we had extensive talks and posts about zobel networks ....there is one question that might sound silly but you never know
does it make any diference in a zobel network if the arengement is inductor and then capacitor and resistor to ground .....
will it make an change if its inductor resistor and capacitor to ground ?????
does it make any diference which of the parts of the zobel is first attached to ground either the resistor or the capacitor ????
can it work visa versa ????? i think yes but on the other hand there might be reasons i dont know
thanks
does it make any diference in a zobel network if the arengement is inductor and then capacitor and resistor to ground .....
will it make an change if its inductor resistor and capacitor to ground ?????
does it make any diference which of the parts of the zobel is first attached to ground either the resistor or the capacitor ????
can it work visa versa ????? i think yes but on the other hand there might be reasons i dont know
thanks
Does not make much difference,
if the output inductor comes before the Zobel or after.
And if the cap or resistor is next to ground does not matter, at all.
This is for sure!
-------
I have seen both ways to put inductor in many amplifiers.
Can be interesting, though, to see what a Professor in Electronics use.
As we all know,
a real Professor is always 10 times more right
than any www.diyaudio.com besserwisser
You do not become Professor in Electronics at
Georgia Institute of Technology
School of Electrical and Computer Engineering
only because some people are nice .... I think
http://users.ece.gatech.edu/~mleach/lowtim/output.html
http://users.ece.gatech.edu/~mleach/lowtim/
if the output inductor comes before the Zobel or after.
And if the cap or resistor is next to ground does not matter, at all.
This is for sure!
-------
I have seen both ways to put inductor in many amplifiers.
Can be interesting, though, to see what a Professor in Electronics use.
As we all know,
a real Professor is always 10 times more right
than any www.diyaudio.com besserwisser
You do not become Professor in Electronics at
Georgia Institute of Technology
School of Electrical and Computer Engineering
only because some people are nice .... I think
http://users.ece.gatech.edu/~mleach/lowtim/output.html
http://users.ece.gatech.edu/~mleach/lowtim/
This is Professor Leach comment to the bove output stage
of his amplifier.
One pratical thing with R50 C25 after the inductor
is that they can be put across the amplifier output terminals (Speaker OUT).
Leach have had bad experiences with putting these 2 components, The Zobel, on the PCB.
Zobel is an equalization filter for flatten the impedance curve for the LOAD.
This makes sense to me.
To put it more close the LOAD, than close to the amplifier feedback point.
of his amplifier.
One pratical thing with R50 C25 after the inductor
is that they can be put across the amplifier output terminals (Speaker OUT).
Leach have had bad experiences with putting these 2 components, The Zobel, on the PCB.
Zobel is an equalization filter for flatten the impedance curve for the LOAD.
This makes sense to me.
To put it more close the LOAD, than close to the amplifier feedback point.
One might question why Leach was allowing dirty Zobel currents to flow in signal leads.
Self has a completely opposite recommendation and one that I agree with, that the Zobel is to provide load and low impedance to pickup, at RF, to the output stage. Therefore it should be on the PCB as any inductance due to wires or traces will spoil it's effectiveness.
You should have dirty ground for the Zobel and decoupling capacitors and a clean ground for the signal and feedback network. These two should return to the power ground star by their own wire.
To answer Sakis, in a series connection it does not matter in which order components go. In accordance with the recommendation by Self, the Zobel should go before the output inductor, as the output inductor is to just protect against highly capacitive loads from crossovers and speaker cables.
Self has a completely opposite recommendation and one that I agree with, that the Zobel is to provide load and low impedance to pickup, at RF, to the output stage. Therefore it should be on the PCB as any inductance due to wires or traces will spoil it's effectiveness.
You should have dirty ground for the Zobel and decoupling capacitors and a clean ground for the signal and feedback network. These two should return to the power ground star by their own wire.
To answer Sakis, in a series connection it does not matter in which order components go. In accordance with the recommendation by Self, the Zobel should go before the output inductor, as the output inductor is to just protect against highly capacitive loads from crossovers and speaker cables.
You are very correct, Lineup , the Zobel/ inductor order is NOT
critical
Being a perfectionist, one has to consider that the zobel's true
function is to protect the amps output from too inductive
a reactance (loudspeaker). Knowing this, one could speculate
the best place for it is RIGHT at the output.
The output inductor's job is block the effect of capacitance
FROM the loudspeaker being introduced back to the amp.
Both effect's as mentioned above will affect the NFB loop and
cause various instabilities if left unchecked.
Another aspect of the zobel I found interesting is
where to "dump" the HF "garbage" that it filters out.
Most DIY designs I've seen couple the zobel right to the PC board
ground injecting this undesirable noise directly to the amp.
In my designs I keep the zobel network ground separate by connecting it directly to the main chassis star ground which
results in a much "cleaner" board/amp ground.
In commercial amps I've seen all 3 implementations .
(including my separated zobel scheme.)
Like in the prof. leach design, the extra damping resistor
in parallel with the output inductor reduces resonance
(ringing) at the output.
OS
critical
Being a perfectionist, one has to consider that the zobel's true
function is to protect the amps output from too inductive
a reactance (loudspeaker). Knowing this, one could speculate
the best place for it is RIGHT at the output.
The output inductor's job is block the effect of capacitance
FROM the loudspeaker being introduced back to the amp.
Both effect's as mentioned above will affect the NFB loop and
cause various instabilities if left unchecked.
Another aspect of the zobel I found interesting is
where to "dump" the HF "garbage" that it filters out.
Most DIY designs I've seen couple the zobel right to the PC board
ground injecting this undesirable noise directly to the amp.
In my designs I keep the zobel network ground separate by connecting it directly to the main chassis star ground which
results in a much "cleaner" board/amp ground.
In commercial amps I've seen all 3 implementations .
(including my separated zobel scheme.)
Like in the prof. leach design, the extra damping resistor
in parallel with the output inductor reduces resonance
(ringing) at the output.
OS
Any bypass capacitor and filter cap attached to ground
will inject Current spikes into GND.
Where is Smaller caps, often smaller current.
Big caps often big Currents.
AC signal currents can not just dissapear.
And ground rails are often transporting this to power supply.
Ground rails have some resistance, inductance.
No matter what geometry / size of copper.
Copper has got resistance per volume & length.
Current x [Resistance+Inductance] = Voltage.
What we have done is SCREWING UP the 0-Volt ZERO Reference.
And if 0 is +0.1
then follows that +2 is no longer 2
but +2.1.
All other values are dependent on ZERO Reference.
And if REF is changed, all other values are changed.
Make this experiment.
When working with Op-Amps, this can sometimes be an issue.
We use often two 100 nF very close to chip V+ V- pins.
Where we put the 'ground legs' of those 2 caps
can sometimes make a BIG difference.
This is why sometimes can be better to put only 1 capacitor.
From Opamp V+ pin to V- pin.
This way we avoid current injection at high frequency
into the GND.
My Lineup Bottomline:
.. There is nothing more important in one AC Amplifier
than to have a clean ZERO AC 0-volt Reference.
Star Grounding is one good way, to try to achieve this.
Note .. that ZERO DC Ref .. is not necessarily same as ZERO AC Ref.
Many times DC Ref is not abolute zero.
But AC Ref should always be as close to 0.000 Volt, as possible.
will inject Current spikes into GND.
Where is Smaller caps, often smaller current.
Big caps often big Currents.
AC signal currents can not just dissapear.
And ground rails are often transporting this to power supply.
Ground rails have some resistance, inductance.
No matter what geometry / size of copper.
Copper has got resistance per volume & length.
Current x [Resistance+Inductance] = Voltage.
What we have done is SCREWING UP the 0-Volt ZERO Reference.
And if 0 is +0.1
then follows that +2 is no longer 2
but +2.1.
All other values are dependent on ZERO Reference.
And if REF is changed, all other values are changed.
Make this experiment.
When working with Op-Amps, this can sometimes be an issue.
We use often two 100 nF very close to chip V+ V- pins.
Where we put the 'ground legs' of those 2 caps
can sometimes make a BIG difference.
This is why sometimes can be better to put only 1 capacitor.
From Opamp V+ pin to V- pin.
This way we avoid current injection at high frequency
into the GND.
My Lineup Bottomline:
.. There is nothing more important in one AC Amplifier
than to have a clean ZERO AC 0-volt Reference.
Star Grounding is one good way, to try to achieve this.
Note .. that ZERO DC Ref .. is not necessarily same as ZERO AC Ref.
Many times DC Ref is not abolute zero.
But AC Ref should always be as close to 0.000 Volt, as possible.
Best 0.0000v reference is a 12 FT. ground rod outside in damp
ground..
HA HA P.S. true statement...
I really did this ..."cheetah" HT system/amps have dedicated
20A breaker with its own ground rod.
ground..
An externally hosted image should be here but it was not working when we last tested it.
HA HA P.S. true statement...
I really did this ..."cheetah" HT system/amps have dedicated
20A breaker with its own ground rod.
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