alter an analog signal the least. \$\endgroup\$ – VHS May 15 at 0:52
6
\$\begingroup\$

IMHO the integrity of the shielding is what matters. Without shields, RFI and EMI and black-brick switching-requlator spikes are aggressors into and onto the audio.

Foil may be best, but foil is fragile.

Thus multi-layer woven copper-braid [many small wires in the braid, dense enough to block the passage of light] shields should be your goal.

Been working with a guy on piezo-sensors, located a couple meters from the signal conditioning analog-circuitry. He uses 16KHz LPF into buffers, and then 5KHz LPF into the ADC sampling Vin, with that final large capacitor providing the ADC sampling surges.

His usual noise floor, using a 60Hz nulling algorithm to reduce/remove power-line electric fields, is about 1/2 a quanta of 4,096 levels with 0/3.3 volt ADC range.

Thus the RMS is 3.3/8192 or about 400 microVolts RMS, with 2 meters of shielded cable between sensors and analog circuitry.

The "laboratory environment" includes numerous black-brick power supplies, and some unused old computers with metal cases that show 180 degree phase-shift of the 60Hz; a DVM shows 200+ volts between these unused computers and the analog circuitry/sensor returns.

Forgot --- here are several 2Ghz and 5GHz Internet Routers, about 6 feet away. I've carefully encouraged use of passive RC LPFs (15KHz and 5KHz) to reduce high frequency energy into the opamp buffer which might overload input-diffpair isolation-diode junctions; for these LPF's to be effective, the impedance of the LPF's shunt element, the capacitor, has to be low inductance with the capacitor's RTN node tightly wired to input-signal's RTN as well as the output (filtered) signal's RTN).

Thus a comprehensive approach to protecting your audio signal cleanliness is your task:

1) cabling, with densely-woven multiple-layer copper braid shields

2) cable connectors to/from the circuitry, with very short connector--PCB transitions to minimize that loop-area (magnetic field pickup)

3) filtering, to exclude RFI

4) proper use (skilled use) of mechanical structures (planes and cases) to ensure the interference must attempt to pass thru filters, and not be easily routed around the filters

I recall a discussion about a transistor preamp, where a capacitive-path exited from the OUTPUT pin all the way back to the INPUT transistor; the product reviewer showed (by testing) the injection of AM_RF energy into the OUTPUT pin would cause intermodulation (rectification) in the input transistor. Other preamp designs (this was RIAA phono preamps) did not have that capacitive topology, and those other preamps had BETTER reputations in the marketplace. An output RFI filter would have made the difference.

\$\endgroup\$
1
\$\begingroup\$

The measure of low frequency (< 100MHz) shielding effectiveness is called transfer impedance.

The coaxial cable was invented by Heaviside over 100 years ago.

ANSI/NEMA WC 61 January 1, 2005 This standard is intended to provide a reliable surface transfer impedance (STI) test method for coaxial cables and shielded multiconductor cables over the frequency range from DC to 100 MHz. The IEC standard for Surface Transfer Impedance ratio is IEC 62153-4-3

Unfortunately, the s-video cable industry has not rated their products for this.

Solid shields are better than tri-shields which are better than single shields. In between single and tri-shields, it is not intuitively obvious why weave angles and alum. foil differences affect performance. But "usually", the more shield layers, the better the performance.

STI is measured by an induced magnetic field to create an electric field and a voltage difference on the shield per unit length.

REF:

\$\endgroup\$
  • \$\begingroup\$ @ Sunnyskyguy I agree with you on "no obvious difference". The opaqueness of the shield, so far as blocking more and more of the Efield ability to penetrate the shield and reach the center conductor, is best done by foil; but even foil has seams. That's why I stated "multi-layer woven copper braid" as my estimate, in absence of solid-extruded silver-plated tube as the shield. \$\endgroup\$ – analogsystemsrf May 13 at 17:24

Not the answer you're looking for? Browse other questions tagged or ask your own question.