Sounds like the shop was just trying to make a sale. Alt whine, if that's what you have, is typically fixable. It's just a matter of tracking down the source.
Do not believe that you NEED to switch amplifier's to make the noise go away.
Does the whine alternate (change pitch, etc) with acceleration or is it a constant, fixed whine ?
Do not believe that you NEED to switch amplifier's to make the noise go away.
Does the whine alternate (change pitch, etc) with acceleration or is it a constant, fixed whine ?
- Thread Starter
- #3
it does change in pitch when I get on the gas, however, if this were alt wine induced in the power circuit, it does not make sense that I can have front plugged in and sound great, rears plugged in and sound great, but not both plugged in or BAD whine. I would think bad grounding or dirty power would be present in all three configurations, not just the one. True he may have been trying to sell me the JL cause theres a high markup, but I think he was on to something with the differential vs non-differential inputs, and radios like pioneer notorious for having interesting and very sensitive internal grounding issues. Also theres alot cheaper amps then JL with differential inputs, and thats probably what I would do, just want to know from some people weather or not this situation is possibly true.
Do not buy a new amp! I started the Stuborn Alt Whine thread and it seems that you and I are in the same boat. I have a pioneer 880 and after installing a four channel I got bad whine. I regrounded EVERYTHING; hu, rca's, both amps and ipod adapter. Without knowing what else could be the cause I went and bought some new RCA'S, after finding out that the new Memphis RCA's that I bought are twisted, not shielded. I bought some $50 monster cable rca's and the noise is completely gone! Now that I know that my rca's were the problem I'll probably take the monsters back and buy some Knukoncepts, to save some cash.
Anyway, check all of your grounds then try a new set of rca's, don'st let them convince you that you need a new amp until you have tried everything.
Anyway, check all of your grounds then try a new set of rca's, don'st let them convince you that you need a new amp until you have tried everything.
- Thread Starter
- #5
Already have triple shielded RCAs, tryed new rcas, and tryed the Knukoncepts isolators to no avail
helotaxi
5,000+ posts
Kilroy was Here
Do you HAVE to have front-rear fade capability? Can you configure the amp to get signal to all 4 channels with only a pair of inputs? I'm pretty sure that you can. If the noise is only present with two sets of RCAs connected and you can get noise free operation of all 4 channels with only one set connected, only connect one set. You can use the gain controls to balance the level front to rear and then leave it set.
My guess as to the actual problem is that a single RCA pair has more resistance than the ground of the HU but adding the second lowers the resistance enough that you get a ground path for the HU through the RCAs when both are connected. Where is your HU grounded and with what size wire? Second possibility (and one I have a bit of personal experience with) is that you have a switch on the amp that is stuck in a an inbetween position and connecting the second set of RCAs is allowing the front channels to short to the rear channels causing your noise. Check the switch positions on you amp. Positively move them to a different position and them move them back to where you want them.
gijoe- I'd wager that the source of your problem is still a marginal HU ground and the reason that the Monster cables worked to fix the problem is that they are directional cables. That means nothing more than the barrel of the RCA is only grounded to the shield on one end and the resistance overall is higher not allowing the HU to partially ground through the RCAs to the amp.
My guess as to the actual problem is that a single RCA pair has more resistance than the ground of the HU but adding the second lowers the resistance enough that you get a ground path for the HU through the RCAs when both are connected. Where is your HU grounded and with what size wire? Second possibility (and one I have a bit of personal experience with) is that you have a switch on the amp that is stuck in a an inbetween position and connecting the second set of RCAs is allowing the front channels to short to the rear channels causing your noise. Check the switch positions on you amp. Positively move them to a different position and them move them back to where you want them.
gijoe- I'd wager that the source of your problem is still a marginal HU ground and the reason that the Monster cables worked to fix the problem is that they are directional cables. That means nothing more than the barrel of the RCA is only grounded to the shield on one end and the resistance overall is higher not allowing the HU to partially ground through the RCAs to the amp.
- Thread Starter
- #7
Thanks for some good info helotaxi, but what your saying is sort of what the dealer was getting at, thats why I am trying to get someone with alot of knowledge about the difference in inputs to post.
I cleaned up a piece of the frame under the dash and ran a fresh ground from the radio to this point, as to bypass the noisy factory grounds.
What your saying about the path being created inside the amp between front and rear channels and causing a feedback loop, is exactly what the dealer was talking about, and per what I gathered with our conversation and my understanding of it, the differential inputs almost acts like 2 separate amps inside the one, and does not allow the amp to create any circuit between the two pairs of RCAs. Thats why he was saying something like a JL, that has the differential inputs, would allow me to plug all the channels into the same amp, with out having a feedback loop, or any bleed through created inside the amp. He also said with amps that have non-differential inputs radios like kenwoods work good cause of diffrent grounding.
Just to add to what else I have done to prevent this:
RCAs run opposite side of vehicle
All cables run away from drive train
High quality shielded RCAs
Radio grounded to frame in dash
I pretty much did everything I could to keep noise out, and I am not inexperienced in car stereo, AND I added isolators after all appropriate measures were taken, I still get noise. Thats why I think it may be something with the equipment not liking each other. But everything you guys had to say was good advice for a place to start, but I am posting this thread cause I have done it all already.
I cleaned up a piece of the frame under the dash and ran a fresh ground from the radio to this point, as to bypass the noisy factory grounds.
What your saying about the path being created inside the amp between front and rear channels and causing a feedback loop, is exactly what the dealer was talking about, and per what I gathered with our conversation and my understanding of it, the differential inputs almost acts like 2 separate amps inside the one, and does not allow the amp to create any circuit between the two pairs of RCAs. Thats why he was saying something like a JL, that has the differential inputs, would allow me to plug all the channels into the same amp, with out having a feedback loop, or any bleed through created inside the amp. He also said with amps that have non-differential inputs radios like kenwoods work good cause of diffrent grounding.
Just to add to what else I have done to prevent this:
RCAs run opposite side of vehicle
All cables run away from drive train
High quality shielded RCAs
Radio grounded to frame in dash
I pretty much did everything I could to keep noise out, and I am not inexperienced in car stereo, AND I added isolators after all appropriate measures were taken, I still get noise. Thats why I think it may be something with the equipment not liking each other. But everything you guys had to say was good advice for a place to start, but I am posting this thread cause I have done it all already.
- Thread Starter
- #8
Taken from: http://www.prosoundweb.com/install/synaudcon/news27_1/difamps_p1.shtml
All credit goes to them
By Pat Brown
Mechanical analogies can be very useful for under standing electrical concepts. Electricity, that unseen force that powers much of the world around us, is an abstract concept to most people because we can’t see it or touch it safely. The simple mechanical system of a bicycle can provide understanding of a common electrical circuit - the differential input.
One of the best ways to avoid extraneous noise pickup in a sound reinforcement system is to properly utilize the differential input on each piece of equipment. The differential input is sensitive to the instantaneous difference between the voltage that arrives at each input terminal. Let’s use a bicycle to gain understanding about this concept.
A professional cyclist utilizes devices on the pedals that allow both the downward pressure and upward pres sure of the foot to be transmitted to the rear wheel. Figure 1 shows a time domain plot of the position of each pedal. Note that this appears as a sine wave when viewed as a function of time, and that there is always a 180 degree phase differential between the two pedals at any instant. Since this differential is fixed and independent of peddling frequency, we could say that the two pedals have a reverse-polarity relationship.
As one pedal is being pushed down by one foot, the other is being pulled up by the other foot. This type of relationship is aptly known as “push pull” and is common in many mechanical and electrical systems. The sprocket is turned by the differential pressure from the two pedals, which is twice the pressure of either pedal considered individually. Also of interest is that if a positive or negative pressure were exerted on both petals simultaneously, no rotation would occur because these two pressures are of opposite polarity and will cancel out at the sprocket. Only when a differential pressure is exerted does the bike move. We could say that our sprocket has high common-mode impedance, because pressures that are identical on both pedals do not cause the bike to move. It has low differential impedance, in that pressures that are reverse-polarity on each pedal cause the bike to go forward. The input impedance of the sprocket therefore describes how effectively energy can flow into it.
Figure 2 - The input signal is derived from the difference between the voltage on the inverting and non-inverting inputs at any instant in time. The result is a signal 6 dB higher in level than the individual signals.
The differential electrical input works in the same manner. It only responds when there is a differential signal present, which is when there is a difference between the voltage on the positive and negative input terminals. If the same voltage is present on each, as you might have from noise that gets coupled into the connecting cable, no input signal is realized across the input terminals. This is how differential inputs reject external noise.
The electrical circuit behaves in the same manner as the mechanical, exhibiting high common-mode impedance to noise signals common to both inputs.
In the mechanical example, if only one pedal were utilized to move the bike, there would only be half of the pressure available. In an electrical circuit, if one input terminal were disconnected or shorted, half of the electrical pressure, or voltage, would be lost. This would re duce the input level to the device by a 2-to-i voltage ratio, or 6 dB. When properly driven from a balanced signal source, the differential input provides a great deal of noise immunity for the sound system.
Also of importance in the mechanical and electrical circuits is proper balancing of the impedances of each input terminal (electrical) or pedal (mechanical). We would not want to have to pedal harder with one foot than the other, so a balanced opposition to the force of the rider’s foot is desired. In the electrical example, if one input terminal has a higher input impedance than the other, then an imbalance results which will reduce the effectiveness of the input in rejecting unwanted (common-mode) input signals.
Of course, all analogies fall short at some point, but hopefully this one has helped in gaining understanding of balanced differential inputs. PB
All credit goes to them
By Pat Brown
Mechanical analogies can be very useful for under standing electrical concepts. Electricity, that unseen force that powers much of the world around us, is an abstract concept to most people because we can’t see it or touch it safely. The simple mechanical system of a bicycle can provide understanding of a common electrical circuit - the differential input.
One of the best ways to avoid extraneous noise pickup in a sound reinforcement system is to properly utilize the differential input on each piece of equipment. The differential input is sensitive to the instantaneous difference between the voltage that arrives at each input terminal. Let’s use a bicycle to gain understanding about this concept.
A professional cyclist utilizes devices on the pedals that allow both the downward pressure and upward pres sure of the foot to be transmitted to the rear wheel. Figure 1 shows a time domain plot of the position of each pedal. Note that this appears as a sine wave when viewed as a function of time, and that there is always a 180 degree phase differential between the two pedals at any instant. Since this differential is fixed and independent of peddling frequency, we could say that the two pedals have a reverse-polarity relationship.
As one pedal is being pushed down by one foot, the other is being pulled up by the other foot. This type of relationship is aptly known as “push pull” and is common in many mechanical and electrical systems. The sprocket is turned by the differential pressure from the two pedals, which is twice the pressure of either pedal considered individually. Also of interest is that if a positive or negative pressure were exerted on both petals simultaneously, no rotation would occur because these two pressures are of opposite polarity and will cancel out at the sprocket. Only when a differential pressure is exerted does the bike move. We could say that our sprocket has high common-mode impedance, because pressures that are identical on both pedals do not cause the bike to move. It has low differential impedance, in that pressures that are reverse-polarity on each pedal cause the bike to go forward. The input impedance of the sprocket therefore describes how effectively energy can flow into it.
Figure 2 - The input signal is derived from the difference between the voltage on the inverting and non-inverting inputs at any instant in time. The result is a signal 6 dB higher in level than the individual signals.
The differential electrical input works in the same manner. It only responds when there is a differential signal present, which is when there is a difference between the voltage on the positive and negative input terminals. If the same voltage is present on each, as you might have from noise that gets coupled into the connecting cable, no input signal is realized across the input terminals. This is how differential inputs reject external noise.
The electrical circuit behaves in the same manner as the mechanical, exhibiting high common-mode impedance to noise signals common to both inputs.
In the mechanical example, if only one pedal were utilized to move the bike, there would only be half of the pressure available. In an electrical circuit, if one input terminal were disconnected or shorted, half of the electrical pressure, or voltage, would be lost. This would re duce the input level to the device by a 2-to-i voltage ratio, or 6 dB. When properly driven from a balanced signal source, the differential input provides a great deal of noise immunity for the sound system.
Also of importance in the mechanical and electrical circuits is proper balancing of the impedances of each input terminal (electrical) or pedal (mechanical). We would not want to have to pedal harder with one foot than the other, so a balanced opposition to the force of the rider’s foot is desired. In the electrical example, if one input terminal has a higher input impedance than the other, then an imbalance results which will reduce the effectiveness of the input in rejecting unwanted (common-mode) input signals.
Of course, all analogies fall short at some point, but hopefully this one has helped in gaining understanding of balanced differential inputs. PB
- Thread Starter
- #9
So my only real question remaining is, the Zeus (http://www.sonicelectronix.com/item_7167_Hifonics+ZXi4406.html) is advertised on HiFonics website as having differential inputs, while I can find nothing saying that the Titan series (http://www.sonicelectronix.com/item_6553_Hifonics+Titan+TXi+4406.html) does. Can anyone confirm if the Titan I have does or does not have differential inputs, as I feel if this guy is correct, and it doesn't, that There-in may lay the problem, and I might fix it by sending my amp back and getting the one for 40 more that does. Lower signal to noise and all that anyway, so wouldnt feel bad.
helotaxi
5,000+ posts
Kilroy was Here
The Titan amp does not. However the way that the dealer described differential inputs is not correct. The tech brief that you cited above is correct. I would be more prone to believe that the amp is bad than believe that differential inputs are going to fix the problem. Diff. inputs are used for line noise rejection, not channel isolation.
That piece of frame in the dash that you grounded to, what's it connected to and how? I'll give you odds that it isn't well electrically connected to the ground plane of the car.
That piece of frame in the dash that you grounded to, what's it connected to and how? I'll give you odds that it isn't well electrically connected to the ground plane of the car.
Does no one here think this could be the Pioneer internal mini-fuse issue?
Have you tried grounding your RCAs? this is a well-documented problem, and I would troubleshoot it from the deck before buying any new amp.
Have you tried grounding your RCAs? this is a well-documented problem, and I would troubleshoot it from the deck before buying any new amp.
- Thread Starter
- #12
can be mini fuse, the dealer said that too, but thinks it will just keep blowing without the right inputs on the amp. I know there trying to make there money too, but sounds like the differential inputs are setting you up for success to begin with. As stated in first post, I have done the Pioneer fix from the noise sticky. I am about to get rid of my car anyway, but the car I am putting it all in is really nice, and want to set this up the right way from the start.
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