Is this similar to a gainclone? Will it work? - diyAudio
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Old 22nd March 2008, 05:15 PM   #1
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Default Is this similar to a gainclone? Will it work?

Hello all! I'm new to hifi and this is my first post here. I've been build guitar gear for years and came across this amp: http://www.generalguitargadgets.com/...lm3886_amp.pdf

My question is if this would be suitable to use as pair of monoblocks for a home stereo. It looks similar to some of the gainclones, but my knowledge is not enough to really now.

Thanks in advance!
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Old 22nd March 2008, 05:28 PM   #2
AndrewT is online now AndrewT  Scotland
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Hi,
it's missing a few filters and Zobels, but otherwise it's close to meeting a home stereo use.

But, I suggest you only use 8ohm speakers and not 4 to 8 ohm.
Use a heatsink twice as big as National suggest.
Widen the bass bandwidth.
Read quite a few more threads on chipamps, particularly on the two basic versions: inverting and non-inverting and between the PSU types with smoothing at the rectifiers vs with decoupling only and no smoothing.
Download the chip datasheet and the application note from National and read all of them thoroughly and re-read them till it's coming out your ears. And ask if you don't understand before you start ordering parts.
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Old 22nd March 2008, 05:32 PM   #3
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Hi Andrew,
I see the Thiele network is a coil wound on a resistor, have you seen this before?
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Old 22nd March 2008, 05:45 PM   #4
AndrewT is online now AndrewT  Scotland
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Quote:
Originally posted by audio1st
Hi Andrew,
I see the Thiele network is a coil wound on a resistor, have you seen this before?
That's only half the Thiele network.
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Old 22nd March 2008, 08:24 PM   #5
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Thanks! Instead of adapting this I think I'll just look for a good home stereo specific project for my LM3876 chips. Thanks so very much for your quick responses!
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Old 22nd March 2008, 08:49 PM   #6
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Hi theundeadelvis,

The schematic you posted looks like the NS app note to me and will work fine in most cases.

For a more complete schematic, you might find this useful.
(R8 R9 not necessary)

http://sound.westhost.com/project19.htm

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Old 22nd March 2008, 11:47 PM   #7
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Hmmmm, now I have to decide. I don't mind scratching this and starting with a clean slate. The only thing that keeps me considering trying it as is is that I already etched 2 boards for the project. Not a big deal, I just hate to waste them. Thanks again for all the input.
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Old 23rd March 2008, 12:02 AM   #8
AndrewT is online now AndrewT  Scotland
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Greg & I both said it will work.
Have a read around and see what is missing and where these components can be added to your PCB.
The input filter components can all be usefully located on the input RCA. Some say they are better there anyway.
That just leaves the Zobel to be added and change the value of the feedback cap.
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