Feedback in audio esp wrt op-amps.

[Arny Krueger]

"Mogens V." <mogensv@NOYOUDONTvip.cybercity.dk> wrote in
message
news:46d2cfc0$0$21927$157c6196@dreader1.cybercity.dk

Arny Krueger wrote:
"Mogens V." <mogensv@NOYOUDONTvip.cybercity.dk> wrote

Right above Fig 1 this 'board' seemingly used for
measurements are mentioned, indicating they did measure
out those opamps - or maybe the player was measured as a
whole.


The analog domain circuitry in a CD player is basically
a stereo DAC, a pair of op amps, and maybe an analog
switch for muting.

Basically, yes. Sometimes I wonder about all that
electronics in some devices. The reference thingy (an
SACD, it seems) in said article seems to be loaded with
electronics. YMMV..

This is ironic, because one of the alleged benfits of DSD is supposed to be
a simplified player.

However, there are two other explanations for the apparently complexity of a
SACD player:

(1) It's a high end audio product, and the oversized collection of hardware
is supposed to convey perceived value.

(2) It's a low-volume or early production design, and has very few of the
advantages of component integration, which requires more development time,
and/or technology and expenses that only high volumes can make economically
justified.

The reason I put some faith in the papers is that most
all comments on subjective sonic performance seems to
fit with what I read elsewhere, which of cause doesn't
nessesarily make it technically valid.

There's a lot of people who say this kind of stuff, and
it appears to rock their cradle. Doesn't make it the
least bit true.

Nod. As I said, I was searching for tonal references more
than tech facts. It's for modding the analog part of
guitar processors, where a nof devices will all serve
equally well, from a tech POW.

Regrettably, the meaning of the previous paragraph seems to be hindered by a
few misspellings.

Not having the time nor the test gear, I was going more
for a matching range of subjective sonic comments.

Subjective comments are like - individual and subjective.

The
tonal/sonic 'findings' in the referred article mostly
seem to match what's been commented in here, so at least
subjectively, it's not totally off.

I fully agree with your comments on scale et al.., though
Haven't completely lost my ability to think and read
between lines..

Just trying to throw a flag on a play that seems to be way out of bounds...

Good luck with your project.

 

[Mark]

There's a lot of people who say this kind of stuff, and it appears to rock
their cradle. Doesn't make it the least bit true.

I believe there is a fundamental emotional problem some people have
with audio equipment in that they believe that simple, easy, common,
and cheap means it cannot also be good.

But that is exactly what advances in technology (like negative
feedback) strive for. With today's technology, a simple, cheap,
common, easy to design in op-amp can indeed be VERY good.

I think it is a stoicism thing.

Mark

 

[Arny Krueger]

"Mark" <makolber@yahoo.com> wrote in message
news:1188222664.582305.202940@g4g2000hsf.googlegroups.com

There's a lot of people who say this kind of stuff, and
it appears to rock their cradle. Doesn't make it the
least bit true.

I believe there is a fundamental emotional problem some
people have with audio equipment in that they believe
that simple, easy, common, and cheap means it cannot also
be good.

Agreed, and there are plenty of people who are attempting to profit by
fanning these kinds of fears.

But that is exactly what advances in technology (like
negative feedback) strive for. With today's technology,
a simple, cheap, common, easy to design in op-amp can
indeed be VERY good.

Again agreed. BTW, after looking at

http://members.cox.net/alexhardware/opa.htm

Then I noticed a reference to the author's previous article:

http://tangentsoft.net/audio/opamps.html

In this article, a wide selection of audio op amps that are generally
designed to drive normal line level circuitry were evaluated as headphone
amplifiers. <!!!!>. The tests involved loads as low as 33 ohms. The
apparent test criteria was the power supply voltage required to deliver
signals on the order of 0.5 volts into 33 ohm loads. <head shaking>.

I'm not knocking the need, but I've got a lot of questions about the
approach to testing, and the choice of parts tested for the stated purpose.

There are such thing as op-amp chips that are very appropriate for driving
headphones, none of which I see being tried.

I think it is a stoicism thing.

When I started out in audio, it took a half-a rack or so of epxensive
equipment (based on octal tubes) with a farily thick power cord to do a what
then passed for a high quality job of recording two tracks from condenser
microphones. Today, a Microtrak fits in my hand, runs off a built-in
battery for an hour or more, and does a far better technical job of doing
the same basic thing - recording and playing audio. Not everybody seems to
be able to get their head around such dramatic changes.

 

[Mogens V.]

Arny Krueger wrote:

"Mogens V." <mogensv@NOYOUDONTvip.cybercity.dk> wrote in
message
news:46d2cfc0$0$21927$157c6196@dreader1.cybercity.dk

Arny Krueger wrote:

"Mogens V." <mogensv@NOYOUDONTvip.cybercity.dk> wrote


The reason I put some faith in the papers is that most
all comments on subjective sonic performance seems to
fit with what I read elsewhere, which of cause doesn't
nessesarily make it technically valid.

There's a lot of people who say this kind of stuff, and
it appears to rock their cradle. Doesn't make it the
least bit true.


Nod. As I said, I was searching for tonal references more
than tech facts. It's for modding the analog part of
guitar processors, where a nof devices will all serve
equally well, from a tech POW.


Regrettably, the meaning of the previous paragraph seems to be hindered by a
few misspellings.

Que? not sure I understand..

Good luck with your project.

Don't worry, I'm not about substiting all opamps just because I _think_
I can get better tone. It's mostly for things like programmable
compressors build on a NE570+TL082, to be substitutd for a NE572+NE5534.
I'd like to adopt a better, more natural sounding (sideband) compressor
design without breathing artefacts, though I'd have to expect facing
some problems integrating it into this existing programmable design.
Wouldn't mind references to a good sideband compressor, though..

--
Kind regards,
Mogens V.

 

[Arny Krueger]

"Mogens V." <mogensv@NOYOUDONTvip.cybercity.dk> wrote in
message
news:46d2f814$0$21929$157c6196@dreader1.cybercity.dk

Arny Krueger wrote:
"Mogens V." <mogensv@NOYOUDONTvip.cybercity.dk> wrote in
message
news:46d2cfc0$0$21927$157c6196@dreader1.cybercity.dk

Arny Krueger wrote:

"Mogens V." <mogensv@NOYOUDONTvip.cybercity.dk> wrote


The reason I put some faith in the papers is that most
all comments on subjective sonic performance seems to
fit with what I read elsewhere, which of cause doesn't
nessesarily make it technically valid.

There's a lot of people who say this kind of stuff, and
it appears to rock their cradle. Doesn't make it the
least bit true.


Nod. As I said, I was searching for tonal references
more than tech facts. It's for modding the analog part
of guitar processors, where a nof devices will all serve
equally well, from a tech POW.


Regrettably, the meaning of the previous paragraph seems
to be hindered by a few misspellings.

Que? not sure I understand..

Good luck with your project.

Don't worry, I'm not about substiting all opamps just
because I _think_ I can get better tone. It's mostly for
things like programmable compressors build on a
NE570+TL082, to be substitutd for a NE572+NE5534. I'd
like to adopt a better, more natural sounding (sideband)
compressor design without breathing artefacts, though I'd
have to expect facing some problems integrating it into
this existing programmable design. Wouldn't mind
references to a good sideband compressor, though..

The NE570 variable gain element seems to be far more likely to create
audible effects than even just a fair op amps.

You might want to check That Corp semiconductor for their latest-greatest
VCA chips.

http://www.thatcorp.com/vcas.html

 

[Eeyore]

"Mogens V." wrote:

Arny Krueger wrote:

Good luck with your project.

Don't worry, I'm not about substiting all opamps just because I _think_
I can get better tone. It's mostly for things like programmable
compressors build on a NE570+TL082, to be substitutd for a NE572+NE5534.
I'd like to adopt a better, more natural sounding (sideband) compressor
design without breathing artefacts, though I'd have to expect facing
some problems integrating it into this existing programmable design.
Wouldn't mind references to a good sideband compressor, though..

The NE570 and 572 are fairly poor performers designed originally for telephony
IIRC. Have you looked at using dedicated high quality audio VCAs ?

Graham

 

[Scott Dorsey]

Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote:

"Mogens V." wrote:

Arny Krueger wrote:

Good luck with your project.

Don't worry, I'm not about substiting all opamps just because I _think_
I can get better tone. It's mostly for things like programmable
compressors build on a NE570+TL082, to be substitutd for a NE572+NE5534.
I'd like to adopt a better, more natural sounding (sideband) compressor
design without breathing artefacts, though I'd have to expect facing
some problems integrating it into this existing programmable design.
Wouldn't mind references to a good sideband compressor, though..

The NE570 and 572 are fairly poor performers designed originally for telephony
IIRC. Have you looked at using dedicated high quality audio VCAs ?

Or using the gain-control grid on a 6BE6! You need two of them out of
phase to deal with the linearity issues, but you need to do that with
the NE570, anyway.

THAT makes some nice VCA chips that are available from Mouser and are
good performers, with no need to parallel them and totem-pole them like
with the NE570.
--scott

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

 

[Mark]

Don't worry, I'm not about substiting all opamps just because I _think_
I can get better tone. It's mostly for things like programmable
compressors build on a NE570+TL082, to be substitutd for a NE572+NE5534.
I'd like to adopt a better, more natural sounding (sideband) compressor
design without breathing artefacts, though I'd have to expect facing
some problems integrating it into this existing programmable design.
Wouldn't mind references to a good sideband compressor, though..


Breathing effects are all about the attack and decay rates and overall

amount of compression ( not the particular op amp or VCA). For ham
radio applications consider two compressors in cascade, first a slow
AGC with 15 dB compression that acts to keep the overall level
correct. Follow that with a fast limiter or clipper with 6 dB
clipping or limiting (consider even a simple clipper here) that chops
off the peaks so you can increase the average.

This was the standard setup in radio stations, a slow AGC follwed by a
fast limiter. The slow AGC makes up for board (bored) operator errors
so that the limiter sees about the same input all the time and the
limiter does the dirty work to make audio louder by clipping or
limiting the peaks.

Since you are looking for communications quality and your SSB
transmitter probably has several % distortion anyway..., the choice of
VCA is not important.

You gotta get the time constants and ratios etc correct however.

Have fun.

Mark

 

[Mogens V.]

Scott Dorsey wrote:

Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote:

"Mogens V." wrote:


Arny Krueger wrote:


Good luck with your project.

Don't worry, I'm not about substiting all opamps just because I _think_
I can get better tone. It's mostly for things like programmable
compressors build on a NE570+TL082, to be substitutd for a NE572+NE5534.
I'd like to adopt a better, more natural sounding (sideband) compressor
design without breathing artefacts, though I'd have to expect facing
some problems integrating it into this existing programmable design.
Wouldn't mind references to a good sideband compressor, though..

The NE570 and 572 are fairly poor performers designed originally for telephony
IIRC. Have you looked at using dedicated high quality audio VCAs ?

So true! The 572 part is a bit to the better side of things.
Nope, haven't yet looked at alternatives. Just started looking into
things to improve on; the crappy compressor is first on the list.

Or using the gain-control grid on a 6BE6! You need two of them out of
phase to deal with the linearity issues

Yes, I've thought about a tube-based solution. One (more) problem is
there's no space for additional tubes in the box, so I'd have to house
them externally with signals and controlwires in and out.

but you need to do that with the NE570, anyway.

Uh oh, hadn't realized the linearity problem..
That the NE570 is hooked up for a max 30:1 ratio doesn't exactly help on
liniarity and breathing

THAT makes some nice VCA chips that are available from Mouser and are
good performers, with no need to parallel them and totem-pole them like
with the NE570.
--scott

I'm looking at the That; thanks both for mentioning it.

Actually, for guitars, I have more use of a sustain function, operating
at levels lower than, and after, the initial natural attack.
The above mentioned max 30:1 compression ratio really is useless, and
only serves to completely demolish a guitar's attack and definition,
even for the heaviest metal. Further, it makes using an envelope
follower to control parameters in proceeding effects less accurate.

It's interesting to observe that many metal players, as they grow in
musical understanding and playing capabilities, tends to drift away from
the overcompressed tone, playing with much more expression and effects
liven up, even when severe distortion is used.

--
Kind regards,
Mogens V.

 

[Mogens V.]

Mark wrote:

Don't worry, I'm not about substiting all opamps just because I _think_
I can get better tone. It's mostly for things like programmable
compressors build on a NE570+TL082, to be substitutd for a NE572+NE5534.
I'd like to adopt a better, more natural sounding (sideband) compressor
design without breathing artefacts, though I'd have to expect facing
some problems integrating it into this existing programmable design.
Wouldn't mind references to a good sideband compressor, though..



Breathing effects are all about the attack and decay rates and overall
amount of compression ( not the particular op amp or VCA)..

Yup, and WRT this, the NE570 wasn't exactly too controlable for music
processing.

Since you are looking for communications quality and your SSB
transmitter probably has several % distortion anyway..., the choice of
VCA is not important.

Ehm, nope, not for SSB apps.. it's just that NE57x was very widely used
in music applications of ye olde times, in this case a guitar processor.

--
Kind regards,
Mogens V.

 

[Mark]

On Aug 27, 4:40 pm, "Mogens V." <moge...@NOYOUDONTvip.cybercity.dk>
wrote:

Mark wrote:
Don't worry, I'm not about substiting all opamps just because I _think_
I can get better tone. It's mostly for things like programmable
compressors build on a NE570+TL082, to be substitutd for a NE572+NE5534.
I'd like to adopt a better, more natural sounding (sideband) compressor
design without breathing artefacts, though I'd have to expect facing
some problems integrating it into this existing programmable design.
Wouldn't mind references to a good sideband compressor, though..

Breathing effects are all about the attack and decay rates and overall
amount of compression ( not the particular op amp or VCA)..

Yup, and WRT this, the NE570 wasn't exactly too controlable for music
processing.

Since you are looking for communications quality and your SSB
transmitter probably has several % distortion anyway..., the choice of
VCA is not important.

Ehm, nope, not for SSB apps.. it's just that NE57x was very widely used
in music applications of ye olde times, in this case a guitar processor.

--
Kind regards,
Mogens V.

OK I'm sorry I mis-understood you then...

What did you mean by _sideband_ here....

"I'd like to adopt a better, more natural sounding (sideband)
compressor design without breathing artefacts....."

Mark

 

[Mr.T]

"Mark" <makolber@yahoo.com> wrote in message
news:1188265519.892253.228370@19g2000hsx.googlegroups.com...

OK I'm sorry I mis-understood you then...

What did you mean by _sideband_ here....

"I'd like to adopt a better, more natural sounding (sideband)
compressor design without breathing artefacts....."

I would guess he actually meant side-chain.
I'm pretty sure he wasn't talking about amateur radio anyway

MrT.

 

[Mogens V.]

Mr.T wrote:

"Mark" <makolber@yahoo.com> wrote in message
news:1188265519.892253.228370@19g2000hsx.googlegroups.com...

OK I'm sorry I mis-understood you then...

What did you mean by _sideband_ here....

"I'd like to adopt a better, more natural sounding (sideband)
compressor design without breathing artefacts....."


I would guess he actually meant side-chain.
I'm pretty sure he wasn't talking about amateur radio anyway

MrT.

yup, maybe I used the wrong description, so to be more verbal:
I mean a compressor not directly in the signal path, but rather where
the compressed part is summed onto the direct signal, leaving the
original dynamics untouched, so the compressed part 'blends in' only
after the initial attact/decay part, thus effectively acting as a
sustain function.

This is very much needed when creating guitar sound. Maybe mostly OT in
this discussion, but still..
AFAIU, many 'normal' in-line (guitar) solid state compressors tend to
create third harmonic distortion at the somewhat fast attack times
mostly used for guitars, plus some breathing/pumping (design problem).
At least for my own taste, I'd prefer using and preserving the natural
dynamic envelope of the instrument, coupled with the ability to prolong
the sustain part of the envelope, with a somehat natural release.
It allows for a much more expressive playing style.

Of cause I could use some external ADSR-based device for more control,
but this doesn't really fit with my otherwise programmable rack - at
least it won't fit my finances hense my attempt to rework it.
My preamp only has comp.ratio, threshold and level parameters, so this
is what I'm left with for another design.

--
Kind regards,
Mogens V.

 

[Arny Krueger]

"Mr.T" <MrT@home> wrote in message
news:46d38a63$0$13845$afc38c87@news.optusnet.com.au

"Mark" <makolber@yahoo.com> wrote in message
news:1188265519.892253.228370@19g2000hsx.googlegroups.com...
OK I'm sorry I mis-understood you then...

What did you mean by _sideband_ here....

"I'd like to adopt a better, more natural sounding
(sideband) compressor design without breathing
artefacts....."

I would guess he actually meant side-chain.

That was my interpretation.

 

[Mark]

I would guess he actually meant side-chain.
I'm pretty sure he wasn't talking about amateur radio anyway

MrT.

yup, maybe I used the wrong description, so to be more verbal:
I mean a compressor not directly in the signal path, but rather where
the compressed part is summed onto the direct signal, leaving the
original dynamics untouched, so the compressed part 'blends in' only
after the initial attact/decay part, thus effectively acting as a
sustain function.
...

OK that's not sidechain either.... sidechain is when one audio signal
is applied to the control part of the compressor and is used to
controal another audio signal. i.e announcers voice used to lower the
gain of (or duck) the music is the usual example.

What you are asking for is done with an ordinary compresser and then
use an ordinary mixer to combine the wet (compressed) and dry
(original uncompressed) signal. You can use the two faders of the
mixer channels to vary the amount of wet / dry to your taste.

Mark