Tone Control - Volatage range for TL072/LF252-N - Page 2 - diyAudio
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Old 16th May 2013, 01:35 PM   #11
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Big thanks to everyone who helped me! This is my first time trying out making audio circuits. I made my first chipamp using TDA2009A. It works perfectly with very minimal noise. I can only hear it its really quiet and I need to put my ear on the speakers to hear it. I guess it has to do with my PSU. I used a cheap ATX PSU.

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Old 16th May 2013, 02:28 PM   #12
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Your welcome
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Old 17th May 2013, 01:05 AM   #13
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What quad JFET-input opamps could be used in place of the TL072/LF353N?
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Old 17th May 2013, 02:09 AM   #14
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Sorry for being so noob. Just got a few more questions:

Click the image to open in full size.

What is the polarity orientation of the 5u5 and 1u1 capcitors in the schematic? Can I use 4.7uF instead of 5.5uF and 1.0uF instead of 1.1uF?
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Old 17th May 2013, 06:23 AM   #15
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The TL074 or TL084 would be fine.

The caps are one (1) and five (5) uF (Microfarad). The 10K resistor sets the input impedance of the tone stage. That's pretty low. You could use a 470K here and a 0.47uF poly type cap. The 1uF is just a coupling cap and can be larger if needed. A 10uF cap would work well.

If you use electroylitics for those two then the polarity shouldn't matter because there is no DC voltage present across them.
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Old 17th May 2013, 11:05 AM   #16
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Thanks. I made the circuit today with an LF353 op amp. The 5.5uF got replaced by an electolytic 4.7uF. The 10K resistor is unchanged. I changed the 11K and 3.6K resistors with 10K and 3.9K, respectively, and the 0.05uF cap to 0.56 due to unavailability.

I hooked it up to my TDA2009A amp. As far as I can tell, the sound quality is the same. There is one problem though. I get a mains hum with the tone control connected to the main amp. I grounding the case of the potentiometers and the hum was reduced but it is still quite noticeable.

Any way to eliminate or at least reduce the mains hum?
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Old 17th May 2013, 11:22 AM   #17
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Someones having fun.

0.56uf for a 0.05uf cap won't do as its a critical component in determining the frequency response of that section of the control. 0.05 can be replaced by 0.047uf (that's 47nano farad) or you can use five 0.01uf (10 nano farad) caps in parallel.

Any hum will probably be down to the wiring and grounding. That also depends on whether this is a separate unit with its own PSU or whether you have it built into the main amp. It should be possible to get it silent though. So that's not an easy one to answer without seeing exactly what you have done.
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Old 17th May 2013, 11:32 AM   #18
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Whoops. Typo there. The 0.05uF got replaced by 0.056uF not .56uF.

Both preamp and main amp are wired to the same power supply. The wiring I used is just plain awg 22 with single layer of insulation.

I will try to take pics but its a real mess. I'll be posting in a few.
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Old 17th May 2013, 11:35 AM   #19
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OK
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Old 17th May 2013, 11:52 AM   #20
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I'll just update the software images first. It has no labels, sorry. Numbers on the preamp indicate the corresponding pot pins.


Click the image to open in full size.

Damn. The preamp and main amp got switched.
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