12v amplifier?

[mr.z]

Hi all, first posting here..


I'll get right to it..

What i'm after is an amplifier (for cd player/md/mp3 e.t.c.) that will run off a 12/14(ish) power supply (off a motorcycle power supply)

All the ones out on the market are either absoloute rubbish or massively overpriced (

[audioguru]

Hi Mr. Z,
Welcome to our forum. ;D
There are many medium-power stereo amp ICs for cars, but they have umpteen million pins, therefore need a complicated pcb.

The TDA2005M is a mono 12W to 15W into 4 ohms (it is rated for 20W under ideal conditions) amp IC for cars that has only 11 pins. Its datasheet shows a simple schematic, parts list and pcb. You can copy the pcb onto stripboard or perf board and just make two of them, one for each channel. Use a finned heatsink on each to keep them cool. The datasheet is here: http://www.st.com/stonline/products/literature/ds/1451.pdf
;D

[mr.z]

Hi audio guru, thanks very much for the quick reply...

To be honest i dont think 15watt will quite cut it..

On a test run i fitted a 10watt head unit, even at full blast it was bearly audable over 30mph :( (a real shame as it was working great appart from that)

Hein Gericke (good motorcycle gear company) sell 15watt amps and speekers, ive been told they aren't particuarly great for the same reason as the 10watt HU

Got a 40watt head unit but its got a key code lock on it so can't use it... :-\

This

http://www.aerostich.com/catalog/US/Mini-Stereo-Amp-p-17536.html

Would be ideal, but too expensive + i'm in the uk, so it would work out @

[audioguru]

The mini-expensive amplifier uses the same ICs that I recommended. 32W continuous power, is 16W per channel when the output is horribly clipped, it is only 14W just before clipping. Clipping occurs when an amplifier's output level reaches the supply voltage and is square waves. A square wave sounds awful but has twice the power of a wave that isn't clipped. "Peak" or "Maximum" power is double the real power of an amplifier.

All modern car radios have 14W per channel into a 4 ohm speaker, operated at low distortion just below clipping. Most are rated at 25W "maximum" per channel, 200W for the radio with 4 channels. Its total real power output is actually less than 60W.

High-power car amps are very different. They use a high current voltage stepup inverter to provide their "real" monster amplifiers with 72V or higher.

Speaker efficiency has an enormous effect on loudness. An efficient speaker on a 10W amp would sound like an ordinary speaker with a 100W amplifier.

Make the TDA2005M amp with stripboard or perf board and just copy the pcb with wires. It is a simple amp. Then get some efficient 4 ohm speakers. I'm glad you're in the UK so I won't hear you cummin'. ;D

[mr.z]

ahhh now i'm understanding allot more!

Wattage "power" is allways missleading i suppose, dosn't really mean all that much in terms of volume.. (like mHz in processors means bugger all just a rough indicator)

Loud isn't massivly important to me, but to go over the background noise it needs to be beefy (like driveing with your windows open, then put a helmet on and stick your head out the window ;) ) so its going to be full volume probably half the time..

Apparently i can get hold of these chips pretty easy, not massively pricey either..

I'm going to be pretty limited as far as speeker choice, to have them out in the open (important really) they will have to be similar to these


http://www.yachtbits.com/gme_audio/gme_spk530w_stereo_box_speakers.php

Would the TDA2005M based amp drive these well enough to get effieicnt sound?


Eventually i'd like to have waterproof volume/mute controlls and a volume boost linked to a digital tachmeter (progressively louder to 10krpm) is that feesable with a simple beastie like this one?


Very much appreciate the help, i understamd noobish question like this much be hard work  :-[

[audioguru]

ahhh now i'm understanding allot more!

Wattage "power" is allways missleading i suppose, dosn't really mean all that much in terms of volume.

I call the missleading ratings for amps and speakers "Whats" instead of Watts.
Years ago, the Sears catalog had an asterisk  beside all their Stereo Consoles. The description read: "Our 240W stereo consoles actually produce 4W per channel into 8 ohm speakers from 20 cycles to 20k cycles per second continuously, with low distortion". They got busted for false advertising and the stereos did produce 240W but only into a dead short only for a microsecond before they blew-up!
You need to read all the data to find the real power from amps and speakers.

I'm going to be pretty limited as far as speeker choice, to have them out in the open (important really) they will have to be similar to these...

They are tiny 3" speakers similar to ones in some headphones and clock radios, seem cheap but very expensive and are rated in "Music Power" like Sears did in their catalog. I don't think there is much background noise on a sailboat.

I worked for TOA, a large international Japanese PA equipment manufacturer. They have many waterproof (outdoor) very efficient various-quality (price) speakers. A few might be small enough for your motorcycle. Talk to a salesman of one of their dealers near the end of a month near the end of a yearly-quarter and you will get an excellent price. Especially if you tell him you will recommend his stuff to all your friends. Quota, quota, quota! Top salesman award! ;D
I fooled the sales manager when I powered the speakers in the demo room with my home-made little battery powered 7.8W amp. He thought the 200W amp was driving them. 

Would the TDA2005M based amp drive these well enough to get effieicnt sound?

Not those cheap little speakers for sailboats. Efficient speakers would sound awesome with these amps.

Eventually i'd like to have waterproof volume/mute controlls and a volume boost linked to a digital tachmeter (progressively louder to 10krpm) is that feesable with a simple beastie like this one?

The 218 real Watts amp in my car does that. It would be a nice challenge to do.

Very much appreciate the help, i understamd noobish question like this much be hard work

[mr.z]

I've decided to go for it then, the chips are pretty expensive compared to the cost in the states ($10ish each!) so will have to shop about a bit..

Main consideration is cost and size, speekers are going to be hard to find.. so let me check, should i be looking for two 20watt speekers @4/8

[audioguru]

4 ohm speakers will take nearly twice the power of 8 ohm speakers and will be louder.

[chub2]

Hello Guru,

Please help this novice from a remote place.

Is there any simple High power amp circuit which can be used in a car? is there also a simple way to increase the 12v car battery power to run these high power amps?

I have searched everwhere in the internet and it was found that the more powerfull the amplier is, we need higher DC supply input too.

[audioguru]

Hi Chub,
A single ordinary power amplifier IC like a TDA2003 has an output power of about 2W into an 8 ohm speaker at clipping with a 14V supply. Its power is 4.5W into 4 ohms, 6W into 3.2 ohms and 8W into 2 ohms.

A power amplifier IC like the TDA2005 is bridged with two amplifiers and has an output power of about 15W into a 4 ohm speaker at clipping when it has a 14V supply. It can't drive a lower impedance.

Philips has a power amplifier IC that is bridged for 15W output into 4 ohms, but also has a voltage doubler circuit so can make an output of about 50W into 4 ohms when needed.
It automatically switches its supply from 14V to 28V on demand in order to stay fairly cool.

Real high power amplifiers for cars have a powerful amplifier that uses a supply voltage of about 70V and has a powerful voltage stepup power supply circuit.

A high power amplifier for cars is not simple.

[audioguru]

Hi Sasi,
The TDA7240 is better than the TDA2005 even though the spec's are about the same because the TDA7240 has less number of pins and has a pcb layout in the datasheet.

Thanks for the big long list of TDA amplifier ICs. I noticed that it missed out the TDA2005.

I notice that most of these amp ICs have a very high voltage gain of from 100 (40dB) to 316 (50dB). They would have less distortion if they had more negative feedback which reduces the gain. But the distortion is accepably low as it is now and maybe they would oscillate if they had more feedback.