[stv]

On the Mandolin Cafe website there was a discussion of the big PA
that
the Grateful Dead used for a while, with which they used dual mics for
the
vocals with one out of phase with the other.

After a while, one fellow wrote this:

"I have experimented with using two mics and a line out from the
effects loop of each to the input of the other with great results,
seemingly immune to feedback even when looking right at a speaker.
This idea is also now a breakthrough in MRI imaging and also has some
interesting possibilities for electricity harvesting. "

And followed up with this:

"i'm you can loop out from your aux outs to ins on your soundboard or
with a dual input mic pre amp. i'm using a pendulum sps-1 pre and a
mackie onyx board. maybe could use a single trs cord? "

He seems to be suggesting crossing channels on a preamp or mixing
board in order to phase cancel part of the signal...

Have any of you any idea what this guy is talking about? It seems
gibberish to me.
But just in case there's something in there, I thought I'd ask...

Thanks,

stv

[Richard Crowley]

"stv" wrote ...
On the Mandolin Cafe website there was a discussion of
the big PA that the Grateful Dead used for a while, with
which they used dual mics for the vocals with one out of
phase with the other.
.....
Have any of you any idea what this guy is talking about?

The Rolling Stones used home-made *differential, noise-
cancelling* microphones which they lashed up from two
regular microphones held together back-to-back with
duct~tape. The microphones were wired together out
of phase and the "front" mic was close-talked so that
only the front mic heard the desired sound and the
back mic cancelled (more-or-less) the ambient sound
(i.e. the noise from the "wall of sound" speakers which
were stacked up *behind* the performers.

AFAIK, the mics were wired together with a reverse-
polarity "Y-cable" and sent only one XLR cable to the
mic preamp. There are likely various ways of doing the
reverse-polarity cancelling trick on various mixers but
that would depend on what was available on a particular
mixer.

It seems gibberish to me. But just in case there's
something in there, I thought I'd ask...

The part about MRI imaging and "electricity harvesting"
sound more like long-term brain deterioration from
drug abuse. :-)

[Scott Dorsey]

stv wrote:
On the Mandolin Cafe website there was a discussion of the big PA
that
the Grateful Dead used for a while, with which they used dual mics for
the
vocals with one out of phase with the other.

After a while, one fellow wrote this:

"I have experimented with using two mics and a line out from the
effects loop of each to the input of the other with great results,
seemingly immune to feedback even when looking right at a speaker.
This idea is also now a breakthrough in MRI imaging and also has some
interesting possibilities for electricity harvesting. "

And followed up with this:

"i'm you can loop out from your aux outs to ins on your soundboard or
with a dual input mic pre amp. i'm using a pendulum sps-1 pre and a
mackie onyx board. maybe could use a single trs cord? "

He seems to be suggesting crossing channels on a preamp or mixing
board in order to phase cancel part of the signal...

Have any of you any idea what this guy is talking about? It seems
gibberish to me.
But just in case there's something in there, I thought I'd ask...

The Wall of Sound used two omni microphones mounted on top of one another
driving a differential input.

In the far field, everything cancelled. A vocalist would sing into one
of the two microphones and because they were louder in one than the other,
the difference signal would have the vocal in it.

There was massive comb filtering and it sounded like the vocals were coming
through a telephone, but aside from that it was great.

Get some archive recordings of some of the Wall of Sound concerts. It was
an interesting idea, and it was better than many of the alternatives back
in that era.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Earl Kiosterud]

We did that back in the 70's using pairs of EV 545 mics, one below the other. It worked
very well to get rid of the uneven response you get as you approach feedback in those small
clubs, which causes a lot of regenerative comb-filter irregularities in the overall
response. When a cancel mic was brought in, the sound got noticeably cleaner. We still
couldn't always get the acoustic gain real high because it can increase very high-frequency
feedback. At those short wavelengths, the mics aren't always out of phase. We never got
around to adding a low-pass filter to each cancel mic, but it'd be worth a try.
--
Regards from Virginia Beach,

Earl Kiosterud

"stv" wrote in message
...
On the Mandolin Cafe website there was a discussion of the big PA
that
the Grateful Dead used for a while, with which they used dual mics for
the
vocals with one out of phase with the other.

After a while, one fellow wrote this:

"I have experimented with using two mics and a line out from the
effects loop of each to the input of the other with great results,
seemingly immune to feedback even when looking right at a speaker.
This idea is also now a breakthrough in MRI imaging and also has some
interesting possibilities for electricity harvesting. "

And followed up with this:

"i'm you can loop out from your aux outs to ins on your soundboard or
with a dual input mic pre amp. i'm using a pendulum sps-1 pre and a
mackie onyx board. maybe could use a single trs cord? "

He seems to be suggesting crossing channels on a preamp or mixing
board in order to phase cancel part of the signal...

Have any of you any idea what this guy is talking about? It seems
gibberish to me.
But just in case there's something in there, I thought I'd ask...

Thanks,

stv

[stv]

On Mar 25, 3:42*pm, (Scott Dorsey) wrote:
stv wrote:
On the Mandolin Cafe website there was a discussion of the big PA
that
the Grateful Dead used for a while, with which they used dual mics for
the
vocals with one out of phase with the other.

After a while, one fellow wrote this:

"I have experimented with using two mics and a line out from the
effects loop of each to the input of the other with great results,
seemingly immune to feedback even when looking right at a speaker.
This idea is also now a breakthrough in MRI imaging and also has some
interesting possibilities for electricity harvesting. "

And followed up with this:

"i'm you can loop out from your aux outs to ins on your soundboard or
with a dual input mic pre amp. i'm using a pendulum sps-1 pre and a
mackie onyx board. maybe could use a single trs cord? "

He seems to be suggesting crossing channels on a preamp or mixing
board in order to phase cancel part of the signal...

Have any of you any idea what this guy is talking about? *It seems
gibberish to me.
But just in case there's something in there, I thought I'd ask...

The Wall of Sound used two omni microphones mounted on top of one another
driving a differential input.

In the far field, everything cancelled. *A vocalist would sing into one
of the two microphones and because they were louder in one than the other,
the difference signal would have the vocal in it.

There was massive comb filtering and it sounded like the vocals were coming
through a telephone, but aside from that it was great.

Get some archive recordings of some of the Wall of Sound concerts. *It was
an interesting idea, and it was better than many of the alternatives back
in that era.
--scott
--
"C'est un Nagra. *C'est suisse, et tres, tres precis."

Hey Scott, et al,

I've heard that stuff and read a good deal about the Wall. It's not
that part of
this guy's thing that I don't understand. (I guess I should have left
out more
of the contextual stuff...) The Wall bit is the McGuffin (to pull
from Hitchcock)
and the quoted parts are the plot. ;-)

It's the bits in the quotes that have left me scratching my head.

Is there anything at all that you (all) can make of that stuff?

Sorry for the confusion.

Thanks,

stv

[Richard Crowley]

"stv" wrote ...
It's the bits in the quotes that have left me scratching my head.
Is there anything at all that you (all) can make of that stuff?

You put quite a lot inside the quotes.

So mixing two mics out of phase is not a big deal
and can be done several ways depending on what
you have to work with. Is THAT what you are
asking about?

"seemingly immune to feedback even when looking
right at a speaker" doesn't seem credible to me.
Is THAT what you are asking about?

"breakthrough MRI imaging" and "electricity harvesting"
are just goofy. Is THAT what you are asking about?

Sorry for the confusion.

Still confused. Maybe you should ask specific questions.

[Scott Dorsey]

stv wrote:
I've heard that stuff and read a good deal about the Wall. It's not
that part of
this guy's thing that I don't understand. (I guess I should have left
out more
of the contextual stuff...) The Wall bit is the McGuffin (to pull
from Hitchcock)
and the quoted parts are the plot. ;-)

It's the bits in the quotes that have left me scratching my head.

Is there anything at all that you (all) can make of that stuff?

I think it's drugs.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Paul Stamler]

"stv" wrote in message
...

"I have experimented with using two mics and a line out from the
effects loop of each to the input of the other with great results,
seemingly immune to feedback even when looking right at a speaker.
This idea is also now a breakthrough in MRI imaging and also has some
interesting possibilities for electricity harvesting. "

And followed up with this:

"i'm you can loop out from your aux outs to ins on your soundboard or
with a dual input mic pre amp. i'm using a pendulum sps-1 pre and a
mackie onyx board. maybe could use a single trs cord? "

He seems to be suggesting crossing channels on a preamp or mixing
board in order to phase cancel part of the signal...

Have any of you any idea what this guy is talking about?

He's harvesting electricity. I woudn't concern yourself about it if I were
you.

When he catches some, then pay attention.

Peace,
Paul

[Federico]

"Scott Dorsey" wrote:
"There was massive comb filtering and it sounded like the vocals were coming
through a telephone, but aside from that it was great."

This sound like a Woody Allen sentence... Great Scott!!!!
F.

[david gourley]

(Scott Dorsey) put forth the notion in...news:fsc07s$2sl
:

stv wrote:
I've heard that stuff and read a good deal about the Wall. It's not
that part of
this guy's thing that I don't understand. (I guess I should have left
out more
of the contextual stuff...) The Wall bit is the McGuffin (to pull
from Hitchcock)
and the quoted parts are the plot. ;-)

It's the bits in the quotes that have left me scratching my head.

Is there anything at all that you (all) can make of that stuff?

I think it's drugs.
--scott


Well, Owsley was the one with the idea, so go figure.

david

[stv]

On Mar 25, 6:17*pm, "Richard Crowley" wrote:

Still confused. *Maybe you should ask specific questions.

OK, here's what I'm most mystified by:

"I have experimented with using two mics and a line out from the
effects loop of each to the input of the other with great results...
seemingly immune to feedback even when looking right at a speaker. "

"i'm you can loop out from your aux outs to ins on your soundboard or
with a dual input mic pre amp. i'm using a pendulum sps-1 pre and a
mackie onyx board. maybe could use a single trs cord? "

Effects loop phase adjustments? Aux outs to ins?

Seems like gibberish to me, but I'm not the sharpest tool in the
shed...

The MRI and "harvesting" bits I can write off.... ;-)

Thanks,

stv

[Richard Crowley]

"stv" wrote ...
"Richard Crowley" wrote:
Still confused. Maybe you should ask specific questions.

OK, here's what I'm most mystified by:

"I have experimented with using two mics and a line out from the
effects loop of each to the input of the other with great results...
seemingly immune to feedback even when looking right at a speaker. "

"i'm you can loop out from your aux outs to ins on your soundboard or
with a dual input mic pre amp. i'm using a pendulum sps-1 pre and a
mackie onyx board. maybe could use a single trs cord? "

Effects loop phase adjustments? Aux outs to ins?

Seems like gibberish to me, but I'm not the sharpest tool in the
shed...

Just some theoretical methods of achieving opposite polarity
("phase") for implementing the cancellation trick. Dunno how
one can do polarity reversal with single-ended signals (as out
of your typical effects loop), but this guy knows how to harvest
electricity, so maybe you should ask him.

I'd write it off as gibberish if I were you. Get on with your
life and study something rewarding.

[stv]

So... I asked this guy for some details and here was the latest
response:

" The pre-amp for electricity harvest is essentially the same design
as those used for audio applications. Understanding this may be of
interest for anyone desiring to modify or make a pre=amp for phase
canceled signaling.

"An electromagnetic or piezo-electric signal is first poled, then
oriented through a diode (one way current) and buffered to match ohm
ratings (think high or low Z) with a rheostat. This is a feature
sorely lacking in most systems. Martin Taylor uses this when blending
any of three pickup/mic signal combinations on his guitar.

"Anyway, if you're still with me, the "phase canceling" occurs when
signals which have carefully matched ohm ratings are aligned, in
phase. Just like the familiar problem of a mic hearing itself from the
speaker and feed-back, except in this example the identical
characteristics of the two or more perfectly matched signals create a
"standing wave" and disappear. A unit like a digital feedback
eliminator works constantly calculating a root/mean/square (RMS)
equation throughout the harmonic range while summing signals,
canceling as it works. Then of course amplification and/or power
inversion. A phase inverter switch on your soundboard simply changes
the direction of signal travel along either two wires, the third being
a ground.

"I never thought you were slow to understand before. Usually quick
with valuable experience to share. Thanks for that.
here's a pick of my pre=amp. The "inserts" are TRS. So, channel out
jack each side to insert of the other, each direction. A single TRS
patch cord would likely work even better, But I don't have one yet.
The Pendulum SPS-1 has exactly matched ohm signals... "

And he posted a picture of the back of a Pendulum SPS-1.

I don't get it. One more time, please? Is there -anything- to this
(harvesting excepted, never mind that...) ?

Thank you,

stv

[Chris Hornbeck]

On Sat, 29 Mar 2008 19:50:00 -0700 (PDT), stv
wrote:

So... I asked this guy for some details and here was the latest
response:

massive BS excerpted

And he posted a picture of the back of a Pendulum SPS-1.

I don't get it. One more time, please? Is there -anything- to this
(harvesting excepted, never mind that...) ?

Thanks. That was truly hilarious.

Much thanks,

Chris Hornbeck
"Hollywood goddess's rodent-racing facilities"
WS's puzzle - no, not that WS; *our* WS!

[Richard Crowley]

"stv" wrote ...
I don't get it. One more time, please? Is there -anything-
to this (harvesting excepted, never mind that...) ?

It is gibberish from the first word to the last.
Dunno whether the guy is insane or is trying to pull
your chain? Either way, that is quite enough for this
newsgroup. If you want to carry on a discussion(?)
with this guy, do it elsewhere.

[hank alrich]

stv wrote:

" The pre-amp for electricity harvest

snipitty doo dah

Oh, my goodness, wait until the Prius people hear about this!!

Nobody's heard from McQuilken in a while...

snipitty yay

--
ha
Iraq is Arabic for Vietnam

[Paul Stamler]

"stv" wrote in message
...

I don't get it. One more time, please? Is there -anything- to this
(harvesting excepted, never mind that...) ?

Reading through the bafflegab, it sounds like he's discovered that his
preamp or board (or something) has signals of opposite polarities available
via different outputs, and he's combining them to do, well, something or
other.

Peace,
Paul

[Scott Dorsey]

Richard Crowley wrote:
"stv" wrote ...
I don't get it. One more time, please? Is there -anything-
to this (harvesting excepted, never mind that...) ?

It is gibberish from the first word to the last.
Dunno whether the guy is insane or is trying to pull
your chain? Either way, that is quite enough for this
newsgroup. If you want to carry on a discussion(?)
with this guy, do it elsewhere.

I reiterate: it's drugs.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[stv]

Here's the whole thread:

http://www.mandolincafe.net/cgi-bin/...8;t=51851;st=0

The first mention of phase cancellation thru effects loops is on March
24.

Enjoy. I think it's better in the original...

stv