Help with crossover

[shinester184]

Hi,

I recently bought a Boss BX15 subwoofer crossover, however for now I intend to use it OUT of a car. I don't know a great deal about car audio and have run into a problem - some help would be great!

I have bought the crossover to use temporarily as a lowpass filter with DJ mixer going into a PA amp via the crossover as it is a much cheaper option than buying a real DJ crossover for over £100. It was guess work though - I wasn't a 100% confident it would work!

Anyway here is my problem;

To power my crossover, I have got a normal mains to 12V DC plug and chopped the end off. I have inserted the two separate wires into the 12V+ and REM terminals. The power LED lights up bright green, so it seems on!

I have inputted into the crossover via RCA from the DJ mixer and have the output RCA going into the amplifier.

Problem is, no signal is being received by the amplifier! nothing seems to be getting through the crossover.

There may be a really obvious flaw in this layout, and it would be great if someone could highlight it. If it's not working because it's faulty, then the headsup would also be great.

Many thanks!

EDIT: for a dedicated sub amp usind 2nd output of mixer

 

[joeyjojo]

Not quite sure what you're doing. A crossover like that is a low pass filter. This one looks decent, as you can give it either a line level (not amplified) or high level (amplified) signal. It then cuts off everything above eg. 120Hz or whatever you set it to, and sends what's left to the sub.

By amplifier do you mean a dedicated sub amplifier?

 

[shinester184]

By amplifier do you mean a dedicated sub amplifier?

Yes. I have a dedicated amp for 3 subs, but they go quite high into the mid ranges so got this.

Have got it running on a 12V supply from the wall but getting no output when it's set up (signal LED not lighting up on amp)

Shows here the mixer going into input and the output disapperaing off the amp under the desk.

I'm just confused as to why there is no output from the crossover??

 

[Phemo]

The power should surely be going to the 12v and ground connections. The remote terminal is a switched 12v signal that tells the box to turn on when it receives that - ie. when you turn the car's ignition on.

I'm not entirely sure how you'd set this up in this scenario since you're not using it in a car, but I'm quite certain you should be using the ground terminal too.

 

[shinester184]

The power should surely be going to the 12v and ground connections. The remote terminal is a switched 12v signal that tells the box to turn on when it receives that - ie. when you turn the car's ignition on.

I'm not entirely sure how you'd set this up in this scenario since you're not using it in a car, but I'm quite certain you should be using the ground terminal too.

I connected to the ground terminal ans started to smell burning :S so have taken it out. How else might I use thr ground terminal? In the small connections page it says it just attaches to the car's chassis?

 

[AtaRo]

As stated by phemo the negative of the power supply goes to the ground and the positve goes to 12v+ and you can short the REM connection to the 12v+ to turn the crossover on.

 

[AtaRo]

I connected to the ground terminal ans started to smell burning :S so have taken it out. How else might I use thr ground terminal? In the small connections page it says it just attaches to the car's chassis?

Did you check the polarity of the power supply cable before inserting it?

 

[MikeHunt79]

Try setting the level to 12db, PA amps use much higher levels than consumer gear...

 

[banja]

Have you checked that the 2nd output of the DJ mixer is good? Check coming out of the main output to ensure the crossover is receiving a signal. Also, sounds obvious, but also check your RCA phono leads are good.

 

[shinester184]

Got some bad news, connected the negative wire to the ground terminal again, and there was quite a significant bang. Opened it up and a resistor seems to have been obliterated (it was black and R53 if it's any use?)I can see the two wires so I can probably replace it.

The crossover still turns on however when I have the 12V+ and REM terminals connected the crossover still turns on but I don't know if this is any use :/

All my cables/outputs are good, and I've experimented with levels.

Have I fudged it with this resistor going blam?

Cheers guys

 

[AtaRo]

Can you post a top view pics of the inside showing a clear view of parts and a bottom/underside pics clearly showing the pcb traces.
As I have stated in my previous post did you check the polarity of the 12v cable your inserting to the crossover?
Cause it will surely damaged it if powered in reverse polarity and this is probably why you burn the resistor and the resistor is probably just a fusible resistor and can safely be replaced.

 

[shinester184]

Top side, showing missing resistor in red circle (the resitor had black casing)

And under side:

Thanks!!

 

[AtaRo]

As I suspected your powering the crossover in reverse polarity thats why you burn the resistor, you also damaged the capacitor in the pic and possible the other beside it.
I suggest you get yourself a multimeter and identify the polarity of the 12v cable before inserting it to the ground and the 12v+.You also need to removed/replace that bulging capacitor.
I did not noticed at first but It looks like you also burn another resistor beside Q1.Looks like a 10Ω or 100Ω.



this is how you power the crossover.
12v+ REM GND
+12v +12v -12v

 

[shinester184]

Thanks very much AtaRo, I have indeed damaged the two capacitors next to each other, and also the smaller capacitor on the far left is bulging too. I will replace those three.

Also, for the blown out resistor (R53 circled in picture) what should I replace this with?

Thanks

EDIT: also just wondering, because Ive run this in reverse polarity, is there a chance I have permanantly damaged the crossover even after I have replaced the resistor and capacitors?

 

[MikeHunt79]

May I suggest a cheap mains powered crossover? Behringer make some pretty cheap ones which work well, but if you've got a little extra cash the DCX2496 is damn nice as allows lots of tweaking.

It also has XLR outs which is ideal for PA gear...

 

[AtaRo]

Also, for the blown out resistor (R53 circled in picture) what should I replace this with?



also just wondering, because Ive run this in reverse polarity, is there a chance I have permanantly damaged the crossover even after I have replaced the resistor and capacitors?

I really just cant guess the value for r53 unless I see the schematic for it or how it is connected to the circuit but if you got an ohmmeter/multimeter you can try measuring it cause although the resistor may look burn you may still be able to measure it sometimes.

There is a good chance that the damage to the crossover is only limited to the caps/resistor cause of the limiter resistor and when you power a capacitor in reverse it will present itself as a low resistance and thus absorb as much current until it blows and seeing that there are several of them in the circuit as bypass there is a good chance the amplitude that reach the active parts is not high enough to damage it.Fingers cross though.

 

[MikeHunt79]

I really just cant guess the value for r53 unless I see the schematic for it or how it is connected to the circuit but if you got an ohmmeter/multimeter you can try measuring it cause although the resistor may look burn you may still be able to measure it sometimes.

There is a good chance that the damage to the crossover is only limited to the caps/resistor cause of the limiter resistor and when you power a capacitor in reverse it will present itself as a low resistance and thus absorb as much current until it blows and seeing that there are several of them in the circuit as bypass there is a good chance the amplitude that reach the active parts is not high enough to damage it.Fingers cross though.

It may be worth checking the traces around the burnt resistor also... I've found that the traces can also get hot when too much current goes thru them, and they are prone to lifting. Still this PCB looks to be single sided so can easily be bodged if needed...

As for a schematic, I remember a website that had loads of them for various bits of audio gear, it's surprising what google will turn up these days as it searches inside most PDFs...

 

[shinester184]

Thanks AtaRo, your help is brilliant. I will try to get it fixed (replace caps and resistor) and power it the way you said, then I'll report back. I'm seeing a friend next week who is an electrical engineer so he will have the tools to attempt to work out R53. Cheers!

 

[shinester184]

Ignore this.