Sam's Surprise!!!

Vivekphadnis · 18th November 2005, 15:02

Will try reducing gain but can the cables introduce so much hiss?

Sam Kapasi · 18th November 2005, 15:21

Well, yes, cables can introduce some hiss. A high gain setting can amplifiy that too
You can also try warpping up the entire cable in silver foil and earthing that foil too. (if you're looking at saving some money)

Vivekphadnis · 18th November 2005, 15:25

The Boss interconnects are wrapped in foil but not the speaker and power cable of course. Should I try wrapping them in foil too? The hiss does not really make much difference to the sound I hear but I suppose we could do without it.

Sam Kapasi · 18th November 2005, 17:02

Nope. The audible hiss can only be introduced at line-level. I am assuming that you have run the power and the RCAs from different sides of the car.
What do you mean the RCA's are wrapped in foil? Did you wrap them? Because they dont originally come with an additional ground foil on them.
It should definitely reduce with the reduction in the input level of the amp.
Also try removing the RCAs altogether and check if the hiss is still there.

Vivekphadnis · 18th November 2005, 17:32

The power and remote turn on are on the left side of the car while the speaker and interconnect wires are on the right. I can see the foil wrapping on the wire as the insulation is clear blue. I bought these Boss interconnects from Sound Factor.

Sam Kapasi · 18th November 2005, 17:48

OK Vivek...

By foil, I meant an EXTERNAL foil wrap, over the insulation. Ordinary cooking foil, tightly wrapped over the insulation and grounded, this reduces external interferance.

Secondly: all this has been an assumption you mean "hiss" and not alternator whine.
Which means that it should exist with the engine turned off as well. Do you have a sound that changes with the revving of the engine, or an actual HF hiss with the volume at 0?

Autophile · 18th November 2005, 20:28

Vivek...change your RCA patch cables !!!!

Sam Kapasi · 19th November 2005, 13:28

lol JB yaar, he's just bought them. let's try and save him some paisa na!

Vivekphadnis · 20th November 2005, 08:29

The hiss is there even with the engine turned off. So it cannot be alternator whine. This is more like the tape hiss or white noise kind of thing.

JB, my mother has seen enough of wires for now. She is likely to kick me out of the house if I buy any more wires.

Sam Kapasi · 20th November 2005, 12:16

If the hiss exists in the car, with the car engine off, i do not think the fault is the RCA cables. Please disregard the silver foil suggestion.

The hiss is either generated from the HU or from the amplifier itself.

Simple confirmation, disconnect the RCAs from the amplifier side and listen again. If the hiss still exists, it is generated in the amplifier.
If the hiss goes away, when you disconnect the RCAs from the amp side, then it is generated from the HU. I assure you, that though cheap RCA's may pick up external interference, no RCA cable can generate a constant hiss.

In either case (Hiss generated from HU or from Amp) reduce the gain of the amplifier. Again, if the hiss is generated from the HU, reduction of the amp gain setting will immediately work.
If the hiss is constant and present even with the RCAs disconnected, then it's an amplifier fault. Either a design fault, or a particular piece fault. That can only be confirmed by replacing the amplifier.
My guess is that it is from the HU. Reduce the gain on the amp and it will be ok.

gkrishn · 20th November 2005, 15:36

Sam,
The hiss in my system comes up only when the EQ setting in the HU is selected. If i disable the EQ, the hiss goes off... does that mean, that it comes from the HU???
Thanks,

Sam Kapasi · 20th November 2005, 16:11

Quote:

Originally Posted by gkrishn

Sam,
The hiss in my system comes up only when the EQ setting in the HU is selected. If i disable the EQ, the hiss goes off... does that mean, that it comes from the HU???
Thanks,

Yes, unfortunately that does mean that the hiss is coming from the HU

gkrishn · 20th November 2005, 20:53

Quote:

Originally Posted by Sam Kapasi

Yes, unfortunately that does mean that the hiss is coming from the HU

Those EQ setting where crappy any way. Also that sony HU, just after the its 1st year, started skipping a lot. And it didnt read a lot of CDs which work properly else where.

I am actually happy that its the HU which is culprit, the rest of the system was brought much recently. Will get rid of it some time...

Sam Kapasi · 21st November 2005, 10:53

All head units have a reasonable amount of hiss. I guess this will depend upon the construction of the pre-amp circuit in the HU.
Some of us are sensitive to it and some not.
Please remember that the higher the gain settings on your amplifier, the higher chances you have of amplifying unwanted noise as well as the music.

Vivekphadnis · 21st November 2005, 13:02

I tried with the RCAs removed at the amp end. The hiss is still there.

I tried changing the gain settings. There is very little difference in the amount of hiss.

When I play a CD, I can hear the transport noises from the speakers when the volume is zero. The amp seems to be "faithfully" amplifying and reproducing every bloody kind of signal/noise. I suppose the hiss was there even without the amp and it is being amplified now.

My guess would be that the wires are picking up some noise. The speaker and RCA wires are running parallel to the Autocop security system wiring. Just below the steering wheel, the autocop thing is fitted and the RCAs run near it. Obviously, there is a power wire for the autocop. There could be something there.

18th November 2005, 15:02	#316
Vivekphadnis BHPian Join Date: Jun 2005 Location: Bangalore Posts: 690 Thanked: 2 Times	Will try reducing gain but can the cables introduce so much hiss?
	() Thanks

18th November 2005, 15:21	#317
Sam Kapasi Distinguished - BHPian Join Date: Jul 2005 Location: Mumbai (but wat Posts: 6,997 Thanked: 1,840 Times View My Garage	Well, yes, cables can introduce some hiss. A high gain setting can amplifiy that too You can also try warpping up the entire cable in silver foil and earthing that foil too. (if you're looking at saving some money)
	() Thanks

18th November 2005, 15:25	#318
Vivekphadnis BHPian Join Date: Jun 2005 Location: Bangalore Posts: 690 Thanked: 2 Times	The Boss interconnects are wrapped in foil but not the speaker and power cable of course. Should I try wrapping them in foil too? The hiss does not really make much difference to the sound I hear but I suppose we could do without it.
	() Thanks

18th November 2005, 17:02	#319
Sam Kapasi Distinguished - BHPian Join Date: Jul 2005 Location: Mumbai (but wat Posts: 6,997 Thanked: 1,840 Times View My Garage	Nope. The audible hiss can only be introduced at line-level. I am assuming that you have run the power and the RCAs from different sides of the car. What do you mean the RCA's are wrapped in foil? Did you wrap them? Because they dont originally come with an additional ground foil on them. It should definitely reduce with the reduction in the input level of the amp. Also try removing the RCAs altogether and check if the hiss is still there.
	() Thanks

18th November 2005, 17:32	#320
Vivekphadnis BHPian Join Date: Jun 2005 Location: Bangalore Posts: 690 Thanked: 2 Times	The power and remote turn on are on the left side of the car while the speaker and interconnect wires are on the right. I can see the foil wrapping on the wire as the insulation is clear blue. I bought these Boss interconnects from Sound Factor.
	() Thanks

18th November 2005, 17:48	#321
Sam Kapasi Distinguished - BHPian Join Date: Jul 2005 Location: Mumbai (but wat Posts: 6,997 Thanked: 1,840 Times View My Garage	OK Vivek... By foil, I meant an EXTERNAL foil wrap, over the insulation. Ordinary cooking foil, tightly wrapped over the insulation and grounded, this reduces external interferance. Secondly: all this has been an assumption you mean "hiss" and not alternator whine. Which means that it should exist with the engine turned off as well. Do you have a sound that changes with the revving of the engine, or an actual HF hiss with the volume at 0?
	() Thanks

18th November 2005, 20:28	#322
Autophile BHPian Join Date: Sep 2005 Location: New Delhi Posts: 931 Thanked: 2 Times	Vivek...change your RCA patch cables !!!!
	() Thanks

19th November 2005, 13:28	#323
Sam Kapasi Distinguished - BHPian Join Date: Jul 2005 Location: Mumbai (but wat Posts: 6,997 Thanked: 1,840 Times View My Garage	lol JB yaar, he's just bought them. let's try and save him some paisa na!
	() Thanks

20th November 2005, 08:29	#324
Vivekphadnis BHPian Join Date: Jun 2005 Location: Bangalore Posts: 690 Thanked: 2 Times	The hiss is there even with the engine turned off. So it cannot be alternator whine. This is more like the tape hiss or white noise kind of thing. JB, my mother has seen enough of wires for now. She is likely to kick me out of the house if I buy any more wires.
	() Thanks

20th November 2005, 12:16	#325
Sam Kapasi Distinguished - BHPian Join Date: Jul 2005 Location: Mumbai (but wat Posts: 6,997 Thanked: 1,840 Times View My Garage	If the hiss exists in the car, with the car engine off, i do not think the fault is the RCA cables. Please disregard the silver foil suggestion. The hiss is either generated from the HU or from the amplifier itself. Simple confirmation, disconnect the RCAs from the amplifier side and listen again. If the hiss still exists, it is generated in the amplifier. If the hiss goes away, when you disconnect the RCAs from the amp side, then it is generated from the HU. I assure you, that though cheap RCA's may pick up external interference, no RCA cable can generate a constant hiss. In either case (Hiss generated from HU or from Amp) reduce the gain of the amplifier. Again, if the hiss is generated from the HU, reduction of the amp gain setting will immediately work. If the hiss is constant and present even with the RCAs disconnected, then it's an amplifier fault. Either a design fault, or a particular piece fault. That can only be confirmed by replacing the amplifier. My guess is that it is from the HU. Reduce the gain on the amp and it will be ok.
	() Thanks

20th November 2005, 15:36	#326
gkrishn BHPian Join Date: Aug 2004 Location: Bangalore Posts: 584 Thanked: 39 Times View My Garage	Sam, The hiss in my system comes up only when the EQ setting in the HU is selected. If i disable the EQ, the hiss goes off... does that mean, that it comes from the HU??? Thanks,
	() Thanks

21st November 2005, 10:53	#329
Sam Kapasi Distinguished - BHPian Join Date: Jul 2005 Location: Mumbai (but wat Posts: 6,997 Thanked: 1,840 Times View My Garage	All head units have a reasonable amount of hiss. I guess this will depend upon the construction of the pre-amp circuit in the HU. Some of us are sensitive to it and some not. Please remember that the higher the gain settings on your amplifier, the higher chances you have of amplifying unwanted noise as well as the music.
	() Thanks

21st November 2005, 13:02	#330
Vivekphadnis BHPian Join Date: Jun 2005 Location: Bangalore Posts: 690 Thanked: 2 Times	I tried with the RCAs removed at the amp end. The hiss is still there. I tried changing the gain settings. There is very little difference in the amount of hiss. When I play a CD, I can hear the transport noises from the speakers when the volume is zero. The amp seems to be "faithfully" amplifying and reproducing every bloody kind of signal/noise. I suppose the hiss was there even without the amp and it is being amplified now. My guess would be that the wires are picking up some noise. The speaker and RCA wires are running parallel to the Autocop security system wiring. Just below the steering wheel, the autocop thing is fitted and the RCAs run near it. Obviously, there is a power wire for the autocop. There could be something there.
	() Thanks

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