Question about Pyle PLA4240 Car Audio Amplifier

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Overtightened lpf knob

I was adjusting the frequency on my lpf and i overturned it and the sound just kicked off is there any way to fix the knob

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Re: overtightened lpf knob

It seems like the POT is going to have to be replaced if it is broken, if the LPF won't adjust when you turn the knob eighter side then it is broken.

Posted on Jan 07, 2008

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Is there a crossover in the ada885 sub box do i disconnect when using external amp

usually the external amplifiers have potentiometers that you can adjust called sub sonic and LPF. Find what your sub needs to be setup to and set the LPF to that frequency, usually 40-60hz.
Find the tuning of your box or the sub sonic frequency cut-off and set it there. usually 30hz and under, this will keep your subwoofer from unloading and damaging itself.

Nov 10, 2013 | Car Amplifiers

1 Answer

The recommended settings for a mofet car amp 50.4 , theres a few knobs not sure what they should be turned to

The gain knob is used to control how much the volume (output) of the amp increases with each increase in volume on the deck (installed in the dash). This is used to match speakers running of your deck. Other knobs are probably for a crossover (labelled in Hz). This controls what frequencies are passed to the speakers connected to the amp. A Highpass (HPF) crossover passes all frequencies above what the knob is set for. A Lowpass (LPF) pass all frequencies below what the knob is set for. A HPF is typically used when the amp is powering component or full range speakers to keep the ultra low frequencies (anything below 90Hz) from going to theses speakers. A LPF is used when the amp is connected to a sub. Subs dont handle higher frequencies very well.

Nov 02, 2013 | Crossfire Car Amplifiers

1 Answer

Is the bass boost the gain or frequency knob?

Bass boost simply adds DB or gain to the bass signal. Some like it, some dont.
The frequency knob is the Low Pass Filter (LPF) that cuts off the amp output above
the set frequency. A bass system usually cuts off below 400 HZ and more often 200HZ.
A good, rattle your car bass note is in the 25-80HZ range or lower but most amps and audio
input devices cant attain a good low note with clarity.
"Low-pass filter allows only frequencies below the crossover point to be amplified. A high-pass filter allows only frequencies above the crossover point to be amplified - useful for keeping low bass away from small speakers, so they can play more efficiently."
Checkout Crutchfields Glossary of Car Amps.

Mar 14, 2011 | Rockford Fosgate Car Amplifiers

1 Answer

What is the best adjustment for a Nitro BMW 481 with one 12" Memphis subwoofer?

First you need to determine what kind of subwoofer it is and by that i mean, is it a dual voice coil subwoofer or a single voice coil sub woofer.
Dual voice coil(DVC)
Depending on how many Ohms each voice coil is you will have the amplifier drive a specific load (4OHM stereo (75 RMS x 2) 150RMS total power / 2OHM stereo(100RMS x 2) 200RMS total power) Connect each voice coils separatley to each speaker output of the amplifier for this configaration. Always making sure that the + & - of each voice coil go to the coresponding location of the speaker outputs of your amplifier.

If your sub woofer is a single 4OHM voice coil then your cables should be connected to the coresponding location on your amplifier which states "BRIDGED" It is marked clearly on the speaker outputs of your amplfier.

If it is a 2OHM then do not connect it to the amplifier. The specific amplifier is not stable at 2OHMS bridged and will most likely get damaged if you try to operate it at that OHM load.

On the side of the amplifier where the adjustments are there is a switch that indicates X-OVER. (LPF/HPF/FULL) Make sure to set it to LPF (Low Pass Filter). (not doing so can damage the subwoofer)
On the left hand side of the X-OVER there is the adjustment for the LPF (30-250) the best setting would be at the same frequency that your speakers stop
If your speakers have a frequency response of 60Hz to 20KHz then setting your LPF to roughly 70 to 80 will be ideal. The rule is that where one speaker drivers frequency ends, the other must continue in order to complete the full range of audible frequencies.

if you have any more questions feel free to ask.

Feb 05, 2011 | Nitro BMW-481 Car Audio Amplifier

1 Answer

Mtx 801d amp turns on but no bass just high pitch sound sub is fine

if theres a switch on ur amp that says LPF Full or HPF put it on LPF for low pass frequencies

Mar 16, 2010 | MTX Thunder 801D Car Audio Amplifier

2 Answers

I have a pioneer gm-x 304 amp. I want to know what are the lpf-off-hpf switches for< and what sdhould I set the input levels to?

Hello packs6,

The lpf-off-hpf switches control the "low pass" and "high pass" filters. When driving full-range or component speakers the filters are usually operated in the "off" position to send all frequencies to the speakers. When driving a subwoofer, the best position is "lpf". If you have a separate amp to power a subwoofer, this amp can be used just for the high frequencies by putting the switches in "hpf".

Input levels should be adjusted to match your receiver output. You don't want the levels so high that distortion results. But you want it high enough for the amp to be able to produce maximum output. Start at about midrange and adjust the receiver volume to a little higher than a comfortable listening level. Adjust the amp gain (level) counterclockwise until you begin to hear the speakers distort. The turn the control slightly clockwise until the distortion disappears. That's the best setting.

Hope this helps.

Sep 02, 2009 | Pioneer Car Amplifiers

1 Answer

What do hpf and lpf switchs do

Hello rwalinske, The abbreviations "hpf" and "lpf" stand for High Pass Filter and Low Pass Filter. They do exactly what their names imply. They allow frequencies above or below a specific setting, while blocking or attentunating frequencies below or above the setting. There's also a "band pass filter" which allows frequencies within a specific range below the high setting and above the low setting. Finally there's a "subsonic" filter which blocks inaudible frequencies below the threshold of hearing. The hpf is generally used in speaker component systems to send the high frequencies to the tweeters. The lpf is normally used with subwoofer systems and is set to send frequencies below the setting to the subwoofer. While most amps will amplify a wide range of frequencies, they are more efficient when the range is limited depending on their intended use. For example, a typical 2-channel amp might have a frequency response of 20-20KHz. When used to drive a set of normal speakers, you would not use either the lpf or the hpf, but simply let it send all frequencies to the speakers. But when used to drive a subwoofer, and operated in "bridged" mode, the amp can put all of it's amplifying power into frequencies than can be used by a subwoofer if the lpf switch is turned on. Hope this helps.

Jun 05, 2009 | Sony Car Amplifiers

1 Answer


Hello again ronnieyannon,

It's probably best to allow the amp that is powering the subs to control the frequencies going to the sub(s). I would not use the lpf on both the head unit and the amp in any case. The control settings are not completely precise and you could end up with a lot of tweaking between the units to get the sound you want. I'd send full range to the amp and with it playing something with a lot of bass, set the 401s to "LP", the crossover slope to near maximum, and then adjust the frequency until it sounded best to me. Starting on page 11 of your manual are the Rockford-Fosgate recommended adjustment procedures, including setting the gains and the filter frequency.

Those numbers for the lpf on your head unit sounds like it allows you to decrease (-24dB), as well as increase (+6dB) the bass at the specific frequencies of 50, 63, 80 and 100Hz. You probably don't want to decrease the bass boost for subs. And the 401s will allow a boost up to 12dB and is variable from 50-250Hz.

Hope this helps.

Apr 24, 2009 | Rockford Fosgate Punch 401S Car Audio...

1 Answer

My Sub Doesnt Sound Good

The settings are all pretty much dependent on your ear. But some guide lines would be for the input gain, never turn it all the way up. Turn the gain up about half way possibly 3/4 of the way up. There should also be a filter, if you are powering subs then you want to filter out any high frequencies. So if there is a switch saying HPF or LPF you want LPF (Low Pass Frequency). Then there should be another "knob" that controls the frequency. At the least, you want your sub amp to be tuned below 50 Hz any lower is up to your ear. I hope this helped.
-Andrew Hawkins

Mar 28, 2008 | Rockford Fosgate Punch 500a2 Car Audio...

1 Answer

Overtightened lpf

Yes. but it wont be cheap to pay some one to do it. Call around to the local stereo shops find out where repairs are done in your area. Then go there ask to speak to the person that does the repairs then offer him like 20 bucks to do it on the side. Doin it your sellf I would not recomend. The input adjustment on an amp is very touchy and if you use to much solder, or to little, or jump a connection on accident or whatever youll end up with some serious noise instead of music.
Good luck buddy

Dec 25, 2007 | Sony Xplod XM-554ZR Car Audio Amplifier

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