I have an Alpine CDA-7840 HU connected to an Alpine ERA- G320 sound field processeor.
My 1st question is, does the Ai-net provide an unclipped signal at full HU volume?
2nd question is, if the Ai-net does not provide an uclipped signal at full HU volume, which pins do I probe in the AI-net cable connector to get output voltage on an oscilloscope.
3rd, Is there a site that I can find out just what AI-net is and does. Alpines site was no help, and searching goole didn't help. I want info just specific to AI-net it's description and capabilites and specs.
Replies (11)
swez on 01/13/2008 12:55:31
Hum, this is very technical and I see why you want that information. I can try to toss a few ideas your way, but they are more general in nature.
Most aftermarket HU's will begin to clip at about 80% of max volume. If using EQ boost or loudness contour features, this may happen even sooner on some well-juiced CD's and MP3 audio material. (Hip Hop and many Rap songs really kick up the bass loading and these can easily clip the HU sooner.
You can measure the clipping levels from the HU amplifers or RCA's with the O-Scope. Test tones can be used to give a single sinusoidal wave form. When the peaks of the wave begin to flatten out or change shape, the source amplifier(s) is/are clipping. It would be best to load the amp with a speaker or a dummy load resistor to get an accurate reading from the output stage of the amps or preamps being tested.
When running program music on an O-Scope, the wave forms are very complex and it may be very difficult to spot all but heavy clipping on the scope. Our ears may be a good tool in conjunction with the scope to figure out when clipping begins to show up. If one knows what clipping sounds like in real time, then we can coorelate that with the wave forms seen on the O-Scope as well.
As for the Ai-Net, this is a very complex processor and many features as well. (Sweet) From a little research, the main features are:
Listening Position Selector (LPS)
BBE Processor (4 BBE Modes, 1,2,3 and off)
DSP Surround 14-Band Digital Equalizer (3 modes)
One pair of RCA input, and 3 pair of RCA outputs (F/R/Sub)
Here's the operations manual for this processor:
http://vault.alpine-usa.com/products/documents/OM_ERA-G320.PDF
Wow, this is a huge file and some very tedious preset tools available as well.
6 main EQ presets here: (Flat, Male, Female, Pop, Rock & News)
The LPS features are neat, but one needs to measure the distance of each speaker to the listener to determine the correct time delays for each speaker location. (In a small sedan, this may not be much of a factor as we a dealing with micro-seconds and may not be needed)
This device seems to have a self-calibration feature too. If the input signal gets too for the sensing circuit threshold, a light will come on and tell us to readjust input source power as needed to correct the situation. (More like a sensitivity/gain feature in most high-eng amplifiers)
This is an "anti-clipping sensor" of sorts. If we note steady illumination, the system is clipping badly. A few momentary blinks on peak music transients may be a good place to start the calibration process and optimize as needed. It seems that when using Ai-Net HU's, this is done automatically. Non-Ai-Net HU's are adjusted manually via the menu system shown in the manual. (Looks like you don't have to tinker with this feature)
Anyway, read the manual carefully, experiment with the features to determined the best settings for your listening pleasure. When using any EQ or BBE features, "Less is More" in most cases. Minimal EQ boost is recommended. It is better to cut adjacent EQ presets below flat then leave most flat and boost the lows and highs above +5 or 6dB.
OK, that's it for now. Once you have reviewed this manual, most of your questions will be answered or at least directed to specific features and their use. Again, be a "Minimalist" when at all possible.
Comments?
Swez
storis on 01/13/2008 13:19:50
Thanks Swez, Using the Ai-net I do not use the rca out jacks on the head unit at all.
So I guess from reading your reply the answer is using Ai-net the head unit will not send a clipped waveform to the processor. So i should be able connect the oscilloscope to the speaker leads and adjust amp gain with out being concerned about anthing upstream of the amp clipping.
swez on 01/13/2008 14:15:30
Yes, in theory... that is what you'll want to do. Ai-Net HU's appear to be calibrated and automatictally adjust HU/Ai-Net components w/ minimal work from the user. Using your O-scope and a "non-reactive" dummy load, (pure resistance, and not capacitive or inductive
When setting gains we look at AC voltage targets from a given amp, to a specified load. (Speakers impedance or a fixed value dummy load) When dealing with subwoofers, we can take direct voltage reading off the amp with the sub wired as the load and get very good results. A 50 Hz. test tone @ 0dB reference works fine.
Component based speakers are harder to calibrate with the amp as they present complex impedance issues at various crossover frequencies. We cannot get an accurate AC voltage measurement this way. Here, we often use a non-reactive "Dummy Load" or a simple full range speaker as the load. In this case, we use "Pink Noise", (full range) test tones as the audio source and again, they are @ 0dB reference levels. That will get one into the "ballpark". But an RTA, (Real Time Analyzer) is the best tool for this type of SQ tweaking. This tool also requires a calibrated microphone as well.
More?
Swez
MrBrownstone on 01/15/2008 18:55:42
Since you are using line level output, I'd doubt you'd be able to clip the signal on any head unit. Bass boosts, etc., can all add up, but when you are sending voltage out at 10kOhms, I highly doubt you'd clip the signal FROM the HU without maxing out all the controls first.
However, on the sig proc or other device, it's likely you can saturate the input...but again, I wouldn't lose sleep over it.
Remember, if the recording is quiet (zero output), there'll be no output. If the output is above 32767, then there could be clipping...but again, it depends upon the sound you are reproducing.
storis on 01/15/2008 21:15:35
I am sorry, I am not trying to slam you MrBrownstone, but none of what you wrote makes any sense to me.
First off I am not sure Ai-net is a line level output. Line level output is the color coded wires coming out of the bck of the HU that you hook your speakers to. That is not what Alpines Ai-net is. (I have checked on Alpines website, and searched on google and cannot find any description of what it is or any technical info on it).
I have some electrical/electronic knowledge, and you do not send voltage out. Voltage is considered electrical pressure and does not flow. Amperage is considered electrical current and that is what flows through the circuits; and I have no idea what you are talking about sending it out at 10kohms. you don't send anything anywhere in ohms that is resistance.
Your last sentence isn't clear to me either, yes of course 0 input signal will be 0 voltage at the output, but I am totally clueless as to what 32767 is or has to do with clipping.
storis on 01/16/2008 00:41:01
Well, I went back and spent an evening searching google for info on Alpine's Ai-net. I didn't find much what I did find is it is something called proprietary high speed data transfer system bus.
So, I am guessing it is digital output to the processor from the HU, therefore the output from the HU will not be clipped even at full HU volume, once the signal is processed it must be converted to analog and sent to the amplifier. Which means all I have to do is, turn the HU volume all the way up connect to the speaker leads with the scope and set my gain (This is all guessing on my part). I hope someone can verify this for sure or point me to where I can get info about AI-net.
I also found an Ai-net connector pinout diagram.
Victor on 01/16/2008 01:12:55
http://www.mp3car.com/vbulletin/input-devices/79766-diy-alpine-ai-net-rca-head-phone-adapter-ipod-gurus-needed.html
hope this helps...
Victor...
storis on 01/16/2008 01:26:59
Thanks Victor, thats the site where I got the pinout diagram from. I guess I'll call the alpine techs tomorrow.
cplkittle on 01/17/2008 17:29:00
The Ai Net is exactly as you said - digital output/input.
I am looking into purchasing the PXA-H701 multimedia manager / sound processor. In my case I am using the CDA-9835 HU, and when I connect the H701, it will take controll over some of the basic features my HU normally controlled (fade, balance, eq, MX, LPF, HPF, stage/delay, etc..) There is a switch on the bottom of my HU that I have to change over to Ai net when I attach this unit.
So the way I understand it, is that it integrates with the HU, and the RCA outputs on the EQ or processor are now the outputs that are to be used for the amplifiers. What ever the additional unit is rated at would be the standard for measurement (ie. 4v preouts) Everything will be measured as it would if you were just using the HU RCA outs. Volume at 3/4 with all EQs, filters, and enhancements turned off.
I personally don't see a need in determining if the HU presents a clipped signal at full volume. Clipping should be measured and adjusted out at the amplifier outputs. If the amplifier is set properly to the output voltage of the HU, clipping should no occur unless the amplifier is a flea market brand. Here is a link for an easy way to set gains without an O-scope. It is not as accurate as the way you described, but I don't think the human ear could distinguish between this method, and a perfectly measured and balanced setup.
http://www.datafilehost.com/download.php?file=6d26c621
This is an excel spreadsheet with an imbedded 60 second 60Hz test tone that you can burn to a CD.
storis on 01/18/2008 05:14:11
I called Alpine the other day and you are correct the processor acts like it is part of the HU. They did not recommend probing the Ainet connector due to the risk of something getting shorted out, they said all I would see is approx. a 3.8v rapid pulse. They said to connect the scope to the processors rca outputs, turn the HU up until the scope shows a clipped waveform, then turn it down until the waveform is no longer clipped (this should be around 3/4 on the volume knob). Then go ahead and set amp gain
MrBrownstone on 01/24/2008 13:43:11
there are 2 different issues here. Clipped signal coming from the head unit & the transferred data to the amplifier.
The only way you can clip a 10101010 signal is if the intended output is higher than the digital maximum. Of course, that may not even be possible so it's of little concern.
Clipped signal occurs when the user is asking their amplification device to put out a higher voltage than it is capable of. Digital signal isn't using variable voltage, rather, 1s & 0s to typify the signal.
In any case, all of your issues will stem from the amplifier or signal processor leading into the amplifier and not from the head unit.
PS there's no reason your head unit should clip at 100% of the volume with or without tone controls maxed
My 1st question is, does the Ai-net provide an unclipped signal at full HU volume?
2nd question is, if the Ai-net does not provide an uclipped signal at full HU volume, which pins do I probe in the AI-net cable connector to get output voltage on an oscilloscope.
3rd, Is there a site that I can find out just what AI-net is and does. Alpines site was no help, and searching goole didn't help. I want info just specific to AI-net it's description and capabilites and specs.
Replies (11)
swez on 01/13/2008 12:55:31
Hum, this is very technical and I see why you want that information. I can try to toss a few ideas your way, but they are more general in nature.
Most aftermarket HU's will begin to clip at about 80% of max volume. If using EQ boost or loudness contour features, this may happen even sooner on some well-juiced CD's and MP3 audio material. (Hip Hop and many Rap songs really kick up the bass loading and these can easily clip the HU sooner.
You can measure the clipping levels from the HU amplifers or RCA's with the O-Scope. Test tones can be used to give a single sinusoidal wave form. When the peaks of the wave begin to flatten out or change shape, the source amplifier(s) is/are clipping. It would be best to load the amp with a speaker or a dummy load resistor to get an accurate reading from the output stage of the amps or preamps being tested.
When running program music on an O-Scope, the wave forms are very complex and it may be very difficult to spot all but heavy clipping on the scope. Our ears may be a good tool in conjunction with the scope to figure out when clipping begins to show up. If one knows what clipping sounds like in real time, then we can coorelate that with the wave forms seen on the O-Scope as well.
As for the Ai-Net, this is a very complex processor and many features as well. (Sweet) From a little research, the main features are:
Listening Position Selector (LPS)
BBE Processor (4 BBE Modes, 1,2,3 and off)
DSP Surround 14-Band Digital Equalizer (3 modes)
One pair of RCA input, and 3 pair of RCA outputs (F/R/Sub)
Here's the operations manual for this processor:
http://vault.alpine-usa.com/products/documents/OM_ERA-G320.PDF
Wow, this is a huge file and some very tedious preset tools available as well.
6 main EQ presets here: (Flat, Male, Female, Pop, Rock & News)
The LPS features are neat, but one needs to measure the distance of each speaker to the listener to determine the correct time delays for each speaker location. (In a small sedan, this may not be much of a factor as we a dealing with micro-seconds and may not be needed)
This device seems to have a self-calibration feature too. If the input signal gets too for the sensing circuit threshold, a light will come on and tell us to readjust input source power as needed to correct the situation. (More like a sensitivity/gain feature in most high-eng amplifiers)
This is an "anti-clipping sensor" of sorts. If we note steady illumination, the system is clipping badly. A few momentary blinks on peak music transients may be a good place to start the calibration process and optimize as needed. It seems that when using Ai-Net HU's, this is done automatically. Non-Ai-Net HU's are adjusted manually via the menu system shown in the manual. (Looks like you don't have to tinker with this feature)
Anyway, read the manual carefully, experiment with the features to determined the best settings for your listening pleasure. When using any EQ or BBE features, "Less is More" in most cases. Minimal EQ boost is recommended. It is better to cut adjacent EQ presets below flat then leave most flat and boost the lows and highs above +5 or 6dB.
OK, that's it for now. Once you have reviewed this manual, most of your questions will be answered or at least directed to specific features and their use. Again, be a "Minimalist" when at all possible.
Comments?
Swez
storis on 01/13/2008 13:19:50
Thanks Swez, Using the Ai-net I do not use the rca out jacks on the head unit at all.
So I guess from reading your reply the answer is using Ai-net the head unit will not send a clipped waveform to the processor. So i should be able connect the oscilloscope to the speaker leads and adjust amp gain with out being concerned about anthing upstream of the amp clipping.
swez on 01/13/2008 14:15:30
Yes, in theory... that is what you'll want to do. Ai-Net HU's appear to be calibrated and automatictally adjust HU/Ai-Net components w/ minimal work from the user. Using your O-scope and a "non-reactive" dummy load, (pure resistance, and not capacitive or inductive
When setting gains we look at AC voltage targets from a given amp, to a specified load. (Speakers impedance or a fixed value dummy load) When dealing with subwoofers, we can take direct voltage reading off the amp with the sub wired as the load and get very good results. A 50 Hz. test tone @ 0dB reference works fine.
Component based speakers are harder to calibrate with the amp as they present complex impedance issues at various crossover frequencies. We cannot get an accurate AC voltage measurement this way. Here, we often use a non-reactive "Dummy Load" or a simple full range speaker as the load. In this case, we use "Pink Noise", (full range) test tones as the audio source and again, they are @ 0dB reference levels. That will get one into the "ballpark". But an RTA, (Real Time Analyzer) is the best tool for this type of SQ tweaking. This tool also requires a calibrated microphone as well.
More?
Swez
MrBrownstone on 01/15/2008 18:55:42
Since you are using line level output, I'd doubt you'd be able to clip the signal on any head unit. Bass boosts, etc., can all add up, but when you are sending voltage out at 10kOhms, I highly doubt you'd clip the signal FROM the HU without maxing out all the controls first.
However, on the sig proc or other device, it's likely you can saturate the input...but again, I wouldn't lose sleep over it.
Remember, if the recording is quiet (zero output), there'll be no output. If the output is above 32767, then there could be clipping...but again, it depends upon the sound you are reproducing.
storis on 01/15/2008 21:15:35
I am sorry, I am not trying to slam you MrBrownstone, but none of what you wrote makes any sense to me.
First off I am not sure Ai-net is a line level output. Line level output is the color coded wires coming out of the bck of the HU that you hook your speakers to. That is not what Alpines Ai-net is. (I have checked on Alpines website, and searched on google and cannot find any description of what it is or any technical info on it).
I have some electrical/electronic knowledge, and you do not send voltage out. Voltage is considered electrical pressure and does not flow. Amperage is considered electrical current and that is what flows through the circuits; and I have no idea what you are talking about sending it out at 10kohms. you don't send anything anywhere in ohms that is resistance.
Your last sentence isn't clear to me either, yes of course 0 input signal will be 0 voltage at the output, but I am totally clueless as to what 32767 is or has to do with clipping.
storis on 01/16/2008 00:41:01
Well, I went back and spent an evening searching google for info on Alpine's Ai-net. I didn't find much what I did find is it is something called proprietary high speed data transfer system bus.
So, I am guessing it is digital output to the processor from the HU, therefore the output from the HU will not be clipped even at full HU volume, once the signal is processed it must be converted to analog and sent to the amplifier. Which means all I have to do is, turn the HU volume all the way up connect to the speaker leads with the scope and set my gain (This is all guessing on my part). I hope someone can verify this for sure or point me to where I can get info about AI-net.
I also found an Ai-net connector pinout diagram.
Victor on 01/16/2008 01:12:55
http://www.mp3car.com/vbulletin/input-devices/79766-diy-alpine-ai-net-rca-head-phone-adapter-ipod-gurus-needed.html
hope this helps...
Victor...
storis on 01/16/2008 01:26:59
Thanks Victor, thats the site where I got the pinout diagram from. I guess I'll call the alpine techs tomorrow.
cplkittle on 01/17/2008 17:29:00
The Ai Net is exactly as you said - digital output/input.
I am looking into purchasing the PXA-H701 multimedia manager / sound processor. In my case I am using the CDA-9835 HU, and when I connect the H701, it will take controll over some of the basic features my HU normally controlled (fade, balance, eq, MX, LPF, HPF, stage/delay, etc..) There is a switch on the bottom of my HU that I have to change over to Ai net when I attach this unit.
So the way I understand it, is that it integrates with the HU, and the RCA outputs on the EQ or processor are now the outputs that are to be used for the amplifiers. What ever the additional unit is rated at would be the standard for measurement (ie. 4v preouts) Everything will be measured as it would if you were just using the HU RCA outs. Volume at 3/4 with all EQs, filters, and enhancements turned off.
I personally don't see a need in determining if the HU presents a clipped signal at full volume. Clipping should be measured and adjusted out at the amplifier outputs. If the amplifier is set properly to the output voltage of the HU, clipping should no occur unless the amplifier is a flea market brand. Here is a link for an easy way to set gains without an O-scope. It is not as accurate as the way you described, but I don't think the human ear could distinguish between this method, and a perfectly measured and balanced setup.
http://www.datafilehost.com/download.php?file=6d26c621
This is an excel spreadsheet with an imbedded 60 second 60Hz test tone that you can burn to a CD.
storis on 01/18/2008 05:14:11
I called Alpine the other day and you are correct the processor acts like it is part of the HU. They did not recommend probing the Ainet connector due to the risk of something getting shorted out, they said all I would see is approx. a 3.8v rapid pulse. They said to connect the scope to the processors rca outputs, turn the HU up until the scope shows a clipped waveform, then turn it down until the waveform is no longer clipped (this should be around 3/4 on the volume knob). Then go ahead and set amp gain
MrBrownstone on 01/24/2008 13:43:11
there are 2 different issues here. Clipped signal coming from the head unit & the transferred data to the amplifier.
The only way you can clip a 10101010 signal is if the intended output is higher than the digital maximum. Of course, that may not even be possible so it's of little concern.
Clipped signal occurs when the user is asking their amplification device to put out a higher voltage than it is capable of. Digital signal isn't using variable voltage, rather, 1s & 0s to typify the signal.
In any case, all of your issues will stem from the amplifier or signal processor leading into the amplifier and not from the head unit.
PS there's no reason your head unit should clip at 100% of the volume with or without tone controls maxed
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