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Old 11th December 2012, 10:39 AM   #851
AndrewT is offline AndrewT  Scotland
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Ah,
This is what I brought up a long time ago.
Probably not this Thread.
The resistors must be right next to the -IN & +IN Pins.
Is Atupi reporting that he has moved the resistor closer to the -IN Pin?
And the result is improved sound quality?

Is he reporting a change to the value of the RC time constant?
Or, has he retained the 86ms RC? 390r & 220uF = 86ms
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Old 11th December 2012, 10:46 AM   #852
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Quote:
Originally Posted by AndrewT View Post
The resistors must be right next to the -IN & +IN Pins.
KSTR's suggestions should have the goal of 'achoring' one of C9's plates to ground so to pickup less noise.

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Is Atupi reporting that he has moved the resistor closer to the -IN Pin?
And the result is improved sound quality?
Not exactly, the RC boards have the option to mount C9/R10 in both ways.

Yes, the sound subjectively improves.

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Is he reporting a change to the value of the RC time constant?
Or, has he retained the 86ms RC? 390r & 220uF = 86ms
Only positions are swapped, values are My_Ref's default ones.
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Old 11th December 2012, 10:52 AM   #853
atupi is offline atupi  Romania
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Thanks Dario for clariying the discussion.
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Old 11th December 2012, 11:19 AM   #854
AndrewT is offline AndrewT  Scotland
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Does swapping the locations of C & R put the resistor closer to the -IN Pin?
I think the answer is "yes".
I do not agree that anchoring one of the capacitor plates to Signal Ground has a more significant effect. I would argue that the anchoring has an insignificant effect.
I would also argue that a bigger effect would be brought about by physically moving the resistor to be actually on the -IN Pin rather than 15mm away from it.
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Old 11th December 2012, 12:05 PM   #855
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Quote:
Originally Posted by AndrewT View Post
Does swapping the locations of C & R put the resistor closer to the -IN Pin?
I think the answer is "yes".
Absolutely.

Quote:
Originally Posted by AndrewT View Post
I do not agree that anchoring one of the capacitor plates to Signal Ground has a more significant effect. I would argue that the anchoring has an insignificant effect.
I don't know but also Mauro found some merit in it.

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I would also argue that a bigger effect would be brought about by physically moving the resistor to be actually on the -IN Pin rather than 15mm away from it.
Can you elaborate a bit?

Thanks

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Thanks Dario for clariying the discussion.
You're welcome
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Old 11th December 2012, 12:26 PM   #856
AndrewT is offline AndrewT  Scotland
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the -IN Pin and to a lesser extent the +IN pin are very suceptible to parasitics, especially capacitance.

The further away the resistor, the longer the trace (and component if swapped the wrong way around). That longer trace has more parasitics than a 1mm trace to an adjacent resistor.

That is the problem that must be avoided in laying out any opamp or power amp traces.
Minimise parasitics on the +IN and -IN Pins.

I am sure I have explained this more than a few times and I am also pretty sure I have argued this on a MyRef Thread.
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Old 11th December 2012, 12:59 PM   #857
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Quote:
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the -IN Pin and to a lesser extent the +IN pin are very suceptible to parasitics, especially capacitance.
Sure, now I understand, thanks

Click the image to open in full size.

I've taken it in in account (see the IN- trace) but it's more difficult for IN+, what would you have done differently?
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File Type: jpg My_Ref_FE RC - PCB.jpg (66.5 KB, 445 views)
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Old 11th December 2012, 01:41 PM   #858
AndrewT is offline AndrewT  Scotland
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I can't make out the traces well.
But I read it as capacitors near the -IN & +IN Pins.
It should be resistors next to the Pins.
100r, or 200r, smd at the Pins or under the PCB using PTH for shortest (pin to resistor) routes would allow anything to be hung on the other side of the resistors.
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Old 11th December 2012, 01:52 PM   #859
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I understand...design choices are often compromises.
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Old 14th December 2012, 12:30 PM   #860
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no updates for 3 days, let me fix that...

at last, I have added copper shields, a grounding wire and desoldered few sockets! WOW...The sound has dramatically improved and the soundstage became extremely wide and deep, moreover, I felt as the output power has doubled or even more kidding! no improvements here, it's already good and no hum from toroids as I reported earlier, so just aesthetic addons.

some pics below:
Attached Images
File Type: jpg IMG_0043.jpg (707.4 KB, 184 views)
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File Type: jpg IMG_0053.jpg (708.8 KB, 80 views)
File Type: jpg IMG_0055.jpg (376.1 KB, 78 views)
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