polarized cap in audio circuit?
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From: panfilero on 8 Mar 2010 21:04 is it ok to use an electrolytic polarized cap to block dc signals in an audio circuit? Basically I have this kit http://www.electronickits.com/kit/complete/meas/ck102.pdf and I wanted to remove the DC offset at the outputs before sending the signal to an audio amplifier thank you
From: krw on 8 Mar 2010 21:09 On Mon, 8 Mar 2010 18:04:38 -0800 (PST), panfilero <panfilero(a)gmail.com> wrote: >is it ok to use an electrolytic polarized cap to block dc signals in >an audio circuit? Sure. Overrate the cap by at least 50% (16V in this case). >Basically I have this kit > >http://www.electronickits.com/kit/complete/meas/ck102.pdf > >and I wanted to remove the DC offset at the outputs before sending the >signal to an audio amplifier >thank you
From: pimpom on 9 Mar 2010 04:35 panfilero wrote: > is it ok to use an electrolytic polarized cap to block dc > signals in > an audio circuit? > > Basically I have this kit > > http://www.electronickits.com/kit/complete/meas/ck102.pdf > > and I wanted to remove the DC offset at the outputs before > sending the > signal to an audio amplifier > > thank you Electrolytics are fine except where high fidelity and very low leakages are important. Just make sure you observe the correct polarity and that the capacitance is adequate for the lowest frequency yuo want to use. I suggest you put a resistor from the output side of the cap to ground. Thius will prevent getting a loud 'thump' if you connect the signal generator to the amp after both units are powered on.
From: panfilero on 9 Mar 2010 11:06 On Mar 9, 3:35 am, "pimpom" <pim...(a)invalid.invalid> wrote: > panfilero wrote: > > is it ok to use an electrolytic polarized cap to block dc > > signals in > > an audio circuit? > > > Basically I have this kit > > >http://www.electronickits.com/kit/complete/meas/ck102.pdf > > > and I wanted to remove the DC offset at the outputs before > > sending the > > signal to an audio amplifier > > > thank you > > Electrolytics are fine except where high fidelity and very low > leakages are important. > > Just make sure you observe the correct polarity and that the > capacitance is adequate for the lowest frequency yuo want to use. > I suggest you put a resistor from the output side of the cap to > ground. Thius will prevent getting a loud 'thump' if you connect > the signal generator to the amp after both units are powered on. Thanks! What would the correct polarity be in my case? Does the output get the cathode or the anode? I tried putting a resistor on the output to ground but it attenuates my low frequencies... am I correct in thinking that putting a resistor to ground on the ouotput would make a high pass filter and is therefore killing my lower frequencies?
From: pimpom on 9 Mar 2010 12:19
panfilero wrote: > On Mar 9, 3:35 am, "pimpom" <pim...(a)invalid.invalid> wrote: >> panfilero wrote: >>> is it ok to use an electrolytic polarized cap to block dc >>> signals in >>> an audio circuit? >> >>> Basically I have this kit >> >>> http://www.electronickits.com/kit/complete/meas/ck102.pdf >> >>> and I wanted to remove the DC offset at the outputs before >>> sending the >>> signal to an audio amplifier >> >>> thank you >> >> Electrolytics are fine except where high fidelity and very low >> leakages are important. >> >> Just make sure you observe the correct polarity and that the >> capacitance is adequate for the lowest frequency yuo want to >> use. >> I suggest you put a resistor from the output side of the cap >> to >> ground. Thius will prevent getting a loud 'thump' if you >> connect >> the signal generator to the amp after both units are powered >> on. > > Thanks! > > What would the correct polarity be in my case? Does the output > get > the cathode or the anode? The anode of the capacitor should go to the output *from* the kit, e.g. pin 7 of the opamp if you're going to use the sine output. The cathode should go to the audio amplifier. The "anti-thump" resistor should have one end connected to the cap's cathode, and the other end to ground. > > I tried putting a resistor on the output to ground but it > attenuates > my low frequencies... am I correct in thinking that putting a > resistor > to ground on the ouotput would make a high pass filter and is > therefore killing my lower frequencies? Yes and no. The combination of output cap and resistor to ground does make a high-pass filter. But if you choose a proper combination of capacitance and resistance, the roll-off frequency (the frequency where lower frequencies start to be noticeably attenuated) can be placed well below the lowest frequency you want to use. For example, if we choose C = 4.7uF and R = 10k, the roll-off freq is about 3.4Hz. The high-pass action will have only a small attenuating effect at 5Hz, and negligible effect at higher frequencies. Note, however, that the 10k resistor is in parallel with the input impedance of the amplifier. This lowers the effective resistance and raises the roll-off frequency. If the amp has a high input resistance compared to 10k, then the effect will be minor. If the input impedance is comparable to or lower than 10k, then it will have a significant effect on the roll-off frequency. |