Audio Noise

[Spies]

Is there any way to reduce or eliminate background hiss? I'm using the phono outputs from a Satellite STB so I can't get any better, there is an obvious hiss though when you're listening to it through headphones through sagetv.

Cheers

[kny3twalker]

what recording profile are you using?
you may want to make sure it has an audiosampling of 48000
and a audiobitrate of 384
also try different audio rendering and some audio decoders are better than others

[justme]

Is it a hiss or hum? If it's a hum you could have a ground issue. But from the way you described it that doesn't sound right, so I won't go into ground issues.

If it's a hiss then make sure you're using good quality RCA cables, especially if you have a long run. You can also try feeding the STB's RCA audio directly into you AMP(if you have one) to see if the hiss is there as well. If it is you can change out the cable and try again. If it's still there on your Amp and it is a hiss then you may want to request a replacement converter box. Edit:Whoops, I just remembered you said Satellite. Sorry, I'm so used to cable.

Anyway, the key is to find out where the bad audio is being introduced(STB, RCA cables/connectors, PVR capture card(unlikely unless the card is bad), soundcard, etc). Standard troubleshooting practice. Then you can work on that area.

[Spies]

Best way to show the noise is for you to hear it firsthand, so I've created a sample for you.

http://inara.lewww.com/~carl/sample.avi

[kny3twalker]

I could not hear it until I turned the volume up to the highest volume
and then it makes me believe as well that it is a cable problem

if you think it is an issue with the pvr card then just make sure your drivers are up to date (but I have been seeing this alot)

you should try the better cables like justme said

[zz5]

Spies,

Are you listening to headphones directly from the Satellite STB? Are there left and right audio channels, and you are combining them somehow to form the single input for your headphones?

[Spies]

The Stereo signal is preserved.

[zz5]

I don't understand how the signal is getting to your headphones though. Are you using a passive combiner? Do you have 2 RCA outputs going to an amp? Since you mentioned "outputs" instead of "output", I assumed that there isn't a heapdhone jack on the STB. I'm not familiar with what outputs would be on a Satellite STB. Are these outputs line level? Are they amplified? Just looking at your first post without knowing anything more, the problem appears to be an impedance matching problem.

[Spies]

I'm in England, we don't use stuff like that, the Sky box has scart and phono out's. I'm using a breakout scart with phono's for the audio.

The RCA connector goes directly to the PVR-250.

[zz5]

I still don't understand. What are the headphones plugged into?

[justme]

What are the headphones plugged into?

His computer in all likely hood. He is after all talking about this isuue in the SageTv forums.

Seriously I don't know too much about England and SCART. But here in the US there's a difference between a Phono jack and most RCA jack's input/output. They both use the same style connector but I believe the old Phono standard is at a higher level. Anyway I can't see them using the actual Phono standard for SCART. Here in the US, basically all stereo RCA jacks but the Phono(for an actual record player) use the same impedance/voltage levels.

But anyway it could be an impedance issue, but then you'd think we'd have heard more talk from other international users. I'm not eliminating it. Man this has turned into a descussion on home AV, rather than his Sage issue. I'm not saying all this isn't valid, just that without him narrowing it down first we won't know where to look/suggest.

[kny3twalker]

I am guessing that he is using RCA right and left to (phono/headphone input) in the pvr 250 and then is using the microphone output port on his sound card and is hearing this??????????
That would be how I would do it .........

[utica]

I don't know if your SCART "phono" output is truly phonograph outputs.

However, in the US, turntable/phonograph outputs are in the mV range and you need a pre-amp (usually on older amplifiier/receivers or you can get a stand-alone one) to boost the signal above and beyond any hiss. For example, recording vinyl LPs to mp3 would require a pre-amp before going into the sound card inputs.

Sometimes you will have a hum that can be eliminated by grounding the turntable to the pre-amp.

[justme]

utica, Personal thanks, for clearing up my confusion over the exact Phono standard(I should've gotten out my electronics books). I haven't played a real record in over 15 years, although my AV AMP does have a true phono intput along with all the others. I just remembered there was a difference and they shouldn't be mixed. Thanks for clarifying.

PS:Spies, Is there any word on if you've narrowed it down to a specific area. Did you at least try different cables?

/Justme

[Spies]

I have tried a couple of different cables but neither are of particulary high quality.

[zz5]

If you connect headphones to an output with electronics optimized for speakers, you will hear hiss. That's what I was talking about. The problem is that the headphones have low impedance (high sensitivity). Speakers have high impedance (low sensitivity). Headphones need to have low impedance so they will be easier to drive by portable equipment. Speakers are bigger with longer cable so they impede the electricity flow more. An amplifier designed for speakers is a lot noiser because it's hard to make it quiet when it needs to output a lot of power. An amplifier optimized for heapdhones can't put out as much power, but will be very quiet. Sometimes when you're listening to an output with electronics optimized for speakers, the sound will be kind of murky sounding also. If there is hiss with headphones but not with speakers, as seems to be implied in the first post, that's a dead giveaway of an impedance problem. Headphone jacks on big expensive receivers will often be noisy because they are just using a line from the single main amplifier. Most people won't use the headphone jack much. A cheap walkman will have a hissless headphone jack. Another thing to consider is that headphones reveal more detail and so maybe that's at least part of the reason why you can hear the hiss.