Isolater?

[b/w05]

I think I need an isolater??

Put a new deck, amps and speakers in this winter. Everything sounds good when engine is off. When I turn the engine on it has a "whinning" noise! This whine corresponds higher & lower with RPMs. I also noticed that when I push the button to adjust my Taps, you can hear a clicking noise thru the speakers. You can't really hear when it's turned up loud. I hooked up my fake-a-lake when we installed the last amp and turned the engine on and everything sounded fine. Took the boat to the lake last night and motored out a ways, turned the stereo on and "NOISE"!

Details:

2005 22i
Pioneer 780 deck
4 Kenwood cabin speakers, Rockfordfosgate T400-4 amp
Focal tower speakers, Clarion 200w amp
10" JL sub, JL amp

2 batteries, w/perko type switch.

[philwsailz]

Make sure all of your RCA cables are completely connected. If that does not take care of it, consider moving the radio ground wire to the negative terminal of your largest amplifier. That will help some, or a lot.

Clicking when energizing accessories is a pretty common problem. A solution I like is to use a couple of capacitors in the radio power leads, wired across from red to black, and also yellow to black. See the pic below. The cap is a 50-volt 2200 uF cap; available on-line at radio shack...

Be sure to finish the installation; the pic shows leads just twisted on!!! Take the time to solder or crimp, and then be sure to shrink wrap the cap, or do something to insulate and isolate the connections.

[chpthril]

How/where is the head unit and amp getting power and ground? This is where we need to start as that is where the noise is probably coming from. An Isolator is nothing more than a lazy mans Perko, so it wont help here.

Also check where your signal cables are run. They can also pick up EMI/noise if they are running along the power and grounds.

[Domsz06]

you stole my line chpthril!

[spharis]

You could always take the easy way (sometimes unavoidable) out and get an inline filter. Solves the ground loop 90% of the time. Look for a "ground loop isolator" at your favorite store.

[b/w05]

Picked up a couple filters tonight at Stereo King (their recommendation). I'll try it tomorrow.

Thank for the input.

Mark

[spharis]

Yeah, its not a "pro" fix, but it will take care of the issue most of the time, and the end user will never know the difference. They are used ALOT by installers who need to maximise time sent on issues like that.

[evil0ne]

I'm getting noise in the speakers when the blower is on, will one of these filters help for that?

[philwsailz]

I'm getting noise in the speakers when the blower is on, will one of these filters help for that?

My $0.02:

I agree that RCA-style in-line filters do a good job of removing noise from amplifier inputs. I prefer not to use them due to one simple fact: any intentional music signal that has similar characteristics to the noise is inadvertantly removed from the music as well.

More often than not, in trouble-shooting boat stereos for OEM boat manufacturers, we can show that the noise, while ending up in the RCA's is initially in the power wire. Think about your blower; it might be brushless, but regardless, motors work in DC systems by reversing polarity to a coil of wire which is spinning inside the motor. One can often see the effects of the magnetic field being established and collapsing on an oscilloscope. Same thing goes for popping associated with switches, pumps, lights, etc.

You guys remember the little black boxes that used to be on the power wires of stereos that were available 5 or 10 years ago? These usually held a fuse, but they tupically had a little noise filter in there as well; designed to remove the noise from the power wire prior to getting into the stereo. Almost nobody has these on the stereo power wire harnesses anymore; some as a result of better radios and improved technology, some as a result of cost cutting.

The capacitor idea I shared above is as a direct result of my efforts aimed at eliminating popping in the sereo systems for another boat manufacturer. If you take the time to do this mod, and do it as close to the back of the radio as possible, I can almost totally guarantee that you will eliminate all popping and whining noise in your stereo. That is, assuming you really have a reasonably good set of RCA cables...

[spharis]

Phil,
While I agree that those are not the proper way to fix the issue no, removing of any frequencies from the audio signal (a common misconception is that they actually filter the noise areas)....there may be a slight voltage drop, but it will be less than you can pick up without a really good MM. As I am sure you are aware, a ground loop isolator is nothing more than two very very very long coils of wire around a pole(non-boosting transformers). It doesn't filter the audio by design. What happens is the DC signal (the noise) travels into the first transformer and since it cannot pass to the second, it is eliminated.

The little black boxes have made a huge comeback in recent years with the popularity of TFT screens and mini displays, ipod integration, etc. Almost always one on the power wire now. Even so, these are usually the coupled transformer style, or the one I had open yesterday was anyway. I have also seen the cap bleed style in rear screens to help with white noise, and pop.

Now a capacitor fix on the audio leads (not power leads as you have suggested) will remove audio frequencies, and can be tuned to application as well. It is also a very common fix to add these to get a delay in turning on amps or eqs where the units power up before the signal is established. Pop. I have also built DVD screen override circuits using caps to simulate handbrake triggers.


Also guys keep in mind that the cap fix will not solve white noise, alternator noice, whining, etc. Once a cap is fully charged, it is uselesss to the circuit if the circuit continues to recieve a steady amperage. It will only assist to delay the startup time to the component installed behind it while the cap charges up. Ergo, the larger the cap, the longer delay in the component getting power.

[spharis]

One more note, the GLI I am referring install on audio signal leads only (RCAs). If you are getting noise somewhere else, these will not help. Also a little better explanation, I read what I wrote and it can be confusing I guess: The isolator contains a little circuit that seperates the input signal from the output signal to remove the noise.

[philwsailz]

Phil,
While I agree that those are not the proper way to fix the issue no, removing of any frequencies from the audio signal (a common misconception is that they actually filter the noise areas)....there may be a slight voltage drop, but it will be less than you can pick up without a really good MM. As I am sure you are aware, a ground loop isolator is nothing more than two very very very long coils of wire around a pole(non-boosting transformers). It doesn't filter the audio by design. What happens is the DC signal (the noise) travels into the first transformer and since it cannot pass to the second, it is eliminated.


Now a capacitor fix on the audio leads (not power leads as you have suggested) will remove audio frequencies, and can be tuned to application as well. It is also a very common fix to add these to get a delay in turning on amps or eqs where the units power up before the signal is established. Pop. I have also built DVD screen override circuits using caps to simulate handbrake triggers.


Also guys keep in mind that the cap fix will not solve white noise, alternator noice, whining, etc. Once a cap is fully charged, it is uselesss to the circuit if the circuit continues to recieve a steady amperage. It will only assist to delay the startup time to the component installed behind it while the cap charges up. Ergo, the larger the cap, the longer delay in the component getting power.

SP-

Careful...
Are you saying that in-line RCA filters do or do not remove audio in your opinion? My reasoning for the question is this: By nature, DC can have no noise. Connect a 9 volt battery to a speaker, and beyond the initial pop, there is no noise. Audio program material is an AC signal; its voltage changes; i.e. varies both in amplitude, (loud and soft) and in frequency, (pitch). The pop when you connect the battery to a speaker is due to the fact that the voltage applied to the speaker CHANGED from zero to nine volts. Once at nine volts, the speaker is sitting with the cone extended, but it is making no noise. DC has no inherent noise...

The noise being describe in this thread is audible, and since it is audible, it must be able to move a speaker cone back and forth. Since it can move a speaker cone back and forth, it must have a changing voltage, and therefore a frequency. Since it has a frequency, it has an amplitide, and it is not DC.

Now evilOne is describing one of two things, either the pop associated with turning the switch to the blower on, or the operation of the blower itself. The noise is AC hash, caused by slight fluctuations in the voltage on the power wiring, caused either by throwing the switch, or again by the magnetic field in the motor witing turning on an off, while reversing phase several times a second. Several times a second; i.e. it has a frequency.

Now, were the cap shown above wired in SERIES, all of the things you share about the behavior of capacitors would be true. However, the capacitor install I picture above is in PARALLEL with the battery / power supply. It will filter noise, and does a darned good job of it. It will NOT see any amperage moving through it, it will NOT delay the turn on of the device, since the device is not behind it, but "next" to it, just like the battery is "next" to it.

This is the same use for a cap as is on the backside of a diobe-bridge-rectifier; to clean up the voltage, smooth it, and get rid of the AC noise artifacts...


****QUICK EDIT****

I just submitted my reply, and see your new one SP. I think again we are much closer to being on same page than the rest of the guys herer might suspect, based on our "spirited" discussions. Your quick follow up confirms this in my mind. How are ya today?

[spharis]

RCA filters do not remove frequencies by design. Ground loop will cause a hum based on the difference in signal droop at about 50-60Hz. The ground loop isolators will remove it from the RCA line.

It is a decoupled transistor circuit. The DC noise cannot get from the input to the output. It has nothing to do with the signal. The full signal will tranverse the ciruit. Here's a better explanation, taken from bcae1.com.

Function:
Ground loop isolators are used to remove the DC circuit path from the audio shield ground circuit.

Background:
The head unit's preout audio section is referenced to ground (the metal outer chassis of the head unit to be more precise). This means that the audio output's reference is tied to the mounting position of the head unit.
You already know that ALL conductors have resistance. This includes the vehicle's metallic chassis. Any time that you have current flowing through a conductor (which, as you remember, has resistance) you will have a voltage drop across the conductor.
Any accessory (lights electric motors etc...) which are grounded to the body will cause varying voltages across the conductor (the body of the vehicle). If you could measure the voltage from the ground for your amplifier to the ground for the head unit, you would see a very small difference of voltage even though they are both ground. To make matters worse, the alternator produces small pulses which aren't completely filtered out by the battery and/or capacitors. These pulses create noise that varies with engine (and therefore alternator) speed.

Note: This next paragraph will become agonizingly redundant. It is an attempt to make the concept clear to those who are new to car audio.

Ground Loops:
Every piece of car audio equipment has some type of noise canceling circuit on the audio input circuit. These input circuits will, ideally, completely isolate the audio's shield ground from the amplifier's internal connection chassis ground. The amplifier's input shield connection (if properly designed) will have virtually no connection to the amplifier's power ground. It should take the signal from the RCA cable's center conductor, compare the center conductor's signal to the RCA's shield (the reference) and amplify the difference between the two. Remember the voltage generated in the body(voltage drop across the chassis from other electrical accessories)? Well if the amplifier used the ground in the rear of the vehicle (where the amplifier is mounted) as the audio reference instead of the shield ground (which is referenced to ground at the head unit's mounting position) as a reference, the voltage generated through the body would become part of the amplified signal. The amplifier would amplify the difference between the signal on the center conductor of the RCA cable and the amplifier's ground (in the rear of the vehicle). Some manufacturers use poorly designed input circuitry which allows the equipment's power ground to have too much of an influence on the signal (not enough isolation). This causes a small amount of fluctuating DC current to flow through the audio shield which allows noise (from the voltage drop across the chassis) to enter the signal path. The 2 ground paths create a ground loop.

Lame Analogy:
For those of you who are more mechanically inclined, try to think of it as a brake cable for the rear brakes on a bicycle. You know that there's an outer casing and a center cable. If there was no outer casing (only a cable connected to the brake lever). The brakes would work properly only when the handle bars were in precisely the right position (straight ahead for this example). If the handle bars were turned a little to one side (let's say left), the cable would get slack and could not possibly tighten the calipers onto the rear wheel. If the handle bars were turned sufficiently to the right, the cable would tighten and the brakes would be applied no matter whether the brake lever was pulled or not. The brake cable's outer casing acts as a reference for the braking system. If the inner cable at the brake lever end moves 1 inch with reference to the casing, it will do the same thing on the other end (the caliper end of the cable). It does not matter how much the two opposite ends of the cable (as a whole) are moved (with reference to each other). The RCA cable provides a reference along with the signal to make sure that the signal is accurate when it reaches the other end. If you want add a 'ground loop' to the braking system, imagine a stiff rubber band connecting the brake lever to the rear caliper. If you adjusted the brakes to operate properly with the handle bars straight, the braking would not work precisely the same when you turned the bars to either side. The brake cable would dominate the braking operation and the brakes would probably work fairly well, but not perfectly because there would be 2 different forces trying to control the rear caliper. This would form the mechanical version of the ground loop.

Construction:
A ground loop isolator contains an isolation transformer for each channel. The transformers generally have a 1:1 ratio which neither boosts nor cuts the audio level. The audio is magnetically coupled through the transformer's core. Since DC can not flow the transformer, the DC path is cut and the noise is eliminated.

[spharis]

Definition of an isolation transformer.

An isolation transformer is a transformer, often with symmetrical windings, which is used to decouple two circuits. An isolation transformer allows an AC signal or power to be taken from one device and fed into another without electrically connecting the two circuits. Isolation transformers block transmission of DC signals from one circuit to the other, but allow AC signals to pass. They also block interference caused by ground loops. Isolation transformers with electrostatic shields are used for power supplies for sensitive equipment such as computers or laboratory instruments.

[spharis]

On the caps, yeah.....across the power they will help to condition the power, similar to the caps alongside the Northbridge on a motherboard. If they are connected in parallel to a seperate ground, then they will act as a delay circuit for powering off. They still need to be connected in parallel though. A turn on delay can be made with a few more parts. Mainly a transistor, a pot, and another cap.