Need volume control on active filter

Buzzy · 06:34 AM

Hi ! I have built an active high pass filter exactly as shown in the figure below for my UCD 400 amp. ( figure done by Collo from his website)

I wanted to add a volume control. I wired RCA input---> high pass filter ---> potentiometer. But the volume is so low that i have to put my ear on the speaker to hear. The output from the high pass filter is connected to input of the pot. The wiper/output of the pot is connected to the input of the amp. Ground of the pot and the high pass filter are connected together. May I know what i have done wrongly ?

Is there a way to add volume control to the circuit above ?

picowallspeaker · 27th December 2009, 06:55 AM

Sorry , but I think you'll need to add another capacitor on pin 7 (or 1) of the IC . Maybe you could just move the 1uF of the input to the output ,depending on which circuit it's attached to.
Bye

Buzzy · 27th December 2009, 03:32 PM

Quote:

Originally Posted by picowallspeaker

Sorry , but I think you'll need to add another capacitor on pin 7 (or 1) of the IC . Maybe you could just move the 1uF of the input to the output ,depending on which circuit it's attached to.
Bye

May i know what is that extra capacitor for and what value should it be ?

The amplifier is a hypex UCD 400. The amp has 3 inputs: in+, in- and signal ground.

Buzzy · 28th December 2009, 02:52 AM

Erm......have I confused you guys ?

paulb · 28th December 2009, 01:47 PM

First check if you have 0V DC at the output, or close to it. If you have a large DC (more than a few 10s of millivolts), check your circuit connections, especially power supply.
The filter circuit has a gain of unity, so it should not be reducing the amplitude of anything above its cutoff frequency. What frequency is it set to? If you are not driving a tweeter directly (which could be damaged by low frequencies), bypass the filter and go directly from the source to the potentiometer and see what you get.

Davey · 29th December 2009, 04:40 AM

I would attach your volume control as the first component in the circuit. (Before the 1uF capacitor.) (Even externally in a different box would be fine.)

Wire it like the second example in Figure 6 on this page:

Potentiometers (Beginners' Guide to Pots)

That should work for you.

Dave.

27th December 2009, 06:30 AM	#1
Buzzy diyAudio Member Join Date: Apr 2007	Need volume control on active filter Hi ! I have built an active high pass filter exactly as shown in the figure below for my UCD 400 amp. ( figure done by Collo from his website) I wanted to add a volume control. I wired RCA input---> high pass filter ---> potentiometer. But the volume is so low that i have to put my ear on the speaker to hear. The output from the high pass filter is connected to input of the pot. The wiper/output of the pot is connected to the input of the amp. Ground of the pot and the high pass filter are connected together. May I know what i have done wrongly ? Is there a way to add volume control to the circuit above ? Last edited by Buzzy; 27th December 2009 at 06:34 AM.

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27th December 2009, 06:55 AM	#2
picowallspeaker diyAudio Member Join Date: Apr 2007	Sorry , but I think you'll need to add another capacitor on pin 7 (or 1) of the IC . Maybe you could just move the 1uF of the input to the output ,depending on which circuit it's attached to. Bye

28th December 2009, 02:52 AM	#4
Buzzy diyAudio Member Join Date: Apr 2007	Erm......have I confused you guys ?

28th December 2009, 01:47 PM	#5
paulb diyAudio Member Join Date: Jun 2001 Location: Calgary	First check if you have 0V DC at the output, or close to it. If you have a large DC (more than a few 10s of millivolts), check your circuit connections, especially power supply. The filter circuit has a gain of unity, so it should not be reducing the amplitude of anything above its cutoff frequency. What frequency is it set to? If you are not driving a tweeter directly (which could be damaged by low frequencies), bypass the filter and go directly from the source to the potentiometer and see what you get.

29th December 2009, 04:40 AM	#6
Davey diyAudio Member Join Date: Dec 2001 Location: Bremerton, WA.	I would attach your volume control as the first component in the circuit. (Before the 1uF capacitor.) (Even externally in a different box would be fine.) Wire it like the second example in Figure 6 on this page: Potentiometers (Beginners' Guide to Pots) That should work for you. Dave.

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