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-   -   LM4702 reference design note 1490 - ideal 1st amplifier? (http://www.diyaudio.com/forums/solid-state/110553-lm4702-reference-design-note-1490-ideal-1st-amplifier.html)

Spasticteapot 23rd October 2007 12:09 AM

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!

kesee 23rd October 2007 03:57 AM

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

myhrrhleine 23rd October 2007 05:40 PM

Looks like a fun project!
Go for it :) :)

Leolabs 24th October 2007 01:39 AM

What kind of power transistors are u interested in??

Spasticteapot 24th October 2007 02:01 AM

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.

Leolabs 24th October 2007 02:05 AM

Why not try something like the SAP15??

SpittinLLama 24th October 2007 09:57 PM

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

Spasticteapot 24th October 2007 10:01 PM

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.)

TheGabbleDuck 20th February 2013 09:47 PM

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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