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Old 1st January 2011, 12:33 AM   #1
ads2 is offline ads2  France
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Default Speaker protection and common ground

Hi all,
first of all, happy new year to all and your familly

I have bought 2 years ago a gainclone made of LM3886 from China from ebay.
Fake chips, bad build quality and partialy broken case during shipping.
Here's a Italian test of the same amp : Recensione: DeskTop Star Gainclone by Hlly Electronics
After repairing it I have used it during 2 years.
Now it's time to get something better, I will only keep transformer and speaker protection unit from previous amp.

I have bought PCBs from DIY Chip Amplifier Kits, PCB's, Components and Information.

I have bought the Dual Mono Kit, but for now I have only one transformer, so I use only one power supply board. (like stereo version)

Haven't tested if everything is ok, but should be.

I had a look at the speaker protection board, and there L/R channels have same ground, the previous amp also used common ground (from RCA input to output).

The chipamp kit always use separate grounds, so is it problematic if the output of the both amplifier boards are connected together to be able to use the protection unit ?

Thanks for your help.

Regards

ads
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Old 1st January 2011, 09:29 AM   #2
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Join Date: May 2008
If both amplifiers are in the same case, they will share the same ground anyhow.
If the speaker grounds are really connected together at the protection board, you need to make sure not to create a ground loop. In that case you should rather take the protection board ground to the star-point instead of routing the speaker ground through the board.
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Old 1st January 2011, 01:42 PM   #3
ads2 is offline ads2  France
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Thanks Pacificblue for your help.
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Old 1st January 2011, 01:47 PM   #4
ads2 is offline ads2  France
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I face now a big problem that I didn't take in account previously.
The PSU board is the one from Carlos Filipe :
Click the image to open in full size.

and my toroidal is a single secondaries (3 wires) not a twin one (4 wires).
Is it still possible to use it ? and how ?

Regards
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Old 1st January 2011, 09:25 PM   #5
ads2 is offline ads2  France
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My transformer is the same as Recensione: DeskTop Star Gainclone by Hlly Electronics - Pagina 3 it seems that Maurarte has suceeded to revert from 3 wires to 4 wires, but I don't understand Italian.
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Old 1st January 2011, 10:58 PM   #6
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Yes you can use the centre-tapped transformer. You only use one rectifier instead of two.
Attached Images
File Type: jpg CFM CT 2011 01 01.jpg (29.9 KB, 190 views)
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Old 1st January 2011, 11:02 PM   #7
ads2 is offline ads2  France
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Thanks pacificblue for the picture, will try to modify the board.
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Old 1st January 2011, 11:42 PM   #8
wwenze is offline wwenze  Singapore
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Join Date: Mar 2008
Quote:
Originally Posted by ads2 View Post
I have bought 2 years ago a gainclone made of LM3886 from China from ebay.
Fake chips, bad build quality and partialy broken case during shipping.
Here's a Italian test of the same amp : Recensione: DeskTop Star Gainclone by Hlly Electronics
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