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Chip Amps Amplifiers based on integrated circuits

Newbee build: PA03 amp (LM4780)
Newbee build: PA03 amp (LM4780)
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Old 28th October 2015, 06:08 PM   #21
daanm is offline daanm  Norway
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Yep Clog... that's me. I added the flag after your post ;-).
The amp looks like pretty closed to "finished".... or not?
What is your opinion? Is it "okay" or "just fine" or "nice" or "superb" or...... did it blow your socks of?
Can't wait to hear more about it.
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Old 28th October 2015, 07:52 PM   #22
redjr is offline redjr  United States
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Quote:
Originally Posted by daanm View Post
Yep Clog... that's me. I added the flag after your post ;-).
The amp looks like pretty closed to "finished".... or not?
What is your opinion? Is it "okay" or "just fine" or "nice" or "superb" or...... did it blow your socks of?
Can't wait to hear more about it.
Blew my socks off!
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Old 29th October 2015, 09:46 AM   #23
clog is offline clog  Netherlands
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Redjr, afaik you built both the PA03 and Rudi's Symasym at about the same time. I'm very interested in your opinion on both amps. By coinicidence i also have Rudi's black beauty pcb's laying around. Still unpopulated.
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Old 29th October 2015, 09:43 PM   #24
redjr is offline redjr  United States
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Quote:
Originally Posted by clog View Post
Redjr, afaik you built both the PA03 and Rudi's Symasym at about the same time. I'm very interested in your opinion on both amps. By coinicidence i also have Rudi's black beauty pcb's laying around. Still unpopulated.
Yes I did. And of late I haven't had time to listen to either of them for very long! Too busy with work, life and personal family matters that have taken me away from home lately. Hopefully, my schedule will slow down soon.

Rick
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Old 29th October 2015, 10:05 PM   #25
daanm is offline daanm  Norway
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Quote:
Originally Posted by clog View Post
Redjr, afaik you built both the PA03 and Rudi's Symasym at about the same time. I'm very interested in your opinion on both amps. By coinicidence i also have Rudi's black beauty pcb's laying around. Still unpopulated.
Yes Redjr plz plz
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Old 30th October 2015, 03:17 PM   #26
clog is offline clog  Netherlands
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Default magic smoke ???

Episode 5

Inserted last parts into the board. As I said before the only hurdle was the exact mounting of the heat sink and the positioning of the LM4780. My 35W soldering iron has enough muscle to handle 99 percent of the joints but soldering parts to the ground plane took too much time. For these rare cases I used my antique soldering gun (oh horror!!!).

Okay now what. There it is in front of me. My first completed and professional looking amplifier board. To prevent disappointment perhaps it would be wise to stop here, frame it and hang it on the wall of my living. No won't happen.

In his build guide Pavel advises to test it with a Variac which I don't have. Now it's time to put the bulb tester into practice. I decided not to put everything in a box because in case of sparks and smoke it would be all for nothing. So I mounted everything on a piece of chipboard.

For a while I was unsure how to connect the secondaries of my transformer but I got help. Recipe is “one winding with dot to ground and the other winding "no dot" to ground”. Again a teachable moment for me as I learned something about transformer phasing and the dot notation. I suppose it's easy to go wrong here because there are no clear markings on the dual secondary windings of my transformer. Well if you know where to look and know what to look at …… !!

Time to test the thing. I hooked up the bulb tester with a 25W bulb. Now don't laugh, newbee action here. I have read that big capacitors can explode so to be on the safe side I put safety goggles on. Seeing that my wife asked what on earth I was doing.

I have to confess that I had shaky hands when I put the mains plug of the PA03 in the bulb tester and flipped the switch. The bulb was flashing for two seconds and then dimmed down to such a level that it appeared to be off. After a short time the relays clicked and I thought……... job done. I left it on for about half an hour, no magic smoke came out. The bulb remained lukewarm. So I guess it's time to let the little bird sing its pretty song.

In the pictures: PA03 on testboard, all the parts on board (1) and (2),

To be continued ......
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Old 30th October 2015, 03:33 PM   #27
AndrewT is offline AndrewT  Scotland
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Measure some voltages while it is still powered up via the Bulb.

Check supply rails to ground and across each other.
Check output offset and output noise with the input shorted with a dummy/zeroOhm plug.
If all OK , power down.

What size of Mains fuse is fitted? Close rated, or enormous?

Now power up direct off Mains.
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Old 30th October 2015, 07:12 PM   #28
JammyBStard is offline JammyBStard  United Kingdom
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Looking good

Sent from my SM-G920F using Tapatalk
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Old 30th October 2015, 08:05 PM   #29
loafimus is offline loafimus  United States
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Newbee build: PA03 amp (LM4780)
My PA03 just shipped. Can't wait to get started working on it. Let us know how everything turns out, I'm following this thread pretty closely!
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Old 31st October 2015, 12:27 AM   #30
redjr is offline redjr  United States
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Excellent! You can also test the PSU alone by removing the fuses.
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