Need help with a persistent Hiss
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0 Watt CAFz'r
Joined: Jun 2020
Posts: 1
Need help with a persistent Hiss
I am having a heck of time with a persistent Hiss issue in a new build. I will provide what I have in the system and what I have tried already:
Vehicle: 2013 Chevrolet Silverado
Head Unit: Kenwood DMX957xr
dual amp setup: Alpine MRC-F65 and Powerbass ACS-1000D
speakers: Alpine SPR-50C (2 sets) and Kicker CompVR Shallow Mount 12" (2x)
also included is a Maestro
Amp Power is straight from batter terminal (0 Gauge to the rear and then 4 Gauge to each AMP)
Ground for each amp are local ground posts (<12 inches) in the rear of the vehicle
HU Power is wired from fuse block under the hood
HU Ground is from ground post under the hood right off an engine block ground strap
I think that covers the basic setup. I connected everything up and I have a hiss coming from the 4 speakers (4 doors + 2 tweeters) being driven by the alpine amplifier. The hiss occurs without starting the engine, and it does vary with volume changes. Here is the list of things I have tried and their results/conclusion:
Vary the amplifier ground --> no effect on issue => Ground is probably good
disconnect RCA from HU --> small reduction on issue => could be RCA cables or AMP
disconnect RCA from Amp --> Completely removes Hiss => issue is not in the amplifier
swap RCA cable to higher quality and run through open air --> no reduction in hiss => not an issue with patch cable
disconnect second amp (Powerbass) --> no impact on issue => not a GND loop cause by second amp
Tie HU Acc+ to constant 12V --> no impact on issue => not dirty power from Acc
Connect phone to Amplifier via RCA cables/adapter --> no hiss at all => further re-enforces that Amp is not the issue
Disconnect Maestro unit --> no effect at all => not the maestro
Disconnect HU Antenna --> no effect at all => not the antenna
Move HU Power to Battery Terminal --> no effect at all => not dirty HU Power
Move HU GND to battery GND --> no effect at all => not bad HU GND
I can remove almost all the hiss by turning the gain on the AMP all the way down to its lowest setting (seems like this should not be necessary)
proper gain settings are: 110W per channel @ 4 Ohms per channel equates to ~20V output target which works out to about 2/3 gain on my amp (no numbers, just ticks)
All of this points me towards a potentially bad HU, but the HU is brand new and probably the highest quality component in my whole system.
Thoughts? What else can I try? Maybe something in my testing/conclusions is incorrect?
Vehicle: 2013 Chevrolet Silverado
Head Unit: Kenwood DMX957xr
dual amp setup: Alpine MRC-F65 and Powerbass ACS-1000D
speakers: Alpine SPR-50C (2 sets) and Kicker CompVR Shallow Mount 12" (2x)
also included is a Maestro
Amp Power is straight from batter terminal (0 Gauge to the rear and then 4 Gauge to each AMP)
Ground for each amp are local ground posts (<12 inches) in the rear of the vehicle
HU Power is wired from fuse block under the hood
HU Ground is from ground post under the hood right off an engine block ground strap
I think that covers the basic setup. I connected everything up and I have a hiss coming from the 4 speakers (4 doors + 2 tweeters) being driven by the alpine amplifier. The hiss occurs without starting the engine, and it does vary with volume changes. Here is the list of things I have tried and their results/conclusion:
Vary the amplifier ground --> no effect on issue => Ground is probably good
disconnect RCA from HU --> small reduction on issue => could be RCA cables or AMP
disconnect RCA from Amp --> Completely removes Hiss => issue is not in the amplifier
swap RCA cable to higher quality and run through open air --> no reduction in hiss => not an issue with patch cable
disconnect second amp (Powerbass) --> no impact on issue => not a GND loop cause by second amp
Tie HU Acc+ to constant 12V --> no impact on issue => not dirty power from Acc
Connect phone to Amplifier via RCA cables/adapter --> no hiss at all => further re-enforces that Amp is not the issue
Disconnect Maestro unit --> no effect at all => not the maestro
Disconnect HU Antenna --> no effect at all => not the antenna
Move HU Power to Battery Terminal --> no effect at all => not dirty HU Power
Move HU GND to battery GND --> no effect at all => not bad HU GND
I can remove almost all the hiss by turning the gain on the AMP all the way down to its lowest setting (seems like this should not be necessary)
proper gain settings are: 110W per channel @ 4 Ohms per channel equates to ~20V output target which works out to about 2/3 gain on my amp (no numbers, just ticks)
All of this points me towards a potentially bad HU, but the HU is brand new and probably the highest quality component in my whole system.
Thoughts? What else can I try? Maybe something in my testing/conclusions is incorrect?
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Natban
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Mar 24, 2011 03:22 PM
