Kenwood KAC-7201 Problem

Guys,

I just bought a Kenwood KAC-7201 today, and hooked it all up. A little backround first. I am running 2x 10" Orion XTR 4ohm DVC 500w RMS subs. I was running (laugh away) a Profile Baja 600 for the last 7 years (ya little guy won't die) bridged at 4ohms. I have used this same setup like I said for 6 years. Head unit is a Pioneer DEH-740mp 6V preouts (with sub-out). I wired the subs this way: 

I connected the Amp the same way as I has my Profile connected, same 4ga wire, yada yada. The Kenwood Manual ( http://www.kenwoodeurope.com/languages/EN/support/manuals/KAC-7201_7251.pdf) States that you brigde by connecting L+ to R- which I did. My RCA's are quality (monster cable) so that is not a problem. Now there are 2x 30 amp fuses, neither of which are blown, and I even tried new ones. The Kenwood has an overload circuit, but states in the manual that the blue indicator light will go off if it is activated, mine had NOT gone off, and the amp turns on and off just fine with the head unit.

Now the story: After connecting everything I turned it all on, Kenwood's gain was all the way down, and selector switch was on "MONO Lch" per the manual for running it bridged. Amp was fine, worked well, I gradually turned the gain up to about 70-75% (0.5 on the knob on amp) which is wear I typically put the gain on amps, which is enough bass without overloading (Profile amp was there for 6 years.) OK, so after that test was done, I drove down to a vacant parking lot so I could crank it, by crank it I mean my max on the Pioneer is 30, which if you have a Pioneer you know is pretty loud, but not deafining. OK, so I threw in a Bass CD and just kinda checked it out, the bass was amazing, and vert dead on, I loved it. I did notice that the amp got a little toasty to the touch, but nothing that I haven't felt on my Profile, so I didn't think that it was too abnormal. I leave the lot just in time to dodge a cop that I'm sure would have given me crap, and drive down the street listing to Skid Row of all things, Quicksand Jesus which has some nice rolling bass in it. At this point the amp had been going for approx. 25min. Halfway through Quicksand Jesus I head a very slight click, and then no bass whatsoever, BUT the amp was still on, and the blue indicator light was also on. I turned the head unit off for 15min thinking maybe the amp overheated. Turn it back on, nada, no bass. By now the amp is cold to the touch, as it is 35 here (NH) now and I had the windows all open to aid in the cooling. I pulled over to check the connections, and the fuses, nothing out of whack, fuses fine.

So I beg of you 12volt guru's what the hell happened here? I am pretty good at stereo rigging, no pro, but I have been doing it a long time, and have over 50 installs under my belt for other people with no problems like this. Could this be something as simple as a DOA unit from Kenwood? I'm just really bummed, and really like the way that it sounded and rounded out the system in my car, until it freaking died! So please let me know what I should be looking at in terms of fixing this, or if I should just return the unit and get another one. If I do get another one is there something that I did wrong as far as wiring it goes that I should not do again to avoid this type of problem. Lastly WHY DIDN'T THE INDICATOR LIGHT TURN OFF? Is there any type of possibility that the RCA (sub out) from the Pioneer Head unit malfunctioned, and it is simply not sending signal to the Kenwood?

Thanks for your help, and reading this novel.

Todd

Thank's for the reply, but please help me understand this. Kenwood says to match the input sensitivity of the source (head) unit to the amp. What voltage are they looking for? My pre-outs are 6V but it does not even list 6V on the knob. It ranges from (min) 5V to 0.2V (max). As I said above I have a Pioneer DEH-740MP ( http://www.pioneerelectronics.com/pna/product/detail/0,,2076_4041_34922,00.html)

Can someone please tell me what my Input Sensitivity is? I certainly don't think that I should put the knob down to 5V (closest to my 6V Preout's) because you cannot even hear the bass that way.

The amp DID NOT work still this morning on the way to work. Same symptoms, indicator light on, fan running, no sound. HELP!

Todd

Quick Correction, my pre-out's are 4V. Hopefully this will help someone help me figure out what my Input sensitivity is.

Thanks- Todd

Yes, you are supposed to match the input sensitivity to the head output, and in your case with 4V preouts and 5V max on your amp, the "gain" should have been around 10%, just off the MIN setting, to correspond to 4V.  The purpose of that control is to allow the amplifier's input circuits to handle the high output voltage from your source and to give you full volume range on the amp without clipping.  If you had it up to 75% (which in your case would correspond to about 1V input) and you turned the head up so it was delivering near its 4V capability, I suspect you fried the input section of your amp. 

You are out of luck and the amp will need repair.  If you purchased it from an authorized dealer you MAY be able to get the repair work done under warranty.

Here's a good explaination of input sensitivity and how to setup an amp: http://www.bcae1.com/gaincon2.htm

Thanks DYohn for your input. I did start at the 5V mark as stated above, and gradually worked my way up. At the 5V (min) I could barly hear the bass at my typical max volume of 30 on the HU, so at 10% I can imagine the same results in that the bass is borderline null and void. What is the bloody point of having high volt preouts if I cannot get any bass out of the box? I'm just really upset, and mad at myself that I trashed my new amp. But please let me know why the volume of the subs are so low at what you call the correct setting, and how I correct it so it actually sounds like I have subs.

Thanks- Todd

That Kenwood is 460 watts RMS into a bridged 4-ohm load so you were delivering a max of 230 watts to each sub, or only about 50% of their rated capacity.  This would be with the head unit at full output if the gain was set correctly.  So to get the most out of a properly setup system, your volume control on your head would have to be turned up, which is its function.  If what you want is max bass at a less than max head level, you need a much larger sub amplifier (and then of course you run the risk of blowing the speaker voice coils if you happen to turn it up too loud.)  I suspect that you tuned your system by ear to your liking and thereby forced it to operate at the hairy edge of safety, and you were probably clipping the amplifier without realizing it.  The input sensitivity control is designed to be set at the MAXIMUM voltage the head can supply, so if you had it set to say 1V and were delivering 1V from your head, all is well.  But then all it takes at that point is a loud musical transient or a slight "bump" on your volume control and voila, too much input voltage and instant fried amp. 

Kenwood amps are fine performers generally.  I run one now and then (I have an old mono Kenwood coupled to a trustworthy Infinity Beta sub.)  But they are not known for being able to take much abuse.  Similar to Sony amps, it doesn't take much to blow them up - as it appears you have learned.

Thanks very much for all your help with this. I'm somewhat upset that the amp didn't have a mode of protection for that, seeing as through the instruction manual was very oddly worded and didn't say that damage would result. In any event it boils down to my ignorance, so I can't complain that much. I'll return this and get another one and not let this happen again. I'm not sure that I will be happy with the bass level though unless I get a large amp, we'll see.

Thanks! Todd

Thanks Kevin,

Maybe I'll get another Profile. In all honesty I had really good luck with thing in the last 6 years, and it doesn't mind when I tweat the gain. The have  CL 1200 which is 900X1 RMS Bridged at 4ohms. That would give me 450watts per sub RMS, which should be retardedly loud, and cheaper that this seemingly fragile Kenwood. I know Profile isn't all that great, but damn mine has lasted a long time flawlessly!