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Chip Amps Amplifiers based on integrated circuits

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Old 13th July 2012, 04:21 AM   #11
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Join Date: Jul 2012
I'm sorry arty. I was crunched for time when I responded to you, I may have confused you. but yes, I am fairly new to DIY audio. you're right though, a small degree of success builds moral.

that class h amp sounds perfect for the project which originally led me here, which is a suitcase boom box powered by a 12 volt rechargable battery... I have a little bit of experience in this area from building a solar powered cooler radio for myself and selling two others just like it. the cooler radio was very simple because I just bought a 200 watt amp, connected it to a jet ski battery with an on/off rocker on the remote, added a solar trickle charger, and wired the speakers up to present a 4 ohm load on the amp.... easy... it lead me here. this is a much bigger step than I thought, lol.

my suitcase boom box could be built the same way, but the battery is really heavy, and the amp takes up a lot of space... these chip amps look like they are light weight, cheaper, and more efficient than the amps I was buying. (the lepai I bought to test speakers from the salvation army sounds wonderful) I thought by building these chip amps I could cut down on the weight of the suitcase, save space inside, and make the audio quality the best it can be (for a suit case)

when I started digging around at 41hz.com I saw how complicated these these can be and that most of them would not supply the watts I needed with a 12 volt dc power supply.

after I read your message I saw those pipe speakers, which I built in 30 minutes and tested with my lepai. they sounded great. I would like to build a small amp to run them with and put it in a case that matches the pipes, one that plugs into the wall. I would like to give them to a friend of mine for his birthday. I thought a smaller chip would be good practice before I build a larger one for the suitcase stereo.

I have a soldering iron and a multimeter I bought for building the cooler radios. I also have a couple different saws and power drills from when I built my own slilts, lol.

I guess I would like you to help me find a suitable amp kit to power four 8 ohm speakers...
(1) 10 inch sub 70w rms
(2) 5 inch sealed back midrange drivers 50 watts rms
(1) 2 inch tweeter rated 40 watts rms
powered by a SLA 12 volt battery that can play reasonably loud.

I would also like for you to recommend a beginners amp kit, one I could practice on that would power two hivi b3n 3" speakers if I build it right. I have $400 available from selling the cooler radios. failure only makes me more motivated.
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Old 13th July 2012, 10:37 PM   #12
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Join Date: Feb 2011
o, now it sounds a lot more detailed.

You know, the verry first step along a path is the most important.
prior any design, the goal must be declared, so is the limitations.

So first of all, we should inspect what load are we going to drive with the amplifier.
it is a rather good practice to first design the cabinet, and use a simulation tool like
LinearTeam
winisd is not the most accurate one, but it is more than sufficient to estimate what output power the amplifier needs to deliver, by showing the excursion at a given input for the driver.
cone excursion limits power handling of a speaker, among many others.
allso worth to check out the specs of the drivers You intend to use.

I give You a real life example why. At this moment i drive a pair of 3 way speakers with 8" bass drivers, and my amp allso runs from 12 volts. And its an 8 ohm load.
it gives us.. roughly 10 volts at verry best output voltage, now we divide this with our 8 ohm load. Equals to 1.25 A current. Voltage multiplied by current yields power. That is, 12,5 watt at verry best. I actualy never turn it over half power, as it is sufficient for the room (6 by 4 meters), and yields more than reasonable loudnes.

You should prehaps link the drivers You intend to use, it may well happen that a similar few watts worth of amp will be more than enough to do the job.

Allso, if weight is an issue for a prtable music box, one can resort to smaller rechargable battery packs. Gives a bit of freedom on voltgae level used Most automotive IC can handle 16-17 volt input without problems, while the datasheets only show 13.5 or 14.4 volt supply characteristics.
Why it is important? well.. first of all, if my amp would have a supply of 16 volts, then it might have an output of 12-13 volts instead of 9-10 volts.
Let us redo the calculation based on this.
12 volt output, divided by 8 ohm yields 1,5 A current, multiplyed by 12 volts yields 18 watts.
And that is a verry reasonable and realistic figure.
It can be verry loud, depending on what speakers are in use

For now, let us turn back to the small HIVI b3n 3" speakers.
I have to admit it is an excellent choice, cheap spekaer for a fun little project.
Madisound Speaker Store
If i guess wright this is the speaker mentioned.
Given the data, after the simulation with winisd it seems it will not handle more than like.. 6-8 watts. That is good news, but if You ask me even less will drive it quite well.
So lets get down to business.
I personaly dislike "kits".
If its diy, then let it be DIY, one does not learn a lot of designing from soldering stuff to a premade board.

The amplifier chip i 99% of time advise to use is tda1557q.
http://www.datasheetcatalog.org/data...s/TDA1557Q.pdf
it won't get any simpler than that.
But will it blend?
Well, i would realy advice You to build this amp,
and abuse it.
Try it with some big speakers if You have any.
You will be surprised what can it do.
This is a good way to "dispell" the plauge of marketing and huge numbers printed on everything, stating 10-20 Kw output power for a portable mp3 player does indeed kills the ability or proper judgement of power.

soo.. what does the chip include?
actualy it has 4 little amplifiers in one IC. They are bridged into 2 amplifiers.
And requires minimum number of parts to "bring to life", while it can be tuned up with just a handfull of more parts.
Ont thing to keep in mind.
Page 5 of the datasheet shows limitations.
Maximum supply voltage must not go over 18 volts. And we should stick to it.
None operating supply voltage must be less than 30 volts.
This is important, say.. many wall plugg adapters nowdays are switch mode supplys.
Many of those, when turned on have a big fat ripple in the voltage, many times simply killing this IC. So battery operation, on non-switching powersupply is the one it likes.
(traffo if You like)

Lets take a look at a basic schematic of how to build this into an amplifier.

Click the image to open in full size.

C1, and its pair C3 are responsible to block DC from the inputs of the amplifer.
A larger value will yield better ability to blay bass.
Caps reactance depends on freqvency.
Xc = 1/ (2 * π * f * C)
where Xc is the capacitive reactance, unit is Ohm.
f is freqvency
and C is the capacity of the capacitor in Farads.

page 7 of IC datsheet reveals input impedance of the amplifier to be close to 15 K ohm.

The capacitor and the input impedance of the amplifer form a voltage divider.
Voltage divider - Wikipedia, the free encyclopedia
The article will explain how will it influence the characteristics of deep sound reproduction. Excell is Your friend, if You like You can plot the response curve and play with capacitor values.

Tipical value is shown at datasheet page 8.
That is 270 nF.
My suggestion is 470 nF.
The type of capacitor to use is non-polarised.
Foil type, that is.
These capacitors have a voltage rating, but it is now not realy important.
The reason is simple, this component is used at the input side, so input voltage level it will recive. Usualy that is not more than 1 volt, and so, any capacitor will do.

C2, and its twin sister, C4 are to prevent the amplifier to act as a radio reciver, by filtering the input.
220 pF value will be enough.
The bigger it is, the more of the high freqvency will be cut.
Ceramic capacitors are best used here.


C5 is the powersupply bypass capacitor.
It should be a polarised electrolit capacitor.
The value should be something from 3300 uF or more.
Higher value does not hurt, but anything over 2x bigger will make no difference.
Voltgae rating must be higher than powersupply voltage.
My advice would be 25 volt rating.
Pay attention to the polarity.

C6 is the capacitor responsible for amplifier stability.
It may even work without it, but it should allways be used with chip amps.
It is there to prevent oscillation.
The value for this capacitor is shown on page 8 of the datasheet.
100 nF, foil capacitor is to be used here.
Notice, it must be as close to the IC as possible, to function properly.

The schematic i attached shows the exact wiring.
Question may arise where to get a PCB for this.
Well, nowhere. Just simply do an old fashion point to point soldering.
Mount the IC on a heatsink before doing anything else, and identify pin 1.
When soldering to the leads of the chip, make sure You allow it to cool down after eatch soldering. Unlikely, but if You keep soldering one lead after a nother, You can actually fry the poor thing..

Sw1
togles the mute /play state of the amp. IF, the switch is open, then there is no sound comming from the amp. If it is closed, then You have sound.

As for powersupply, even a 9 volt battery will do.
And for testing, You should use one.
Click the image to open in full size.

one like this will do for sure.

Heatsink may be difficult to find, but if You have acces to any dead electronic stuff You can salvage one for free. Say.. dead Pc psu's are not hard to find for free, and is an excellent source of wires, and heatsinks.

For soldering properly, do purchase some flux.
Ordinary cheapoo zinkchloride solution will do more than just fine.

When testing the circuit make sure that:
1. Use a battery. its forgiving of sorts.
2. You will hear a "thump" when You turn the amplifier on. Later on we will learn how to fix that with additional circuitry.
3. Whatever source You use, be it a computer of an mp3 player, make sure to set it to the lowest level first. Otherwise make sure You are prepared for a hearth attack. The 9 volt battery does not provide enough voltage to keep the amp from clipping, it will happen if it has to play full volume. Reducing the input voltgae (reducing the output of the source by setting it to low level) will prevent this. On the otherhand it will be pretty loud anyways.
4. Use an inexpensible little speaker for the first tests.
5. When using with bigger speakers, amke sure You check on the temperature of the IC, it may get hot. In that case get a bigger heatsink.


Prior any purchase link the product, so we can verify it.

waiting for reply.
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Old 14th July 2012, 11:11 AM   #13
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okay, I want to build an amp using the TDA1557Q. those schematics look the least frightening of all that I have seen so far. because I don't really know how to read schematics...... yet. right now, looking at that data sheet, I have no clue what to purchase to make that amp I have a wedding to shoot tomorrow. so give me three days to research at the library and I will return here with links to the electronic components I will need to build this amp. after you approve of my links I will purchase the items and try to build my first amp

is there a site you would suggest for purchasing the IC and other components, or will I have to order from different sites? I live in Starkville Mississippi. purchasing them in store is not an option, lol.

also, thank you for your thorough and detailed reply. you have been really helpful and inspiring. I think for right now I'm going to focus on building this amp.

Last edited by iggy18; 14th July 2012 at 11:20 AM.
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Old 14th July 2012, 11:24 AM   #14
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that is a good idea, i must say
I will list here the components.
You can get them at any online or other electronics shop, they are verry widely used simple things.
And it is allso a verry low cost project.
If you can manage to solder 2 wires, then You will allso manage to make the amp.


The stuff You need:
1x TDA1557Q ic.
1x 100 nF capacitor, non polarised
1x 3300 uF 25 V elco capacitor
2x 470 nF capacitor, non polarised
2x 220 pF capacitor, ceramic.
some wires, should be as thick as the ones You see coming from computer powersupplys to HDD for example.
a stereo jack plug
1x 9 volt battery
dunno its english name :
Click the image to open in full size.

A simple on-off switch, like this :
Click the image to open in full size.

and some solder flux.

Basicly this will blend into a reasonably powerfull amplifier.
You did hear car radios in Your life, this IC was quite/is quite commonly used in them.
And we can make it more powerfull than that.
A lot more
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Old 14th July 2012, 01:25 PM   #15
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Join Date: Jul 2012
hi,
i am not a professional, but i suggest that this link can help you :
Circuit Stereo Preamplifier With IC TDA1524A – Tone Control Unit – Bass Treble volume control, channel balance and loudness contour | Xtronic Free Electronic Circuits and Informations
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Old 14th July 2012, 04:46 PM   #16
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not bad, but probably a simple passive EQ and a volume pot will be more than sufficient for this project.
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Old 14th July 2012, 06:12 PM   #17
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Location: S.England
Thought of using lithium batteries for the supply instead of (I assume) lead acids? Just a thought.

A
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Old 14th July 2012, 09:02 PM   #18
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hmm.. not a bad idea, a minimalistic float charger and simple relay logic can recharge the thing while its off, and more than probably it would have a decent play time with even a small battery.
at least a battery IS dc at its best. no ground loops, and sortha stuff.

but we should first wait for iggy to build the amp it self, and run it on a single 9v battery first.
the rest can wait i guess
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Old 16th July 2012, 05:48 PM   #19
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when looking for these capacitors, should should all of them rated for 25 volts?
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Old 16th July 2012, 08:24 PM   #20
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3300 uF must be 25v or higher. Higher will not help, lower will simply blow up

capacitors 'round the nF size and less are usualy rated for voltage far exceeding Our demands.


If you link the onlne store (or the store's price list You have nearby, if You have any) I will gladly help You pick the right parts.

Maybe i would pick a few extra things that can be handy in the long run, within a 5 dollar budget. Realy, just some resistors and stuff.
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