Speaker protection and common ground

ads2 · 1st January 2011, 12:33 AM

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

pacificblue · 1st January 2011, 09:29 AM

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.

ads2 · 1st January 2011, 01:42 PM

Thanks Pacificblue for your help.

ads2 · 1st January 2011, 01:47 PM

I face now a big problem that I didn't take in account previously.
The PSU board is the one from Carlos Filipe :

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

ads2 · 1st January 2011, 09:25 PM

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.

pacificblue · 1st January 2011, 10:58 PM

Yes you can use the centre-tapped transformer. You only use one rectifier instead of two.

ads2 · 1st January 2011, 11:02 PM

Thanks pacificblue for the picture, will try to modify the board.

wwenze · 1st January 2011, 11:42 PM

Quote:

Originally Posted by ads2

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

1st January 2011, 12:33 AM	#1
ads2 diyAudio Member Join Date: Dec 2008	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

1st January 2011, 09:29 AM	#2
pacificblue diyAudio Member 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. __________________ If you've always done it like that, then it's probably wrong. (Henry Ford)

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1st January 2011, 01:42 PM	#3
ads2 diyAudio Member Join Date: Dec 2008	Thanks Pacificblue for your help.

1st January 2011, 01:47 PM	#4
ads2 diyAudio Member Join Date: Dec 2008	I face now a big problem that I didn't take in account previously. The PSU board is the one from Carlos Filipe : 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

1st January 2011, 09:25 PM	#5
ads2 diyAudio Member Join Date: Dec 2008	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.

1st January 2011, 11:02 PM	#7
ads2 diyAudio Member Join Date: Dec 2008	Thanks pacificblue for the picture, will try to modify the board.

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