| Title: | * * Computer Music, MIDI, and Related Topics * * |
| Notice: | Conference has been write-locked. Use new version. |
| Moderator: | DYPSS1::SCHAFER |
| Created: | Thu Feb 20 1986 |
| Last Modified: | Mon Aug 29 1994 |
| Last Successful Update: | Fri Jun 06 1997 |
| Number of topics: | 2852 |
| Total number of notes: | 33157 |
When C.J. MOUTON signed in, he mentioned a vocal eliminator. I contacted
him for the plans and put this together from the info that he provided.
' Thought it would be a fitting topic for the COMMUSIC notesfile.
VOCAL ELIMINATOR (actually a center band eliminator)
THEORY:
This circuit will eliminate anything that is common to both the left
and right channels (ie:centered). Since the lead vocal is usually
centered, it is the usually the thing that is eliminated. Any signal
positioned between the left and right channels, but not panned fully to
one side will be attenuated proportional to its distance from the
center of the mix.
The reason the circuit works is because it contains op amps, otherwise
known as difference amplifiers. When both the left and right channels
are fed into an op amp, the only thing amplified is the *difference*
between the two channels. This means that a signal panned fully to the
right and not to the left will be amplified. A signal centered will
appear to be equal on both channels and will effectively filtered out.
In this circuit the OUTPUT L puts out the amplified signal formed from
the Left channel minus the right channel. The OUTPUT R outputs the
Right Channel minus the Left Channel. Consequently nothing is lost
except the signals common to both channels.
------------------------------------------------------------------------------
Parts:
qty item
1 - TL082 (from radio shack)
8 - 100K ohm resistors.
4 - 9V batteries or +- 15VDC source
4 - connectors (optional)
The pinout of the TL082 is very straightforward. Pin 1 is the output of the
first op-amp. Pin 2 is the minus input of op-amp 1. Pin 3 is the plus input
of op-amp 1. Pin 4 is the -15 volt input. Pin 5 is the plus input of op-amp
2. Pin 6 is the minus input of op-amp 2. Pin 7 is the output of op-amp 2.
Pin 8 is the +15 volt input.
Note: All resistors are 100K ohm
-15v
|
|4
LEFT CHANNEL 3 |\| OP2
___________.___NNN_______________|+\
V | | | \ 1 OUTPUT L
^-------- | Z | \_______.___________
| | Z 2 | / | V
___________|_._____|___NNN__.____|- / | ________^
V | | | | | | / / |
^_______. | | | | |/ / |
RIGHT | | | _____ | / |
CHANNEL | | | ___ |______NNN___/ _____
| | | _ ___
----- | | _
--- | |
- | | +15v
| | |
| | |8
| | 5 |\| OP2
| |_NNN_______________|+\
| | | \ 7 OUTPUT R
| Z | \_______.___________
| Z 6 | / | V
|_______|___NNN__.____|- / |
| | | / / --------^
| | |/ / |
| | / |
| |_____NNN____/ |
_____ -----
___ ---
_ -
IMPLEMENTATION:
By using 100K ohm resistors we can cross connect the two op amps in
such a way that the outputs become left-right and right-left. The
stereo separation is usually maintained with such an arrangement.
Pin 1 output is connected to pin 2 minus with a resistor. The same
between pins 6 and 7. Pin 2 is additionally attached to the right
channel input through another resistor. Pin 6 is connected through a
resistor to the left channel. Pin 3 is connected through a resistor to
the left channel input. Pin 3 is also connected through a resistor to
ground. So pin 3 is between 2 resistors, one going to the left channel,
the other from pin 3 to ground. Connect pin 5 through 2 more resistors
the same way as pin 3. You can use 4 batteries (9 volt size) connected
in series to obtain the proper voltage. The connection between the two
center batteries is ground.
to pin 8---+___- +___- GND +___- +___- to pin 4
And that's it!! Attach whatever connectors are necessary to the
LEFT channel and ground and the RIGHT channel and ground. Also add
connectors between the outputs and ground.
VARIATIONS:
By the way, for some unique variations on patches, you can separate the
resistors going to pins 2,3,5, and 6 with separate connectors. Since
the op-amp's real name is a difference amplifier, you can come up with
some pretty unique effects by sending 2 patches through this circuit,
or sending your voice in with a patch, and get the difference of the
two!!
Have fun.......let me know if it is useful....
C.J.
(editing and comments by Mark Hastings)
| T.R | Title | User | Personal Name | Date | Lines |
|---|---|---|---|---|---|
| 2281.1 | MILKWY::JANZEN | Noting is a privilege not a right | Tue Mar 06 1990 17:55 | 3 | |
There was a similar PAiA project years ago; I doubt it's still in their
catalogue.
Tom
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| 2281.2 | ACESMK::KUHN | vox et praeterea nihil | Tue Mar 06 1990 18:54 | 1 | |
how much to get one built? | |||||
| 2281.3 | cost estimate | KEYBDS::HASTINGS | Tue Mar 06 1990 19:50 | 6 | |
re: last
CJ says that it can be done for under $7. It'll probably be more if you
add connectors.
Mark
| |||||
| 2281.4 | ACESMK::KUHN | vox et praeterea nihil | Wed Mar 07 1990 14:20 | 2 | |
how much would it cost for someone to build it for me? if i tried
something like that i would blow up the house.
| |||||
| 2281.5 | worth trying..... | LEDDEV::ROSS | shiver me timbres.... | Wed Mar 07 1990 14:28 | 11 |
Use 1% resistors for best results....OR use trim pots instead
of resistors in the feedback path, and then set those for
same gain as the non-inverting sides (read: set for best elimination).
Since vocals usually have reverb, and reverb is a stereo, not
mono signal usually, this circuit wont remove it. (might get
some neat effects...)
ron
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| 2281.6 | don't spend a lot of moey, though | SWAV1::STEWART | As a matter of fact, it's all dark | Wed Mar 07 1990 14:34 | 14 |
It's real difficult to blow up anything with just a couple of batteries...add a fuse and some plastique though... These vocal eliminator things are sold commercially. Check out magazines related to music (Stereo Review, Electronic Musician, ???). In the back pages where the cheap ads live, you'll sometimes find a real small photo ad with a picture of a guy (who looks like Freddy Prinze before he died) singing. Sorry I don't have specific publication dates or issues for you. If you need somebody to put one of these together for you, you should probably post a note in the ELECTRONOTES (???) conference where all the circuit builders hang out. | |||||
| 2281.7 | Just take this little pill... | FSTVAX::MOUTON | Wed Mar 07 1990 14:58 | 31 | |
Hi Gang!!!
C.J. here....
Tried to find Mr/Mrs/Ms Kuhn in the ELF, but you don't have enough
info in your note to locate you.
I am building some for my friends here....for cost (and an optional cup
of coffee) I could build it for you.
Where are you? Your DTN?
How far from Boston, Mass, etc.
As far as the ad is concerned I checked the ad out ( a couple of years
ago ) and got a price list....
A complete setup would run over $500.00!!!!
The eliminator alone cost over $200.00!!!
And it was in MONO!!!!
I have a demo record they sent me around somewhere....
They also had a number you could call to hear an over the phone sample.
Send me mail at FSTVAX::MOUTON to help you.....
C>J>
c.j. (10 thumbs strikes again)
| |||||
| 2281.8 | yo | ACESMK::KUHN | vox et praeterea nihil | Wed Mar 07 1990 15:14 | 5 |
yo c.j.
i'm contacting you offline. 500 bucks??? i dont think all my
'equipment' is worth that! :-)
| |||||
| 2281.9 | It really works | ACESMK::KUHN | MKO2 - 264-1319 | Mon Mar 12 1990 17:00 | 8 |
I tried out the circuit over the weekend. All claims made are true. It
works as advertised. I also found that It removes some of the tape hiss
that gets created when i bounce tracks from deck to deck.
I didn't blow up the house,but when i plugged in the 4th 9V battery,
all the lights in the neighborhood dimmed. :-)
jay
| |||||
| 2281.10 | Hole In The Middle? | LUDWIG::RAPHAELSON | Tue Mar 13 1990 14:17 | 4 | |
What effect did seem to have other normally centered stuff, such
as kick drum or snare drum? Perhaps the real expensive commercial
unit includes some bandwidth selectivity to limit the effect to
certain frequency areas...............................Jon.........
| |||||
| 2281.11 | its center channel quad :-) | ACESMK::KUHN | MKO2 - 264-1319 | Tue Mar 13 1990 17:50 | 11 |
ANYTHING common to both channels is virtually removed. Maybe the
expensive models let you select bandwith but its not worth the price
for me. This circuit is fine for low-tech thrills.
A workaround is to have a Y output from your cd and mix in the other
(non vocal eliminator) source when there are no vocals.
I didn't really notice a hole in the music i was playing with (Procol
Harum Grand Hotel), but (of course) everything sounds different.
I like the effect on the stuff I do myself. I cant explain exactly
how its different...for 7 bucks worth of parts, its well worth it.
jay
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