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Old 23rd October 2007, 12:09 AM   #1
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Default LM4702 reference design note 1490 - ideal 1st amplifier?

I'm looking to build my first proper solid-state (non-chipamp) amplifier, and the LM4702 looks like a good starting point.

http://www.national.com/an/AN/AN-1490.pdf

I'm thinking of building an exact copy, but with four channels, and using a 30-0-30 transformer for lower voltage rails and power output.

Any thoughts/advice?

Thanks!
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Old 23rd October 2007, 03:57 AM   #2
kesee is offline kesee  Australia
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Default Re: LM4702 reference design note 1490 - ideal 1st amplifier?

Quote:
Originally posted by Spasticteapot
I'm looking to build my first proper solid-state (non-chipamp) amplifier, and the LM4702 looks like a good starting point.

http://www.national.com/an/AN/AN-1490.pdf

I'm thinking of building an exact copy, but with four channels, and using a 30-0-30 transformer for lower voltage rails and power output.

Any thoughts/advice?

Thanks!

Hi,
Goto Chip Amps >LME49810 - a new cousin for LM4702 thread and you will get lot of information

Regards KC
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Old 23rd October 2007, 05:40 PM   #3
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Looks like a fun project!
Go for it
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Old 24th October 2007, 01:39 AM   #4
Leolabs is offline Leolabs  Malaysia
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What kind of power transistors are u interested in??
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Old 24th October 2007, 02:01 AM   #5
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Quote:
Originally posted by Leolabs
What kind of power transistors are u interested in??
MN2488/MP1620s. They're about $2.50 each, but I'm not quite sure how I'm going to match them.
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Old 24th October 2007, 02:05 AM   #6
Leolabs is offline Leolabs  Malaysia
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Why not try something like the SAP15??
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Old 24th October 2007, 09:57 PM   #7
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Might want to try the LME49810, mono so easier to layout a board. Seems to be easier to get fully stable too. The mono version of the LM4702 is not far away from release. Also might be easier to work with. Laying out a stereo board can be a little bit of a pain. IF you use Darlington devices, don't try to use more than one device per side in the output stage or you may never get it stable.

-SL
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Old 24th October 2007, 10:01 PM   #8
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Quote:
Originally posted by SpittinLLama
Might want to try the LME49810, mono so easier to layout a board. Seems to be easier to get fully stable too. The mono version of the LM4702 is not far away from release. Also might be easier to work with. Laying out a stereo board can be a little bit of a pain. IF you use Darlington devices, don't try to use more than one device per side in the output stage or you may never get it stable.

-SL

I won't. I'm following the reference design to the letter, aside from decreasing the voltage rails (which I have been told won't cause any problems aside from a lower power output.)
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Old 20th February 2013, 09:47 PM   #9
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Hey Spasticteapot, did this ever work out? I'm doing almost exactly the same thing.

I've got a bunch of chip amps laying around, knocked together a dual LM3886 (sounds alright) and am now doing an LM4702 + STD03 pair, or 2SB1560/2SD2390.

Was wondering about issues like:
1. Stability (board layout and other factors)
2. Current limit of OP stage (STD03=15A, 2SB/D=10A) and it's effect on quality
3. DC servos, speaker protection etc - what did you do here?

Just wondering really...
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