Your input is too hot, and/or your gain is too high. On Mar 18, 2015 2:42 AM, "Ryan O'Connor" wrote: > Aha! That actually made me wonder if maybe one half of the opamp is > dead, and I realised I was using a second-hand one. Replaced it with a > new one and it runs continuous now. This thing is loud! > > Unfortunately the distortion is super high. It sounds more clipped > than a highly distorted guitar. could it be some of the resistors need > tweaking now? > > On 18 March 2015 at 20:13, Ryan O'Connor wrote: > > 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 as they are at least 10nF, any film caps will work. The reason I am > recommending 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 stage. > >>>>> > >>>>> 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 > pulldown > >>>>>> 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 > further > >>>>>>> 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 > playing > >>>>>>>> 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 and > >>>>>>>> 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 pola= r > >>>>>>>> 47uF). Then silence, DC voltage. Could it be because I am using > >>>>>>>> electrolytics for these two caps? I can't find any "103" bipolar > lying > >>>>>>>> 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 > >>> > >>> -- > >>> 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 .