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Old 12th July 2009, 12:50   #61
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Originally Posted by sdh View Post
What is that torroid next to the amp9 power connectors. I do not have it in the kit I got. Can you share the purpose and spec of the same.
Don't worry about that Yellow toroid. Its not part of kit. I just added it in series of power line to make sure that I block high frequency noise (if any). That anyway was precaution, and can be ignored safely.

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Originally Posted by ghpk View Post
Mishra ji,
How good are the Luxco Speakers ?
I see them in first page, and I think those are made in my town,
Do they compete with Those Branded Speakers in ICE market ?
THey are good for low-bass but are inefficient. Also they do not provide any specs so can not build a suitable box for them.

Those are not used for ICE but serving purpose for test bed. (Apply lot of power and get little audio) So WAF remains aceptable while testing.
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Old 16th July 2009, 14:52   #62
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Originally Posted by omishra View Post
I would like to thanks everybody for their support
now,

All below noises are gone now!

Hiss - this is taken care by reducing the input to my amp about 1/3 of output of HU - DAC output. At level 1 I can here only audio no hiss and at Max 50 now I reach upto amp saturation and distortion at very high SPL.

Whine - Aha! This was quite interesting problem. I got to know it from two angles. There was no ground loops.
1. Input cable replaced with another good shielded local cable and kept away from power lines. <- main part
2. Power and ground wires are replaced with 5mm thick multistrand Finolex cables. Additionally I put three tantalum capacitors in all power inputs of OEM HU (two X 1,uf/35V ) and one X 10,uf/35V for my amp power input.

Now I have audio with dark background, dead silence and clean audio, even tuner reception improved too.

Regards,
I have also installed this amp (my second one. The first one blew for some reason) along with my car computer. I am getting alternator noise and slight crackling sounds when amplifier inputs are muted. Can you help me resolve the issue. I will be replacing the input calbe between pc and am with a better quality one. Any other changes you propose. The other amp I will check as proposed by you.
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Old 16th July 2009, 17:51   #63
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I did a quick check in the afternoon. With the computer feeding the amp, there is alternator whine. I just removed the stereo jack from the computer and connected it to my phone and the whine was gone completely. So my guess is that the AGND of the amp is getting connected to the GND of the amp because the computer is passing GND via the ground of the streo plug as computer and amp share the same power supply. Now the question is how do I isolate the audio output from the computer.
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Old 17th July 2009, 11:23   #64
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Originally Posted by sdh View Post
I did a quick check in the afternoon. With the computer feeding the amp, there is alternator whine. I just removed the stereo jack from the computer and connected it to my phone and the whine was gone completely. So my guess is that the AGND of the amp is getting connected to the GND of the amp because the computer is passing GND via the ground of the streo plug as computer and amp share the same power supply. Now the question is how do I isolate the audio output from the computer.
audio output from the computer is balanced or unbalanced? I mean does it contain ground as return path which is getting connected to AGND?

Look at these facts.

1. Amplifier PGND is connected at only one place to ground i.e. along with power supply (does not connect to chassis).

2. Amplifier AGND is connected only to referrenace at output of source and does not short to chassis ( check at RCA jack's body grounds)

3. AGND, PGND and chip GND is not connected to chassis or does not have interconnect elsewhere.

4. Chassis to Chassis connect through metal bodies only.

5. All power sources are clean, I mean amp power source is as clean as input source's PS. It may be case that you are injecting whine from Amp PS towards source. I used ferrite bid + above mentioned filter caps for that purpose only. Wind 1 meter of 16 SWG (0.75mm) wire over 15mm inner diameter toroidal bid. Meterial is not specific ( take out from old PSU of SMPS)
Regards

Last edited by omishra : 17th July 2009 at 11:28.
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Old 17th July 2009, 12:32   #65
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I have following in a single box:
1 DC-DC PSU
1 Mother board
1 Amplifier
1 HDD
1 LCD.

The power is fed via the ISO head unit connector to the system. Powe and ground are split and one set goes to the DC-DC PSU and the other goes to the Amp.
Since Amp mounting points are not grounded, they do not connect the GND for the amp to the chasis. But since the DC-DC PSU or the computer mounting points are grounded, the amplifier ground actually gets grounded to chasis.

At the same time the audio output of the computer carries this ground signal to the amplifier and in the process shorts AGND and GND of the amp.

I cannot avoid grounding of the PSU and computer mother board to chasis as the mounting points are with ground contacts.

The only point now is how to avoid the AGND and GND of the amp getting sorted via the audio connector.

The PSU is not causing interference as I have shielded that part after I heard some noise on the workbench.
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Old 17th July 2009, 12:56   #66
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Then buy some audio transformer (acting as ground isolaters) for input. Please look at audio sections of this forum.

Example - http://www.team-bhp.com/forum/538907-post19.html

You have to find something like this. Neutrik - Audio - Transformers

Just take care to maintain signal in phase always.

Last edited by omishra : 17th July 2009 at 12:59.
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Old 17th July 2009, 13:01   #67
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If I put a beed like L5 in the schematic on the ground line from the audo connector will it resolve the issue. L5 is used to separate GND and AGND on the amplifier.
Are these audio transformers locally available.

Last edited by sdh : 17th July 2009 at 13:06.
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Old 17th July 2009, 13:04   #68
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If I put a beed like L5 in the schematic on the ground line from the audo connector will it resolve the issue. L5 is used to separate GND and AGND on the amplifier.
No, I don't think so. This will not avoid ground loop at that fequency. This is only for isolating switching noise. Also it will come in audio signal's return path.
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Old 4th September 2009, 00:48   #69
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Gr8 is the word buddy.
I am myself an equal electronic geek but what u have done is terrific.
Keep it up.
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Old 28th June 2012, 12:06   #70
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Default Re: SX4 OEM HU: By pass surgery for Amp section

Omprakash, Great stuff. I have one problem and maybe you could help. I use an IPOD dock connected to my HU. However when I connect the power cable to the dock, I get the alternator whine. Because of this I cannot charge my ipod while I am playing that in my vehicle. How did you eliminate the alternator whine.
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Old 6th July 2012, 19:14   #71
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Default Re: SX4 OEM HU: By pass surgery for Amp section

Hi Manavendra thanks,

As far as I see, you are providing power ground to IPOD which is source and this power ground is adding whine. Using isolation transformer between HU and IPOD doc could solve the problem provided IPOD itself is not complaining about whine.

I am not sure about charger but that should eliminate the whine by good filtration.
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Old 23rd December 2012, 17:12   #72
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Default Re: SX4 OEM HU: By pass surgery for Amp section

Great stuff Omishra! Can you please help me out with a basic query!
I am planning to attach a two channel AMP and a pair of subwoofers to OEM stereo. Can I use the two RCA inputs as the input to PreAMP or will I have to cut the rear speaker wires to get the input?

Putting them to increase the bass response, hope this would increase the Thump. Would it be okay to just connect the AMP directly or put some converter connector also in between?
Also if the Amp power supply is directly connected to the battery terminal, the amp will have power all the time even if the car is turned off? Is there any other place where I can connect it so that it gets switched on, once I turn on the ignition...
Too many questions, but again that is the power of T-bhp
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Old 24th December 2012, 12:37   #73
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Default Re: SX4 OEM HU: By pass surgery for Amp section

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Originally Posted by s10 View Post
... I am planning to attach a two channel AMP and a pair of subwoofers to OEM stereo. Can I use the two RCA inputs as the input to PreAMP or will I have to cut the rear speaker wires to get the input? ...
You require an OUTPUT from the HU to drive the subwoofers, not an input to it. So, you will need to connect the amp to the Pre-OUTs. If the HU doesn't have Pre-Outs, the only decent way is to use a LOC (Line Output Converter) connected to the Speaker Outputs of the HU. The LOC contains 4 RCA sockets (FR+FL, RR+RL).

BUT ... If you have not used an external amplifier for the front speakers (at least), adding only the sub will make the system sound worse than it does now. It will be difficult to tune the system to get balanced sound without the amp driving front speakers. Better to buy a 4-channel amp (costs ~30% more than the 2-channel one) instead of a 2-channel amp

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Originally Posted by s10 View Post
... if the Amp power supply is directly connected to the battery terminal, the amp will have power all the time even if the car is turned off? Is there any other place where I can connect it so that it gets switched on, once I turn on the ignition ...
There is a Remote Turn On signal provided by the HU (will be mentioned in the connection diagram on a sticker pasted on the HU). This signal (it is connected to the Remote Turn On input of the amp) commands the amp to go on when the HU goes on, and off when it goes off - even with the power coming directly from battery to the amp. The HU takes the turn-on command from the ACC signal that comes to it from the Ignition Switch.

The installer who will install your amp will know how to connect it.

Last edited by DerAlte : 24th December 2012 at 12:44.
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Old 4th January 2013, 11:05   #74
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Default Re: SX4 OEM HU: By pass surgery for Amp section

thanks a ton DerAlte for your inputs...

Quote:
You require an OUTPUT from the HU to drive the subwoofers, not an input to it.
Yes, I meant that only. I have done it as myself as DIY
I attached a Sony Xplod XMGTX6021, it's a 2 Channel Amp. In SX4 OEM stereo, RCA output is available so I didn't have to cut any wires/ put any converter to attach.
But after listening to the output as you suggested also I feel that I should have bought a four channel amp.
Now to tune it I am thinking of disconnecting the OEM rear speakers (as the RCA seems to of RR + RL speaker channels) and putting the volume setting more for rear.
What's your expert opinion ?
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Old 4th January 2013, 12:47   #75
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Default Re: SX4 OEM HU: By pass surgery for Amp section

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... Now to tune it I am thinking of disconnecting the OEM rear speakers (as the RCA seems to of RR + RL speaker channels) and putting the volume setting more for rear. ...
No, don't disconnect rears.

If there is only one pair of RCAs, they correspond to the stereo signal directly. FL+FR and RL+RR is split later internally. If there are 2 pairs, they will correspond to FL+FR and RL+RR. Putting volume setting more towards the rear will cause the image to shift backwards - not good for listening.
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