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Old 30th July 2012, 09:14 PM   #21
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Default First power up

After branching transformers you can fire up modules (be sure they're heatsinked.... ) with all inputs and outputs disconnected.

You should hear relais click, this is the first good news, it means modules are working and no serious DC is present at output.

Keeping modules powered on we then proceed to measure DC offset at output tabs.

It should measures less then 20mV and with shorted inputs less then 10mV.

If relais don't click don't panic, power off modules and ask help on this thread.

Disclaimer

This tutorial it's not the unique way to build the amp and it's not necessarily the best one but it worked for me several times.
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Old 30th July 2012, 11:36 PM   #22
bcmbob is offline bcmbob  United States
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My only suggestion so far is to go through the tutorial several times before starting the build. This morning I sent Dario a PM questioning the "thermals" reference in post #10. He referred me back to post #7 where I had completely blown past the explanation. So be attentive. Don't hesitate to post problems and questions.

I also had mentioned the need for some pre-planning if builders think they will mount the LED on a front panel. Dario made note of that in the thread.

Will read through again tonight, but I can't imagine a more thorough and detailed guide.

It's gonna be great fun and rewarding!
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Old 31st July 2012, 12:05 AM   #23
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Dario,

If I may suggest, this would be a good time to lay out the alternative build choices in one place;

Optional capacitors
advantage and disadvantage of the C9 - R10 choice
alternative compensation capacitors
orientation of premium parts

That way, everything is together in one place and easy to find.

By the way, the build looks very good.

Jac
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Old 31st July 2012, 12:33 AM   #24
SoIL4x4 is offline SoIL4x4  United States
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Quote:
Originally Posted by lehmanhill View Post
Dario,

If I may suggest, this would be a good time to lay out the alternative build choices in one place;

Optional capacitors
advantage and disadvantage of the C9 - R10 choice
alternative compensation capacitors
orientation of premium parts

That way, everything is together in one place and easy to find.

By the way, the build looks very good.

Jac
And a complete list of locations for sockets. this way a builder could lay out the socketed positions ahead of time and not have to worry about trying to remember the swap locations while populating the board. This way no leads get accidentally trimmed.

I have a list that I have been carrying around in my pocket of the locations that I have identified (it is written on a copy of the pcb) but I am sure I missed a spot or added one.
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Old 31st July 2012, 01:17 AM   #25
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Quote:
Originally Posted by lehmanhill View Post
Optional capacitors
Otional capacitors C102/C202 are there just beacuse there was space for them but I wouldn't use them unless stability problems arise.

The amp sound better without.

Quote:
Originally Posted by lehmanhill View Post
advantage and disadvantage of the C9 - R10 choice
Functionally both arrangements are identical but the new one makes the circuit less prone to pickup noise.

To my ears it also sound better...

But experimenting with both arrangements is encouraged to confirm the final choice.

Quote:
Originally Posted by lehmanhill View Post
alternative compensation capacitors
Rev C compensation is the original one developed by circuit designer Mauro Penasa, it's a no brainer and sounds great.

FE compensation has been 'guessed' by me via trial and listen and sound more refined in the high range with a tighter bass and (much) wider and deeper soundstage, LinuxGuru simulations and several months of use proved it's stable.

FE compensation can be considered experimental but it's the one I suggest to use.

Quote:
Originally Posted by lehmanhill View Post
orientation of premium parts
Amtrans are oriented exactly like FKP2s
150pF KP1834 have a yellow mark (see picture)


Click the image to open in full size.

Click the image to open in full size.

Quote:
Originally Posted by SoIL4x4 View Post
And a complete list of locations for sockets.
I don't know how much it can be useful since it depends on what you want to experiment with...

BTW

Click the image to open in full size.

The area in the cyan rectangle is the most interesting to explore.

The positions that should be socketed for sure are C9 and R10 to determine which C9/R10 arrangement it's the best one.

Builders that don't want to experiment are encouraged to use the alternate arrangement

Click the image to open in full size.
Attached Images
File Type: jpg Sockets.jpg (361.7 KB, 1779 views)
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Last edited by ClaveFremen; 31st July 2012 at 01:24 AM.
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Old 31st July 2012, 01:43 AM   #26
bcmbob is offline bcmbob  United States
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Dario, orientation at R13 appears a bit confusing.
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File Type: jpg Sockets 2.jpg (39.7 KB, 60 views)
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Old 31st July 2012, 01:47 AM   #27
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Quote:
Originally Posted by bcmbob View Post
Dario, orientation at R13 appears a bit confusing.
It's because R13 can accept both Mk132 an 0309 resistors.

The left orientation is for Caddocks while the right one is for KOAs.

Inviato dal mio LT22i con Tapatalk 2
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Old 31st July 2012, 09:33 AM   #28
bcmbob is offline bcmbob  United States
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Understood.
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Old 31st July 2012, 10:41 AM   #29
bcmbob is offline bcmbob  United States
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Here is a note on mounting the LM3886 as shown in post #18. This came up back in the MyRef V1.2/V1.3 threads. Minor alignment problems can be corrected by insuring there is a little stand-off from the board. When making measurements to locate where to drill the hole in the heatsink, a spacer like a matchstick or toothpick will ensure there is some flexibility on the pins - which need to protrude completely through the holes - but horizontal of chip leads should not be flush to the PCB.

Having the standoffs mounted at this step is important. Also try to think about the need for any clearance between the bottom of the heatsink (if needed) and the chassis that will house the amp. Spacers may be useful here also. Dry/cold fit everything before drilling and/or applying solder.
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File Type: jpg Up2.jpg (87.4 KB, 111 views)
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Last edited by bcmbob; 31st July 2012 at 10:57 AM.
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Old 31st July 2012, 11:56 AM   #30
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The LM3886 Eagle component I've used in RC boards it's a new one derived from National one, different from all previous, and have exact holes.

It will be easier to desolder the part if needed and LM3886 will slide in without alignment problems.

For the same reason the LM3886 will no more stand up without soldering like in Bob's pictures.

Also I've aligned component so that the LM3886 edge will have at least half millimeter from board's edge so that it should adehere perfectly to heatsink.
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