Need advice from the PRO's...Mono amp gets hotter than hell...any suggestions?

**bambam** · 08-01-2007, 06:35 AM

Ok, here is my simple setup.

A Panasonic CQ 99 <something> 70W HU that pushes a max 5V to the amp.

A Pioneer GM-7300M Mono Power Amplifier with 800 Watts Max. Power (2 Ohm stable)
http://www.pioneerelectronics.com/pn...846766,00.html

and two Pioneer TS-SW2541D, 10" shallow, 4 ohm subs
http://www.pioneerelectronics.com/pn...564759,00.html

I have the subs wired in parallel (2 wires from the amp +, 1 to each sub and 2 wires from the amp -, 1 to each sub) and the amp power and neg cable the same size as detailed in the specs. Pretty simple setup.

The amp has a gain that goes from .4V (clockwise) to 6.5V (counter clockwise). The manual says to turn the gain clockwise with the volume turned up (whatever that means) until the sounds distorts and then turn counterclockwise until it clears up. When I turn the gain clockwise, I never hear the sound distort but I do hear the sub THUMP volume increase dramatically (which sounds awesome by the way). When I turn it counter clockwise, I hear the THUMP volume decrease dramatically until it effectively fades away to nothing if I go all the way counter clockwise. The tech guy tells me that the gain control must be turned to match the HU voltage to the amp voltage setting so I'm trying to guess the correct range (I have to be very close).

The problem is no matter where I set the gain, if I crank the HU volume, the subs start cutting out and the amp gets so hot that I can't hold my hand on it. I've even installed dual fans around it but it doesn't cool it off.

Any suggestions on what to try? I have called tech support 4 times (very nice people that really do try to help) and each time, a different tech answered and they have all said the amp will handle the subs in parallel with no problem.

Thanks in advance to all who respond...appreciate it.

**durwood** · 08-01-2007, 07:32 AM

Are you sure you have a solid ground? I.E. Ground connected to bare metal (shiny no paint).

Otherwise you could have a bad sub-the impedance is too low or is slighty blown. Has it always worked as you describe or has it just recently started acting up?

**XC-C30** · 08-01-2007, 07:34 AM

hmmm.... Your subs are 250watts each..... your amps is 360watts at 2Ohms.... So technically your subs are underpowered. Are you sure it doesn't distort? It's harder to hear with a sub than with kicks or tweeters.... Underpowering doesn't have to be a bad thing, but I think you might be pushing the amp a little hard maybe...

**bambam** · 08-01-2007, 07:45 AM

Originally Posted by durwood

Are you sure you have a solid ground? I.E. Ground connected to bare metal (shiny no paint).

Otherwise you could have a bad sub-the impedance is too low or is slighty blown. Has it always worked as you describe or has it just recently started acting up?

It has always worked like that. The only time I really crank the volume is when I have the windows down.

Ironically, the tech guy I talked to last night mentioned ground also. Thanks for the response, I'm going to take everything out and make sure the ground area is to the bare metal.

**bambam** · 08-01-2007, 07:47 AM

Originally Posted by XC-C30

hmmm.... Your subs are 250watts each..... your amps is 360watts at 2Ohms.... So technically your subs are underpowered. Are you sure it doesn't distort? It's harder to hear with a sub than with kicks or tweeters.... Underpowering doesn't have to be a bad thing, but I think you might be pushing the amp a little hard maybe...

I've had the volume up high enough where I thought I'd tick off our neighbor and have never heard any distortion.

I'm going to look at the "ground" suggestion and try the "gain till distortion" tweak again.

Thanks for taking the time to respond

**monkeyracer** · 08-01-2007, 05:23 PM

Here's a few other things to try if the ground is good:

Take one wire from the amp + to one speaker's +, then from that same speaker's + to the other speaker's +, then from the amp - to the first speaker's -, and then from the same speaker's - to the other speaker's -.
This is the proper way to wire it in parallel.

You do have it wired in parallel, but in a strange way imo, it may not seem like much, but it may help.

Also, what gauge wire are you using for everything? You should be using at least 8 AWG for the power and ground, and at least 14 AWG for the speaker wires. Also make sure the Ground wire is shorter than the power wire, and that the fuse is within 18 inches from the battery.

@xc-c30, it's better to under power the speakers than to overpower them.

This set-up should be fine, with minimal distortion. Overpowering the subs can definitely make them clip and possibly over extend, meaning the voice coil is not lined up with the magnet.

If the sub is failing it will cause a short in the sub itself, and have different electrical properties, but still play. Easy way to check if it's blown: lightly press down on the center of the sub, if it sounds like it's scratching, it's most likely blown.

The manual has the gain till distortion procedure, but if it's turned too high up, the amp has to work harder to compensate for the mismatched voltage, and would heat up. So try to get it as close as possible to the optimum.

Lastly, the amp's mounting position can be affecting it too. Heat of course rises, so if the amp is vertical, the heat from the lower part of the amp will rise to the top part and not allow the heat sink to do the best job of cooling it. When it's horizontal, the heat sink has the best chance for cooling the amp. Also, if there's not much space above the amp, this air will heat up quickly, and not allow the heat sink much cold air to dissipate the heat into.

**XC-C30** · 08-01-2007, 06:00 PM

Originally Posted by monkeyracer

@xc-c30, it's better to under power the speakers than to overpower them.

Actually.... It doesn't make any difference as long as things are set up correctly. Underpower may make the amp clip, overpower may blow the speakers.

The other way around, overpower will push them a little more, generally giving more detail or keeping betyter vcontrol over the unit which will make it sound more laid-back. Where underpower will fail to get the sound out of the speakers, resulting in a cut-up frontstage.

the install of a friend of mine:

focal polyglass set, fully active: tweeters, 15watt RMS.... ssounded agressive as you could get....45watt rms on them, smoother, but with a little rimm.....105watt rms.... HELL YEAH.... 220watt rms? they started to smell a little, so she went back to 105. Had been playing in her car for 3 years, than she sold the set to aother friend of mijne who is using the exact same set still for more than a year now. If you set up your install correctly overpower, nore underpower will do any harm.

edit: and if you are afrais of overpowering, you can always turn your gains down. But you can't push any more out of an amp than it ca deliver. So a bigger output amp will never hurt anyone.

Pt all boils down to having a clean signal. As long as yoo can accoplish that, underpower, nore overpower will harm your speakers, it'll only change the sound