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AD815 - Page 2

post #16 of 20
10/31/09 at 2:14pm

AD815

Thanks you very much.
The Cout is 4.7uf/01.uf not 33uf. The gain of this pre 3x.
LL
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post #17 of 20
10/31/09 at 2:30pm
Quote:
Originally Posted by Mr.Unknown View Post
Thanks you very much.
The Cout is 4.7uf/01.uf not 33uf. The gain of this pre 3x.
With that output capacitor(s), you either have to bypass the caps (but check for DC offset first) or use a larger cap. With your 100R phones I'd recommend no smaller cap than 100 uF. Here's a cut off frequency calculator Guitar Pedals: R-C Filter Calculator . What's the value of your output resistor? Do you use a resistor to the input to balance the bias currents?
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post #18 of 20
10/31/09 at 8:43pm
I have aerovox 40uf, si I will use it. Dc ofset is about xxmV, I don't want to "burn" my headphone. What about the gain, 3x is enough.
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post #19 of 20
11/1/09 at 5:38am
Quote:
Originally Posted by Mr.Unknown View Post
I have aerovox 40uf, si I will use it. Dc ofset is about xxmV, I don't want to "burn" my headphone. What about the gain, 3x is enough.
IMO 3x is plenty enough with 100R phones, if they're not extremely unefficient. According to the data sheet AD815 seems to be stable at low gain and no extras should be needed. There will probably be a little overshooting. I've found that overshooting might sound a little harsh (I'm not sure, maybe placebo). The overshooting can be dealt with by adding a 5 pF cap in parallel with the feedback resistor, R5 in the schematic. Another way to deal with it is to increase the gain and change the 660R (R5) resistor to 1k5.
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post #20 of 20
11/25/09 at 12:01am
I will test this circuit after finishing the Carlosfm . It is suitable for Current FB opamp. The Dc offset is very small.
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