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Head unit distorts, even at low volume?

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Head unit distorts, even at low volume?

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So I just picked up this head unit last Friday (http://www.crutchfield.com/p_105KDHDR60/… and installed it. I fired up my test tone CD(and played a sine wave @ 1kHz, normalized to 0dbfs) and was only able to make it to about 40(of 50) volume before hearing distortion.

Now, the setup of my car is very non-standard. It's changed three times - each being an attempt to fix a problem:
At first I had a low level signal run direct from an Ipod to the trunk through RCA cables, but I had to crank up the gain on the amps so much that all of the interference and alternator whine was more prominent than my music. I can't tell if the phase distortion(mentioned below) was still there, as there was far too much interference to hear the fine details of the music.
To overcome the problem of all this interference, I installed an equalizer in the dash, which had a built in 20W RMS amplifier(normally you would connect your speakers to this.) I set it up to where the speaker level (high voltage) signal was going to the trunk(running through the same type of wire used for RCA cables - braided outside with a small wire inside) then through a line level converter(http://www.crutchfield.com/p_142SLC4/Sco… , and finally through very short wires into the power amp. This allowed me to keep the amplifier gain all the way down, maximizing the ratio of signal to noise. This setup was able to get extremely loud without distorting or having any interference. The down-side was that I was feeding the EQ/first amp stage with an Ipod(which is made to feed headphones), and the impedance mismatch was detracting from the clarity and frequency response of the sound - almost like phase distortion(some frequencies being slightly delayed more than others.) When using my laptop and an outboard sound device(M Audio FastTrack Pro) there was an obvious difference(well, obvious to me as an audio engineer) - but maybe that's because of the D/A converters themselves.

And thus I thought "Hey I should just replace the EQ with a head unit that plays MP3s and has a built-in D/A converter."
So I did, and much to my dismay, it sounds WORSE AND NOT AS LOUD as it did before. I attribute the loudness issue to the fact that I cannot turn the head unit up all the way without it distorting. The "Worse" part is the distortion itself - after all, what company would put out a $170 head unit that distorts before even hitting full volume?

To test the distortion, and rule out that any other component could be causing it, I turned the gain on the line level converter all the way down, and the gain on the outboard amplifier all the way down as well. I then turned up the head unit until I heard distortion(starts around 38/50 volume - totally unbearable past 42/50 volume.) Note that the sound coming out of the speakers was VERY very low in volume(since the amp gain was down,) but still distorted. Just to be sure, I turned up the gain on the amplifier, as well as the line level converter, and still heard the same thing - the same distorted sine wave, just a bit louder. The tone(harmonics) of the distortion did NOT change - which is a dead giveaway that neither of the two knobs I adjusted are even playing into, much less responsible for what I was hearing - they are just magnifying the distorted signal being passed through them.

So, at this point, I have a few ideas as to what could be causing this distortion. Bear in mind, I'm no electrical engineer, and these hypotheses could all be misguided:
1. The cables that carry the speaker level signal to the trunk (RCA cable wire without RCA connectors) are designed to carry a ground(zero reference) and hot(+) signal(unbalanced) and not two actively driven signals(+ and -). Possibly the difference in resistance, or higher than average resistance, between the two conductors of the cable are causing the head unit's amplifier to freak out as it is easier for it to push on one pole than the other. I doubt this is it, because the equalizer I had in there before was dirt cheap (no name Japanese product from a flea market) and did not have any issues. With that being said, maybe the EQ was so cheap that it did not have two actively driven terminals - and the cable was actually being used as intended - with a ground and a positive connector. I doubt this is the case, as the left front and left rear, as well as the right front and right rear shared a ground on the wiring harness - note that the front left and front right(or rear left/rear right) did NOT share a ground - only the speakers on the same side of the car did.
2. The head unit is expecting to see a 4 ohm load (a regular car speaker) but is instead seeing the resistance of the line level adapter, and is thus passing more(or less?) current than it is designed to - causing distortion. I doubt this is the case, as I wired up a 4 ohm 25w dummy load resistor across the + and - speaker wire, and did not get any different of results. I have yet to try hooking up a regular speaker to the head unit.

Tomorrow I am going to try connecting the HU directly to my speakers to see if the results are any different. If this reveals that the head unit is in fact not the sole source of the distortion, I will probably try running some "real" speaker wire.

Finally, if that doesn't work, I guess I'll just return this particular head unit, put my EQ back in, and use the money to get a mp3 player with a line out. I'm not too concerned with losing HD radio; After all, if I really want to hear Billboard's top 40 in 128kbps mp3(not to mention commercials,) I'll download them myself.

What do you guys think?

Verified Answer
  • I admit I skimmed through most of your post, but ....  I'm really not seeing too much what the problem is ....

    Most - if not all - aftermarket HU's will distort on the speaker level outputs at about 80% volume.  You should be able to set the volume at 80% and set the gain properly on the LOC and the amp and be fine.

    Ideally, you should be running RCA's without a LOC with that HU - is there a reason you aren't (other than you have it wired to a LOC previously and didn't want to run a long RCA all the way through the car) - Most HU's DO NOT distort on the RCA outputs.

    If you definitely don't want to run RCA's and don't want to have the HU distort when you turn it up - there is this from the HOR tab:

    Amplifier Gain Control: When you are using the KD-HDR60 with factory speakers (or those rated to less than 50 watts peak), the Amplifier Gain Control can limit the amount of power being sent to those speakers. When the Amp Gain Control is set to Low, the volume control ranges from 0 (minimum) to 30 (maximum). When using speakers rated higher than 50 watts peak, you can set the Amp Gain Control to High, and the volume control will range from 0 to 50. When all speakers in the system are powered by an external amplifier, the internal amplifier can be turned off.

    Seems like you could set that to Low and you would have to set the amp gain higher, but that would eliminate your problem.

    HPF settings in the HU would be nice (especially without an external amp), but doesn't the external amp have HPF settings?

    Your post was confusing b/c it sounded like you were running the iPod initially to an amp in the trunk - then to an EQ, and now directly to the speakers - not sure what amp was or is in the system.

    Also - the EQ was common ground on the left and right sides - the JVC is NOT.  You can't wire the negative leads together on the JVC - you can seriously damage the HU if you do!!!

    The above could be your problem - it is more likely than the wiring issues you mentioned, but I really think it is just that the HU distorts by design at about 40.

    Sorry if the reply got confused.

    Hope This Helps!!!

    Anyone else have suggestions?

     

    2002 Ford Focus JVC KD-A815 Sony CDX-GT410u Sony XT-100HD HD Tuner Stock speakers, no amp, no subs

  • The flea market amp does not have HPF settings?  Although without a subwoofer, that's not a great idea - but it would help - more below.

    Are you sure the flea market amp is more powerful than the JVC's internal amp?

    Eric1024
    The head unit isn't exactly distorting in the 5-60hz range, but these frequencies take up "space"(aka headroom) in the total signal that the amplifier will process - by removing them, it would leave more space for higher frequencies, and thus, other frequencies themselves can be amplified more without distorting. This is why the distortion went away when I turned the sub-bass all the way down - the same would have probably happened had I adjusted another EQ band - the idea is, you're turning down the volume at certain frequencies, and thus, you can turn the total volume up, so other frequencies can be louder, while the combined energy of the frequencies(RMS) stays the same.

    I agree and I don't agree.Devil  I will agree that bass takes more power to reproduce and filtering out the bass will allow you to play the speakers louder without distortion.  Where I disagree is that having HPF's in the HU would automatically allow the deck to channel it's internal power to other frequencies.  I don't think HU designers factor that into account.  Bottom line - I think whether you have HPF's in the HU, F-mod HPF's in the RCA's, HPF's in the amp, or bass blockers on the speaker leads, the end result is the same (neglecting differences in db/octave slope, etc.)

    Eric1024
    I wouldn't be trading in for another head unit, as I really only need the HU for mp3 playback - don't even use the radio or CD player.

    There's also fader and tone controls, but I guess the EQ gives you that.  It isn't what I would recommend for my system - but I guess it could work for you and if it does.

    Eric1024
    I actually only got this particular unit because it had a 7 band EQ that you can actually adjust(as opposed to a 3 band eq with 5 presets that you can't tweak.) I guess I would miss the cool colors lol...

    Actually - most of the 3-band models have 5 presets AND one mode that you CAN tweak, but ....  The cool colors (and the ability to exactly match the dash) would be a selling point on the unit for me - others wouldn't care.

    Eric1024
    I think I'll give it a few more days to see if anyone can come up with a solution

    You could try running the speakers directly off the HU or running RCA's to the amp - not sure it will make a major difference - just throwing options out there.

    Have you tried copying your MP3's to a flash drive and playing them off the HU that way?  (It wouldn't surprise me a bit if the poor D/A converters in the MP3 player and the poor quality (in general) AUX input on the HU weren't the main source of your problems).

    Also - you might well find out that the new amp fixes the issue and then you could go back to using the HU - although if you indeed are only using it for the EQ and colors - you might be better off with the previous setup.

    Eric1024
    so it's reassuring to see that the community isn't totally ignoring it.

    We don't ignore much of anything - although sometimes when I have no clue, I'll try to let others comment first.

    Hope This Helps!!!

    Anyone else have suggestions?

     

     

    2002 Ford Focus JVC KD-A815 Sony CDX-GT410u Sony XT-100HD HD Tuner Stock speakers, no amp, no subs

All Replies
  • Update:

    I was able to reduce the volume at which distortion occurs by turning the sub-bass all the way down on the device's built-in EQ, however, this still doesn't really solve my problem. Would be really nice if the thing had a built in crossover - there's a low pass filter for the sub pre-out, and no door speakers will ever reproduce anything below 40Hz, especially not hooked up to something that only does 20W RMS...

  • I admit I skimmed through most of your post, but ....  I'm really not seeing too much what the problem is ....

    Most - if not all - aftermarket HU's will distort on the speaker level outputs at about 80% volume.  You should be able to set the volume at 80% and set the gain properly on the LOC and the amp and be fine.

    Ideally, you should be running RCA's without a LOC with that HU - is there a reason you aren't (other than you have it wired to a LOC previously and didn't want to run a long RCA all the way through the car) - Most HU's DO NOT distort on the RCA outputs.

    If you definitely don't want to run RCA's and don't want to have the HU distort when you turn it up - there is this from the HOR tab:

    Amplifier Gain Control: When you are using the KD-HDR60 with factory speakers (or those rated to less than 50 watts peak), the Amplifier Gain Control can limit the amount of power being sent to those speakers. When the Amp Gain Control is set to Low, the volume control ranges from 0 (minimum) to 30 (maximum). When using speakers rated higher than 50 watts peak, you can set the Amp Gain Control to High, and the volume control will range from 0 to 50. When all speakers in the system are powered by an external amplifier, the internal amplifier can be turned off.

    Seems like you could set that to Low and you would have to set the amp gain higher, but that would eliminate your problem.

    HPF settings in the HU would be nice (especially without an external amp), but doesn't the external amp have HPF settings?

    Your post was confusing b/c it sounded like you were running the iPod initially to an amp in the trunk - then to an EQ, and now directly to the speakers - not sure what amp was or is in the system.

    Also - the EQ was common ground on the left and right sides - the JVC is NOT.  You can't wire the negative leads together on the JVC - you can seriously damage the HU if you do!!!

    The above could be your problem - it is more likely than the wiring issues you mentioned, but I really think it is just that the HU distorts by design at about 40.

    Sorry if the reply got confused.

    Hope This Helps!!!

    Anyone else have suggestions?

     

    2002 Ford Focus JVC KD-A815 Sony CDX-GT410u Sony XT-100HD HD Tuner Stock speakers, no amp, no subs

  • Sorry for the lack of clarity - I'm running the signal to the trunk at speaker level due to the interference I was picking up at line level - same reason I decided to put in the EQ initially - also the principle used in higher end cars with premium sound systems(bmws, for example, send signal to the amplifier at like 8v.) I admittedly have not tried running a line level signal from the HU itself into the outboard amp, but since the HU only has a sub out, and one set of LR outs, I would not be able to use the fader if I use the line outs.

    As for the filter, my outboard amp does have a filter, but the signal will already be distorted by the time it gets to the amplifier's filter because the head unit's last amplification stage is still amplifying a bunch of 5-60Hz stuff(which takes up far more headroom than higher frequencies) and if I could filter that off before the amplification stage, that leaves more headroom for other frequencies(which my speakers /can/ reproduce.)

     

    I guess at this point, I'm trying to find some way(excuse?) to keep this head unit, but in retrospect, I may be better off investing that money into a better amp or mp3 player.



    [edited by: Eric1024 at 2:07 PM (GMT -5) on Tue, Mar 30 2010]
  • I still didn't get the answer I was looking for!!! Devil

    What amp are you using - BMW factory amp, or an aftermarket amp?

    Eric1024
    As for the filter, my outboard amp does have a filter, but the signal will already be distorted by the time it gets to the amplifier's filter because the head unit's last amplification stage is still amplifying a bunch of 5-60Hz stuff(which takes up far more headroom than higher frequencies) and if I could filter that off before the amplification stage, that leaves more headroom for other frequencies(which my speakers /can/ reproduce.)

    Again - don't quite follow the logic here - the head unit distorts in the 5-60Hz range, but if you filter that off, it doesn't get to your speakers.  The only issue would be if the HU output is low enough that you have to max out the gain on the amp or turn the HU all the way up and then either the amp or the HU is introducing distortion above the HPF setting.

    Eric1024
    I guess at this point, I'm trying to find some way(excuse?) to keep this head unit, but in retrospect, I may be better off investing that money into a better amp or mp3 player.

    I really don't see an MP3 player doing you much good - a better amp would, but it's not a really expensive HU, and I don't see that you would save much on a different HU that you could then put into a different amp.

    Hope This Helps!!!

    2002 Ford Focus JVC KD-A815 Sony CDX-GT410u Sony XT-100HD HD Tuner Stock speakers, no amp, no subs

  • Sorry for the confusion - The current setup is head unit speaker out -> scosche line level converter -> amplifier -> speakers. The primary reason for running through the speaker outs instead of the line outs is so I can still use the built-in fade control, and also because high level signals are less prone to interference. This is also why I want to milk every last watt of power out of the head unit. I was merely citing BMWs as an example, as they use a high level signal to get from the head unit to the amp as opposed to a line level one. Both will pick up interference, but with a high level signal, the interference will account for less of the total volume (signal to noise ratio.) Admittedly, I am using a pretty low end amplifier - something I picked up at a flea market-and I couldn't afford a BMW lol.

    The head unit isn't exactly distorting in the 5-60hz range, but these frequencies take up "space"(aka headroom) in the total signal that the amplifier will process - by removing them, it would leave more space for higher frequencies, and thus, other frequencies themselves can be amplified more without distorting. This is why the distortion went away when I turned the sub-bass all the way down - the same would have probably happened had I adjusted another EQ band - the idea is, you're turning down the volume at certain frequencies, and thus, you can turn the total volume up, so other frequencies can be louder, while the combined energy of the frequencies(RMS) stays the same.
    It's the same reasoning behind why you cut these frequencies on your amp - if you send your speakers a 60hz wave, they may be able to reproduce it, but since they will have to move so far(excursion) to reproduce just that 60hz wave, they wont have any more room to move when they get a 1000Hz wave (in addition to the 60Hz wave) and instead, you'll hear distortion. Don't let this confuse you - my speakers aren't the source of the distortion - I'm merely using them as an example since I can't think of anything else "concrete" to use.

    As far as trading in the HU for something else - I was actually thinking about omitting a HU from my setup entirely, like what I had before. It would be a (new, better)mp3 player feeding the (same old)EQ, feeding the (new, better)amp. I wouldn't be trading in for another head unit, as I really only need the HU for mp3 playback - don't even use the radio or CD player. I actually only got this particular unit because it had a 7 band EQ that you can actually adjust(as opposed to a 3 band eq with 5 presets that you can't tweak.) I guess I would miss the cool colors lol...

    I think I'll give it a few more days to see if anyone can come up with a solution (can't actually make this swap til Friday when I'm off work) and go back to my old setup til the new amp arrives. In retrospect, I have no idea why I didn't decide to do that the first time around. -facepalm-


    I figure this is probably a one of a kind issue(given my wiring setup, and the fact that most people probably wouldn't be so anal about this distortion,) so it's reassuring to see that the community isn't totally ignoring it. Thanks for your help and attention :)



    [edited by: Eric1024 at 10:16 PM (GMT -5) on Tue, Mar 30 2010]
  • The flea market amp does not have HPF settings?  Although without a subwoofer, that's not a great idea - but it would help - more below.

    Are you sure the flea market amp is more powerful than the JVC's internal amp?

    Eric1024
    The head unit isn't exactly distorting in the 5-60hz range, but these frequencies take up "space"(aka headroom) in the total signal that the amplifier will process - by removing them, it would leave more space for higher frequencies, and thus, other frequencies themselves can be amplified more without distorting. This is why the distortion went away when I turned the sub-bass all the way down - the same would have probably happened had I adjusted another EQ band - the idea is, you're turning down the volume at certain frequencies, and thus, you can turn the total volume up, so other frequencies can be louder, while the combined energy of the frequencies(RMS) stays the same.

    I agree and I don't agree.Devil  I will agree that bass takes more power to reproduce and filtering out the bass will allow you to play the speakers louder without distortion.  Where I disagree is that having HPF's in the HU would automatically allow the deck to channel it's internal power to other frequencies.  I don't think HU designers factor that into account.  Bottom line - I think whether you have HPF's in the HU, F-mod HPF's in the RCA's, HPF's in the amp, or bass blockers on the speaker leads, the end result is the same (neglecting differences in db/octave slope, etc.)

    Eric1024
    I wouldn't be trading in for another head unit, as I really only need the HU for mp3 playback - don't even use the radio or CD player.

    There's also fader and tone controls, but I guess the EQ gives you that.  It isn't what I would recommend for my system - but I guess it could work for you and if it does.

    Eric1024
    I actually only got this particular unit because it had a 7 band EQ that you can actually adjust(as opposed to a 3 band eq with 5 presets that you can't tweak.) I guess I would miss the cool colors lol...

    Actually - most of the 3-band models have 5 presets AND one mode that you CAN tweak, but ....  The cool colors (and the ability to exactly match the dash) would be a selling point on the unit for me - others wouldn't care.

    Eric1024
    I think I'll give it a few more days to see if anyone can come up with a solution

    You could try running the speakers directly off the HU or running RCA's to the amp - not sure it will make a major difference - just throwing options out there.

    Have you tried copying your MP3's to a flash drive and playing them off the HU that way?  (It wouldn't surprise me a bit if the poor D/A converters in the MP3 player and the poor quality (in general) AUX input on the HU weren't the main source of your problems).

    Also - you might well find out that the new amp fixes the issue and then you could go back to using the HU - although if you indeed are only using it for the EQ and colors - you might be better off with the previous setup.

    Eric1024
    so it's reassuring to see that the community isn't totally ignoring it.

    We don't ignore much of anything - although sometimes when I have no clue, I'll try to let others comment first.

    Hope This Helps!!!

    Anyone else have suggestions?

     

     

    2002 Ford Focus JVC KD-A815 Sony CDX-GT410u Sony XT-100HD HD Tuner Stock speakers, no amp, no subs

  • You do realize that line out still is effected by the fader, right? Also, the locs you are running are most likely putting way more interference than a good set of rcas going from the headunit back to the amplifier.

     

    Just run rcas back to the amplifier, nobody with a nice audio system (bar people who REALLY like the factory headunit) use line output converters, because using them, you are amplifying the signal with the headunit, then reducing the signal strength with the locs. All that does is reduce quality (like converting a movie from 1080p to 720p, then back to 1080p again, nothing is perfect, so there is going to be a bit of loss there), which is why any headunit worth buying has rcas on the back, so that you can bypass the internal amplifier and not deal with the excess noise that puts into the signal.

     

    Like TigerHeli said, you should just burn some mp3 cds, in 320kbps, and use them instead of your media player, this should give you better quality than you setup before, because you were using your media player's DAC, which on most media players, is not nearly as good of quality as one like your headunit has. Also, the only thing I can disagree to TigerHeli about is that the headunit's rcas do in fact distort, but not nearly as much as the speaker outs coming from the headunit.

     

    I hope you don't take any of this negatively, as none is intended to be. I just really hate to see people get rid of something that could have worked, and have wasted money. Good luck in getting getting your stereo sounding better!

    1985 Toyota P/U Orion Cobalt 10" on MTX 801D, Soundstream 5x7 in custom boxes, no name 4" in dash

  • Mark S
    Also, the only thing I can disagree to TigerHeli about is that the headunit's rcas do in fact distort, but not nearly as much as the speaker outs coming from the headunit.

    You might well be correct on that - I think I got it from an old post by Andy Wehmeyer - but he might well have also meant that they don't appreciably distort and I simplified it.

    2002 Ford Focus JVC KD-A815 Sony CDX-GT410u Sony XT-100HD HD Tuner Stock speakers, no amp, no subs