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James Price[_5_] James Price[_5_] is offline
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Default Question about Digital vs. Analog

What's the differentiating factor between digital clipping at the input stage, and its effect on the end result, compared to how an analog guitar amplifier sounds when boosted?

To refine the question, if I'm recording guitar using a digital amp / guitar cab simulator into a DAW and the input of the guitar is clipping, how does that clipping affect the digital amp / cab and what's the end result at the output end (after the amp / cab) compared to an analog amplifier with huge amounts of input boost?

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Neil[_9_] Neil[_9_] is offline
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On 2/10/2019 12:28 AM, James Price wrote:
What's the differentiating factor between digital clipping at the input stage, and its effect on the end result, compared to how an analog guitar amplifier sounds when boosted?

To refine the question, if I'm recording guitar using a digital amp / guitar cab simulator into a DAW and the input of the guitar is clipping, how does that clipping affect the digital amp / cab and what's the end result at the output end (after the amp / cab) compared to an analog amplifier with huge amounts of input boost?

I'm not sure what you are referring to as "digital clipping", or how
that is being achieved. If by "...its effect on the end result" you mean
how it sounds, there is no one single answer.

your refinement of the question, what is causing the input of the
guitar to clip? Is this "guitar" a physical instrument, or is it a
sampled file? If it's a real guitar, how and why would the instrument's
input clip, since the "input" is the magnetic pickup of string
vibrations (and totally analog, not that it matters)?

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best regards,

Neil
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On 2/10/2019 12:28 AM, James Price wrote:
What's the differentiating factor between digital clipping at the input stage, and its effect on the end result, compared to how an analog guitar amplifier sounds when boosted?


The input stage of a guitar amplifier is always analog, so if there's
clipping at the input stage, it's "analog clipping." The
analog-to-digital converter will reproduce the clipping very accurately.

To refine the question, if I'm recording guitar using a digital amp / guitar cab simulator into a DAW and the input of the guitar is clipping, how does that clipping affect the digital amp / cab and what's the end result at the output end (after the amp / cab) compared to an analog amplifier with huge amounts of input boost?


A properly designed digital system will accommodate (and properly
digitize) a signal with the maximum output level of the analog input
stage. The maximum output level of the input stage is the point at which
clipping begins.

It's not completely clear what you're asking about, though. If you have
a guitar amplifier with a standard input jack, internal digital
processing, a power amplifier, and a loudspeaker, it will work just like
a straight-through analog amplifier. But I have a sense that this isn't
what you're talking about.

So if you have a computer audio interface ("sound card") that has an
input for a guitar, that's connected to your computer, and you have an
amplifier and speaker plug-in inserted on a track in your DAW that
you're using to process the guitar signal. You can crank up the guitar
output and the input gain on the interface so that you get analog
clipping going into the digital guts of the interface. That's the sound
that will be feeding the plug-in. If you keep the gain down so that the
interface's input stage isn't clipping, then the plug-in will be getting
a clean signal and you can use its controls to bugger it up however you
want.

Unless you have an interface that's specifically designed to be used
with a guitar (a few of them showed up at the NAMM show last month), you
shouldn't expect the guitar input of your interface to distort in the
same way as the input of a real amplifier, and the kind of distortion
that you get from pushing the output stage of an amplifier hard is what
will be simulated by the plug-in. They're pretty flexible so you can get
a lot more different sound colors from the same input signal than you
can from most amplifiers.

You just have to play around to get the sound that you like, but because
you have more tools, it will take more time than just plugging in and
playing. But you can do that, too, with a digital system, once you get
the hang of it.





--
For a good time, call http://mikeriversaudio.wordpress.com
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Scott Dorsey Scott Dorsey is offline
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James Price wrote:
What's the differentiating factor between digital clipping at the input sta=
ge, and its effect on the end result, compared to how an analog guitar ampl=
ifier sounds when boosted?


This is not a digital vs. analogue question. You are asking whether clipping
the analogue input of an ADC is different than clipping the analogue input of
a guitar amplifier.

And... the answer is.... it depends a lot on the ADC and on the amplifier.
In both cases you're creating a lot of odd harmonics, but the actual
spectrum varies a lot. You can likely assume both are nonlinear but
time-invariant (although there used to be some ADCs that would stick to
the rails when clipped).

To refine the question, if I'm recording guitar using a digital amp / guita=
r cab simulator into a DAW and the input of the guitar is clipping, how doe=
s that clipping affect the digital amp / cab and what's the end result at t=
he output end (after the amp / cab) compared to an analog amplifier with hu=
ge amounts of input boost?


It will sound different because the spectrum is different.

But you're using this as a musical instrument. If it sounds the way you
want, do it.

But be aware that although most guitar amps are designed with the intention
of clipping them, most ADC designers didn't spent a lot of time worrying about
clipping behaviour because they didn't expect people to use them that way.
So you're likely to find that no two ADCs sound quite the same way when
overloaded.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."
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Don Pearce[_3_] Don Pearce[_3_] is offline
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Default Question about Digital vs. Analog

On 10 Feb 2019 09:22:28 -0500, (Scott Dorsey) wrote:

James Price wrote:
What's the differentiating factor between digital clipping at the input sta=
ge, and its effect on the end result, compared to how an analog guitar ampl=
ifier sounds when boosted?


This is not a digital vs. analogue question. You are asking whether clipping
the analogue input of an ADC is different than clipping the analogue input of
a guitar amplifier.

And... the answer is.... it depends a lot on the ADC and on the amplifier.
In both cases you're creating a lot of odd harmonics, but the actual
spectrum varies a lot. You can likely assume both are nonlinear but
time-invariant (although there used to be some ADCs that would stick to
the rails when clipped).

To refine the question, if I'm recording guitar using a digital amp / guita=
r cab simulator into a DAW and the input of the guitar is clipping, how doe=
s that clipping affect the digital amp / cab and what's the end result at t=
he output end (after the amp / cab) compared to an analog amplifier with hu=
ge amounts of input boost?


It will sound different because the spectrum is different.

But you're using this as a musical instrument. If it sounds the way you
want, do it.

But be aware that although most guitar amps are designed with the intention
of clipping them, most ADC designers didn't spent a lot of time worrying about
clipping behaviour because they didn't expect people to use them that way.
So you're likely to find that no two ADCs sound quite the same way when
overloaded.
--scott


If the clipping in an ADC happens after the anti-alias filter (ie
actual numeric digital clipping), you are in trouble, because you now
have high frequency products that are not filtered away, but are right
there and are going to produce alias frequencies in the audio band.
They won't be harmonically related as analogue clipping would be, but
they will instead be dissonant. You really don't want this to happen,
because once they have been produced, there is no DSP capable of
removing them.

d


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Scott Dorsey Scott Dorsey is offline
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Default Question about Digital vs. Analog

Don Pearce wrote:
If the clipping in an ADC happens after the anti-alias filter (ie
actual numeric digital clipping), you are in trouble, because you now
have high frequency products that are not filtered away, but are right
there and are going to produce alias frequencies in the audio band.
They won't be harmonically related as analogue clipping would be, but
they will instead be dissonant. You really don't want this to happen,
because once they have been produced, there is no DSP capable of
removing them.


Yes, but analogue clipping can produce intermodulation products too.
The effect isn't usually as obvious, but it can be pretty bad.

Still... maybe it's the cool sound that he's looking for on his guitar.
You never know until you try it.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
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James Price[_5_] James Price[_5_] is offline
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Default Question about Digital vs. Analog

On Sunday, February 10, 2019 at 8:22:32 AM UTC-6, Scott Dorsey wrote:
James Price wrote:
What's the differentiating factor between digital clipping at the input sta=
ge, and its effect on the end result, compared to how an analog guitar ampl=
ifier sounds when boosted?


This is not a digital vs. analogue question. You are asking whether clipping
the analogue input of an ADC is different than clipping the analogue input of
a guitar amplifier.

And... the answer is.... it depends a lot on the ADC and on the amplifier.
In both cases you're creating a lot of odd harmonics, but the actual
spectrum varies a lot. You can likely assume both are nonlinear but
time-invariant (although there used to be some ADCs that would stick to
the rails when clipped).

To refine the question, if I'm recording guitar using a digital amp / guita=
r cab simulator into a DAW and the input of the guitar is clipping, how doe=
s that clipping affect the digital amp / cab and what's the end result at t=
he output end (after the amp / cab) compared to an analog amplifier with hu=
ge amounts of input boost?


It will sound different because the spectrum is different.

But you're using this as a musical instrument. If it sounds the way you
want, do it.

But be aware that although most guitar amps are designed with the intention
of clipping them, most ADC designers didn't spent a lot of time worrying about
clipping behaviour because they didn't expect people to use them that way.
So you're likely to find that no two ADCs sound quite the same way when
overloaded.


I was under the impression that the primary difference is that overloading
the front end of the ADC would potentially produce digital hard clipping at
the output, that is assuming the amp sim's volume isn't set particularly low
and the input level is cranked high enough. For example, a 50 dB boost applied
to the input of an ADC vs. an analog amp. Both will clip, but my presumption
was that the ADC would produce digital hard clipping in the form of a square
waveform, whereas hard clipping in the analog amp would produce a waveform
that wasn't chopped.
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Scott Dorsey Scott Dorsey is offline
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James Price wrote:
I was under the impression that the primary difference is that overloading
the front end of the ADC would potentially produce digital hard clipping at
the output, that is assuming the amp sim's volume isn't set particularly low
and the input level is cranked high enough. For example, a 50 dB boost applied
to the input of an ADC vs. an analog amp. Both will clip, but my presumption
was that the ADC would produce digital hard clipping in the form of a square
waveform, whereas hard clipping in the analog amp would produce a waveform
that wasn't chopped.


Clipping is clipping. Some analogue circuits will "clip softly" which is
to say they have a little gain reduction right before they come to the
clipping point. Some analogue circuits will overshoot when they clip.
Some will get stuck for a cycle or two when they clip.

All of these will result in a different spectrum. You'll still get the
odd harmonics that you get from perfect clipping, but the ratio between
them will be different and you'll get other stuff too.

People that build guitar amps think a lot about behaviour of circuits
when they clip, but most designers don't care about it because they don't
expect people will ever clip anything. Hi-fi tube amps often use splitter
circuits like the paraphase inverter or the see-saw, which you will never
see in guitar amps because they behave very badly when clipped.

When you go into clipping, you have left the normal operating envelope of
the equipment, and you have become a test pilot. Don't make any assumptions
about how anything will behave when it's clipped. If you intend on using
clipping as an effect, try it and listen.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
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Don Pearce[_3_] Don Pearce[_3_] is offline
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On Sun, 10 Feb 2019 11:28:50 -0800 (PST), James Price
wrote:

On Sunday, February 10, 2019 at 8:22:32 AM UTC-6, Scott Dorsey wrote:
James Price wrote:
What's the differentiating factor between digital clipping at the input sta=
ge, and its effect on the end result, compared to how an analog guitar ampl=
ifier sounds when boosted?


This is not a digital vs. analogue question. You are asking whether clipping
the analogue input of an ADC is different than clipping the analogue input of
a guitar amplifier.

And... the answer is.... it depends a lot on the ADC and on the amplifier.
In both cases you're creating a lot of odd harmonics, but the actual
spectrum varies a lot. You can likely assume both are nonlinear but
time-invariant (although there used to be some ADCs that would stick to
the rails when clipped).

To refine the question, if I'm recording guitar using a digital amp / guita=
r cab simulator into a DAW and the input of the guitar is clipping, how doe=
s that clipping affect the digital amp / cab and what's the end result at t=
he output end (after the amp / cab) compared to an analog amplifier with hu=
ge amounts of input boost?


It will sound different because the spectrum is different.

But you're using this as a musical instrument. If it sounds the way you
want, do it.

But be aware that although most guitar amps are designed with the intention
of clipping them, most ADC designers didn't spent a lot of time worrying about
clipping behaviour because they didn't expect people to use them that way.
So you're likely to find that no two ADCs sound quite the same way when
overloaded.


I was under the impression that the primary difference is that overloading
the front end of the ADC would potentially produce digital hard clipping at
the output, that is assuming the amp sim's volume isn't set particularly low
and the input level is cranked high enough. For example, a 50 dB boost applied
to the input of an ADC vs. an analog amp. Both will clip, but my presumption
was that the ADC would produce digital hard clipping in the form of a square
waveform, whereas hard clipping in the analog amp would produce a waveform
that wasn't chopped.


The problem with clipping in the digital domain is that the resulting
square wave has harmonics all the way up to the sampling rate. That
can't happen with analogue clipping, because the lowpass input filter
will guarantee that they are suppressed well before the Nyquist rate.

Those harmonics surrounding the sampling rate alias back into the
audio band following decimation. They are nasty. Never ever allow
digital domain clipping.

d
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Mike Rivers[_2_] Mike Rivers[_2_] is offline
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Default Question about Digital vs. Analog

On 2/10/2019 2:28 PM, James Price wrote:
I was under the impression that the primary difference is that overloading
the front end of the ADC would potentially produce digital hard clipping at
the output, that is assuming the amp sim's volume isn't set particularly low
and the input level is cranked high enough.


Please, exactly what are you talking about? Hardware or software?

Yes, you can overdrive the input of an ADC and you'll get digital
clipping. This clipping occurs at the point where the guitar signal is
digitized, before it even gets to the simulation software. You
definitely want to avoid it.

For example, a 50 dB boost applied
to the input of an ADC vs. an analog amp. Both will clip, but my presumption
was that the ADC would produce digital hard clipping in the form of a square
waveform, whereas hard clipping in the analog amp would produce a waveform
that wasn't chopped.


You can clip an analog stage if you drive it hard enough. Drive it 50 dB
higher than its nominal input level and you'll get something pretty
close to a perfect square wave. When the analog stage reaches its
maximum output voltage, it can go no higher, so as long as any portion
of the cycle is above the maximum output level, it will be clipped at
that voltage.

The same thing happens with an ADC, only its maximum output level isn't
defined as a voltage, but as a binary number - the higher the voltage at
the point along the waveform where the converter takes a "snapshot," the
bigger the number. For a given word length, say 16 bits, the maximum
output, or full scale, as it's called, is when all the bits are turned
on. There isn't a 17th bit so the next successive samples that would
exceed full scale if they could are digitized at the full scale value.
And, yes, that means they're flat on top.


--
For a good time, call http://mikeriversaudio.wordpress.com


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On Sun, 10 Feb 2019 13:04:31 -0800, Robert Orban
wrote:

In article ,
says...


The problem with clipping in the digital domain is that the resulting
square wave has harmonics all the way up to the sampling rate. That
can't happen with analogue clipping, because the lowpass input filter
will guarantee that they are suppressed well before the Nyquist rate.

Those harmonics surrounding the sampling rate alias back into the
audio band following decimation. They are nasty. Never ever allow
digital domain clipping.

d


You can clip in the digital domain, but it's difficult. It requires
oversampling the clipper, and aliasing decreases quite slowly as sample rate
increases.

Current Optimod processors use a combination of oversampling and other
tricks to get an equivalent sample rate of about 10 MHz for "clipper-like"
processes. At that frequency, aliasing distortion into the audio band is
negligible compared to the desired clipping distortion (i.e. distortion that
is equivalent to that produced by an analog clipper with the same
input/output gain shape).

--Bob Orban


OK, I think I've got that. I'll work it out later in Mathcad. But what
we are talking about here is accidental clipping by simply hitting
digital max. That can never be good news.

d
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On 11/02/2019 8:28 AM, James Price wrote:


I was under the impression that the primary difference is that overloading
the front end of the ADC would potentially produce digital hard clipping at
the output, that is assuming the amp sim's volume isn't set particularly low
and the input level is cranked high enough. For example, a 50 dB boost applied
to the input of an ADC vs. an analog amp. Both will clip, but my presumption
was that the ADC would produce digital hard clipping in the form of a square
waveform, whereas hard clipping in the analog amp would produce a waveform
that wasn't chopped.


That would depend on the ADC involved and/or the analogue circuitry
before it.

I've never thought of the idea of using an ADC itself as a fuzz box. Try
it, but don't expect it to apply to any other ADC in a effect box or
audio computer interface model other than the one you've tried.

Myself, I get more pleasure out of fiddling with a guitar amp itself,
even over fuzz-boxes/distortion-pedals/whatever.

geoff
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On 11/02/2019 9:06 AM, Scott Dorsey wrote:
James Price wrote:
I was under the impression that the primary difference is that overloading
the front end of the ADC would potentially produce digital hard clipping at
the output, that is assuming the amp sim's volume isn't set particularly low
and the input level is cranked high enough. For example, a 50 dB boost applied
to the input of an ADC vs. an analog amp. Both will clip, but my presumption
was that the ADC would produce digital hard clipping in the form of a square
waveform, whereas hard clipping in the analog amp would produce a waveform
that wasn't chopped.


Clipping is clipping. Some analogue circuits will "clip softly" which is
to say they have a little gain reduction right before they come to the
clipping point. Some analogue circuits will overshoot when they clip.
Some will get stuck for a cycle or two when they clip.

All of these will result in a different spectrum. You'll still get the
odd harmonics that you get from perfect clipping, but the ratio between
them will be different and you'll get other stuff too.

People that build guitar amps think a lot about behaviour of circuits
when they clip, but most designers don't care about it because they don't
expect people will ever clip anything. Hi-fi tube amps often use splitter
circuits like the paraphase inverter or the see-saw, which you will never
see in guitar amps because they behave very badly when clipped.

When you go into clipping, you have left the normal operating envelope of
the equipment, and you have become a test pilot. Don't make any assumptions
about how anything will behave when it's clipped. If you intend on using
clipping as an effect, try it and listen.
--scott



And then there is the solid-state v. vacuum tube predominant even/odd
distortion harmonic thang, as you obliquely alluded to in your second
paragraph.

geoff

geoff
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On 11/02/2019 9:18 AM, Mike Rivers wrote:


The same thing happens with an ADC, only its maximum output level isn't
defined as a voltage, but as a binary number - the higher the voltage at
the point along the waveform where the converter takes a "snapshot," the
bigger the number. For a given word length, say 16 bits, the maximum
output, or full scale, as it's called, is when all the bits are turned
on. There isn't a 17th bit so the next successive samples that would
exceed full scale if they could are digitized at the full scale value.
And, yes, that means they're flat on top.



Cue Thekma. Ooops sorry ...

geoff


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geoff wrote:

And then there is the solid-state v. vacuum tube predominant even/odd
distortion harmonic thang, as you obliquely alluded to in your second
paragraph.


That is a useless oversimplification which is no way correct, and it
comes from an IEEE Spectrum article in the 1980s. I wish people would
stop repeating it.

That article was talking about predominant distortion at low levels
without feedback, caused by the device characteristic itself. The
thing is, we don't actually use electronics that way. We use circuits
designed to minimize distortion using techniques like local feedback
and push-pull amplification, techniques like constant current supplies.
Once you do that, the distortion spectra all change in ways that are
not so cut and dried.

And of course, you can't generalize low level distortion to clipping.
When you clip a waveform, you generate odd harmonics. Generate enough
and you get a square wave. It doesn't matter if you do it with tubes
or transistors, in the analogue domain or the digital domain. That is
what clipping does.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
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On 11/02/2019 3:49 PM, Scott Dorsey wrote:
geoff wrote:

And then there is the solid-state v. vacuum tube predominant even/odd
distortion harmonic thang, as you obliquely alluded to in your second
paragraph.


That is a useless oversimplification which is no way correct, and it
comes from an IEEE Spectrum article in the 1980s. I wish people would
stop repeating it.

That article was talking about predominant distortion at low levels
without feedback, caused by the device characteristic itself. The
thing is, we don't actually use electronics that way. We use circuits
designed to minimize distortion using techniques like local feedback
and push-pull amplification, techniques like constant current supplies.
Once you do that, the distortion spectra all change in ways that are
not so cut and dried.

And of course, you can't generalize low level distortion to clipping.
When you clip a waveform, you generate odd harmonics. Generate enough
and you get a square wave. It doesn't matter if you do it with tubes
or transistors, in the analogue domain or the digital domain. That is
what clipping does.
--scott



We are talking specifically in an electric guitar context no ? Hardly an
amp designed to minimise distortion ?

So that would be why distortion from over-driving a solid-state guitar
amp (discount 'modelling amps') is just as pleasing as that from a valve
amp then - not ?

geoff
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geoff wrote:

We are talking specifically in an electric guitar context no ? Hardly an
amp designed to minimise distortion ?

So that would be why distortion from over-driving a solid-state guitar
amp (discount 'modelling amps') is just as pleasing as that from a valve
amp then - not ?


Comparing a tube amplifier and a solid state amplifier is like comparing
apples and oranges... totally different topology, totally different output
stage. Many of the differences have little to do with the devices and
everything with how they are used. An enormous amount of the coloration from
a tube amp is in the output transformer.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
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On 12/02/2019 4:36 AM, Scott Dorsey wrote:
geoff wrote:

We are talking specifically in an electric guitar context no ? Hardly an
amp designed to minimise distortion ?

So that would be why distortion from over-driving a solid-state guitar
amp (discount 'modelling amps') is just as pleasing as that from a valve
amp then - not ?


Comparing a tube amplifier and a solid state amplifier is like comparing
apples and oranges... totally different topology, totally different output
stage. Many of the differences have little to do with the devices and
everything with how they are used. An enormous amount of the coloration from
a tube amp is in the output transformer.
--scott



So there is no truth in the old adage that distortion products of
over-driven valves are of predominantly even order harmonics which are
pleasing to the ear, as opposed to the predominantly odd-order harmonics
that resulting from the distortion from over-driving solid-state
devices, which are considered unpleasant ?

geoff
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geoff wrote: "
Cue Thekma. Ooops sorry ...

geoff "

People who have principles, and actually stand
by them, get to you that much, ehh?


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On 2/11/2019 5:31 PM, geoff wrote:
On 12/02/2019 4:36 AM, Scott Dorsey wrote:
geoffÂ* wrote:

We are talking specifically in an electric guitar context no ? Hardly an
amp designed to minimise distortion ?

So that would be why distortion from over-driving a solid-state guitar
amp (discount 'modelling amps') is just as pleasing as that from a valve
amp then - not ?


Comparing a tube amplifier and a solid state amplifier is like comparing
apples and oranges... totally different topology, totally different output
stage.Â* Many of the differences have little to do with the devices and
everything with how they are used.Â* An enormous amount of the coloration from
a tube amp is in the output transformer.
--scott



So there is no truth in the old adage that distortion products of over-driven
valves are of predominantly even order harmonics which are pleasing to the ear,
as opposed to the predominantly odd-order harmonics that resulting from the
distortion from over-driving solid-state devices, which are considered
unpleasantÂ* ?

geoff


Compare the output tube amplifier and a solid state amplifier with a scope as
you drive them into distortion. Notice how much softer the tube amp goes into
distortion than the solid state does.

Years ago I almost had a fight with my steel playing friend. He came in and ask
me to put some distortion in his amp I had built. I screamed "I've been trying,
for years to get the distortion out and you want to put it back in!"


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Scott Dorsey Scott Dorsey is offline
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geoff wrote:

So there is no truth in the old adage that distortion products of
over-driven valves are of predominantly even order harmonics which are
pleasing to the ear, as opposed to the predominantly odd-order harmonics
that resulting from the distortion from over-driving solid-state
devices, which are considered unpleasant ?


Not really.

But that article wasn't about over-driven amplifiers either, it was about
operating amplifiers within normal envelopes. Most audio designers never think
about what happens when amps are overdriven because normal audio users don't
do that.

However... just look at the spectrum of a push-pull tube amp vs. a
single-ended tube amp.... lots more second harmonic in that single-ended
amp, some of which has to do with the lack of push-pull cancellation and
some of which has to do with having all the DC on that output transformer.
The topology has more to do with it than the device.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
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gray_wolf wrote:

Compare the output tube amplifier and a solid state amplifier with a scop=
e as=20
you drive them into distortion. Notice how much softer the tube amp goes =
into=20
distortion than the solid state does.


90% of that has to do with the output transformer rather than any of
the gain stages. You can build a solid state amp with an output transformer
(like McIntosh did in the seventies) and get similarly soft clipping
behaviour. With some tinkering and a high Vcc you can even make it
behave like a tube output section pretty well.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
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geoff geoff is offline
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On 12/02/2019 3:06 PM, Scott Dorsey wrote:
geoff wrote:

So there is no truth in the old adage that distortion products of
over-driven valves are of predominantly even order harmonics which are
pleasing to the ear, as opposed to the predominantly odd-order harmonics
that resulting from the distortion from over-driving solid-state
devices, which are considered unpleasant ?


Not really.

But that article wasn't about over-driven amplifiers either, it was about
operating amplifiers within normal envelopes. Most audio designers never think
about what happens when amps are overdriven because normal audio users don't
do that.

However... just look at the spectrum of a push-pull tube amp vs. a
single-ended tube amp.... lots more second harmonic in that single-ended
amp, some of which has to do with the lack of push-pull cancellation and
some of which has to do with having all the DC on that output transformer.
The topology has more to do with it than the device.
--scott


I must have a play with the '100/70V Line' amp I'm fixing just now ....

geoff
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Phil Allison[_4_] Phil Allison[_4_] is offline
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Scott Dorsey wrote:

Notice how much softer the tube amp goes =
into distortion than the solid state does.


90% of that has to do with the output transformer rather than any of
the gain stages.



** Nothing magical about transformers, just the fact there IS one included inside the feedback loop. This limits how much feedback the designer can use before the amp becomes unstable at high frequencies to much less than with typical transformerless designs.


You can build a solid state amp with an output transformer
(like McIntosh did in the seventies) and get similarly soft clipping
behaviour.




** Some 100V line amplifiers have a transformer included in the output stage using a topology not too different from a tube amp with a single positive supply rail ( often 24VDC) connected to a CT on the primary.

The secondary may have 8ohm ( used for NFB) plus 50, 70 and 100V windings for the distributed speaker system.

Normally clipping is softish.


...... Phil




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geoff wrote:

I must have a play with the '100/70V Line' amp I'm fixing just now ....


Check out the difference between what happens when you clip the thing with
a 25 Hz wave vs. with a 1KHz wave. The behaviour of the transformer is
very clear.

A 1 KHz square wave response on those things is also quite enlightening.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
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geoff wrote:




So there is no truth in the old adage that distortion products of
over-driven valves are of predominantly even order harmonics which are
pleasing to the ear, as opposed to the predominantly odd-order harmonics
that resulting from the distortion from over-driving solid-state
devices, which are considered unpleasant ?




** With sine wave drive, the vast majority of valve output stages produce mainly 3rd harmonic distortion under high power and overdrive conditions.
The symmetrical shape of the output wave guarantees this will be the case.

Transistor amps also produce mainly 3rd harmonic under the same test conditions - with perhaps a bit more 5th and 7th as overdrive is increased.

Musical sounds consist of many frequencies at the same time. so the dominant distortion is real life is **intermodulation** between these frequencies.

Which generally sounds disgusting.



..... Phil







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On 12/02/2019 10:31 am, geoff wrote:
So there is no truth in the old adage that distortion products of
over-driven valves are of predominantly even order harmonics which are
pleasing to the ear, as opposed to the predominantly odd-order harmonics
that resulting from the distortion from over-driving solid-state
devices, which are considered unpleasantÂ* ?


The truth is that for many decades there has been *NO* reason to
overdrive a solid state amp so the question is moot. However there are
still plenty of people who like the distortion from valve amps,
especially guitarists. As an *effect* it will always have a place it seems.



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Theckhh-maah the village idiot thechh-mmmaaaah@tardsЯtheckmah
stumbled off the short bus and puked up:

People who have principles, and actually stand
by them, get to you that much, ehh?


Is being a retarded dumb**** a "principle" to you, li'l buddy? HFU. FCKWAFA!
DFRT.

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Scott Dorsey Scott Dorsey is offline
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In article , Trevor wrote:
On 12/02/2019 10:31 am, geoff wrote:
So there is no truth in the old adage that distortion products of
over-driven valves are of predominantly even order harmonics which are
pleasing to the ear, as opposed to the predominantly odd-order harmonics
that resulting from the distortion from over-driving solid-state
devices, which are considered unpleasantÂ* ?


The truth is that for many decades there has been *NO* reason to
overdrive a solid state amp so the question is moot. However there are
still plenty of people who like the distortion from valve amps,
especially guitarists. As an *effect* it will always have a place it seems.


It's not necessarily moot in some cases... because there are cases where
people are going to inadvertently overload things and it's important that
they either don't sound too bad when overloaded, or that they sound so bad
that it's an immediate wake-up call to the operator. Mike preamps in live
sound consoles are a great example.
--scott


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


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On 14/02/2019 2:26 am, Scott Dorsey wrote:
In article , Trevor wrote:
On 12/02/2019 10:31 am, geoff wrote:
So there is no truth in the old adage that distortion products of
over-driven valves are of predominantly even order harmonics which are
pleasing to the ear, as opposed to the predominantly odd-order harmonics
that resulting from the distortion from over-driving solid-state
devices, which are considered unpleasantÂÂ* ?


The truth is that for many decades there has been *NO* reason to
overdrive a solid state amp so the question is moot. However there are
still plenty of people who like the distortion from valve amps,
especially guitarists. As an *effect* it will always have a place it seems.


It's not necessarily moot in some cases... because there are cases where
people are going to inadvertently overload things and it's important that
they either don't sound too bad when overloaded, or that they sound so bad
that it's an immediate wake-up call to the operator. Mike preamps in live
sound consoles are a great example.


But I was talking about valve Vs SS amps, and the fact is for the same
money or less you buy a SS amp with ten times the power and the question
of overloading it *IS* moot compared to the valve amp with 1/10th the
power! You *COULD* overload the SS amp of course, but then you are
definitely NOT comparing the power output to a valve amp with ANY amount
of, or type of, distortion!
Sadly however there are actually people for whom the distortion caused
by overloaded SS amps is not a wake-up call. :-(



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