Well I suspect this amp is far more watts than I thought. My speaker is 15 watts, but I think its my speaker that's distorting. I unplugged one of the opamps, and I get a fairly crisp signal coming through at room-filling volume. When the other opamp is plugged in, The speaker is going pretty nuts and moving a lot. As mentioned before the volume is very loud and clipped. On 18 March 2015 at 20:50, Ryan O'Connor wrote: > Which resistors are responsible for the gain? Is it the 2x 3.3k, or > just the first one? Cheers. > > Attached diagram again. > > On 18 March 2015 at 20:46, James Burkart wrote= : >> 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 secon= ds >>> >> 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 d= ry >>> 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 accurac= y >>> >>>> 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 littl= e >>> 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 Schottk= y >>> 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 h= ad >>> 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 po= lar >>> >>>>>>>> 47uF). Then silence, DC voltage. Could it be because I am usin= g >>> >>>>>>>> electrolytics for these two caps? I can't find any "103" bipol= ar >>> lying >>> >>>>>>>> around, or even close to it. I tried a 0.47uF bipolar but I on= ly >>> 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 you= r >>> 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 >>> >> -- >> 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 .