Good thread on debugging radio is missing
10-24-2001, 01:15 PM
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Good thread on debugging radio is missing
Those who posted to the thread last week regarding debuggin alternator whine in radio/stereo, can you please repost? I esp want the part about alt whine in radio, and the porsche mailing/instructions on fixing it.
For my part, I'll remind you that there can be two components to the problem -- the radio antenna/amplifier itself can pick up ignition noise, while the Head unit/amplifier/speaker chain can be another source of the problem.
A good site to learn about the debug process is the car sound Bulletin Board: http://www.carsound.com/cgi-bin/ubbc...i?action=intro -- look at David Navone on troubleshooting, search for alternator whine.....
The basic routine is:
1.Unplug the antenna -- noise remains?
2. if so...mute the amp using mute plugs -- take a pair of RCA jacks, cut them, fuse the positive and negative for a given jack toether. Then plug these in to the amplifier's inputs. If when you run the car, the noise is gone, the problem lies in either the head unit or the wires connecting the head unit to the amp.
One post said replacing the expensive wires with cheap fixed hir problem -- this is affirmed at tthe Car sound site, basically, sheilded wires great a haven for inducted noise in noisy environments.....
Read Car Sound, they really are pros..
FYI -- I have the Rod Birch setup, and noise, but no time, right now, to go through another round of debugging, but I believe I know where the problem lies. When I'm done with a house remodeling project, and weekends at the track, I'll get back to the stereo.....
For my part, I'll remind you that there can be two components to the problem -- the radio antenna/amplifier itself can pick up ignition noise, while the Head unit/amplifier/speaker chain can be another source of the problem.
A good site to learn about the debug process is the car sound Bulletin Board: http://www.carsound.com/cgi-bin/ubbc...i?action=intro -- look at David Navone on troubleshooting, search for alternator whine.....
The basic routine is:
1.Unplug the antenna -- noise remains?
2. if so...mute the amp using mute plugs -- take a pair of RCA jacks, cut them, fuse the positive and negative for a given jack toether. Then plug these in to the amplifier's inputs. If when you run the car, the noise is gone, the problem lies in either the head unit or the wires connecting the head unit to the amp.
One post said replacing the expensive wires with cheap fixed hir problem -- this is affirmed at tthe Car sound site, basically, sheilded wires great a haven for inducted noise in noisy environments.....
Read Car Sound, they really are pros..
FYI -- I have the Rod Birch setup, and noise, but no time, right now, to go through another round of debugging, but I believe I know where the problem lies. When I'm done with a house remodeling project, and weekends at the track, I'll get back to the stereo.....
10-24-2001, 03:38 PM
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Hi Craig-
I was the initiator of the that thread. I can't remember all that went on - but it went something like this.
I purchased the Car Audio Innovation (CAI) i.e., the Rod Birch setup, and performed the install myself of a sub and a MTX amplifier under the passenger seat.
Huge noise issues. I called CAI and while they were very patient, they seemed to kind of be surprised there was that much noise. They argued for a ground loop, and then blamed my head unit. However, this didn't sound right to me, because the orginal setup had NO noise and all I did was add an amplifier. I did all kinds of testing at their beheast.
I went through all kinds of ground loop chasing, rerouting, tying the RCA plug outer shields into the ground, running common grounds to the battery. I did discover that when both RCA cable sets were plugged in, noise was at a maximum, and CAI suggested a potential difference in ground between the front and rear outs on the head. I felt that something, albeit less amplified, should have been there before the amplifier install if this were the case.
Anyway, at a point of dispair, I went with a hunch which was that noise was resulting from EMI through the high-end cables sold to me by CAI for the amp-head unit connection. I pulled out the $50.00 pair of Stinger 24K gold plated, oxygen-free, directional, shielded-twisted-pair RCA cables with depleted uranium tips and double-super nitrous oxide alcohol-burning insulation, and replaced these with a $2 piece of crap 4-strand RCA cable from the back of my home stereo. Noise went away.
I think the CAI folks are good, mean well, and are very customer oriented. I'd buy from them again anytime. I also think the facts in this case point to a root-cause that people need to be more open in considering.
Noise aside, I challenge anyone who can hear the difference in a pair of these high-end cables and a set of rubber coated wires from radio shack.
I was the initiator of the that thread. I can't remember all that went on - but it went something like this.
I purchased the Car Audio Innovation (CAI) i.e., the Rod Birch setup, and performed the install myself of a sub and a MTX amplifier under the passenger seat.
Huge noise issues. I called CAI and while they were very patient, they seemed to kind of be surprised there was that much noise. They argued for a ground loop, and then blamed my head unit. However, this didn't sound right to me, because the orginal setup had NO noise and all I did was add an amplifier. I did all kinds of testing at their beheast.
I went through all kinds of ground loop chasing, rerouting, tying the RCA plug outer shields into the ground, running common grounds to the battery. I did discover that when both RCA cable sets were plugged in, noise was at a maximum, and CAI suggested a potential difference in ground between the front and rear outs on the head. I felt that something, albeit less amplified, should have been there before the amplifier install if this were the case.
Anyway, at a point of dispair, I went with a hunch which was that noise was resulting from EMI through the high-end cables sold to me by CAI for the amp-head unit connection. I pulled out the $50.00 pair of Stinger 24K gold plated, oxygen-free, directional, shielded-twisted-pair RCA cables with depleted uranium tips and double-super nitrous oxide alcohol-burning insulation, and replaced these with a $2 piece of crap 4-strand RCA cable from the back of my home stereo. Noise went away.
I think the CAI folks are good, mean well, and are very customer oriented. I'd buy from them again anytime. I also think the facts in this case point to a root-cause that people need to be more open in considering.
Noise aside, I challenge anyone who can hear the difference in a pair of these high-end cables and a set of rubber coated wires from radio shack.
10-24-2001, 05:13 PM
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Does it make a difference in debugging whether the noise is a hum, like you might hear in a ground loop in a home system, or a whine that changes pitch with the engine speed? Are they really just the same thing or do they have different causes? I have a Rod Birch system (but no subwoofer yet) and have a whine related to engine speed. It is not loud enough to affect listening to moderately loud music, but when the music is quiet and the engine is revving it is annoying.
10-24-2001, 07:29 PM
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Tom-
I have installed a high-end stereo in each of my vehicles since I was 16 years old, and every single one had alternator whine hum of some sort that had to be addressed. Some slight, some intense. I would characterize the whine I just addressed in my 964 as the worst yet. I can be the result of a ground loop as you suggest. However, in my case, this was EMI caused by the cables interacting with other sources in/on/through the chassis.
I would strongly suggest that you take a look at changing and/or rerouting those RCA cables.
I have installed a high-end stereo in each of my vehicles since I was 16 years old, and every single one had alternator whine hum of some sort that had to be addressed. Some slight, some intense. I would characterize the whine I just addressed in my 964 as the worst yet. I can be the result of a ground loop as you suggest. However, in my case, this was EMI caused by the cables interacting with other sources in/on/through the chassis.
I would strongly suggest that you take a look at changing and/or rerouting those RCA cables.
10-25-2001, 11:17 AM
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I'm still looking for the post that had the info on the radio/alternator interference. The poster had the Porsche Technical Bulletin on that problem. I'm 99% certain that my car has two (at least) sources of hum, one in the basic head unit/interconnect/amp set up (somewhat easy fix), and the other in the antenna amplifier/noise suppressor setup. It is really noticable as I accelerate, with bad static up to an RPM point, but once I set a new rpm level, the noise drops off somewhat.
Just for other confusion, I installed a Birch setup myself, and went through two amps -- the first one was installed under the seat and got horrible alternator noise, which was lessened by taking the amp out of the seat well. (there's a big black power cable that runs on the side of the seat well from the battery back to the engine.....)
I finally got a better amp that was too large for the seat well and installed it in the forn instead. This introduced a longer interconnect run, whioch is prone to interference/inductance.
Whatever. Projects like this make you an ever-greater expert on your car. What doesn't kill you makes you stronger, or something like that......
Just for other confusion, I installed a Birch setup myself, and went through two amps -- the first one was installed under the seat and got horrible alternator noise, which was lessened by taking the amp out of the seat well. (there's a big black power cable that runs on the side of the seat well from the battery back to the engine.....)
I finally got a better amp that was too large for the seat well and installed it in the forn instead. This introduced a longer interconnect run, whioch is prone to interference/inductance.
Whatever. Projects like this make you an ever-greater expert on your car. What doesn't kill you makes you stronger, or something like that......
10-26-2001, 05:12 AM
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Craig-
here is TSB X9104...
Electrical Problems Due to Aftermarket Equipment
91porsche06
September 10, 1991
Model
All Models
Group
X
Part Identifier
N/A
Number
9104
Subject:
Installation of Aftermarket
Equipment (Electrical)
ATTENTION:
Service Manager/Service Technician
Models Affected:
All
Concern:
Electrical problems due to the installation of aftermarket equipment.
General Information:
With the sale of aftermarket alarms, stereo radios, CD players etc., there has been an increasing number of vehicle electrical problems arising, many of which are directly and/or indirectly tied to installation of such equipment. Examples are:
Discharged battery caused by excessive current draw from added equipment. In the case of aftermarket alarms, they often are spliced into the existing alarm systems using inferior connectors. The actual connecting of the two systems often results in a malfunction that appears to be in the factory alarm and is later found to be caused by the aftermarket alarm interface to the factory unit. Additionally, since these aftermarket systems are installed by non-dealership technicians or outside the selling dealer, technicians at the dealer have no working knowledge of the aftermarket equipment layout and electrical connection to the vehicles electrical system.
With aftermarket equipment installation, cables and wires must be laid in the vehicle. These cables often run parallel to existing vehicle harnesses and have been known to cause interference in other vehicle systems when activated. Intermittent open circuits can be created causing difficult to diagnose electrical problems. In addition, holes drilled in the body for the purpose of routing cables are not treated to prevent rust, and frequently rubber grommets are not used to prevent harness cuts and possible short circuits.
In extreme cases, short circuits can develop and cause electrical fires. In many of these cases, damage is so extensive that it becomes difficult, if not impossible, to determine the cause.
Since aftermarket equipment is not approved by Porsche, and no accommodations have been made for such equipment during the vehicle design phase, Porsche accepts no responsibility for damages to vehicles related to aftermarket equipment installation.
In addition, dealers should not install or sublet the installation of such items on vehicles at any time.
Repair Procedure:
In the event that a vehicle is brought in for service with verified electrical problems, and contains aftermarket electrical equipment, the vehicle should first be examined for obvious problems. If initial repair does not resolve the issue, the vehicle must have all aftermarket electrical equipment disconnected and the problem must again be verified before any further diagnosis. It should be made clear to the customer that all diagnosis and repair(s) resulting from aftermarket equipment are not warranty matters.
here is TSB X9104...
Electrical Problems Due to Aftermarket Equipment
91porsche06
September 10, 1991
Model
All Models
Group
X
Part Identifier
N/A
Number
9104
Subject:
Installation of Aftermarket
Equipment (Electrical)
ATTENTION:
Service Manager/Service Technician
Models Affected:
All
Concern:
Electrical problems due to the installation of aftermarket equipment.
General Information:
With the sale of aftermarket alarms, stereo radios, CD players etc., there has been an increasing number of vehicle electrical problems arising, many of which are directly and/or indirectly tied to installation of such equipment. Examples are:
Discharged battery caused by excessive current draw from added equipment. In the case of aftermarket alarms, they often are spliced into the existing alarm systems using inferior connectors. The actual connecting of the two systems often results in a malfunction that appears to be in the factory alarm and is later found to be caused by the aftermarket alarm interface to the factory unit. Additionally, since these aftermarket systems are installed by non-dealership technicians or outside the selling dealer, technicians at the dealer have no working knowledge of the aftermarket equipment layout and electrical connection to the vehicles electrical system.
With aftermarket equipment installation, cables and wires must be laid in the vehicle. These cables often run parallel to existing vehicle harnesses and have been known to cause interference in other vehicle systems when activated. Intermittent open circuits can be created causing difficult to diagnose electrical problems. In addition, holes drilled in the body for the purpose of routing cables are not treated to prevent rust, and frequently rubber grommets are not used to prevent harness cuts and possible short circuits.
In extreme cases, short circuits can develop and cause electrical fires. In many of these cases, damage is so extensive that it becomes difficult, if not impossible, to determine the cause.
Since aftermarket equipment is not approved by Porsche, and no accommodations have been made for such equipment during the vehicle design phase, Porsche accepts no responsibility for damages to vehicles related to aftermarket equipment installation.
In addition, dealers should not install or sublet the installation of such items on vehicles at any time.
Repair Procedure:
In the event that a vehicle is brought in for service with verified electrical problems, and contains aftermarket electrical equipment, the vehicle should first be examined for obvious problems. If initial repair does not resolve the issue, the vehicle must have all aftermarket electrical equipment disconnected and the problem must again be verified before any further diagnosis. It should be made clear to the customer that all diagnosis and repair(s) resulting from aftermarket equipment are not warranty matters.
10-26-2001, 05:17 AM
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And TSB 99101...
Alternator Radio Interference
91porsche03
February 28, 1991
Model Group
911C2/C4/T 9
Part Identifier Number
9735 9101
Subject:
Radio Interference from Alternator
ATTENTION: Service Manager/Service Technician
Models Affected: 911 Carrera 2 and 911 Carrera 4
911 Turbo (Model Year 1991)
Concern: Radio interference (whistling) from alternator.
Figure 1
Repair Information: An interference suppression filter may be installed on the engine compartment fuse/relay board to alleviate this condition (arrow, Figure 1).
It is installed on all vehicles from production date:
November 15, 1990
VIN: WP0AB296 - MS 41 0989 - Coupe
WP0BB296 - MS 44 0438 - Targa
WP0CB296 - MS 46 1025 - Cabriolet
WP0AA296 - MS 48 0086 - Turbo
Service Information: When diagnosing radio interference complaints on earlier 911C2/C4 models, first check:
a. Cable routing. The connecting cable, radio to booster, must be routed away from battery plus cable (on shift console right side). Distance between both cables should be 30-40 cm.
Figure 2
Service Information (cont.):
b. Ground wire for booster. Disconnect ground wire from booster (term.1 - brown wire) install new 4 mm diameter wire and connect to ground point XX on seat cross member under the right seat.
c. Check ignition wires for correct routing and installation. Spark plug connectors must be tight.
d. Interference suppression filter and additional wiring harness (Figure 2) can be installed in 911 Carrera 2/4 prior to the VIN numbers on page one.
Work Procedure: 1. Disconnect battery. Remove heater duct in engine compartment and cover flange with a shop towel. Remove fuse relay board cover in engine compartment.
2. Unscrew carrier plate and housing from body. Remove housing.
3. Remove both wiring tie straps from back side of carrier plate.
Figure 3
4. Cut wiring protection sleeves for wiring harness leading to fuses approximately 10 cm and remove (Figure 3, arrow A).
Careful, do not cut wiring
5. Apply two layers of textile tape to edge of the carrier plate (arrow E, shaded area).
6. Install suppression filter between the two wiring plugs. Make sure suppression filter engages properly at the bottom; push against clip on filter to ease engagement. Route wiring harness leading to fuses under the engagement bracket (arrow B).
7. Connect new wiring harness (Part Number 964 645 901 00) to suppression filter 2 pin plug and 12 pin DME wiring plug.
8. Route voltage supply wire (Figure 3, arrow C) and connect with the supplied quick connector to one of the four red 2.5 mm diameter wires (arrow D). The distance between the suppression filter and the quick connector must be sufficient to ease installation of the carrier plate.
Figure 4
9. Reinstall housing and carrier plate.
Note: When installing carrier plate, make sure the plate contacts the stops on the housing (Figure 4, arrow F). To achieve proper installation, it may be necessary to pull both wiring harnesses approximately 3 cm towards the front (Figure 4) and to push bottom of suppression filter slightly towards the front.
10. Reinstall fuse relay board cover and heater duct. Connect battery. Perform system adaption, set clock and code radio.
Parts Information: Interference suppression filter: Part Number 964 645 011 00
Wiring harness: Part Number 964 645 901 00
Warranty Information: Installing suppression filter and wiring harness.Labor Operation: 9735190A
Damage Code: 9735400002
Time Units: 100
Alternator Radio Interference
91porsche03
February 28, 1991
Model Group
911C2/C4/T 9
Part Identifier Number
9735 9101
Subject:
Radio Interference from Alternator
ATTENTION: Service Manager/Service Technician
Models Affected: 911 Carrera 2 and 911 Carrera 4
911 Turbo (Model Year 1991)
Concern: Radio interference (whistling) from alternator.
Figure 1
Repair Information: An interference suppression filter may be installed on the engine compartment fuse/relay board to alleviate this condition (arrow, Figure 1).
It is installed on all vehicles from production date:
November 15, 1990
VIN: WP0AB296 - MS 41 0989 - Coupe
WP0BB296 - MS 44 0438 - Targa
WP0CB296 - MS 46 1025 - Cabriolet
WP0AA296 - MS 48 0086 - Turbo
Service Information: When diagnosing radio interference complaints on earlier 911C2/C4 models, first check:
a. Cable routing. The connecting cable, radio to booster, must be routed away from battery plus cable (on shift console right side). Distance between both cables should be 30-40 cm.
Figure 2
Service Information (cont.):
b. Ground wire for booster. Disconnect ground wire from booster (term.1 - brown wire) install new 4 mm diameter wire and connect to ground point XX on seat cross member under the right seat.
c. Check ignition wires for correct routing and installation. Spark plug connectors must be tight.
d. Interference suppression filter and additional wiring harness (Figure 2) can be installed in 911 Carrera 2/4 prior to the VIN numbers on page one.
Work Procedure: 1. Disconnect battery. Remove heater duct in engine compartment and cover flange with a shop towel. Remove fuse relay board cover in engine compartment.
2. Unscrew carrier plate and housing from body. Remove housing.
3. Remove both wiring tie straps from back side of carrier plate.
Figure 3
4. Cut wiring protection sleeves for wiring harness leading to fuses approximately 10 cm and remove (Figure 3, arrow A).
Careful, do not cut wiring
5. Apply two layers of textile tape to edge of the carrier plate (arrow E, shaded area).
6. Install suppression filter between the two wiring plugs. Make sure suppression filter engages properly at the bottom; push against clip on filter to ease engagement. Route wiring harness leading to fuses under the engagement bracket (arrow B).
7. Connect new wiring harness (Part Number 964 645 901 00) to suppression filter 2 pin plug and 12 pin DME wiring plug.
8. Route voltage supply wire (Figure 3, arrow C) and connect with the supplied quick connector to one of the four red 2.5 mm diameter wires (arrow D). The distance between the suppression filter and the quick connector must be sufficient to ease installation of the carrier plate.
Figure 4
9. Reinstall housing and carrier plate.
Note: When installing carrier plate, make sure the plate contacts the stops on the housing (Figure 4, arrow F). To achieve proper installation, it may be necessary to pull both wiring harnesses approximately 3 cm towards the front (Figure 4) and to push bottom of suppression filter slightly towards the front.
10. Reinstall fuse relay board cover and heater duct. Connect battery. Perform system adaption, set clock and code radio.
Parts Information: Interference suppression filter: Part Number 964 645 011 00
Wiring harness: Part Number 964 645 901 00
Warranty Information: Installing suppression filter and wiring harness.Labor Operation: 9735190A
Damage Code: 9735400002
Time Units: 100
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10-26-2001, 05:24 AM
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Just a note-
My problem was exacerbated by noisy cables that were too close to the so-called "battery plus cable." I think they mean the postive lead connected to the battery
qoute:
"a. Cable routing. The connecting cable, radio to booster, must be routed away from battery plus cable (on shift console right side). Distance between both cables should be 30-40 cm."
My problem was exacerbated by noisy cables that were too close to the so-called "battery plus cable." I think they mean the postive lead connected to the battery
qoute:
"a. Cable routing. The connecting cable, radio to booster, must be routed away from battery plus cable (on shift console right side). Distance between both cables should be 30-40 cm."
10-27-2001, 03:23 AM
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That battery plus cable is the positive cable that runs from the battery, along the passenger floor of the car, near the trans tunnel, up and through the "bulkhead" area below the passenger side rear seat, and to the starter, I believe. I don't know if this a source for EMF or not. (964 and 993 anyway).
As far as the dreaded alternator whine on aftermarket stereo systems, this is always an interesting topic, since it involves really effective troubleshooting and you'll get so many opinions and theories as to its origin.
The odd part is, I just installed 5 systems in Porsches this last week, all of which involved amplifiers, and none of which had noticeable system noise of any kind. We've been using the Stinger twisted pair cable, because twisted pair cable has been the best at reducing noise. Before the twisted pair cable, for several years I used the basic black, gold plated, coaxial style RCA cables. I learned years back that the coaxial design is not good for automobile stereo installations because the inner and outer conductor tend to make any emf (electro magnetic field) interference much worse. The double and triple shielded (read: expensive) coaxial cables were worse, since the shield created more distance between the inner and outer conductor. A difference between the inner and outer can be simply carried through the cables as noise, and the amplifier doesn't know the difference between music and this noise, so it amplifies it all. (BTW, no amplifier, no noise, naturally.)
I was making my own twisted pair cables in systems where emf was a nasty force. You simply take a couple of lengths of 18 or 20 gauge wire (smaller works too) and twist them in a drill, then solder the RCA ends on them. Then the Stinger cables came along, and I've been using them with great results 99% of the time.
Now, as Jon Kaminsky is learning, there is also loop area noise. This is the difference between the two pairs of cables. You unplug one pair of cables, and the system noise is gone. The noise is related to the distance between the conductors in the RCA cables. If you have one cable that has all 4 pairs of conductors in it, each twisted pair, and no shielding between them, that is simply ideal in these situations where there is system noise. The problem with running two lengths of twisted pair cable is the distance between them. The shielding in each cable increases this distance. This distance is "loop area", and David Navone wrote a great article in the latest issue of Car Sound. I think Jon mentioned the forum online, another great source of information. Both Jon and Craig had trouble with their installations, and Lloyd and I failed to troubleshoot their systems over the phone. I'm more than thankful that both Jon and Craig have been so patient with us as we try to figure out why they are having noise in a system with amplifier and cables that we've used countless times before. Sometimes the head unit can also be involved, and it can be a ground potential issue with the head unit. If one set of RCA outputs has the same ground connection as the chassis and ground lead of the head unit, but another set of RCA/preamp outputs doesn't, then this difference, again, generates a signal that is amplified at the amplifier along with the music.
I'm humble enough to know that I don't know everything. I try one thing, then I try another. I love this business because there is so much to learn. I am a student of the things that I haven't figured out, and I'm a student of the feedback from our customers. I feel ashamed that Craig and Jon have had to spend *any* time troubleshooting system noise. I also agree that we, like many shops, tend to be not quite as open-minded as we could be, since we all have our own experience, previous results and cures, and the practice of doing similar installations literally hundred of times, sometimes on identical cars.
Whew! Sorry for the bandwidth. Questions, comments, feedback are always welcome.
Craig and Jon, I owe you guys both, big time. I'm here to serve.
-Rod Birch
As far as the dreaded alternator whine on aftermarket stereo systems, this is always an interesting topic, since it involves really effective troubleshooting and you'll get so many opinions and theories as to its origin.
The odd part is, I just installed 5 systems in Porsches this last week, all of which involved amplifiers, and none of which had noticeable system noise of any kind. We've been using the Stinger twisted pair cable, because twisted pair cable has been the best at reducing noise. Before the twisted pair cable, for several years I used the basic black, gold plated, coaxial style RCA cables. I learned years back that the coaxial design is not good for automobile stereo installations because the inner and outer conductor tend to make any emf (electro magnetic field) interference much worse. The double and triple shielded (read: expensive) coaxial cables were worse, since the shield created more distance between the inner and outer conductor. A difference between the inner and outer can be simply carried through the cables as noise, and the amplifier doesn't know the difference between music and this noise, so it amplifies it all. (BTW, no amplifier, no noise, naturally.)
I was making my own twisted pair cables in systems where emf was a nasty force. You simply take a couple of lengths of 18 or 20 gauge wire (smaller works too) and twist them in a drill, then solder the RCA ends on them. Then the Stinger cables came along, and I've been using them with great results 99% of the time.
Now, as Jon Kaminsky is learning, there is also loop area noise. This is the difference between the two pairs of cables. You unplug one pair of cables, and the system noise is gone. The noise is related to the distance between the conductors in the RCA cables. If you have one cable that has all 4 pairs of conductors in it, each twisted pair, and no shielding between them, that is simply ideal in these situations where there is system noise. The problem with running two lengths of twisted pair cable is the distance between them. The shielding in each cable increases this distance. This distance is "loop area", and David Navone wrote a great article in the latest issue of Car Sound. I think Jon mentioned the forum online, another great source of information. Both Jon and Craig had trouble with their installations, and Lloyd and I failed to troubleshoot their systems over the phone. I'm more than thankful that both Jon and Craig have been so patient with us as we try to figure out why they are having noise in a system with amplifier and cables that we've used countless times before. Sometimes the head unit can also be involved, and it can be a ground potential issue with the head unit. If one set of RCA outputs has the same ground connection as the chassis and ground lead of the head unit, but another set of RCA/preamp outputs doesn't, then this difference, again, generates a signal that is amplified at the amplifier along with the music.
I'm humble enough to know that I don't know everything. I try one thing, then I try another. I love this business because there is so much to learn. I am a student of the things that I haven't figured out, and I'm a student of the feedback from our customers. I feel ashamed that Craig and Jon have had to spend *any* time troubleshooting system noise. I also agree that we, like many shops, tend to be not quite as open-minded as we could be, since we all have our own experience, previous results and cures, and the practice of doing similar installations literally hundred of times, sometimes on identical cars.
Whew! Sorry for the bandwidth. Questions, comments, feedback are always welcome.
Craig and Jon, I owe you guys both, big time. I'm here to serve.
-Rod Birch
10-27-2001, 03:30 AM
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I just realized that I babbled on incoherently for a few pages worth of dribble without suggesting a cure for the loop area noise problem I was trying to explain.
We're trying to find a single cable, unshielded, with 4 twisted pairs for 4 channel connections from head unit to amplifier. I've got a lead on possibly Monster Cable, and there's a place called MIT out here near our store we're checking out. I know that I can take twisted pair wiring for home wiring and solder RCA ends on, but I'd like to find something professionally finished. Short of that (no pun...), I think that taping the two pairs of RCA's together, such as the Stinger twisted pair (which I wish were not shielded!) may help. Moving the RCA's further apart will likely increase the noise if it's loop area, whereas keeping the RCA's tightly together should reduce it.
Maybe Jon can share the brand and origin of his home style cable he used? Jon?
I'll try to check these boards more regularly, I receive the 911 digest and keep up on it regularly, but obviously I missed out on a hot topic on this board. doh!
-Rod
We're trying to find a single cable, unshielded, with 4 twisted pairs for 4 channel connections from head unit to amplifier. I've got a lead on possibly Monster Cable, and there's a place called MIT out here near our store we're checking out. I know that I can take twisted pair wiring for home wiring and solder RCA ends on, but I'd like to find something professionally finished. Short of that (no pun...), I think that taping the two pairs of RCA's together, such as the Stinger twisted pair (which I wish were not shielded!) may help. Moving the RCA's further apart will likely increase the noise if it's loop area, whereas keeping the RCA's tightly together should reduce it.
Maybe Jon can share the brand and origin of his home style cable he used? Jon?
I'll try to check these boards more regularly, I receive the 911 digest and keep up on it regularly, but obviously I missed out on a hot topic on this board. doh!
-Rod
10-27-2001, 06:29 AM
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Rod-
You don't owe me anything! I am very pleased with the results of your setup, and have had several compliments on the "OEM" look of the sub box. The carpet was a great match. Your statement of performing numerous installs without a hitch shows how different each environment can be. Also, *I* appreciate the time you guys spent with me on many many phone calls. I know most local dealers would have told me to bite it by then, or pretended not the hear the the noise, or push me into a filter.
The cable that solved the problem is just a 4-ft 4-strand radio shack special that went from my tape deck into my receiver in my home stereo. A real cruddy looking thing, it must be over ten years old.
EMI is not a trivial thing. At Intel where I work, minimizing EMI is a full-time effort in designing PC server systems- adjusting board trace lengths and routing, moving components around, power supply locations, peripheral locations, etc. We go to great lengths to design electrically quiet systems to maximize data integrity. In the presence of electromagnetic fields, cables and traces of any electronic system can act as receiving antennas and capture all kinds of rogue signals. Minimizing all this during design is not easy!
You don't owe me anything! I am very pleased with the results of your setup, and have had several compliments on the "OEM" look of the sub box. The carpet was a great match. Your statement of performing numerous installs without a hitch shows how different each environment can be. Also, *I* appreciate the time you guys spent with me on many many phone calls. I know most local dealers would have told me to bite it by then, or pretended not the hear the the noise, or push me into a filter.
The cable that solved the problem is just a 4-ft 4-strand radio shack special that went from my tape deck into my receiver in my home stereo. A real cruddy looking thing, it must be over ten years old.
EMI is not a trivial thing. At Intel where I work, minimizing EMI is a full-time effort in designing PC server systems- adjusting board trace lengths and routing, moving components around, power supply locations, peripheral locations, etc. We go to great lengths to design electrically quiet systems to maximize data integrity. In the presence of electromagnetic fields, cables and traces of any electronic system can act as receiving antennas and capture all kinds of rogue signals. Minimizing all this during design is not easy!
10-27-2001, 11:29 PM
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Hi Jon, (and everyone),
I really appreciate your patience through all of this, and the great integrity you displayed while commenting on a frustrating situation. Some people would have simply lost patience with us as we failed to fulfill our promise of "the system" as a "do it yourself" project. That kind of patience and persistence shows great "work" character, IMHO.
Everyone,
we appreciate all and any input. It is this valuable feedback that helps us to think "outside the box" (get it? subwoofer enclosures? boxes?),
and provides an opportunity to learn new things about "delivering" a superior product. From customer feedback I get the impression that we try harder than most places, but this little business has been my "baby" for the last 10 years now. 500 enclosures in the cars of happy Porsche customers. Man oh man, it's an absolute dream come true.
And then, our customers, you guys have just been so incredibly supportive and downright nice. Porsche 911 owners seem to be a group of primarily successful, well-adjusted, and appreciative of nice things. What great company to be in.
I apologize for the bandwidth. Allow me to continue.
Seriously, Jon, I'm happy to provide a refund on those cables. Ship them back and I'll pay for shipping as well. They're great cables I think 99% of the time. At 6 feet long each, they're not really useful in most mobile installations, 'far too short. They're probably not worth keeping unless you like the shiny Kryptonite ends. (There are far more expensive cables at $50 per pair as opposed to $24/pair, but all that shielding, they're no quieter than these in a noisy environment!
And Craig, I feel bad that we helped you swap out that amp, the noise was still there, and we were just this side of useless trying to help you locate and eliminate the source of noise. Geez. It sounds like you guys are both happy with the overall results, and that means a lot to us. Thank you again for your patience and persistence.
You rule.
-Rod
I really appreciate your patience through all of this, and the great integrity you displayed while commenting on a frustrating situation. Some people would have simply lost patience with us as we failed to fulfill our promise of "the system" as a "do it yourself" project. That kind of patience and persistence shows great "work" character, IMHO.
Everyone,
we appreciate all and any input. It is this valuable feedback that helps us to think "outside the box" (get it? subwoofer enclosures? boxes?),
and provides an opportunity to learn new things about "delivering" a superior product. From customer feedback I get the impression that we try harder than most places, but this little business has been my "baby" for the last 10 years now. 500 enclosures in the cars of happy Porsche customers. Man oh man, it's an absolute dream come true.And then, our customers, you guys have just been so incredibly supportive and downright nice. Porsche 911 owners seem to be a group of primarily successful, well-adjusted, and appreciative of nice things. What great company to be in.
I apologize for the bandwidth. Allow me to continue.
Seriously, Jon, I'm happy to provide a refund on those cables. Ship them back and I'll pay for shipping as well. They're great cables I think 99% of the time. At 6 feet long each, they're not really useful in most mobile installations, 'far too short. They're probably not worth keeping unless you like the shiny Kryptonite ends.
(There are far more expensive cables at $50 per pair as opposed to $24/pair, but all that shielding, they're no quieter than these in a noisy environment! And Craig, I feel bad that we helped you swap out that amp, the noise was still there, and we were just this side of useless trying to help you locate and eliminate the source of noise. Geez. It sounds like you guys are both happy with the overall results, and that means a lot to us. Thank you again for your patience and persistence.
You rule.
-Rod
10-28-2001, 12:12 AM
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oh man, it's me again. sorry.
'too many posts on this, but re-reading my first posts, something finally seeped into my brain.
Jon mentioned that his work involved circuit design and I think component placement to reduce noise in computers, for stable, clean, data integrity.
Porsche's TSB shows of a certain distance between the positive cable that goes to the starter (and perhaps a buss bar with more connections, to alternator perhaps...) and the wire for the factory stereo amplifier.
I defined loop area noise as noise created by the distance between the RCA cable conductors. What I obviously should have said is that this distance between the various conductors of the RCA patch cord tends to "pick up" EMF, or EMI, and these cables can become far more sensitive to the "noise" from other various components and wiring in the car. It looks like I was trying to say that the cables make the noise, but what I should have said was that the cables are more 'sensitive' to the noise from various sources.
Multiply the distance between the conductors (1 or 2 mm in unshielded twisted pair, as much as 7-9 mm in coaxial and/or shielded RCA's) between the two pairs of RCA cables, times the length of the cable for the total "distance" between the conductors. (If I've got that right). Less distance, less "loop", which is where perhaps the wires involved take on other qualities, just as wire wrapped around a magnet, and it's like a friggin' antenna or microphone to some degree. Add one amplifier to boost all of this noise, some good, accurate speakers, and 'voila! one noisy system. It's the distance between the conductors in each cable that causes us problems. The distance between 2 or more pairs of RCA cables adds to the effect dramatically. Single cable, 4 pair, all conductors spun in twisted pair fashion seems to be the cure. Unshielded. Shielding and also the coaxial RCA design appear to be just the worst at conducting this noise right into the amplifier's inputs.
Look at what works for the phone company, they just spin twisted wire together, and run it alongside power lines on poles. Those poles carry thousands of volts of AC, which by definition, has cycles. This isn't exactly the same environment, but I think it has similarities. David Navone also credits the phone companies for showing how unshielded twisted pair wire works best.
I'll stop now. This time for sure.
-Rod
'too many posts on this, but re-reading my first posts, something finally seeped into my brain.
Jon mentioned that his work involved circuit design and I think component placement to reduce noise in computers, for stable, clean, data integrity.
Porsche's TSB shows of a certain distance between the positive cable that goes to the starter (and perhaps a buss bar with more connections, to alternator perhaps...) and the wire for the factory stereo amplifier.
I defined loop area noise as noise created by the distance between the RCA cable conductors. What I obviously should have said is that this distance between the various conductors of the RCA patch cord tends to "pick up" EMF, or EMI, and these cables can become far more sensitive to the "noise" from other various components and wiring in the car. It looks like I was trying to say that the cables make the noise, but what I should have said was that the cables are more 'sensitive' to the noise from various sources.
Multiply the distance between the conductors (1 or 2 mm in unshielded twisted pair, as much as 7-9 mm in coaxial and/or shielded RCA's) between the two pairs of RCA cables, times the length of the cable for the total "distance" between the conductors. (If I've got that right). Less distance, less "loop", which is where perhaps the wires involved take on other qualities, just as wire wrapped around a magnet, and it's like a friggin' antenna or microphone to some degree. Add one amplifier to boost all of this noise, some good, accurate speakers, and 'voila! one noisy system. It's the distance between the conductors in each cable that causes us problems. The distance between 2 or more pairs of RCA cables adds to the effect dramatically. Single cable, 4 pair, all conductors spun in twisted pair fashion seems to be the cure. Unshielded. Shielding and also the coaxial RCA design appear to be just the worst at conducting this noise right into the amplifier's inputs.
Look at what works for the phone company, they just spin twisted wire together, and run it alongside power lines on poles. Those poles carry thousands of volts of AC, which by definition, has cycles. This isn't exactly the same environment, but I think it has similarities. David Navone also credits the phone companies for showing how unshielded twisted pair wire works best.
I'll stop now. This time for sure.
-Rod
10-28-2001, 03:22 AM
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That's right Rod. Yes phone line works great, and even inside a home with 60 cycle fields everywhere it meets its purposes nicely, not to mention multi-plexing other signals down the same wire with no problem such as like ADSL or other homes service. That's not to say that the floor for phone line quality parameters like jitter and SNR aren't fairly high, but only that for the requirements of the application, it usually works. But the more crap you hook up to your phone line (phone's , especially portable "radio" units, caller ID boxes, AD converters, etc. the more susceptible you are to noise. Do the presence of such items suddenly damage or lower the quality of the installed UTP phone line? No. But the line, properly tuned to their "noise" can broadcast it into your ear or your modem.
And don't forget the jillions of miles of CAT 5 UTP networking wire installed around the world. Yes- the cables themselves aren't the source of the noise. Its actually a question of whether they are going to pick-up the noise from the numerous sources in the vehicle.
Some people like noise however. I read somewhere about these clowns who get their kicks by installing illegally powered CB radios in their vehicles with dual or greater sets of alternators, batteries and whatever to power all this stuff. They go to shoot-outs much like the car stereo enthusiast contests. Anyway, some guy was filming one such event with a handheld video camera. One guy's super-power CB setup was held in great awe by the rest of the participants because when the guy with the camera walked by, the dude keyed his CB and the massive RFI generated from the CB caused the camera to eject its tape. Probably sterilizing everyone within 100 feet as well!
Thanks for the offer of the return Rod. I may end up doing some more experimenting with them (re-routing, cutting and soldering, etc.). But its nice to know that you'd do that.
And don't forget the jillions of miles of CAT 5 UTP networking wire installed around the world. Yes- the cables themselves aren't the source of the noise. Its actually a question of whether they are going to pick-up the noise from the numerous sources in the vehicle.
Some people like noise however. I read somewhere about these clowns who get their kicks by installing illegally powered CB radios in their vehicles with dual or greater sets of alternators, batteries and whatever to power all this stuff. They go to shoot-outs much like the car stereo enthusiast contests. Anyway, some guy was filming one such event with a handheld video camera. One guy's super-power CB setup was held in great awe by the rest of the participants because when the guy with the camera walked by, the dude keyed his CB and the massive RFI generated from the CB caused the camera to eject its tape. Probably sterilizing everyone within 100 feet as well!
Thanks for the offer of the return Rod. I may end up doing some more experimenting with them (re-routing, cutting and soldering, etc.). But its nice to know that you'd do that.
10-29-2001, 12:39 PM
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Hey Rod -- great to hear from you. Believe me, the stereo is the absolute s**t. Being a Porsche owner, I get more and more tuned to details, that's all...
Anyway, the noise on this system is a lot lower than the Kenwood was, and I've tried to forget it while the summer track days and home repair season was on me. I'll get back to the dubug later this year, and really have no hard feelings about the stereo. I'm pretty sure the last bit of noise is from the connects picking up emf on the way to the amp. But, I've been way too busy on other stuff to check it out.
For those of you tuning in to this semi-private conversation, let me repeat that Rod is a really class act, and his gear is incredible. I have no doubt that I have the best sounding Porsche in my neck of the woods. Whatever slightly irritating noise I have is probably due to my own lame self-install. If only I could have driven it to Cali and have the master do it... Maybe next summer.
Rod -- what about using CAT 5 for interconnect? Navone sounds kind of negative on it, and I was wondering about that stuff he patented..
Way off side note -- what do you guys think of the new systems Porsche/Bose will be putting out in 2002? Subwoofer cab in the rear deck, god knows how many amps? What are they doing, exactly?
Anyway, the noise on this system is a lot lower than the Kenwood was, and I've tried to forget it while the summer track days and home repair season was on me. I'll get back to the dubug later this year, and really have no hard feelings about the stereo. I'm pretty sure the last bit of noise is from the connects picking up emf on the way to the amp. But, I've been way too busy on other stuff to check it out.
For those of you tuning in to this semi-private conversation, let me repeat that Rod is a really class act, and his gear is incredible. I have no doubt that I have the best sounding Porsche in my neck of the woods. Whatever slightly irritating noise I have is probably due to my own lame self-install. If only I could have driven it to Cali and have the master do it... Maybe next summer.
Rod -- what about using CAT 5 for interconnect? Navone sounds kind of negative on it, and I was wondering about that stuff he patented..
Way off side note -- what do you guys think of the new systems Porsche/Bose will be putting out in 2002? Subwoofer cab in the rear deck, god knows how many amps? What are they doing, exactly?