Beginner help!

Zenolijo

Member
2010-11-20 3:55 pm
Hope youre not tired of beginners, cause heres a new thread!

Im new to DIY but ive built a boombox just a month ago
I built it on a 12v 12ah battery, a car radio and two GAS Alpha 6936 speakers.
So its a rather small boombox.
Ill add a pic l8er if u want


First of all, i got a question if i've got it all right how a amp works.
Imageshack - testmo.png

This is how i THINK a amp works, im wondering if this is correct or if im wrong somewhere or maybe everywhere >.<



Lets get to the new project im starting!
This is going to be almost the same as the boombox but smaller and some modifications.

I have already bought a pair of Sony CS-F1026SE Speakers
You can find them here XS-F1026SE (XSF1026SE) : Car audio : Sony

I have also bought an very very cheap amplifier, which i need your help to upgrade to get better. I will get the amp very soon, the other times i ordered from dealextreme the deliveries takes around 2-3 weeks. I know the deliveries are horribly slow but you cant say no to free worldwide delivery and cheap prices!
DealExtreme: $18.54 Hi-Fi Stereo Amplifier with Remote Control for Car/Motorcycle (SD/MMC/USB)

I want to upgrade this amp. I wonder if i can change the 2x TA8201AK thats already inside to something stronger, maybe 30 or 40w if thats available for chips.
I can do this without changing the pre-amp right?


I am thinking of buying a 7,2Ah 12v lead acid battery, the same as last time but 7,2Ah instead of 12Ah. Dont want it too heavy.


Thanks for the help!
 

Zenolijo

Member
2010-11-20 3:55 pm
I got my amp now!
As i thought, it would be a horrible quality on the amp.
One of the amp chips weren't attatched, i've tried to attach it again but i failed, ill post pics later.
On the one amp chip that works, ive adding some cooling paste, it became hot even on half the volume before, but now its better :)

I'll be posting pics and more detailed info in the weekend when i have some more time for fixing it :)
 
If it did not work, you should have sent it back instead of trying to repair it. Now, if you don't get it to work, you have lost the warranty and the money.

The output power is typically limited by the supply voltage and the load impedance. With 12 V power supply you cannot expect much more than those 18 W into 4 Ohm and that is already with high distortion.

If the TA8201 sounds bad, that has probably more to do with the speakers and/or the application than with the IC itself.
 
To get higher power, you need a higher supply voltage. There's two ways to do this:
a) A higher voltage battery or more batteries.
b) A switch-mode power supply that converts 12V to a much higher voltage.

If you want to use a small battery to save weight, then high power is probably not a good idea as the battery will go flat fast. To play louder, it would be a better idea to use more efficient loudspeakers.

The Sony CS-F1026SE is not very efficient. It is only rated at 85dB/1m/1W.
A speaker rated at 91dB/1m/1W will play as loud with 10W as the Sony does with 40W.
 

Zenolijo

Member
2010-11-20 3:55 pm
If it did not work, you should have sent it back instead of trying to repair it. Now, if you don't get it to work, you have lost the warranty and the money.

The output power is typically limited by the supply voltage and the load impedance. With 12 V power supply you cannot expect much more than those 18 W into 4 Ohm and that is already with high distortion.

If the TA8201 sounds bad, that has probably more to do with the speakers and/or the application than with the IC itself.

I fixed the chip today with a friend, works good actually.
Both speakers sounds bad but im very sure about that its because of my weak power supply, i have a 600mw adapter connected to the amp.
Will buy another one and fix the connection to the battery.
How many ampere do i need, something between 3 and 5A?

To get higher power, you need a higher supply voltage. There's two ways to do this:
a) A higher voltage battery or more batteries.
b) A switch-mode power supply that converts 12V to a much higher voltage.

If you want to use a small battery to save weight, then high power is probably not a good idea as the battery will go flat fast. To play louder, it would be a better idea to use more efficient loudspeakers.

The Sony CS-F1026SE is not very efficient. It is only rated at 85dB/1m/1W.
A speaker rated at 91dB/1m/1W will play as loud with 10W as the Sony does with 40W.

Didn't know there was 5" speakers with 91dB/w :O
Too late buying new, its been more than 2 weeks since i bought them :(
And my amp doesnt support higher voltage so i cant actually do much.
Havn't ever been thinking before about that i will get more W from the amp if its running higher voltages.
Im pretty sure im going to build an amp when this project is done.
Do you need anything else for a amp than a amp, pre-amp, switch-mode power supply, volume controller and some cooling for a amp to work?
 
How many ampere do i need, something between 3 and 5A?

Depends on how loud you want to listen. The TA8201 has a peak output current of 9 A, but it can only put out what is fed in.

Didn't know there was 5" speakers with 91dB
There are, if you either don't need bass or put them into a horn.

And my amp doesnt support higher voltage so i cant actually do much.

The TA8201 can be driven from 18 V nominal DC. Just check whether all other components in the amp withstand that voltage. You may have to replace a few capacitors.

Do you need anything else for a amp than a amp,

No. ;)

pre-amp, switch-mode power supply, volume controller and some cooling for a amp to work?

You can skip the preamp. You can use a conventional power supply instead of an SMPS. You need components that you did not list although you are probably aware of them. Case, feet for the case, screws, cables, connectors, wires, switches for power and sources, knobs for the switches and the volume control potentiometer, fuses with holders, a power indicator, a few spare components just in case, some knowledge about the functions of each component, soldering skills, a multimeter, very recommendable is a light bulb with socket to build yourself a light bulb tester, etc.
 

Zenolijo

Member
2010-11-20 3:55 pm
Depends on how loud you want to listen. The TA8201 has a peak output current of 9 A, but it can only put out what is fed in.

There are, if you either don't need bass or put them into a horn.

The TA8201 can be driven from 18 V nominal DC. Just check whether all other components in the amp withstand that voltage. You may have to replace a few capacitors.

No. ;)

You can skip the preamp. You can use a conventional power supply instead of an SMPS. You need components that you did not list although you are probably aware of them. Case, feet for the case, screws, cables, connectors, wires, switches for power and sources, knobs for the switches and the volume control potentiometer, fuses with holders, a power indicator, a few spare components just in case, some knowledge about the functions of each component, soldering skills, a multimeter, very recommendable is a light bulb with socket to build yourself a light bulb tester, etc.

Thanks for all the help! :)
But if i run the amp on 12v 9A i get 108w and that seems like alot of more power that the specs says.
On the back of my amp it says DC12V 5A. Thats 60w and i guess thats the peak of what the amp handles. Doesn't really sound right that it's possible to run it on 9A. I guess that the TA8201 can handle more than the rest of the amp can.
So if i run the amp on 1A 18 v i will get 12w but if i run the amp on 12v 1A i will get only 12w?
Does it still survive up to 9A even if its on 18V instead? 9A x 18V = 162w so its a rather big difference.

Can i in some way see what capacitors i need to change?

Can u send some examples on speakers with 91dB/w?
I want to see the other specs on them too.
I bought mine for 300 swe crowns that is about 30€, is there any big difference on the price?
 
You do not get the voltage times the current of the supply as output power. It's more complicated than that.

Use V * V / R = P to calculate the power for a particular voltage.

So if you have 8 ohm speakers, you would get approximately 12V*12V / 8R = 18W *IF* you supply at least enough current.

18W / 12V = 1.5A, but you need more than that because the circuit is no where near 100% efficient. You want a power supply that is the correct voltage for the output power you want, and has more than enough current to provide that power.

To provide 60W into 8R you need 60W * 8R = V * V. So your voltage would have to be 22V. And you would need a fair bit more than 60W / 22V = 2.7A to provide that power.

To make matters even more complicated, most amp chips can't swing all the way to the voltage rails, they max out between 4 and 6 volts from the supply voltage. So to realistically get 60W into 8 ohms, you need about 30V power supply capable of around 4A.
 
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Can u send some examples on speakers with 91dB/w?
I want to see the other specs on them too.

Of 5" speakers with 91 dB/W @ 1 m?

The Visaton BG13P is specified with 92 dB/W @ 1 m. It is a full-range speaker that sells for 12 €. Resonant frequency is 168 Hz, so no bass to be expected.

The Beyma 5G40Nd has 93 dB/W @ 1 m. Beyma describes it as low-mid transducer, but with a resonant frequency at 110 Hz, you should not expect it to go very low either. Price is around 80 €.

Then there is the Celestion TF0510, fs = 106 Hz, ~26 €.

What these drivers have in common is, they are intended for professional use (guitar speakers, line arrays, small monitors), there is not much going on in the bass region, the high sensitivities are usually reached at high frequencies only and their frequency responses are anything but flat.
 

Zenolijo

Member
2010-11-20 3:55 pm
You do not get the voltage times the current of the supply as output power. It's more complicated than that.

Use V * V / R = P to calculate the power for a particular voltage.

So if you have 8 ohm speakers, you would get approximately 12V*12V / 8R = 18W *IF* you supply at least enough current.

18W / 12V = 1.5A, but you need more than that because the circuit is no where near 100% efficient. You want a power supply that is the correct voltage for the output power you want, and has more than enough current to provide that power.

To provide 60W into 8R you need 60W * 8R = V * V. So your voltage would have to be 22V. And you would need a fair bit more than 60W / 22V = 2.7A to provide that power.

To make matters even more complicated, most amp chips can't swing all the way to the voltage rails, they max out between 4 and 6 volts from the supply voltage. So to realistically get 60W into 8 ohms, you need about 30V power supply capable of around 4A.

Oh, i didn't know how the resistance worked at all, just knew it made higher power but not exactly how much.
so if i have a 12v amp at 4 Ohm i can play 12*12/4=36w
36/12=3A?
I think i got 8Ohm on my amp but can i in some way like upgrade that to 4Ohm resistance without anything in the amp will break?

Would be totally awsome but i guess that wont work >.<

Of 5" speakers with 91 dB/W @ 1 m?

The Visaton BG13P is specified with 92 dB/W @ 1 m. It is a full-range speaker that sells for 12 €. Resonant frequency is 168 Hz, so no bass to be expected.

The Beyma 5G40Nd has 93 dB/W @ 1 m. Beyma describes it as low-mid transducer, but with a resonant frequency at 110 Hz, you should not expect it to go very low either. Price is around 80 €.

Then there is the Celestion TF0510, fs = 106 Hz, ~26 €.

What these drivers have in common is, they are intended for professional use (guitar speakers, line arrays, small monitors), there is not much going on in the bass region, the high sensitivities are usually reached at high frequencies only and their frequency responses are anything but flat.

I'd like at least 80Hz on my speaker and a pretty cheap one.
Still impressing those with Visaton BG13P.
92dB/w @ 1m is great for only 12€
Someone told me that the volume is doubled up at every 3dB added, is that true?
Or maybe could i run one bass speaker and one tremble speaker and get a higher sound? My EQ controller with bass and tremble on my amp is great, if i max it i get no bass at all, if i do the same on my bass it's the same.
 
so if i have a 12v amp at 4 Ohm i can play 12*12/4=36w
36/12=3A?

No. The 12 V are DC. Music is AC and the effective AC voltage is 0,707 times the peak voltage. With 12 V DC you get ~8,5 V AC which leads to ~18 W and ~2,1 A with a 4 Ohm load. And then you still have to reduce that by the losses.

I think i got 8Ohm on my amp but can i in some way like upgrade that to 4Ohm resistance without anything in the amp will break?

You should check the datasheet. The TA8201 aka TA8205 is specified for 4 Ohm loads. In general you need to increase the heatsink size and sometimes have to reduce the supply voltage to make an amplifier work into a lower impedance.

Someone told me that the volume is doubled up at every 3dB added, is that true?

The other way round. Double the power leads to 3 dB more. But it takes 5-10 dB depending on the frequency to give the impression of double the volume.

Or maybe could i run one bass speaker and one tremble speaker and get a higher sound?

You may get a better sound, because each driver can be used in the frequency range where it works best. You won't increase the efficiency though.
 

Zenolijo

Member
2010-11-20 3:55 pm
No. The 12 V are DC. Music is AC and the effective AC voltage is 0,707 times the peak voltage. With 12 V DC you get ~8,5 V AC which leads to ~18 W and ~2,1 A with a 4 Ohm load. And then you still have to reduce that by the losses.

Actually, my amp doesnt have a heatsink at all and the chassi is made of aluminum.
I've added cooling paste myself though, became very hot before when i used it.
I can replace a heatsink with a cooler right?
Because i can rather easily get a 12V cooler for only 4€ :)

Still no awnser how to make it 4Ohm and what capacitors i need to change if i make the input power 18V

You should check the datasheet. The TA8201 aka TA8205 is specified for 4 Ohm loads. In general you need to increase the heatsink size and sometimes have to reduce the supply voltage to make an amplifier work into a lower impedance.

I have already seen those sheets, but thanks anyway :)

The other way round. Double the power leads to 3 dB more. But it takes 5-10 dB depending on the frequency to give the impression of double the volume.

Ah, i thought it was a little wierd that it was just 3dB >.<

Then its much more important with a good dB/[email protected] if you only get 3dB for every double up of the power.

You may get a better sound, because each driver can be used in the frequency range where it works best. You won't increase the efficiency though.

Ok, then it's still better cause you get better sound for the same price.
 
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Yes, the impedance makes a difference. The lower the impedance in Ohms, the more current will flow at a given voltage. More current means more heat. So if you connect 4 Ohm speakers instead of 8 Ohm speakers you should make sure that the heatsink is big enough and that the amplifier can deliver the increased current. If either is not the case, you have to use a lower supply voltage.

I don't know what a 2-16 Ohm speaker is. Normally a speaker has a nominal impedance, e. g. 4, 6 or 8 Ohm. The impedance can go down to 80 % of the nominal value at certain frequencies.

You can run your amp on 18 V with 8 Ohm speakers.

With 4 Ohm speakers and 18 V you will get a worst case heat dissipation of ~35 W. With 2 Ohm speakers and 18 V you will get ~68 W. The TA8201 can dissipate 50 W at 25 °C and must be derated above that temperature.
35 W can be dissipated at 62,5 °C. With the IC's thermal resistance of 1,5 K/W the heatsink must remain below 10 °C without the effect of thermal grease and isolation washers. 68 W can be dissipated at -20 °C which pushes the maximum heatsink temperature to below -122 °C. I believe you won't be able to find heatsinks for that amount of waste heat.