Loud screech then POP sound when turn on and between changing radio stations etc.
Hey folks, joined up in hopes we may be able to get to the bottom of an ongoing saga around an audio system install going onto one of my motorcycles. Any input / guidance going forward would be highly valued and ever so much appreciated. Neither myself or my motorcycle mechanic who's taken on the audio install are much in the way of experienced with this stuff... it was a bit of a project he felt he could take on but we've hit a snag.. I have some theories which I'll get to later but haven't actioned them yet... first to explain the setup :-
1) Marine head unit - one of those 'velex VX230B' circular shaped headunits which has built in amp rated supposedly for 4 x 45W.
2) 2 speakers up front of bike mounted next to dash, 2 speakers at the rear mounted at the front of the topbox.
3) kenwood kac-m3004 compact marine 600w 4 channel amp located inside the rear topbox
4) kenwood ksc-psw8 'underseat' compact 8" subwoofer w/ built in amp in one of the side panniers
Okay, so here's the deal. At one point we had it where there was no separate amp for the 4 speakers and we were just running off the head unit's own built-in amp. When the setup was like this it was perfectly fine, no odd noises or issues of any kind! The only issue was I wasn't happy with the output at higher volumes and it begun to distort at 32+ volume (highest is 40) plus i didn't feel it was loud enough in all.
I decided to bring bike back to mechanic along with a kac-m3004 4 channel amp (as listed above) and have him re-route everything so the speakers passed through that.
The head unit does *NOT* have pre-outs - only high level speaker output. However the kenwood amp im now using states that it is designed to take in high level speaker output and deal with it so that shouldn't be an issue. It's good for 600w peak and 50w RMS per channel; in any case for a compact amp a DAMN SIGHT better power than the crappy built in one on the velex headunit. So he's done all the work using higher quality thick gauge speaker cables etc. and now to explain what the symptom(s) are :-
When turning on the bike's ignition, head unit fires up after a few seconds as normal, but then just before the radio (sound) kicks in there's a very loud, brief high pitched screech type noise followed by a POP, then the sound is ok after that. Turning off the bikes ignition does a very small pop (no screech sound) but isn't near as loud as the turn on pop.
Subwoofer setup in the side pannier is entirely unaffected and works fine! - No pops or noises at all from that. Remembering it also has its own amp built-in.
If while listening to the radio, i change station? that damn loud screech / pop occurs before playing the next stations sound. I tried with mp3s on a usb stick and same deal, loud screech/ pop when clicking to change track. Sometimes at random what also happens is after the loud pop, no sound will come out; head unit still on / playing the music but you cant hear anything anymore from the speakers. At first i thought it was because they got blown up by this behaviour but if i turn off bike's ignition, then turn back on, after the screech / pop the music returns to all speakers and plays. Perhaps the Kenwood amp has some sort of protection override after certain pops and shuts off the output to the speakers to protect them? but as i said, this doesn't happen all the time.
Things we tried. On the kenwood amp there are 'input sensitivity' dials for the front / rear channels. this had almost no effect whatsoever on the loud pop noise issue. We tinkered with the filter frequency dials just for the hell of it knowing that probably wouldnt make any difference with this kind of problem, and sure enough not.
One thing that was a real scare was when we switched on either the "low pass" or "high pass" filter setting... either of these settings causes an ongoing extremely loud run of POPOPOPOPOPOPOPOP sounds that are sure to destroy the speakers (and your ears) if you left it going for more than 5 / 10 seconds. Caused us to quickly turn off bike ignition then try the other filter pass which had the same effect. Only when setting filter to "OFF" for both the channels was everything okay in that regard. I thought this was a very odd symptom but must surely relate to the overall issue as regardless of how small diameter speakers you're using a filter pass shouldnt cause this to happen?
What I am thinking after trying to do some digging is that perhaps each time you change radio station / mp3 track on the usb stick, the built-in amp on the head unit itself goes off briefly, then back on - sending a rush of high level speaker power to the kenwood 4 channel amp and somehow causing a bit of a shit-fight. On that token, I considered if whether or not this problem would be mostly resolved by adding in something like an AERPRO AP3044A 4-CH fixed line output converter which changes up the high level line output from the headunit to low level before reaching the amp? I am a bit dubious about paying for one of these (even though they are pretty cheap) as the kenwood is rated to take high level line outputs..
Another thought is to delay when the kenwood amp turns on... by sticking something like a PAC TR-4 remote turn-on module to the kenwood 4ch amp which delays its turn-on by 1 second. Again i am a bit skeptical of this helping in this situation though as the loud screen/pop is occuring even when changing radio stations or mp3 tracks. No turn-on delay system is going to resolve that.
The only thing i can think that may possibly stop this is a bit of a 'work'a'round scenario which i'm sure a lot of you would laugh at and isn't really practical in the real world sense. To place a switch up on the dash somewhere that turns on / off the 4ch kenwood amp manually. So i would leave that switch turned off when turning on the bike / head unit.. then after thats all on, flick the switch on to the 4 channel amp and hopefully wont pop as the head unit is already up and running. The issue will be when the next track kicks in or i want to change radio stations, have to remember to flick the amp switch off before a song ends / back on when new one starts. Highly impractical and almost comedic!
HELP!!!!!
Re: Loud screech then POP sound when turn on and between changing radio stations etc.
Quote:
Originally Posted by
Ricochet76
What I am thinking after trying to do some digging is that perhaps each time you change radio station / mp3 track on the usb stick, the built-in amp on the head unit itself goes off briefly, then back on - sending a rush of high level speaker power to the kenwood 4 channel amp and somehow causing a bit of a shit-fight. On that token, I considered if whether or not this problem would be mostly resolved by adding in something like an AERPRO AP3044A 4-CH fixed line output converter which changes up the high level line output from the headunit to low level before reaching the amp? I am a bit dubious about paying for one of these (even though they are pretty cheap) as the kenwood is rated to take high level line outputs..
This is the most logical thing to try. If you have another source (iPod, phone, another radio), you can try feeding it into the amp first via RCA to verify that the amp isn't causing the problem. If you verify the amp isn't the problem, you can try using a line output converter or possibly shop for a new source.
Quote:
Another thought is to delay when the kenwood amp turns on... by sticking something like a PAC TR-4 remote turn-on module to the kenwood 4ch amp which delays its turn-on by 1 second. Again i am a bit skeptical of this helping in this situation though as the loud screen/pop is occuring even when changing radio stations or mp3 tracks. No turn-on delay system is going to resolve that.
This could only alleviate the screech and pop when the amp turns on, you'd still have the issue when seeking or changing tracks.
Re: Loud screech then POP sound when turn on and between changing radio stations etc.
Quote:
Originally Posted by
Euphonic
This is the most logical thing to try. If you have another source (iPod, phone, another radio), you can try feeding it into the amp first via RCA to verify that the amp isn't causing the problem. If you verify the amp isn't the problem, you can try using a line output converter or possibly shop for a new source.
Good move. I'll troubleshoot further by hooking up the phone to the amp's A then B channels and see if the issue continues on either of those. If it does, i'll move onto perhaps changing the location of the amp's ground and using a larger ground ring on the end of the wire (could this potentially cause it?). I've been told by someone it may be a 'ground loop' issue, but if that were the case I wouldn't expect the sound to work perfectly fine during normal listening after the initial POP and is only repeated when i change radio station or mp3 track. Am I right in my thought process on that?
So, if we're onto something here, this should hopefully save the day ? :-
https://www.alburyrcmodels.com.au/4-...evel-converter
