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National Semi LMC6032 sub?

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Anonymous
August 19, 2004 3:01:43 AM

Archived from groups: rec.audio.pro (More info?)

Hi, all,

Well, I had to open it up to replace two pots anyway, so...

....looking in an acoustic guitar preamp I have I see three of these opamps
in it. Naturally, I start wondering about "upgrading." I have three LT1469
chips. Would these be a good choice for an upgrade?

George Reiswig
Song of the River Music

More about : national semi lmc6032

Anonymous
August 19, 2004 4:57:06 AM

Archived from groups: rec.audio.pro (More info?)

"A. & G. Reiswig" <NOSPAMreiswig@bigfoot.com> wrote in message
news:rdRUc.20692$Kf4.8621@nwrddc02.gnilink.net...
> Hi, all,
>
> Well, I had to open it up to replace two pots anyway, so...
>
> ...looking in an acoustic guitar preamp I have I see three of these opamps
> in it. Naturally, I start wondering about "upgrading." I have three
> LT1469
> chips. Would these be a good choice for an upgrade?


Absolutely. They'll be totally more groovulating, and your flux density
will be unsurpassed.

Pray tell, what are the problems that you're having at the moment that cause
you to consider upgrading? And why is it that you feel that anyone could
possibly offer an intelligent answer to a question like the one you asked?

Maybe, just maybe, the designer made a bad mistake in his/her choice of
opamp, and there is some other opamp out there that can drop into the same
circuit and provide an improvement in all regards. More likely, they chose
the LMC6032 because they thought it was the best alternative; and if you
change it you'll just trade off some specs for others - noise for battery
consumption, or frequency range for distortion, or whatever. Which ones
you'll end up trading off will depend entirely on what the circuit is;
which, of course, one can't even guess at with the information you've given.

The LT1469, though, would be a singularly poor choice for replacement.
First, it's not specified to work reliably at the supply voltage that your
preamp likely runs at (a partially drained 9V battery, that is); second,
it's extremely fast, meaning it will probably be unstable in a circuit
designed to work with the comparatively slow LMC6032; and third, it consumes
10x as much supply current, meaning it will decimate your battery life.
Anonymous
August 19, 2004 5:48:43 AM

Archived from groups: rec.audio.pro (More info?)

"A. & G. Reiswig" wrote:

> Hi, all,
>
> Well, I had to open it up to replace two pots anyway, so...
>
> ...looking in an acoustic guitar preamp I have I see three of these opamps
> in it. Naturally, I start wondering about "upgrading." I have three LT1469
> chips. Would these be a good choice for an upgrade?

The LMC6032 doesn't have stunning noise performance @ 22nV/rtHz and has low slew
rate @ 1.1V/us but is CMOS ( low power consumption - 400uA/op-amp ).

The LT1469 appears to be bipolar, judging by the input bias currents. OK, its
slew rate is higher @ 22V/us and noise is lower at 5nV/rtHz but depending on
the circuitry involved this may be degraded by the higher input noise *current*.
Its power consumption is also higher ( 6.5 mA ) so if in a battery powered
implementation will significantly reduce battery life.

Unless you're unhappy with the existing performance, probably simplest to leave
well alone.


Graham
Anonymous
August 19, 2004 6:52:56 AM

Archived from groups: rec.audio.pro (More info?)

Walter Harley wrote:

> third, it consumes
> 10x as much supply current, meaning it will decimate your battery life.

I hate to be a poo-poo but 'decimating' means reducing by one tenth !

The LTs will flatten any batteries way faster than 1/10th quicker.

Just love to comment on accurate use of the English language - can't resist it -
hope you don't mind ! Many ppl seem to think it means to reduce *to* 1/10th
rather than *by* 1/10th - which is not the case.


Cheers, Graham

http://dictionary.reference.com/search?q=decimate

Usage Note: Decimate originally referred to the killing of every tenth person, a
punishment used in the Roman army for mutinous legions

etc
Anonymous
August 19, 2004 7:57:23 AM

Archived from groups: rec.audio.pro (More info?)

Thank you for your cogent, smart-assed answer, Walter. You could have saved
a lot of text had you just said "They're not even close to direct
replacements, and their current draw is a lot higher."

'Course you don't know me, so why not lambaste? Besides, it is beyond the
realm of reason to suspect that manufacturers might actually use parts that
are CHEAP rather than GOOD.

Have a nice day!

George Reiswig
Song of the River Music

"Walter Harley" <walterh@cafewalterNOSPAM.com> wrote in message
news:cg0tt2$452$0$216.39.172.65@theriver.com...
> "A. & G. Reiswig" <NOSPAMreiswig@bigfoot.com> wrote in message
> news:rdRUc.20692$Kf4.8621@nwrddc02.gnilink.net...
> > Hi, all,
> >
> > Well, I had to open it up to replace two pots anyway, so...
> >
> > ...looking in an acoustic guitar preamp I have I see three of these
opamps
> > in it. Naturally, I start wondering about "upgrading." I have three
> > LT1469
> > chips. Would these be a good choice for an upgrade?
>
>
> Absolutely. They'll be totally more groovulating, and your flux density
> will be unsurpassed.
>
> Pray tell, what are the problems that you're having at the moment that
cause
> you to consider upgrading? And why is it that you feel that anyone could
> possibly offer an intelligent answer to a question like the one you asked?
>
> Maybe, just maybe, the designer made a bad mistake in his/her choice of
> opamp, and there is some other opamp out there that can drop into the same
> circuit and provide an improvement in all regards. More likely, they
chose
> the LMC6032 because they thought it was the best alternative; and if you
> change it you'll just trade off some specs for others - noise for battery
> consumption, or frequency range for distortion, or whatever. Which ones
> you'll end up trading off will depend entirely on what the circuit is;
> which, of course, one can't even guess at with the information you've
given.
>
> The LT1469, though, would be a singularly poor choice for replacement.
> First, it's not specified to work reliably at the supply voltage that your
> preamp likely runs at (a partially drained 9V battery, that is); second,
> it's extremely fast, meaning it will probably be unstable in a circuit
> designed to work with the comparatively slow LMC6032; and third, it
consumes
> 10x as much supply current, meaning it will decimate your battery life.
>
>
Anonymous
August 19, 2004 7:58:10 AM

Archived from groups: rec.audio.pro (More info?)

Thanks, Graham! That's what I was after. I'd looked over the spec sheets,
but wanted a second opinion. I hadn't caught the current draw aspect.

George Reiswig
Song of the River Music

"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:4123F8EB.57F7A869@hotmail.com...
> "A. & G. Reiswig" wrote:
>
> > Hi, all,
> >
> > Well, I had to open it up to replace two pots anyway, so...
> >
> > ...looking in an acoustic guitar preamp I have I see three of these
opamps
> > in it. Naturally, I start wondering about "upgrading." I have three
LT1469
> > chips. Would these be a good choice for an upgrade?
>
> The LMC6032 doesn't have stunning noise performance @ 22nV/rtHz and has
low slew
> rate @ 1.1V/us but is CMOS ( low power consumption - 400uA/op-amp ).
>
> The LT1469 appears to be bipolar, judging by the input bias currents. OK,
its
> slew rate is higher @ 22V/us and noise is lower at 5nV/rtHz but depending
on
> the circuitry involved this may be degraded by the higher input noise
*current*.
> Its power consumption is also higher ( 6.5 mA ) so if in a battery powered
> implementation will significantly reduce battery life.
>
> Unless you're unhappy with the existing performance, probably simplest to
leave
> well alone.
>
>
> Graham
>
Anonymous
August 19, 2004 9:51:58 AM

Archived from groups: rec.audio.pro (More info?)

"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:412407F7.4FFB2FAB@hotmail.com...
> Just love to comment on accurate use of the English language - can't
> resist it -
> hope you don't mind ! Many ppl seem to think it means to reduce *to*
> 1/10th
> rather than *by* 1/10th - which is not the case.

Don't mind at all. Thanks for the correction, and my apologies for the
misuse. I remembered the origin, but got confused over whether they killed
every tenth man, or left every tenth man alive...
Anonymous
August 19, 2004 10:05:46 AM

Archived from groups: rec.audio.pro (More info?)

"A. & G. Reiswig" <NOSPAMreiswig@bigfoot.com> wrote in message
news:D yVUc.36500$SC1.35891@nwrddc03.gnilink.net...
> Thank you for your cogent, smart-assed answer, Walter. You could have
> saved
> a lot of text had you just said "They're not even close to direct
> replacements, and their current draw is a lot higher."
>
> 'Course you don't know me, so why not lambaste? Besides, it is beyond the
> realm of reason to suspect that manufacturers might actually use parts
> that
> are CHEAP rather than GOOD.


The LMC6032's aren't cheap enough, or common enough, to be a part that was
chosen without some thought.

There seems to be a large group of folks out there who have this "upgrade
the opamps" bug - as if opamps could be ranked on some sort of scale of
Betterness, and if they just get some Better opamps their circuit will be
Better. Your question didn't include any mention of how the opamps were
being used in the circuit, or even of the manufacturer of the circuit; you
didn't have any evident complaint about the current opamps, other than a
suspicion that they could be Better; and you had apparently not absorbed any
of the relevant parts of the datasheets of the two opamps in question; these
facts led me to suspect that you might be part of that large group. To be
honest, I still suspect it.

But you're right, it was a smart-assed answer. I apologize. That it is a
pet peeve for me was no reason for me to be rude.

Here's a more polite version:

The performance of an opamp in a circuit is a function in large part of that
circuit. Different circuits demand different things of opamps - an opamp
that is better in one might be worse than another. In particular, speed is
good for some circuits, bad for others; high current consumption acceptable
in some circuits, not in others; high input impedance necessary in some, not
in others; and current noise is more important in some circuits, where
voltage noise is more important in others. The two opamps you described
differ substantially in all those parameters, as well as others. So, it is
quite unlikely that the LT1469 would be a good replacement.

As to whether a good replacement does exist, that question can't be answered
without a bit more information. Do you have, or can you trace and post, a
schematic of the circuit in question? If not, can you let us know what kind
of pickup the opamp is amplifying; what voltage is powering it; and whether
you believe it is serving as an amplifier, active tone control, or both?
Anonymous
August 19, 2004 12:39:25 PM

Archived from groups: rec.audio.pro (More info?)

A. & G. Reiswig <NOSPAMreiswig@bigfoot.com> wrote:
>Well, I had to open it up to replace two pots anyway, so...
>
>...looking in an acoustic guitar preamp I have I see three of these opamps
>in it. Naturally, I start wondering about "upgrading." I have three LT1469
>chips. Would these be a good choice for an upgrade?

Not unless you also change the supply rail voltages. The whole point of
the LMC6032 is clean operation with low rail voltages and low current
draw. Anything that sounds better is also going to be a lot less efficient.
But it still might be worth it depending on the gear... I am assuming it is
battery operated from the fact that they use the 6032. Could you live with
more batteries inside the case and a shorter operating time, in exchange for
better sound?

Note that changing rail voltages will also probably mean having to change
electrolytic caps for higher values too.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
August 19, 2004 7:11:49 PM

Archived from groups: rec.audio.pro (More info?)

Walter,

No harm done...I probably overreacted, too, so I apologize as well.

You're right...I looked at the data sheets and focused on noise and slew
rate parameters, and missed other key points. The only reason that I was
even thinking of replacing them is that a) I was going to be working on the
board anyway, and b) I have the LT1469's sitting around. That coupled with
my suspicious mind when it comes to manufacturers' choices for component
quality made me wonder.

I'd had great success changing components out in an old Symetrix mic pre,
but that was based on Monte McGuire's suggestions. Before I made the
changes, if someone had asked "Well, what problem do you have with the
existing components?" ...I couldn't have answered any more specifically
than that I would go to the trouble to record four tracks two-at-a-time with
my RNP rather than one take of four tracks with my RNP and the Symetrix. I
had no idea how much difference the component changeout might make. But
now, although the RNP is still better for critical tracks, the margin is
reduced enough that I can do four tracks at once without much concern.

From what you, Scott, and Pooh have said, the manufacturer chose opamps
wisely for this app, and you say they didn't chose cheap. (LR Baggs)...my
compliments to them!

Thanks, all! I'll leave it as-is...except for those pots.

George Reiswig
Song of the River Music

"Walter Harley" <walterh@cafewalterNOSPAM.com> wrote in message
news:cg1fvq$70v$0$216.39.172.65@theriver.com...
> "A. & G. Reiswig" <NOSPAMreiswig@bigfoot.com> wrote in message
> news:D yVUc.36500$SC1.35891@nwrddc03.gnilink.net...
> > Thank you for your cogent, smart-assed answer, Walter. You could have
> > saved
> > a lot of text had you just said "They're not even close to direct
> > replacements, and their current draw is a lot higher."
> >
> > 'Course you don't know me, so why not lambaste? Besides, it is beyond
the
> > realm of reason to suspect that manufacturers might actually use parts
> > that
> > are CHEAP rather than GOOD.
>
>
> The LMC6032's aren't cheap enough, or common enough, to be a part that was
> chosen without some thought.
>
> There seems to be a large group of folks out there who have this "upgrade
> the opamps" bug - as if opamps could be ranked on some sort of scale of
> Betterness, and if they just get some Better opamps their circuit will be
> Better. Your question didn't include any mention of how the opamps were
> being used in the circuit, or even of the manufacturer of the circuit; you
> didn't have any evident complaint about the current opamps, other than a
> suspicion that they could be Better; and you had apparently not absorbed
any
> of the relevant parts of the datasheets of the two opamps in question;
these
> facts led me to suspect that you might be part of that large group. To be
> honest, I still suspect it.
>
> But you're right, it was a smart-assed answer. I apologize. That it is a
> pet peeve for me was no reason for me to be rude.
>
> Here's a more polite version:
>
> The performance of an opamp in a circuit is a function in large part of
that
> circuit. Different circuits demand different things of opamps - an opamp
> that is better in one might be worse than another. In particular, speed
is
> good for some circuits, bad for others; high current consumption
acceptable
> in some circuits, not in others; high input impedance necessary in some,
not
> in others; and current noise is more important in some circuits, where
> voltage noise is more important in others. The two opamps you described
> differ substantially in all those parameters, as well as others. So, it
is
> quite unlikely that the LT1469 would be a good replacement.
>
> As to whether a good replacement does exist, that question can't be
answered
> without a bit more information. Do you have, or can you trace and post, a
> schematic of the circuit in question? If not, can you let us know what
kind
> of pickup the opamp is amplifying; what voltage is powering it; and
whether
> you believe it is serving as an amplifier, active tone control, or both?
>
>
>
>
Anonymous
August 19, 2004 9:37:18 PM

Archived from groups: rec.audio.pro (More info?)

A. & G. Reiswig wrote:
>
> ...looking in an acoustic guitar preamp I have I see three of these opamps
> in it. Naturally, I start wondering about "upgrading." I have three LT1469
> chips. Would these be a good choice for an upgrade?

Jim Williams uses LT1352's for very low power stuff, dunno much of the details but someone else can probably offer intelligent commentary...
Anonymous
August 20, 2004 1:38:08 AM

Archived from groups: rec.audio.pro (More info?)

Kurt Albershardt <kurt@nv.net> wrote:
>A. & G. Reiswig wrote:
>>
>> ...looking in an acoustic guitar preamp I have I see three of these opamps
>> in it. Naturally, I start wondering about "upgrading." I have three LT1469
>> chips. Would these be a good choice for an upgrade?
>
>Jim Williams uses LT1352's for very low power stuff, dunno much of the details but someone else can probably offer intelligent commentary...

I've used a number of the Maxim chips for very low power stuff. They don't
sound very good, but man they can run with so little current it's not funny.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
August 20, 2004 8:34:50 AM

Archived from groups: rec.audio.pro (More info?)

Kurt Albershardt wrote:

> A. & G. Reiswig wrote:
> >
> > ...looking in an acoustic guitar preamp I have I see three of these opamps
> > in it. Naturally, I start wondering about "upgrading." I have three LT1469
> > chips. Would these be a good choice for an upgrade?
>
> Jim Williams uses LT1352's for very low power stuff, dunno much of the details but someone else can probably offer intelligent commentary...

Looked promising until I saw the input bias current figures.

Graham
Anonymous
August 20, 2004 10:11:42 AM

Archived from groups: rec.audio.pro (More info?)

"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:41257159.C500A963@hotmail.com...
> Looked promising until I saw the input bias current figures.

I didn't look at them. But if it's a preamp for a magnetic pickup, it might
not matter at all - source impedance probably around 10k to 100k. If it's
for a piezo, or an electret, different story. LR Baggs makes all three, I
*think*; the OP hasn't mentioned which it is.
Anonymous
August 20, 2004 12:12:03 PM

Archived from groups: rec.audio.pro (More info?)

Pooh Bear <rabbitsfriendsandrelations@hotmail.com> wrote in message news:<41257159.C500A963@hotmail.com>...
> Kurt Albershardt wrote:
>
> > A. & G. Reiswig wrote:
> > >
> > > ...looking in an acoustic guitar preamp I have I see three of these opamps
> > > in it. Naturally, I start wondering about "upgrading." I have three LT1469
> > > chips. Would these be a good choice for an upgrade?
> >
> > Jim Williams uses LT1352's for very low power stuff, dunno much of the details but someone else can probably offer intelligent commentary...
>
> Looked promising until I saw the input bias current figures.
>
> Graham

I use those 1352's in the onboard guitar preamps I build. Bias current
is very low for a bipolar part, it resembles the old "super-beta"
opamps like the ol' 308 from National. (Arn't we getting old or what?)
Anyway, it works very well in 1 meg ohm front ends without excessive
dc shift. I even use them in the EQ section of the old TAC Scorpions
as the low bias current likes the 470k sweep pot's impedance. Lower
noise, lower distortion, 200 v/us slew rate, 250 ua supply current...
what's not to love?

Jim Williams
Audio Upgrades
Anonymous
August 20, 2004 5:49:32 PM

Archived from groups: rec.audio.pro (More info?)

OP here...

The pickups are B-Band pickups, which actually have a preamp inside the
guitar to buffer between the electret film pickup and whatever. Output
impedance of the preamp is listed at 150 Ohms. But (ignorance showing once
again) I don't know what that means in this case. Eager to learn, though!

George Reiswig
Song of the River Music

"Walter Harley" <walterh@cafewalterNOSPAM.com> wrote in message
news:cg44mu$kda$0$216.39.172.65@theriver.com...
> "Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
> news:41257159.C500A963@hotmail.com...
> > Looked promising until I saw the input bias current figures.
>
> I didn't look at them. But if it's a preamp for a magnetic pickup, it
might
> not matter at all - source impedance probably around 10k to 100k. If it's
> for a piezo, or an electret, different story. LR Baggs makes all three, I
> *think*; the OP hasn't mentioned which it is.
>
>
Anonymous
August 20, 2004 11:45:15 PM

Archived from groups: rec.audio.pro (More info?)

"Jim Williams" <jwilliams3@audioupgrades.com> wrote in message
news:a377f4b9.0408200712.6172b25e@posting.google.com...
> I use those 1352's in the onboard guitar preamps I build. Bias current
> is very low for a bipolar part, [...] Lower
> noise, lower distortion, 200 v/us slew rate, 250 ua supply current...
> what's not to love?

Gee, those are some extraordinary specs! And it's specified at supply
voltages down to 5v, which is great. Stable into capacitive loads. Still
available in DIP8 package, not just surface mount. Looks like a nice
substitute for a TL062 in most applications, and probably also for the
LMC6032's in George's LR Baggs preamp, since it's being driven by a low
impedance.

Showing stock at Digikey for $8.38 each in unit quantity.


Thanks, Jim. If you need any LM308's let me know, I'm sure I've got a few
tubes still lying around ;-)
Anonymous
August 20, 2004 11:54:57 PM

Archived from groups: rec.audio.pro (More info?)

"A. & G. Reiswig" <NOSPAMreiswig@bigfoot.com> wrote in message
news:MjnVc.9147$og.7295@nwrddc04.gnilink.net...
> OP here...
>
> The pickups are B-Band pickups, which actually have a preamp inside the
> guitar to buffer between the electret film pickup and whatever. Output
> impedance of the preamp is listed at 150 Ohms. But (ignorance showing
> once
> again) I don't know what that means in this case. Eager to learn, though!

So, you've got B-Band pickups, with the associated B-Band preamp inside the
guitar; and you're running the output of those into the LR Baggs preamp.
Are you sure you need the LR Baggs at all, actually? Are you just using it
for tone control?

In any event, the LT1352's that were mentioned sound like a good candidate
for improvement; it doesn't sound like the high input impedance of the CMOS
LMC6032 is important in this application, and the LT1352's apparent
discomfort with large differential signals won't be a problem either.

If you do it, let us know how it sounds! You might consider doing a bit of
recording before making the change, and then after, so as to have a
reasonably good comparison.
!