My 1st car amplifier!..engine whine problem.

[deepanger]

hi all,
ive just built a 4x22watt car amplifier based on TDA1554Q amp.
i use 2 of them to make a 22watt x 4channels amp, each one is
totally separated from the other, so each has its own filter cap.
ouputs...etc

http://www.aaroncake.net/circuits/amp20w.htm

its just so simple amp. to drive 2 coaxials and 2 tweeters..
the input is from a battery powered discman,
the prob. is iget that engine whine when car is running,, its
really annoying and mess the whole thing!
am powering the amp. with a 10 or 8gauge "dont exactly remember" power cable, its more than enough as the max. current demand for the whole amp. is about 10A, i tried many diff.
ground locations in the car but nothing works ,the same prob.
the power and the speaker cables arent close and running in diff.
directions so itsnt making probs.

so anything to do about it? try to increase the power filter capacitance or doesnt has effects?! ,am ready to build any good
noise filter if its the only solution...

so i really need any help in this as much as anyone can!
thanks alot..

[nw_avphile]

It's very likely a ground loop. You need to find out where your car stereo is grounded and ground the amp at the same place. Even a few feet away will create whine. It can be difficult to sort the grounds out, but once you do it almost always gets rid of the noise.

You might also try isolation transformers (ground loop isolators) between your car stereo and the inputs to the power amplifier. The people that sell car stereo accessories sell them. MCM Electronics here in the USA has them for about $9.

Some other options are to try to get rid of the alternator noise at the source--the alternator. Some people put filters or large capacitors (10,000uf 25v) right at the alternator output terminal. But be careful of creating a fire hazard if there is a short or failure. But this usually only reduces the whine and never gets rid of it completely.

Higher power car amps are less prone to this problem because they have a DC-DC converter in their power supply so the amplifier ground can be somewhat isolated from the car's 12 volt ground. But in a bridged amplifier like you're using, you have no isolation.

[Matttcattt]

couldnt you just use a seperate battery?

[deepanger]

Originally posted by nw_avphile
It's very likely a ground loop. You need to find out where your car stereo is grounded and ground the amp at the same place. Even a few feet away will create whine. It can be difficult to sort the grounds out, but once you do it almost always gets rid of the noise.

You might also try isolation transformers (ground loop isolators) between your car stereo and the inputs to the power amplifier. The people that sell car stereo accessories sell them. MCM Electronics here in the USA has them for about $9.

Some other options are to try to get rid of the alternator noise at the source--the alternator. Some people put filters or large capacitors (10,000uf 25v) right at the alternator output terminal. But be careful of creating a fire hazard if there is a short or failure. But this usually only reduces the whine and never gets rid of it completely.

Higher power car amps are less prone to this problem because they have a DC-DC converter in their power supply so the amplifier ground can be somewhat isolated from the car's 12 volt ground. But in a bridged amplifier like you're using, you have no isolation.

idont have a car stereo right now,, i use my battery powered discman as an input to the amplifier, i tried to power ground the amp. to diff. locations in the car but with no use...

anyway, ive a 2x 10,000uF 25V. caps right here, but can i use them b4 the power input of the amp. instead of putting them after the alternator output?

and what about using or even building a good noise filter? dont know any about em but can learn!

thanks in advance..

[HDTVman]

Do you have the +12 input connected to the battery or some where else? It sounds like you may have alternator noise. The best way to get rid of it is to connect both + and ground of the amp directly to the battery. If the noise is still there add a choke to the + wire as close to the amp as possible. You will need a power switch to turn the amp on and off.

Good luck
BZ

[deepanger]

Originally posted by HDTVman
Do you have the +12 input connected to the battery or some where else? It sounds like you may have alternator noise. The best way to get rid of it is to connect both + and ground of the amp directly to the battery. If the noise is still there add a choke to the + wire as close to the amp as possible. You will need a power switch to turn the amp on and off.

Good luck
BZ

i already tried many diff. locations for grounding...1st the power cables were connected to the battery + & - terminals, theni tried to ground to a more near points , like where my old HU were grounded, then to one of the doors, seats....etc the same prob.
and the amp. already has a ON/OFF switch...

so any other ideas?

[Diode]

Deep Anger,

Yes, you need to build a filter. It is the same filter as a crossover filter. I don't know the exact values. From the battery wire (before your amp) an inductor. Then a big capacitor from + to - then a .1uF cap in parallel with that. Then another inductor inline with the ground, followed by a .1uF cap across the + and - then a big cap from + to - make these in series as the position of the inductors with the caps is important. If you want, experiment with a low pass filter, as in a speaker box. A simple inductor (iron core) and a capacitor from coil to ground. With 10,000uF caps, the inductor can be fairly small, possibly air core. Experiment and see! Put one on each power lead at different times, you may find the noise on the ground lead! you may want to put a filter on both of the leads. Are you using batteries or power for the diskman? That is probably where the loop is being formed. Hook up the amp, by itself and see if the niose goes away or goes down in volume. If so, the diskman is the problem. If not, filter the amp.

Hope this helps,

Chris

[zx3chris]

since you are only drawing 10a you can just make a circuit usign a 12v regulator to regulate the 14v down to 12. this should reduce the noise quite a bit. an independant power source will always solve the problem, and in other cars ive worked in (that had an inverter as well), we would just use ac-dc wall transformers laying around and use them...always worked

good luck

-chris

[nw_avphile]

You can probably buy a ready-made noise filter (made in China) much cheaper than you could build one. They make them in various ratings up to at least 40 amps which is more than you need for your amp.

It might also be you have a grounding problem within the amplifier. If the grounding is done wrong it will destroy something known as the Common Mode Rejection of the amplifer. This is basically the amp's ability to reject power supply noise (like alternator whine).

It's very important to use a "star" ground for all the critical grounds. Especially critical are the input grounds, any of the input circuitry grounds, and the feedback loop grounds (i.e. the dc blocking capacitor to ground in the feedback loop). All of those grounds should tie to a common SINGLE point like the center of a "*".

Grounding can be tricky and sometimes it's a matter of trial and error to find the problem.

[Matttcattt]

would connecting the CD player ground to the car battery ground help?