Audio CFB Opamp

jackinnj · 5th November 2007, 07:49 PM

Hot off the presses:

it's a wow

http://www.national.com/ds/LM/LME49713.pdf

x-pro · 5th November 2007, 07:59 PM

Quote:

Originally posted by jackinnj
it's a wow

In what respect "wow"? I can not see anything particularly interesting from the datasheet. Perhaps it may sound good in some appliciations but that only a listening test can tell.

Alex

Ipanema · 6th November 2007, 01:38 AM

This opamp spec sheet looks fantastic. BTW, can it drive a 32ohms headphone or is it good for an opamp based power amp since the current output is +/-100mA.

Thanks.

Tim__x · 6th November 2007, 04:29 AM

Looks pretty nice.
Though the high value feedback resistors will ruin noise performance.

peranders · 6th November 2007, 07:36 AM

The performance is similar other CFB opamps like the TPA6120 but since I like CFB it looks wow.

peranders · 6th November 2007, 07:39 AM

Quote:

Originally posted by Tim__x
Looks pretty nice.
Though the high value feedback resistors will ruin noise performance.

It's a good point but also quite irrelevant because it's a CFB topology which is useless for high impedance network, it's against it's nature. In this case Tim, you must do you homework about CFB amps.

Tim__x · 6th November 2007, 04:46 PM

I understand how CFB works. Look at page 6, good stability appears to require at least a couple Kohms of feedback resistance.

This CFB opamp is optimized for slightly higher values in the feedback network than many other opamps. It's not a huge concern, but it is a valid and considered complaint.

Tolu · 28th November 2007, 07:34 AM

I don't see the point. 1.2kOhm isn't the issue I think.
The slew rate is extraordinary.

I would test how it sounds in a preamp but National wants 30$ for 4 sample chips!

Anyone just tried it?

banana · 28th November 2007, 07:44 AM

1.2Kohm would be an issue, if u multiple it with 16pA/rtHz current noise density. But that's the case only when gain is low.

5th November 2007, 07:49 PM	#1
jackinnj diyAudio Member Join Date: Apr 2002 Location: Llanddewi Brefi, NJ	Audio CFB Opamp Hot off the presses: it's a wow http://www.national.com/ds/LM/LME49713.pdf

6th November 2007, 07:36 AM	#5
peranders Electrons are yellow and more is better! diyAudio Member Join Date: Apr 2002 Location: Göteborg, Sweden Blog Entries: 4	The performance is similar other CFB opamps like the TPA6120 but since I like CFB it looks wow. __________________ /Per-Anders (my first name) or P-A as my friends call me

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6th November 2007, 01:38 AM	#3
Ipanema diyAudio Member Join Date: Jun 2004 Location: KL	This opamp spec sheet looks fantastic. BTW, can it drive a 32ohms headphone or is it good for an opamp based power amp since the current output is +/-100mA. Thanks.

6th November 2007, 04:29 AM	#4
Tim__x diyAudio Member Join Date: Jun 2004 Location: Edmonton area, Alberta	Looks pretty nice. Though the high value feedback resistors will ruin noise performance.

6th November 2007, 04:46 PM	#7
Tim__x diyAudio Member Join Date: Jun 2004 Location: Edmonton area, Alberta	I understand how CFB works. Look at page 6, good stability appears to require at least a couple Kohms of feedback resistance. This CFB opamp is optimized for slightly higher values in the feedback network than many other opamps. It's not a huge concern, but it is a valid and considered complaint.

28th November 2007, 07:34 AM	#8
Tolu diyAudio Member Join Date: Mar 2007	I don't see the point. 1.2kOhm isn't the issue I think. The slew rate is extraordinary. I would test how it sounds in a preamp but National wants 30$ for 4 sample chips! Anyone just tried it?

28th November 2007, 07:44 AM	#9
banana diyAudio Member Join Date: Feb 2003 Location: Hong Kong	1.2Kohm would be an issue, if u multiple it with 16pA/rtHz current noise density. But that's the case only when gain is low.

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