16 replies to this topic

[peaandham]

G'Day guys im in some more need of help to rid my system of these pesky little noises. For starters I had an Alpine 9887 for my source and that was connected to my H701 via AI-Net (Analogue) at this time I was getting frustrated with noise throughout my system, one being a noise every time I turn the rotary control on my source unit and the other is a hiss type noise if you will. The hiss isnt full on and doesn't increase with revs but when I turn the system down fully I can hear the air like hiss and it really puts me off. It seems like its originating more from the front left Scanspeak Tweeter than anywhere else.

So any way tonight I fitted the 9861e I just purchased, I connected it to the H701 via optical output, turned the optical output option on the 9861e to "on" and its all still there, and if so the rotary noise is alot more present now then it was with the 9887.

Ive tried star grounding all the grounds in my car and that did nothing, I tried running the grounds from the Processor and Headunit straight to the battery and no change.

Any ideas?

Thanks
Luke

[Sorin-Andrei]

Processor?

[SQXPRT]

you sure the optical is working?

test:
whilst playing CD music, unplug the optical... music should stop coming out of the speakers.

If the above doesn't result in silence, then the optical is not working.

perhaps the amps are hissing?

[Damo95]

Is the head unit grounded at the same spot as the proessor?

Shouldn't be any noise when playing cd (only cd output is digital) from the h701...
My guess is the amp earths now...

Damo95 posting on iphone

[peaandham]

you sure the optical is working?

test:
whilst playing CD music, unplug the optical... music should stop coming out of the speakers.

If the above doesn't result in silence, then the optical is not working.

perhaps the amps are hissing?

Defiantly sure, I unplugged it first and nothing come out on CD, everything else was alright however.

Will the amps produce hissing through the speakers? That could be the case, im powering my tweeters and mids of an RE Class D amp, I will disconnect it and see what happens this, but im pretty sure last time I did that the noise was still there.

So Pulse-R, do you believe that optical should stop the Rotary control noise at least? Maybe a new cable? Because ive noticed this one doesnt fit in very tight, its loose fitting and doesnt take much to pull it out, however I would like to hear from someone else who has used the connection before.

Is the head unit grounded at the same spot as the proessor?

Shouldn't be any noise when playing cd (only cd output is digital) from the h701...
My guess is the amp earths now...

Yep same spot, earths ive tried time after time after time and then some more.

Edit: Just disconnected my RE 4ch that was powering the mids and tweeters and the hiss is still there :s

[SQXPRT]

Zipper Noise from the volume control usually indicates an earth potential difference between the different circuits in the system - i.e. H/U to Processor to Amps. Took me a few tries to get the earthing right.
If the sound come out with the optical connected, then it's fine. Nothing to do with noise.

The location of the earths is not as important as ensuring lowest resistance between them.

The scans are quite efficient, and may amplify the amp noise a lot. put some crappy (<90dB sensitive) tweeters in, and see if the hiss is still there.
maybe try adjusting the amp gains to see if the hiss gets louder - if not, then it's definitely the amps causing it.

[peaandham]

Zipper Noise from the volume control usually indicates an earth potential difference between the different circuits in the system - i.e. H/U to Processor to Amps. Took me a few tries to get the earthing right.
If the sound come out with the optical connected, then it's fine. Nothing to do with noise.

The location of the earths is not as important as ensuring lowest resistance between them.

The scans are quite efficient, and may amplify the amp noise a lot. put some crappy (<90dB sensitive) tweeters in, and see if the hiss is still there.
maybe try adjusting the amp gains to see if the hiss gets louder - if not, then it's definitely the amps causing it.

Thanks for the info I will look into all of it.

Firstly the tweeters, I plan to reset all gains and re-tune from scratch to I try to kill 2 birds with one stone perhaps.

Sorry for the Noobish question but what is a good practice to lower resistance between the circuits? Should I leave the headunit ground where it is (under the h/u) and then try grounding the h701 close to itself? Or could that cause ground loop issues using different locations?

[woodzyspl]

try grounding the rca's like people do with pioneer head units.. Or maybe its a factory ground playing up? just random ideas lol

[bobo333]

i get the clicking volume control noise on my 9887 too, its happened in every car/amp/speaker config ive used it in though so ive just put it down a trait of the head unit, since youve changed yours out now maybe its an alpine thing? theres too many other noises in the laser for me to check the alpine in that but i vaguely remember Ryzaas car doing something similar, ajs does the same thing too im pretty sure

Edited by bobo333, 08 May 2012 - 10:46 PM.

[peaandham]

Ok correct me if im on the wrong track, what im going to do is check the resistance of the bracket where my headunit and processor are grounded to, im going to do this by running a lead of 10 gauge wire from the battery to the interior so I can attach that to the negative probe of my multimeter and then put the positive lead of the multimeter onto the ground and check the ohm rating?

Now if I rub back some metal next to my processor and check the rating there and its better I will ground the H701 to that part of the chassis there and leave the headunit on its stock ground location?

[DrBoom]

_{May I suggest you try these to rectify your problem}

• Its a ground loop issue you ar dealing with here
  
• try to ground your RCA's as stated earlier on this thread, check with multimetre for resistance
  
• If you are using stock grounding, you may have to do a new ground for your head unit.
  
• Take your head unit out and bench test it to see if the hissing is still present, as it could be a head unit issue
  
• Check ground on your amp as well, with multimetre

Hope one of these should fix your issue...hopefully!!!

[TMM]

1. Remove the remote wire from your amp (so it doesn't power up) and power on the rest of your system. If the noise still remains, the speaker cables are picking up noise from something, try rerouting them on a different path. Routing them near ANY cables that carry a decent amount of current can induce noise, even ground cables for amps.

2. Hook the remote wire back up. Get some spare RCA plugs and solder the lugs together with a short piece of wire so the signal pin is shorted to the ground jacket. Plug them into into your amp. If the noise remains, the problem is the amp itself, or the grounding of the amp.

3. Hook the amp back up, and put your shorted RCA plugs into the inputs of the processor. If the noise still remains then it is the processor itself, or the grounding of the processor. If it goes away then it is the headunit or RCA cables coming from the headunit (already eliminated the RCAs in this case by trying the optical cable).


If i had to bet on it, i would guess the rotary noise is a ground issue at the headunit or just a design fault of the headunit. Keep in mind that rotary volume knob noise is normal when playing music as when you turn up the volume by 1 step it causes an instantaneous jump in the output waveform which is heard as an impulse/pop through the speakers. It shouldn't happen during silence though.

I'd also bet that the hissing is caused by your processor or amp and you won't be able to eliminate it without replacing the offending hardware for a completely different model.

If replacing your processor/amp isn't an option, what you can do to dampen the hiss is make an L-pad for your tweeters (possibly mids too if they also emit the hiss), about 5-8db is pretty effective, and turn up the gain on the amp to compensate. At -5db only 31% of the power from the amp is being sent to the speakers and the other 69% is emitted at heat from the resistors. At -8db it's 16% and 84% respectively. Use two 10watt resistors for each tweeter, two 50watt resistors for each mids.
Calculator for resistor selection:
http://www.sengpiela...ulator-Lpad.htm

If you get hiss from woofers then it's time for a new amp/processor as adding L-pads to woofers isn't practical (way too much heat from resistors, and kills your power output).

Sensitive speakers will make any hiss introduced in the signal chain more noticable.

Edited by TMM, 12 May 2012 - 12:21 AM.

[peaandham]

Didnt get much done today but I pulled the remote from the amp and the hiss was gone, so I replaced the remote wire and the hiss was back, tried grounding the rca's and that didnt help, swapped the RE amp with an Avantgarde amp but the noise was still there.

So now im thinking its a ground issue, however my multimeter doesn't seem to be able to get a steady reading so I can check resistance. At the moment the amp is grounding to the boot floor.

[SQXPRT]

might need to ground the amp near a chassis rail - child restraint bolts are good.

if the amp hisses with the RCA;s unplugged, then the amp is the problem.

The best ground for the processor is the closest one to where it is located. same with the H/U ground in the dash.

Really only amps have a high need for ground current flow.

[peaandham]

Ok so went out and pull the remote wire from my RE 4 Channel again, and the noise was gone, put remote back in and removed the rca's and the noise was back, try moving the ground to a seat bolt and noise was still there.

Now I will try grounding the H701 closer and find a new spot for my headunit, however I dont understand why when I tried another amp which was an A/B Avantgarde amp why the hiss was still there? Thoughts?

[VAUDii]

Hmmmm I have had a similar problem before with my own car! Big pain in the butt!!!!!!!

If the hiss is still present with the rca unplugged from the amp then id say it has nothing to do with the processor or head unit.

First Try re earth the battery to the engine and chassis.

Try running your power cable to the amp around the outside of the car.

Not sure what car you have but electronic acc pedals sometimes cause a bit of a hiss!

Make sure u match your amp gains to the processor.

next step id say maybe try the speaker wires.... (but hopefully one of the previous steps solves the problem!!)

Hope that helps!

[peaandham]

Ok well heres a bit of an update, I didnt like my 9861e, the interface was annoying and it was visually a let down compared to the 9887 and since the optical didnt work the way I expected it to. Also I grounded my h701 closer to it and tidied up some wiring in my boot (meaning some RCA's had to be altered in their run) but I started getting engine whine, so I swapped the 9861e out for the 9887, and voila no rotary noise, however the hiss was a little bit more noticeable, so the optical was doing something but not enough.

I've had engine whine before and gotten rid of it, Id like to put it down to the RCA's (which were the issues last time) but this time im thinking its because I grounded the h701 to the chassis instead of where the headunit was grounded, as this was engine whine free.

I also have 2 x 4 channel Rockford Fosgate Punch (old school ones) amps coming so they will be the real test of whether the current RE amp is the issue or not.

Fun, Fun and more Fun.