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A75 front-end unwanted output signal
A75 front-end unwanted output signal
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Old 14th November 2007, 06:01 AM   #1
ckwong99 is offline ckwong99  Hong Kong
diyAudio Member
Join Date: May 2005
Location: HK
Default A75 front-end unwanted output signal

Hi All,

Can anyone help me about my A75 , it almost be completed but it response with square wave input would have a little spur signal in output waveform raising edge, out of this all is normal and well .

Actually, I do not use folded cascode (without R21 & C6) and the feedback resistor R81=700 ohm. When measuring the front-end output did not connect the power FET but have C8 and R31 connected to GND.

How can I vanish this unwanted signal and why it will happen ?

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Old 29th December 2007, 10:28 PM   #2
norb is offline norb  Germany
diyAudio Member
Join Date: Mar 2007
Location: Germany
hi ckwong99,

i have attached a picture with a signal that i suppose is what you describe in you request.
If it is like this, there is no reason to be afraid, this is normal behaviour as the amp tries to adapt to the new voltage level of the signal as fast as possible. Since the amp is not indefintely fast - and no amp is - you will see this slight overshoot.

So enjoy your A75, itīs a great amp and a ear-opening experience.

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File Type: jpg square_wave.jpg (39.3 KB, 122 views)
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