[tajender]

Dear BHPians,

I own a Tata Manza Saffire Aura. The stock ICE setup, though OK, lacks on details. So I decided to upgrade the same. The ICE installer took me to a guy in Rajouri Garden who runs Kenwood and Nipon service center and that guy in turn made a few soldered contacts on the stock Manza system to get the RCA connectors for Pre-Amp output and Remote turn on lead soldered on the circuit board of the HU itself and when we tested it on bench, it sounded awesome, no distortion or humming etc whatsoever.

Then came the time to test the waters, the HU was put back in the car and wired all well using wiring kit from Fusion, RCA cables running on one side and power cables on the driver side. Had my JBL GTO1004 connected to pioneer 6993 and JBL CS1204B bass box and the system was turned on and tuned. It sounded very nice, way better than the stock would. I came boom booming back to my home and turned the ignition off and as I removed the key came a pretty high pitch pop sound. Tried it again and the sound was there. I consoled myself and thought of living with it and just then I noticed that whenever I turn the volume all the way down on the HU, there is a audible distortion from the PIO 6993s. If I try to reverse the car with 0 volume, I get sound from reverse buzzer of the central locking kit from the speakers too, though pretty bleak, its there.

Now the troubleshooting started.
--Removed the RCA cables from amp, no distortion what so ever.
--The distortion sound and gain from central locking hooter is there even when the engine is off.
--Removing the RCA cables for channel 1 and 2, to which the PIO coaxials are connected removes the humming completely.
--When the engine is cranked, we get to hear the alternator whine too which varies with acceleration.
--Routed a new RCA cable from HU to Amp for speaker connections, without touching any of the metal parts of the vehicle. The issue still persists.
--Sanded the area where the amp is grounded, Issue persists.
--Amp is not touching any metal at all.
--Swapped the RCA cables from speakers to the ones on Sub channel. Issue persists.
--Swapped the speaker output channels. Issue still persists.
--Created a fresh ground for the Amp. Issue still persists.

The only thing that I guess is remaining is the installation of noise filter/suppressor. Which my installer is not recommending as that may reduce the gains too but I will do that if needed. Regarding the pop sound on turning the HU off, my installer has suggested installing a cutoff switch on the Remote/Antenna lead and switching the AMP off before HU. What do you guys suggest on this>

Please give suggestions on further course of troubleshooting this issue. Any help would be highly appreciated.

[DerAlte]

1. Ask the gentleman to use GOOD SHIELDED CABLES in the HU wherever he took out the connection from. He should be able to identify a ground track in the HU and and connect all the shields to ground

2. Get the amp grounding checked

[navin]

Originally Posted by tajender

Had my JBL GTO1004 connected to pioneer 6993 and JBL CS1204B bass box and the system was turned on and tuned. ...as I removed the key came a pretty high pitch pop sound.:...I get sound from reverse buzzer of the central locking kit from the speakers too, though pretty bleak, its there.

--When the engine is cranked, we get to hear the alternator whine too which varies with acceleration.
--Routed a new RCA cable from HU to Amp for speaker connections, without touching any of the metal parts of the vehicle. The issue still persists.

Regarding the pop sound on turning the HU off, my installer has suggested installing a cutoff switch on the Remote/Antenna lead.

The remote antenna lead is powered and hence you will get a pop sound. Most stock HUs do not have a passive remote lead. Maybe that cutoff switch is your only option.

Engine whine is a sign of poor sheilding. Since the wires are soldered at the HU end I would suspect that that end is not well sheilded. Try and shield that connection using aluminum foil (do not short anything so line one side of the foil with paper to test).

[yogeshnaik]

Fitted GTO1004 in my Vista. Head Unit is Pioneer 6050UB. When volume is low I hear a hiss from speakers (Heard only when ears are close to speakers). Secondly, when I turn the AHU off, after 1 second the amp gets off which is normal, but I hear a slight audible pop (tupp) sound from the speakers. Since the amp from JBL is of high quality, is this an expected behavior?

Any solutions to this? Thanks.

[nitinbose]

Check for the RCA leads, there could be a loose connection somewhere. Make sure there are no wire strands between the negative and positive RCA contacts, causing a short. The RCA wires could also be fake! I've had similar experiences. You may also try noise suppressors. Also make sure the RCA negatives are not grounded to the chasis. This always brings in all sorts of noises.


Finally as for the pop up heard when shutting down, does the stock HU have a remote connection - maybe not, this means the amps could be turning OFF with the ignition, causing the POP.

[DerAlte]

Originally Posted by yogeshnaik

... hiss from speakers (Heard only when ears are close to speakers). ... slight audible pop (tupp) sound from the speakers. ...

The two problems are related, and both are linked to a faulty amp ground. Get the ground connection of the amp redone, this time with some proper scrubbing down to bare metal around the hole. Or use copper / brass washers if using existing bolts.

Also, search the ICE forum for PioneerHU-specific noise problem. The effective solution is to wind a bare copper strand around the outer shell of all the RCA sockets on the HU, and connecting it to the nearest screw on the HU body. There are pics of how that has been done.

Originally Posted by nitinbose

... make sure the RCA negatives are not grounded to the chassis. This always brings in all sorts of noises. ...

At least one side of the 'negative', which is the screen / shield really, needs to be grounded for EMI shielding to be effective. It is when neither end is grounded does one starts getting interesting sounds injected into the signal - EMI interference. In short runs as in an automobile, both sides can be grounded without any adverse effects. In longer runs, as with microphones and guitar pickups, only one side can be grounded anyhow - since the other side is always floating.

You are right about the RCA cables, but issue is not of 'fakes' (fakes of what???). In some cables (even from known brands), the shield is sparsely wound. The better ones have shielding comparatively densely wound. That is the difference between good and bad RCA cables.

[yogeshnaik]

Originally Posted by DerAlte

The two problems are related, and both are linked to a faulty amp ground. Get the ground connection of the amp redone, this time with some proper scrubbing down to bare metal around the hole. Or use copper / brass washers if using existing bolts.

Also, search the ICE forum for PioneerHU-specific noise problem. The effective solution is to wind a bare copper strand around the outer shell of all the RCA sockets on the HU, and connecting it to the nearest screw on the HU body. There are pics of how that has been done.

At least one side of the 'negative', which is the screen / shield really, needs to be grounded for EMI shielding to be effective. It is when neither end is grounded does one starts getting interesting sounds injected into the signal - EMI interference. In short runs as in an automobile, both sides can be grounded without any adverse effects. In longer runs, as with microphones and guitar pickups, only one side can be grounded anyhow - since the other side is always floating.

You are right about the RCA cables, but issue is not of 'fakes' (fakes of what???). In some cables (even from known brands), the shield is sparsely wound. The better ones have shielding comparatively densely wound. That is the difference between good and bad RCA cables.

Thanks Nitin Bose & DerAlte for your high info replies. Your points with respect to the RCA cables is correct. I and Sachin's Auto Shop owner (Suraj) had done some joint debug at their Koramangala workshop. Here is some outcome.

Remote wire is connected through AHU. I saw the wiring carefully and after analysis when the amp goes off, I found the delay was less (approximately < 1 sec). I notified this to the JBL amp installer owner of Sachin's AutoShop (known to me since years). He asked me to drop in as he wanted to inspect himself. After analyzing there, we found the noise was through rear speakers only.

I asked him if a delay circuit (a capacitor + relay circuit) would help. He also advised to connect copper wires running through all the ground terminals of the amp's RCAs. Surprisingly, this worked!

The fitters had removed externally connected ground/earth wires bolted to the body of the Pioneer DEH6050UB AHU (Double DIN), this was noticed by the shop owner during the amp install but we did not ask the fitter to replace the wire thinking that the Pioneer manufacturers would have internally connected PCB ground to the AHU body.

The pop sound is gone with increasing the complexity with a burden of a delay/relay circuit for the remote wire to amp and copper wires running through all the GND terminals of the AMP's input RCAs.

Although the RCA cables are of high quality, this is a mere EMI issue due to improper grounding of the shields of the RCAs. I doubt connecting the GND terminals of the RCAs would not decrease the dB of STEREO seperation.

[DerAlte]

Originally Posted by yogeshnaik

... I doubt connecting the GND terminals of the RCAs would not decrease the dB of STEREO seperation.

No, it won't affect the stereo separation.

[yogeshnaik]

Originally Posted by DerAlte

No, it won't affect the stereo separation.

It was a strange behavior from JBL GTO1004 amp today. The pop sound has re-appeared. This comes from rear speakers while the amp turns OFF after 1/2 second delay once AHU is turned OFF. RCA's are earthed, Delay circuit is fitted to remote wire. I believe 1) This could be the differential op-amp pair draining sink current through speakers 2) May be imbalance between differential amplifier circuit 3) Power capacitor drains faster.

[DerAlte]

Originally Posted by yogeshnaik

It was a strange behavior from JBL GTO1004 amp today. ...

Why did you introduce a delay in the remote path??? It serves no purpose w.r.t. your problem. The problem is to do with the amp itself, no matter if it switches off along with the HU or x.y sec after it.

The reason will be quite really very simple, so no point in over-analyzing it. Power capacitor? Do you have an external capacitor on the Bat line? If the cap drains fast, it will actually *alleviate* the problem.

Is it possible for you to borrow another amp to check whether the amp itself is the problem? Otherwise, you will need to take your amp to the JBL service center. If there is a leaky cap inside the amp (possible) discharging itself, the problem will repeat at the service center also.

[yogeshnaik]

Originally Posted by DerAlte

Is it possible for you to borrow another amp to check whether the amp itself is the problem? Otherwise, you will need to take your amp to the JBL service center. If there is a leaky cap inside the amp (possible) discharging itself, the problem will repeat at the service center also.

I spoke to the dealer, he agreed to check this with another amp (similar or different type) for pop sound. No power cap connected in parallel. My amp GTO1004 is absolete in the market now, how about going for GT5-S644? Form factor is small but GTO1004 is looks heavy old school build type when compared. This is one of the reasons and thought GTO1004 would be better than the new entrant, not sure please correct me if I am wrong.

[DerAlte]

You are right, but not on account of 'new entrant'. GT5-S644 cannot push large amounts of current through the speakers, as much as the 1004 can. When the music dynamics demand it, the amp should be able to keep up - this is a major difference between one amp and another.

Amps never go obsolete, unless they were made with custom parts. Even 40 year old semiconductor amps are around, and many valve ones older than that. Spares are sometimes difficult, but never impossible to find. 1004 is just a couple of years old.