Can I use Cin and Cc in The between of Rin and Rc?. However I am almost a new graduate of Electrical Engineer and not sure if I can handle the processes. Arnaud, one advantage in using the 18+18 is you can use higher rated uF Caps (using 35V instead of 50V) in both the PS and the amp w/o having to worry about their diameter limits fitting on the boards. Hi! The key to a good grounding layout is to keeplow current grounds separate fromhigh current grounds. Crossed over at 1000 and 7000, thats about it Pete Zafian on October 27, 2020 at 1:13 pm At least to me, but Ive been listening only to Yamahas for the past 10 plus years. Would it be possible to provide the PS schematic or the gerber files for the PCB board? Ive got the PCB but when I started to put the components , I didnt find the holes for R4. Thanks for replying and giving me at least the first hints on where to start troubleshooting. I was going to purchase the same transformer (brand) listed in the parts list with the exception of using the 25v version rather than 18v. At high frequencies, the impedance of Csn is very low, so high frequency current is shorted to ground. Please be kind :-). A new pop-up box appears to request the info. In order to bring this down to a more reasonable level, I decided on using 4.7 for Rsnand 220 nF for Csn, which lowers the Fcdown to 154 kHz: 154 kHz is wellabove the 20 kHz limit of human hearing, andwell below any radio frequencies the speaker wires might pick up. Meaning, small caps closest to LM3886. 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. Did you mean X7R ceramic capacitors. Hello, I am interested in the Fremen Edition Evolution A amp as well but cant seem to find a link to where you can order some boards. It will then give you a download box for the gerber file. Unfortunately, it alsoincreases the chance foroscillation. Ina high pass filter, frequencies belowthe cutoff frequency will be attenuated (muted). Simone: I tested my amp boards using the chipamp PS and everything works fine. I did the directly onto the chip procedure.. it took patience. Yes, you are not Scott, but you do share something in commonkindness! your job is truly inspiring me so i have to do it. Weakest link: Supply large bulk storage caps. The feedback loop should be kept as short as possible to reduce the loop area. Ed. Due to the length of this post, I decided not to cover the power supply in detail, but I may do so in the future. Should I use 4 Ohms as my base for the power calculations? An easyway to minimize the loop area is to useground planes on the bottom layer of the PCB, which Ive done in this layout. Also sent to earth ground are the SIG_GND from each board, and all the common (-) lines from the RCA inputs & speaker outputs. Just in case its not clearly stated in the history flow above, my changes to the decoupling caps are 470uF/50V nichicon KAs, 10uF/100V Silmic IIs (mounted on underside of board) and Vishay 100nF/100V 1837MKPs (mounted on top with a bit of creative angling). My design is intended to be used with a bluetooth module, having the option to connect any bluetooth compatible device, has a radio receiver, an option for usb/SD card insertion as well as an AUX input. Can i use a center tapped torroid fo this amp project? Simply adding some controls could decrease/alter the sound quality output, or not. You explained it very well to me! In that configuration, Ccfilters radio frequency and electromagnetic interference picked up by the input wires. If you dont want do all of the calculations we didabove, you can use the values I used. Why a 63V cap (versus a 50V like everywhere else) is needed in the Mute Circuit I cant answer. Tony, I think the author was using 1.1 as a factor in the calculation implying the mains voltage (=1) and adding 10% to it (10% of 1 is 0.1) hence the factor is 100% + 10% = 1.1. Cheers. The LM3886 has one negative power supply pin (pin 4) and two positive power supply pins (pins 1 and 5). However, as I mentioned before, the hum only exists when the input is left open (without any connection to it). It also prevents radio frequencies picked up by the speaker wires from getting back into the amplifiers inverting input via the feedback loop. Dave, I am not sure but you can try this Forum: https://www.diyaudio.com/forums/chip-amps/234032-my_ref-fremen-edition-build-thread-tutorial.html. Lijo: you cant use a center tapped transformer for the PS referenced in this project because it has two diode bridges which required dual secondaries on the toroidal transformer (they are both +25AC BTW). the negative leads tied together which is what Im doing for my spin on this excellent reference design. In this case whats the best way to handle grounds? Lets start by figuring out how much voltage and power your amplifier willneed from the power supply. :( when I connect a power supply (tried 2 different ones), voltage slowly rises on both the positive and the negative rail on all power supplies on both channels with no signal through the speakers. However If amp is run at near full load (not likely) heating effects of the transformer and bulk storage caps should be cooled as well. To find the maximum supply voltage, takethe peak output voltageand add the voltage drop (Vod) of the LM3886 (4 V). 1) I am just starting to get into DIY audio and while this amp seems like a great quality amp and the article is very in depth I am wondering if this is too complicated for a first amp build? You can do this in two different ways- Build everything into the original amp housing or build the additional controls into a separate enclosure. I tried jumping diode, the voltages were correct 35V at both the rails. Second is to place fuse at the output end of the lytics. The ground protection circuit can connect to the chassis at the bolt wherethe mains earth wire is connected to the chassis, or at a separate location. This is amazing. Grey/black gives 0 in any combination. This is too close should there be PS fluctuations due to various factors such as transformer load ratings (% regulation) and/or higher line voltage (one should not depend on PS sag for meeting this voltage requirement). Im wondering where we can add bass control and volume control in this. I also really like how you supplied the calculations for determining the size of the components. Unfortunately itcan be hard to find a chassis that fits everything and looks nice too. A470F capacitor will set the Fc of myfeedback loop filter to 4.9 times lower than the Fc of myinput filter. The cutofffrequency (Fc) of thisfilter can be found with the equation: The equationcan be rearranged to find avalue ofCinfor a particular Fc: Youfound thevalue for Rinwhen youbalanced the input bias currents, so all youneed now is to choose a cutoff frequency. A complete schematic, as well as components values for the power supply will be greatly appreciated, Thank you so much in advance. The production costs arent very high but the shipping costs are, unless you have a more local production facility. Otherwise, the ground loop protection circuit will be bypassed entirely by the input/output ground wires that connect to the main system ground. Truly fantastic stuff you got here! Please do refer our website: There are numerous designs for these circuits on the web. The power supply wires, speaker output wires, transformer, rectifier diodes, and AC mains wiresare a major source of magnetic fields. I wasnt sure if the volume potentiometer should be in the signals input path or the amps output (does it matter?). You can check voltages directly at the pins on LM3886 itself (look to its data sheet for correct pins ). I have order the pcbs but no the components. Hi, I really enjoyed reading this ! Yes, its just made by a different manufacturer so the specs will be slightly different. But I was astounded. Could you explain briefly, the advantages/disadvantages of the T versus TF versions of the LM3886? 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. From my understanding the 50pf should be C13 and the 680pf the C2?? This is what you posted to me just before with how I suggested to hook up the tranny to the PS input. Am in the process of reviewing all the details in this guide to get started shortly with my build. Audio input cables running from the source to the amplifier chassis can pick up interference. I started with a 3 amp Fast Blo and it immediately blew on the first startup due to inrush currents of the 40,000 lytics. Thanks, Measure the mV output at the speaker out terminals. In this arrangement, the heat sinks provide some shielding from the Thiele networks and the AC wires leading to the transformer: GROUND LOOP PROTECTION CIRCUITS MAY BE ILLEGAL IN SOME AREAS. Yuval, I built them amp just as described and Im using it with my 8 ohm speakers. Earth ground the 0 terminal of your switching PS as well. The Fc with a4.7 F capacitor would be: An Fc of 1.69 Hz is pretty close to my desired 1.5 Hz, so a 4.7F capacitor should be good. Placingtheir PCB terminalson opposite sides of the boardwill make it easier to keep them separate when you route the traces. Capacitors with lower equivalent series resistance(ESR) and lowerequivalent series inductance (ESL)are the best types to use here. I would like to know how much the project costs for a stereo system including the power supply/transformer and where can i order these modules/accessories? Only low currents flow through the input wires and signal ground wires, so they dont need to be heavy gauge. And be sure to like, share, and subscribe if you found this helpful! The capacitance will probably be too high to use polypropylene, so youll likely have to use an electrolytic. Great detail and explanations of the individual aspects of the circuit. Lets see what the cutoff frequency would bewith that. EasyEDA is a full suite schematic and PCB design software/manufacturing service thats free to use and offers great prices on custom PCB manufacturing. Try grounding all return (-) leads from inputs and speaker outputs as a start. Thanks in advance, David. There is also a new build-buy forum Regards. The right channel PCB is mounted upside down so that the input side of the board is close to the RCA and 3.5 mm input terminals. I drive 8 ohm speakers so I wanted a bit more horsepower. V+(R)/GND= 25v, V-(R)/GND R= -25v. for signal path coupling should be at least 10% of next capacitor value so; 0.1uf, 1uf, 10uf, the reason for the 3uf polypropylene above, to link the 0.47 teflon to the 30uf polyprop I can use it, no? But I think three wire transformer output should also do just fine. Cc before Rb? my other amp on same spaker calble pre amp is quit, Hey i would like to buy this PCB but dont know how to. If this becomes a problem, you can installa 1 nF capacitor betweeneach input terminal ground andthe chassis to filter it. 2 Since the power per channel would be about 40watts, why should the transformer be rated 300VA? Martin, dont know if Scott will answer but in the beginning of the article there is a yellow box with Bonus starting off the entry. Ive moved the 4.7uf ceramic onto the pins, bottom of board obviously The individual ground networks are connected to the main system ground so thathigher current grounds arecloser to the reservoir capacitors. All the better made (audiophile if youd like; e.g., ALPS, TDKs) are meant for low voltage and attach early on in the signal flow path. This will give youa stronger solder joint andbetter electricalconductivity. The LM3886 is an excellent component and you explained who to do better. This is know as a ground loop, and it can createhum in your amplifiers output. To convert the total power to a transformer VA rating, a general rule of thumb is to multiply itby a factor of 1.5: This is the VArequiredfor each channel, so for a stereo amplifier powered by a single transformer, just double it: Finding a transformer with a VA of 222 will be hard, but youcanround-up to the next closest value and use a 250 VA transformeror larger. I have the same ground for both signal input and output, signal ground, which is then connected at one point with the power ground. The traces for the power supply feeds weremade very wide to minimize the resistance and inductance. Actual voltage is only in the equation as V-transformer and in the results. Alessandro: which make & model number transformer do you have? To un-mute the amplifier, we need to find avalue forRmso that thecurrent allowed to flow out of pin 8 is greater than 0.5 mA. thank you so much for your posting of the parts list as well as the power supply schematic and values!! 3) The +/-42V PS presented in section 7.2.3 is right at the MAX 84V spec specified in the LM3386 datasheet under Absolute Maximum Ratings (Input Signal, not the No Signal 94V). Check out SunFounder, the number one source for Raspberry Pi and Arduino starter kits and many more robotics and DIY electronics modules and accessories. Awesome job, guys. Also, I would try to slide the capacitors away from the heatsink more on the PCB design so that the modules would have a longer life in many years time before breakdowns. If I may offer my observations, which are purely subjective though based and no doubt influenced by research. Have a great day Thank you circuit Basics for the Details in Explanation. Jrgen: the gerber PCB files are referenced all the way at the beginning of the article. Repeating the Fccalculation for a 330 F capacitor gives 0.48 Hz. So I built this gainclone LM3886 chip amp and I learn a lot from doing it. If its a toroidal, it sounds like you wired the secondaries in series (doubling the rated voltage output ) rather than parallel (keeping rated voltage but doubling amperage) and once the 18+18V goes through the diode bridge rectifier circuit it would be 32 x 1.4 = 45V minimally. I read your tutorial and I want to congratulate your excellent didactic and planning work. i didnt change the file just saved it Its not really the same thing as a truly integrated amp (pre-amp + amp) but it works for controlling volume if your signal source doesnt have its own volume control. Ok, that sounds correct. There are plenty of pre-built switching circuits of both types to be found on eBay. I also plan to use a pair of 8 ohm speakers, so if everything works properly with a little more juice in the input I will start with a solution equivalent to yours. Hi Stan, Im not Scott, but all the Gerber files are available right st the beginning of the article and the PS Gerbers can be found in the yellow bonus box. Thediameter of 14 AWG is 1.62814 mm. I build the amp borad are same as sescribed here How would this alter component values? The heatsink is huge. Great Job! After a lot ofsearching, I found a company called Hi-Fi 2000that manufactures some reallynice metalenclosures. I used 14 AWG, but anything larger than18 AWG shouldbe fine. Best tutorial youve ever made and one of the best available online. To convert voltage gain to decibels (db) gain, use this formula: Higher value resistors create more Johnson-Nyquist noise, so its best to find an Rf1/ Riratio that providesyour target gainwith low resistor values. When you connect a powered audio source to your amplifier, magnetic fields fromthe sources transformer and power supply wires can be coupled intothe ground wires of the audio inputcables. The boards are designed by me using the schematics and instructions from this platform. when Im trying to order the PCB for the amplifier and the power supply from EasyEDA its running DRC tests and i get many errors Pad to Copper Area They have ended up 250mm x 170mm and the board is a z shape and the pins etc allow me to swap the various components (polystyrene caps are massive) I have connected some components underneath and supported them on separate boards Electrolytics, ceramics, and tantalum capacitors should be avoided. The lower limit of human hearing is 20 Hz, so theFcshould be well below that to prevent attenuation of bass frequencies. All the best Itusually peaks late at night when people are asleep anddrops in the daytime when more people are awake and drawing current from the power grid. A typical value for Tambis room temperature (25C). Diode Configuration Single I did build my own enclosure with about $25 in material and I cut back on the high priced input coupling capacitors to another high grade film type. Do they have any kind of records on that so it may only require a push of a button on this end? Thanks for the explanation. The PS design is lacking only in that it never incorporated any LED indicators that it was actually On. Thank you! What can i do now? Then measure theoveralldimensions to make sure the enclosure will fit everything. I think I found a misbehaving (though physically intact) decoupling 22uf cap as a suspect and replaced it . They also filter noise and radio frequencyinterference in the power supply. Notify me of follow-up comments by email. Your email address will not be published. I have measured the voltages across the C7, C8, C9, C10, C11, & C12, and the all show the supply voltage of 35V. R5 should be a 10K (or something less than 58K) now, correct? After setting the gain, the next step is to balance the input bias currents by choosing values for Rin and Rb: If the currents at the non-inverting input (pin 9) and the inverting input (pin 10) are different, a voltage will develop between them. Yuval Abadi. Thanks for your reply, Robin! Oh! Dan. Im tweaking some of the filter values for personal; preference and adding a an Arduino Nano to the mix for relay controlled speaker connect / disconnect, basic gain control and thermal monitoring.. Next iteration will have more pre-amp functions including source select, volume and tone control, all done digitally. thanks in advance for any clarification but the 615pf definitely goes to ground. Its costly here in India. Ill explainwhat each part of the circuit does, andshow you how to calculatethe right component values withexamples from the amplifier Im building. Thank you in advance. The Chassis terminal connects to the chassis: Click on the imagetoedit the layout, change component footprints, andorder the PCB. If it were me, I would opt for a separate enclosure which would leave room for multiple input/output connections also. Peak Reverse Recovery Time 60ns No Alessandro, thats not what I said if Im reading your response correctly. You need to start looking at 1000uF values which is coincidentally the same value as the audio grade caps in the local power supply circuit. Cin is in series with the non-invertinginput. 1. I think youve completed the most comprehensive and understandable post on this subject. Make sure you havent got fake chips! thanks. Best, you would need to run a ground wire from source to amp. A bit much perhaps? I assembled the circuit exactly like the one in the guide, with the following changes in the PSU: 24-0-24 250 VA transformer and 4x 10000 uf 50V, having + -32.8 volts dc. The negative supply pinneeds itsown set of decoupling capacitors andthe positive supply pins share a separate set of decoupling capacitors. Repeating the calculations again with a470F capacitor gives an Fc of 0.34 Hz. In addition to the DC blocking function, Cinand the input resistor (Rin) form ahigh pass RC filter that sets the low endof the amplifiers bandwidth at the non-inverting input: This filters cutoff frequency (also known as the-3db point or corner frequency) is the frequency at which the filter starts to work. Your efforts really appreciated.thanks a lot, Hi All, Rf2 and Cfdampen resonance in the feedback loop and enhance stability: Rf1,Rf2, and Cfform a low pass filter in the feedback loop, but as you can see from the formula in the datasheet, calculating the Fc of this filter is quite complicated: The best way to determine values for Rf2 and Cf is with circuit simulation software such as LTSpice. To separatethelow currentgrounds from the high current grounds, we willcreate several ground networks: These grounds should connect only once at a set of terminals called the main system ground. I actually plan to have the whole system installed in a wooden casing, would I still need a ground loop circuit? I still dont understand where the 50VDC is being measured. Hello Pete, If you put one on the amps output its got to be a huge, well insulated one to withstand the power output from the amp (I think these are called L-pads). Hi Pete! Good luck, http://www.learnabout-electronics.org/Downloads/lm1036-Tone%20control%20IC.pdf. Heat sinks with a lower saare better at dissipating heat. When I designed the boards, I placed R4 directly on the boards, Thats what I meant by somewhere else on the board (but now soldered on the LM3886). I am now in the process of building 3 way active speakers, initially with crossovers then with dsps fed through a preamp. Actually you can create a non polarized cap by putting to polarized back to back, i.e. The plastic case of the LM3886TF gives it a higher cs: Tjmaxis the maximum junction temperature, or the temperature at the chips die above which the thermal shutdown circuitry is enabled. 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/. And sorry for asking such an obviously stupid question. I have just finished my build and I noticed right away that I had massive crossover distortion with poor, crackling sound as a result. 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. All other (47) pages of the article and the comments are hidden. The ground loop protection circuitcan be hard wired, but its a little neater to mount the components ona PCB. Please have a look at the pics. Its well below the lowest AM broadcast frequency (535 kHz), so radio frequencies and most electromagnetic interference should be filtered out. I had the same, and i placed the order anyway. Thnx.. Hey, great job! How did you obatin electrical continuity between the front, back, side, top and bottom panels? You would need to use a PS design which utilizes a center-tapped (or a created center tapped transformer from dual secondaries on a toroidal) to create the + GND VDC structure needed to power this amp. What happens to long waveband signals and very high power VLF signals like from time signal transmitters? So you live in the USA David? The highs are clear, but not harsh at all. Amit: I have to go back and look at the schematic, but if youve re-connected the power polar inputs inputs correctly onto to both the amps , and no sound is coming forth, that youve probably damaged the LM3886 chips. Pl. What a painless way of integrating theory, a bit of math, and circuit understanding to a fun project. It explained so much. I really just used the recommendations shown in the Lm3886 datasheet. Though I have no expertise in Physics, was able to understand the technical things in this article. The unit looks very professional and the performance is fantastic. Scott, you have a dedicated follower in me. Since the power supply is relatively far away from the chip, inductance and resistanceare a problem. Ci is still bypassed, because I cant find good quality capacitors around, and I was able to get very little DC at the output. Thedecoupling capacitors alsocompensate for the parasiticinductance and resistanceofthe power supply wires and traces leading to the the chips power pins. They have a huge selection of high quality Raspberry Pi and Arduino parts! I would be gratefull if someone could point me to some schematics or diagrams that could explain the difference..Thnks.