Hi there, I already asked question on ChipAmps forum , but nobody seems to know how to solve problem...
Just finished, PA100, chipamp and snuberized regulated PSU.
Testing one chanel (board) everything is beautiful, rail voltage is steady +/-27V, dc-offset 15mV, testing other the same thing... Absolutely beautiful...
Now the funny part, when I connected both channels(boards) to a PSU I got massive voltage drop and negative LM388 got too hot to touch... I used a single power tranny (separate windings), a single PSU, two rectifiers (ready made, rated 7A) LM388 regulators... So, every board works perfectly, but when they are both in system sh.. hits the fan...
Alexw amp.
http://shine7.com/audio/pa100.htm
Regulated psu , nuuk's pages http://myweb.tiscali.co.uk/nuukspot...gainclone6.html
Just finished, PA100, chipamp and snuberized regulated PSU.
Testing one chanel (board) everything is beautiful, rail voltage is steady +/-27V, dc-offset 15mV, testing other the same thing... Absolutely beautiful...
Now the funny part, when I connected both channels(boards) to a PSU I got massive voltage drop and negative LM388 got too hot to touch... I used a single power tranny (separate windings), a single PSU, two rectifiers (ready made, rated 7A) LM388 regulators... So, every board works perfectly, but when they are both in system sh.. hits the fan...
Alexw amp.
http://shine7.com/audio/pa100.htm
Regulated psu , nuuk's pages http://myweb.tiscali.co.uk/nuukspot...gainclone6.html
Yes, each board works perfectly, but when they r connected together they don't work...
I want to try 'classic' PSU (no regulators, just cappacitors) but I get +/- 38 volts at rails, is that too much for 3886 (2x2 per channel)???
LM3886 does not need a regulated power supply.Feel free to try +-38 volts(These chips can handle +-42V).However , continous operation at +-38 Volts is only considerable if your loadspeaker impedance is >=8 ohms.LM3886's has an unique Spike protection , which is annoying when turns on , but keeps output transistor array in safe temperature range.
Regards,
Lukas.
Regards,
Lukas.
Just tryed 'classic' (unregulated) PSU everything worked perfectly 😎
Funny thing, regulated PSU works with 3775 😕
Funny thing, regulated PSU works with 3775 😕
Yeah, thats plenty, and did you add the caps as per the datasheet for stability etc...?
Also as per usual with error checking new stuff, grab your multimeter and check every single resistor!
Good luck.
Also as per usual with error checking new stuff, grab your multimeter and check every single resistor!
Good luck.
sith, Are you monster/shine7? or did you buy his PCBs? Or did you fabricate the pcbs?
Afraid I can't help with your problem, just interested in the above.
Afraid I can't help with your problem, just interested in the above.
🙂 no Monster/Shine7 is AlexW from forum here, and no i didn't buy PCB , just did plain old p2p using euro board... 😉
Nah, I'm obsessed with isolating things
As I told classic nonregulated PS works perfectly... I think that 4x3886 is just too much for poor 338's 
Anyway, tnx. to all I think I'll go unregulated....
It can't be too much because I'm using four TDA7294 with +-41V rails regulated with a pair of LM338, and they don't fold back or oscillate even when three of the four TDAs are driving 4 ohms. Input voltage to the regulators is 60V without load and falls to 48V with heavy load. Capacitance is just 20.000uF at the input and 8.400 at the output of each LM338.
The most likely cause for the problem that you describe is oscillation due to bad layout, due to capacitive coupling between ICs through the heatsinks or due to having capacitors of different kinds paralelled everywhere thus creating resonant networks.
The most likely cause for the problem that you describe is oscillation due to bad layout, due to capacitive coupling between ICs through the heatsinks or due to having capacitors of different kinds paralelled everywhere thus creating resonant networks.
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