a questione

Al Bundy · 27th February 2004, 07:18 AM

hello,

will this schematic work. basically it is peter daniels schematic, i guess.

i am not sure about the 2,2 µF condensator (too small?) and the missing resistor from + input to ground.
i think the 2,2µF is good enough and the missing resistor is ok because i will use a 22k pot.

thank you
al

Al Bundy · 27th February 2004, 07:42 AM

the 2,2µF capacitior is a paper in oil cap

Nuuk · 27th February 2004, 08:35 AM

It will work but 2.2uF may be too small. Only way to tell is build it and see!

richie00boy · 27th February 2004, 08:45 AM

I would put a 10k resistor from the non-inverting input down to ground. As you have drawn it, there is no way for the non-inverting input to get a DC bias current path.

Using a 10k in this way also allows you to use a linear pot for the volume, as the law will be skewed to an approximate logarithmic curve by the 10k.

Nuuk · 27th February 2004, 08:53 AM

Richie, shouldn't the law faking resistor be about 1/6 of the value of the pot?

In this case I would prefer a 50K (or 47K) pot with a 7K5 resistor to ground.

Al Bundy · 27th February 2004, 12:05 PM

to be honest, i am a little bit confused

the only thing i know about electronics is nothing... well almost nothing

why do i need a shunt resistor if i use a 22k log pot, and why has the shunt resitor to be that small, i.e. 10k?

thank you

al

Ouroboros · 27th February 2004, 12:24 PM

Quote:

Originally posted by Al Bundy
:
why do i need a shunt resistor if i use a 22k log pot, and why has the shunt resitor to be that small, i.e. 10k?

thank you
al

The chip requires that the + and - inputs have a dc path to 0V. If you only have a capacitor then the input doesn't have the correct dc biasing conditions and the chip won't work properly.

A 100k resistor will do, and with a resistor this high, your 2.2uF capacitor will be OK for the LF performance. (and your 22k log pot will work correctly.

GregGC · 27th February 2004, 02:50 PM

Do it this way than.

/Greg

Fishy · 27th February 2004, 06:56 PM

BTW ... is an electrolytic for the 4.7uF ok? (with the +ve side facing the input) or should I use some other type?

Thanks ...
<">++<

Tor M · 27th February 2004, 08:12 PM

Hi!
Just a question, wouldn`t it work to place the cap in front of the pot? Then the pot would make the dc path?

Regards

Tor Martin

27th February 2004, 08:35 AM	#3
Nuuk diyAudio Member Join Date: Feb 2003 Location: Somerset, SW England	It will work but 2.2uF may be too small. Only way to tell is build it and see! __________________ The truth need not be veiled, for it veils itself from the eyes of the ignorant.

27th February 2004, 08:53 AM	#5
Nuuk diyAudio Member Join Date: Feb 2003 Location: Somerset, SW England	Richie, shouldn't the law faking resistor be about 1/6 of the value of the pot? In this case I would prefer a 50K (or 47K) pot with a 7K5 resistor to ground. __________________ The truth need not be veiled, for it veils itself from the eyes of the ignorant.

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27th February 2004, 07:42 AM	#2
Al Bundy diyAudio Member Join Date: Nov 2003 Location: nrw	the 2,2µF capacitior is a paper in oil cap

27th February 2004, 08:45 AM	#4
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	I would put a 10k resistor from the non-inverting input down to ground. As you have drawn it, there is no way for the non-inverting input to get a DC bias current path. Using a 10k in this way also allows you to use a linear pot for the volume, as the law will be skewed to an approximate logarithmic curve by the 10k.

27th February 2004, 12:05 PM	#6
Al Bundy diyAudio Member Join Date: Nov 2003 Location: nrw	to be honest, i am a little bit confused the only thing i know about electronics is nothing... well almost nothing why do i need a shunt resistor if i use a 22k log pot, and why has the shunt resitor to be that small, i.e. 10k? thank you al

27th February 2004, 06:56 PM	#9
Fishy diyAudio Member Join Date: Jan 2004 Location: Calgary	BTW ... is an electrolytic for the 4.7uF ok? (with the +ve side facing the input) or should I use some other type? Thanks ... <">++<

27th February 2004, 08:12 PM	#10
Tor M diyAudio Member Join Date: Oct 2002 Location: Haugesund	Hi! Just a question, wouldn`t it work to place the cap in front of the pot? Then the pot would make the dc path? Regards Tor Martin

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