Funnily enough I connected one of the caps from inverting input on left-hand op-amp to GND by mistake, and I hear the audio with a high-pitched squeal mixed in lol. On 18 March 2015 at 20:07, Ryan O'Connor wrote: > 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 = to prevent the DC bias from leaking back into the signal source. As long a= s they are at least 10nF, any film caps will work. The reason I am recomme= nding 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. = Film 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 st= age. >>>> >>>> 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 pulld= own >>>>> 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 fur= ther >>>>>> 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 play= ing >>>>>>> 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 remov= e >>>>>>> the 0.01uF cap from the non-inverting input of the left-most opamp = and >>>>>>> plug it back in, I hear a distorted version of the song I am playin= g >>>>>>> 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 ly= ing >>>>>>> around, or even close to it. I tried a 0.47uF bipolar but I only he= ar >>>>>>> about 0.05 seconds of audio when I plug/unplug that one. Have doubl= e >>>>>>> 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 .