What to look for in a car amp??

[Dan2]

hi,

i haven't bought many amps, and i have only set up about 3 so i can't say im too clued up on all the features that amps have. i know the basics, like if it's bridgeable, got crossovers etc, but is there anything i should be looking out for when buying a new amp??

please bear in mind i am a student and haven't got tons of money to throw into a new amp. i also have relatively cheap speakers - but they work and i am happy with their peformance.

at the moment i am running 4 speakers and one sub in my sedan.
the fronts and the 12" sub are connected to a 4 ch 1000w jenson amp. i want to get an amp with similar power handling.

there are 2 problems with this amp i currently have:
first, it has crossover distortion, which is not a problem with the sub but sucks on the mids.

second, there is not enough gain for the sub unless you put the bass boost on, which makes the bass very boomy, but then there is more than enough power for what i need.

so what should i look for??

[ppia600]

If your Jensen says 1000w (max), the equivalent of most US made amps would be about 50watts rms by four (200 watts). I like ppi, orion, zapco, phoenix gold for example. You should be sure to check the RMS power ratings, they are more realistic that the peak/max ratings a lot of amps give you. Also, you want a low distortion percentage at that RMS rating. RMS is pretty much the term for continous output power. Peak is just for a few milliseconds and is pretty much a useless measurement in my opinion.

[Dan2]

thanks for the info, but.....

50wrms sounds a bit low. for example, my sony 2ch amp (250w) is about 50wrms per channel (if i remember correctly) and that doesn't have as much power as my Jenson. i am not saying that you are wrong, that's just what it seems to me. ( maybe south african watts are different from US watts )

my friend has a starsound amp, 800w 4ch (70w rms), which also doesn't have quite as much output, but does sound better ( i had it running in my car for about 2 weeks to test it for him)

my amp i got for free with no manual so i don't know what it's rms value is.

so what is a low ditortion percentage?? will that include crossover distortion?? (i am not talking about the high- and low pass filters, i am talking about the distortion that can be heard when the output signal crosses from positive to negative)

[jol50]

I would guess there is something wrong with the amp if it has that type of distortion. Most amps don't even have a bias adjust anymore and the main issue is clipping at max power. Jensen is a budget amp, the ratings are not the same as a more expensive brand. Here you can find amps all over from pawn shops to ebay, if you shop some you can find a great deal. I would try to go class D on subs if you can, they require less power and wiring in the car.

The amp could be 4x50rms, that would be something like 1x150 if half were bridged on a sub if it is 75rms/ch at 2 ohms. Yeah some of those amps they reduce the gain because people turn the boost way up, or I think that is why. Personally I would not use most 4ch for subs, many don't have as much of a power supply as a 1 or 2ch does but it depends on brand.

Google the name/model and you might find a manual online.

[ppia600]

In 1999 or 2000 Jensen had some amps that I think were made in America. (maybe not) I tried to get my supervisor to order some but they always bought the cheapest stuff from some of the flea markets. The Jensens were just a hair more expensive and I still couldn't convince them. If you have one of those, I could believe 100watts rms by four but its still unlikely. Do you have the model number or maybe a pic or two?

[Dan2]

Originally posted by jol50
I would guess there is something wrong with the amp if it has that type of distortion. Most amps don't even have a bias adjust anymore and the main issue is clipping at max power.

well i did change the resistor between amp ground and power ground - it used to be 10 ohms but that gave some engine noise. i think i changed it to 100 or 1k ohm, can't remember.

i will get the model number, and i might have some pic's, i will check.

the one thing i hate about this amp is the bass boost. with it off, the gain is a little low, and with it on there's tons of low rumbly bass that doesn't seem to reach frequencies high enough to mix with my mids. some rock and dance songs seem to have no bass while others have way too much.

also, should i be looking for any kind of features on an amp? my friend's amp has a subsonic filter (high pass i think) but i don't know if its too important.

[jol50]

Subsonic is good for running ported subs hard or maybe IB subs. Ported can unload below tuning and xmax the sub easily, and IB can be limited in power handling at low frequency. It becomes a problem when you get to the sub's limits. Most newer amps have what you need with HP/LP filters and variable boost. If you need it a few can bandpass for a midbass or maybe mid. A few have parametric EQs for subs that could work nice in certain apps. A warranty and/or worthy brand is likely most important. You might be able to change the boost circuit to work better, but I've never done it.

[Dan2]

that makes sense. im using a sealed enclosure so that wont bother me.

[ke4mcl]

im a fan of linear power amps, matts, and mcintosh. macs are pricey. mmats can be had very reasonably if they are last years stock or older. they are well built. linears are very well built but getting service can be a pain and they are getting up there in age.

[Dan2]

i was in my friend's hatch the other day, he has a 2000w 4ch with a DVC 12". that had really hard hitting bass which sounded really good - only thing is doesn't know if all 4 channels are used for the sub ( 2 x bridged) and he couldn't remeber what sub it was. unfortunately i didn't get a chance to check it out.

i was thinking of gettin a 1600w 4ch - my sub is a kenwwod 12' SVC 800w so a 1600 w would match the sub (800 bridged).