Author Topic: QRP02 DC out  (Read 15983 times)

0 Members and 1 Guest are viewing this topic.

Offline AudioSpirit

  • Member
  • **
  • Posts: 14
  • Karma: +0/-0
  • Gender: Male
QRP02 DC out
« Reply #15 on: August 12, 2005, 09:04:37 PM »
I installed r19 and r20 not correct.Moved them to other direction.First chanell is fixed,but second still doesn't work.I work on it right now,hope I've not burned lm3886:)

Offline AudioSpirit

  • Member
  • **
  • Posts: 14
  • Karma: +0/-0
  • Gender: Male
QRP02 DC out
« Reply #16 on: August 12, 2005, 09:42:33 PM »
Ok,I fixed all.On second board was bad Ad8620 .I replaced ic and now all is ok.

Offline AudioSpirit

  • Member
  • **
  • Posts: 14
  • Karma: +0/-0
  • Gender: Male
QRP02 DC out
« Reply #17 on: August 12, 2005, 10:01:22 PM »
Actually I like AC level ,it is 0,000V now,under my Fluke 112 measurement level.Unbelivable!
Actually all will be bilded in dual monoblock design inside of Technics SA900 body and hope will looks extremely attractive.Will post more details later.

Offline peranders

  • Administrator
  • Reached Nirvana
  • *****
  • Posts: 1230
  • Karma: +6/-0
  • Gender: Male
  • Forum owner
    • Sjöström Audio
QRP02 DC out
« Reply #18 on: August 13, 2005, 08:51:08 AM »
You will probably experience 0.02-0.08 mV(!) offset. Good to hear that you managed to get it working... I suppose you didn't build as a wrote in the instructions. It's smart to build and test piece by piece just because SMD is a bit harder to troubleshoot.

So fix first the PS and +- 12 volt, then the IC1 and last the LM3886.
/Per-Anders Sjöström, owner of this forum

Homepage with my DIY hifi stuff

Offline AudioSpirit

  • Member
  • **
  • Posts: 14
  • Karma: +0/-0
  • Gender: Male
QRP02 DC out
« Reply #19 on: August 13, 2005, 10:44:09 AM »
Ooops.I awake today,bringed amp up und... BUMMM from speakers.I fast disconnected speakers. ad8620 died. I replaced to other now it is again working.But here one dangerous thing which I like to fix.
Here is no defence against AC from IC 1.Can I replace r6 1 kOhm with capacitor? Even tought about I can burn my loudspeakers make me very nervous...

Offline peranders

  • Administrator
  • Reached Nirvana
  • *****
  • Posts: 1230
  • Karma: +6/-0
  • Gender: Male
  • Forum owner
    • Sjöström Audio
QRP02 DC out
« Reply #20 on: August 13, 2005, 12:58:45 PM »
Are you complete sure that the +-12 V is working properly? When everything work perfectly you'll have a silent and smooth startup and also power down.

I have never distroyed and opamp in such position and nor has the other builders.

I'll guess something isn't solder properly or simply forgotten or some parts are located wrong.The AD8620 has no startup transient what so ever and below 12 volts the LM3886 is shut down so both the servo and the input buffer are working proberly before the LM3886 is.

I suggest that you measure the startup transient at pin1 IC1.

Since you have 1 kohms as R6 a coupling capacitor must be pretty big. Sure you can have it but it's a bit a waste in the same time.
/Per-Anders Sjöström, owner of this forum

Homepage with my DIY hifi stuff

Offline AudioSpirit

  • Member
  • **
  • Posts: 14
  • Karma: +0/-0
  • Gender: Male
QRV-02
« Reply #21 on: September 12, 2005, 10:15:05 PM »
Ok amp is up and running for over 2 weeks now,and I have only positive emotions. Very nice and clean sound,excellent dynamic. I never expected such quality from LM3886! Highly Recommended. 10/10

Offline peranders

  • Administrator
  • Reached Nirvana
  • *****
  • Posts: 1230
  • Karma: +6/-0
  • Gender: Male
  • Forum owner
    • Sjöström Audio
QRP02 DC out
« Reply #22 on: September 13, 2005, 06:48:42 AM »
Good to hear that everything are working alright.
/Per-Anders Sjöström, owner of this forum

Homepage with my DIY hifi stuff