ebay GainClone PCBs

[portreathbeach]

Thanks again AndrewT 🙂

 

[portreathbeach]

Sorry to ask another question......

Right, I understand the ground-loop breaking idea, but I have just been reading about 'signal start ground' and 'power star ground'!

So, I am I right in thinking that the power supply cables (+, - and GND) leave the PSU and the GND cables connect to a star point (power star) in the amp enclosure and from there feed the the various parts of the amp board and all of the signal grounds are put to a 'signal star point'. The two star points are then connected together and then connected to the chassis via the ground-loop breaker?

Thanks again for all of the help 🙂

 

[AndrewT]

yes,
signal ground has a separate wire to the main power/audio/star ground.
The signal ground can be connected on the PCB to the power ground with a 10r resistor.
I prefer the signal ground to power ground connection to go from the input RCAs. It seems to be quieter from this point for many different source connections.
It is worth having two optional signal grounds, switch between them to find which works best.

If you can, short out the disconnecting network between power ground and Safety Earth. If the amp works well with the shorting switch closed then keep it that way and remove the disconnecting network.

 

[portreathbeach]

Thanks again AndrewT for your quick reply.

Now that I understand a bit more about the grounding, I can see why you don't like the layout of the eBay boards, as all of the grounds are together without separation. I will experiment with these boards, but will end up making my own PCBs on Eagle, as Proteus doesn't work on Mac OS X, and I find it a pain to keep running XP as a virtual machine on it.

I've seen a method for producing PCBs by laser printing onto photo paper and transferring the print onto the copper clad board with an iron. Looks interesting, and much quicker than the ultra violet method.

Thanks again 🙂

 

[portreathbeach]

Hi again,

Is this the sort of arrangement you are talking about:

Sorry about the poor image. Should have done it on the computer 🙂

 

[AndrewT]

Hi
the 680r of the Negative FeedBack (NFB) should be removed from Power Ground and instead connected to the Signal Ground above the 10r.
Similarly the grounding resistor, setting the Rin value 20k, must also go to Signal Ground.

The signal arrives over two wires, signal Hot and signal Return.
These two wires go to the amplifier +IN and -IN, if we adopt opamp nomenclature. To achieve this just remove the two Power Ground symbols and connect the Signal Return to the two unterminated ends.

I suspect you have posted a simplified schematic to address this topic of grounding only.
Please be aware that you have shown a DC coupled amplifier with no protection and that there are numerous components missing that help ensure a successful performance. For beginners all of these must be sorted.

 

[portreathbeach]

Thanks again AndrewT,

Yes this is a simplified schematic to show the grounding. I have left out various capacitors, input fuses etc. just for a simpler drawing of the grounding.

 

[portreathbeach]

Thanks for all of the help in these forums. Here is my first finished GainCone; Post 1363

http://www.diyaudio.com/forums/chip-amps/79303-chip-amp-photo-gallery-137.html

After an evening listening to this amp with another hifi enthusiast, I am amazed at the sound quality and power output obtained from these LM3875 chips, simply stunning.