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Started by ENGR BUGO aka DimebuGG, October 12, 2011, 12:37:45 PM
Quote from: J M Fahey on May 01, 2012, 12:03:02 AMNo problem.I have posted it earlier myself, but don't remember the link, so repost.EDIT: I saw the project you found.Don't like it very much: it uses the obsolete single supply configuration, has no short circuit protection, the feedbark network is unnecessarily complex (and probably wrong) and it's not easy to modify it into a mixed feedback system.Study this:http://www.diyaudiotr.com/islecler/tammetin.php?metinid=6&durum=e#sonyorumIt is *very* crude, simplified to the maximum, but it works and can be built.The PCB is easy to homebuild and works too.And is very easy to modify to mixed feedback.It's in Turkish but google can translate the page easily.http://translate.google.com/translate?sl=tr&tl=es&js=n&prev=_t&hl=en&ie=UTF-8&layout=2&eotf=1&u=http%3A%2F%2Fwww.diyaudiotr.com%2Fislecler%2Ftammetin.php%3Fmetinid%3D6%26durum%3De%23sonyorumSome small corrections:1) forget the 150W they claim and even 100W, it can provide honest and loud 70W into an 8 ohm speaker.2) the supply voltage suggested is not too safe.I suggest (by experience) not passing +/- 40V rails, which demand a transformer of no more than 30+30VAC (or 60VCT).3) there is a separate .pdf with the ready to print PCB. www.diyaudiotr.com/resim/proje/kapibara/pcb.pdfI recommend the iron on laser thermal transfer process, but it requires some experience.Meaning, make 3 or 4 PCBs before trying this one.I suggest not building this amplifier now, but it's good to know what you are getting into.Start by making an LM386 amp.Build and enjoy it. It is fun.Later, build , say, some 15 to 30W with a TDA2003, TDA2030 or even TDA2050.Build and enjoy.Later, an LM3886 project. (50W)Loud enough to play anywhere.Go step by step, enjoy and learn along the way.I see you live in Peru. Check what amplifier kits you can buy in an Electronics Shop.
Quote from: J M Fahey on September 15, 2012, 12:36:59 AMBasically right, but please repost the schematic labelling every component , such as R1/R2 ....C1/C2.... Q1... etc.Also label input/output and +/- on the speaker.I *hate* explaining "the resistor to the left of the transistor which is upside down between ..... "Also the added feedback resistor goes to the lower end of the speaker, not straight to ground.Good luck.
Quote from: Loudthud on September 18, 2012, 01:04:23 PMBreak the connection of C1 to ground and connect it to the top of R12. If you want to experiment, connect a 25 ohm wirewound pot (1 or 2W) across R12 and connect C1 to the wiper. That way you can adjust between voltage mode and mixed mode feedback. There will be some gain change as you adjust the pot. R12 can be 0.22 5W (or higher). JM basically gave you the answer in post #21.
Quote from: Loudthud on September 20, 2012, 11:47:01 AMC32 is a fairly high value limiting the high frequency open loop gain of the Randall amp.