I've made gainclone amplifier that uses a LM3886 chip. It's one of the best compact HiFi amplifiers. It is a Class AB-A (conjugate)  amplifier that has a fully symmetrical structure (push-pull), this mean that the sine waves  produced, will produce a + , - output. A 25 volt (+/- Dual Rail), 5 Ampere, toroidal transformer was used to supply electricity for the amp. There's also a PCB Layout provided for the project. I found an old CPU processor attached to a gorgeous heatsink & fan, I recycled both of them and drilled holes for it to be mounted on the LM3886 chips. 

- Maximum Output Power: 68W RMS - 108W Peak
- Frequency Response: 7Hz-25kHz (Filtered ⇒Linkwitz)
- THD: %0.03 at 60W
- SNR: 110dB at 60 W - 92.5dB at 1W
- Output Class: AB-A (Conjugate)
- Auxiliary Features: DC/AC Short circuit protection and thermal protection.
Working Voltage/Power: 12-94 Volts (Dual Rail), 1-10 Amperes
- Audio Features: Input Mute Funtion (100% silent = no input)

Too bad I had a late documentation, that's why I only have a few pictures of the steps and procedures. Due to the late documentation, I had to get images from the original source. Some of the pictures are not mine, there are no claims that the PCB designs are mine nor the diagrams, although there where some modifications made by me for the amp.

What Is A Gainclone?
Back in 1999, relatively unknown manufacturer 47-Labs released the "Gaincard" to rave reviews. It immediately caused controversy because it was based around a $5 power amplifier IC (Integrated Circuit), yet a typical setup would cost you around $3300. A Gainclone in the other hand refers to any DIY amplifier that uses a LM3875/ LM3886 as it's main component. 

What's So Special About It?
The gainclone only uses small amounts of space, it's built with a minimal supply of components, yet giving a great HiFi result. It beats the hell out of those modern HiFi amps, it produces 2x68 watts of power, with a Total Harmonic Distortion of 0.03%THD and built on a 2x3 PCB board!  So why doesn't the audio industry use it? I'm not really sure. All of these sounds "too good to be true", I recommend this project for those who are still starting on their DIY HiFi amp hobby, since it only uses some few components.

What's A Power Amp?
A power amp is a amplifier with no preamp, volume control, tone control, or any auxiliary devices attached to it. It's just pure simplicity.

Coming Soon: DIY HiFi Preamp With Tone Control (Works With The Gainclone)

Step 1: Parts, Materials, & Tools

I can tell that parts in the US are highly expensive. Here in the Philippines a typical resistor would cost 0.25 centavos ($0.0006), while in america, a typical resistor would cost $1 each. There's a large difference. Also, parts are available here almost everywhere. That's the beauty of living here when you have a hobby of electronics. My project cost me P870.00 ($21.75) all in all.


- LM3886 amplifier chip (2pcs.)
- 25 Volt, Dual Rail Transformer (Toroidal/ IE)
- Rectifier Diodes 6 Amperes (4pcs.) 
- 2x3 PCB board (2pcs.)
- Large Heatsink (2pcs.)
- Cooling Fan (1pc.)
- Plastic/ Metal Enclosure(1pc.)
- Binding Posts
- Female RCA Plugs
- AC Cable
- 20k 1/4 watt Resistor (4pcs.)
- 10k 1/4 watt Resistor (2pcs.)
- 15k 1/4 watt Resistor (2pcs.)
- 1k 1/4 watt Resistor (4pcs.)
- 2.2k 1/4 watt Resistor (2pcs.) 
- 10,000uF 25v Electrolytic (2pcs.)
- 10uF 25v Electrolytic (4pcs.)
- 2.2uF 25v Electrolytic (2pcs.)
- 470nF Mylar/ Ceramic (2pcs.)
- 150nF Mylar/ Ceramic (2pcs.)
- 100nF Mylar/ Ceramic (2pcs.)

It is added to my favorites list. I always wished to build my own amplifier. I believe this is the time to do it. Thanks for all the info.
This is a very interesting project, thanks for sharing.
<p>hello. great project!! one question. what is the power rating of the 25v toroidal transformer</p><p>regards</p>
Bro I M w8ing for u reply. Plz
Hi bro plz give me full detail and PCB layout plz it's a request
<p>Thanks for the guide. I notice that there are 2 ICs (LM3886TF) in the pcb you have given. However In parts list you have mentioned 2x3 pcb in 2 qty. since only 2 Ics are required for 62 WPC sterio, i am bit confused here. It would be great if you can clarify on this</p>
<p>does the transformer has to have a mid point? does it need to be 25V? and how do i know what current is enough?</p>
<p>Please help me, i dont know where to mount the components.<br>The schematic doesnt match the pcb layout.</p><p>Thx</p>
How to add volume controller any idea ? <br>I m using this amp from past 2 years I want to add volume controller I m puzzle to find out the right option help me out of you know about it . Thanks
<p>You can add a potentiometer at the input.</p>
<p>Hi i have just made this amplifier and it sounds great apart from when there is heavy bass it distorts slightly in the bass but im only useing a 2x12v transformer would this be the problem</p>
Why do you need a pre-amp? Can't you just plug your input from your CD player, FM receiver, Ipod, or whatever directly into the gainclone? Thanks for this, I've been thinking about building one of these for awhile.
The preamp enhances the audio input. There's also a tone control feature added to it.
where is the updated schematic? please upload i cant seem to work this project. i might be missing something. thank you
<p>What author probably means is that a &quot;preamp&quot; would add those additional features, but it is not part of this instructable.</p>
<p>Hi! When will you upload the Hi-Fi Preamp???</p>
<p>good day Sir ASCAS! Is it possible if I make the wattage higher? (e.g. make it 100watts)<br><br>if it is possible, what are the are the things that I need to consider, and what are the steps that I need to do.</p>
<p>Can one chip be used in a biamped setting? One channel drives the woofer, the other one drives the tweeter. I understand that when you have an active crossover, you need a bit less power, since the drivers are directly coupled to the amp.</p>
<p>Ordered a couple samples of these from TI awhile back. They may finally be taken out of their bags.</p>
Hey I' ve a question. How much amps does your transformer have. I mean how much va with 25 volts should it have at least. Sorry for my (bad) english. :)
<p>Hello,</p><p>I do not know if you still read comments that are posted here, but I have a question, that basically is the only thing stopping me at the moment. I have plenty of transformers that could fit this project. Problem is that none of them has ground coming out of it. So, would it work, if I would take ground from diode bridge, - just wire from connection between the two 10 000 uF caps? And run it in amp. As diode bridge provides +20vdc and -20vdc.</p><p>Thanks a lot.</p><p>Regards</p>
<p>Where did you get the transformer? They are so expensive on amazon.</p>
<p>From a local repair shop. They sell scavenged transformers from unrepairable appliances. </p>
<p>Oh ok thanks, I'll check Murphy's surplus (local industrial/military electronic scrap), they have all kinds of stuff, capacitors, transformers, vacuum tubes (valves) you name it. Is it possible to use an Ei transformer? Also, should I use a 5a output fuse for the output stage in case of LM3886 failure?</p>
<p>Yes Ei transformers work fine just be sure it supplies enough current to the amp. Yes, I would also recommend using a fuse. </p>
<p>So I've got a small undocumented Plitron, 2x115v primary (I've paralleled for my country- 115v), 2x9vac out and 1x15vac out, toroidal. </p>
<p>You need a transformer higher than 2x9v (dual rail). You could buy two of these, use each as a single rail 1x15v and create a 2x15v dual rail out of it. </p><p>:))</p>
<p>CAN I USE 12 PIN IC BASE FOR <strong>LM3886</strong></p>
<p>What do you mean by 12 pin?</p>
<p> can i use this for lm3886</p>
<p>There's no need to use a socket, it would just melt from the heat of the LM3886. </p>
<p>Hi. I'm new to electronics and I have a question. For the split rail supply, is it possible to use the circuit below instead of using a centre tapped transformer, because I can't seem to find an appropriate one on the web. Obviously, the half wave rectification will mean an increase in filtering capacitance, but will 20000uf be enough? Plus, is the signal ground down the middle able to handle the combined current from both Vcc and Vee? </p><p>Thanks in advance.</p>
<p>I think you may be over-exaggerating on the price of resistors in America... Maybe if you buy them from Radioshack (but they mark up damn near everything they sell) but if you just buy them from China or eBay the price is a lot lower.</p>
Great instructable!
I've never seen $1.00 for an American resistor!<br><br>
<p>Hi,<br>Call this a silly question but I see only one AMP (LM3886) in schematics. Is this like a schematics for a parts used to set up one AMP? And then the same schematics are repeated the same way for the second? If so, how are they connected?<br><br>Thank you in advance!</p>
<p>Yes, the single LM3886 is repeated for the second channel. </p><p>:)</p>
<p>Hello, ASCAS<br>I want to build an 2x50W amplifier and I'm basing it on your design. I'm new at audio stuffs and i'm having some doubts about the concepts....<br>I'll build two bookshelf speakers from a JBL two-way kit (Mid-bass + tweetter + crossover) and I was reading the LM3886 datasheet for the amplifier project.</p><p>My main question is: the LM3886 supports two output speakers, so why did you used two chips instead of one? All other projects use two chips too.... that's better? So in this case, if you use an mp3 player as input, each channel goes at one amplifier and the ground is common?</p><p>If you have some material to indicate to me, i'll be thankful!</p>
<p>Hi! It's nice to see that you're gaining interest in audio. Yes, it's true that a single chip of the LM3886 can support two channels. The reason why people use two chips instead of one is because they want to get twice the power (watts) of the output.</p><p>It's called amplifier bridging. Not all amplifiers are compatible to it. Luckily the LM3886 does. This is done by merging two input:output channels of one chip, in other words, you're assigning a single channel for each chip :)</p>
Thank you so much for the answers!<br>Actually, I realized that I need an 2x100W amplifier, because both speaker and tweeter has a power of 50W each, thus the total power per channel would be 100W.<br>My speaker/tweetter has an impedance of 4 ohms. Since the LM3886 delivers 50W into 8 ohms at Vcc=+/-35V, if I connect speaker+tweetter in series, I'll have a total impedance of 8 ohms. So I'll need 2xLM3886 to deliver 100W into 8 ohms, but when I bridge the LM3886, the output impedance changes?<br><br>If the output impedance is cut in half and my logic is correct, I can brigde 2xLM3886 to deliver 100W into 2 ohms at Vcc=+/-28V and connect my speakers in parallel to achieve 2 ohms output load. Is that right?<br><br>I can't connect a 8 ohms load into a 4 ohms output, but I can do the oposite, right?
<p>Luis, you are not correct. If you have a typical speaker which has a 50W woofer, and a 50W tweeter, plus a passive crossover (to send the low frequencies to the woofer and the high frequencies to the tweeter) then the proper amp to use would be about 60 to 75 watts. You can use a 100 watt or 25 watt or even 2 watt amp, but the trouble is, that if you use an underpowered amp, you get massive distortion if you try to run it full blast, or if you use an overpowered amp, and you run it full blast you will overpower the speakers. Two things that kill speakers are excessive distortion (DC clipping) or excessive power (Burnt voice coil). So you want an amp that is about 10% or 15% larger than what your speakers can handle so you can run it at a comfortable volume without the amp being maxxed out. So 68 watts amps for a 50 watt speaker seems about right. Just trust your ears when you are setting the volume, if it sounds bad or distorted, turn it down or your speakers will be nothing but doorstops in a few minutes. <br>As for ohms, two 8 ohm speakers connected in parallel make 4 ohms, two 8 ohm speakers connected in series make 16 oms. So you can wire up your speakers to suit whatever your amp can handle. A high quality amp can handle 2, 4, 8, or 16 ohms. The power decreases as the ohms go up, so keep that in mind. For this amp, I haven't looked at the spec sheet, but to be safe I wouldn't run it below four ohms. Heat increases as ohms go down so you wouldn't want to melt the amp by running it too hard.</p><p>Hope this helps.</p>
<p>I was reading the application report for the LM3886 and I can drive loads lower than 4 ohms using parallel configuration. In parallel (Quote: &quot;For example, using four ICs to drive a 1Ω load means that each IC dissipates 1/4 of the total power dissipation. In other words, the load to each IC looks like a 4Ω load&quot;). Look at the picture to see how I should wire my speakers (I intend to use a two-way kit). Since loads are setup in parallel, I need an outpute voltage of 14,14Vrms to obtain 50W at each 4ohm load, right? Using 2xLM3886 I can get this voltage, but I divide the total current for each CI. This way the amp run softer. Please, correct me if I said anything stupid =)</p><p>I don't understand why you've said to add 10 to 15% power to the amp. This will not burn my speakers? Or I do this, but I limit my input, so the output voltage never exceeds 14,14Vrms for 50W?</p><p>I read a lot since last question 15 days ago and I'm beginning to understand how to design the amp, but DIYs and people answering my questions has been REALLY helpful! Thanks a LOT!</p>
<p>Music power is not constant, it is always fluctuating. So what we are talking about is the long term average, or RMS wattages. There is a lot of flexibility built into the RMS figures. So don't think of the power rating of a speaker as a hard and fast figure you can never exceed. The speaker will probably handle four times as much power for a brief second, it's the long term average that needs to stay close to the speakers power rating. You could drive a 50W speaker with a 1000w amp, as long as you kept the volume low. Like I said above, don't let the amp distort, and don't let it run at much higher power than the speaker can handle for a long period of time, and you will be fine. Let your ears be your guide.</p>
<p>So you need 2xLM3886 for stereo output?</p>
<p>Yes.</p><p>The project has a bridged structure. A single LM3886 is capable of driving two separate channels, but for this project we bridged the two channels on each chip and assigned each chip for separate channels. This is done two double the amplifier's power output.</p>
<p>I only see one output and one V+ and V- in the pinout shown, so hows that two channels ? A single channel can provide 68W?</p>
<p>Hello, few years ago I tried to build 300w amp but I couldn't make it work due to bad parts, schematic or my own fault. Since most expensive parts are working (PS), I would like to build this specific amp. Only problem is high voltage of +-60V. What effect do you think it would have on this amp? Would it just gain more power (how much more?) or overheat and malfunction? I still don't have speakers for it. Thanks.</p>
<p>Just wanted to drop a message to say thanks so much for this instructable. Ever since i saw it on the featured email I wanted to build one (not even knowing they existed previously) and started collecting parts almost immediately. I now have a complete dual mono gainclone assembled but still in development on my bench and i love it. The reason it's still in development is that like you, I am putting a sound processor and source switcher (using a TDA7439, 16X2 LCD, DAC, rotary encoder and an arduino to control it all) in front of it and its almost complete. Thanks so much for the inspiration! And to anyone else - If you make one of these you will want to bin any other amp you own. The sound quality from these is AMAZING!</p>
<p>Awesome! I'm glad you like it! </p><p>___________________________</p><p>What a coincidence! I was finishing my Arduino Gainclone Amp when I received a notification from your comment :)) I was supposed to post the guide today but I'm struggling to find a &quot;digital volume control module&quot;. The remote + LCD display would be a waste if I didn't add a digital volume control. </p>

About This Instructable




Bio: Hi I'm Angelo! I am a 18 y/o college sophomore taking my majors in BS-ECE at the DLSU. I use my course as ... More »
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