10% THD?

[[email protected]]

Are they serious?

http://av.jvc.com/product.jsp?modelId=MODL027647&pathId=5&page=2
"100 watts per channel, 8 ohms at 1kHz, with 10% THD"

10% THD sounds like a lot.

Michael

 

[BobG]

But the waveform that gets clipped and produces the 10% distortion
probably occurs less than 1% of the time... when the car crashes or
the tank cannon fires, etc, so you probably cant tell if the KaBoom!
is distorted or not... 99.9% of people have never heard a live tank
cannon at a range of less than several miles anyway.

 

[[email protected]]

But the waveform that gets clipped and produces the 10% distortion
probably occurs less than 1% of the time... when the car crashes or
the tank cannon fires, etc, so you probably cant tell if the KaBoom!
is distorted or not... 99.9% of people have never heard a live tank
cannon at a range of less than several miles anyway.

Well, for nearly the same price ($130 at Wal-Mart), you can get this
instead:

http://www.sherwoodusa.com/prod_rd6500.html

"100 Watts per Channel x 2 in Stereo Mode with less than 0.9% THD,
40 Hz-20 kHz, 6 Ohms"

The THD for a range 40Hz-20kHz should be greater (summed) than the THD
for a single frequency (1 kHz in the JVC above), right?

Michael

 

[Eeyore]

Are they serious?

http://av.jvc.com/product.jsp?modelId=MODL027647&pathId=5&page=2
"100 watts per channel, 8 ohms at 1kHz, with 10% THD"

10% THD sounds like a lot.

Pretty standard figure for quoting watts for in car entertainment
equipment.

Never previously seen it used for any home audio though. It's probably ~
60-70W at some acceptable THD figure.

Graham

 

[Eeyore]

Well, for nearly the same price ($130 at Wal-Mart), you can get this
instead:

http://www.sherwoodusa.com/prod_rd6500.html

"100 Watts per Channel x 2 in Stereo Mode with less than 0.9% THD,
40 Hz-20 kHz, 6 Ohms"

The THD for a range 40Hz-20kHz should be greater (summed) than the THD
for a single frequency (1 kHz in the JVC above), right?

THD typically increases with frequency (due to falling open-loop gain) so
a 20kHz figure will be more than a 1 kHz figure.

Graham

 

[[email protected]]

THD typically increases with frequency (due to falling open-loop gain) so
a 20kHz figure will be more than a 1 kHz figure.

Graham

And the THD should be higher at 4 or 6 ohms than at 8, right?

M

 

[BobG]

I dont think you can see the difference between 0.1% and 3% distortion
in a sine wave. Scope aint good enough. But 'visible clipping' is
about 10%, and is surprisingly inaudible. Try it yourself. Get a scope
and a cd player and a smallish amp and a speaker. View amp output on
scope. Turn up till you see visible clipping. Compare sound with
clipping to sound without clipping.

 

[Eeyore]

And the THD should be higher at 4 or 6 ohms than at 8, right?

That would be normal.

Graham

 

[Eeyore]

I dont think you can see the difference between 0.1% and 3% distortion
in a sine wave.

Yes you can.

Graham

 

[Eeyore]

But 'visible clipping' is
about 10%, and is surprisingly inaudible.

Absolute nonsense. You can easily see clipping on a sinewave on a scope at
less than 1% and it's CLEARLY audible due to the high harmonic content.

Graham

 

[[email protected]]

Absolute nonsense. You can easily see clipping on a sinewave on a scope at
less than 1% and it's CLEARLY audible due to the high harmonic content.

Graham

Perhaps you have better ears than the rest of us. ;-)

There's a cellphone ringtone that supposedly only teenagers can hear,
no one over thirty - so if they get a call, their parents/teachers are
none the wiser.

Michael

 

[Phil Allison]

"BobG"

I dont think you can see the difference between 0.1% and 3% distortion
in a sine wave. Scope aint good enough. But 'visible clipping' is
about 10%, and is surprisingly inaudible. Try it yourself. Get a scope
and a cd player and a smallish amp and a speaker. View amp output on
scope. Turn up till you see visible clipping. Compare sound with
clipping to sound without clipping.

** Might be almost true for small, SE tube amplifiers with zero negative
feedback.

Their very soft rounding to the wave crests is not easy so easy to notice
compared to typical hard peak clipping seen with all high feedback
amplifiers - particularly with 100 / 120 Hz modulation added from an
unregulated supply.

I can hear that when the THD meter says it is only 0.5 %.



..... Phil

 

[Jon Slaughter]

But the waveform that gets clipped and produces the 10% distortion
probably occurs less than 1% of the time... when the car crashes or
the tank cannon fires, etc, so you probably cant tell if the KaBoom!
is distorted or not... 99.9% of people have never heard a live tank
cannon at a range of less than several miles anyway.

At least not more than once

 

[BobG]

� �I have seen 2% THD described as sounding like a barrel of nails in a
cement mixer.

=============================
But in court, this would be objected to as hearsay. We have all heard
horrible distorted clipped hash coming from and amp, but was that .5%,
5%, or 50% THD we were hearing at the time? Anyone can hear a diff in
an AB comparison with a graphic EQ in and out, but few can characteris
it quantatatively and within about an octave. Unless they have a
couple decades experience in live sound reinforcement like me and a
couple of buddies. They could win a bet in a bar if you took in a
signal generator and a spectrum analyzer. Perfect pitch.

 

[Bob Eld]

Are they serious?

http://av.jvc.com/product.jsp?modelId=MODL027647&pathId=5&page=2
"100 watts per channel, 8 ohms at 1kHz, with 10% THD"

10% THD sounds like a lot.

Michael

It is a lot. Most likely a misprint. Nobody in their right mind would spec.
an amplifier with that distortion nor would they rate an amplifier at its
clipping level as has been suggested.

Since getting less than one percent even less than 0.1% THD is trivial these
days with modern semiconductor circuitry it would seem that this spec sheet
is probably in error.

Most likely the printer or web master left out a decimal point and nobody
caught it. Call JVC and ask.

 

[[email protected]]

It is a lot. Most likely a misprint. Nobody in their right mind would spec.
an amplifier with that distortion nor would they rate an amplifier at its
clipping level as has been suggested.

Since getting less than one percent even less than 0.1% THD is trivial these
days with modern semiconductor circuitry it would seem that this spec sheet
is probably in error.

Most likely the printer or web master left out a decimal point and nobody
caught it. Call JVC and ask.

I downloaded the manual, and it also has 10% THD...
http://resources.jvc.com/Resources/00/00/90/LVT1507-001A.pdf

Support info:
http://support.jvc.com/consumer/support/index.jsp

I called their 800 number, and heard an amazingly distorted
recording. Maybe distortion is company policy? ;-)

I'll try e-mailing them (but won't hold my breath).

Well, if it does end up a mistake, this would be a pretty good
product...
http://www.walmart.com/catalog/product.do?product_id=5301826

Thanks,

Michael

 

[[email protected]]

I downloaded the manual, and it also has 10% THD...http://resources.jvc.com/Resources/00/00/90/LVT1507-001A.pdf

Support info:http://support.jvc.com/consumer/support/index.jsp

I called their 800 number, and heard an amazingly distorted
recording. Maybe distortion is company policy? ;-)

I'll try e-mailing them (but won't hold my breath).

Well, if it does end up a mistake, this would be a pretty good
product...http://www.walmart.com/catalog/product.do?product_id=5301826

Thanks,

Michael

I called them again (the phone lines were clear this time).

Confirmed that, yes, it is 10%. (Tech guy asked his supervisor).

okay then...

Either way, the manual said 8 ohm to 16 ohm impedance only... I was
thinking of using the 4-ohm subwoofer speakers I got (great deal on
car audio) that I currently use on my Onkyo.

Oh well..

"Nobody in their right mind..." ha ha ha.

Thanks guys

M

 

[BobG]

Absolute nonsense. You can easily see clipping on a sinewave on a scope at
less than 1% and it's CLEARLY audible due to the high harmonic content.

Graham

============================================================
Lets generate a test waveform with 1khz fundamental and 3% of 3khz...
formula is something like wave[n]=350.0*sin(twopi*n/1024.0) + (350.0
* 0.03)*sin(twopi*3.0*n/1024.0); I'm using ampl of 350 because I'm
plotting 1024*768. You agree this amplitude of 3rd harmonic will give
3% THD?

 

[Phil Allison]

"BobG"


** Hey Bob,

take a breath - you are not talking about the same topic as others here !!

Peak clipping ( = hard clipping ) of a CONTINUOUS sine wave is VERY audible,
even at low percentages. The harmonics generated go up to 5, 7, 9 and 11
times the fundamental - if they fall in the range of 1 to 5 kHz their
presence is obvious us to anyone who is not deaf.

OTOH - occasional transient clipping of a music or speech signals is
virtually inaudible, specially if each clipping event is under 2mS
duration. Such occasional transients may be clipped at high percentages of
their unclipped amplitude and still remain hidden to listeners.

Some power amplifiers have fast acting signal clipping indicators ( ie the
Crown IOC system) and it is easily demonstrated that the LED clipping light
will flicker regularly on normal music program WELL before any listener
can hear a problem.




...... Phil

 

[BobG]

** Hey Bob,

take a breath - �you are not talking about the same topic as others here !!

==============================================
I claimed that one cannot see 3% distortion in a sine wave on a scope.
I got a response that this is utter nonsense, and its easy to see 1%
THD on a scope. So I want to synthesize a waveform with fundamental of
amplitude X and 3rd harmonic down at 0.03X. Then I will plot it and
see for myself if in fact 3% is easily visible and my claim was utter
nonsense. Of course, I'll be using a computer monitor with about 3
times the vertical resolution of most scopes, but that should just
make the distorion easier to see.... I'm making the test harder for
myself. I wouldnt want anyone to say my experiment was biased in favor
of my claim. Just trying to defend myself against the assertion that I
have spoken utter nonsense.