This is a stereo amplifier kit designed to make use of the STA540 power amplifier IC. Once this kit is completed you have a fully functional, two-channel audio amplifier, complete with a standby switch, volume control and indicator LEDs. The kit also includes a 6400BG heatsink for the STA540 to dissipate any damaging heat.
In this kit, the STA540 is configured as a dual bridge amplifier capable of delivering up to 2x 38W (4Ω at 18V). Power supplied to the kit directly powers the STA540 and should be within 8 to 22V.
This kit comes as a bag of parts, you'll need to solder everything to the PCB. All components are through-hole, so it shouldn't be too difficult; but this kit is a bit more complex than our other through-hole kits.
Some users have noticed that their amp will oscillate or 'thump' when power is applied rather than operate normally. There are usually two causes for this and both are pretty easy to fix.
The first is that you may not have a power supply that can supply enough current for the kit to work. You need at least a 12 volt power supply that can provide 2.5 amps or more current. Supplies up to 20 volts will work but you still need 2.5 amps or more current to play it safe.
The second issue that can cause trouble is if you have a lot of flux leftover on the back of the board from soldering. We recommend that you solder all components except for the potentiometers first, then thoroughly clean off any leftover flux from the board. Once the flux is cleaned off, solder the potentiometers and you should be fine.
Hearing a buzzing sound? There are a few reasons why you might be hearing a buzzing sound. We have heard of problems with the audio amplifier kit due to the power supply or needing some additional decoupling capacitors. If the power supply is not providing constant power and is noisy, there can be problems amplifying sound. Maybe the bench and laptop power supply units are not giving enough peak current to your STA540 Amp Kit. Also, try adding as a shunt capacitor to reduce the lower signals out of the amplifier as opposed to in series which would increase the lower frequencies. Try looking at this tutorial for more information on stabilizing the signal => https://learn.sparkfun.com/tutorials/capacitors/application-examples . This might help with any issues using the audio amplifier kit.
This skill defines how difficult the soldering is on a particular product. It might be a couple simple solder joints, or require special reflow tools.
Skill Level: Rookie - The number of pins increases, and you will have to determine polarity of components and some of the components might be a bit trickier or close together. You might need solder wick or flux.
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Whether it's for assembling a kit, hacking an enclosure, or creating your own parts; the DIY skill is all about knowing how to use tools and the techniques associated with them.
Skill Level: Noob - Basic assembly is required. You may need to provide your own basic tools like a screwdriver, hammer or scissors. Power tools or custom parts are not required. Instructions will be included and easy to follow. Sewing may be required, but only with included patterns.
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If it requires power, you need to know how much, what all the pins do, and how to hook it up. You may need to reference datasheets, schematics, and know the ins and outs of electronics.
Skill Level: Competent - You will be required to reference a datasheet or schematic to know how to use a component. Your knowledge of a datasheet will only require basic features like power requirements, pinouts, or communications type. Also, you may need a power supply that?s greater than 12V or more than 1A worth of current.
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Based on 16 ratings:
2 of 2 found this helpful:
I had this kit together in no time at all. I do have to say I am experienced in electronics, but I still believe that anyone can do this. One thing that could really improve this product is a 3 mm stereo input jack. This would make a nice clean connection for a iPod or for a computer. Now with that said, something really fun you can do with this is pair it up with a Raspberry Pi with Shairport (AirPlay) and you can play music right off your iPhone. VERY COOL. I hooked this up to my Pi and some in ceiling speakers. The idea is you could have a Pi per room in your house and listen to different music in each room. Here is the link on how to setup the Pi with Shairport: http://www.raywenderlich.com/44918/raspberry-pi-airplay-tutorial
1 of 1 found this helpful:
had it together in no time, works perfect with my mp3 trigger, make sure to use a ground loop isolator, highly recommended. Cody from tech support was very helpful in my decision in choosing this amp, thanks Cody for all your tips.
2 of 2 found this helpful:
The simplicity, the clarity... omg the power in such a tiny little package. Add an option to bridge the input and outputs and you have a serious contender here. It's raw this is true but I've played with and owned pro grade qsc and crown amps and I'm simply blown away. And it only takes about 20 min to build if your serious about getting it done.
1 of 1 found this helpful:
I bought this kit in 2014 for a part of a project I didn't get around to. I've finally gotten around to finishing it and I'm impressed with its performance. I've noticed some background hiss (I haven't tried using a ground isolator as another review suggested) but the output is otherwise clear, even when turned up louder than I care to listen. (Hm. I should try temporarily replacing the amp for my my living room speakers with this and see what I think of it.)
Assembling the kit was straightforward, even though this was the first time I'd soldered any nontrivial PCB. (Make sure you have flush cutters — there are lots of bent leads you want to clear out of the way to get at the next joint.)
Here are some minor problems/inconveniences I encountered, some of which I think could be helped by changes to the design of the kit with little added cost:
• The spacing between the amplifier chip and heat sink is not quite right, or the assembly procedure needs improvement. I ended up with the chip being at an angle to the heat sink, not lying flat against it, which doesn't help heat transfer. (I'm glad I used a solid “thermal pad” which fills the gap with its thickness rather than heat sink compound.)
• It was very hard to read the capacitors confidently and tell them apart. I had to sort out all the capacitors and compare the number of each type I had to the labeling before I got them all straight.
• All of my audio sources have cables with plugs. While the screw terminals may be nice for using this as a component of a larger project, I think it would make more sense to include a 3.5 mm jack, or 2 RCA jacks, for input, and anyone wishing to direct wire inputs could simply leave the parts out and solder wires in place of the screw terminals.
• The included instructions say “connect 12V to the power terminals”. They don't mention, as the product description does, the larger 8V to 22V allowable range.
• I think it would also be worth mentioning that the input “-” terminals are wired to ground, and that the output “-” terminals aren't.
• The output screw terminals should be changed to ones that accept larger diameter wires or pins. There's plenty of room on that end of the board, and standard speaker wires can be pretty thick.
1 of 1 found this helpful:
I just assembled this kit, it doesn't work and has the following behaviors- can anyone think of an obvious mistake I may have made on assembly? - With 10VDC the power LED illuminates - With the switch on "Standby" the ON LED illuminates - With the switch on "ON" the ON LED turns off - With the switch on "ON," no amplified audio output, but a periodic thump every .25 sec and flash of the Peak LED as if a Capacitor is charging and discharging.
I'll assume user error here, based on the other reviews. Thinking I cooked a component or miswired. Any knowledgeable comments greatly appreciated.
Have you contacted our technical support department @ support @ sparkfun . com ? They're usually very good at helping figure out issues like this!
Overall the amp is a nice kit with great sound and small but simple construction. This kit did not come without a few flaws that I noticed as I constructed and used this amp.
First, the standby switch is in a terrible spot for even moderate use. If you plan on putting it in a small case like I did, then you won't even be able to get to it. The pots are long enough to protrude from any case but the switch is buried deep in the board. That's a moot point though since my switch didn't even last one day before it failed and wouldn't switch Vcc to the STA540 to disable standby mode. It only switched Vcc to the Standby LED which made this a little harder to diagnose. I have since removed the faulty switch and placed a jumper there. This is not my recommended solution though as now the only way to tun it off is to remove power. This typically results in a pop from the speakers.
Second, the individual pots for the left and right channel volume. This is definitely not a deal breaker as it isn't very difficult to get them close enough to the same volume for most listeners but might be an annoyance to some. Dual pots specifically for stereo channel volume control are readily available and I would have paid an extra dollar or two for a kit that was designed around one just for the convenience.
Finally, the size of the screw terminals is a bit too small. The largest size wire they seem to accept is 18 AWG and its a tight fit. Be careful when putting 18 AWG speaker wire in that you dont have any strands poking out that cause a short circuit. Terminals that fit 16 AWG and even 14 AWG might have been a better choice here.
I would still recommend this amp to anyone looking for a small amp kit with plenty of power for bookshelf speakers. I will be using this as a stepping stone to design my own amp with similar components to fit my needs. Nice work Sparkfun!
I built this to replace a BT/aux in amplifier in some powered speakers. In that, the BT would go off line with a power glitch. The aux in would drop out continually. I ripped that piece of junk out and installed this compact amplifier. It works as well as I hoped. Chromecast Audio is the input.
After assembly, I tried it with a lab supply I use for such things. At whisper volume the amp was fine. Increasing the volume resulted in a loud thumping and the Peak light started flashing. Tech support recommended a higher current supply. I tried connecting it to my car battery. Same problem. I was given a refund. I think the problem is that the amp is not rated for 4 ohm speakers as stated in the spec. or maybe there is some kind of feedback causing the pulsing.
I purchased this to serve as a test-bench amp for some Thiele/Small parameter measurement work as I knew I could get schematics and parts for repairing the thing if it did spew magic smoke all over my bench (vs. a commercial stereo amp which might have unobtainium parts and no service manual to speak of). As a result, I can't really speak to its audio quality, although I'm sure it's reasonable for the parts list and price.
Assembly went fine until I hit step 12, where I ran into a 1000uF obstacle while trying to stuff the slide switch. I was able to retain it in the PCB by bending its pins with needlenose pliers, but the results were still undesirably cockeyed. Likewise, with step 14, I had to use the heatsink as a prop to retain the terminal blocks while I soldered them in. This could be fixed easily by moving steps 10/11 (the electrolytic caps) after steps 12-14 (the slide switch, LEDs, and terminal block). Step 13 itself is another potential pitfall as while the written instructions for LED insertion do a very good job, the silkscreen on the board has barely any visible indication of LED polarity. This could be trivially fixed with a diode symbol in the silkscreen layer, as documented in https://blog.screamingcircuits.com/files/led_markation_guidelines.pdf While you're at changing the silkscreen, by the way, moving the electrolytic cap polarity marks outside the footprint of the capacitors would be nice -- it'd sure make checking your work easier!
Also, like other reviewers, I had difficulty with getting the STA540 and its heatsink installed. I ended up (after some false starts) tack-soldering a pin on the STA540 to get the part to have the correct relationship with the HS while I soldered the latter in. Furthermore, the kit doesn't come with heat-sink grease, something that should be stated a bit more clearly at the beginning of the manual. Luckily, I had some Arctic Silver 5 left over from old PC builds, but this could really bite someone less experienced.
Once it was put together, I put it through some brief tests with the speaker DUT in question, in my case the 4ohm version of the Visaton SL87XA (a small, although high-power-rated, full-range speaker), and fed it a couple of 1Vrms sines (1 and 1.5kHz, to be precise) from my trusty function generator while powering it with ~9V from my bench supply. The amp functioned OK in this checkout, drawing ~400mA at low-ish volume levels, save for the regular popping or thumping other reviewers mentioned, which seems to be an internal issue when the amp is ON but lacks an input signal. I haven't done any probing around to try to reveal if the pops or thumps are coming from the input stage or the power amp itself, though -- it's not an issue for my intended usecase as long as it doesn't interfere with the measurements I'm going to be taking.
Overall verdict: functional, but no Heathkit -- the manual, while well-illustrated, falls short on a few rather irksome points, and the board silkscreen could stand to be improved in a couple spots as well. Also, while the popping isn't an issue for me, it's a much bigger nuisance in more...musical uses of this amplifier.
OMFG! With a phono pre-amp (ahem, sparkfun, you should sell a kit), this was epic! Listening to Steve Miller, Living in the USA, I was back in 1968! This is a really cool kit, easy to build, fun to implement. Thank you. With all that's digital and cool, don't stop making neat stuff like this!
Easy project to assemble. I hooked mine up to two 30W Celestions and an Ubuntu Studio box doing stereo guitar effects processing. That, plus a little op-amp preamp to provide a high-impedance buffer between sound card and the guitar (important!) makes a full-featured guitar amplifier project. A little extra work to make a cabinet for it and it goes places too!
Bought this to drive a pair of 40W bookshelf speakers - now I have a great computer sound system!
I was BOM'ing an amp for a project using a different chip. Once I hit a certain dollar amount, I thought 'hey, I wonder if there's a kit.' Found this jewel, and glad I did! So, here's "just the facts:"
- well made plated-through PCB with solder mask and component silkscreen - circuit implements a manufacturer's reference design for the IC in 2-channel BTL mode - component selection is reasonably conservative, nothing is working too close to its allowable rating
Just my thoughts:
- this is a quad amp IC bridged into stereo BTL- the people who built the kit and just got thumping out are probably trying to ground the outputs!
- to reiterate that- the output + and - are for speaker phasing, do not connect them to ground! Both sides are driven, like an H-bridge - do bother to look at the IC datasheet, it will answer most questions and fix most problems - its form factor is a little awkward for trying to come up with an enclosure - never mind the "38 watts"- again, look at the datasheet, consider speaker impedance and power supply voltage - I am going to buy it again for another project!
Random: I would knock 1/2 star for mechanical considerations. Nothing that couldn't be worked around. What works best for me may not work best for you, and this is not a finished consumer product, it's a kit!
Seriously great amp, especially for the price. Good quality sound, and powerful.