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Adam Stouffer
Guest
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 Posted:
Sat Dec 10, 2005 1:36 am Post subject:
Automatic Volume Limiter |
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Anyone have a schematic for something to limit the volume from line
level sources? I hate watching a tv show or movie and then getting
blasted by a commercial at twice the volume.
Adam
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Joe G (Home)
Guest
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| Posted:
Sat Dec 10, 2005 9:35 am Post subject:
Re: Automatic Volume Limiter |
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in Australia i think there is a limit on loudness... however they get
around this law using a compressor,
So the aduio is compressed up to the limit.
JG
"Adam Stouffer" <adam_stouffer@hotmail.com> wrote in message
news:Bxnmf.41$pF.10@trndny08...
| Quote: | Anyone have a schematic for something to limit the volume from line level
sources? I hate watching a tv show or movie and then getting blasted by a
commercial at twice the volume.
Adam |
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Dave Moore
Guest
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| Posted:
Sat Dec 10, 2005 9:35 am Post subject:
Re: Automatic Volume Limiter |
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I built an AVC for my brother for the same purpose
Used a NE571 IC since I had a few on hand.
Dunno if it's even still available
I even went the full 9 yards and designed in
an IR receiver so he could switch it in or out
without distrupting any couch potato status.
There are apparently some turn-key devices
available;
http://www.google.com/search?hl=en&q=Automatic+volume+control&btnG=Google+Search
"Adam Stouffer" <adam_stouffer@hotmail.com> wrote in message news:Bxnmf.41$pF.10@trndny08...
: Anyone have a schematic for something to limit the volume from line
: level sources? I hate watching a tv show or movie and then getting
: blasted by a commercial at twice the volume.
:
:
: Adam
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Rich Grise
Guest
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| Posted:
Sat Dec 10, 2005 5:35 pm Post subject:
Re: Automatic Volume Limiter |
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On Fri, 09 Dec 2005 22:27:45 +0000, Adam Stouffer wrote:
| Quote: | Anyone have a schematic for something to limit the volume from line
level sources? I hate watching a tv show or movie and then getting
blasted by a commercial at twice the volume.
|
What I'd like to find is something in the VBI stream that identifies
"Commercial", to make the VCR "pause" and skip the bloody things.
Then again, the advertisers do keep TV free, "the way God intended it
to be."[1] ;-)
Cheers!
Rich
[1] Dave Letterman |
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John S. Dyson
Guest
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| Posted:
Sat Dec 10, 2005 6:36 pm Post subject:
Re: Automatic Volume Limiter |
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In article <Bxnmf.41$pF.10@trndny08>,
Adam Stouffer <adam_stouffer@hotmail.com> writes:
| Quote: | Anyone have a schematic for something to limit the volume from line
level sources? I hate watching a tv show or movie and then getting
blasted by a commercial at twice the volume.
There are some schematics on the www.thatcorp.com website. They |
use proprietary devices, but are arguably one of the best ways to do the
job.
Another good way (something that a hardware hacker could make work)
would be to use a photoresistive device along with a LED (various
companies used to make those.) The response time of the photoresistive
cell is slower, but that can actually be advantageous WRT the effects
on perception. (A similar effect can be done by using the RMS detector
and VGA scheme, but the idea of attack/release time constants should
be generalized so as to get the best audible effects.)
If you are interested only in mono, you could use a JFET in a voltage
variable resistor mode. Matching problems would make stereo a little
less fun.
John |
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Ken Smith
Guest
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| Posted:
Sat Dec 10, 2005 10:17 pm Post subject:
Re: Automatic Volume Limiter |
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In article <Bxnmf.41$pF.10@trndny08>,
Adam Stouffer <adam_stouffer@hotmail.com> wrote:
| Quote: | Anyone have a schematic for something to limit the volume from line
level sources? I hate watching a tv show or movie and then getting
blasted by a commercial at twice the volume.
|
One attack of the problem:
Comparitor
LM311 Sign
--!>---------------------------------------------
! ------ !
! ------- ------ ! High ! ------- ---
In -----+--! ABS() !---! ln() !--! pass !---! exp() !---! X !-- Out
------- ------ ------ ------- ---
One advantage this has is that the ln() and exp() operations can be quite
well matched and tend to track with temperature. Also, the high pass can
have a few poles in it without stability problems.
Other method:
Any normal feedback based one, needs a quite linear multiplier to sound
any good. You may be able to take advantage of the fact that for normal
volume levels you don't want to change the sound at all. I'm thinking of
something like this:
Audio
quality
buffer
!\
-\/\/\---+---------! >-----------------+--------------- Out
! !/ !
! --------
! J1 U1 LM324 ish ! -ABS() !
--! /+!--GND --------
!<--+---< ! D1 R1 !
--! ! \-!--+-->!--/\/\--+
! ! ! R2 !
GND +---!!----+---/\/\/-----
C1 !
---/\/\-- +Vref
R3
The Jfet J1 is selected for having a high Vgs off.
D1 is a 1N914 like diode.
The output of U1 normally rests at the (-) supply rail. Op-amps like the
LN324 don't have diodes across their inputs so C1 will charge up to more
than just the rail voltage. Vref, R3, R2, D2 and R1 sets the amount of
"integrator wind up".
When someone shoots the bad guy, there is bang. If it isn't followed by
abunch more noise, R1 and D1 won't be able to discharge C1 far enough to
start the output of the LM324 going positive, so you won't effect the
sound.
When the soap ad comes on, The output of U1 (LM324) will swing positive
and reduce the sound. A fair bit of distortion will be added but you may
not care.
--
--
kensmith@rahul.net forging knowledge |
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Luhan
Guest
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| Posted:
Sun Dec 11, 2005 1:35 am Post subject:
Re: Automatic Volume Limiter |
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Rich Grise wrote:
| Quote: | On Fri, 09 Dec 2005 22:27:45 +0000, Adam Stouffer wrote:
Anyone have a schematic for something to limit the volume from line
level sources? I hate watching a tv show or movie and then getting
blasted by a commercial at twice the volume.
What I'd like to find is something in the VBI stream that identifies
"Commercial", to make the VCR "pause" and skip the bloody things.
Then again, the advertisers do keep TV free, "the way God intended it
to be."[1] ;-)
Cheers!
Rich
[1] Dave Letterman
|
Rich,
I've looked at the VBI data - no go. It varies from station to station
but not really durring commercials.
I have an approach to killing commercials, but it requies a 'video out'
from the TV. Its just like my intrution detector....
http://members.cox.net/berniekm/videodet.gif
You take an array of 8 by 8 samples of the video at very low resolution.
This forms a pattern that rarely occurs by accident.
When you see a comercial you really hate, you hit a button to store an
image near the start of the commercial. When it detects this pattern in
the future, it kills the sound for 1 minute.
Hmmm, I may make one just to prove it out.
Luhan |
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Pooh Bear
Guest
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| Posted:
Sun Dec 11, 2005 9:01 am Post subject:
Re: Automatic Volume Limiter |
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Adam Stouffer wrote:
| Quote: | Anyone have a schematic for something to limit the volume from line
level sources? I hate watching a tv show or movie and then getting
blasted by a commercial at twice the volume.
|
I suggest you look here for starters.
The 'audiohm' couplers are available from Farnell and I can attest they
they work well. In fact I've been using them for around 10 ? yrs in my
designs.
Nice thing about a CdS cell is that it's typically more linear than any
solid state multiplier chip and has no DC conditions that require set
up. A breeze to use and not even expensive.
Graham |
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Pooh Bear
Guest
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| Posted:
Sun Dec 11, 2005 9:35 am Post subject:
Re: Automatic Volume Limiter |
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Pooh Bear wrote:
| Quote: |
Adam Stouffer wrote:
Anyone have a schematic for something to limit the volume from line
level sources? I hate watching a tv show or movie and then getting
blasted by a commercial at twice the volume.
I suggest you look here for starters.
|
Oops ! Missed the link last time....
http://www1.silonex.com/audiohm/compressor.html
| Quote: | The 'audiohm' couplers are available from Farnell and I can attest they
they work well. In fact I've been using them for around 10 ? yrs in my
designs.
Nice thing about a CdS cell is that it's typically more linear than any
solid state multiplier chip and has no DC conditions that require set
up. A breeze to use and not even expensive.
Graham
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GregS
Guest
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| Posted:
Mon Dec 12, 2005 5:35 pm Post subject:
Re: Automatic Volume Limiter |
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In article <pan.2005.12.10.17.15.26.869129@example.net>, Rich Grise <richgrise@example.net> wrote:
| Quote: | On Fri, 09 Dec 2005 22:27:45 +0000, Adam Stouffer wrote:
Anyone have a schematic for something to limit the volume from line
level sources? I hate watching a tv show or movie and then getting
blasted by a commercial at twice the volume.
What I'd like to find is something in the VBI stream that identifies
"Commercial", to make the VCR "pause" and skip the bloody things.
Then again, the advertisers do keep TV free, "the way God intended it
to be."[1] ;-)
Cheers!
Rich
[1] Dave Letterman
|
A VCR makes a very good limiter. I have tried this before. The internal
record holds the volume constant.
I have made automatic volume controls using op-amps
and a lamp-photoresistor combo. The photoresistor changes
the gain.
Terk makes a nice inexpensive unit for abot $30-$40.
It even has two frequency channels.
I find the devices very good for changing channels and
maintaining volume. I had too much of a problem though with the Hughes
surround sound system, where the volume changes as the surround
sound changes.
greg |
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