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Old 24th July 2010, 17:15   #1
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Default How to get rid of hissing noise from after market amp?

I recently upgraded the audio in my Tata Manza. As the stock HU doesnt have RCA out, the amp and subwoofer was wired with speaker level inputs. It is giving a very audible hissing noise ever since. All the sources, when played has the same level of noise, even when the engine is not running. My current set up is this.

Stock HU (Blaupunkt with BT)
Focal Solid 4 Amp
Infinity reference components (front)
DLS Oval performance 962 (rear)
Focal Bomba 20A1 sub woofer
After-market wiring (unknown brand)

After the install, I learned that it is quite normal to have a hissing noise if speaker level inputs are used. Since I don't want to change the look of the fascia by installing an after-market head unit, im thinking of using a Hi/Lo converter or a signal processor like the 3sixty.2, Phoenix Gold, Alpine Imprint or the JL cleansweep. How effective are these equipments in eliminating the noise coming from the HU amp? Or is there a more cost efficient product I can use? I don't require any sort of equalization, but just the elimination/reduction of the noise. And the cheaper it is, the better.
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Old 25th July 2010, 13:16   #2
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Sounds like the amp gain has been kept too high. Set the HU volume higher when you set the gain at the amplifier.

If this is a Blau HU, quite likely it will have Preamp out. Go to a Blau dealer, and you will be able to get the adapter cable. You need to buy RCA cables and try.
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Old 25th July 2010, 19:10   #3
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thanks. there is no RCA out present at the rear side of the HU. i will check with the dealer if a pre-out can be drawn using an adapter. The gain on the amp is set to 0 position and it still has the noise

Last edited by VEA : 25th July 2010 at 19:12. Reason: typo
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Old 25th July 2010, 19:24   #4
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Blau HUs don't usually come with RCAs out of the box. It is usually terminated in the first or third rectangular connector, and need an adapter to bring it out to RCA sockets.

Wierd! Gain set to 0 (it is not really 0 gain, it is minimum gain, i.e. expecting high input voltage) and still noise? Hmmm. Does the noise come when HU volume is set to 0? If so, try redoing the grounding of the amp.
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Old 25th July 2010, 19:56   #5
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Quote:
Originally Posted by VEA View Post

After-market wiring (unknown brand)
Here is the cause..

Upgrade power and ground to proper gauge (atleat 8 ga) of wiring from Finolex, Havells or L&T.
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Old 25th July 2010, 22:40   #6
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Quote:
Originally Posted by DerAlte View Post
Blau HUs don't usually come with RCAs out of the box. It is usually terminated in the first or third rectangular connector, and need an adapter to bring it out to RCA sockets.

Wierd! Gain set to 0 (it is not really 0 gain, it is minimum gain, i.e. expecting high input voltage) and still noise? Hmmm. Does the noise come when HU volume is set to 0? If so, try redoing the grounding of the amp.
I will try that. I'll call Tata Blaupunkt support too and see if i can get some information about it. Regarding the gain settings, it is set to 0 because at the moment it gives the least amount of hiss. No, there is absolutely no hiss when the volume is set to 0. But at 1, the noise appears. Do you know someone who can help me find the adapter?

Quote:
Originally Posted by panky12345 View Post
Here is the cause..

Upgrade power and ground to proper gauge (atleat 8 ga) of wiring from Finolex, Havells or L&T.
The power wiring is good enough i guess. It is probably 2ga from the battery to a splitter where one connection goes to the amp using a 6ga probably. Another wire goes to the active sub using a 6ga again i guess. I did not ask them which brand they used. I am more concerned about the quality of the speaker wires than the power cables.
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Old 26th July 2010, 09:00   #7
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Quote:
Originally Posted by VEA View Post
I recently upgraded the audio in my Tata Manza. As the stock HU doesnt have RCA out, the amp and subwoofer was wired with speaker level inputs. It is giving a very audible hissing noise ever since. All the sources, when played has the same level of noise, even when the engine is not running. My current set up is this.

Stock HU (Blaupunkt with BT)
Focal Solid 4 Amp
Infinity reference components (front)
DLS Oval performance 962 (rear)
Focal Bomba 20A1 sub woofer
After-market wiring (unknown brand)

After the install, I learned that it is quite normal to have a hissing noise if speaker level inputs are used. Since I don't want to change the look of the fascia by installing an after-market head unit, im thinking of using a Hi/Lo converter or a signal processor like the 3sixty.2, Phoenix Gold, Alpine Imprint or the JL cleansweep. How effective are these equipments in eliminating the noise coming from the HU amp? Or is there a more cost efficient product I can use? I don't require any sort of equalization, but just the elimination/reduction of the noise. And the cheaper it is, the better.
Hi Vea,

The hissing is natural since you're taking the speaker outputs and converting it to a lower level in your amp. The amp has the lineoutput converter which probably does this. The L/O converter consists of resistors, capacitors and inductors to reduce the speaker out levels.

Speaker output levels would contain much more noise than line out levels, hence even when you reduce the levels, the noise would be evident. The best choice for you would be to upgrade your HU. When you connect a speaker to the speaker output, the noise would be less evident, owing to the way the speakers (all speakers) work.
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Old 26th July 2010, 13:42   #8
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@nitinbose, the LOC is only a set of resistors. No caps or inductors, since they will suppress high or low frequencies, and the LOC is not supposed to do that.

Ask around in Kochi who is the Blau official distributor and contact them for the adapter.
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Old 26th July 2010, 18:32   #9
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I have checked with the Tata Blaupunkt help desk about the pre-amp outs. They confirmed that there is no pre-amp outs from the HU. That possibility is ruled out, or the help desk people are quite ignorant about their own products. I think i'll go ahead and try installing the Audio Control LC6i. Will I get a steering remote interface for tata cars? if then, I can think about a HU change.
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Old 26th July 2010, 18:52   #10
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Do you have the Part no. or Model number of the OE HU?
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Old 26th July 2010, 18:55   #11
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Quote:
Originally Posted by VEA View Post
After the install, I learned that it is quite normal to have a hissing noise if speaker level inputs are used.
No, it is not normal. There should not be any noise unless there is some fault.

Quote:
Originally Posted by VEA View Post
Regarding the gain settings, it is set to 0 because at the moment it gives the least amount of hiss.
This makes it obvious that there is definitely some noise that is being added to the signal somewhere along the cable path, which the amplifier is amplifying. Try routing the speaker cables that are providing the input to the amplifier from some other route that does not have any power cables running alongside, before doing anything else.
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Old 28th July 2010, 17:55   #12
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Quote:
Originally Posted by DerAlte View Post
Do you have the Part no. or Model number of the OE HU?
I have to remove the HU to check. Will be doing the same soon.

Quote:
Originally Posted by Bass&Trouble View Post
Try routing the speaker cables that are providing the input to the amplifier from some other route that does not have any power cables running alongside, before doing anything else.
That is something i should check. The power cable is running alongside the speaker wires that provide the input to the amp. The installers should have been careful about it. I thought it is ok since its a high level input and not low level RCAs.
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Old 7th August 2010, 02:39   #13
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VEA,

I believe Bass picked up the right point. The power cable running along ur speaker cables is bound to introduce some noise and with an unbranded cable it just increased the chances. try running the cables along different sides.

The other thing which u MUST do is get a Blau RCA adapter and if thats not available get a High to Low convertor which will allow RCA out for your amp.

Good luck.
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Old 7th August 2010, 12:16   #14
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There should not be any hum/hiss when connected to speaker level inputs. I am also using the same setup, powering the front comps and Sub from a 4 channel Amp with speaker level inputs to the front. Sub is connected by RCA. Even though the installer has routed the power cables and the signal wires in the same route, it’s making any hissing or hum sound even in higher volumes. Since the sound stage is good in front, if any distortion or hissing can be noticed easier. I am using Finolex 16 Sqmm cables to power the amp.

As B&T suggested try re routing the signal cables from the power cable path also check the grounding too.

Experts, Since from the volume level 1 onwards it’s audible can it because of a faulty HU?

Last edited by sajjt : 7th August 2010 at 12:17.
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Old 19th September 2010, 22:12   #15
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An update:

The wiring was done quite badly by the installer. There were a lot of joints and at some places it was joined with the stock wires. I have now changed the wiring to scosche and routed it through the other side without power cables. Again, an audiocontrol lc6i was installed before the amp. All these have made significant improvements. The hiss is barely audible now. I am happy with the results.
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