Introduction: Make Your First Serious Amplifier

Picture of Make Your First Serious Amplifier

I did it! I've always wanted to build my own amplifier, and now, finally, I made one. It's my first "serious audio" project ever.

Starting this project was daunting to me. There was a gap between buying the parts and actually making the amplifier... a two year gap, as a matter of fact. I know a thing or two about analog electronics and I can read and understand electronic diagrams, but I never made something from scratch that connects directly to a wall outlet. And I usually make stuff with electronics either for kids or as a "proof of concept", where accuracy and details matter only little. In other words, I was just insecure about me as a maker of Serious Amplifiers.

What helped me to get started is that I just needed an amplifier. I love to play music and the best sound system I had was my iMac. And that proved not good enough for me. So I had the choice between buying a cheap receiver while knowing I had all the parts for a much better amp or just get started building it. Oh boy, I am SO glad I did just that!

If you find yourself dreaming about building an amplifier now and then, but are not sure about how to get it done: Read on! I described the making of my Serious Amp as good as possible, including the mistakes and successes. The result is not a Perfect Amp, but it surely is a Serious One that is not that hard to build even if you never built one before.

This amplifier is the best one I've ever owned (that claim isn't worth very much) and I'm really, really happy with it. Even with my secondhand (€10,-) loudspeakers it sounds pretty nice. In the video, the sound is recorded with the on-camera mic. What you hear is far, far away from the real life experience.


The amp is a so called Gainclone, using one LM3886 op-amp per channel. The power supply is based on a (way too large) 230VA toroid transformer. It took me about 32 hours to build the amp and power supply.

In this Instructable, I'll describe how I made the power supply and amplifier. More important, I'll also describe what I would do different if I had to do the project again.

Step 1: Links: Get a Grip on the Gainclone Universe

Picture of Links: Get a Grip on the Gainclone Universe
I'm not an audiophile and not an expert on amplifiers either. So when I started to look around on "how to build a Serious Amp", I entered the universe of Gainclone amplifiers. Looking at the sometimes gorgeous designs, I realised I wanted to build one of these babies myself. There are many different ways to build them, so browse around and get yourself familiar with the world of gainclones...

  • Mark Hennesy's website: Very, very nice amps and great info on gainclones and powersupplies. Great pics and comments on how he built it. The most inspiring resource I found.
  • Wikipedia article on Gainclone amps and where they come from.
  • The Chill Amp: Well documented site, including schematics and parts list.
  • Chipamp.com: I used their circuit diagram for the amplifier (the pdf is available on their site. Comes along with good tips on building amps). They also sell kits and parts.
  • DIY Chip Amps: Nice listing of several DIY gainclone amplifiers.
  • Audiosector.com: Stunningly beautiful gainclone amps.
  • Decibel Dungeon (that's an audio-nerdy name :-)): Schematics for a gainclone amp and a power supply.
  • Decibel Dungeon Gainclone Gallery: Nice collection of DIY gainclone amps.
On Instructables are just a few gainclone projects. ASCAS' DIY HiFi Gainclone Power Amp is an example.

You may have noticed that there are a lot of slightly different schematics and op-amp types that can be used. Not being an expert, I found it hard to make a choice. I turned to a friend who I consider to be an expert for advice. He convinced me just to choose something simple and trustworthy. The differences in the circuits are about details, which are hardly relevant when building your first amp. Novice mistakes will be made and those will have much more impact for the worse than the refined details have for the better.

What I really like about the Gainclone is the minimalistic approach. The general rule with Gainclones is the less components, the better the amp. This comes at a prize, of course: The quality of the components and their specs become more important, since there are so few components to create the sound.

Step 2: Parts

Picture of Parts
Depending on your configuration of choice, you need the parts. This is what I have used:

Power Supply:
  • 1 toroid transformer with double secondary windings: at least 120 VA max output, 2x 12-18 Volt. I used a 230 VA 2x 18 V model, which is really too big for this amp (over 300VA is considered overkill for any amp, so I'm pretty close to that :-))
  • 2x 10,000 uF / 35 V electrolytic capacitors
  • 1x rectifier module KBU1005
  • 1x Anti-interference filter for mains supply: Kemo nr. M41 (I only used it because I had it lying around. I would have left it out otherwise)
  • 1x switch. I already had a very nice old model.
  • 1x male power plug, Euro model. These plugs are also sold with an integrated power switch, like this one.
  • 1x 3 Amp fuse with socket
  • 1x 10mm red LED
  • 1x 100 kOhm resistor to dim the LED
  • about two meters of heavy duty power cable. I used loudspeaker cable for the power cord to the amplifier, and regular power cord for the internal wiring

Amplifier:
Electronics:
  • 2x LM3886 op-amps
  • 1x 22kOhm potentiometer, logarithmic scale.
  • Resistors: 2x 2.7 (2 Watt), 2x 680, 2x 1k, 2x 10k, 4x 22k
  • Capacitors electrolytic: 2x 47 uF, 4x 100 uF
  • Capacitors film (MKP type): 4x 0.1 uF
  • Something that can act as a heatsink for the op-amps. I used a piece of aluminium tube (square profile, 30x30 mm)

Connectors:
  • 1 set of RCA "audio-in" connectors. In Dutch, these are called "tulip plugs". I'm not kidding.
  • 2 sets of lab connectors to connect the speakers
  • 1 set (male and female) 3-way XLR plugs, to connect the power supply to the amp.
  • A piece of aluminium to mount the connectors in. I harvested a piece of 150 x 60 x 2 mm aluminium sheet from a discarded PC.

Casing:
Anything you like, of course. I used birch plywood, 9 mm thick and alkyd-based clear varnish used foor floors and stairs.

Costs:
All together, I spent around €100,- for the whole project. The toroid transformer is the most expensive part by far: €50,-. The op-amps cost around €9,- each, the big electrolyte capacitors are around €4,-. Please buy a decent potentiometer. I discarded two of these because they caused noise. The one I use now is so-so, for €6,- (which is PEANUTS for a potentiometer in audio, but I'm on a low budget).

Step 3: Size, Footprint and Design of the Amp

Picture of Size, Footprint and Design of the Amp

I decided to make separate casings for the power supply and the amp. Thus I can choose to stack the casings or set them side by side.

I made the casings out of wood, because I'm more comfortable with woodworking than with metal. Besides that, I have a thing with clear lacquered birch plywood. I have a bookcase and a dressoir made from it and my daughter sleeps in an ubercool birch plywood bed.

Wood isn't a very sensible choice to make audio-equipment casings from. Most parts that go through the casing (connectors, switch, indicator light, etc.) are designed for mounting in metal cases. 9mm wood is just too thick for most parts to protrude. So for the connectors on the backside of the amplifier casing, I decided to mount them into a separate plate of aluminium, and screw the plate onto the inside of the backside of the casing.

To get a grip on the size of the casing, the size of the power supply is leading (the PS has the largest components by far). I laid out the components on a sheet of paper and found out the whole thing can fit into a rectangle of 148.5 x 210 mm (that's the size of half A4, the document standard in Europe).

The top of the casings is a sheet of perforated aluminium. The sheet I used is 0.8 mm thick, which is a bit too thin: The sheets tend to sag a little. I'm looking out for perfed aluminium sheets of at least 1.5 mm.

Step 4: Circuit Diagrams

Picture of Circuit Diagrams

These are the circuit diagrams I used. I built them without PCB's, all components of the amp are point-to-point soldered on the chip's leads. For the power supply I used loudspeaker-cable and regular power cord to connect the components.

The secondary coils of the transformator must be connected. To do this right, you must find out which wires to connect. Connecting the wrong leads will result in a 0 Volt output. When connected the right way, you should read 40 to 50 Volts AC. I used an oscilloscope to find the right configuration, but it can also be done with a multimeter, set on AC Voltage.

The rectifier bridge (KBU1005) needs some cooling. I mounted it on a piece of aluminium.

For more info on the circuit: I added some comments with the pictures. Have a look.


Step 5: Prototype the Power Supply

Picture of Prototype the Power Supply

Not very hard, this step. The power supply has only a few components and is easy to prototype. I connected the parts with connectors and crocodile clamps and hooked it up to an oscilloscope. It worked right away for me.

Step 6: Prototype the Amplifier

Picture of Prototype the Amplifier
I found prototyping the amp's difficult. That might have something to do with my choice for point-to-point soldering. Although p2p soldering is not very difficult, it does make the wiring a lot more complicated. I almost had to build one entire channel to be able to test it. If you're reading this: I'd love to have some advice on this...

Here's how the op-amp looks like with the soldered parts:


If I had to make an amplifier again, I would use PCB's instead of the point-to-point soldering. But I never made custom PCB's before, and the op-amp's pins don't fit in the veroboard I normally use.

  • Cut away leads 2, 6 and 11 from the op-amp (picture 1)
  • I used a third hand and non-hardening clay to fixate the parts to be soldered.
  • Start soldering the parts directly on the pins:
  • Solder the 22k resistor from pin 3 to pin 9 in pictures 2 and 3 (it's the feedback path. The connection should be as short as possible). Cut away the protruding leads entirely.
  • Solder the 10k resistor between pins 4 and 8 (picture 4). This time, let the resistor protrude from the op-amps chassis. You need the length of the resistor's leads to mount other parts on. Pins 4 and 8 are pretty crowded.
  • Solder the 100uF cap's minus side to pin 8 and the 10k resistor (picture 5). Try to make "solder-time" as short as possible. By heating up the resistor it tends to get loose from pin 8.
  • Connect pin 7 to the plus-side of the 100uF cap with a piece of bare solid wire (I used jumper wire from a breadboard) (picture 6).
  • Solder the 680 Ohm resistor to pin 9. Take care not to un-solder the 22k resistor on pin 9 (pic 7).
  • Solder the 47uF cap's minus lead to the plus-side of the 100uF cap. Connect the plus-lead of the 47 uF cap to the 680 Ohm resistor (pic 8).
  • Solder a piece of solid kern copper wire to pins 1 and 5 (pic 9). I bent the pins into a small arc so the copper wire wouldn't roll away too easily. Let the wire protrude.
  • Finally, solder the wires to +V, -V and ground to resp. pins 1 and 5, pin 4 and pin the plus-side of the 100uF cap (pics 9 and 10).

Repeat this for the second op-amp. But again, my advice is to do this on a PCB if you know how to. I would, however, solder the 22k resistor directly between the op-amp's pins 3 and 9. PCB or not.



Step 7: Volume Control, Connectors and Wiring

Picture of Volume Control, Connectors and Wiring

Now that you have the amps, it's time to connect power, ground and signal on the plate. I found this the hardest part of the project. That might have something to do with my choice for point-to-point soldering instead of using PCB's. It's wisdom that comes with hindsight, but if I ever make another amplifier I'll use PCB's for sure. The drawing in picture 1 is an attempt to show how I set it up.

I'm not very happy with the result. I'm confident that the wires and connections will not cause shorts, but boy, what a mess! If I ever make another amp, this is the part that I'll want to do better.

Here's how I organised the wiring:
See pics 1 and 5. Grounding: At first, I wanted to ground all components in one place. I read about "ground star-configuration" over here, and it made sense to me. But there's a price to pay: The many wires to the central ground cause a true spaghetti incident in wiring. So after a failure or two, I decided to ground the parts in two different but close spots.

Volume control:
Start easy. See picture 2. The middle lead goes to the amps through a 1k resistor. One other lead goes to ground, the remaining lead must be connected to the input. It's a matter of paying attention and soldering two resistors per channel onto the potentiometer.

Connectors:
I mounted the connectors to an aluminium back plate. The trouble with wiring starts here: All connectors must be grounded, resulting in 6 leads to the "star ground" M4 bolt in the back plate. Try to cut the grounding wires as short as possible. Loopy wires take up space. See pic 3. Start with choosing one of the XLR-plug's pin as ground and connect it to the star ground. Also connect the star ground in the back plate with star-ground 2 on the "floor".

V+ and V-:
See picture 5: I made leads for the V+ and V- connections with solid kern electrical wire. The wires are mounted in 16 amp connectors which are screwed onto the wooden floor. Solder leads from the XLR plug to the V+ and V-.

Write down the XLR's pin numbers that are now connected to Ground, V+ and V-. You will need that when you connect the other side of the XLR plug to the power supply's power cord!

Heat sink:
I glued a piece of alu tube (30x30 mm) over the width of the floor with epoxy. I made some halfway cuts in it to improve ventilation and add some area. The disadvantage of this configuration is that the line-in wires and a ground wire must go through the heat sink. I covered the wires with heat shrink tube to protect them against the heat. Better safe than sorry.

Connect it:
All is ready to be connected now. Connect the potentiometer to the lines-in and ground through the heat sink. Then mount both amps on the heat sink. Start connecting the wires one by one, cutting them as short as possible. Use shrink wrap to isolate the soldered connections where possible. The spaghetti incident is happening right under your hands! With some patience and a decent soldering iron, you'll get there.



Step 8: Build the Cases

Picture of Build the Cases
The wooden cases are fairly easy to make. However, it's easy to mess it up.
I made the cases from 9mm birch plywood. They had three coats of clear lacquer.
I added many pictures of the making of the casings. I think the pics are pretty self-explanatory...

Here are some tips. I learned some of them the hard way...
  • Use decent tools: Sharp saw and drills, screwdriver that actually fit into screws, etc.
  • DON'T RUSH! It will not save you time in the end.
  • I remembered just in time to label the panels before sawing them. With the labels on the panels, I could make the grain of the panels continue from one panel into the next when the power supply and the amp are stacked.
  • Drill all holes before glueing the panels together.
  • I don't have a cutter. I used the table saw to make the groove in the panels for the aluminium sheets. It works well, but the groove is a bit wide (2.5 mm).
  • Clamping the panels while maintaining the angles straight is always difficult for me. This time, I made an extra panel with the same size as the bottom and used that as a placeholder for the clamped panels. It worked pretty good.
  • Apply the coating in broad daylight! Especially with the second and third layer, it's sometimes hard to see whether parts are missed.
  • My first layer of lacquer was too thick. It started dripping after I was finished. It took me careful sanding to get rid of the drips.


Step 9: Fitting the Power Supply in It's Case

Picture of Fitting the Power Supply in It's Case

Compared to the amplifier, wiring the power supply is a piece of cake! I mounted the parts on a separate wooden floor. The mains plug, the fuse, the switch and the indicator LED are fitted in the case itself.
Browse through the pictures to see what I did. It's not a hard job.

The toroid transformer is mounted on the floor with a 60 mm bolt. I drilled a 20mm hole in the bottom of the case, so that the floor can ly flat on the case's bottom.

In the floor, I drilled two 35mm holes to fit in the big capacitors and I cut away a rectangle to fit the mains filter.

I used a tie-rap around the power cord on the inside of the box as a strain relief. Just in case someone decides to lift the power supply by the power cord...



Step 10: Play It Loud!

Picture of Play It Loud!

That's it! As said, my first Serious Amp is the best amplifier I've ever owned and I'm very happy with the result. It's not perfect, though. When the volume is turned up without music playing, a soft noise comes up. It's inaudible when playing music, but it's there. I think it comes from my cheap potentiometer, but a small cap in the line-in might fix it as well. I'm going to have a look at it when I find some time. For now, I totally enjoy playing music. Loud!

Next project: Making a pair of decent loudspeakers :-)

For people reading this who never built an Amp but always wanted to: Just do it! I hope this I'ble gets you the motivation and confidence that you can. If you have questions, write them down in the comments. I'll try to answer them as good as I can.

For people who made Serious Amps before: Please leave your comments and tips for others. It'll be appreciated by me and hopefully a lot of future Amp-builders.

Comments

mfaust made it! (author)2014-05-18

Thank you again for this great instructable. I've finished my first gainclone this weekend and can't count the hours I've stared on this page. Also, thank you again for your help. I forgot to ground the secondary coil during my first attempt which (according to a friend) causes a "floating" of the current. However, it finally works perfectly fine, without any noise. I've attached two pictures, the wiring is not as nice as yours, but works for me :)

ynze (author)mfaust2014-05-18

Wow! Thanks so much for your pics and nice comment! Your amp looks GREAT, thumbs up! You added a second line-in, didn't you?

Cheers, Y.

mfaust (author)ynze2014-05-18

Yes, it's a second input. I am using the amp for CDs and PC and since I already had the parts I thought it's more convenient.

KayH44 (author)2017-08-03

I found this amp as the best on here but it is very big because of the power supply.

Any idea on how to shrink the power supply to the minimum?

Like smaller Transformer

justusbernold made it! (author)2017-01-01

This instructable finally "pushed me over the edge" and I made it - finally. Many thanks to ynze!

Currently I'm still searching for an error in the implementation as the gain is not as expected :-(, but I think I'm almost there.

Nevertheless: here some pictures of my first serious amplifier :-)

Below some pictures of my interpretation .

MrCheatak made it! (author)2016-09-12

Great instructable! When I found this instructable, I didn't even think I could build an amp, but here it is! Well, my wiring not that neat, but I hope it saved some space and it works. God, how many times circuits stopped working and I thought I've messed with the chip, but it was just disconnected ground or bad soldering.

There's a couple of things that I added:

I added a 100 Ohm resistor between V+ and V– terminals, that switches on when power is off to empty those giant caps (without that a led, which is also between V+ and V– parallel to amp circuits, would stay on like forever). Use at least 1watt resistor for this. Also I've made amp pcbs one under another to save space.

There's one little thing I had to figure out myself: to turn linear potentiometer to logarithmic, you need to insert certain additional resistance between input and output, for 50kOhm potentiometer it's 10kOhm.

ynze (author)MrCheatak2016-09-18

Thanks so much for this post and for hitting the Made It button! Great to hear that the I'ble was useful for you!

Y.

MrCheatak (author)ynze2016-09-18

I've got a little problem here(
Sometimes sound just goes off. Switching on and off helps but then it repeats. What could be the cause? Overheating?

ynze (author)MrCheatak2016-09-18

It might be overheating. The chip-amps turn off when overheated. Your heatsink seems large enough though. Is it hot just after the sound turns off? Is your case perforated, so that hot air around the heatsink can flow out?

MrCheatak (author)ynze2016-09-19

I checked chip-amps right after sound went off and they were just warm(after ~5min). If it's not heating then may be it's something with the power? I measured voltage between V–/V+ and Ground and it was rising with V+ and going down with V–, then reaching 8.9V when sound went off.

It was a damaged trail on power pcb, resulting in 550Ohm resistance which didn't let caps recharge simultaneously.

Hope this will help someone.
Sorry for bothering, man

rmenchon made it! (author)2016-09-11

Thanks so much for this instructable! Thanks for documenting it, it sounds great! At the end I decided to make the power source as 2 dc sources connected in series as in http://www.markhennessy.co.uk/articles/power_suppl... the rest is exactly the same :)
I also made use of a kind of pcb for the components, reinforcing some of the connections just in case there would be too much intensity. Sound is very nice and can power up my speakers with no problem at all. For the heatsink I used a piece of metal and attached on top a couple of spare small heatsinks that I had around. I just need to change the potentiometer, it turned out to be noisy for a particular angle. I add couple of pictures. Thanks a lot once again!

ynze (author)rmenchon2016-09-18

Wonderful! Great build, thanks for the post. Posts like these always make my day :)

Y.

baltot made it! (author)2016-07-04

Thank you for this instructable. It got me looking at all kinds of circuits and here is the final incarnation of my amp and pre-amp. I blew 1 channel early on before doing a proper job of a signal earth star (and power earth star), so re-made it, & then improved the power supply...... & then decided to add a mute switch instead of the volume,.....& FINALLY built a pre-amp with a stepped attenuator. Decibel Dungeon is a great site, so thank you very much. Sounds better than the Cambridge Audio amp it sits next door to. I also used some thick plexiglass from a broken kitchen chair to make the lid windows.

Cheers,

Ed

ynze (author)baltot2016-07-05

You're very welcome! Your amp looks really great. Thanks for posting this, you just made my day :D

Y.

RobbieD10 (author)2016-03-16

Going to be attempting this in the next week or so. I am going down the route of separating the signals with banana plugs due to it being a work project. Will be using a hammond enclosure and transformer(Work).

jimvandamme (author)2016-01-27

I'm surprised TI still makes these amps. They were pretty good in their day, and found their way into many stereo receivers and TVs (along with many competitors' products). Nowadays you'd use a class D amp, and save yourself a bunch of money on power supply and heat sinking.

abrogard (author)jimvandamme2016-02-14

You seem to be saying that there's a better way to go than this design, then? Could you direct me to an example I could follow, perhaps? I was thinking of making this, it'd be a first for me, but if there's a 'nowadays' thing that saves a heap of money.....

jimvandamme (author)abrogard2016-02-28

Sorry, I was in Guatemala and just got back, long story.

I don't think a class D amp should be your first. Layout is tricky when there's a lot of square waves circulating around. Learn how to make something that works. If you just want to save money you can buy Chinese boards from ebay, but you won't learn much.

abrogard (author)jimvandamme2016-02-14

You seem to be saying that there's a better way to go than this design, then? Could you direct me to an example I could follow, perhaps? I was thinking of making this, it'd be a first for me, but if there's a 'nowadays' thing that saves a heap of money.....

jonkendall (author)2016-02-26

great instructable ynze, I'm gunna need it! I'm a complete novice and this will really help with my project. Just wondered if you'd be able to let me know how I'd go about wiring in 3 inputs as opposed to one with a selector switch and also a pre-amp for phono channel. Thanks, Jon.

Lee Wilkerson (author)2016-02-12

BTW, the LM-3886 is rated 38W Continuous Average Output Power into 8Ω at Vcc = ±28V with 0.1% THD+N from 20Hz–20kHz. (Source Texas Instruments)

Since you're only supplying ±25V, it will be more like 35W which is still plenty of power for most people.

Lee Wilkerson (author)2016-02-11

Great Instructable. I have built many audio amplifiers in my day (way back before there was an internet and Instructables).

Your DC voltage should be 1.4 x AC voltage. It is the result of rectification of the AC wave itself from the point where voltage is being coupled across the diodes + the small amount factored in by capacitive action. KBU-1005 Vf (forward voltage) is 1.0 V for 5 A so when the amp is drawing 5 A, the diodes are in pairs dissipating 5 W x 2.

Your DC current will be the reciprocal (.71 x rectifier input current minus the heat wasted in the diodes, capacitors, and transformer).

CatalinRO (author)2016-01-29

Awesome build, congrats! After a long time when I saw only Arduinos and digital electronics :) Once I saw someone on Instructables adding a simple audio Bluetooth connection (A2DP) to such amplifier, perhaps it will make it more attractive to be built by young people (n.b. you can connect it to your smartphone - tadaaaam) -

http://www.ebay.com/itm/3-5mm-Stereo-Audio-Music-Speaker-Receiver-Adapter-Dongle-USB-Bluetooth-Wireless-/381282219096?hash=item58c630f458:g:zVEAAOSw3xJVbpYm

tiger12506 (author)2016-01-25

That 47uF cap between the 680 ohm resistor and ground. It is there to block DC from the negative feedback of the amplifier. What it essentially does is allow the negative pin to float as seen from DC, which will help prevent your amplifier from applying an amplified DC offset value which would hurt your dynamic range and put unnecessary current through your speakers causing undue stress.

tiger12506 (author)tiger125062016-01-25

Also, see here for more technical descriptions of what everything in the circuit does. I just googled for the chip LM3886 and found datasheets and application notes.

http://www.ti.com/lit/ds/symlink/lm3886.pdf

http://www.ti.com/lit/ds/symlink/lm3886.pdf#page=8...

swander (author)2016-01-24

thats a great project. consider wire wrapping instead of "P2P" soldering. It easy with a cheap wire wrap tool and makes a nice connection that can be unwrapped if you make a mistake. Many old Zenith components from back in the 50's were wire wrapped by hand. Mount the components through a rigid medium like 2.5mm plastic and then drill tiny holes for the leads. then if you want to get really fancy, you can wrap the wires with an insulated ground to shield them after its all done, justremember to tie it to the ground plane. Very nice.

Jamlaser01 (author)2016-01-24

Great presentation. Your written dialog is refreshingly clear and even pleasant to read. A similar, but refined version of my old, "How to fix your VW for the Complete Idiot" It, and you, make a seemingly impossible task, a simple, and logical task of common sense.
Thanks. Please post any other projects that you may attempt. I will gladly read about the journey.
Thanks, John Millington

kobyx (author)2016-01-24

Excellent design, congratulations.

Tumunga (author)2016-01-24

When I saw the word "imac" I quit reading...JK!!! LOL!!

fortney (author)2016-01-24

You did a wonderful job-congratulations. I have one mono gainclone and am very pleased with it.

Re: breaking out of wood when drilling: I put tape over the to be drilled area and introduce the drill through the good side of the wood panel through the tape. Or drill from the wood backside while holding the wood panel firmly against a flat piece of scrap wood.

MoritzC (author)2015-07-24

Maybe it's not the best idea to put something you attach to the powergrid in a flammable wooden box?

ynze (author)MoritzC2015-07-27

That crossed my mind as well, but then I thought: 50 years ago most boxes containing electronics were made from wood. The casing can withstand some big sparks for sure. If you want a really fireproof box metal sheets seem the only way to go...

VincentJ2 (author)ynze2016-01-24

For almost all my projects I use acrylic boxes. It cuts as easy as wood. If you find an acrylic supplier you can usually pick up pretty decent sized scrap pieces for about a $1US(€0.93) per pound (0.45kg) The only tricky part is the acrylic glue is really runny and if not applied carefully can look crappy. But if you use metal L brackets to hold the box together they can absorb a pretty decent sized explosion. Acrylic can also be tapped with thread holes for mounting heat sinks or chassis grounds.

ve6cmm (author)2016-01-24

Nice Job.

I like the way to built the power supply, although I would think that the heatsink if much too small for the amount of power that you use.

The cases look incredible. You did a fantastic job of putting these together. A finished case like this makes the whole project look professional. I wish I had that type of talent!

I do have a bit of a concern with the amplifier itself. As it is, it isn't very robust and you will have to make sure that it won't get bumped hard, or be in an area with a lot of vibration. P2P wiring such as this will eventually rear it's ugly head.

One thing that came to mind was your use of aluminum tubing as the heatsink. This is brilliant. Another idea would be to cut more slots into the tubing and then put a fan at one or both ends to really get the airflow happening. This will keep the amps reasonably cool. Having the slots on the side would allow air to escape on both sides as well.

All in all, a beautifully made project. I have been looking at building a tube guitar amp for a year or so myself but haven't had the time to get to it, yet. I have had all the parts and more for over a year! You have given me some great idea's and better yet, the inspiration to do something about it!

RobertH25 (author)2016-01-24

THIS is the kind of project that got me into electronics longer ago that I care to remember.THANKS!

Rand0mUser (author)2016-01-24

Nice work! I know this is quite old now but it just got featured in the Instructables newsletter. The 25V DC is a result of the AC peak voltage being significantly higher than the value always given (larger by a factor of the square root of 2) - under low loads or with no load, the voltage output from a transformer, bridge rectifier and capacitor can be quite high.

mheramil (author)2015-12-15

can i use .1uf mylar instead of mkp? whats the difference?

mheramil made it! (author)2015-12-14

got my first seriour amp. thanks for the instruction.

ynze (author)mheramil2015-12-14

Very cool! Cheers!

Y.

ironwood69 (author)2015-07-14

Hey man, very impressed with this amp. What would be your thoughts on scaling up the output wattage to around 200/500 watts?

ynze (author)ironwood692015-07-27

Uhhhmmmm... You would need either an entirely different op-amp, or design a grid of at least four LM3886's to distribute the power. And then take care of the heat that comes with 200 to 500 Watts. The design of my amp is not suitable for that kind of power...

kriksis (author)2015-01-26

Hello,

I finished both amps and instructions are very nicely written, but I have trouble with potentiometer resistors. Could you maybe post a bit clearer image or schematic how to hook it up and what values to use?

I know that your aim is not to make AMPs for Dummies 101, but I would appreciate so much if you could post the remaining part of the build in similar manner. At the moment I have real trouble figuring out the output safety mechanism and potentiometer resistors.

Thank you much, if you will have time, if no, wish you best with what you're doing. :)

Regards

Faulty LED (author)2014-05-19

Could you give us some computer generated schematics? I find them easier to read. Eagle is a good program.

pmk222 (author)2014-02-09

this is a great instructable, very easy to follow. i have always wanted to own an amp that worked well, but not having a lot of money or knowledge i figured building one would be the best but never found a good, easy to follow guide. i will definitely be using this to build one for my next serious project.

aalejo (author)pmk2222014-02-24

ok if of you have a problem with that my i suggest!!!!!!!!!!! lm386 half watt ic!!!! i try that one man makes satisfie you self if you the 386 one

aalejo (author)aalejo2014-02-24

and less cheaper than to make and too powerfull and smokey !!!! you will love it

pmk222 (author)aalejo2014-02-24

i will research the usage of this, if i can figure it out i may use this idea, thanks!

aalejo (author)pmk2222014-02-24

ill give a schematic in the breadboard i wanna make this!!! and work !!! there was a secret about my schematic that make distortion clear !!! figure it out !!!! so it will help you for first speaker and!!!! by the way!!!!!! there have some missing connection for it and is the!!!!......... hahaha figure it out!!!!. so it will may get you been un the challege!!!

aalejo (author)pmk2222014-02-24

your welcome!!! :D

Dunluce (author)2014-01-30

Enjoyed your project and its inspired me to try to build one. My knowledge of electronics is quite limited but I have been reading up a bit on some of the sites you suggested. One question, where do you connect in your switch, LED and resistor? I don't see them in any of your schematics.

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