Thanks that was a really helpful answer Robert. I've found two 0.1uF bipolar capacitors and put them in. But I still have the same problem. It plays distorted audio for about 0.01 seconds now when I plug the second cap in. Ryan On 18 March 2015 at 19:25, Robert Dvoracek wrote: > In this case, no, accuracy does not matter. These are DC blocking caps t= o prevent the DC bias from leaking back into the signal source. As long as= they are at least 10nF, any film caps will work. The reason I am recommen= ding film is because they are guaranteed nonpolar, they don't dry out like = electrolytics, and they don't drift, piezo, or have noise like ceramics. F= ilm 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 = instead of before it to correct for some of the distortion in the final sta= ge. >>> >>> 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 pulldo= wn >>>> 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 i= t >>>>> runs class B and will distort real bad. >>>>> >>>>> Also you will need to get the bases of your transistors a little furt= her >>>>> 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 = you >>>>> 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 playi= ng >>>>>> 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 a= nd >>>>>> 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 lyi= ng >>>>>> around, or even close to it. I tried a 0.47uF bipolar but I only hea= r >>>>>> 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 > > -- > 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 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .