My "audiophile" LM3886 approach - Page 51 - diyAudio
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Old 17th August 2005, 03:16 PM   #501
inguz is offline inguz  United States
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Default What loudspeakers are you using?

I'd be interested to hear anyone's reports of this amp with different speakers. Good,bad?

With a fullrange driver I'm convinced it should be great (how about some of those Gallo A'Divas?) -- but I'm looking at a bi-amped system (passive crossover in Linn loudspeaker) and wondering whether that'll work good...
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Old 17th August 2005, 03:21 PM   #502
troystg is offline troystg  United States
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I emailed instead of posting.
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Old 17th August 2005, 03:23 PM   #503
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Quote:
Originally posted by rabstg
I emailed instead of posting.

I marked you down Troy. Thanks! I will see what I can do about parts.
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Old 17th August 2005, 03:25 PM   #504
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Default I think I am getting close

Sorry about the large image, I just want people to be able to see things clearly.

I think this is just about ready...

Edit: Forgot the GND trace back to star ground for the LM318 Fixed it.

Click the image to open in full size.
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Old 17th August 2005, 03:49 PM   #505
troystg is offline troystg  United States
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Hi Russ-

It looks very nice so far.

Quick questions.

1. Is the beta gonna be double sided? (not that it matters)
2. Is pin two of the LM3886 removed, bent out of the way?

It appears that the pwr trace contacts the hole for pin 2, where-as pin 6 has the spacing around it.
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Old 17th August 2005, 03:53 PM   #506
UnixMan is offline UnixMan  Europe
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Quote:
Originally posted by analog_sa

Probably not possible. The 3886 won't mind a shorted output as it's got a good protection but the circuit won't reallly 'settle' as the 318 will be deprived of feedback. The thump may be reduced but not eliminated.
You're Right. But I was thinking about some trick 'round this... that's not easy, though.

mmmh... let' see... maybe... could something like this work?

before power-on (initial status):
  • a first relay keeps the output shorted (this one -together with some fuse in series with the rectifier- is the one that will take care of speaker protection in case of any major fault with DC at the output...);
  • a second relay keeps a local NFB loop around the LM318 closed; this (temporary) loop will take care of keeping the 318 output (and thus the global output) at zero during the power-on transients;

power-on sequence:
  • circuit is powered on, and given time to settle down;
  • the first relay is activated. The output is no longer shorted, and the global NFB loop become effective. There may be a minor (?) transient, but the local loop is still in place and should avoid weird things from happening... :-?
  • after some time to allow for the circuit to settle down, also the second relay is activated and the temporary local loop around the LM318 is removed. The global loop is now in place and effective, so again there should be no problems... :-?
  • ok, time to light up a "ready" LED!

Unless I have overlooked something, I guess it should work...

Mauro, what do u think? Any better idea?
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Old 17th August 2005, 03:54 PM   #507
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Quote:
Originally posted by rabstg
Hi Russ-

It looks very nice so far.

Quick questions.

1. Is the beta gonna be double sided? (not that it matters)
2. Is pin two of the LM3886 removed, bent out of the way?

It appears that the pwr trace contacts the hole for pin 2, where-as pin 6 has the spacing around it.

It is this double sided design from the previous post. The single sided board is already protoyped and tested, no need for a beta test there.

The NC pins on the LM3886 are truly NC, so no need to treat them specially at all, just solder them as usual.

Cheers!
Russ
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Old 17th August 2005, 04:39 PM   #508
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Default is this too late???

Hi Russ,

Is this too late for the beta testing volunteer?? I would love to test your amp...

please count me in...

Thanks,
Madhu.
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Old 17th August 2005, 05:48 PM   #509
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Nope its not too late, anyone who can pay by paypal is welcome to participate in the beta test I will have to cost in a day or two.
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Old 17th August 2005, 05:50 PM   #510
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Default Last chance for review.

Unless I here there is a problem with this 2 sided layout in the next couple of hours this is what I will order for the beta test.

Cheers!
Russ
Click the image to open in full size.
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