One day I went to use my truck and either my amplifier or subwoofer wasn’t working anymore. I have this one (http://shop.store.yahoo.com/discave/ntdhd2chanca2.html) I realize it’s not the greatest brand, and I have had it for more than three years (I only paid like 120 bucks for it). I just don’t want to buy a new one if I don’t have to. Basically, I am a computer engineering student so I have access to a lab with DC power supplies and multimeters. If I was to measure the output voltage/current from the amplifier what should I expect? Would simply using a 12V supply from a DC power supply mimic a truck battery anyway? Is there an easier way?
BTW, I have changed the amp’s fuse. Thanks in advance.
Assuming you know the source - presumably your car radio or CD player - is in good working order, the easiest thing to do is to test the speaker(s) the amp is driving, rather than the amp itself. Use an ohmmeter and measure across the terminals. An 8-ohm impedance speaker will typically read a DC resistance of between 6 and 8 ohms. You should test for continuity of the wiring at the same time, as well. If everything seems ok, it’s a good bet the amp is bad. If for some reason, this is impossible or impractical, let me know, and I’ll help you test the amp itself.
Oh, and how is the subwoofer connected to the amp? The linked specifications page is a bit sparse on details and doesn’t mention a subwoofer output. If you can provide a few basic details about your system, it might prove helpful.
How is it malfunctioning? You ask whether it’s the amp or subwoofer - does this mean you get sound but no bass? If that’s the case, it would more likely be the subwoofer (or the speaker wiring) than the amp.
As for hooking the unit up to a 12 V power supply, this will work as long as the supply has enough power. A power supply in a computer lab might not be able to supply the current needed for a stereo system. The amp in question is rated at 300 watts per channel, and at 80 watts per channel into 4 ohms. You’re not going to run it at full power, but lets say you ran it at 20 watts per channel. That’s 40 watts total, so the power supply would have to deliver at least this much. That’s 3 1/3 amps at 12 volts.
The Yahoo description of this amp says it has a variable high-pass filter. If you’re not getting any bass, is it possible that this filter is set wrong?
I really don’t know that much about how my system is connected or anything. I just know that I obviously have the power and ground connnected and then my subwoofer (a JL Audio 12 inch) was connected at the R+ and L+ connection terminals from my amp. I can’t find any kind of specifications sheet online from the company itself. THis is the only thing I can find (http://dhdusa.com/a_ntx_211x.html) I have the ntx-2112.
It would be a lot easier to test my amplifier than it would the speaker unless I could do this. This may be stupid, but could I take my subwoofer and connect it to my computer (by using an old set of headphones cut up so it would connect)? If so, this would probably be easiest thing to do.
As far as how it stopped working, I still get audio from my CD player and it plays in all of my speakers except the subwoofer. When my amplifier is connected the fans on it are still blowing.
As for the filter, I am pretty sure that’s not it as my system was working one day and the next when I went to use it it did not. I am pretty sure that no one was able to get in there and change anything.
Now I’m confused. You say you have the subwoofer connected to the R+ and L+ terminals of the amp, yes? If this is correct, it means you have the subwoofer wired from the red terminal on one of the right channels to the the red terminal on one of the left channels. Is this the case? This is very bad. You can easily overload your amp, and also supply a large overload to the speaker thus connected, plus it won’t work the way you intended anyway. You probably did blow the subwoofer, if this is how it’s connected. Since you say the other speakers are ok - and I’m assuming they are also connected to this same amp - then the amp itself is almost certainly ok. If you want to run a subwoofer, you either need an amp with a dedicated subwoofer output, or a separate amp for the subwoofer. Failing that, you at least need a crossover network connected to the amp output which provides an output for a sub - this is not ideal, but it’s far better than the way you apparently have it connected now.
I agree with Q.E.D. - it’s wrong to hook the subwoofer up to L+ and R+. I’m amazed it ever worked like this. Are you sure there’s no crossover unit in the system? If not, you need one.
A crossover in a system with a subwoofer performs two functions. First, it routes the low-frequency signal to the subwoofer (the part of the frequency spectrum the subwoofer is designed to reproduce). Second, it combines the signal sent to the subwoofer from stereo to mono (since there’s only a single subwoofer - there isn’t much stereo imaging in such low frequencies, so there’s no point in having two subwoofer speakers).
DHD shows three different crossover units on their web site. My guess is that the NTX-6208 2-way crossover would be appropriate for you, since you’re just trying to split the signal between the subwoofer and a pair of conventional speakers (that is, you don’t have separate mid-range and tweeters, right?).
I would try to figure out whether the subwoofer still works at all. You could do this by disconnecting the other speakers and hooking the subwoofer up to one channel (not L+ and R+). Play something that has a lot of bass and see what comes out of the speaker.
You can use a crossover, like the one that Jeff Lichtman mentioned above. it will have the following inputs:
Right +
Right -
Left +
Left -
and the following outputs:
Right +
Right -
Left +
Left -
Subwoofer +
Subwoofer -
You’ll connect the inputs exactly the same as you would normal speakers, and connect the speakers and subwoofer to the matching outputs on the crossover. Until you get this, DO NOT connect the subwoofer, or you risk damaging the amp. The subwoofer itself is probably already toast, but you can test it as outlined above to be sure. An even better solution would be to purchase a standalone subwoofer amp, and split the input from the car stereo to feed both amps. This gives you better control over the sound quality, plus the full range of the subwoofer capability. Amps not designed to drive a subwoofer may not have the necessary low-end frequency response.
Don’t count on this completely. This is a quick and dirty test for voicecoil continuity, but it does not test the integrity of the cone or for shorts between voicecoil turns, which which causes distortion - often severe. Once you get things set up per my post above, definitely give it a good test and listen for buzzing, rattling or other similar sounds that indicate a problem with the sub.