[Flint Ridge]

kōbai-iro... Mine had that humm - white noise if you will, could not notice once turned up. However, that was not going to work. I had the input switch wrong I presume and turned the gain almost all the way down.

Verify that you do not have it on RCA. Seems like it should be 4ch - Speaker on the inputs.

 

[kōbai-iro]

Flint, I have the amp input set to 4 channel (I have the 4 Kicker upgrade door speakers and 2 dash tweeters) and Speaker. Front and Rear HPF are off. Gain I moved between roughly 8 and 9 o'clock.
I want to be on speaker level input and just have the amp input wires connected with RCA plugs to keep that function for later use if needed.
I saw your install post btw. I don't have a sub. You said you were having a loud hiss originally but that seems it was due to having the amp settings wrong. So after you were all done and liked the sound you had no hiss or noise at low or no volume in the background? My sound is a definite steady humming tone not a hissing fwiw. The next chance I get I will zero the gain down and go up from there and see what it sounds like. I've had the dash apart and things in and out so many times I can do this blindfolded. I think I have a permanent case of carpal tunnel though on my hands.

 

[Flint Ridge]

Correct, with volume down it is perfectly silent on mine, no hum, hiss or whatever it was.

And yes, you can use the rca connections. I just cut them off.

In hindsight I would not suggest the amp behind the head unit. If you go back in, lengthen the lines so you can put it where you can get to it.

 

[kōbai-iro]

Yeah in a perfect world the amp would be away from the dash and more accessible but there are very limited places for it in these vehicles, besides glove box or under the driver seat which I don't want. I'm going to try to find another grounding point for the amp behind the dash or maybe in the shifter console area- if that and adjusting the gain doesn't remove the noise I will re-wire the amp to the head unit power and ground wires. At least my head unit doesn't have 14 connectors like yours omg! It's bad enough with the few it does have.

 

[kōbai-iro]

Update: a new grounding point didn't eliminate the hum so I rewired the amp to use the head unit power and ground wires but still have hum- no change at all. When I zeroed the gains the hum was still there and when the gains were increased past 9 or 10 oclock position the hum level stayed the same but then hiss increased. I tried the amp's RCA setting instead of speaker but no improvement and a little worse hiss. Seriously nobody else with the non-nav CF625UM head unit and the Alpine KTP-445U amp (no subwoofer etc) can hear a background hum noise at no or very low volume with any source (AM/FM/USB/CD)??
If this is expected with the crappy head units we get stock with the Premium level ok so be it, I would hope an aftermarket head unit would produce a cleaner signal using RCA outputs if that's what I have to do to get no humming!

 

[EJH]

Update: a new grounding point didn't eliminate the hum so I rewired the amp to use the head unit power and ground wires but still have hum- no change at all. When I zeroed the gains the hum was still there and when the gains were increased past 9 or 10 oclock position the hum level stayed the same but then hiss increased. I tried the amp's RCA setting instead of speaker but no improvement and a little worse hiss. Seriously nobody else with the non-nav CF625UM head unit and the Alpine KTP-445U amp (no subwoofer etc) can hear a background hum noise at no or very low volume with any source (AM/FM/USB/CD)??
If this is expected with the crappy head units we get stock with the Premium level ok so be it, I would hope an aftermarket head unit would produce a cleaner signal using RCA outputs if that's what I have to do to get no humming!

OK. I have the 2016 so not quite the same HU. I have a different amp, but can tell you the HU in mine only puts out very low white noise, or hiss. I can only hear it with the engine off, volume high and no music playing. In reality, it is a non issue because it will never be heard. This is probably the 'hiss' you describe. If it increases with the amp gain, it is likely coming from the HU. Can you live with this hiss? It will be there regardless of the amp you use, since it is in the source signal.

The hum you have isn't coming from the HU. If it does not increase with the amp gain, the it is not in the source signal (the HU). This hum is coming from your amp. I don't know how much noise is to be expected with that little Alpine amp (it isn't a very pricy or high quality amp).

Assuming the 'hiss' is acceptable and the 'hum' is not, I suggest a new amp. If even the 'hiss' is unacceptable, then you need a new HU.

It is also possible the hum from your amp is due to power wiring, but it sounds like you eliminated that. I would still recommend a new amp be placed under the seat or in the trunk and grounded to a chassis bolt, not placed behind the dash.

Background on me: I'm an electrical engineer and have installed amps, subs, speakers, etc, etc in three or four of my vehicles, always keeping the stock HU (for anti-theft reasons).

Hope this helps some. Good Luck.:smile2:

 

[kōbai-iro]

EJH, thank you that helps a lot! I assume you have the new 7" touchscreen head unit. Have no clue if that has cleaner output than mine. Anyway hiss isn't an issue as it was only noticeable when I tried switching the amp's input setting from speaker to RCA and cranking up the gains beyond 10 oclock. I tell you without that pesky hum I really enjoy the sound I'm getting. It's the hum that is my issue and as I said it's steady at no volume and low volumes of radio (volume level 1 to 3) where I really notice it. As you may or may not be aware there is a wild difference between volume levels on the head unit depending if the source is switched to radio or CD or AUX/USB (I listen to most of my music on a thumbdrive). Radio is LOUD at "10" when that setting for CD/USB is not at all. Anyway I could live with the hum if it wasn't for the many times when I'm listening to radio at low volume (especially when parked with engine off) and there's that annoying background humming. When I power on the head unit when the volume is turned way down and I can hear it there is a very short pause before the hum kicks in- obviously the amp's "remote sensing" function has detected the head unit sending power thru the speaker inputs to turn it on.

Yeah the original power wire to amp was directly from battery and then I powered the amp via the head unit power and I tried to be careful about keeping power and speaker wiring separated, as well as trying two different ground points besides the head unit's factory ground wire. Yes the Alpine amp isn't that pricey (around $100) and something like the Pioneer you have seems like a good step up. [Update] But there doesn't seem to be a direct replacement for it in Pioneer's line-up- just the 100 w/ch 8604 model. All things being equal I would prefer retaining the factory HU but just get a little more punch and quality sound. If the Alpine powerpack had worked out I was fine with the it, the head unit, and the Kicker upgraded speakers for sound. I don't need a subwoofer. Hey thanks again.

So the 4 Kicker upgrade speakers I have say "50 RMS" and "100 Watts Max" on them, so for those in the know what power rating should I look for when looking for an amp to properly & safely drive them? (and the two Kicker tweeters in the dash). This Pioneer looks good http://www.crutchfield.com/p_130GMD8604/Pioneer-GM-D8604.html?tp=115 but I don't want more amp than I need either.
Crutchfield recommends running new wire to speakers if using a "high power" amp (100+ watts/channel) which I don't want to do so I guess an amp in the 60-75 watts/ch range would be good for my Kicker speakers and oem head unit? Update: these amps looks promising and small footprint:http://www.crutchfield.com/S-RSJf4hthWym/p_023EMA455/Blaupunkt-EMA-455.html and http://www.crutchfield.com/p_109GXA604/JBL-GX-A604.html?tp=35782

Thanks

 

[kōbai-iro]

Help please. Latest troubleshooting for the steady hum I'm hearing in speakers- I unplugged all the rca plugs on the input side of the amp (coming from the factory head unit) and the hum disappears. Of course the amp auto detects a signal from the head unit to turn on so I don't think unplugging the rca inputs determines anything like if the amp or head unit is causing the hum but what the hey. I have the head unit and amp and most of the wiring as far away from the dash as possible to minimize any interference issues. There was no hum until I added the amp but I can't figure out how to narrow it down to the amp itself or a noisy signal from the head unit being amplified. It is a speaker level connection which can be noisier than a low level rca one I realize that. Frustrating because I seem to be the only one with this hum who has a factory head unit/speaker level/Alpine power pack amp combo...:crying: I'd hate to get another better amp and find out that one is just doing the same thing and amplifying a crappy signal from my factory head unit. I'd prefer to keep the factory head unit if I can... Anyway if anyone has any further troubleshooting advice I'd sure appreciate it!

 

[EJH]

I don't think unplugging the rca inputs determines anything like if the amp or head unit is causing the hum but what the hey.

Exactly. The hum is from your amp, as stated in my reply a few posts above. Further troubleshooting would be to try another amp (borrow one if you don't want to buy one yet).

The hum you have isn't coming from the HU. If it does not increase with the amp gain, then it is not in the source signal (the HU).

 

[kōbai-iro]

Got you that it's the amp, thanks. Not sure why that didn't click in the old noggin from your first post, sheesh. Borrowing an amp really isn't an option for me but I will buy one that I can return just in case. Probably one of those I linked to at Crutchfield, like that Blaupunkt EMA 455 or JBL GX-A604 amps for example.

 

[Symmetrical]

Hey Kobai-iro, any update on this issue? Did you manage to fix it? I read this thread awhile back, and I was recently looking at amp install diagrams, and came across this - not sure if you've seen it or not:

Amplifier installation guide

About 6 paragraphs down the page, it lists the following:

"
The amp should be at least three feet from the receiver to avoid noise radiated from the vehicle's electrical system. The amp can also interfere with the receiver's AM/FM reception.
Do not bolt your amplifier directly to your car's metal chassis — that's inviting noise problems, like ground loops which hum or buzz. You could use rubber grommets around the mounting screws to isolate the case. Or you could mount the amp on a wooden board and attach that to the car body.
"

Is it possible this was the problem? Odd that it wasn't affecting anyone else's amps in the same location, though.

 

[kōbai-iro]

Thanks for the post but no never got rid of the hum so I'm done with the Alpine powerpack route. I posted about it on this other thread: http://www.subaruforester.org/vbulletin/f77/4-channel-amp-installed-now-i-have-questions-560737/
Eventually I think I will go with an aftermarket head unit. No external amp or subwoofer I just need a little boost in power and clarity which I think a 20+ watt/channel unit will provide. Just replacing the stock speakers and tweeters with the Kicker upgrades was a great improvement- especially the tweeters. Yeah I saw the Crutchfield amp install guide and a million other things elsewhere online while researching my hum issue and my install. The 3 foot rule shouldn't apply since everybody has installed that Alpine amp next to their head unit with no noise issues- in fact it is intended to be installed near the factory head unit behind the dash. Plus I never installed the two Alpine powerpack amps I tried to any metal behind the dash- they were just wedged in with the wiring and cushioned with thin rubber sheets I placed where it could touch metal. I just can't figure out what else the hum could be other than it occurs when the factory head unit is amped by the Alpine. Just to be clear the low hum I'm hearing is not an issue other than when the factory head unit is at very low volume or no volume at all, so maybe this isn't an issue for most people but it bugs me lol.

 

[stock stereo sucks]

I have a similar problem in a 2017 wrx sti sport (non-navigation)(canada) stereo model Clarion CV752CL. I upgraded the tweeters and door speakers to the kicker speakers, and installed an alpine ktp445u amp, using a forward/backward facing breakout harness. I had hum as well. It is high pitched. It does not appear right away, but after about 10 seconds after booting up. It is there when the audio is turned off as well. It is not proportional to the volume. It does not vary with the engine speed. I tried all the suggestions on crutchfield.ca for eliminating amp noise including grounding all the grounds to chassis, no effect. I installed a line output converter, and used the rca inputs on the alpine, and that helped a bit, but still the hum was there. I tried ground loop isolators on all 4 channels, but that did not help and made it worse. I tried disconnecting all the antennas and usb connections, and that did not help. I disconnected the rear speakers from the head unit and the hum disappeared from the rear speakers, therefore it is not coming from the amp itself or from the speaker wires being too close to the power wires.
Finally I realized that the hum disappeared when AM radio is selected! Therefore it must be a problem with the head unit. Also I notice that another hum is introduced when the brightness of the unit is not full or min. i.e. anywhere in between. I think I have deduced that the source of the hum is the crappy clarion head unit. Solution: get another head unit.

 

[kōbai-iro]

Update - I got a Kenwood Excelon DPX792BH last year and since I still had the Alpine KTP-445U I decided to see how it worked with the new head unit. Very well! No noise issues. The sound has a bit more oomph and presence not a huge amount but I knew that going in. It was just that pesky noise when the amp was hooked up to the stock Clarion head unit but that's gone now. So this time the amp and Kenwood are using the RCA connections and I downloaded some test tones to set the gains with instructions from Crutchfield.https://www.crutchfield.com/S-XhjG8eHM2UP/learn/setting-amplifier-gain.html
Used 100hz and 1 kHz tones, ended up with gains set just past 9 am. The powerpack is sitting behind and below the head unit and seems to have enougn air space back there, and it doesn't get that warm anyway. The amp is powered and grounded using the car's radio harness power and ground wires.