defect9 said:
Yes, I understand that. The thing I'm trying to understand here is why he would want to take the signal from the amplifier stage of a HU. If the point of all of this is to lower noise in the system that is a **** poor way of doing it.
It's possible to build a preamp capable of swinging 8Vrms for <$10 that will have lower noise and better quality than the HU speaker outs.
Infoseeker, please don't take offense, but you you asked in the headline, "What's wrong with this?" This is just my take on it.
Quality.
Simply put, the performance of a HU’s internal amp is not as good as an external amp or line driver. Not talking about power output here, but frequency/phase response, and distortion. And keep in mind that these figures change with power level. They are typically optimal at moderate power levels and less than optimal at low and high power levels.
HU IC amps aren’t usually good for 20-20k within 3dB, and phase response will follow when frequency response falls.
These internal amps simply aren’t designed for the best in sound quality, and nothing that happens farther down the line can recover the degradation caused by the source.
A simple op amp line driver designed for operation in preamp impedance ranges will out-perform an adapted speaker-level amp that was already designed with limited performance in its optimum operating range.
Ah, but he was talking about both and how they can relate. That is, the output voltage of the HU amplifier and the input impedance of the load it is driving. He is assuming that the output voltage is sagging under the current demands of a speaker level load, and that inefficiency (remember the Alpine being tested was getting hot) would be reduced into a high impedance load.
The result would be a higher voltage output into a higher impedance load, not because of any specific impedance, but because of the large difference in load impedances and the limitations of the HU’s amplifier.
Then wouldn't this be an obviously better solution to such an important subject? :
I have a friend who used to own a Pantera. You couldn’t keep that car off 100 mph, it just didn’t feel right driving 55. It was like you were creeping. And if you crept along in stop and go city traffic it would overheat every time. Not very useful, huh? As a matter of fact, it turned out to be a pain in the butt. If you drove it fast enough to be happy, you weren’t legal, if you drove it slow enough to be legal you weren’t happy. He sold the car after owning it about a year.
A while back when high voltage outputs and line drivers started to show up in car audio, they WERE used as a noise control device. The idea was to turn the amplifier’s gain control all the way down minimize amplifier hiss and still be able to make full output.
Is this the motivation for wanting such high voltages?
If you want to experiment, go for it. Just pay attention to what you're doing.
I'd start by using one lead (+) per channel with a series capacitor to block DC for the RCA center, and ground the shield to the HU chassis. Expect noise (ask me how I would know...)
Another way would be to use transformers such as those used in Ground Loop Isolators.
Quality.
Simply put, the performance of a HU’s internal amp is not as good as an external amp or line driver. Not talking about power output here, but frequency/phase response, and distortion. And keep in mind that these figures change with power level. They are typically optimal at moderate power levels and less than optimal at low and high power levels.
HU IC amps aren’t usually good for 20-20k within 3dB, and phase response will follow when frequency response falls.
These internal amps simply aren’t designed for the best in sound quality, and nothing that happens farther down the line can recover the degradation caused by the source.
A simple op amp line driver designed for operation in preamp impedance ranges will out-perform an adapted speaker-level amp that was already designed with limited performance in its optimum operating range.
Ah, but he was talking about both and how they can relate. That is, the output voltage of the HU amplifier and the input impedance of the load it is driving. He is assuming that the output voltage is sagging under the current demands of a speaker level load, and that inefficiency (remember the Alpine being tested was getting hot) would be reduced into a high impedance load.
The result would be a higher voltage output into a higher impedance load, not because of any specific impedance, but because of the large difference in load impedances and the limitations of the HU’s amplifier.
Then wouldn't this be an obviously better solution to such an important subject? :
I have a friend who used to own a Pantera. You couldn’t keep that car off 100 mph, it just didn’t feel right driving 55. It was like you were creeping. And if you crept along in stop and go city traffic it would overheat every time. Not very useful, huh? As a matter of fact, it turned out to be a pain in the butt. If you drove it fast enough to be happy, you weren’t legal, if you drove it slow enough to be legal you weren’t happy. He sold the car after owning it about a year.
A while back when high voltage outputs and line drivers started to show up in car audio, they WERE used as a noise control device. The idea was to turn the amplifier’s gain control all the way down minimize amplifier hiss and still be able to make full output.
Is this the motivation for wanting such high voltages?
If you want to experiment, go for it. Just pay attention to what you're doing.
I'd start by using one lead (+) per channel with a series capacitor to block DC for the RCA center, and ground the shield to the HU chassis. Expect noise (ask me how I would know...)
Another way would be to use transformers such as those used in Ground Loop Isolators.
hello guys gud day 2 all,,im greg in the phillipines,,,im new in here...can somebody help me how to remove the popping sound of the car audio set up i checked all my lines and it was all good my grounds my cables are in proper connections,it appears when i lower my volume to zero,,pls i really need some help,,thanksb in advance i appriciate all of the replies
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.