12 Oct
2004
12 Oct
'04
5:34 p.m.
I am trying to record from a receiver (not sure if that's the right
name, it's the amp/tuner, the thingy that all other components like CD
player, tape deck, video etc. connect to) and it seems like the levels
are too low (the soundcard is soundblaster live platinum, using alsa
drivers that come with kernel 2.6.5).
the receiver has two stereo audio outputs - one is marked as tape
deck recording and the other one as VCR output but both seem to be about
the same (and there doesn't seem to be a way to change them). I connect
them to the RCA connectors on the front panel (live drive) but even if I
set the mixer to 100% (on line in) the levels are too low. On vu-meter
the levels only go to about 25-30% (max) while the 'normal' audio is
somewhere between 50-75%.
I believe both the receiver and soundcard work OK (I can record from
receiver to tape deck, I can record to soundcard from other sources) so
I guess there's mismatch between the signal from receiver and what
soundcard expects. Is there anything I can do? do I need some pre-amp or
something? Seems crazy but does it make any sense to try to record from
speaker outputs? Is there any way to change what soundblaster expects on
input?
TIA
erik
12 Oct
12 Oct
6:01 p.m.
Hi Erik,
Usually audio equipment is setup to output/receive at two possible
levels -10dBu or +4dBV, Semi-pro equipment and home equipment usually
work at -10, which comes up as very low when the receiver is setup for
+4. But I would guess the soundblaster card is setup to work at -10 as
well (I'd be surprised if it isn't).
Maybe there's some software fader somewhere else in the chain?
Maybe you need to turn the volume of the amp/tuner all the way up?
You shouldn't need a preamp, because the amp/tuner thingy should do that
job.
Connecting to the speaker output wouldn't be good since speakers expect
a very high signal, so I would think it wouldn't work...
Andres
Erik Steffl wrote:
I am trying to record from a receiver (not sure if
that's the right
name, it's the amp/tuner, the thingy that all other components like CD
player, tape deck, video etc. connect to) and it seems like the levels
are too low (the soundcard is soundblaster live platinum, using alsa
drivers that come with kernel 2.6.5).
the receiver has two stereo audio outputs - one is marked as tape deck
recording and the other one as VCR output but both seem to be about the
same (and there doesn't seem to be a way to change them). I connect them
to the RCA connectors on the front panel (live drive) but even if I set
the mixer to 100% (on line in) the levels are too low. On vu-meter the
levels only go to about 25-30% (max) while the 'normal' audio is
somewhere between 50-75%.
I believe both the receiver and soundcard work OK (I can record from
receiver to tape deck, I can record to soundcard from other sources) so
I guess there's mismatch between the signal from receiver and what
soundcard expects. Is there anything I can do? do I need some pre-amp or
something? Seems crazy but does it make any sense to try to record from
speaker outputs? Is there any way to change what soundblaster expects on
input?
TIA
erik
7:20 p.m.
Andres Cabrera wrote:
Hi Erik,
Usually audio equipment is setup to output/receive at two possible
levels -10dBu or +4dBV, Semi-pro equipment and home equipment usually
work at -10, which comes up as very low when the receiver is setup for
+4. But I would guess the soundblaster card is setup to work at -10 as
well (I'd be surprised if it isn't).
Maybe there's some software fader somewhere else in the chain?
I don't think so, at least I am not aware of anything. The volume is
too low even when I just use the alsamixer to listen to it. When I
connect other devices (ipod, line6 guitar pod, yamaha dd-55 percussion
pad) the volume is OK.
Actually maybe I could use headphone output, I didn't think of that
(it should be pretty much the same as iPod or guitar pod, I use the same
headphones with all of these).
Maybe you need to turn the volume of the amp/tuner all
the way up?
nothing I do on amp changes the output in any way (volume,
treble/bass, various effects, dolby settings etc.).
erik
You shouldn't need a preamp, because the amp/tuner
thingy should do that
job.
Connecting to the speaker output wouldn't be good since speakers expect
a very high signal, so I would think it wouldn't work...
Andres
Erik Steffl wrote:
I am trying to record from a receiver (not sure
if that's the right
name, it's the amp/tuner, the thingy that all other components like CD
player, tape deck, video etc. connect to) and it seems like the levels
are too low (the soundcard is soundblaster live platinum, using alsa
drivers that come with kernel 2.6.5).
the receiver has two stereo audio outputs - one is marked as tape
deck recording and the other one as VCR output but both seem to be
about the same (and there doesn't seem to be a way to change them). I
connect them to the RCA connectors on the front panel (live drive) but
even if I set the mixer to 100% (on line in) the levels are too low.
On vu-meter the levels only go to about 25-30% (max) while the
'normal' audio is somewhere between 50-75%.
I believe both the receiver and soundcard work OK (I can record from
receiver to tape deck, I can record to soundcard from other sources)
so I guess there's mismatch between the signal from receiver and what
soundcard expects. Is there anything I can do? do I need some pre-amp
or something? Seems crazy but does it make any sense to try to record
from speaker outputs? Is there any way to change what soundblaster
expects on input?
TIA
erik
8 p.m.
On Tue, 12 Oct 2004 14:02:17 -0700, Erik Steffl <steffl(a)bigfoot.com> wrote:
Andres Cabrera wrote:
Possibly it's an impedance mismatch? Possibly the input impedance on
the sound card is too low?
Much of the 'consumer' equipment out there uses high resistance output
drivers since they are less expensive to build. Pro equipment will
almost always use low impedance outputs.
Consider the following:
1V amp PP output -> 1000 Ohm output <---cable----> 1000 Ohm input
In the above pirture to voltage the input receiver sees is 50% of the
voltage actually driven.
Vreceive = Vout * 1000/(1000+1000)
However, consider the following change for pro equipment
1V amp output -> 100 Ohm output <---cable----> 1000 Ohm input
In this circuit the receiver sees 90% of the voltage driven
Vreceive - Vout * 1000/(100+1000)
On the other hand, if the output is high impedance and the input is
low impedance, then you are really messed up:
1V amp PP output -> 1000 Ohm output <---cable----> 100 Ohm input
In this case you get Vreceive = 100/(100+100) or only about 9% of the
voltage transmitted.
This stuff comes up a lot when interfacing studio equipment. This, and
the levels provided as per the post from Andreas, are generall the
root cause of this sort of problem.
Good luck,
Mark
Hi Erik,
Usually audio equipment is setup to output/receive at two possible
levels -10dBu or +4dBV, Semi-pro equipment and home equipment usually
work at -10, which comes up as very low when the receiver is setup for
+4. But I would guess the soundblaster card is setup to work at -10 as
well (I'd be surprised if it isn't).
Maybe there's some software fader somewhere else in the chain?
I don't think so, at least I am not aware of anything. The volume is
too low even when I just use the alsamixer to listen to it. When I
connect other devices (ipod, line6 guitar pod, yamaha dd-55 percussion
pad) the volume is OK.
Actually maybe I could use headphone output, I didn't think of that
(it should be pretty much the same as iPod or guitar pod, I use the same
headphones with all of these).
Maybe you need to turn the volume of the
amp/tuner all the way up?
nothing I do on amp changes the output in any way (volume,
treble/bass, various effects, dolby settings etc.).
erik
> You shouldn't need a preamp, because the amp/tuner thingy should do that
> job.
> Connecting to the speaker output wouldn't be good since speakers expect
> a very high signal, so I would think it wouldn't work...
>
> Andres
>
> Erik Steffl wrote:
>
>> I am trying to record from a receiver (not sure if that's the right
>> name, it's the amp/tuner, the thingy that all other components like CD
>> player, tape deck, video etc. connect to) and it seems like the levels
>> are too low (the soundcard is soundblaster live platinum, using alsa
>> drivers that come with kernel 2.6.5).
>>
>> the receiver has two stereo audio outputs - one is marked as tape
>> deck recording and the other one as VCR output but both seem to be
>> about the same (and there doesn't seem to be a way to change them). I
>> connect them to the RCA connectors on the front panel (live drive) but
>> even if I set the mixer to 100% (on line in) the levels are too low.
>> On vu-meter the levels only go to about 25-30% (max) while the
>> 'normal' audio is somewhere between 50-75%.
>>
>> I believe both the receiver and soundcard work OK (I can record from
>> receiver to tape deck, I can record to soundcard from other sources)
>> so I guess there's mismatch between the signal from receiver and what
>> soundcard expects. Is there anything I can do? do I need some pre-amp
>> or something? Seems crazy but does it make any sense to try to record
>> from speaker outputs? Is there any way to change what soundblaster
>> expects on input?
>>
>> TIA
>>
>> erik
13 Oct
13 Oct
12:34 a.m.
Mark Knecht wrote:
...
>>> I am trying to record from a receiver
(not sure if that's the right
>>>name, it's the amp/tuner, the thingy that all other components like CD
>>>player, tape deck, video etc. connect to) and it seems like the levels
>>>are too low (the soundcard is soundblaster live platinum, using alsa
>>>drivers that come with kernel 2.6.5).
...
1V amp PP output -> 1000 Ohm output
<---cable----> 1000 Ohm input
In the above pirture to voltage the input receiver sees is 50% of the
voltage actually driven.
...
This stuff comes up a lot when interfacing studio
equipment. This, and
the levels provided as per the post from Andreas, are generall the
root cause of this sort of problem.
that might be the case, I see the signal being at about 20-40%,
compared to about 50-70% 'normal' signal (in vu-meter).
the big Q remains - what do I do? (I didn't try the headphones output
yet, but everybody says that headphones output on the consumer receivers
is of poor quality (then again, I listened to it via headphones and it
was good enough for me...)).
erik
1:37 a.m.
On Tue, 12 Oct 2004 19:16:37 -0700, Erik Steffl <steffl(a)bigfoot.com> wrote:
Mark Knecht wrote:
...
Well, I'd guess the best answer, if this is what's really going on, is
to use an impedance matching transformer of some type. Get a high
input impedance, lower output impedance model. Don't know what this
would cost. Probably not cheap, but not really expensive either. This
is very typical for stage work. they get used to turn single ended
into balanced/differential signals, etc., so that you can run long
distances.
Another possibility would be to find a secondary amp to put in the
middle. A good quality headphone amp or something like that *might*
work.
These are all guesses. Take it with a grain of salt.
- MArk
>>> I am trying to record from a
receiver (not sure if that's the right
>>>name, it's the amp/tuner, the thingy that all other components like CD
>>>player, tape deck, video etc. connect to) and it seems like the levels
>>>are too low (the soundcard is soundblaster live platinum, using alsa
>>>drivers that come with kernel 2.6.5).
...
1V amp PP output -> 1000 Ohm output
<---cable----> 1000 Ohm input
In the above pirture to voltage the input receiver sees is 50% of the
voltage actually driven.
...
This stuff comes up a lot when interfacing studio
equipment. This, and
the levels provided as per the post from Andreas, are generall the
root cause of this sort of problem.
that might be the case, I see the signal being at about 20-40%,
compared to about 50-70% 'normal' signal (in vu-meter).
the big Q remains - what do I do? (I didn't try the headphones output
yet, but everybody says that headphones output on the consumer receivers
is of poor quality (then again, I listened to it via headphones and it
was good enough for me...)).
erik
6:08 a.m.
On Tue, Oct 12, 2004 at 02:42:59PM -0700, Mark Knecht wrote:
Much of the 'consumer' equipment out there
uses high resistance output
drivers since they are less expensive to build. Pro equipment will
almost always use low impedance outputs.
I'd expect most consumer equipment to use op-amp based gain blocks which
are cheap enough and have very low output impedance. Usually the output
has a resistor (100 ohm or so) in series for protection against
instability.
[snip explanation of impedance mismatching]
1V amp PP output -> 1000 Ohm output
<---cable----> 100 Ohm input
100 ohms is very unlikely for an input. Even a low-z mic input has an
impedance of over 1k, and a consumer line level input is likely to be
10k.
The actual voltage levels used by consumer equipment do vary, though.
There is a semi-professional standard of -10dBu for RCA connectors, but
domestic equipment does not necessarily follow that. You often see that
in a stereo 'separates' system where you routinely have to adjust the
volume when switching between tuner/CD player/tape etc.
I suspect this may actually not be too much of a problem.
25% of the way up a VU meter (VU meters are linear) means 12 dB below
full scale, and a 16 bit digitized signal will actually be 14 bits.
So boost the gain electronically (e.g. with normalize, or I'm
sure sox or ecasound can do it too) after it's in the computer. There
will in theory be some loss of signal-noise ratio, but as the original
poster was using a Sound Blaster, we're not talking about professional
audio here.
A professional-grade sound input device would either have variable
analogue gain to match the input level precisely, or acccurately
specified input level requirements so the user knew exactly what to
expect.
--
Anahata
anahata(a)treewind.co.uk Tel: 01638 720444
http://www.treewind.co.uk Mob: 07976 263827
15 Oct
15 Oct
1:38 p.m.
New subject: solved? Re: [linux-audio-user] [OT] recording levels (mismatch)
Erik Steffl wrote:
looks like headphones output works pretty well. I don't get
unprocessed signal (i.e. volume, treble/bass, effect (dolby, room
type...) etc. are all there so I have to be careful about the settings
on the receiver) but the signal is strong enough (matching what
soundblaster expects).
any comments? gotchas?
btw I am using gramofile to split the resulting wav into songs and
clean-up the signal. The song splitting works pretty good but I was
wondering what other people use to clean the sound (specifically the
signal from vinyl records).
erik
Andres Cabrera wrote:
> Hi Erik,
> Usually audio equipment is setup to output/receive at two possible
> levels -10dBu or +4dBV, Semi-pro equipment and home equipment usually
> work at -10, which comes up as very low when the receiver is setup for
> +4. But I would guess the soundblaster card is setup to work at -10 as
> well (I'd be surprised if it isn't).
sony STR-SE581
voltage 150mV
impedance 10kOhms
I couldn't find the specs for soundblaster RCA inputs (the docs just
say it's an aux in, no details), on some sites there are some numbers
but I haven't been able to figure out whether they apply to RCA or other
inputs. I also found out that if I connect it to line 2 (the jack right
below RCA inputs) and use the mic gain knob the signal gets amplified
enough to be usable. Unfortunately it's mono (it's just one channel).
the creative.com knowledge base search revealed:
Line In Full Scale Input 2.0 Vrms
Line In Impedance 10k ohms
what is Vrms? I guess it has something to do with voltage... should
2.0 Vrms play nicely with 150mV?
Maybe
there's some software fader somewhere else in the chain?
I don't think so, at least I am not aware of anything. The volume is
too low even when I just use the alsamixer to listen to it. When I
connect other devices (ipod, line6 guitar pod, yamaha dd-55 percussion
pad) the volume is OK.
Actually maybe I could use headphone output, I didn't think of that
(it should be pretty much the same as iPod or guitar pod, I use the same
headphones with all of these).
2:29 p.m.
New subject: solved? Re: [linux-audio-user] [OT] recording levels (mismatch)
On Fri, Oct 15, 2004 at 08:19:36AM -0700, Erik Steffl wrote:
sony STR-SE581
voltage 150mV
impedance 10kOhms
the creative.com knowledge base search revealed:
Line In Full Scale Input 2.0 Vrms
Line In Impedance 10k ohms
what is Vrms? I guess it has something to do with voltage... should
2.0 Vrms play nicely with 150mV?
Root Mean Square, which technically means the DC voltage that develops
the same power in resistive load as the AC signal would... a sort of
average and a reasonable way of comparing volume levels.
No, it wouldn't play nicely - your 150mV output is, as shown, rather low
for an input that expects 2V and that explains ithe low levels you are
seeing.
looks like headphones output works pretty well. I
don't get
unprocessed signal (i.e. volume, treble/bass, effect (dolby, room
type...) etc. are all there so I have to be careful about the settings
on the receiver) but the signal is strong enough (matching what
soundblaster expects).
any comments? gotchas?
As you say, the volume and other controls affect it - but that's the
only problem, and you can live with that - just don't touch them once
set up correctly!
--
Anahata
anahata(a)treewind.co.uk -+- http://www.treewind.co.uk
Home: 01638 720444 Mob: 07976 263827
2:57 p.m.
New subject: solved? Re: [linux-audio-user] [OT] recording levels (mismatch)
On Fri, 15 Oct 2004 17:11:50 +0100, anahata <anahata(a)treewind.co.uk> wrote:
On Fri, Oct 15, 2004 at 08:19:36AM -0700, Erik Steffl
wrote:
> sony STR-SE581
> voltage 150mV
> impedance 10kOhms
>
> the creative.com knowledge base search revealed:
> Line In Full Scale Input 2.0 Vrms
> Line In Impedance 10k ohms
>
> what is Vrms? I guess it has something to do with voltage... should
> 2.0 Vrms play nicely with 150mV?
Basically that a 2V sine wave on the input of the Sound Blaster would
give you full volume.
On the other hand, if the Sony only puts out 150mV at full volume then
you are not driving the SB very hard.
Couple this with a 10K output impeadance and a 10K input impedance and
your 150mV is cut in half to 75mV into a 2V input. That's pretty low
in my mind...
4:33 p.m.
New subject: solved? Re: [linux-audio-user] [OT] recording levels (mismatch)
Mark Knecht wrote:
On Fri, 15 Oct 2004 17:11:50 +0100, anahata
<anahata(a)treewind.co.uk> wrote:
rms is a way to mesure AC voltage,
In case of a sine, 2Vmrs corresponds with a sine of 2*sqrt(2) V of
amplitude.
take a look at http://www.doctronics.co.uk/rms.htm
(it's always good to learn new things :)
On Fri, Oct 15, 2004 at 08:19:36AM -0700, Erik
Steffl wrote:
> sony STR-SE581
> voltage 150mV
> impedance 10kOhms
>
> the creative.com knowledge base search revealed:
> Line In Full Scale Input 2.0 Vrms
> Line In Impedance 10k ohms
>
> what is Vrms? I guess it has something to do with voltage... should
>2.0 Vrms play nicely with 150mV?
>
>
Basically that a 2V sine wave on the input of the Sound
Blaster would
give you full volume.
On the other hand, if the Sony only puts out 150mV at full volume then
you are not driving the SB very hard.
Couple this with a 10K output impeadance and a 10K input impedance and
your 150mV is cut in half to 75mV into a 2V input. That's pretty low
in my mind...
13 Oct
13 Oct
5:30 a.m.
Erik Steffl a écrit :
I am trying to record from a receiver (not sure if
that's the right
name, it's the amp/tuner, the thingy that all other components like CD
player, tape deck, video etc. connect to) and it seems like the levels
are too low (the soundcard is soundblaster live platinum, using alsa
drivers that come with kernel 2.6.5).
the receiver has two stereo audio outputs - one is marked as tape deck
recording and the other one as VCR output but both seem to be about the
same (and there doesn't seem to be a way to change them). I connect them
to the RCA connectors on the front panel (live drive) but even if I set
the mixer to 100% (on line in) the levels are too low. On vu-meter the
levels only go to about 25-30% (max) while the 'normal' audio is
somewhere between 50-75%.
I believe both the receiver and soundcard work OK (I can record from
receiver to tape deck, I can record to soundcard from other sources) so
I guess there's mismatch between the signal from receiver and what
soundcard expects. Is there anything I can do? do I need some pre-amp or
something? Seems crazy but does it make any sense to try to record from
speaker outputs? Is there any way to change what soundblaster expects on
input?
TIA
erik
Using Google I was able to find the specification of the electrical
inputs of the SBLive :
http://grassomusic.de/english/rauschen.htm
The Line In input impedance is 47K so it is unlikely a problem of
impedance mismatch since the line out of your amp/tuner should have an
output impedance of at least 1K. The Line in full scale output is
however 1.5Veff. Since -10dBV = 0.32Veff and +4dBu = 0.775 Veff, 1.5Veff
is quite a large value compared to audio standards but using alsamixer
(or any other mixer) you should be able to adjust the input sensitivity.
Have you try using the Line In on the pci board instead of the one on
the Live drive. There was issues regarding the Live Drive input with
alsa drivers some time ago. I do not know if it has been fixed.
In any case you should consider using a preamp or a cheap console to
adjust the levels since the SBlive level adjustement is done after
Analog to Digital Conversion, a bad thing.
Christophe
6:38 a.m.
On Wed, Oct 13, 2004 at 09:24:02AM +0200, Christophe Vescovi wrote:
output impedance of at least 1K. The Line in full
scale output is
however 1.5Veff. Since -10dBV = 0.32Veff and +4dBu = 0.775 Veff
No, 0dBu is 0.775V and +4dBu is 1.23Vrms which is close to the
specified input of the SB.
Looks like it's nominal +4dBu input, which would explain everything.
In any case you should consider using a preamp or a
cheap console to
adjust the levels since the SBlive level adjustement is done after
Analog to Digital Conversion, a bad thing.
Agreed; in an earlier message I did suggest conversion in the digital
domain, but amplifying the analog signal is certainly a better solution,
if more expensive.
--
Anahata
anahata(a)treewind.co.uk Tel: 01638 720444
http://www.treewind.co.uk Mob: 07976 263827
8:33 a.m.
Anahata a écrit :
On Wed, Oct 13, 2004 at 09:24:02AM +0200, Christophe
Vescovi wrote:
Right !! I should have take my coffee before writing this ;-)
Christophe
output impedance of at least 1K. The Line in full
scale output is
however 1.5Veff. Since -10dBV = 0.32Veff and +4dBu = 0.775 Veff
No, 0dBu is 0.775V and +4dBu is 1.23Vrms which is close to the
specified input of the SB.
Looks like it's nominal +4dBu input, which would explain everything.
7391
days inactive
7394
days old
linux-audio-user@lists.linuxaudio.org
13 comments
6 participants
participants (6)
-
Anahata -
Andres Cabrera -
Christophe Vescovi -
Erik Steffl -
MarC -
Mark Knecht