When referring to amplifiers the favorite catch-phrase of audiophiles
seems to be "clean power". As an ignorant novice I would like to know
what is meant by "clean power" and how do I achieve it. Also, I once
heard something about voltage matching an amplifier with a head unit
but if I set my amp to 4v (same as the preouts on my head unit) I can
barely hear my subs. Do I need to add a bigger amp to get the benefit
of voltage matching? Will this theoretically provide "cleaner power"?

I think 'clean power' would be more of a product of a high quality amp, not
so much from an install. In other words, an amp that amplifies the signal
without a lot of distortion and extra crap. Zapco and Xtant are good
examples of ultra clean amplifiers.


"Dylan X" wrote in message
m...
When referring to amplifiers the favorite catch-phrase of audiophiles
seems to be "clean power". As an ignorant novice I would like to know
what is meant by "clean power" and how do I achieve it. Also, I once
heard something about voltage matching an amplifier with a head unit
but if I set my amp to 4v (same as the preouts on my head unit) I can
barely hear my subs. Do I need to add a bigger amp to get the benefit
of voltage matching? Will this theoretically provide "cleaner power"?

I think 'clean power' would be more of a product of a high quality amp,
not
so much from an install. In other words, an amp that amplifies the signal
without a lot of distortion and extra crap. Zapco and Xtant are good
examples of ultra clean amplifiers.

Doesn't matter who makes it. All amplifiers made these days have distortion
byproducts well below audible threshold. Especially compared to the
distortion that arises from driving your amp into clipping, which is
surprisingly common.

"Mark Zarella" wrote in message
...
I think 'clean power' would be more of a product of a high quality amp,
not
so much from an install. In other words, an amp that amplifies the
signal
without a lot of distortion and extra crap. Zapco and Xtant are good
examples of ultra clean amplifiers.

Doesn't matter who makes it. All amplifiers made these days have
distortion
byproducts well below audible threshold. Especially compared to the
distortion that arises from driving your amp into clipping, which is
surprisingly common.

Eh maybe, but I refuse to believe that a Jensen or Dual amp is going to
sound as good and clean as a Zapco or Xtant.

Doesn't matter who makes it. All amplifiers made these days have
distortion
byproducts well below audible threshold. Especially compared to the
distortion that arises from driving your amp into clipping, which is
surprisingly common.

Eh maybe, but I refuse to believe that a Jensen or Dual amp is going to
sound as good and clean as a Zapco or Xtant.

Why? Because the price tag says it does?

"Mark Zarella" wrote in message
...
Doesn't matter who makes it. All amplifiers made these days have
distortion
byproducts well below audible threshold. Especially compared to the
distortion that arises from driving your amp into clipping, which is
surprisingly common.

Eh maybe, but I refuse to believe that a Jensen or Dual amp is going to
sound as good and clean as a Zapco or Xtant.

Why? Because the price tag says it does?

No, mainly becuase of the design and manufacturing. The power supply section
in a Zapco amp alone costs more than all the parts in some crap amp.

When referring to amplifiers the favorite catch-phrase of audiophiles
seems to be "clean power". As an ignorant novice I would like to know
what is meant by "clean power" and how do I achieve it.

There's no such thing. Power is power. What's usually meant is low
distortion and noise. It's easily attainable simply by not driving your amp
into clipping. That means use sufficient amplification for your needs.

Also, I once
heard something about voltage matching an amplifier with a head unit
but if I set my amp to 4v (same as the preouts on my head unit) I can
barely hear my subs. Do I need to add a bigger amp to get the benefit
of voltage matching? Will this theoretically provide "cleaner power"?

No. NEVER match your amplifier's gain setting to the nominal rating on your
head unit. It doesn't work because a) the output voltage of the HU doesn't
always meet the nominal rating, especially when listening to quieter
passages; b) filtering out higher frequencies with the LPF reduces voltage.
Go strictly by ear when setting gains. There's a tutorial at
installer.com's tech pages.

Let me shed some light:

There is such a thing as "clean" and "dirty" power. A perfect case in point
would be to run your amplifier with a cheap battery charger as its B+
supply. You will hear a tremendous amount of "hum". In other words, it is
"dirty" power. At the other extreme, hook up a whole bunch ( maybe 10 ) of
automotive batteries in series. Tap the "GND" from the connection between
battery 5 and battery 6. Tap the amplifiers output rails (+/-) from the
the top and bottom posts. to do this, you must eliminate the SMPS section
and some other items. The Rectifying diodes and the bulk rail capacitors
to be exact. You now have "clean" Power for your 400W/ch RMS amplifier.

Many things can affect just how "clean" an amplfier is. Power supply
topology, filter capacitors, Inductors, ferrite beads, transformer type,
board layout, star grounding, trace capacitance, trace inductance, PCB
layers ( e.g. 1, 2, 4 ). Do all these things right, and you have a "clean"
power amplifier. Do any one or all these things wrong and you now have a
"dirty" power amplifier. There is even an extreme case where when the
output rails do not have enough bulk capacitance, the output feedback
circuit goes "open loop" for just a microsecond or so. In this time, the
output transistors modulate or "burst" at their peaks causing audible
distortion. Lots of cheap amplifiers will do this just before clipping at
full power.

Not all things are created equal. Power is one of them.

If you want a mechanical analog, how about a V-8 piston engine and a jet
turbine

John Andreen

Mark Zarella wrote:

When referring to amplifiers the favorite catch-phrase of audiophiles
seems to be "clean power". As an ignorant novice I would like to know
what is meant by "clean power" and how do I achieve it.

There's no such thing. Power is power. What's usually meant is low
distortion and noise. It's easily attainable simply by not driving your
amp
into clipping. That means use sufficient amplification for your needs.

Also, I once
heard something about voltage matching an amplifier with a head unit
but if I set my amp to 4v (same as the preouts on my head unit) I can
barely hear my subs. Do I need to add a bigger amp to get the benefit
of voltage matching? Will this theoretically provide "cleaner power"?

No. NEVER match your amplifier's gain setting to the nominal rating on
your
head unit. It doesn't work because a) the output voltage of the HU
doesn't always meet the nominal rating, especially when listening to
quieter passages; b) filtering out higher frequencies with the LPF reduces
voltage.
Go strictly by ear when setting gains. There's a tutorial at
installer.com's tech pages.

There is such a thing as "clean" and "dirty" power. A perfect case in
point
would be to run your amplifier with a cheap battery charger as its B+
supply. You will hear a tremendous amount of "hum". In other words, it
is
"dirty" power. At the other extreme, hook up a whole bunch ( maybe 10 )
of
automotive batteries in series. Tap the "GND" from the connection between
battery 5 and battery 6. Tap the amplifiers output rails (+/-) from the
the top and bottom posts. to do this, you must eliminate the SMPS section
and some other items. The Rectifying diodes and the bulk rail capacitors
to be exact. You now have "clean" Power for your 400W/ch RMS amplifier.

Many things can affect just how "clean" an amplfier is. Power supply
topology, filter capacitors, Inductors, ferrite beads, transformer type,
board layout, star grounding, trace capacitance, trace inductance, PCB
layers ( e.g. 1, 2, 4 ). Do all these things right, and you have a
"clean"
power amplifier. Do any one or all these things wrong and you now have a
"dirty" power amplifier. There is even an extreme case where when the
output rails do not have enough bulk capacitance, the output feedback
circuit goes "open loop" for just a microsecond or so. In this time, the
output transistors modulate or "burst" at their peaks causing audible
distortion. Lots of cheap amplifiers will do this just before clipping at
full power.

Not all things are created equal. Power is one of them.

If you want a mechanical analog, how about a V-8 piston engine and a jet
turbine


That's all well and good, but the important thing to examine here is whether
the results are significant during normal operation. Hint: by significant,
I mean audible. While there are several ways to lower distortion (sometimes
at the expense of noise, or at the expense of reliability, or at the expense
of other forms of distortion, and so forth), there is of course a threshold
at which further reduction is not warranted, nor is it necessarily
recommended since there's almost always a tradeoff in some manner or
another.

So your engine analog holds true, but if your application is to just drive
down a road, then either one will perform as well as the other.

"Mark Zarella" wrote in message
...

So your engine analog holds true, but if your application is to just drive
down a road, then either one will perform as well as the other.

I guess that means that you run the cheapest amps you could find, correct?
By your logic a Rockwood sounds exactly like a McIntosh and it costs $2000
less, so do you run Rockwood amps? Dual? Pyramid?

So your engine analog holds true, but if your application is to just
drive
down a road, then either one will perform as well as the other.

I guess that means that you run the cheapest amps you could find, correct?

Assuming they delivered the power you're after and that they had the
features and reliability you're looking for, then yeah, price is generally
the next consideration.

By your logic a Rockwood sounds exactly like a McIntosh and it costs $2000
less, so do you run Rockwood amps? Dual? Pyramid?

I'd run a Pyramid before I'd run a McIntosh, as long as the Pyramid was
powerful enough and had the features I wanted. But, since neither
manufacturer makes one with the features I want, I personally wouldn't own
either.

Mr Zarella

You are correct, there is always a trade-off between a "clean" amplifier and
a "dirty" amplifier. But the "dirty" amplifier will always loose in terms
of reliability, distortion, sound quality etc. All at the expense of good
Engineering practices and a handful of parts.

On a side note, what would you rather be driving, a Yugo or a Mercedes? Ok,
not the same, but how about a Yugo or a Ford Focus? But if your life
depended on its proper operation all the time, which would you choose?

Here is another case in point. Old school PPI amplifiers. Some of these
amplifiers are over 15 years old and they are still operating and making
great sound. In fact, these units are still highly sought after. Can you
say the same for an equally aged Pioneer or Sony? I think you are perhaps
using a shifting baseline as to what is "clean" today.

Could you also be confusing distortion with noise? They are not the same.
You should do some investigation on these subjects. What you say is a
measurement of distortion is actually called "THD +N" a.k.a. Total Harmonic
Distortion + Noise. Then to make matters worse, some audio companies use
filters (read A-weighted) to make there units appear to have low THD+N. To
add even more confusion into the mix, this "THD+N" is almost always
computationally measured using FFT methods. There are more than a dozen
FFT windows ( read measuring envelope ) that can be used to make the
measurement. Each will give a return a different value for "THD+N". There
is one more thing about measuring "THD+N". One must also specify the power
of the signal being measured. One can measure at 1W, 5W, Full rated power,
etc. "THD+N" is not constant at all power levels. It is usually higher at
very low power levels and very high power levels. At very low power
levels, the major component comes from "noise". At very high power levels,
the major component comes from "THD". Really "clean" amplifiers have "TH
+N" values nearly equal at all power levels under clipping.

I can take even the "dirtiest" amplifier and measure extremely low values of
distortion. On the order of 1/1000 of a %. That is, if I can choose my
own method and power level of distortion measurement.

There is also harmonic distortion caused by the sum and difference of two
signals. Let's say a 40 kHz square wave from a power supply and a 1 kHz
sine wave. There will be strong harmonic distortion at 39 kHz and 41 kHz.
There are also artifacts called sub-harmonics of these two signals that
will be present. These are the artifacts that can appear down in the audio
spectrum. I would also like to point out that music isn't just 1 kHz, but
a plethora of frequencies.

I have told this group many times not to be concerned with "THD+N" as a
figure of merit when buying an amplifier. The human ear doesn't mind even
1-3% THD. It is a "Marketing Tool" designed to sway the masses. Go listen
to a high quality pure tube amplifier and a high quality transistorized
amplifier of the same output power specifications. Do this test blindly.
I am absolutely certain that you will always pick the tube amplifier over
the transistorized one as having the better sound. But, that tube
amplifier will have distortion figures SEVERAL HUNDRED TIMES WORSE than the
transistorized amplifier. Instead, try to buy an amplifier that has Low
"TIM" and low S/N. TIM stands for Transient Intermodulation Distortion.
Good audio distortion analyzers can find this kind of distortion using the
"IMD" settings.

Now, onto the subject of noise. Noise is ever present in the audio world.
It comes from the amplifiers SMPS. It comes from the Automobiles charging
system. It comes from solar wind. It comes from the power transmission
lines. In short, it comes from just about everywhere. In my last post, I
stated several things that make for a "clean" amplifier. Those things are
the items or methodologies used to eliminate or diminish the ingress of
noise into an amplifier. I forgot one them. Decoupling capacitors. Once
again, do not do any or all of those items, and more effective noise will
make it into the audio path. Do all of them right and you will diminish
the ingress of noise into the audio path and have a "clean" amplifier.

I have measured and tested amplifiers from many of the "top" car audio
companies. Some had signal to noise ratios of -50dB, some had signal to
noise ratios greater than -100dB. In other words, the best amplifiers S/N
was 64 times better than the worst. The reason, one amplifier was more
"clean" than anothers. Once again, you can fudge these numbers too. S/N
is different depending upon the position of the gain pot. At max gain, S/N
to noise will be different than min gain. The difference, a handful of
parts and good Engineering practices. QED

John Andreen


Mark Zarella wrote:

There is such a thing as "clean" and "dirty" power. A perfect case in
point
would be to run your amplifier with a cheap battery charger as its B+
supply. You will hear a tremendous amount of "hum". In other words, it
is
"dirty" power. At the other extreme, hook up a whole bunch ( maybe 10 )
of
automotive batteries in series. Tap the "GND" from the connection
between
battery 5 and battery 6. Tap the amplifiers output rails (+/-) from the
the top and bottom posts. to do this, you must eliminate the SMPS
section
and some other items. The Rectifying diodes and the bulk rail capacitors
to be exact. You now have "clean" Power for your 400W/ch RMS amplifier.

Many things can affect just how "clean" an amplfier is. Power supply
topology, filter capacitors, Inductors, ferrite beads, transformer type,
board layout, star grounding, trace capacitance, trace inductance, PCB
layers ( e.g. 1, 2, 4 ). Do all these things right, and you have a
"clean"
power amplifier. Do any one or all these things wrong and you now have a
"dirty" power amplifier. There is even an extreme case where when the
output rails do not have enough bulk capacitance, the output feedback
circuit goes "open loop" for just a microsecond or so. In this time, the
output transistors modulate or "burst" at their peaks causing audible
distortion. Lots of cheap amplifiers will do this just before clipping
at full power.

Not all things are created equal. Power is one of them.

If you want a mechanical analog, how about a V-8 piston engine and a jet
turbine


That's all well and good, but the important thing to examine here is
whether
the results are significant during normal operation. Hint: by
significant,
I mean audible. While there are several ways to lower distortion
(sometimes at the expense of noise, or at the expense of reliability, or
at the expense of other forms of distortion, and so forth), there is of
course a threshold at which further reduction is not warranted, nor is it
necessarily recommended since there's almost always a tradeoff in some
manner or another.

So your engine analog holds true, but if your application is to just drive
down a road, then either one will perform as well as the other.

John Andreen. The only SANE person (besides myself) that I've seen in this
newsgroup yet. You guys spouting out advice and acting like you know
everything should listen to Mr. Andreen. Trust me, you'll learn something.



"John Andreen" wrote in message
news:tMXJb.26126$i55.5289@fed1read06...
Mr Zarella

You are correct, there is always a trade-off between a "clean" amplifier
and
a "dirty" amplifier. But the "dirty" amplifier will always loose in terms
of reliability, distortion, sound quality etc. All at the expense of good
Engineering practices and a handful of parts.

On a side note, what would you rather be driving, a Yugo or a Mercedes?
Ok,
not the same, but how about a Yugo or a Ford Focus? But if your life
depended on its proper operation all the time, which would you choose?

Here is another case in point. Old school PPI amplifiers. Some of these
amplifiers are over 15 years old and they are still operating and making
great sound. In fact, these units are still highly sought after. Can you
say the same for an equally aged Pioneer or Sony? I think you are perhaps
using a shifting baseline as to what is "clean" today.

Could you also be confusing distortion with noise? They are not the same.
You should do some investigation on these subjects. What you say is a
measurement of distortion is actually called "THD +N" a.k.a. Total
Harmonic
Distortion + Noise. Then to make matters worse, some audio companies use
filters (read A-weighted) to make there units appear to have low THD+N.
To
add even more confusion into the mix, this "THD+N" is almost always
computationally measured using FFT methods. There are more than a dozen
FFT windows ( read measuring envelope ) that can be used to make the
measurement. Each will give a return a different value for "THD+N". There
is one more thing about measuring "THD+N". One must also specify the
power
of the signal being measured. One can measure at 1W, 5W, Full rated
power,
etc. "THD+N" is not constant at all power levels. It is usually higher
at
very low power levels and very high power levels. At very low power
levels, the major component comes from "noise". At very high power
levels,
the major component comes from "THD". Really "clean" amplifiers have "TH
+N" values nearly equal at all power levels under clipping.

I can take even the "dirtiest" amplifier and measure extremely low values
of
distortion. On the order of 1/1000 of a %. That is, if I can choose my
own method and power level of distortion measurement.

There is also harmonic distortion caused by the sum and difference of two
signals. Let's say a 40 kHz square wave from a power supply and a 1 kHz
sine wave. There will be strong harmonic distortion at 39 kHz and 41 kHz.
There are also artifacts called sub-harmonics of these two signals that
will be present. These are the artifacts that can appear down in the
audio
spectrum. I would also like to point out that music isn't just 1 kHz, but
a plethora of frequencies.

I have told this group many times not to be concerned with "THD+N" as a
figure of merit when buying an amplifier. The human ear doesn't mind even
1-3% THD. It is a "Marketing Tool" designed to sway the masses. Go
listen
to a high quality pure tube amplifier and a high quality transistorized
amplifier of the same output power specifications. Do this test blindly.
I am absolutely certain that you will always pick the tube amplifier over
the transistorized one as having the better sound. But, that tube
amplifier will have distortion figures SEVERAL HUNDRED TIMES WORSE than
the
transistorized amplifier. Instead, try to buy an amplifier that has Low
"TIM" and low S/N. TIM stands for Transient Intermodulation Distortion.
Good audio distortion analyzers can find this kind of distortion using the
"IMD" settings.

Now, onto the subject of noise. Noise is ever present in the audio world.
It comes from the amplifiers SMPS. It comes from the Automobiles charging
system. It comes from solar wind. It comes from the power transmission
lines. In short, it comes from just about everywhere. In my last post, I
stated several things that make for a "clean" amplifier. Those things are
the items or methodologies used to eliminate or diminish the ingress of
noise into an amplifier. I forgot one them. Decoupling capacitors. Once
again, do not do any or all of those items, and more effective noise will
make it into the audio path. Do all of them right and you will diminish
the ingress of noise into the audio path and have a "clean" amplifier.

I have measured and tested amplifiers from many of the "top" car audio
companies. Some had signal to noise ratios of -50dB, some had signal to
noise ratios greater than -100dB. In other words, the best amplifiers S/N
was 64 times better than the worst. The reason, one amplifier was more
"clean" than anothers. Once again, you can fudge these numbers too. S/N
is different depending upon the position of the gain pot. At max gain,
S/N
to noise will be different than min gain. The difference, a handful of
parts and good Engineering practices. QED

John Andreen


Mark Zarella wrote:

There is such a thing as "clean" and "dirty" power. A perfect case in
point
would be to run your amplifier with a cheap battery charger as its B+
supply. You will hear a tremendous amount of "hum". In other words,
it
is
"dirty" power. At the other extreme, hook up a whole bunch ( maybe
10 )
of
automotive batteries in series. Tap the "GND" from the connection
between
battery 5 and battery 6. Tap the amplifiers output rails (+/-) from
the
the top and bottom posts. to do this, you must eliminate the SMPS
section
and some other items. The Rectifying diodes and the bulk rail
capacitors
to be exact. You now have "clean" Power for your 400W/ch RMS
amplifier.

Many things can affect just how "clean" an amplfier is. Power supply
topology, filter capacitors, Inductors, ferrite beads, transformer
type,
board layout, star grounding, trace capacitance, trace inductance, PCB
layers ( e.g. 1, 2, 4 ). Do all these things right, and you have a
"clean"
power amplifier. Do any one or all these things wrong and you now have
a
"dirty" power amplifier. There is even an extreme case where when the
output rails do not have enough bulk capacitance, the output feedback
circuit goes "open loop" for just a microsecond or so. In this time,
the
output transistors modulate or "burst" at their peaks causing audible
distortion. Lots of cheap amplifiers will do this just before clipping
at full power.

Not all things are created equal. Power is one of them.

If you want a mechanical analog, how about a V-8 piston engine and a
jet
turbine


That's all well and good, but the important thing to examine here is
whether
the results are significant during normal operation. Hint: by
significant,
I mean audible. While there are several ways to lower distortion
(sometimes at the expense of noise, or at the expense of reliability, or
at the expense of other forms of distortion, and so forth), there is of
course a threshold at which further reduction is not warranted, nor is
it
necessarily recommended since there's almost always a tradeoff in some
manner or another.

So your engine analog holds true, but if your application is to just
drive
down a road, then either one will perform as well as the other.

On Sun, 04 Jan 2004 10:12:23 -0700, John Andreen
wrote:

Mr Zarella

You are correct, there is always a trade-off between a "clean" amplifier and
a "dirty" amplifier. But the "dirty" amplifier will always loose in terms
of reliability, distortion, sound quality etc. All at the expense of good
Engineering practices and a handful of parts.

On a side note, what would you rather be driving, a Yugo or a Mercedes? Ok,
not the same, but how about a Yugo or a Ford Focus? But if your life
depended on its proper operation all the time, which would you choose?

Here is another case in point. Old school PPI amplifiers. Some of these
amplifiers are over 15 years old and they are still operating and making
great sound. In fact, these units are still highly sought after. Can you
say the same for an equally aged Pioneer or Sony? I think you are perhaps
using a shifting baseline as to what is "clean" today.

http://silverpioneer.com/


Could you also be confusing distortion with noise? They are not the same.
You should do some investigation on these subjects. What you say is a
measurement of distortion is actually called "THD +N" a.k.a. Total Harmonic
Distortion + Noise. Then to make matters worse, some audio companies use
filters (read A-weighted) to make there units appear to have low THD+N. To
add even more confusion into the mix, this "THD+N" is almost always
computationally measured using FFT methods. There are more than a dozen
FFT windows ( read measuring envelope ) that can be used to make the
measurement. Each will give a return a different value for "THD+N". There
is one more thing about measuring "THD+N". One must also specify the power
of the signal being measured. One can measure at 1W, 5W, Full rated power,
etc. "THD+N" is not constant at all power levels. It is usually higher at
very low power levels and very high power levels. At very low power
levels, the major component comes from "noise". At very high power levels,
the major component comes from "THD". Really "clean" amplifiers have "TH
+N" values nearly equal at all power levels under clipping.

I can take even the "dirtiest" amplifier and measure extremely low values of
distortion. On the order of 1/1000 of a %. That is, if I can choose my
own method and power level of distortion measurement.

There is also harmonic distortion caused by the sum and difference of two
signals. Let's say a 40 kHz square wave from a power supply and a 1 kHz
sine wave. There will be strong harmonic distortion at 39 kHz and 41 kHz.
There are also artifacts called sub-harmonics of these two signals that
will be present. These are the artifacts that can appear down in the audio
spectrum. I would also like to point out that music isn't just 1 kHz, but
a plethora of frequencies.

I have told this group many times not to be concerned with "THD+N" as a
figure of merit when buying an amplifier. The human ear doesn't mind even
1-3% THD. It is a "Marketing Tool" designed to sway the masses. Go listen
to a high quality pure tube amplifier and a high quality transistorized
amplifier of the same output power specifications. Do this test blindly.
I am absolutely certain that you will always pick the tube amplifier over
the transistorized one as having the better sound. But, that tube
amplifier will have distortion figures SEVERAL HUNDRED TIMES WORSE than the
transistorized amplifier. Instead, try to buy an amplifier that has Low
"TIM" and low S/N. TIM stands for Transient Intermodulation Distortion.
Good audio distortion analyzers can find this kind of distortion using the
"IMD" settings.

Now, onto the subject of noise. Noise is ever present in the audio world.
It comes from the amplifiers SMPS. It comes from the Automobiles charging
system. It comes from solar wind. It comes from the power transmission
lines. In short, it comes from just about everywhere. In my last post, I
stated several things that make for a "clean" amplifier. Those things are
the items or methodologies used to eliminate or diminish the ingress of
noise into an amplifier. I forgot one them. Decoupling capacitors. Once
again, do not do any or all of those items, and more effective noise will
make it into the audio path. Do all of them right and you will diminish
the ingress of noise into the audio path and have a "clean" amplifier.

I have measured and tested amplifiers from many of the "top" car audio
companies. Some had signal to noise ratios of -50dB, some had signal to
noise ratios greater than -100dB. In other words, the best amplifiers S/N
was 64 times better than the worst. The reason, one amplifier was more
"clean" than anothers. Once again, you can fudge these numbers too. S/N
is different depending upon the position of the gain pot. At max gain, S/N
to noise will be different than min gain. The difference, a handful of
parts and good Engineering practices. QED

John Andreen


Mark Zarella wrote:

There is such a thing as "clean" and "dirty" power. A perfect case in
point
would be to run your amplifier with a cheap battery charger as its B+
supply. You will hear a tremendous amount of "hum". In other words, it
is
"dirty" power. At the other extreme, hook up a whole bunch ( maybe 10 )
of
automotive batteries in series. Tap the "GND" from the connection
between
battery 5 and battery 6. Tap the amplifiers output rails (+/-) from the
the top and bottom posts. to do this, you must eliminate the SMPS
section
and some other items. The Rectifying diodes and the bulk rail capacitors
to be exact. You now have "clean" Power for your 400W/ch RMS amplifier.

Many things can affect just how "clean" an amplfier is. Power supply
topology, filter capacitors, Inductors, ferrite beads, transformer type,
board layout, star grounding, trace capacitance, trace inductance, PCB
layers ( e.g. 1, 2, 4 ). Do all these things right, and you have a
"clean"
power amplifier. Do any one or all these things wrong and you now have a
"dirty" power amplifier. There is even an extreme case where when the
output rails do not have enough bulk capacitance, the output feedback
circuit goes "open loop" for just a microsecond or so. In this time, the
output transistors modulate or "burst" at their peaks causing audible
distortion. Lots of cheap amplifiers will do this just before clipping
at full power.

Not all things are created equal. Power is one of them.

If you want a mechanical analog, how about a V-8 piston engine and a jet
turbine


That's all well and good, but the important thing to examine here is
whether
the results are significant during normal operation. Hint: by
significant,
I mean audible. While there are several ways to lower distortion
(sometimes at the expense of noise, or at the expense of reliability, or
at the expense of other forms of distortion, and so forth), there is of
course a threshold at which further reduction is not warranted, nor is it
necessarily recommended since there's almost always a tradeoff in some
manner or another.

So your engine analog holds true, but if your application is to just drive
down a road, then either one will perform as well as the other.

Mr Zarella

You are correct, there is always a trade-off between a "clean" amplifier
and
a "dirty" amplifier. But the "dirty" amplifier will always loose in terms
of reliability, distortion, sound quality etc. All at the expense of good
Engineering practices and a handful of parts.

I have to disagree with you on this point. But I suppose much of it depends
on what you're referring to exactly when you use the term "dirty". I assume
you're talking about distortion and noise, and maybe frequency response.
Much of the distortion characteristics of an audio amplifier are due to the
input stage circuitry, even moreso than the components. You can further
reduce harmonic distortion trhough additional circuitry, however statistical
reliability is sacrificed by doing so. PSRR methods are usually sufficient
in even the simplest IPS designs, and noise is rarely an issue. The biggest
issue to tackle is linearity when compensating for freq response
imperfections. But I don't know of any modern-day class AB amplifiers that
don't perform adequately in this respect.


On a side note, what would you rather be driving, a Yugo or a Mercedes?
Ok,
not the same, but how about a Yugo or a Ford Focus? But if your life
depended on its proper operation all the time, which would you choose?

You're talking about reliability concerns I think, which I haven't disagreed
with anyone on in this thread. The analogy when applied to sound quality
does not apply, unless of course you're talking about driving 5 MPH down the
road, in which case you wouldn't notice a difference. The reason I modify
your analogy is because it completely neglects the measuring device: that
is, the human brain.

Here is another case in point. Old school PPI amplifiers. Some of these
amplifiers are over 15 years old and they are still operating and making
great sound. In fact, these units are still highly sought after. Can you
say the same for an equally aged Pioneer or Sony? I think you are perhaps
using a shifting baseline as to what is "clean" today.

Not sure what reliability has to do with "clean"/"dirty".


Could you also be confusing distortion with noise? They are not the same.
You should do some investigation on these subjects. What you say is a
measurement of distortion is actually called "THD +N" a.k.a. Total
Harmonic
Distortion + Noise.

There are several sources of distortion (but the resulting types of
distortion can most easily be narrowed down to harmonic distortion,
intermodulation distortion, and phase distortion), and I don't believe I've
narrowed it down to any of them. I've generally been referring to
distortion, noise, frequency/phase response as a whole in the discussion of
sound quality.

Then to make matters worse, some audio companies use
filters (read A-weighted) to make there units appear to have low THD+N

Are you referring to the amplifier designs or the testing methodologies?

To
add even more confusion into the mix, this "THD+N" is almost always
computationally measured using FFT methods. There are more than a dozen
FFT windows ( read measuring envelope ) that can be used to make the
measurement. Each will give a return a different value for "THD+N".

The estimation procedure is not vital in this case. A confidence interval
can be derived from any estimation procedure, and if the sample size is
large enough (and given the limited bandwidth in audio) it's quite easy to
limit the bias and variance to negligible levels, especially with proper
windowing when applicable.

There
is one more thing about measuring "THD+N". One must also specify the
power
of the signal being measured. One can measure at 1W, 5W, Full rated
power,
etc. "THD+N" is not constant at all power levels. It is usually higher
at
very low power levels and very high power levels. At very low power
levels, the major component comes from "noise". At very high power
levels,
the major component comes from "THD". Really "clean" amplifiers have "TH
+N" values nearly equal at all power levels under clipping.

Right. Distortion levels vary significantly with different power levels.
Good distortion measurements (like the kind I use ) take this into
account by performing the analysis at different power levels and with
different signals. Harmonic distortion is easy. It's IMD where you start
having to make seemingly arbitrary (though not necessarily incomplete)
decisions.

I can take even the "dirtiest" amplifier and measure extremely low values
of
distortion. On the order of 1/1000 of a %. That is, if I can choose my
own method and power level of distortion measurement.

That's why it's important to use representative techniques and keep them
uniform.


There is also harmonic distortion caused by the sum and difference of two
signals. Let's say a 40 kHz square wave from a power supply and a 1 kHz
sine wave. There will be strong harmonic distortion at 39 kHz and 41 kHz.
There are also artifacts called sub-harmonics of these two signals that
will be present. These are the artifacts that can appear down in the
audio
spectrum. I would also like to point out that music isn't just 1 kHz, but
a plethora of frequencies.

I have told this group many times not to be concerned with "THD+N" as a
figure of merit when buying an amplifier. The human ear doesn't mind even
1-3% THD.

Well, that can depend on a number of other factors, but your point is well
taken.

It is a "Marketing Tool" designed to sway the masses. Go listen
to a high quality pure tube amplifier and a high quality transistorized
amplifier of the same output power specifications. Do this test blindly.
I am absolutely certain that you will always pick the tube amplifier over
the transistorized one as having the better sound. But, that tube
amplifier will have distortion figures SEVERAL HUNDRED TIMES WORSE than
the
transistorized amplifier. Instead, try to buy an amplifier that has Low
"TIM" and low S/N. TIM stands for Transient Intermodulation Distortion.
Good audio distortion analyzers can find this kind of distortion using the
"IMD" settings.

I agree completely. But note that the discussion at hand is picking apart
the difference, rather than the more "pleasing" sound. Several reports have
demonstrated that many listeners actually prefer even order harmonics, which
tend to be especially high in tube designs. However, other reports say
quite the opposite, and asymmetrical clipping which often results in high
even order harmonic content is generally viewed as unfavorable. The most
telling paper I've read on the subject is Farrimond, Perceptual and Motor
Skills,1990,70. He found that in the subjective evaluation of audio
components, it was quite easy to implement paradigms where the users could
tell the difference between two sounds but could not reliably label which
was more or less distorted.


Now, onto the subject of noise. Noise is ever present in the audio world.
It comes from the amplifiers SMPS. It comes from the Automobiles charging
system. It comes from solar wind. It comes from the power transmission
lines. In short, it comes from just about everywhere. In my last post, I
stated several things that make for a "clean" amplifier. Those things are
the items or methodologies used to eliminate or diminish the ingress of
noise into an amplifier. I forgot one them. Decoupling capacitors. Once
again, do not do any or all of those items, and more effective noise will
make it into the audio path. Do all of them right and you will diminish
the ingress of noise into the audio path and have a "clean" amplifier.

I don't know of any modern amplifiers where the inherent noise is a problem.
In fact, the noise resulting from less-than-stellar installation tends to be
much larger than that which cannot be overcome in the amplifier. I said
earlier in the thread however that some amplifiers are more prone to noise
than others, but the significant portion can be eliminated with good
installation techniques. It wasn't too long ago that -70dB to -80dB was
considered good. And IMO, in the car that still is perfectly sufficient.
Now people quibble over the difference between -100dB and -92dB. Again,
it's inconsequential.


I have measured and tested amplifiers from many of the "top" car audio
companies. Some had signal to noise ratios of -50dB, some had signal to
noise ratios greater than -100dB. In other words, the best amplifiers S/N
was 64 times better than the worst. The reason, one amplifier was more
"clean" than anothers. Once again, you can fudge these numbers too. S/N
is different depending upon the position of the gain pot. At max gain,
S/N
to noise will be different than min gain. The difference, a handful of
parts and good Engineering practices. QED

Our disagreement isn't in the electrical aspect of the amplifier. We agree
on just about all of it. Rather, it's the psychophysical end of things.
Pushing distortion down past the noise floor is unnecessary. Trying to
obtain -100dB noise levels is unnecessary. Trying to minimize freq
response dips to below 1dB is unnecessary. This can all be demonstrated in
psychophysical experiments. And these so-called "dirty amplifiers" (even
when, in many cases, the cheaper amplifier is actually "cleaner" than the
more expensive one), do not exhibit deficiencies in any of these categories
that can be detected by us listeners, especially in an electric and acoustic
noise box like a car.

You could say the same about an original Sony XES-M1 or M3... I think
you need to establish an apples to apples comparison, can't compare
premium product with run of the mill stuff and expect them to "age" the
same.

JD

John Andreen wrote:

Mr Zarella

You are correct, there is always a trade-off between a "clean" amplifier and
a "dirty" amplifier. But the "dirty" amplifier will always loose in terms
of reliability, distortion, sound quality etc. All at the expense of good
Engineering practices and a handful of parts.

On a side note, what would you rather be driving, a Yugo or a Mercedes? Ok,
not the same, but how about a Yugo or a Ford Focus? But if your life
depended on its proper operation all the time, which would you choose?

Here is another case in point. Old school PPI amplifiers. Some of these
amplifiers are over 15 years old and they are still operating and making
great sound. In fact, these units are still highly sought after. Can you
say the same for an equally aged Pioneer or Sony? I think you are perhaps
using a shifting baseline as to what is "clean" today.

Could you also be confusing distortion with noise? They are not the same.
You should do some investigation on these subjects. What you say is a
measurement of distortion is actually called "THD +N" a.k.a. Total Harmonic
Distortion + Noise. Then to make matters worse, some audio companies use
filters (read A-weighted) to make there units appear to have low THD+N. To
add even more confusion into the mix, this "THD+N" is almost always
computationally measured using FFT methods. There are more than a dozen
FFT windows ( read measuring envelope ) that can be used to make the
measurement. Each will give a return a different value for "THD+N". There
is one more thing about measuring "THD+N". One must also specify the power
of the signal being measured. One can measure at 1W, 5W, Full rated power,
etc. "THD+N" is not constant at all power levels. It is usually higher at
very low power levels and very high power levels. At very low power
levels, the major component comes from "noise". At very high power levels,
the major component comes from "THD". Really "clean" amplifiers have "TH
+N" values nearly equal at all power levels under clipping.

I can take even the "dirtiest" amplifier and measure extremely low values of
distortion. On the order of 1/1000 of a %. That is, if I can choose my
own method and power level of distortion measurement.

There is also harmonic distortion caused by the sum and difference of two
signals. Let's say a 40 kHz square wave from a power supply and a 1 kHz
sine wave. There will be strong harmonic distortion at 39 kHz and 41 kHz.
There are also artifacts called sub-harmonics of these two signals that
will be present. These are the artifacts that can appear down in the audio
spectrum. I would also like to point out that music isn't just 1 kHz, but
a plethora of frequencies.

I have told this group many times not to be concerned with "THD+N" as a
figure of merit when buying an amplifier. The human ear doesn't mind even
1-3% THD. It is a "Marketing Tool" designed to sway the masses. Go listen
to a high quality pure tube amplifier and a high quality transistorized
amplifier of the same output power specifications. Do this test blindly.
I am absolutely certain that you will always pick the tube amplifier over
the transistorized one as having the better sound. But, that tube
amplifier will have distortion figures SEVERAL HUNDRED TIMES WORSE than the
transistorized amplifier. Instead, try to buy an amplifier that has Low
"TIM" and low S/N. TIM stands for Transient Intermodulation Distortion.
Good audio distortion analyzers can find this kind of distortion using the
"IMD" settings.

Now, onto the subject of noise. Noise is ever present in the audio world.
It comes from the amplifiers SMPS. It comes from the Automobiles charging
system. It comes from solar wind. It comes from the power transmission
lines. In short, it comes from just about everywhere. In my last post, I
stated several things that make for a "clean" amplifier. Those things are
the items or methodologies used to eliminate or diminish the ingress of
noise into an amplifier. I forgot one them. Decoupling capacitors. Once
again, do not do any or all of those items, and more effective noise will
make it into the audio path. Do all of them right and you will diminish
the ingress of noise into the audio path and have a "clean" amplifier.

I have measured and tested amplifiers from many of the "top" car audio
companies. Some had signal to noise ratios of -50dB, some had signal to
noise ratios greater than -100dB. In other words, the best amplifiers S/N
was 64 times better than the worst. The reason, one amplifier was more
"clean" than anothers. Once again, you can fudge these numbers too. S/N
is different depending upon the position of the gain pot. At max gain, S/N
to noise will be different than min gain. The difference, a handful of
parts and good Engineering practices. QED

John Andreen


Mark Zarella wrote:



There is such a thing as "clean" and "dirty" power. A perfect case in


point


would be to run your amplifier with a cheap battery charger as its B+
supply. You will hear a tremendous amount of "hum". In other words, it


is


"dirty" power. At the other extreme, hook up a whole bunch ( maybe 10 )


of


automotive batteries in series. Tap the "GND" from the connection
between
battery 5 and battery 6. Tap the amplifiers output rails (+/-) from the
the top and bottom posts. to do this, you must eliminate the SMPS
section
and some other items. The Rectifying diodes and the bulk rail capacitors
to be exact. You now have "clean" Power for your 400W/ch RMS amplifier.

Many things can affect just how "clean" an amplfier is. Power supply
topology, filter capacitors, Inductors, ferrite beads, transformer type,
board layout, star grounding, trace capacitance, trace inductance, PCB
layers ( e.g. 1, 2, 4 ). Do all these things right, and you have a


"clean"


power amplifier. Do any one or all these things wrong and you now have a
"dirty" power amplifier. There is even an extreme case where when the
output rails do not have enough bulk capacitance, the output feedback
circuit goes "open loop" for just a microsecond or so. In this time, the
output transistors modulate or "burst" at their peaks causing audible
distortion. Lots of cheap amplifiers will do this just before clipping
at full power.

Not all things are created equal. Power is one of them.

If you want a mechanical analog, how about a V-8 piston engine and a jet
turbine


That's all well and good, but the important thing to examine here is
whether
the results are significant during normal operation. Hint: by
significant,
I mean audible. While there are several ways to lower distortion
(sometimes at the expense of noise, or at the expense of reliability, or
at the expense of other forms of distortion, and so forth), there is of
course a threshold at which further reduction is not warranted, nor is it
necessarily recommended since there's almost always a tradeoff in some
manner or another.

So your engine analog holds true, but if your application is to just drive
down a road, then either one will perform as well as the other.