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Are any passive (or active - unlikely) components used in the 3.5mm mini stereo headphone (TRS) plug to RCA audio plug converter cables, such as this one ?

Asking because, during a quick search I came accross some DIY cable post, where a poster commented that they find the audio volume to be extremely low when using such a cable, indicating serious attenuation.

For line-in/line-out (on PC), I found the following Wikipedia entry that talk of the electrical characteristics, but nothing (so far) for RCA audio connectors and the 3.5" mini (TRS) headphone plug.

Also found this interesting post, but it is in reference to RCA to SPDIF conversion (chain), but still not much helpful with respect to my question.

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No, these cables are simply conductors with different connectors. There should be no difference if both sides of the cable had the same type of connectors or not, barring any manufacturing defects or low grade parts. Cheaper quality cables sound worse, for obvious reasons (Pre-digital audio).

The biggest case of attenuation as it may be, is different audio signal levels. RCA cables are often used for Phono Level signals, while TRS phone plugs are used at Line Level signals. Line Level signals are about 1v, which is ten times what Phono level uses. Mixing a Phone Level output with a Line Level input, and you will get a very quiet sound. Mix Line Level output with Phono Level input, you will get clipping and distortion as it is overdriven. Same reason a passive microphone can't be heard well on a standard input, without amplification.

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  • \$\begingroup\$ Ah, thanks @Passerby. Finally, some electrical characteristics. In my case, the TRS end is the headphone out jack on a RaspberryPi, so can I safely assume it to be line level ? \$\endgroup\$ – bdutta74 Feb 12 '13 at 17:40
  • \$\begingroup\$ @icarus74 they list it as Line Out on the schematic, but no details on it. Not the best quality output in the first place (check their forums). For the most part, you'll be fine. I doubt you will need a pre-amp or anything. It just works. \$\endgroup\$ – Passerby Feb 12 '13 at 17:51
  • \$\begingroup\$ RCA connectors are used for both line-level and phono-level signals. Generally on hifi amplifiers the phono input was/is phono level and everything else is line level. \$\endgroup\$ – Peter Green Oct 2 '17 at 18:50
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No, there shouldn't be anything added.

However, the length and gauge of the cable can cause attenuation and lower volume on the output, since most of the time these cables carry signals that are later amplified. A small drop here can add to noticeable drop on the audio.

Also, there could be some physical damage to the copper and having most of the copper strands broken.

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  • \$\begingroup\$ Thanks @Mando. Are there any standards / specifications for the electrical characteristics of stereo TRS plugs ? Afraid, I do not have a scope, else I could measure, but so far, haven't come across much. \$\endgroup\$ – bdutta74 Feb 12 '13 at 17:10
  • \$\begingroup\$ The specs depend on the device designer. If you're wondering about the voltage, for your RasPi, it would be ~1V (as @passerby noted) and not Phono. \$\endgroup\$ – MandoMando Feb 12 '13 at 21:22
  • \$\begingroup\$ Thank you @MandoMando. Very useful knowing that. Given a chance, I'd also measure it -- just to be sure. For starts will try with a standard DMM. \$\endgroup\$ – bdutta74 Feb 13 '13 at 0:49

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