Prius High-Pitch Sound Post-Install


pokeyouindaeye

CarAudio.com Newbie
Jan 20, 2020
15
2
Vancouver, BC - Canada
Hi all,
Just installed a Kenwood KMM-X503, Hertz Hpower H604, Infinity 12" Kappa sub, and Polk DB6502+ component speakers in a 2006 Prius...
BUT
got a high-pitch sound coming-out of the component speakers that seems to relate to electrical.

- cuts-out when head-unit is off (or in standby)
- cuts-out when RCA cables (front pair) are disconnected from the amp
- cuts-out when car is sitting but on (i.e., not charging, regenerating, nor driving)
- volume adjustment does not affect it

I have tried:
- re-doing the ground on the amp = minor reduction
- re-running the RCAs along the roof, rather than alongside the floorboards (starting at the foot-well) = minor reduction

I haven't tried:
- re-grounding the head-unit
- different RCA interconnects

SO, my questions, if anyone is willing to help a fellow audiophile out:
- what would you try first?
- what's the story with single-end vs differential and how does that affect my next cable choice attempt (ref. "Truth about RCA cables" video); I'm pretty sure neither the amp nor head-unit are differential

Potential suppliers of cables aren't great in Canada, but want to be ready to try all means next time I open-up the dash and re-run cables.... if need be.

KnuKonceptz seems to have two options for highly shielded cables:
1. Karma "twisted coaxial, triple shielded"
2. Klarity quad-shielded twisted-pair

But also, would a simple coax-type RCA potentially solve this interference? (e.g. Monoprice premium 2x RCA)? My current RCAs are probably basic rubber-insulated, potentially not even twisted pair.... came from an iConnects install kit - link
 
OP
pokeyouindaeye

pokeyouindaeye

CarAudio.com Newbie
Jan 20, 2020
15
2
Vancouver, BC - Canada
Thanks @1aespinoza - I'm running 4 chan, ya. Both RCA pairs seem to carry the signal, as I tried putting the sub-out RCA pair into the front channel input on the amp and got the same noise issue. The sub doesn't carry it because of the filter, I guess?

I'll try grounding the radio chassis next, thanks for the tip!
 

Popwarhomie

10+ year member
Jan 22, 2010
8,496
1,367
FL
Unhook RCAs. Use RCA to 3.5mm jack and plug you phone into amplifier. If the noise goes away then it's either headunit or rca related.
 
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pokeyouindaeye

pokeyouindaeye

CarAudio.com Newbie
Jan 20, 2020
15
2
Vancouver, BC - Canada
Unhook RCAs. Use RCA to 3.5mm jack and plug you phone into amplifier. If the noise goes away then it's either headunit or rca related.
Thanks Popwarhomie, that did stop it... so I'm thinking to try a few things next time I pull it all apart:
- group loop isolator
- re-ground the head-unit direct to the chassis
- try grounding the head-unit chassis to the car chassis
- try grounding the head-unit to the amp (KnuKoncepts staff member recommended trying this)
- shielded RCA cables
 

1aespinoza

Junior Member
May 22, 2013
655
178
Pharr, Texas
Thanks Popwarhomie, that did stop it... so I'm thinking to try a few things next time I pull it all apart:
- group loop isolator
- re-ground the head-unit direct to the chassis
- try grounding the head-unit chassis to the car chassis
- try grounding the head-unit to the amp (KnuKoncepts staff member recommended trying this)
- shielded RCA cables
Also make sure rcas are fully inserted. If only center pin goes in, you will have sound but with a whine.
 
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pokeyouindaeye

pokeyouindaeye

CarAudio.com Newbie
Jan 20, 2020
15
2
Vancouver, BC - Canada
Update, I've tried a few more things:

1. snip the HU ground and go over-seat to the amp's ground terminal --> no change, or very minor change -- was a good 18awg copper run

2. move the ground to a chassis point --> no change, or very minor change -- but, wasn't screwed down, just held to chassis

3. try a diff. pair of RCAs over the seat --> no change, or very minor change -- but, these were basic RCAs, unshielded DJ, not twisted/shielded... however, run over the seats from an open dash, shouldn't that eliminate noise?

4. tried moving the amp a few more feet away from the hybrid battery --> no change, or very minor

Tried two different brands of group loop isolator in front of the amp... no change.

Hmmmm, didn't try:
- grounding HU chassis
- shielded twisted-pair RCAs (note: the HU is single-end output, the amp is differential input)


Any ideas?
 
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pokeyouindaeye

pokeyouindaeye

CarAudio.com Newbie
Jan 20, 2020
15
2
Vancouver, BC - Canada
Hello pokeyouinthaeye. Did you solve your issue? I am curious to learn what the solution was.
Shielded twisted-pair RCAs did not.

Haven't tried grounding the HU chassis yet. Also going to re-try ground loop isolator on the HU outputs, rather than on the amp inputs. Last resort is manually re-grounding the outer ring on the RCA outs of the HU to the HU chassis or some ground... seems ridiculous, considering this is a new Kenwood Excelon head unit.

I've tried everything, shouldn't be having this many issues... going after Kenwood for a warranty solution at this point. I highly suspect it's an internal circuitry bad grounding issue with the RCA outs.
 

1aespinoza

Junior Member
May 22, 2013
655
178
Pharr, Texas
I've tried everything, shouldn't be having this many issues... going after Kenwood for a warranty solution at this point. I highly suspect it's an internal circuitry bad grounding issue with the RCA outs.
You are right, it should not be this difficult to isolate. Since you already removed the rcas and the noise stopped, only the head unit is suspect. I had a similar problem with a Pioneer head unit, ended up just using one set of rcas to solve the issue.
 
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