In this case, no, accuracy does not matter. =A0These are DC blocking caps t= o prevent the DC bias from leaking back into the signal source. =A0As long = as they are at least 10nF, any film caps will work. =A0The reason I am reco= mmending film is because they are guaranteed nonpolar, they don't dry out l= ike electrolytics, and they don't drift, piezo, or have noise like ceramics= .. =A0Film is always the best when you are dealing with audio. Cheers, Robert ---------------------------------------- > Date: Wed, 18 Mar 2015 19:14:15 +1300 > Subject: Re: [EE] simple opamp amplifier problems > From: rocifier@gmail.com > To: piclist@mit.edu > > Hi Robert, why does it have to be 10nF specifically? What do those > caps do? I have a professional audio mixer circuit here that uses > in-line 47uF polarized caps at the signal inputs. Does the accuracy > matter? > > Cheers > Ryan > > On 18 March 2015 at 18:42, Robert Dvoracek wrote: >> 10nF, use film caps. >> I would have also connected the feedback resistor after the totem pole i= nstead of before it to correct for some of the distortion in the final stag= e. >> >> Cheers, >> Robert >> >> ---------------------------------------- >>> From: bobblick@ftml.net >>> To: piclist@mit.edu >>> Subject: Re: [EE] simple opamp amplifier problems >>> Date: Tue, 17 Mar 2015 22:01:18 -0700 >>> >>> Actually I take back that thing about the third diode, just the pulldow= n >>> resistor should fix things. >>> >>> Bob >>> >>> On Tue, Mar 17, 2015, at 09:46 PM, Bob Blick wrote: >>>> Hi Ryan, >>>> >>>> The LM358 will require a pulldown resistor on its output, otherwise it >>>> runs class B and will distort real bad. >>>> >>>> Also you will need to get the bases of your transistors a little furth= er >>>> than 2 diodes apart. Put a third diode in there, and it should sound >>>> great but use too much current. Make that third diode a Schottky and y= ou >>>> should be golden. >>>> >>>> Cheerful regards, Bob >>>> >>>> On Tue, Mar 17, 2015, at 09:36 PM, Ryan O'Connor wrote: >>>>> Hi guys, I've bread-boarded the following circuit, but its not playin= g >>>>> audio. I get only DC current at the base of the 2N4401. I've had it >>>>> playing audio briefly while screwing around. For example if I remove >>>>> the 0.01uF cap from the non-inverting input of the left-most opamp an= d >>>>> plug it back in, I hear a distorted version of the song I am playing >>>>> as input for about half a second (actually the cap value is polar >>>>> 47uF). Then silence, DC voltage. Could it be because I am using >>>>> electrolytics for these two caps? I can't find any "103" bipolar lyin= g >>>>> around, or even close to it. I tried a 0.47uF bipolar but I only hear >>>>> about 0.05 seconds of audio when I plug/unplug that one. Have double >>>>> checked all the wiring twice. >>>>> >>>>> Circuit below: >>>>> >>>>> http://www.techlib.com/electronics/graphics/audioa14.gif >>>>> >>>>> Cheers, >>>>> Ryan >>> >>> -- >>> http://www.fastmail.com - Choose from over 50 domains or use your own >>> >>> -- >>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive >>> View/change your membership options at >>> http://mailman.mit.edu/mailman/listinfo/piclist >> >> -- >> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive >> View/change your membership options at >> http://mailman.mit.edu/mailman/listinfo/piclist > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist =20 --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .