Follow along with the video below to see how to install our site as a web app on your home screen.
Note: This feature may not be available in some browsers.
If you want real information, don't ask people in high places. Ask techs.I'm not sure that's right. My memory (which could be faulty) is that this
can be shown mathematically.
I'll ask around (I know a few people in high places) and see if I can get a
reference.
Wouldn't you get 4 kHz (2nd harmonic of 2kHz) rather than 3 kHz?If you put in a FS 1 KHz tone, you get out a nearly FS 1KHz tone, DC that is
46 dB down, and 2 KHz that is 46 dB down. Run the output back through again,
and you get a nearly FS 1 KHz tone, DC that is still about 46 dB down, a 2
KHz tone that is about 46 dB down, and a 3 KHz tone that is about 92 dB
down.
Oh, I reckon the latest fad, the single ended tube output satge (preferably withEeyore wrote:
The idea that you can 'get away' with sloppy circuitry for replay because the
source was in some way 'impaired' is totally false.
I don't think anybody proposed "sloppy" circuitry for replay. The point is
that studio audio gear is just solid, reliable, conventional good audio
stuff (none of that high-end low-oxygen power cord crap). Plenty of opamps,
plenty of NFB, plenty of digital processing, plenty of all the things that
high-enders loathe.
Since the recording studio already did 90% of the work of completely
destroying the audio signal beyond repair, it doesn't matter how much your
home audio gear adds to that.
Mr. Dorsey is being only slightly hyperbolic.It does, because a stage which is audibly blameless
by itself may turn into a sonic disaster when it appears
a few hundred times in the signal path.
** Huh ??
A few HUNDRED times ???????
The colossal fool must be on LSD.
If there were a Fifth Horseman, "Grundge", that would be the K1. It's soI do wish you'd glom onto a Crown K1. You really need to
hear this amplifier -- and run it through some blind tests.
What's the K1 like then ?
Something like The Second Coming?
No, more like something out of Revelations.
I think if you owned better equipment, your views of what constitute goodSometimes when I hear the golden earers talk I'm surprised
that I can make out any music at all when listening with my
Cantons fed from an old Sony amp through particularly
oxygen-rich cables.
And their qualifications for making a valid mathematical analysis wouldWilliam Sommerwerck wrote:
I'm not sure that's right. My memory (which could be faulty) is that this
can be shown mathematically.
I'll ask around (I know a few people in high places) and see if I can get
a reference.
If you want real information, don't ask people in high places. Ask techs.
Can't find a schematic for that one, but I'm looking at the schematic of a"Scott Dorsey wrote
It does, because a stage which is audibly blameless by itself may turn
into a sonic disaster when it appears a few hundred times in the signal
path.
The EQ section alone on a Neve V series (and derivatives) has 18 op-amp
stages.
You get both third and fourth. The 4th is another 46dB or so down, or aboutIf you put in a FS 1 KHz tone, you get out a nearly FS 1KHz tone, DC that
is
46 dB down, and 2 KHz that is 46 dB down. Run the output back through
again,
and you get a nearly FS 1 KHz tone, DC that is still about 46 dB down, a
2
KHz tone that is about 46 dB down, and a 3 KHz tone that is about 92 dB
down.
Wouldn't you get 4 kHz (2nd harmonic of 2kHz) rather than 3 kHz?
It all comes out if you do the math, which involves a few simple trigI tried my harmonic of the harmonic argument again. Sometimes it
works sometimes not.
Really? I see an article about sample-and-holds, and the like.Dammit, I've got that paper around here *someplace*.
The paper I'm referring to is by an English author, I think not Reg
Williamson and I think not Self, showing the generation of higher
harmonics
on the application of moderate amounts of feedback in a simple FET circuit
which produces only low-order harmonics without feedback. As the feedback
is
increased the high harmonics get smaller; they're at their worst in
low-feedback circuits. The measurements were real, not simulations.
Meanwhile, as I looked for that $%^$# article, I found this:
www.ucop.edu/research/micro/98_99/98_074.pdf
It's a theoretical discussion of the generation of higher-order IM
products
in feedback amps. The theory is supplemented by simulations, but
unfortunately not by real-world measurements, and the authors note that
their models are oversimplified.
Yes at a casual glance it looks much the same."Eeyore" wrote
"Scott Dorsey wrote
It does, because a stage which is audibly blameless by itself may turn
into a sonic disaster when it appears a few hundred times in the signal
path.
The EQ section alone on a Neve V series (and derivatives) has 18 op-amp
stages.
Can't find a schematic for that one, but I'm looking at the schematic of a
Neve 83022EQ which seems to be representative.
http://www.danalexanderaudio.com/neveinfo/83049/83022EQ.jpg
Depending on the cut and boost, the signal may be affected by all of them.There are a ton of op amps, but they aren't all cascaded on the signal path.
For example, 16 op amps are in 4 state-variable filters each composed of 4
stages, plus a helper amplifier.
In actual use, the full bandwidth and amplitude of the output signal of the
equalizer rarely if ever flows through all 16 op amps.
Where does this DC term come from ?"Robert Latest" <boblatest@yahoo.com> wrote in message
If you put in a FS 1 KHz tone, you get out a nearly FS 1KHz tone, DC that
is 46 dB down, and 2 KHz that is 46 dB down. Run the output back through
again, and you get a nearly FS 1 KHz tone, DC that is still about 46 dB
down, a
2 KHz tone that is about 46 dB down, and a 3 KHz tone that is about 92 dB
down.
Wouldn't you get 4 kHz (2nd harmonic of 2kHz) rather than 3 kHz?
You get both third and fourth. The 4th is another 46dB or so down, or about
138 dB down from the fundamental. I felt safe ignoring it. ;-)
I think that the third harmonic is actually due to the modulation of the DC
term from the first time through. The fourth harmonic is the second harmonic
of the second harmonic, of course.
Baxendall? in Wireless world magazine about 35 years ago.Dammit, I've got that paper around here *someplace*.
Meanwhile, can anyone help my blocked memory? Who the hell wrote that
paper?
Peace,
Paul
Pretty typical for a 4-section parametric eq, plus/minus some details.Arny Krueger wrote:
"Eeyore" wrote
"Scott Dorsey wrote
It does, because a stage which is audibly blameless by itself may
turn
into a sonic disaster when it appears a few hundred times in the
signal
path.
The EQ section alone on a Neve V series (and derivatives) has 18 op-amp
stages.
Can't find a schematic for that one, but I'm looking at the schematic of
a
Neve 83022EQ which seems to be representative.
http://www.danalexanderaudio.com/neveinfo/83049/83022EQ.jpg
Yes at a casual glance it looks much the same.
No doubt, but it is not the same as every ounce of signal going through allThere are a ton of op amps, but they aren't all cascaded on the signal
path.
For example, 16 op amps are in 4 state-variable filters each composed of
4
stages, plus a helper amplifier.
In actual use, the full bandwidth and amplitude of the output signal of
the
equalizer rarely if ever flows through all 16 op amps.
Depending on the cut and boost, the signal may be affected by all of them.
Pop the cover on an SSL 4000 some time..."MooseFET" <kensmith@rahul.net> wrote in message
news:1187669490.438547.314920@j4g2000prf.googlegroups.com...
It isn't hard to end up with that many. 1 per band per channel plus a
few will get you to 20 without working at it. To get above 100, you
are talking about a serious amount of more signal processing.
100 op amps on parallel channels is a far different situation than 100 *ALL
in series* with the signal.
Of course in the real world the situation is somewhere in between those
extremes.
A DC term is a natural consequence of a second order nonlinearity. Comes outArny Krueger wrote:
"Robert Latest" <boblatest@yahoo.com> wrote in message
If you put in a FS 1 KHz tone, you get out a nearly FS 1KHz tone, DC
that
is 46 dB down, and 2 KHz that is 46 dB down. Run the output back
through
again, and you get a nearly FS 1 KHz tone, DC that is still about 46
dB
down, a
2 KHz tone that is about 46 dB down, and a 3 KHz tone that is about 92
dB
down.
Wouldn't you get 4 kHz (2nd harmonic of 2kHz) rather than 3 kHz?
You get both third and fourth. The 4th is another 46dB or so down, or
about
138 dB down from the fundamental. I felt safe ignoring it. ;-)
I think that the third harmonic is actually due to the modulation of the
DC
term from the first time through. The fourth harmonic is the second
harmonic
of the second harmonic, of course.
Where does this DC term come from ?
Oh, it absolutely would. No question about it. That wouldn't have to do withI think if you owned better equipment, your views of what constitute good
and bad reproduction might change.
That tends to happen if you have a high amount of feedback at theMooseFET wrote:
On Aug 20, 6:13 pm, Mark <makol...@yahoo.com> wrote:
On Aug 20, 6:06 pm, Eeyore <rabbitsfriendsandrelati...@hotmail.com
wrote:
Mark wrote:
Eeyore wrote:
What is the case AIUI is that NFB can create 'new' (higher) harmonics that don't
exist with the open-loop situation. It's down to the maths of how feedback works.
And I am saying NFB CANNOT create new higher harmonics.
And it seems you are incorrect (at least when the amplifier having the feedback applied
has some non-linearity).
Graham
take something like crossover distortiuon for example...
No, I don't want crossover distortion.
How about thinking about a distortion that only adds, lets say the 2nd
harmonic to a sine wave. Think about what happens when that is
enclosed in a feedback loop. You take some of that second harmonic
from the output and feed it back into the input. The nonlinear
circuit takes the 2nd harmonic of the 2nd harmonic giving the forth
and sends that out the output. That forth comes back around and
around and around. A nonlinear cicrcuit that only made 2nd a harmonic
is now resulting in an infinite chain of frequencies.
in an open loop amp, crossover dist. creates lots of harmonics.
add neg feedback and they are all reduced. The high order ones are
not reduced AS MUCH as the low order ones, but they are certainly not
increased (assumming a proper design not on the verge of instability
and assuming the feedback componets themselves are linear, resistors
are usually linear for our purposes).
This is not correct. You have to have an extraordinarily large phase
margin to not have a boost in the harmonic near the gain crossover.
If G is the forward gain from the point where the distortion is made
to the output and H is the rest feedback the math looks like:
G /(1 + GH)
Here's the very ugly bit:
The distortion is often created in the output section making the G
part unity or nearly so. A stable servo loop can have a phase margin
of 30 degrees.
1/(1 + 1 * 1@(180-30)) = 1/(1 - 0.866 + j0.5)
= 1/(0.134 + j0.5)
Take ABS()
ABS(1/(0.134 + j0.5)) = 1/sqrt(0.134^2 + 0.5^2) = 1.93
Even though this amplifier is very stable, the feedback loop doubles
the amplitude of the harmonic near the gain crossover.
So for audio, put the gain crossover way out of band. Right?