Whenever I turn my stereo up past 45 (out of 60) the sound cuts out
sparactically. I'm totally at a loss & have no clue what to try next.
My setup is as follows in a 2001 GMC Sierra standard cab;

Pioneer DEH-P8400 Headunit (22w rms/50w peak X4 powering the speakers)
Pioneer 4x6 2-way speakers in the rear (40w rms/80w peak)
Pioneer 6 1/2 3-way speakers in the doors (80w rms/160w peak)
Pioneer GM-X942 amp, bridged at 2-ohm
Audiobahn AW1000Q 10" sub (dual 4-ohm coils in parallel)
Lightning Audio 1 Farad cap
Lighthing Audio 4ga Power/Ground (Power is about 13ft to the cap, then
1 1/2ft to amp, Ground is 1 1/2ft from cap & 1 1/2ft from amp grounded
to the same point)
12ga streetwires speaker wire all soldered from amp to sub

Im confident its a good ground. I drilled into my frame so I ruled
that out. Also, it seems to only cut out when the amp is powered. If
the amp is powered & I shut the sub off from the headunit, it will
still cut out, however, if I unplug either the speaker wire from the
sub/amp, or power cable to the amp, it will not cut out. I've tried
without the cap, & it still cuts out. I've tried another sub at 4-ohm
bridged & running off one single channel, same thing. I'm beginning
to think it might be the amp, but I've used this amp before in my
other car & never had a problem with it for the last 3 years. I don't
have another amp I can swap it out with to see if thats the problem
either.

Another weird thing, is that if I fade the speakers all the way to the
front, it doesn't cut out with the sub/amp running. However, if I
fade it all the way to the back, or even 6 front (out of 15
front/back) it will cut out. When faded to the rear, I can balance it
to the right & it won't cut out, balance it to the left & it will. So
I removed the rear left speaker & it still cut out faded @ 6 front w/
0 balance with no speaker attached to the wire. Another thing, is
that the more faded it is to the front, it seems the more the front
speakers distort, but only when the sub/amp is on, if I turn the amp
off on the headunit the front speakers sound crystal clear. I've also
put a meter on the power cable going to the cap, & then amp, & it is a
constant 14.1 volts, so I think thats ok. Also, when the sound cuts
out, it doesnt cut the bass out. In other words, just my 4 speakers
cut out, not the sub.

I've tried damn near everything short of switching amps/power cable, &
have no clue what to try next, any help would be greatly appreciated.
Thanks.

-Matt

Is the Pioneer GM-X942 1 ohm stable in stereo? By running a bridged 2
ohm load, the amp "sees" a 1 ohm load. Hence the output mosfets pass
enough current to match that of a 1 ohm load in stereo. This does not
sound like the root cause of your problem, but IMHO you should be
carefull with impedence loads. If this amp is not 1 ohm stable, IMHO
it would be safer to wire the dual voice coils in series and push a
bridged 8 ohm load. The amp would "see" this as a 4 ohm load, and
you'll be safer that way.

Sounds like a head unit problem to me. IMHO built in headunit amps are
tricky, they generate a LOT of heat and are stuffed into the dash with
zero circulation. When pushed, the heat build up can adversely affect
other things in the head.

Do you have a portable CD or MP3 player you can hook up to the sub amp?
You need to start with a known good signal source and work your way back
from there. If you send a signal from a known good source to the sub
amp and it does not cut out, then its something else.

????

Garrett



Matt Nye wrote:

Whenever I turn my stereo up past 45 (out of 60) the sound cuts out
sparactically. I'm totally at a loss & have no clue what to try next.
My setup is as follows in a 2001 GMC Sierra standard cab;

Pioneer DEH-P8400 Headunit (22w rms/50w peak X4 powering the speakers)
Pioneer 4x6 2-way speakers in the rear (40w rms/80w peak)
Pioneer 6 1/2 3-way speakers in the doors (80w rms/160w peak)
Pioneer GM-X942 amp, bridged at 2-ohm
Audiobahn AW1000Q 10" sub (dual 4-ohm coils in parallel)
Lightning Audio 1 Farad cap
Lighthing Audio 4ga Power/Ground (Power is about 13ft to the cap, then
1 1/2ft to amp, Ground is 1 1/2ft from cap & 1 1/2ft from amp grounded
to the same point)
12ga streetwires speaker wire all soldered from amp to sub

Im confident its a good ground. I drilled into my frame so I ruled
that out. Also, it seems to only cut out when the amp is powered. If
the amp is powered & I shut the sub off from the headunit, it will
still cut out, however, if I unplug either the speaker wire from the
sub/amp, or power cable to the amp, it will not cut out. I've tried
without the cap, & it still cuts out. I've tried another sub at 4-ohm
bridged & running off one single channel, same thing. I'm beginning
to think it might be the amp, but I've used this amp before in my
other car & never had a problem with it for the last 3 years. I don't
have another amp I can swap it out with to see if thats the problem
either.

Another weird thing, is that if I fade the speakers all the way to the
front, it doesn't cut out with the sub/amp running. However, if I
fade it all the way to the back, or even 6 front (out of 15
front/back) it will cut out. When faded to the rear, I can balance it
to the right & it won't cut out, balance it to the left & it will. So
I removed the rear left speaker & it still cut out faded @ 6 front w/
0 balance with no speaker attached to the wire. Another thing, is
that the more faded it is to the front, it seems the more the front
speakers distort, but only when the sub/amp is on, if I turn the amp
off on the headunit the front speakers sound crystal clear. I've also
put a meter on the power cable going to the cap, & then amp, & it is a
constant 14.1 volts, so I think thats ok. Also, when the sound cuts
out, it doesnt cut the bass out. In other words, just my 4 speakers
cut out, not the sub.

I've tried damn near everything short of switching amps/power cable, &
have no clue what to try next, any help would be greatly appreciated.
Thanks.

-Matt

Yes you can dis-connect the speakers from the built in amp and the amp
will be OK. In theory it will not "try to push". Its not like old tube
amps that toast the oputput transformer without the speaker load. Just
make sure to insluate any exposed speaker leads, dont want them shorting
to chassis ground.

Theres only one way to find out.

disconnect all the speakers from the HU amp.
Feed the head units full range line outputs to the pioneer amp in
stereo, pushing 2 of the 4 speakers full-range. Turn the pioneer line
level gain way down. Turn up the HU volume be carefull and dont blow
the speakers though!! If the signal still cuts out using the line level
outputs, then something is wrong with the HU.

IMHO you should try this before buying a new amp, because the amp may
not be the root cause.

Garrett

Matt Nye wrote:

I hooked a discman up to it & it worked fine. I guess it is my
headunit then. I did get it to cut out without the amp being powered
last night as well. The weird thing, is that it seems to cut out
moreso when the amp is being pushed hard. I can't return the headunit
(had it 2 months) at this point. Is it possible that the headunit is
not getting enough power itself, or is it just junk?

Not that it really matters at this point, but the amp is 1-ohm stable.
In your opinion, if I run a seperate amp for the 4 speakers (since
that would be cheaper than buying a new headunit) would it still cut
out? Does the receiver amp still try to put out a signal even though
there is no speakers attached to it? If so I'm worried it would still
cut out using an amp. Thanks for all your help.

-Matt



Sanitarium wrote in message ...
Is the Pioneer GM-X942 1 ohm stable in stereo? By running a bridged 2
ohm load, the amp "sees" a 1 ohm load. Hence the output mosfets pass
enough current to match that of a 1 ohm load in stereo. This does not
sound like the root cause of your problem, but IMHO you should be
carefull with impedence loads. If this amp is not 1 ohm stable, IMHO
it would be safer to wire the dual voice coils in series and push a
bridged 8 ohm load. The amp would "see" this as a 4 ohm load, and
you'll be safer that way.

Sounds like a head unit problem to me. IMHO built in headunit amps are
tricky, they generate a LOT of heat and are stuffed into the dash with
zero circulation. When pushed, the heat build up can adversely affect
other things in the head.

Do you have a portable CD or MP3 player you can hook up to the sub amp?
You need to start with a known good signal source and work your way back
from there. If you send a signal from a known good source to the sub
amp and it does not cut out, then its something else.

????

Garrett