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Old 25th June 2011, 11:09 PM   #101
hurtz is offline hurtz  Germany
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Join Date: Jun 2010
Ok, the thread just developed a life of its own

I try to get one thing after another.

Value of Ci.

The Cin/Rin combination gives me a cutoff of ~0.00072Hz with 4.7uF/47k
So I should probably move to the more widely accepted: ~0.00154Hz with 4.7uF/22k

Therfore I declare my Ci to be ~ 0.000769Hz
Since I would like to keep Ci as small as possible (sizewise) I choose Ci to be 33uF (as enzoR suggested)
So the formula gives me an Ri of: 62.7k
The cap will have a diammeter of 12mm which will be a huge pain arranging on the board.

Quote:
Originally Posted by AndrewT
Add RF attenuation across Rin.
I guess an additional parallel 50pF will do?

Quote:
Originally Posted by DaveR
Will Rm fit under the chip instead?. Looks like that could free up a lot more space.
It would, but it would also elevete the chip by approx 2.5mm and I think it might be better to keep the track-length down.

Quote:
Originally Posted by infinia
Also the Zobel needs to be shown at the IC ground not at the speaker.
If I understand you correctly you say the zobel should tie in closer to the chip 0V?
Also Ci will change as soon as I have succesfully rearanged the parts to allow for Ci.

Additionally enzoR volunteered to measure my design (with some fancy audio analyzer) against a p2p lm3886, so since most of the design-changes about the ground are more or less surgical, I'd like to wait for the test results, to for one get a better understanding where negative influences come from and on the other hand to see how bad my grounding scheme really is >.<


cheers!

P.s.
However I think suggestions can be put in until monday.
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Old 25th June 2011, 11:22 PM   #102
enzoR is offline enzoR  Netherlands
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Oh yeah, i think michaels comment about the jumper on the chip gnd line is a good one. Rather get rid of it, maybe make a small narrowing in the trace instead.

And rf attenuation across Rg can be done in parallel underneath if required i guess. Not much board space anymore! lol. Amazes me how much u can fit on 40x30mm!

Last edited by enzoR; 25th June 2011 at 11:25 PM.
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Old 25th June 2011, 11:31 PM   #103
hurtz is offline hurtz  Germany
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Ah btw, forgot to mention, I modified my laminator today, and it works like a charm, 0.07mm pitch no problem (no typo ) and 0.12mm as track width worked also very well.

For those interested in the details:
Samsung ML-1865 Printer,
reichelt-catalog Paper (good distributor in germany, has moderately glossy paper)
HAMA A40 DIN A4 Laminator ~17€

cheers!

P.s jumper is fixed, new PCB-update tomorrow.

Last edited by hurtz; 25th June 2011 at 11:36 PM.
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Old 25th June 2011, 11:44 PM   #104
enzoR is offline enzoR  Netherlands
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So toner transfer method? Thats amazingly good.

Im lazy! I just print on normal white paper, then place it toner side against the photoresist and shove it in my uv scanner. Learnt from a friend, i never believed him until i saw with my own eyes how good the results were!

But still, even though you can achieve such fine pitch, its better to space them as much as possible apart (leakages, dirt ect..)
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Old 26th June 2011, 11:41 AM   #105
hurtz is offline hurtz  Germany
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Hmm a scanner, good to know! I never wanted to buy two chemicals to do the job ;-)

New components/updates:
Code:
Ci: 33uF T+F bipolar d12mm
Ri: 63.4k

Cd: 50pF
Rin: 22k
Now with 100% more Ci and at least 70% more standing resistors.
Also renamed Rg to Rin, seemed more sensible.
Hmm so much free space :-)

AMP: v5.7
Click the image to open in full size.

cheers!
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Old 26th June 2011, 11:52 AM   #106
AndrewT is offline AndrewT  Scotland
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Location: Scottish Borders
Hi,
1/4inch spade terminal pads can be inserted at Vn & Vp, if placed top to bottom.
Similarly 1/4 spade terminal pads for Power Ground between Vp & Vn but placed left to right. This is where you will bring in the twisted triplet from the PSU.

Add a pair of pads for a 10r resistor in the SIG GND to Gnd trace.
This is not needed if you build only monoblocks. If you build a chassis with two or more of these PCBs inside then the resistor is used to attenuate the current in the ground loop so formed.

I would move RnL (R//L) off board.
__________________
regards Andrew T.
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Old 26th June 2011, 04:16 PM   #107
hurtz is offline hurtz  Germany
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Join Date: Jun 2010
Quote:
Originally Posted by AndrewT View Post
Hi,
1/4inch spade terminal pads can be inserted at Vn & Vp, if placed top to bottom.
Similarly 1/4 spade terminal pads for Power Ground between Vp & Vn but placed left to right. This is where you will bring in the twisted triplet from the PSU.

Add a pair of pads for a 10r resistor in the SIG GND to Gnd trace.
This is not needed if you build only monoblocks. If you build a chassis with two or more of these PCBs inside then the resistor is used to attenuate the current in the ground loop so formed.

I would move RnL (R//L) off board.
Noted, but I like the screw-down terminals better. Rearranged them anyways, now looks a little bit cleaner.

And for now I'd like RnL to stay on the board, will wait for the test-result

No mono-blocks, so added resistor, new part:
Rb2: 10R

AMP: v5.8
Click the image to open in full size.
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Old 26th June 2011, 06:29 PM   #108
enzoR is offline enzoR  Netherlands
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is Ci that huge?
MULTICOMP|NP100V336M13X20|CAPACITOR, N/P, 33UF, 100V | Farnell Nederland
i thought it would fit in the original space...
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Old 26th June 2011, 06:36 PM   #109
hurtz is offline hurtz  Germany
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Sadly so, the component you linked has is even 1mm bigger in diameter, my Ci now is 12mm diameter, so considereing the board has a length of 40mm, its nearly one third...

cheers.
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Old 26th June 2011, 06:47 PM   #110
enzoR is offline enzoR  Netherlands
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crap, ok well Rin is just 1/4 W btw, and Rz too i believe. A quick browse of the datasheet i couldnt find it though. I will be jumping RnL btw because my inductor is pretty huge aswell. I believe 15mm x 9mm...
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