Question about star ground LM1875

OMaudio · 13th February 2011, 11:28 AM

Hello,

i have a question about star ground for LM1875 amp. I use a dual pcb, i buyed on ebay.

I build this amp with own parts an it sounds good.

Now i want to put in the amp into a chassis. The chassis is grounded, but how to ground the amp?

I hope, someone can help me.

King regards
Olaf

Rainwulf · 13th February 2011, 12:03 PM

Just run a earth wire from your amp ground to the case.. not much to it.

CraigBuckingham · 13th February 2011, 12:07 PM

Usually with a low ohm resistor and pair of diodes anti-parallel in parallel with resistor. This is done to prevent low ohmic current ground loops. Diodes work if large current fault occurs.

OMaudio · 13th February 2011, 01:36 PM

OK, but wich point i use on the amp board for ground?

Here are some pictures of the amp.

Olaf

Minion · 13th February 2011, 05:37 PM

I usualy use the ground that is between the Big PSU filter caps .......

From looking at your board it looks like you might need a bit more soldering practice ......

OMaudio · 08:33 PM

OK, do you mean the points between the PSU Caps?

Can i use the cap who is near the transformer - C2.

I can use C1/C3 the - pol.

Or C2/C4 the + pol.

Is this ok?

Soldering is good, not so good on pictures.

Olaf

SoNic_real_one · 13th February 2011, 08:29 PM

IMO is better to use the transformer connecting pin (left photo, middle screw - GND).

AndrewGM · 13th February 2011, 08:34 PM

Hey, leave him alone - if the amp works then he's done it's right - he can have another go on something else later.

One the subject of the amp - I connected all the signal grounds together ( with their own individual wires - NOT daisy chained ) and fed them directly to the chassis and mains inlet earth bolt.
It's fine like this.
Someone might have a better way but it works for me.

BTW - it's exactly the same board I used and is very sweet sounding.
It's driving my upper mid drive units and hf units of L and R speakers.

I'm still a newb and soldering is not that easy straight away but if your joints hold the component well, completes the circuit correctly and are not dripping all over an adjacent component then who the hell cares ?

Andrew

Redshift187 · 14th February 2011, 01:51 PM

Quote:

Originally Posted by OMaudio

OK, do you mean the points between the PSU Caps?

I can use C1/C3 the - pol.

Or C2/C4 the + pol.

Is this ok?

Yes, any of those 9 pads in between the capacitors in the photo on the right will do.

OMaudio · 14th February 2011, 02:10 PM

OK, thank you all for help.

King regards

Olaf

13th February 2011, 11:28 AM	#1
OMaudio diyAudio Member Join Date: Feb 2010	Question about star ground LM1875 Hello, i have a question about star ground for LM1875 amp. I use a dual pcb, i buyed on ebay. I build this amp with own parts an it sounds good. Now i want to put in the amp into a chassis. The chassis is grounded, but how to ground the amp? I hope, someone can help me. King regards Olaf

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13th February 2011, 12:03 PM	#2
Rainwulf diyAudio Member Join Date: Feb 2009	Just run a earth wire from your amp ground to the case.. not much to it.

13th February 2011, 12:07 PM	#3
CraigBuckingham diyAudio Member Join Date: Dec 2002 Location: Sydney, Australia	Usually with a low ohm resistor and pair of diodes anti-parallel in parallel with resistor. This is done to prevent low ohmic current ground loops. Diodes work if large current fault occurs.

13th February 2011, 05:37 PM	#5
Minion diyAudio Member Join Date: May 2006	I usualy use the ground that is between the Big PSU filter caps ....... From looking at your board it looks like you might need a bit more soldering practice ......

13th February 2011, 08:29 PM	#7
SoNic_real_one diyAudio Member Join Date: Jan 2008 Location: Virginia	IMO is better to use the transformer connecting pin (left photo, middle screw - GND).

13th February 2011, 08:34 PM	#8
AndrewGM diyAudio Member Join Date: Jun 2008	Hey, leave him alone - if the amp works then he's done it's right - he can have another go on something else later. One the subject of the amp - I connected all the signal grounds together ( with their own individual wires - NOT daisy chained ) and fed them directly to the chassis and mains inlet earth bolt. It's fine like this. Someone might have a better way but it works for me. BTW - it's exactly the same board I used and is very sweet sounding. It's driving my upper mid drive units and hf units of L and R speakers. I'm still a newb and soldering is not that easy straight away but if your joints hold the component well, completes the circuit correctly and are not dripping all over an adjacent component then who the hell cares ? Andrew

14th February 2011, 02:10 PM	#10
OMaudio diyAudio Member Join Date: Feb 2010	OK, thank you all for help. King regards Olaf

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