Topic: Mic Preamp Chip LM833N

[corsair]

I found out my mic preamp uses this chip. Though I concede the preamp
is in the lower end, can anyone give a lowdown on the characteristics of this opamp?

Thanks!

[Brian Skalinder]

I found out my mic preamp uses this chip. Though I concede the preamp
is in the lower end, can anyone give a lowdown on the characteristics of this opamp?

I would say its sonic characteristics are best identfied by...listening to your preamp.

[poorlyconditioned]

I found out my mic preamp uses this chip. Though I concede the preamp
is in the lower end, can anyone give a lowdown on the characteristics of this opamp?

Thanks!

Just curious, what make/model# is the preamp?  Is there any other stuff there too?  For example, is there a transistor pair before the 833?  Are there several 833's arranged as an instrumenation amplfier?

But, the main question is does it sound OK?  If so, don't mess with it!

  Richard

[corsair]

Just curious, what make/model# is the preamp?  Is there any other stuff there too?  For example, is there a transistor pair before the 833?  Are there several 833's arranged as an instrumenation amplfier?

But, the main question is does it sound OK?  If so, don't mess with it!

  Richard

Actually, its the Reactive Sounds preamp...
I took a snapshot of the circuit board...just not sure if its right to upload the photo to the forum..

[poorlyconditioned]

Just curious, what make/model# is the preamp?  Is there any other stuff there too?  For example, is there a transistor pair before the 833?  Are there several 833's arranged as an instrumenation amplfier?

But, the main question is does it sound OK?  If so, don't mess with it!

  Richard

Actually, its the Reactive Sounds preamp...
I took a snapshot of the circuit board...just not sure if its right to upload the photo to the forum..

Is it single 833 chip?  Cool.  I've always wanted to know what is inside these boxes.  As far as upgrades, I'm not sure.  There was some talk about lower power chips (longer battery life), but I'm not sure there is anything that will sound a lot better using a single 9V battery.  I'm using a similar design with an OPA 2134 chip, but I don't think it is really any different in quality.  At least I cannot hear it.

  Richard

[Chuck]

http://www.national.com/ds/LM/LM833.pdf

There are definately better op-amps out there, but it may not be worth messing with depending on the circuit that is built around it.

Other chips with the same pin outs: TL072, TL082, NE5532.. etc... pretty common op-amps

[poorlyconditioned]

Just curious, what make/model# is the preamp?  Is there any other stuff there too?  For example, is there a transistor pair before the 833?  Are there several 833's arranged as an instrumenation amplfier?

But, the main question is does it sound OK?  If so, don't mess with it!

  Richard

Actually, its the Reactive Sounds preamp...
I took a snapshot of the circuit board...just not sure if its right to upload the photo to the forum..

Can you PM me a copy of the photo?  Or go ahead and post it.  I would like to see it.

We dissect gear all the time, so why should reactive sounds be different, right?

  Richard

[Brian Skalinder]

I took a snapshot of the circuit board...just not sure if its right to upload the photo to the forum..

If you're concerned about some sort of board policy, don't sweat it - post away.  If you're about publishing the manufacturer's board, in general, then do what you wish.

[Kindguy]

Post it!

[dklein]

if memory serves, don't these guys make a big deal out of 'variable gain' vs. the usual fixed gain with attenuation?
fwiw, I think it's difficult to get the gain to track properly in both channels, and that a variable gain design often introduces noise when you turn the knob.

I wouldn't mind a peak inside - I'll bet it's a dead simple circuit.

[corsair]

Ok, here's the photo..
Hope I don't get sued... By right, any joker can easily dissect it.. 

And yes, its a dead simple circuit.

[poorlyconditioned]

Ok, here's the photo..
Hope I don't get sued... By right, any joker can easily dissect it.. 

And yes, its a dead simple circuit.

Thanks!  It looks simple, but I'm curious why there are two LM833's there.  Each one has two opamps.  Do you have any ideas?  Is one used for the level/overload detector?  Or is it some kind of multistage/instrumentation amplifier?

  Richard

[corsair]

Thanks!  It looks simple, but I'm curious why there are two LM833's there.  Each one has two opamps.  Do you have any ideas?  Is one used for the level/overload detector?  Or is it some kind of multistage/instrumentation amplifier?

  Richard

I really have no idea... My knowledge on electronics is way back in junior college... where I l dithered around a bit
with small circuit boards...

All I know about this circuit is that its supposed to act as a microphone preamp, with variable gain
and a led that lights up when the signal is clipping the preamp.

[Weazel]

1 for the left and 1 for the right channel?

[poorlyconditioned]

1 for the left and 1 for the right channel?

Yeah, but each chip has two opams inside.  So there are a total of four opamps for two channels.  A cheap box (like mine!) would use just one opamp for each channel.

  Richard

[poorlyconditioned]

it is because of the clip light circuit they are using one side of each chip to drive the clip led. IMO

Ok, here's the photo..
Hope I don't get sued... By right, any joker can easily dissect it.. 

And yes, its a dead simple circuit.

Thanks!  It looks simple, but I'm curious why there are two LM833's there.  Each one has two opamps.  Do you have any ideas?  Is one used for the level/overload detector?  Or is it some kind of multistage/instrumentation amplifier?

  Richard

Aha!  Thanks for the info, Chris...  I didn't think of this.

+T

 Richard

[neutrino]

You could install a couple of dip sockets and plug and play with various compatable opamps to see which you like best.
dB-

[poorlyconditioned]

You could install a couple of dip sockets and plug and play with various compatable opamps to see which you like best.
dB-

Been there... done that!  It turns out, to my ears anyway, not to make that much difference.  I haven't done a systematic test, but just listening informally.  LM833 is a bit low-end, but NE5532, or any of the OPA opamps that Chris uses should be fine.  A more important issue (for me at least) was power consumption.  I've used an LT6234, and that uses about 1/3 less power than the others and sounds just as good.  Unfortunately this only comes in surface mount, so soldering is very hard.  If I was building these for sale, though, I would have a PC board made.  That is a very nice chip.

  Richard

[poorlyconditioned]

I will have to check that chip out what is the max gain of the chip? and power consumption.

Chris

You could install a couple of dip sockets and plug and play with various compatable opamps to see which you like best.
dB-

Been there... done that!  It turns out, to my ears anyway, not to make that much difference.  I haven't done a systematic test, but just listening informally.  LM833 is a bit low-end, but NE5532, or any of the OPA opamps that Chris uses should be fine.  A more important issue (for me at least) was power consumption.  I've used an LT6234, and that uses about 1/3 less power than the others and sounds just as good.  Unfortunately this only comes in surface mount, so soldering is very hard.  If I was building these for sale, though, I would have a PC board made.  That is a very nice chip.

  Richard

I'm not sure the gain specs, but it is 1.1mA consumption per channel.  Check out the LT website (linear.com), and order some samples.  Hey, at least you might really be using them in a real product .

You can PM me if you have any specific questions about the circuit, but I think we're all using pretty much the same design (aside from the clip light you added).

  Richard