Possible to control TV-cable input volume?

[gunrock]

Various threads exist and in one of them @MWeston says that you can't control input volume through the TV-cable.

I need to do that, but surely I could setup a softvol or something in the ~/.asoundrc file?

Any help here would be appreciated.

 

[levi]

Yes, the connectors on the TV-out cable identify them as stereo line plugs, with volume at line level, intended to be modified by the final amplifier for reproduction. But a software volume limiter would proabably be able to modify the apparent level of this.

I'm afraid I can't really help though. I don't set a global volume level on my systems, only modify it in players such as mplayer or vlc using keyboard shortcuts. That said, is alsamixer installed? That can control system sound levels, although I generally leave it at 100%.

 

[gunrock]

If the data is at line level, I wonder why it clips so much when recorded?

 

[levi]

That depends on what you're recording it on and how you've plugged it in, and whether what you're playing on it has clipping in it at source, I suspect. My ears are fairly well attuned to hearing clipping if it's present, and I've never heard it coming out of my TV-out cable.

 

[TeDaDeS]

So when you connect the Pandora with the TV-out cable to a TV you can't control the volume on the Pandora?

 

[Linux-SWAT]

The applications control the output volume.

 

[gunrock]

To be clear, this recording audio in through the TV cable audio inputs, not the volume of output to the TV thru the cable.

The input is a C64 cassette thru line out of my hifi tape deck and according to the VU meters on that the signal peaks around 6dB. Yet using 'arecord' with the '-VU mono' VU meter on the pandora, it's mostly at 99% full volume.

In Audacity, the signal is clipping. The red is Audacity's "show clipping" view.

As pictures speak a 1000 words, etc., I have attached shots of alsamixer that shows that volume controls for the line in are not available. The mics I have disabled.

It seems to me that there is input gain on the hardware, that is configured somewhere in Alsa on the pandora.

Using a walkman and the headphone jack, with the volume set to low (the thumbwheel turned down to around 2( out of a max of 10), I get a lower input on the VU meter of about 84% for the peaks. This suggests alsa is configured badly for the actual min/max dB range.

I've put the tape deck for now, so can't post a pic of the VU meters on my deck or using arecord, but will maybe do later tomorrow.

 

[levi]

Ah okay. Sorry, I was thinking it was an output problem. I've recorded radio programmes off an old PVR and on to my Pandora back in the day, and I heard no clipping on those. I think the problem may be due to the signal recorded on the C64 tape. I don't think I've ever heard one of those, but I've heard plenty of ZX Spectrum and BBC Micro tapes so I assume they all use two tones (apparently known as FSK) and they're recorded pretty damn loud, for reproducibility's sake.

I'm assuming you've tried at the very least fiddling that master level in alsamixer, and that didn't work. You might be limited to simply adding a resistor into the circuit to attenuate the level, but that's easier said that done, you could mangle an old stereo line level interconnect to do it. I'm not sure if they're normally coaxial or twisted pair or something else.

 

[gunrock]

@levi perhaps I can solder (or tape!) resistors between the tips of the phono jacks on two cables? Thus creating one cable with resistors in the middle?

Actually, I could buy these (but was hoping to not spend too much money):