1. it amazes me how the digital era of audio appears to be going, I saw a
report recently of a new Logitech speaker that was getting rave reviews
saying "it has no distortion at all" reading the reviews it became clear
they where refering to be able to play at max vol with an ipod as the input
without it distorting....a look at logitech.com found me the spec 20wrms @
10%thd ! sheesh! that got me wondering too about the mp3 source, compared to
the orig CD wav what wouth the thd of the mp3 work out at ? can it be
measured ?


2. a few yrs back I got samples from Analog Devices of a low noise audio
switch and a dc controlled vol chip ( 0.002% thd ) I knocked them together
with a couple of 5532's and have been enjoying them since ( from tv/dvd or
Technics CD into 4 x 75wrms mosfet amps and onto a pair of ILP TL4's,
ground/door and window shaking stuff and very clear, or so I thought.....
last week I got hold of samples of National's LM4562 and replaced the
5532's, the attack on drums is now much better and everything sounds
tighter. As it was chucked together I used 7815 & 7915 regs, I had a trouble
with rf on the -ve rail which could be heard as a faint hiss, so I thought
whilst it's in bits I'll go over the power supply , no need! it's now
silent, better rejection ? anyone else tried these LM4562's ?

Pete

Pete Cross wrote:
1. it amazes me how the digital era of audio appears to be going, I saw a
report recently of a new Logitech speaker that was getting rave reviews
saying "it has no distortion at all" reading the reviews it became clear
they where refering to be able to play at max vol with an ipod as the input
without it distorting....a look at logitech.com found me the spec 20wrms @
10%thd ! sheesh! that got me wondering too about the mp3 source, compared to
the orig CD wav what wouth the thd of the mp3 work out at ? can it be
measured ?

I'm not a bit surprised that a cheap computer 'speaker would be reviewed
as having no distortion. I assume the review was in a computer journal
or General Public publication, and not an engineering journal. Reviews
of technical products by non-technical journalists often make these
stupid statements.

MP3 sources generally don't have any worse THD figures than non
data-reduced formats for one reason:- THD is normally measured by
injecting a single tone into the Device Under Test, then measuring the
output with the tone removed by a very deep and tight notch filter.
Everything else is deemed to be distortion (plus noise). MP3 encoding
with a single tone is very good, and won't show any artefacts, as the
entire bit budget can go towards coding that tone perfectly. Things get
a little more difficult when encoding multiple tones, as the bit budget
has to be spread over more information. There are tests available that
inject multiple tones, null them all out separately and measure what's
left. These tests, however have shown that the measured result is very
dependant on how many tones, what levels of each tone etc. As far as I
know there's no standard test that will assess distortion for an MP3
encoder/decoder.

As an aside, if you play a rapid sliding tone (20-20k in 2 seconds)at
constant level into an encoder, then decode the result, you will get
something out that looks very strange. There are great holes in the
frequency response, and you would think it was broken. I did this test
for the French Post Office some years ago when they were assessing MP2
ISDN codecs. They had this standard test they wanted to apply to the
codecs even though they knew it was pretty stupid.

S.

"Serge Auckland" wrote in message
...
Pete Cross wrote:
1. it amazes me how the digital era of audio appears to be going, I saw
a
report recently of a new Logitech speaker that was getting rave reviews
saying "it has no distortion at all" reading the reviews it became clear
they where refering to be able to play at max vol with an ipod as the
input
without it distorting....a look at logitech.com found me the spec 20wrms
@
10%thd ! sheesh! that got me wondering too about the mp3 source,
compared to
the orig CD wav what wouth the thd of the mp3 work out at ? can it be
measured ?

I'm not a bit surprised that a cheap computer 'speaker would be reviewed
as having no distortion. I assume the review was in a computer journal
or General Public publication, and not an engineering journal. Reviews
of technical products by non-technical journalists often make these
stupid statements.

MP3 sources generally don't have any worse THD figures than non
data-reduced formats for one reason:- THD is normally measured by
injecting a single tone into the Device Under Test, then measuring the
output with the tone removed by a very deep and tight notch filter.
Everything else is deemed to be distortion (plus noise). MP3 encoding
with a single tone is very good, and won't show any artefacts, as the
entire bit budget can go towards coding that tone perfectly. Things get
a little more difficult when encoding multiple tones, as the bit budget
has to be spread over more information. There are tests available that
inject multiple tones, null them all out separately and measure what's
left. These tests, however have shown that the measured result is very
dependant on how many tones, what levels of each tone etc. As far as I
know there's no standard test that will assess distortion for an MP3
encoder/decoder.

As an aside, if you play a rapid sliding tone (20-20k in 2 seconds)at
constant level into an encoder, then decode the result, you will get
something out that looks very strange. There are great holes in the
frequency response, and you would think it was broken. I did this test
for the French Post Office some years ago when they were assessing MP2
ISDN codecs. They had this standard test they wanted to apply to the
codecs even though they knew it was pretty stupid.

S.

I noticed a similar effect yrs back when I got a Sony CDman , I stuck my
Alan Parsons sound check cd in and on the sweep freq test it sounded ok till
just past 5KHz when all sorts of harmonics where added, it was due to the cd
spinning at 4x for the read ahead buffer ( anti jog ),must have been sampled
at too low a freq, if you turn off the anti jog it plays fine.

Pete

On Tue, 20 Feb 2007 15:31:37 -0000, Pete Cross wrote:

I noticed a similar effect yrs back when I got a Sony CDman , I stuck my
Alan Parsons sound check cd in and on the sweep freq test it sounded ok till
just past 5KHz when all sorts of harmonics where added, it was due to the cd
spinning at 4x for the read ahead buffer ( anti jog ),must have been sampled
at too low a freq, if you turn off the anti jog it plays fine.

It wasn't from reading the disk at 4x. Reading data at 1x or 200x is
reading the same data. As you also surmised, sampling at too low a sample
rate will cause all kinds of distortion once you get past the nyquist
frequency.

AZ Nomad wrote:

On Tue, 20 Feb 2007 15:31:37 -0000, Pete Cross wrote:


I noticed a similar effect yrs back when I got a Sony CDman , I stuck my
Alan Parsons sound check cd in and on the sweep freq test it sounded ok till
just past 5KHz when all sorts of harmonics where added, it was due to the cd
spinning at 4x for the read ahead buffer ( anti jog ),must have been sampled
at too low a freq, if you turn off the anti jog it plays fine.


It wasn't from reading the disk at 4x. Reading data at 1x or 200x is
reading the same data. As you also surmised, sampling at too low a sample
rate will cause all kinds of distortion once you get past the nyquist
frequency.

I thought that the Sony compressed the data before loading the buffer
then uncompressed it on reading from the buffer, because memory was
expensive in the second millennium. Of course, I may have got hold of
the wrong end of the stick again.

--
Eiron.

On Tue, 20 Feb 2007 17:47:31 +0000, Eiron wrote:


AZ Nomad wrote:

On Tue, 20 Feb 2007 15:31:37 -0000, Pete Cross wrote:


I noticed a similar effect yrs back when I got a Sony CDman , I stuck my
Alan Parsons sound check cd in and on the sweep freq test it sounded ok till
just past 5KHz when all sorts of harmonics where added, it was due to the cd
spinning at 4x for the read ahead buffer ( anti jog ),must have been sampled
at too low a freq, if you turn off the anti jog it plays fine.


It wasn't from reading the disk at 4x. Reading data at 1x or 200x is
reading the same data. As you also surmised, sampling at too low a sample
rate will cause all kinds of distortion once you get past the nyquist
frequency.

I thought that the Sony compressed the data before loading the buffer
then uncompressed it on reading from the buffer, because memory was
expensive in the second millennium. Of course, I may have got hold of
the wrong end of the stick again.

"Eiron" wrote in message

AZ Nomad wrote:

On Tue, 20 Feb 2007 15:31:37 -0000, Pete Cross
wrote:
I noticed a similar effect yrs back when I got a Sony
CDman , I stuck my Alan Parsons sound check cd in and
on the sweep freq test it sounded ok till just past
5KHz when all sorts of harmonics where added, it was
due to the cd spinning at 4x for the read ahead buffer
( anti jog ),must have been sampled at too low a freq, if you turn off
the anti jog it plays fine.


It wasn't from reading the disk at 4x. Reading data at
1x or 200x is reading the same data. As you also
surmised, sampling at too low a sample rate will cause
all kinds of distortion once you get past the nyquist
frequency.

http://www.pcavtech.com/play-rec/Pan_SL-S220/index.htm

Note the adverse effect on IM and frequency response when the shock
resistance feature was enabled.

I thought that the Sony compressed the data before
loading the buffer then uncompressed it on reading from
the buffer, because memory was expensive in the second
millennium.

I was under the impression that in the old days the buffer was not RAM, but
CCD.

"Pete Cross" wrote in message


1. it amazes me how the digital era of audio appears to
be going, I saw a report recently of a new Logitech
speaker that was getting rave reviews saying "it has no
distortion at all" reading the reviews it became clear
they where refering to be able to play at max vol with an
ipod as the input without it distorting....a look at
logitech.com found me the spec 20wrms @ 10%thd ! sheesh!
that got me wondering too about the mp3 source, compared
to the orig CD wav what wouth the thd of the mp3 work out
at ? can it be measured ?

You're making a very common mistake when you read that spec. Does this
equipment have 10% THD as typically used? Probably not. There's a
long-standing (and self-defeating) tradition of rating the power of
equipment in this class @ 10% THD. This practice boosts the number of watts,
that's all. Basically, the electronics are clipping like crazy because the
gain was turned too high. Back of the volume to typical levels and the THD
might be very low.


2. a few yrs back I got samples from Analog Devices of a
low noise audio switch and a dc controlled vol chip (
0.002% thd ) I knocked them together with a couple of
5532's and have been enjoying them since ( from tv/dvd or
Technics CD into 4 x 75wrms mosfet amps and onto a pair
of ILP TL4's, ground/door and window shaking stuff and
very clear, or so I thought..... last week I got hold of
samples of National's LM4562 and replaced the 5532's, the
attack on drums is now much better and everything sounds
tighter.

Anybody who thinks that a LM4562 sounds better than a NE5532, both in
well-designed circuits, is suffering from specificaion-induced
constructor's ear. They are both free of audible distortion unless someone
screws up the design.

As it was chucked together I used 7815 & 7915
regs, I had a trouble with rf on the -ve rail which could
be heard as a faint hiss, so I thought whilst it's in
bits I'll go over the power supply , no need! it's now
silent, better rejection ?

More than likely you screwed up the design by not properly bypassing the
5532 power pins in the origional design. Conventional wisdom is that a
suitable cap (classic 0.05 uF ceramic for example) between the power supply
pins will settle them down.

More than likely National idiot-proofed the 4562s.

anyone else tried these LM4562's ?

The probable justification for National coming out with the 4562 was the
fact that 5532s were thoroughly commoditized. Too many people making them
and selling them for highly competitive prices.

"Arny Krueger" wrote in message
...
"Pete Cross" wrote in message


1. it amazes me how the digital era of audio appears to
be going, I saw a report recently of a new Logitech
speaker that was getting rave reviews saying "it has no
distortion at all" reading the reviews it became clear
they where refering to be able to play at max vol with an
ipod as the input without it distorting....a look at
logitech.com found me the spec 20wrms @ 10%thd ! sheesh!
that got me wondering too about the mp3 source, compared
to the orig CD wav what wouth the thd of the mp3 work out
at ? can it be measured ?

You're making a very common mistake when you read that spec. Does this
equipment have 10% THD as typically used? Probably not. There's a
long-standing (and self-defeating) tradition of rating the power of
equipment in this class @ 10% THD. This practice boosts the number of
watts,
that's all. Basically, the electronics are clipping like crazy because the
gain was turned too high. Back of the volume to typical levels and the
THD
might be very low.


2. a few yrs back I got samples from Analog Devices of a
low noise audio switch and a dc controlled vol chip (
0.002% thd ) I knocked them together with a couple of
5532's and have been enjoying them since ( from tv/dvd or
Technics CD into 4 x 75wrms mosfet amps and onto a pair
of ILP TL4's, ground/door and window shaking stuff and
very clear, or so I thought..... last week I got hold of
samples of National's LM4562 and replaced the 5532's, the
attack on drums is now much better and everything sounds
tighter.

Anybody who thinks that a LM4562 sounds better than a NE5532, both in
well-designed circuits, is suffering from specificaion-induced
constructor's ear. They are both free of audible distortion unless
someone
screws up the design.

As it was chucked together I used 7815 & 7915
regs, I had a trouble with rf on the -ve rail which could
be heard as a faint hiss, so I thought whilst it's in
bits I'll go over the power supply , no need! it's now
silent, better rejection ?

More than likely you screwed up the design by not properly bypassing the
5532 power pins in the origional design. Conventional wisdom is that a
suitable cap (classic 0.05 uF ceramic for example) between the power
supply
pins will settle them down.

More than likely National idiot-proofed the 4562s.

anyone else tried these LM4562's ?

The probable justification for National coming out with the 4562 was the
fact that 5532s were thoroughly commoditized. Too many people making them
and selling them for highly competitive prices.



I did indeed solder caps across the supply , in fact soldered directly to
the ic pins as it's advised to place them as near the chip as poss.

The LM's have a much higher slew rate than the 5532's and it is my opinion
that this has made an audible improvement, but will accept that some may be
imagination running wild, but then so do others if you google for lm4562.

As for saying National idiot proofed them, what are you inferring ? I take
offence to that comment, maybe you didn't mean that though......

Pete