[[email protected]]

I've heard of reverse gain as an indicator of gain through a device
connected "backwards", i.e. a signal is applied at the output pin of
an op amp, and measured at the input pin, gain being measured-at-input
divided by applied-at-output.

But in the context of pro audio, specifically, microphones connected
to mixers in a pro audio (live or recording) situation, what does
"reverse gain structure" mean?

[Eeyore]

wrote:

I've heard of reverse gain as an indicator of gain through a device
connected "backwards", i.e. a signal is applied at the output pin of
an op amp, and measured at the input pin, gain being measured-at-input
divided by applied-at-output.

I doubt you'd get very much with modern circuitry !


But in the context of pro audio, specifically, microphones connected
to mixers in a pro audio (live or recording) situation, what does
"reverse gain structure" mean?

Nothing.

Graham

[William Sommerwerck]

"But _this_ amplifier goes below 0."

[Eeyore]

William Sommerwerck wrote:

"But _this_ amplifier goes below 0."

Might it also require signal inversion ?

Graham

[Richard Crowley]

"Eeyore" wrote ...


William Sommerwerck wrote:

"But _this_ amplifier goes below 0."

Might it also require signal inversion ?


I remember an article in an April edition of "Popular Electronics"
back in the late 1950s or early 1960s. It was a special April-Fools
feature about "negative AC".

They trumped up some impresive-looking formulae to show that
if you took the - path of some +/- factor, you could create this
"inverse power".

They printed two photos demonstrating this power...
1. A soldering iron with ice-cicles hanging off the tip.
2. A gooseneck lamp with a cone of "black" coming
out of the shade where the bulb had sucked up all the
available light in the path.
I wish I had kept the photos.

[William Sommerwerck]

I remember an article in an April edition of "Popular Electronics"
back in the late 1950s or early 1960s. It was a special April-Fools
feature about "negative AC".

It was more likely Radio-Electronics. Regardless, I'd like to see the
article, too.

[Mike Rivers]

wrote:
I've heard of reverse gain as an indicator of gain through a device
connected "backwards",

I haven't. Geez, where do we get these ideas? Must be a web site
somewhere.

--
If you e-mail me and it bounces, use your secret decoder ring and reach
me he
double-m-eleven-double-zero at yahoo -- I'm really Mike Rivers
)

[Mike Rivers]

Richard Crowley wrote:

I remember an article in an April edition of "Popular Electronics"
back in the late 1950s or early 1960s. It was a special April-Fools
feature about "negative AC".

They printed two photos demonstrating this power...
1. A soldering iron with ice-cicles hanging off the tip.
2. A gooseneck lamp with a cone of "black" coming
out of the shade where the bulb had sucked up all the
available light in the path.

I remember that from QST. The article was entitled "Contra Polar Energy."


--
If you e-mail me and it bounces, use your secret decoder ring and reach
me he
double-m-eleven-double-zero at yahoo -- I'm really Mike Rivers
)

[Mark]

I've heard of reverse gain as an indicator of gain through a device
connected "backwards",



in RF circuits you have forward gain S21 and reverse gain S12 also
called reverse isolation. If an RF amplifers' reverse isolation
apporaches it's forward gain, it is in danger of oscillation. These
and other S paramters are measured with a network analyzer.

I have never heard of the term reverse gain used in audio work.

Maybe it could mean in a PA the gain (or loss) from the speaker back
to the mic as an indicator of the possibility of feedback oscillation
or maybe you meant RESERVE gain.

Mark

[Tim Perry]

"Mark" wrote in message
...

I've heard of reverse gain as an indicator of gain through a device
connected "backwards",



in RF circuits you have forward gain S21 and reverse gain S12 also
called reverse isolation. If an RF amplifers' reverse isolation
apporaches it's forward gain, it is in danger of oscillation. These
and other S paramters are measured with a network analyzer.

I have never heard of the term reverse gain used in audio work.

Maybe it could mean in a PA the gain (or loss) from the speaker back
to the mic as an indicator of the possibility of feedback oscillation
or maybe you meant RESERVE gain.

Mark


see bi-directional amplifiers
http://www.impactacoustics.com/produ...1008&sku=41033

in audio perhaps, reverse log attenuator: a pot that attenuates
logarithmically as the pot is turned clockwise.

excerpt from wikki: There is also an anti-log pot or reverse audio taper
which is simply the reverse of a log pot. It is almost always used in a
ganged configuration with a log pot, for instance, in an audio balance
control.

[bg]

Richard Crowley wrote in message ...
"Eeyore" wrote ...


William Sommerwerck wrote:

"But _this_ amplifier goes below 0."

Might it also require signal inversion ?


I remember an article in an April edition of "Popular Electronics"
back in the late 1950s or early 1960s. It was a special April-Fools
feature about "negative AC".

And the power company has the nerve to charge you for the electrons that
enter your house but then they suck em back out again??

[Eeyore]

Tim Perry wrote:

"Mark" wrote

I've heard of reverse gain as an indicator of gain through a device
connected "backwards",

in RF circuits you have forward gain S21 and reverse gain S12 also
called reverse isolation. If an RF amplifers' reverse isolation
apporaches it's forward gain, it is in danger of oscillation. These
and other S paramters are measured with a network analyzer.

I have never heard of the term reverse gain used in audio work.

Maybe it could mean in a PA the gain (or loss) from the speaker back
to the mic as an indicator of the possibility of feedback oscillation
or maybe you meant RESERVE gain.

see bi-directional amplifiers
http://www.impactacoustics.com/produ...1008&sku=41033

in audio perhaps, reverse log attenuator: a pot that attenuates
logarithmically as the pot is turned clockwise.

excerpt from wikki: There is also an anti-log pot or reverse audio taper
which is simply the reverse of a log pot. It is almost always used in a
ganged configuration with a log pot, for instance, in an audio balance
control.

Or pan control or in a balanced mic amp gain stage (inter-emitter resistor).

Incidentally, did you know that 'log' and 'anti-log' controls are named the
wrong way round w.r.t. clockwise rotation ? Think about it.

Graham

[Adrian Tuddenham[_2_]]

wrote:

I've heard of reverse gain as an indicator of gain through a device
connected "backwards", i.e. a signal is applied at the output pin of
an op amp, and measured at the input pin, gain being measured-at-input
divided by applied-at-output.

But in the context of pro audio, specifically, microphones connected
to mixers in a pro audio (live or recording) situation, what does
"reverse gain structure" mean?

There were (possibly still are) bi-directional 'repeaters' used on long
telephone lines. The device was inserted into a standard impedance
transmission line (usually of 600-ohms characteristic impedance) and was
coupled into the line with a pair of 'hybrid' transformers.

Between the transformer circuits were two amplifiers, one facing in each
direction. The hybrid transformer was part of a bridge circuit which
balanced the real line against a 'dummy line' made up of resistors and
capacitors. When the hybrid was correctly nulled, the output of each
amplifier was prevented from appearing in the input signal of the other,
but each amplifier could see signals arriving from its own line.

Thus gain in each direction was possible and, if one direction was
regarded as 'forward', the gain in the opposite direction was 'reverse
gain'.

I doubt if this has any practical application to modern systems and
equipment - at least, not at audio frequencies.

--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

[William Sommerwerck]

I've heard of reverse gain as an indicator of gain through a device
connected "backwards",

I haven't. Geez, where do we get these ideas? Must be a web site
somewhere.

Actually, one of the hybrid (h) parameters for junction transistors is the
reverse voltage gain through the device. This does not apply, of course, to
amplifier circuits.

[[email protected]]

On Dec 5, 8:45*pm, Mark wrote:
I've heard of reverse gain as an indicator of gain through a device
connected "backwards",

in RF circuits you have forward gain S21 and reverse gain S12 also
called reverse isolation. * If an RF amplifers' reverse isolation
apporaches it's forward gain, it is in danger of oscillation. *These
and other S paramters are measured with a network analyzer.

Yeah, that's how I've seen the term used. It's a pretty
well-established term in some kinds of RF work, although
not particulary common. Very low reverse gain is, of course,
desirable, like -60dB or better (lower). If a device is properly
designed, the number should be so low that it's never an
issue, sort of like crosstalk.

I have never heard of the term reverse gain used in audio work.

Neither had I, until recently. The person who's using the
term seems to be using as a strange way of saying that
certain microphones provide a hotter than usual signal level,
so you should turn the mic input trims down on the mixer
(as compared to the trim settings more commonly used
with other microphones).

That's a pretty elementary concept: with a hotter mic signal
level, back off the input trim. It's a typical part of setting up
the gain structure in a pro audio system; by adusting the
input trims. But the term "reverse gain structure" seems a
strange way of describing it, and I had never heard it until
recently. If it were me, I'd say something like, "these mics
provide a pretty hot signal level, so you might want to back
off the input trims." Yeah, it's related to gain structure, but
I don't get where the "reverse" comes from.

I suspect it's some kind of marketing mumbo-jumbo, but
I thought I'd ask if anyone had ever heard the term.

-- Warped

[Tim Perry]

Incidentally, did you know that 'log' and 'anti-log' controls are named
the
wrong way round w.r.t. clockwise rotation ? Think about it.

Graham


I don't wanna. it hurts my brain. Is a man walking to the loo in the back
of an airplane moving backwards?

How about this one: some amplifiers have sufficient negative feedback so
that one could put a signal one the output and measure it on the input.

[Arny Krueger]

"Tim Perry" wrote in
message

Incidentally, did you know that 'log' and 'anti-log'
controls are named the wrong way round w.r.t. clockwise
rotation ? Think about it.

Thinking trigonometrically, potentiometers are really exponential, which is
the same as the anti-log.

How about this one: some amplifiers have sufficient
negative feedback so that one could put a signal one the
output and measure it on the input.

That speaks to a lack of isolation of the input from the output. We expect
that in audio amps, just like we don't expect impedance matching.

If you think of an amp in terms of an impedance matrix, we expect that the
element that describes the influence of the output on the input, is
infinite. If as an admittance matrix, then zero.

[Eeyore]

wrote:

On Dec 5, 8:45 pm, Mark wrote:
I've heard of reverse gain as an indicator of gain through a device
connected "backwards",

in RF circuits you have forward gain S21 and reverse gain S12 also
called reverse isolation. If an RF amplifers' reverse isolation
apporaches it's forward gain, it is in danger of oscillation. These
and other S paramters are measured with a network analyzer.

Yeah, that's how I've seen the term used. It's a pretty
well-established term in some kinds of RF work, although
not particulary common. Very low reverse gain is, of course,
desirable, like -60dB or better (lower). If a device is properly
designed, the number should be so low that it's never an
issue, sort of like crosstalk.

I have never heard of the term reverse gain used in audio work.

Neither had I, until recently. The person who's using the
term seems to be using as a strange way of saying that
certain microphones provide a hotter than usual signal level,
so you should turn the mic input trims down on the mixer
(as compared to the trim settings more commonly used
with other microphones).

That's a pretty elementary concept: with a hotter mic signal
level, back off the input trim. It's a typical part of setting up
the gain structure in a pro audio system; by adusting the
input trims. But the term "reverse gain structure" seems a
strange way of describing it, and I had never heard it until
recently. If it were me, I'd say something like, "these mics
provide a pretty hot signal level, so you might want to back
off the input trims." Yeah, it's related to gain structure, but
I don't get where the "reverse" comes from.

Nowhere. It's complete nonsense.

Graham

[Eeyore]

Tim Perry wrote:

Incidentally, did you know that 'log' and 'anti-log' controls are named
the wrong way round w.r.t. clockwise rotation ? Think about it.

Graham

I don't wanna. it hurts my brain. Is a man walking to the loo in the back
of an airplane moving backwards?

How about this one: some amplifiers have sufficient negative feedback so
that one could put a signal one the output and measure it on the input.

Possibly you mean insufficient NFB ?

Graham

[philicorda[_6_]]

On Fri, 05 Dec 2008 13:46:40 -0800, timewarp2008 wrote:

I've heard of reverse gain as an indicator of gain through a device
connected "backwards", i.e. a signal is applied at the output pin of an
op amp, and measured at the input pin, gain being measured-at-input
divided by applied-at-output.

But in the context of pro audio, specifically, microphones connected to
mixers in a pro audio (live or recording) situation, what does "reverse
gain structure" mean?

I plugged an old spring reverb rack in the other day.

For some reason, it inverts the phase of the direct signal going through
it, and there is no setting that is totally wet.

So, when you turn up the reverb aux send on a track, the track gets
quieter as the reverb gets louder! It works like a reverse gain control.

It's actually quite an intuitive way to use reverb, and there is no sign
of modification inside the rack, so I thought it might be wired that way
intentionally.

[Scott Dorsey]

In article ,
wrote:
I've heard of reverse gain as an indicator of gain through a device
connected "backwards", i.e. a signal is applied at the output pin of
an op amp, and measured at the input pin, gain being measured-at-input
divided by applied-at-output.

But in the context of pro audio, specifically, microphones connected
to mixers in a pro audio (live or recording) situation, what does
"reverse gain structure" mean?

I bet a nickel that it means the _gain structure_ is reversed. That is,
reverse modifies structure and not gain.
--scott

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

[Mike Rivers]

wrote:

The person who's using the
term seems to be using as a strange way of saying that
certain microphones provide a hotter than usual signal level,
so you should turn the mic input trims down on the mixer
(as compared to the trim settings more commonly used
with other microphones).

Oh! Is THAT what it's about? Must be one of those people who complain
that "the mixer is of poor quality becuase the gain has to be turned up
above 7 in order to get a good sound." g


--
If you e-mail me and it bounces, use your secret decoder ring and reach
me he
double-m-eleven-double-zero at yahoo -- I'm really Mike Rivers
)

[[email protected]]

On Dec 6, 5:35*pm, (Scott Dorsey) wrote:
In article ,

wrote:
I've heard of reverse gain as an indicator of gain through a device
connected "backwards", i.e. a signal is applied at the output pin of
an op amp, and measured at the input pin, gain being measured-at-input
divided by applied-at-output.

But in the context of pro audio, specifically, microphones connected
to mixers in a pro audio (live or recording) situation, what does
"reverse gain structure" mean?

I bet a nickel that it means the _gain structure_ is reversed. *That is,
reverse modifies structure and not gain.
--scott

So, in this case (hotter microphone output, thus less gain
on the input trim), what would be "reversed" about the gain
structure?


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

[Chris Hornbeck]

On Sat, 6 Dec 2008 15:12:49 -0800 (PST), wrote:

On Dec 6, 5:35*pm, (Scott Dorsey) wrote:
In article ,

But in the context of pro audio, specifically, microphones connected
to mixers in a pro audio (live or recording) situation, what does
"reverse gain structure" mean?

I bet a nickel that it means the _gain structure_ is reversed. *That is,
reverse modifies structure and not gain.
--scott

So, in this case (hotter microphone output, thus less gain
on the input trim), what would be "reversed" about the gain
structure?

Sound in the room is being lowered. It's a tricky thing to do
well.


All the best fortune,
Chris Hornbeck

[[email protected]]

So, in this case (hotter microphone output, thus less gain
on the input trim), what would be "reversed" about the gain
structure?

Sound in the room is being lowered.

No. Compared to other microphones, the electrical
signal level is higher at the mixer's XLR input. After
the input trim stage, the signal is about the same
with either microphone. The sound in the room, both
at the microphone, and in the listening area, is the
same level with either microphone.

Regardless of that, nothing seems "reversed."
The gain structure is a bit different in one section
of the signal path, but nothing is reversed.

It's a tricky thing to do well.

Reducing the gain at the input is not tricky at all;
it's a simple and straightforward task for anyone
famililar with the use of microphones and mixers.

All the best fortune,
Chris Hornbeck

[Eeyore]

wrote:

On Dec 6, 5:35 pm, (Scott Dorsey) wrote:
In article ,

wrote:
I've heard of reverse gain as an indicator of gain through a device
connected "backwards", i.e. a signal is applied at the output pin of
an op amp, and measured at the input pin, gain being measured-at-input
divided by applied-at-output.

But in the context of pro audio, specifically, microphones connected
to mixers in a pro audio (live or recording) situation, what does
"reverse gain structure" mean?

I bet a nickel that it means the _gain structure_ is reversed. That is,
reverse modifies structure and not gain.
--scott

So, in this case (hotter microphone output, thus less gain
on the input trim), what would be "reversed" about the gain
structure?

NOTHING.

You're an IDIOT.

[Eeyore]

wrote:

So, in this case (hotter microphone output, thus less gain
on the input trim), what would be "reversed" about the gain
structure?

Sound in the room is being lowered.

No. Compared to other microphones, the electrical
signal level is higher at the mixer's XLR input.

So ****ing what ?

That's why we have variable gain input amps.

Now go to hell and die for asking MORONIC questions.

[Scott Dorsey]

wrote:
I bet a nickel that it means the _gain structure_ is reversed. =A0That is=
,
reverse modifies structure and not gain.

So, in this case (hotter microphone output, thus less gain
on the input trim), what would be "reversed" about the gain
structure?

Not much. I mean, there's less gain at the front of the chain in order
to maintain the same amount of headroom, but it's not as if there is more
gain at the other end. I wouldn't call that reversed. In fact, the real
system gain structure hasn't changed much, it's just that there is more
gain in the mike and less in the preamp.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."