LM3875 Volume pot

hotscot · 19th January 2007, 06:21 PM

A value of 10K is often suggested but I could only find a 100K value.

Safe to use?

Alan

impsick · 19th January 2007, 10:02 PM

sure

AndrewT · 20th January 2007, 09:30 PM

Hi Hotscot,
How have you assembled your chipamp?
inverting, non-inverting, DC block on NFB, DC block on input, Zin, NFB resistor values,

All the above will affect the DC output offset and they interact with what source impedance/resistance the amplifier input sees.

If you want to use a passive attenuator then Zin>=5times the attenuator resistance.

attenuator resistance >=5times the source resistance.

5times is the minimum, but 10times is better.

A disadvantage of using high attenuator resistance is loss of treble from the amplifier. Careful selection of component values can avoid many of the problems.

19th January 2007, 06:21 PM	#1
hotscot diyAudio Member Join Date: Aug 2004 Location: California	LM3875 Volume pot A value of 10K is often suggested but I could only find a 100K value. Safe to use? Alan

19th January 2007, 10:02 PM	#2
impsick diyAudio Member Join Date: Dec 2006	sure __________________ "Nothing happens for a reason. There are just reasons why things happen." Quote me on that. http://stores.ebay.com/AudioGrade?_rdc=1

20th January 2007, 09:30 PM	#3
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Passive Attenuator Hi Hotscot, How have you assembled your chipamp? inverting, non-inverting, DC block on NFB, DC block on input, Zin, NFB resistor values, All the above will affect the DC output offset and they interact with what source impedance/resistance the amplifier input sees. If you want to use a passive attenuator then Zin>=5times the attenuator resistance. attenuator resistance >=5times the source resistance. 5times is the minimum, but 10times is better. A disadvantage of using high attenuator resistance is loss of treble from the amplifier. Careful selection of component values can avoid many of the problems. __________________ regards Andrew T.

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