The quietest audio op-amp with ultra-low THD

E

Eeyore

Guest
National's LME49710/20/40 amd LM4562 seem to have the best figures at
2.5nV/sqrt Hz but in a practical circuit I found the venerable NE5534
with its 3.5 nV/sqrt Hz was quieter, presumably due to lower input noise
current in that particular configuration.

The LMEs also have insanely low THD
RL = 600ohms 0.00003% (typ)

http://www.national.com/pf/LM/LME49710.html
http://www.national.com/pf/LM/LM4562.html

Does anyone know of anything better without sacrificing unity gain
stability or THD ?

Graham
 
Eeyore wrote:
National's LME49710/20/40 amd LM4562 seem to have the best figures at
2.5nV/sqrt Hz but in a practical circuit I found the venerable NE5534
with its 3.5 nV/sqrt Hz was quieter, presumably due to lower input noise
current in that particular configuration.

The LMEs also have insanely low THD
RL = 600ohms 0.00003% (typ)

http://www.national.com/pf/LM/LME49710.html
http://www.national.com/pf/LM/LM4562.html

Does anyone know of anything better without sacrificing unity gain
stability or THD ?
Click to expand...
Graham,

What resistance values are you assuming? Not one month ago, in this
very boutique, I posted a link to a new part with some really cute
specs--the ADA4898-1.

http://www.analog.com/static/imported-files/Data_Sheets/ADA4898-1.pdf

I gather it's probably intended for lower source resistances than yours,
but its combination of low eN and low Cin is amazing.

Cheers,

Phil Hobbs
 
Phil Hobbs wrote:

Eeyore wrote:
National's LME49710/20/40 amd LM4562 seem to have the best figures at
2.5nV/sqrt Hz but in a practical circuit I found the venerable NE5534
with its 3.5 nV/sqrt Hz was quieter, presumably due to lower input noise
current in that particular configuration.

The LMEs also have insanely low THD
RL = 600ohms 0.00003% (typ)

http://www.national.com/pf/LM/LME49710.html
http://www.national.com/pf/LM/LM4562.html

Does anyone know of anything better without sacrificing unity gain
stability or THD ?


What resistance values are you assuming? Not one month ago, in this
very boutique, I posted a link to a new part with some really cute
specs--the ADA4898-1.

http://www.analog.com/static/imported-files/Data_Sheets/ADA4898-1.pdf

I gather it's probably intended for lower source resistances than yours,
but its combination of low eN and low Cin is amazing.
Click to expand...
Yes, my source resistance may dominate. It's a new module for SSL 4000E/G
professional sound mixing desks to convert the 'channel buckets' into a
monitor desk for Digital Audio Workstations. I was shocked at how high their
mix resistor values were (15k). Crikey, even at Studiomaster in the latter
days I was using 4k7 !

It's certainly amazingly quiet though.

I'm not familiar with the THD being quoted in dBc though. Can you assist there
?

Graham
 
On Sun, 21 Sep 2008 21:51:38 +0100, in sci.electronics.design "john
jardine" <john.jardine@idnet.co.uk> wrote:

"Eeyore" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:48D6A215.52D62814@hotmail.com...
National's LME49710/20/40 amd LM4562 seem to have the best figures at
2.5nV/sqrt Hz but in a practical circuit I found the venerable NE5534
with its 3.5 nV/sqrt Hz was quieter, presumably due to lower input noise
current in that particular configuration.

The LMEs also have insanely low THD
RL = 600ohms 0.00003% (typ)

http://www.national.com/pf/LM/LME49710.html
http://www.national.com/pf/LM/LM4562.html

Does anyone know of anything better without sacrificing unity gain
stability or THD ?

Graham


Not got round to using it yet but the ADA4899 looks tasty. 1nV, 0.7ppm,
600MHz.

Open the window, more shit flies in.
Click to expand...
600MHz is not required for audio, only audiophools

martin
 
On Sun, 21 Sep 2008 21:55:34 +0100, Eeyore
<rabbitsfriendsandrelations@hotmail.com> wrote:

Phil Hobbs wrote:

Eeyore wrote:
National's LME49710/20/40 amd LM4562 seem to have the best figures at
2.5nV/sqrt Hz but in a practical circuit I found the venerable NE5534
with its 3.5 nV/sqrt Hz was quieter, presumably due to lower input noise
current in that particular configuration.

The LMEs also have insanely low THD
RL = 600ohms 0.00003% (typ)

http://www.national.com/pf/LM/LME49710.html
http://www.national.com/pf/LM/LM4562.html

Does anyone know of anything better without sacrificing unity gain
stability or THD ?


What resistance values are you assuming? Not one month ago, in this
very boutique, I posted a link to a new part with some really cute
specs--the ADA4898-1.

http://www.analog.com/static/imported-files/Data_Sheets/ADA4898-1.pdf

I gather it's probably intended for lower source resistances than yours,
but its combination of low eN and low Cin is amazing.

Yes, my source resistance may dominate. It's a new module for SSL 4000E/G
professional sound mixing desks to convert the 'channel buckets' into a
monitor desk for Digital Audio Workstations. I was shocked at how high their
mix resistor values were (15k). Crikey, even at Studiomaster in the latter
days I was using 4k7 !

It's certainly amazingly quiet though.

I'm not familiar with the THD being quoted in dBc though. Can you assist there
?

Graham
Click to expand...

15K? Sounds like jfet turf.

John
 
On Sun, 21 Sep 2008 22:40:53 +0100, in sci.electronics.design "john
jardine" <john.jardine@idnet.co.uk> wrote:

"Martin Griffith" <mart_in_medina@yah00.es> wrote in message
news:3fedd4lm06iecmu0a2oduiekqp0oasa42c@4ax.com...
On Sun, 21 Sep 2008 21:51:38 +0100, in sci.electronics.design "john
jardine" <john.jardine@idnet.co.uk> wrote:


"Eeyore" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:48D6A215.52D62814@hotmail.com...
National's LME49710/20/40 amd LM4562 seem to have the best figures at
2.5nV/sqrt Hz but in a practical circuit I found the venerable NE5534
with its 3.5 nV/sqrt Hz was quieter, presumably due to lower input
noise
current in that particular configuration.

The LMEs also have insanely low THD
RL = 600ohms 0.00003% (typ)

http://www.national.com/pf/LM/LME49710.html
http://www.national.com/pf/LM/LM4562.html

Does anyone know of anything better without sacrificing unity gain
stability or THD ?

Graham


Not got round to using it yet but the ADA4899 looks tasty. 1nV, 0.7ppm,
600MHz.

Open the window, more shit flies in.
600MHz is not required for audio, only audiophools

martin

Yes.
I was thinking more of it allowing a gain of say x5000 to 100kHz. The chip's
low Vos allowing this in one hit.

A good audio mic at 100KHz and 70dB+ gain, what on earth are you are
Click to expand...
you recording?

martin
 
John Larkin wrote:

Eeyore wrote:
Phil Hobbs wrote:
Eeyore wrote:
National's LME49710/20/40 amd LM4562 seem to have the best figures at
2.5nV/sqrt Hz but in a practical circuit I found the venerable NE5534
with its 3.5 nV/sqrt Hz was quieter, presumably due to lower input noise
current in that particular configuration.

The LMEs also have insanely low THD
RL = 600ohms 0.00003% (typ)

http://www.national.com/pf/LM/LME49710.html
http://www.national.com/pf/LM/LM4562.html

Does anyone know of anything better without sacrificing unity gain
stability or THD ?


What resistance values are you assuming? Not one month ago, in this
very boutique, I posted a link to a new part with some really cute
specs--the ADA4898-1.

http://www.analog.com/static/imported-files/Data_Sheets/ADA4898-1.pdf

I gather it's probably intended for lower source resistances than yours,
but its combination of low eN and low Cin is amazing.

Yes, my source resistance may dominate. It's a new module for SSL 4000E/G
professional sound mixing desks to convert the 'channel buckets' into a
monitor desk for Digital Audio Workstations. I was shocked at how high their
mix resistor values were (15k). Crikey, even at Studiomaster in the latter
days I was using 4k7 !

It's certainly amazingly quiet though.

I'm not familiar with the THD being quoted in dBc though. Can you assist there ?

15K? Sounds like jfet turf.
Click to expand...
Depends on whose jfet !

The existing bus amp uses an LM394 and then destroys the noise performance by
following it with a -6dB 5534 stage.

The worst of all worlds. The bus mix amp will clip before its buffer and the noise
figure goes to hell.

SSL weren't noted for the best audio electronics.

Graham
 
Martin Griffith wrote:

"john jardine" <john.jardine@idnet.co.uk> wrote:
"Eeyore" <rabbitsfriendsandrelations@hotmail.com> wrote in message

National's LME49710/20/40 amd LM4562 seem to have the best figures at
2.5nV/sqrt Hz but in a practical circuit I found the venerable NE5534
with its 3.5 nV/sqrt Hz was quieter, presumably due to lower input noise
current in that particular configuration.

The LMEs also have insanely low THD
RL = 600ohms 0.00003% (typ)

http://www.national.com/pf/LM/LME49710.html
http://www.national.com/pf/LM/LM4562.html

Does anyone know of anything better without sacrificing unity gain
stability or THD ?

Not got round to using it yet but the ADA4899 looks tasty. 1nV, 0.7ppm,
600MHz.

Open the window, more shit flies in.
600MHz is not required for audio, only audiophools
Click to expand...
Absolutely. The LME's 60 or so MHz is more than enough.

Graham
 
john jardine wrote:

"Martin Griffith" wrote
"john jardine" wrote:
"Eeyore" wrote

National's LME49710/20/40 amd LM4562 seem to have the best figures at
2.5nV/sqrt Hz but in a practical circuit I found the venerable NE5534
with its 3.5 nV/sqrt Hz was quieter, presumably due to lower input
noise current in that particular configuration.

The LMEs also have insanely low THD
RL = 600ohms 0.00003% (typ)

http://www.national.com/pf/LM/LME49710.html
http://www.national.com/pf/LM/LM4562.html

Does anyone know of anything better without sacrificing unity gain
stability or THD ?

Not got round to using it yet but the ADA4899 looks tasty. 1nV, 0.7ppm,
600MHz.

Open the window, more shit flies in.
600MHz is not required for audio, only audiophools

Yes.
I was thinking more of it allowing a gain of say x5000 to 100kHz. The chip's
low Vos allowing this in one hit.
Click to expand...
Max gain required would be about 24.

Graham
 
Eeyore wrote:
Phil Hobbs wrote:

Eeyore wrote:
National's LME49710/20/40 amd LM4562 seem to have the best figures at
2.5nV/sqrt Hz but in a practical circuit I found the venerable NE5534
with its 3.5 nV/sqrt Hz was quieter, presumably due to lower input noise
current in that particular configuration.

The LMEs also have insanely low THD
RL = 600ohms 0.00003% (typ)

http://www.national.com/pf/LM/LME49710.html
http://www.national.com/pf/LM/LM4562.html

Does anyone know of anything better without sacrificing unity gain
stability or THD ?

What resistance values are you assuming? Not one month ago, in this
very boutique, I posted a link to a new part with some really cute
specs--the ADA4898-1.

http://www.analog.com/static/imported-files/Data_Sheets/ADA4898-1.pdf

I gather it's probably intended for lower source resistances than yours,
but its combination of low eN and low Cin is amazing.

Yes, my source resistance may dominate. It's a new module for SSL 4000E/G
professional sound mixing desks to convert the 'channel buckets' into a
monitor desk for Digital Audio Workstations. I was shocked at how high their
mix resistor values were (15k). Crikey, even at Studiomaster in the latter
days I was using 4k7 !

It's certainly amazingly quiet though.

I'm not familiar with the THD being quoted in dBc though. Can you assist there
?

Graham
Click to expand...
dBc = 'decibels with respect to the carrier', i.e. the undistorted output.


Cheers,

Phil Hobbs
 
Phil Hobbs wrote:

Eeyore wrote:
Phil Hobbs wrote:
Eeyore wrote:
National's LME49710/20/40 amd LM4562 seem to have the best figures at
2.5nV/sqrt Hz but in a practical circuit I found the venerable NE5534
with its 3.5 nV/sqrt Hz was quieter, presumably due to lower input noise
current in that particular configuration.

The LMEs also have insanely low THD
RL = 600ohms 0.00003% (typ)

http://www.national.com/pf/LM/LME49710.html
http://www.national.com/pf/LM/LM4562.html

Does anyone know of anything better without sacrificing unity gain
stability or THD ?

What resistance values are you assuming? Not one month ago, in this
very boutique, I posted a link to a new part with some really cute
specs--the ADA4898-1.

http://www.analog.com/static/imported-files/Data_Sheets/ADA4898-1.pdf

I gather it's probably intended for lower source resistances than yours,
but its combination of low eN and low Cin is amazing.

Yes, my source resistance may dominate. It's a new module for SSL 4000E/G
professional sound mixing desks to convert the 'channel buckets' into a
monitor desk for Digital Audio Workstations. I was shocked at how high their
mix resistor values were (15k). Crikey, even at Studiomaster in the latter
days I was using 4k7 !

It's certainly amazingly quiet though.

I'm not familiar with the THD being quoted in dBc though. Can you assist there
?

dBc = 'decibels with respect to the carrier', i.e. the undistorted output.
Click to expand...
Unfortunately that doesn't specify a specific voltage or power level AFAICS.

Graham
 
Eeyore wrote:
Yes, my source resistance may dominate. It's a new module for SSL 4000E/G
professional sound mixing desks to convert the 'channel buckets' into a
monitor desk for Digital Audio Workstations. I was shocked at how high their
mix resistor values were (15k). Crikey, even at Studiomaster in the latter
days I was using 4k7 !
Click to expand...
At Midas Audio in the 80's we used 12k.


les...
 
Les Matthew wrote:

Eeyore wrote:

Yes, my source resistance may dominate. It's a new module for SSL 4000E/G
professional sound mixing desks to convert the 'channel buckets' into a
monitor desk for Digital Audio Workstations. I was shocked at how high their
mix resistor values were (15k). Crikey, even at Studiomaster in the latter
days I was using 4k7 !

At Midas Audio in the 80's we used 12k.
Click to expand...
Yes, but you were going downhill them. KT group bought out Midas in 88 when I was
there.

Dave Dearden and I were dumbstruck (and not in a good way) just with the mic input
stage.

Graham
 
ggherold@gmail.com wrote:

John Larkin wrote:
Eeyore wrote:
Phil Hobbs wrote:
Eeyore wrote:
National's LME49710/20/40 amd LM4562 seem to have the best figures at
2.5nV/sqrt Hz but in a practical circuit I found the venerable NE5534
with its 3.5 nV/sqrt Hz was quieter, presumably due to lower input noise
current in that particular configuration.

The LMEs also have insanely low THD
RL = 600ohms 0.00003% (typ)

http://www.national.com/pf/LM/LME49710.html
http://www.national.com/pf/LM/LM4562.html

Does anyone know of anything better without sacrificing unity gain
stability or THD ?

What resistance values are you assuming? Not one month ago, in this
very boutique, I posted a link to a new part with some really cute
specs--the ADA4898-1.

http://www.analog.com/static/imported-files/Data_Sheets/ADA4898-1.pdf

I gather it's probably intended for lower source resistances than yours,
but its combination of low eN and low Cin is amazing.

Yes, my source resistance may dominate. It's a new module for SSL 4000E/G
professional sound mixing desks to convert the 'channel buckets' into a
monitor desk for Digital Audio Workstations. I was shocked at how high their
mix resistor values were (15k). Crikey, even at Studiomaster in the latter
days I was using 4k7 !

It's certainly amazingly quiet though.

I'm not familiar with the THD being quoted in dBc though. Can you assist there
?

Graham

15K? Sounds like jfet turf.

John-

15K? Sounds like jfet turf.

Yes, Aren't you going to be dominated by the current noise? Speaking
of jfet opamps, Do you have a low noise favorite? I like the OPA134
from Burr-Brown (TI). But am always looking for something better.
George
Click to expand...
That depends how many inputs are assigned. As these are going only to be monitoring
desks, the number of inputs will be 24 or 36 typically.

So the suming node will see ~ 400-600 ohms. Current noise shouldn't be a problem
here, in fact I'm now thinking again of a discrete front end where en can be as low
as 0.5nv/sqrt Hz with a certain relatively inexpensive device I know, widely used in
direct coupled low-Z mic preamps. Time to do the sums and a balancing act !

Graham
 
Phil Hobbs wrote:
Eeyore wrote:
National's LME49710/20/40 amd LM4562 seem to have the best figures at
2.5nV/sqrt Hz but in a practical circuit I found the venerable NE5534
with its 3.5 nV/sqrt Hz was quieter, presumably due to lower input noise
current in that particular configuration.

The LMEs also have insanely low THD
RL = 600ohms 0.00003% (typ)

http://www.national.com/pf/LM/LME49710.html
http://www.national.com/pf/LM/LM4562.html

Does anyone know of anything better without sacrificing unity gain
stability or THD ?


Graham,

What resistance values are you assuming? Not one month ago, in this
very boutique, I posted a link to a new part with some really cute
specs--the ADA4898-1.

http://www.analog.com/static/imported-files/Data_Sheets/ADA4898-1.pdf

I gather it's probably intended for lower source resistances than yours,
but its combination of low eN and low Cin is amazing.
Click to expand...
But mind the knee which is a bit highish, see figure 13:
http://www.analog.com/static/imported-files/Data_Sheets/ADA4899-1.pdf

Since Graham does audio stuff this amp might not quite be the ticket.

How about a discrete design? Maybe with tubes ...?

<ducking>

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
 
Martin Griffith wrote:
On Sun, 21 Sep 2008 21:51:38 +0100, in sci.electronics.design "john
jardine" <john.jardine@idnet.co.uk> wrote:

"Eeyore" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:48D6A215.52D62814@hotmail.com...
National's LME49710/20/40 amd LM4562 seem to have the best figures at
2.5nV/sqrt Hz but in a practical circuit I found the venerable NE5534
with its 3.5 nV/sqrt Hz was quieter, presumably due to lower input noise
current in that particular configuration.

The LMEs also have insanely low THD
RL = 600ohms 0.00003% (typ)

http://www.national.com/pf/LM/LME49710.html
http://www.national.com/pf/LM/LM4562.html

Does anyone know of anything better without sacrificing unity gain
stability or THD ?

Graham

Not got round to using it yet but the ADA4899 looks tasty. 1nV, 0.7ppm,
600MHz.

Open the window, more shit flies in.
600MHz is not required for audio, only audiophools
Click to expand...
Yeah but: Think what that can do in advertising: Gold plated super
electrons that are made extra agile and can turn themselves around in
under 2nsec. Electrons spend less time in the muddier regions in the
device, therefore get less dirty and don't wear out so fast. Much less
electron fatigue. Makes for extremely crisp crescendos that could never,
ever be heard with an amp that is anywhere less than 500MHz :)

--
SCNR, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
 
Joerg wrote:

Phil Hobbs wrote:
Eeyore wrote:
National's LME49710/20/40 amd LM4562 seem to have the best figures at
2.5nV/sqrt Hz but in a practical circuit I found the venerable NE5534
with its 3.5 nV/sqrt Hz was quieter, presumably due to lower input noise
current in that particular configuration.

The LMEs also have insanely low THD
RL = 600ohms 0.00003% (typ)

http://www.national.com/pf/LM/LME49710.html
http://www.national.com/pf/LM/LM4562.html

Does anyone know of anything better without sacrificing unity gain
stability or THD ?


Graham,

What resistance values are you assuming? Not one month ago, in this
very boutique, I posted a link to a new part with some really cute
specs--the ADA4898-1.

http://www.analog.com/static/imported-files/Data_Sheets/ADA4898-1.pdf

I gather it's probably intended for lower source resistances than yours,
but its combination of low eN and low Cin is amazing.


But mind the knee which is a bit highish, see figure 13:
http://www.analog.com/static/imported-files/Data_Sheets/ADA4899-1.pdf

Since Graham does audio stuff this amp might not quite be the ticket.

How about a discrete design? Maybe with tubes ...?

ducking
Click to expand...
LOL !

Actually, now I know a little more about its practical intended function, I'm
looking at a discrete differential front end using 2SA1085s in front of the
LME49710.

Should be good for 0.7nV/sqrt Hz.

The manufacturer's original design which is not dissimilar in concept except
they got the gain structure wrong used 2 parallel pairs of LM394s !

Graham
 
On Sep 21, 5:34 pm, John Larkin
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Sun, 21 Sep 2008 21:55:34 +0100, Eeyore





rabbitsfriendsandrelati...@hotmail.com> wrote:

Phil Hobbs wrote:

Eeyore wrote:
National's LME49710/20/40 amd LM4562 seem to have the best figures at
2.5nV/sqrt Hz but in a practical circuit I found the venerable NE5534
with its 3.5 nV/sqrt Hz was quieter, presumably due to lower input noise
current in that particular configuration.

The LMEs also have insanely low THD
RL = 600ohms  0.00003% (typ)

http://www.national.com/pf/LM/LME49710.html
http://www.national.com/pf/LM/LM4562.html

Does anyone know of anything better without sacrificing unity gain
stability or THD ?

What resistance values are you assuming?  Not one month ago, in this
very boutique, I posted a link to a new part with some really cute
specs--the ADA4898-1.

http://www.analog.com/static/imported-files/Data_Sheets/ADA4898-1.pdf

I gather it's probably intended for lower source resistances than yours,
but its combination of low eN and low Cin is amazing.

Yes, my source resistance may dominate. It's a new module for SSL 4000E/G
professional sound mixing desks to convert the 'channel buckets' into a
monitor desk for Digital Audio Workstations. I was shocked at how high their
mix resistor values were (15k). Crikey, even at Studiomaster in the latter
days I was using 4k7 !

It's certainly amazingly quiet though.

I'm not familiar with the THD being quoted in dBc though. Can you assist there
?

Graham

15K? Sounds like jfet turf.

John- Hide quoted text -

- Show quoted text -
Click to expand...

15K? Sounds like jfet turf.
Click to expand...
Yes, Aren't you going to be dominated by the current noise? Speaking
of jfet opamps, Do you have a low noise favorite? I like the OPA134
from Burr-Brown (TI). But am always looking for something better.
George
 
On Mon, 22 Sep 2008 10:18:51 -0700, in sci.electronics.design Joerg
<notthisjoergsch@removethispacbell.net> wrote:

Martin Griffith wrote:
snip
Not got round to using it yet but the ADA4899 looks tasty. 1nV, 0.7ppm,
600MHz.

Open the window, more shit flies in.
600MHz is not required for audio, only audiophools


Yeah but: Think what that can do in advertising: Gold plated super
electrons that are made extra agile and can turn themselves around in
under 2nsec. Electrons spend less time in the muddier regions in the
device, therefore get less dirty and don't wear out so fast. Much less
electron fatigue. Makes for extremely crisp crescendos that could never,
ever be heard with an amp that is anywhere less than 500MHz :)
Click to expand...
I've just done a deal with the LHC at Cern, I'm buying the stripped
off electrons from the ultra fast protons that they use in round
thing.

How should I package them?

martin
 
Eeyore wrote:
Les Matthew wrote:

Eeyore wrote:
Yes, my source resistance may dominate. It's a new module for SSL 4000E/G
professional sound mixing desks to convert the 'channel buckets' into a
monitor desk for Digital Audio Workstations. I was shocked at how high their
mix resistor values were (15k). Crikey, even at Studiomaster in the latter
days I was using 4k7 !
At Midas Audio in the 80's we used 12k.

Yes, but you were going downhill them. KT group bought out Midas in 88 when I was
there.

Dave Dearden and I were dumbstruck (and not in a good way) just with the mic input
stage.

Graham
Click to expand...
Dave Dearden, that name rings a bell. I jumped ship to Brit Row around
87. It was mental at Midas then, bank holding the purse strings, full
order book but no cash flow. Pro40 was crazy, so much more electronics
crammed into the same old Pro4 frame, Geoff just wouldn't contemplate
having a larger frame. They got seriously hot.

les...
 
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