"Yuanjing" Gainclone 3886 - eBay amazing value ?

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linuxguru

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Joined 2007
AndrewT said:
electricity flows around a circuit.
It cannot enter without an exit.
Click to expand...

Sure - to elaborate, there are two AC lines for the uPC1237 circuit, powered from an isolated secondary (floating wrt to the main secondary winding) of the trafo. This is rectified, filtered and regulated to +12V and used to power the uPC1237. The ground on the filtered side of the rails connects to the main star ground, and that sets the DC 0V level for the protection circuit. The uPC1237 protection circuit senses the speaker-out DC level (through a resistive divider) with reference to this 0V.

It also independently senses the AC level of the trafo through a resistive divider - this is what seems to be confusing some of the previous posters. It can do this, because the DC 0V to the uPC1237 is shared between its own rectifier-filter network as well as the power (star) ground of the main secondary winding.
 
pinkmouse

pinkmouse

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Joined 2002
Hope this helps. ;)
 

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digits

digits

Member
Joined 2011
Yep there is nothing to it, 3 inputs basicaly, 1 to cut off speakers if mains is switched off, one to power the chip, one to sense if there is DC on the output... (which is why I prefer useing them as mono units... there is only one input from the 2 channels which is just tree-ed off by 2 resistors....
 
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Ben78

Member
Joined 2010
Hi, I have read this thread with interest as I recently bought the Oatley Tube Headphone Amp and now want to try my hand at some more advanced 'kits', plus my 'lo-fi' 5.1 amp is on its way out so thought a homebuilt one would be fun.

Can anyone give any insight as to the current known good ebay sellers that sell kits with a decent schematic/PCB and not-fake components?

I am actually looking at a TDA7293 or TDA7294 chip rather than LM3886 though.

Thanks

Ben
 
T

TheLaw117

Member
Joined 2010
I personally would not buy ANY components off of eBay. I like to buy just the blank boards on eBay and then populate them with parts that I've sourced from reputable suppliers. The big WIMA MKP4s that you see are almost always fake. Like 99.9% of the time.

Good sellers (for PCBs):

Jim's Audio: jims audio store items - Get great deals on Capacitors, Bare PCBs of kits items on eBay Stores!

I Wanne Buy: eBay My World - iwannebuy

Zoe Tsang: http://myworld.ebay.com/zoe_tsang/?_trksid=p4340.l2559

Those are my favorites. I've bought from all. All good success.
 
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