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Old 25th October 2012, 09:36 AM   #11
AndrewT is offline AndrewT  Scotland
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I see no link, I see no schematic.
Where have you attached your schematic.
Where are the component labels?
elco=1uf ?

do you mean you have used an electrolytic instead of a plastic film capacitor for a 1uF (not f, f=femto).
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Old 25th October 2012, 09:52 AM   #12
yd1cvj is offline yd1cvj  Indonesia
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Andrew T
At thread #7, do you see 3 pictures ?
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Old 25th October 2012, 10:07 AM   #13
AndrewT is offline AndrewT  Scotland
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no.
I cannot see any attachments, nor pics.
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Old 25th October 2012, 10:25 AM   #14
yd1cvj is offline yd1cvj  Indonesia
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Upload again the scheme :
Click the image to open in full size.
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Old 26th October 2012, 08:17 AM   #15
AndrewT is offline AndrewT  Scotland
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Why do I need to upload?
I just want to see your attachment.
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Old 26th October 2012, 10:57 PM   #16
jaycee is offline jaycee  United Kingdom
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that schematic is visible for me
It's slightly unusual with such high input impedance and feedback resistor. I can't think of any good reason to do that rather than use the more usual 22K. Still, if it works and sounds good, it's OK

The input coupling capacitor, it depends on your source. If it has a low DC offset to start with, you can get away with it. Personally I would also like to have an input lowpass filter for RF rejection.
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Old 26th October 2012, 10:58 PM   #17
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He has uploaded it again, here is the link http://i885.photobucket.com/albums/a...21025-1718.jpg
No idea why doesn't it work for you, AndrewT.
Regards, Vic.
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Old 27th October 2012, 09:18 AM   #18
AndrewT is offline AndrewT  Scotland
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Diyaudio attachments work perfectly and last for as long as Diyaudio lats.

Remote servers should be banned.
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Old 17th November 2012, 07:51 AM   #19
yd1cvj is offline yd1cvj  Indonesia
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IMG02124-20121117-1438.jpg IMG02126-20121117-1440.jpg

Alummunium case has arrrived and I got 400watt smps power supply 24 volt. I will modified become +/- 24 volt. I plan to power 4pcs chip. Two parallel for each channel.
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Old 17th November 2012, 08:42 AM   #20
Jay is offline Jay  Indonesia
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Quote:
Originally Posted by jaycee View Post
It's slightly unusual with such high input impedance and feedback resistor. I can't think of any good reason to do that rather than use the more usual 22K.
To balance the two inputs, the FB resistor (at -in) will usually be equal to the other resistor (at +in). The resistor at +in is connected to ground. The higher the resistance, the better the noise floor, as can be seen in simulators.

Beside lifting the input impedance, it is often mentioned in "Design Example" of a chip datasheet to use such a high resistance (usually mentioned as 100k) to lower output offset.

I have tested many resistance and the offset differences are not big. Even the lowest offset was not the best sound to my ears.

But with FB resistance as high as 100k you can get away with 4u7 MKP in the FB path. May be it is audible if compared with low quality electrolytic? (mine was BG, so no worse)

Last edited by Jay; 17th November 2012 at 08:44 AM.
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