The input and feedback loop traces arerouted over the signal ground plane. Please double check the information below, as I do not have alot of knowledge about electronics yet (I am a newbie). Second is there any need for preamp as my audio source would be a laptop or a smatphone. As C13 is used to stabilize the amplifier I would just like confirmation that the parts list and silkscreen are correct. Its well below the lowest AM broadcast frequency (535 kHz), so radio frequencies and most electromagnetic interference should be filtered out. The gain of the LM3886 can be set by changing the values ofresistors Ri and Rf1. Okay, thank you. What can i do now? Great project; thank you for sharing. Is anybody able to make an audio input switch for this amp? Then factor in your transformers regulation and the variation in your mains voltage. I put some changes in Powe supply So depending on the capacitor supplier used, the design may have larger bulk capacitance, divided into multiple smaller caps in parallel as needed that can satisfy the RMS ripple requirement. A lack of attention to design details such as the above can call into question the feasibility/operability of an entire design. Whoa !!! The unit looks very professional and the performance is fantastic.
Ill give your recommendation a try once my parts arrive. I think many of the posters are from countries where English is not the primary language. Use a star ground design (look it up) since grounding to your chassis may or may not work correctly (painted surfaces sometimes dont conduct or connect correctly for a universal case ground. Or have I misunderstood the calculations? Thanks. From the left But I think three wire transformer output should also do just fine. If a high current fault occurs, the fault current can flow through the diode bridge to earth. I could send them to you for the amount of the postage. You attached the chassis earth to the bottom plate of the case, but how are the top, front, sides and rear of the cases earthed? I have a transformer that feeds 22V at 7A..
A last resort is the use of a GLB (ground loop breaker) circuit as part of your grounding scheme. Check out SunFounder, the number one source for Raspberry Pi and Arduino starter kits and many more robotics and DIY electronics modules and accessories. thanks Commonly available through Moser and DigiKey. Crossed over at 1000 and 7000, thats about it If this becomes a problem, you can installa 1 nF capacitor betweeneach input terminal ground andthe chassis to filter it. You are supposed to place R4 (20 Ohm) between pins 3 and 9 directly ON the chip. Now lets find a minimum VA rating for the transformer that will power youramplifier. Thnx in advance, Very nice tutorial. You can click on the image aboveto edit the PCB layout, change the component footprints, and order PCBs. Someone can correct me if Im wrong here. I have about $180 into the completed unit with enclosure. Im beginning to not trust this beast. Then it will ask you if you want to check the file before generating the Gerberssay YES. I have a cd player and phono pre-amp with no volume control. If I may offer my observations, which are purely subjective though based and no doubt influenced by research. Still no sound , IC is still heating. Thank you for your excellent work! These wires should be thick,as short as possible, and twisted together tightly. They are easily bent and the backs of the diodes will short if they touch together. You seem to know what you are doing as well as having a lot of experience. With two two separate power supply units, all grounds be channel specific on the PCBs and the two ground-loop protection circuits (one from each power supply unit PCB) connected together to the chassis? Did you forget it?
Ifyoure building a stereo amplifier, you want Ri and Rf1to have closeresistance tolerances. Second is to place fuse at the output end of the lytics. Inductance and resistanceinhibit the flow of current, whichincreases with longer wires and traces. What happens to long waveband signals and very high power VLF signals like from time signal transmitters? Therefore, smaller values ofRsnmake the Zobel network more efficient at filtering radio frequencies, but it also increases the cutoff frequency, which in turn reduces its effectiveness. But it wasnt so from the start either I wasnt used to the sound or the amp needs some time to burn in (which many people say is a myth). 
It also prevents radio frequenciespicked up by the speaker wires from getting back into the amplifiers inverting input through the feedback loop. Henning, if you read the SET THE LOW FREQUENCY CUTOFF AT THE FEEDBACK LOOP section the author does state that a non-polar polypropylene could be used but the size of such a cap would be huge so an electrolytic cap is substituted. Thevalues of Rin and Rbare chosenso together they equal the value of Rf1. . The impedance info on the speakers themselves as well as Miccas website states Impedance: 4-8 Ohms. Thanks, I did the directly onto the chip procedure.. it took patience. Since the power supply is relatively far away from the chip, inductance and resistanceare a problem. Tambis the ambient temperature inC that the amplifier will be operated at. Can i use a center tapped torroid fo this amp project? Metal enclosures are the best type because they shield the amplifier from interference caused byfluorescent lights, radios,and cell phones. Its more complex and expensive to build (it uses SMDs that either you can buy already attached or you can solder them on yourself) but you will be just astounded with the music coming out of your speakers. This will make the currentat the non-inverting input equal tothe currentat the inverting input. This should about cover most of what youll need to build an excellent sounding Hi-Fi amplifier with the LM3886. Surprisingly, while searching for Negative Feedback of amps, I came here. Please have a look at the pics. This isespecially important for the power supply decoupling capacitors, feedback loop, input circuitry, and Zobel network. After a lot ofsearching, I found a company called Hi-Fi 2000that manufactures some reallynice metalenclosures. for your computer you can simply download some freeware controlssoftware to alter the input signal of your amplier. Low current grounds are the ground feeds to the input circuitry and feedback loop. Withsmaller values of Ci, the bass will be softer and have less punch, butwith larger values of Ci, the bass will be tighter and havemore impact. Cc before or after Cin? The key to a good grounding layout is to keeplow current grounds separate fromhigh current grounds. This candistort the input signal, so its best to keep them far apart or route them at90 angles. I have quite a bit of leftover CPU coolers and i have an idea to use those for building an amp based on 3886. When you convert the transformers AC voltage to DC on the power supply, the voltage actually increases to about 25V due to the bridge rectifier. I have order the pcbs but no the components. Although its a bit more work, I prefer the T version for the 0.8 C/W increase over the other. That wayCcstill filtersradio frequencies, but italso acts as a low pass filter that willset the upper limit of the amplifiers bandwidth. If the Fc of this filter ishigher than the input filter, the amplifier will pass low frequencies to the feedback loop that itcant handle. In this tutorial, Ill go step by step throughthe amplifier design process as I builda 40 Watt stereo amplifier usingthe LM3886. So the silkscreen is correct. Years ago I made a very simple gainclone, But I dont understand why C4 (470F) is a polarised cap. Probably 1 volt too? Thank you Pete for addressing my brain damaged question! Which voltage level gives this output? Ive inserted a nylon screw and two nuts per pair of diodes so they cant touch while youre testing the system. Thanks in advance. In that cas, it should be 2/pi can anybody help me with that%.
Fusing both AC line input and power rails are the best but more work and expense. I trimmedthe leads of the feedback resistor (Rf1) and soldered it directly to pins 9 and 3 to keep the loop area as small as possible: Inductance inhibits the flow of current and creates resonance witha capacitor thats in series. At the time of faulty connection both the fuse were blown up. How would this alter component values? Rectifier Type Switching It just does not get better than that! Thank you very much this blog is very helpful. It will then give you a download box for the gerber file. Agood gain setting thats not too high to cause distortion, but not too low to give you a good range of volume is around 27 to 30 db. Doesnt mean you cant try one and see what it sounds like. I changed the selection of the decoupling capacitors (I posted it somewhere in the string of responses) and I think the amp sounds much better. It came out to just under $35 per side for the components, but you have to consider the costs for the boards and power supply. I tested it all on a bench top so there was no common metal case joining the components. Second, Im trying to design the amp to go with a pair of Bose Interaudio 4000 speakers, which have a rating of 10-100W and 4-8 ohms. I cant thank you enough. So with Rf1at 20 k, thevalue of Rinthat balances the input bias currentfor my amplifier is: Youll probably be able to find a 19 k resistor available with the type of resistors youre using, but 20 k is the closest value I could find with Vishay-Dale PTF resistors so Ill have to settle withthat. wooden iphone passive speaker speakers amplifier projects wood cardboard technology plans amp ks3 woodworking tech phone project holder simple madera This is far far better than I wanted to publish, or would say THE BEST. iphone dock wood speakers amplifier He sells them either blank or with the SMDs (surface mounted devices) already soldered in place (for an extra fee of course). A second high pass filter exists in the feedback loop with Ri and Ci: The cutoff frequencyof this filter should be 3 to 5 times lower than the Fc of the Cin\ Rinhigh pass filter at the input. A request .Could you also consider doing a solid state discrete power amp with dual dc power supply. 1996-2022, Amazon.com, Inc. or its affiliates. In the rest everything is equal to the circuit. Why a 63V cap (versus a 50V like everywhere else) is needed in the Mute Circuit I cant answer. The zener Diode i used is 9.1V zener diode. On each amp board, on the signal input side , the SIG_GND connects to any of the SIG GND on the PS output side of the PS. It is hard to resist from building this amp:-). my other amp on same spaker calble pre amp is quit, Hey i would like to buy this PCB but dont know how to. A complete schematic, as well as components values for the power supply will be greatly appreciated, Thank you so much in advance. Your efforts really appreciated.thanks a lot, Hi All, Thank you.
These should be somewhere between 10 F and 220 F. Since Cinis directly in the path of the audio input signal, thetype of capacitor used will have an influence on sound quality. Dario is currently up to build 1.72 I believe. Peak Non-Repetitive Forward Surge Current 100A If you dont want do all of the calculations we didabove, you can use the values I used. Just as long as all the capacitors are 50V, or greater, youll be fine with that tranny (25Vx1.4=35VAC after rectifiers). any ideas what kind of cable gauge to use for the internal signal wiring ? Drop me a private email (randommailboris@gmail.com) and Ill try to send you understandable instructions. i burned the 2 caps in 2 different times, the 22uF first, then i made a new board and the 1000uF blew. It should read <10mV DC. Copyright 1996-2022 IndiaMART InterMESH Ltd. All rights reserved. To tell you the honest truth I cant hear a big difference between the 18+18 and the 28+28 and the larger toroidals use doesnt improve the bass response. Just a heads up from me regarding the build.
Finally, youll need to know yourinput voltage. If its not there, then send us a message through our comment form and well make sure you get it: https://www.circuitbasics.com/contact-us/. First though, youll need to knowyourLM3886smaximum power dissipation (Pdmax), and the thermal resistancesin the path heat takes from the chip die to the ambient air. Capacitors with lower equivalent series resistance(ESR) and lowerequivalent series inductance (ESL)are the best types to use here. Note that the The Overture App note has a few errors (not necessarily related to the design presented here). One could also build a slightly more advanced controller, e.g., a Pass B1 passive preamp) that build slightly on just a plain, old potentiometer. Is my 3886 damaged internally ?? The heat sink will dissipate the peakpower produced by the amplifier (Pdmax) if its thermal resistance (sa) is less than or equal to the value calculated with this formula: The LM3886 is manufacturedin two different packages, the LM3886T and the LM3886TF. However when the input is not connected to my phone, there is a loud irritating humming noise at the output(speaker). Audio input cables running from the source to the amplifier chassis can pick up interference. Talk to you next time. everything were very well explained. This step is important because if the transformers voltage is too low, the output power of the amplifier will be less than what you expected. The capacitance will probably be too high to use polypropylene, so youll likely have to use an electrolytic. Thanks. and one from amp to receiver. With an 18 V transformer, I would get amaximum supply voltage of: 29.6 V is pretty close to the 30.2 V maximum supply voltage needed by my amplifier, but letscalculate exactly how much output power Idget with this transformer. Ill make the assumption its not a center-tapped transformer.
This is the voltage theamplifierneeds from the power supply to get thedesired output power. I would really appreciate any help before I take every component one after the other. The DC voltagewill be higher after the bridge rectifier diodes on yourpower supply convert the AC voltage to DC. WEON CSA 145 X - Natural Sound Processing 2.0 Channel Hybrid Amplifier System with Bluetooth | USB | FM | Aux & Mic Support, Pluto Accessories HDMI Splitter 1 x 4, 1 Input 4 Output HDMI Amplifier Switcher Box Hub Support 1080p, optik vision gold Hybrid Amplifier 860 MHz CATV, Car & Vehicle Electronics Installation Equipment. This is _really_ a fantastic guide for a newbie like myself.
You can really feel it. What to expect?
I was wondering the same thing. I can hear details in songs that I never knew were there. I dont listen at high volume levels to be honest. The assembled panels of the enclosure are not electrically connected, but they should be to have a proper earthing of the chassis. Peak Reverse Repetitive Voltage 600V Cheers. At high frequencies, the impedance of Csn is very low, so high frequency current is shorted to ground. Like wise you can remove all electrolytics and test them as well (if you have a meter to do so). Pete, yes this gainclone was a great project to build and the detailed theory was very instructive. Then I rearranged the gain formula to solve for Rf1with a gain of 22.4 Vo/Vi: Im going to use Vishay-Dale PTF series metal film resistorsthroughout my amplifier, but the closest value I couldfind was20k.
Im still fumbling when trying my hand at using the EasyEDA software.
Quick question, Im making these amplifiers to work in my car, so I will be using a 12V-30V DC transformer to power it. John- in regards to the case, the T version is non isolated meaning the back of the case is clean metal connected directly to the -V supply which requires electrically insulating it from the heat sink. 2. Csnshould havelow ESR and low ESL, with a voltage rating greater than the rail to rail swing of output voltage. The means to do so have been provided. Set the Low Frequency Cutoff at the Feedback Loop the diagram under that title I think needs the 20k resistor between output and neg input. Thanks for the nice tutorial and beautiful built. Thank you in advance. The sound is now a little fuller at the bottom end than it was before with the proviso that I mostly listen to classical music and some better recordings of Folk & Blues.