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.
put your thinking cap on.
How does the sensing circuit detect a difference in potential?
So...in essence, I just hook up either one of the 28V AC lines to the board, and it would be fine?
yep, they are the same in essence, if you grab the wrong one it will just be a "loop" from ground to ground...
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....
No just the AC sense part. The rest I understand. No need in explaining as long as it works. Thanks.
whew! what a ride!
Barry did you ever sort your mp3 player module amp thingy disable?
I've been wanting to get one of those. It seems it is the nicest MP3 SD USB module at the moment. I have several other smaller ones that I have been using.
THNKs to linuxguru!
Barry did you ever sort your mp3 player module amp thingy disable?
I've been wanting to get one of those. It seems it is the nicest MP3 SD USB module at the moment. I have several other smaller ones that I have been using.
THNKs to linuxguru!
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
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
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.
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.
I think your right, but fake or not, at the prices they sound pretty good. The bare boards are good value. I'm looking forward to my Naim NAC92 to arrive and mod to wire up to my now yuanjing modified Linn amp. Great an it!
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