TL;DR up front: my suburban has intermittently fuzzy audio. Sometimes it is great, sometimes it isn't, and I don't know why.
So far the GM forums have been pretty useless on this one. I've got a 2004 Suburban 2500 that has the mid-level Bose system in it. It also has the rear seat DVD player and such. It is not the fancy "lux" system used on the Denali and Escalade of the same era. The entire system is stock, which means it has the factory head unit running to an amp in the console powering the speakers. There is also a subwoofer built into the center console, and the usual little headphone jack interface in the back that most GM stuff from this era has. Like most of these, the CD player/changer in the head unit is broken.
The only modification is an iSimple ISGM655 adapter setup that replaces the XM module and allows you to use bluetooth and have an aux input with the stock head unit. It works on some kind of GM CAN bus; I forget what the name of the bus is but it also communicates with the rest of the truck for door chimes, speed sensitive volume, the DVD player, and the rear seat audio controls. I'm only going into this in detail because this adapter likes to reset itself occasionally, and is also my primary audio input.
Problem with it is that sometimes the audio quality is great, but most of the time it is fuzzy. It almost sounds like the speakers are blown, or like the amp is clipping. The fuzziness is in all the speakers and the subwoofer regardless of the source. Even the door dings are fuzzy when it is bad.
Can an amplifier fail partially and make things intermittently fuzzy like this? Is there something else I'm missing that I should check?
Yes, amp can fail like this.
My wifes DD, an 06 R class, has an antenna amp that is going bad from what research I have done. Radio stations will come in fine and then be very faint or staticky.
Dad had the same issue on his 08 Silverado. He took it in under warranty and they found a TSB about speaker failure. I told him they were pulling his leg because the probability of all 7 speakers blowing at once was nearly impossible. Evidently something about the BCM caused problems with the speakers. The dealer replaced all the speakers and the problem is gone. I don't know why or how, but maybe that is something you could explore.
GM electronics are becoming a nightmare these days. Dad's 04 Silverado would start playing Disc 1 every time he turned on the key for a while, then it seems to have resolved itself.
Interesting, thanks for the feedback. I will look for a used amp and see if that fixes it then. I actually have a nice 4 channel JL amp in a box somewhere that might be a good upgrade now that I'm thinking about it. But who knows what new problems that might cause.
@Curtis73 that is a really strange one...I guess I should pull some of the speaker covers/door cards and at least get a visual, or see if I can test them on some other audio source. They are almost 20 years old by now after all.
GM electronics are definitely one of the reasons I was hesitant to upgrade from my GMT400 truck, but it seems like everything has potential electrical issues these days so if I want the benefits of a newer truck, it is a risk I had to take. At least most of the GMT800 stuff is still pretty simple and well documented by now (I don't think any of them still have working CD changers...). The newest stuff would be a real challenge for me.
In reply to gearheadE30 :
If it's got a Bose system in it, your JL amp will likely not work without additional work on the system and potentially replacing the speakers as well, as Bose often uses speakers with weird low impedance.
BoxheadTim said:
In reply to gearheadE30 :
If it's got a Bose system in it, your JL amp will likely not work without additional work on the system and potentially replacing the speakers as well, as Bose often uses speakers with weird low impedance.
This. Bose does some really strange proprietary stuff with their electronics. You'll find that nothing really interchanges with anything else.
Well that's a bummer. Looks like the system is set up with differential signals and the head unit outputs are higher voltage than industry standard. So while I don't know what all that means exactly, it does tell me enough that I should just replace the stock amp since I'm not ready to go down the road of replacing everything.
In reply to gearheadE30 :
if that is the case a lot of amps will take a differential signal with high level inputs.
Curtis73 (Forum Supporter) said:
BoxheadTim said:
In reply to gearheadE30 :
If it's got a Bose system in it, your JL amp will likely not work without additional work on the system and potentially replacing the speakers as well, as Bose often uses speakers with weird low impedance.
This. Bose does some really strange proprietary stuff with their electronics. You'll find that nothing really interchanges with anything else.
Yeah, I was about to share this after the experience with the BOSE system in my NC.
The amp was integrated into the head unit and the speakers were all a weird OHM spec that didn't interchange with any readily available stuff.
I kind of fell down the rabbit hole on this one... apparently I lack the self control to leave well enough alone.
The Bose "lux" system on Escalades and Denalis uses unique 500mV preamp outputs from the head unit to a special amp. The amp has integrated signal processing, and all of the volume control, mute, EQ, etc. functions take place in the amp. They are controlled by the head unit via the GM class 2 data bus.
The Bose standard system that I have in the Suburban is more conventional. Head unit feeds a signal to a more standard amp, which only does amplification duties. Apparently it is about 100W for the speakers and 50W for the sub. The goofy part, aside from the differential signals, is that the output from the head unit to the amp isn't line level, but it isn't speaker level either. Apparently it is something like 6.5V, but from what I can tell, this doesn't seem to inherently be a problem. I'm also not 100% sure it's true and will have to see if I can measure it somehow.
All GMT800 head units, at least for the later models, are the same aside from if they have the tape deck or CD changer. They can all be reprogrammed with software compatible with the different systems.
The speakers and subwoofer are the same between Bose standard and Bose "lux", but the "lux" system is 6 channel plus sub with the D pillar speakers on their own channel. The standard Bose is 4 channel plus sub. There is no separate amp for the sub, either way - the sub amplification is integrated. Surprisingly, the Bose speakers are a relatively normal 2 ohm impedance.
Both amp versions have integrated crossovers and high pass filters to keep the bass out of the door speakers. Both systems use differential signals.
It appears that the standard Bose system is actually pretty normal on these trucks. The amp I have (a JL JD400/4) seems like it should be compatible with the head unit's signals and my current speakers, though I'll need an additional small single channel amp for the sub. Is it worth the trouble vs just replacing the stock amp? I'm considering it, mainly because I spend a ton of time in the truck and I really enjoy a good sound system.
z31maniac said:
Curtis73 (Forum Supporter) said:
BoxheadTim said:
In reply to gearheadE30 :
If it's got a Bose system in it, your JL amp will likely not work without additional work on the system and potentially replacing the speakers as well, as Bose often uses speakers with weird low impedance.
This. Bose does some really strange proprietary stuff with their electronics. You'll find that nothing really interchanges with anything else.
Yeah, I was about to share this after the experience with the BOSE system in my NC.
The amp was integrated into the head unit and the speakers were all a weird OHM spec that didn't interchange with any readily available stuff.
Yeah, the term from miata.net was "Bosectomy". There was one company that made replacement speakers for the NB Miatas otherwise the whole system had to be ripped out.
