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Alpine KTP-445U

Universal Class D 4-Channel Head Unit Power Pack for Use with all Aftermarket & Factory Receivers

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List price $249.95

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  • Alpine Universal Power Pack 4-Channel Class D for All In-Dash Receivers
  • Increases the output of any headunit without having to install a full size amplifier and amp install kit
  • The fast and easy solution to higher power aftermarket sound
  • RMS Power Rating:
    • 4 ohms: 45 watts x 4 chan.
    • 2 ohms: 45 watts x 4 chan.
    • 4 ohms: 90 watts x 2 chan. (Bridged)
  • Total RMS power output: 180 watts
  • Independent Front/Rear gain switch is adjustable from high to low
  • Runs off receiver's power circuit
  • High-Pass Filter: selectable 60/80/120 Hz @ 12 dB/octave
  • Fast and simple installation
  • 4 channel operation for four speakers
  • Minimum impedance of 2 ohms
  • Is not compatible with factory amplifiers
  • CEA-2006 compliant amplifier
  • Frequency response: 20-20,000 Hz
  • Fuse Rating: 15A x 1
  • Dimensions: 7-13/16D x 2-9/16"W x 1-1/2"H
  • 1-year warranty

Alpine products are warranted solely by Sonic Electronix, Inc. under the same period and terms as the original Alpine warranty. Sonic Electronix is not an Authorized Alpine Dealer and Alpine requires all merchandise purchased by Sonic Electronix customers to be returned solely to Sonic Electronix. Alpine products are also covered by our Standard Return Policy for returns on exchanges or refunds within 30 days from the date of purchase.

Product History:

Alpine KTP-445U thumbnail
(newest, current model)
Alpine KTP-445 thumbnail
(previous model, replaced by Alpine KTP-445U)

Power Specifications - Full Range Channels

RMS Power @ 4 ohms

The RMS power rating is the measure of continuous power that an amplifier can output, or a speaker can handle. It is the most accurate depiction of real, continuous power that the industry has so far.

If the final impedance of your speakers or subwoofers equals 4 ohms, this is how much power this amplifier will supply at that ohm level. The higher the RMS wattage, the more clean and loud your music will sound.

45 watts x 4 channels
RMS Power @ 2 ohms

The RMS power rating is the measure of continuous power that an amplifier can output, or a speaker can handle. It is the most accurate depiction of real, continuous power that the industry has so far.

If the final impedance of your speakers or subwoofers equals 2 ohms, this is how much power this amplifier will supply at that ohm level. The higher the RMS wattage, the more clean and loud your music will sound.

45 watts x 4 channels
Bridged RMS Power

Bridging refers to combining two channels on an amplifier to create one channel with double the voltage and an increased power output. A 2-channel amplifier will bridge down to 1-channel and a 4-channel amplifier can bridge to create 2-channels. An amplifier is most commonly bridged to drive a subwoofer.

Remember, once you bridge two channels down to one its final impedance will be 4 ohms unless otherwise specified. This rating lists the RMS power created once an amplifier is bridged.

90 watts x 2 channels

Amplifier Specifications

Amplifier Class

An amplifier increases the power of the signal being fed to it by taking energy from its power supply and matching the signal but increasing its amplitude. Amplifiers use many different methods for converting these electrical signals and have been categorized into classes.

Class A/B: Greater than 50% of the input signal is amplified while the other percentage is “off”. These amplifiers have a small amount of current flowing through the output transistors all the time which almost eliminates crossover distortion. Class A/B has great sound quality but is not as efficient as class D. These amps are most commonly used to drive speakers.

Class D: Also known as switching amplifiers, class D amps have output transistors that are completely turned “on” or “off”. This means that when the transistors are on, there is almost no voltage across them but when they are off there is significant voltage but no current flowing through it which makes these amplifiers very efficient at the cost of sound quality. These amps are most commonly used to drive subwoofers.

Other Classes: You may see classes such as GH, bD, X, FD, etc. by some manufactures. These amplifiers tend to be either class A/B, D or a hybrid of the two but with improvements to their designs that can make them more efficient or offer better sound quality.

Number of Channels
Each channel on an amplifier will power one speaker using a positive and negative cable. There are various types of amplifiers, each designed to power a certain number of speakers. Monoblock amplifiers, also known as single channel, are designed to power one or more subwoofers. These amplifiers often have very high power ratings. On the other hand, multi-channel amplifiers power multiple speakers, usually at lower power ratings. 2-Channel and 4-Channel amplifiers can power car speakers or low powered subwoofers. Occasionally you might see a 5 or 6-channel amplifier that can power speakers and subwoofers at the same time. The most common setup is a monoblock amp to run subwoofers and a 4-channel amp to run door speakers. Check out our Knowledge Base for more information.
Total RMS Power Output
Total RMS power is measured by multiplying RMS power per channel by the number of channels, and is calculated at the lowest level of operating impedance.

RMS power is the amount of continuous power, measured in watts, that an amplifier produces is called RMS power. The higher the RMS figure, the louder and cleaner your music sounds.

The RMS output figure is much more accurate than the peak rating when comparing products.

180 watts
Maximum Input Gauge Size
This is the largest gauge wire that will fit into the power and ground terminals of this device. The lower the gauge number, the thicker the wire is. For example, a 4 gauge wire is thicker than an 8 gauge wire and thus has higher current carrying capacity. Always do your best to get this size wire to reduce the risk of damage to your components.
Wire Harness
Minimum Impedance Unbridged
The lowest impedance the amplifier will handle when it is not bridged.
2 ohms
Minimum Impedance Bridged
The lowest impedance the amplifier will handle when it is bridged.
4 ohms
THD at Rated RMS Power
The amount of change in harmonic content of the signal as it is amplified. A lower figure indicates less change and a more accurate amp. THD below 0.10% is inaudible.
Speaker Level Inputs
Speaker level inputs are commonly referred to as high-level inputs and vice versa. This input type allows you to get your audio signal directly from the speaker wire in your vehicle, instead of using RCA cables. The advantage of this is factory integration, as most stock radios do not have RCA outputs to run amplifiers.
Preamp Outputs
Many amplifiers are equipped with RCA preamp outputs which pass the original music signal from the source to additional amplifiers. This is known as daisy chaining because the source connects to the first amp, and the first amp connects to the second amp, etc. The advantage to daisy chaining is you only need one 2-channel RCA cable to transfer the signal from the head-unit to the amplifier, and then one additional cable for each amp being daisy chained.
Built-in Crossover

A crossover is a type of filtering system that permits only certain frequencies to play. A Low-Pass (LP) crossover allows only frequencies below its setting to get through which is good in the case of some subwoofers. A High-Pass(HP) filter allows frequencies above its setting to pass through, this is normally used on speakers.

When a crossover is set to FULL it means no filtering is added and the full frequency spectrum is allowed through the amplifier. Filtering is important because feeding a speaker frequencies it cannot reproduce effectively creates distortion.

Signal-to-Noise Ratio
This spec compares the strength of the signal to the level of background noise. A higher value indicates less background noise.
81 dB
Bass/Gain Remote
If the amp comes with a bass/gain remote you will be able to control the level of your bass from your dashboard. Typically bass remotes also include a 16-20 ft. wire for installation.
Fan Cooled
A great feature to have if an amp generates a large amount of heat. Cooling fans can help regulate the temperature to prevent the amp from overheating (burning).
Fuse Rating
The amperage and the number of fuse(s) an amp requires.
15A x 1 
CEA-2006 Compliant
Amplifiers that have been tested to meet specific standards. When a car amplifier meets these standards, you can be sure that it will be able to produce the amount of power specified by the official CEA-2006 rating. Usually, these rating consist of the following items:
  • RMS Power
  • Signal-to-Noise Ratio

This rating applies to both external car amplifiers, as well as the amplifiers inside of in-dash stereos.


Warranty and Return Policy

Parts Warranty Duration
1 year
Labor Warranty Duration
1 year
Warranty Provider
Sonic Electronix

Summary of Customer Ratings & Reviews

Rating Distribution

5 Star
4 Star
3 Star
2 Star
1 Star

Average Attribution Rating


Centre, Alabama

Nice little amp

August 11, 2013

This amp is perfect for small places, or to hide easily where not seen. Produces big sound in a small package and a great value. I love it.

25 of 46 found this helpful

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January 27, 2013

Does exactly as it says. Look elsewhere online for better reviews, but basically works amazing. Fits in center console of 05+ Tacomas.

25 of 47 found this helpful

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May 9, 2014

decent enough for small speakers for someone just starting out and doesnt wish to upgrade battery or alternator or run amp kits, however you get what you pay for and because its not an actual 4 chan or 6 chan amp dont expect the same sound quality or power coming from this little fella. value wise its pretty good and easy to install. might cause engine whine if you have to use a in line converter or data module for your specific vehicle.

26 of 50 found this helpful

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Melbourne, FL

An absolute BEAST in a tiny package!

January 19, 2014

This thing cranks out some serious juice from such a small box. It's about the size of a red brick. It can be stashed up in the dash so you never even see it. And it makes WORLDS of difference.

It can accept low-level (RCA) inputs or high-level (speaker wire) inputs. (Just cut off the RCA tips, per instructions) It also has adjustable high pass filters for front and rear. (via DIP switches) Adjustable gain for front and rear. (via knobs)

This thing ROCKS. Unless you're planning on getting huge 4-channel amp that does at least 100WRMSx4@4ohm, then just get this. It's just as good as anything below that power range, despite what the figures on this may lead you to believe. I honestly think the power output is underrated. You WON'T be disappointed.

24 of 46 found this helpful

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Great Product for entry level setup!

January 6, 2014

After building several full all out setups on my previous vehicles, I wanted to try a more simple build for my current car since I don't want to spend too much time running new wire, mounting amps, etc. and I do not have the luxury of putting a sub since I need the cargo space for work.

I was hesitant getting this amp since I thought it would only give a little more than an aftermarket headunit and heat up, but I really liked the size of it (tucked behind the glovebox) and how simple it is to wire it up. I installed it today with a pioneer headunit, JL TR components in front, JL TR coax in rear, all doors deadened, gave it a good tune by ear and to my surprise it sounds great! Well 50x better than my base unit and stock speakers.

The sound is nice and clear, has a good thump, no noise or muddy sound and I can hear all the sounds I was looking for (just over 1/2 gain) that my stock stuff could not even come close to producing. I definitely recommend this amp to anyone who is looking to do a simple upgrade on their system without the hassle of running new wire and looking for a place to mount or hide a traditional sized amp!

23 of 45 found this helpful

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J. Escuela


not bad at all, great for factory speakers and entry level after-markets

September 20, 2013

would have bought from sonic, but were out of stock. bought from bestbuy instead. installation was surprisingly simple. wired into a single din pioneer with 3 rca level outputs (front, rear, sub - used front and rear obviously) with two 3 ft rca cables from radio shack. wired output into Scosche TA02B / TA02 and connected that to factory harness (speaker level, ground wire, batt, and remotes). worked flawlessly, made factory speakers sound phenomenal...almost to the point where i second guessed my purchase of new JL C2 sets...but added the JL's anyway and, big surprise, they sound great as well. instructions are a little convoluted but its fairly simple to install and use once you start. only problem now is finding a spot to mount it (its jus sitting in the glovebox). and yeah, the wires are short...not a huge issue if you purchase longer cables to go with it. very happy with it tho, would definitely recommend.

20 of 39 found this helpful

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Great if you Don't want wiring all over the car.

May 12, 2013

Really great product, i have a sets of Polks components 6,5" DB series in the front and DB 6,5" coaxial in the back, this little thing makes the job done, the speakers sound really loud without any distortion if you EQ well.

The price is fair and the Shipping To Chile really fast, i installed in a Suzuki SSwift Sport 2013, and with a limited space behind the dash, have to put it far from the source, so the wiring was not long enough, had to put new wire... i recommend to install it in a professional place, it seems easy to install but, removing some parts of the dash and trying to drill a base for the amp, that was the challenge.

The sound is good, very good for a Class D amp, so Don't expect audiophile sound. My source is a Panasonic OEM radio , not aftermarket, so i have to move the gain to have a louder sound, but try to do this with care, it's too sensitive and if you gone wrong with the right gain, it will distort at some points... and not, the speakers are 110 RMS and 50 RMS, so the distortion is not from them.

I recommend this amp if you don't want to go big, and don't want to wiring the entire car to put a amplifier in the back and then wiring again to the doors.

Soon i'm going to put a subwoofer, so the frequency selector to cut at 50-80 Hz it's a really great tool.

Good deal here.

22 of 43 found this helpful

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North Las Vegas, NV

Good full range amp

April 24, 2015

I bought this amp back in August 2014. Installed it in my jeep. It was a straight forward install. It powers my 6.5 components and my 6.5 co-axial speakers.

7 of 15 found this helpful

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Lake Havasu City

Exceptional Quality

September 18, 2013

I bought this little amp to work together with my Alpine system, running Rockford Fosgate speakers front & rear. This system sounds really great. I did not want to install a huge amp under the seat or in the trunk, so this little Alpine fit my needs perfectly. Because it only puts out a true 45w X 4, I went with a lower end speaker selection of Punch P1462's in front and P1692 in back. This system sounds so good, I love listening to my music in my car. So clear & crisp. The power is more than enough, so easy to install and tuick away, requires so little space, no one even knows its there. Draws very little battery power and so far after two years, it doesn't miss a beat. I would recommend to anyone looking to save a few bucks and install a very easy system in your vehicle without no hassle what so ever.

16 of 33 found this helpful

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Des Moines, IA

Alpine KTP-445U

January 9, 2014

At first I didn't think this amp would sound that different than my stereo, but the extra 45 watts really brought my speakers alive. There is more bass, and the sound is so crisp and clear. Plus it fits in my glovebox and doesn't require an amp instillation kit. It's seriously perfect for anyone not wanting to deal with installing an amp kit. You wouldn't think this would do much to your speakers but you just have to try it. It is awesome!

25 of 54 found this helpful

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Murrieta, ca

Great little amp!

June 25, 2013

I purchased this amp for my Volkswagen GTI. My speakers are all factory, which consists of a 6.5" driver, 4" driver and a tweeter in the front and a 6.5" driver and tweeters in the back. This amp fit behind my head with ease! The European factory system sounded decent but this amp really made it come to life! The speakers have more clarity and definition! I definitely recommend this amp!

20 of 44 found this helpful

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chicago, IL


March 9, 2014

Bought this amp because my factory radio was lacking power, hooked this bad boy up and the music came alive. Sounds outstanding!

22 of 49 found this helpful

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Brooklyn, New York

Worth the money

May 8, 2013

Brought my infiniti speakers to life! Tucked neatly in the dash of my 96 Impala. My stereo sounds better than my dads chrysler 300

18 of 41 found this helpful

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freehold, NJ

Amazing AMP!

May 15, 2014

this little amp is outstanding! way better than my 4 channel that was a size of a desktop! I bought a 2013 sonata gls all stock and the oem system sounded horrible so i decided to shop around for a small amp to tuck away behind the dash. I ran the power and gnd right off the stock decks power and I used the speaker level inputs which tied into the oem harness. i had to butcher due to the lack of aftermarket adapters. i guess no one likes hyundai! I had it for 6 months so far and i abuse this AMP. the gains are half way and it's pretty loud to the point where my ear drums starts to ring. this has filters 60/80/120 and off. For best overall sound highs crisps mids and deep low bass i had to turn the filters off. My music is reggae soca hip pop and house. My front speakers are Renegade RX62 6.5-Inch 2-Way Full Range Speakers and the rear are Kickers DS60 6.5 speakers. Do me a favor dont waste your money on a 300 dollar amp that fits under your seat which requires 4 gauage wire and all that crazy stuff it's not worth it. After all are you going to park your car inside a club and dj there?

20 of 48 found this helpful

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Accessory Tools and Products

Accessories added

NVX XBG3PK 1/0 Gauge OFC Big 3 Upgrade Kit

Comes with everything you need to upgrade your power and ground wire.

Your Price $79.99

Kicker Big 3 Package 1/0 Gauge Big 3 Upgrade Kit

Get all you need including wire cutters to upgrade your power and ground wire.

Your Price $151.99

Belva BBG3KT CCA 1/0 Gauge Big Three Kit

Features everything needed to upgrade factory power and ground wire.

Your Price $39.99

Small Universal Remote Level Bass Control

The Scosche RLC is a smaller universal bass remote that connects via RCA inputs.

Your Price $11.99

NVX XDBU4 - Top of the Line!

Distribution Block with Two 1/0 or 4 AWG Inputs and Four 4 or 8 AWG Outputs

Your Price $17.99

StreetWires ZN7 RCA Interconnect Cable

16.4 ft. of 4-Channel RCA Cable with hyper twist construction, oxygen free copper, and precision machined tips.

Your Price $59.99

Kicker 4-Channel RCA Audio Interconnect Cable

4 Meters (13 ft.) 4-Channel K-Series RCA Audio Interconnect Cable

Your Price $19.95

NVX XWS1650 Speaker Wire

50 ft. of True 16 Gauge 100% Copper EnvyFlex Speaker Cable/Wire

Your Price $29.99

NVX XWS1625 16 AWG Speaker Wire

25 ft. of True 16 Gauge 100% Copper EnvyFlex Speaker Cable/Wire

Your Price $13.99

Belva BBSW127 12 AWG Speaker Wire

12 Gauge 7 Meter (23 Ft) Speaker Wire (CCA)

Your Price $14.99

Belva BBSW167 16 AWG Speaker Wire

16 Gauge 7 Meter (23 Ft) Speaker Wire (CCA)

Your Price $12.99

SMD DD-1 Distortion Detector

Set the gain of an audio amplifier quickly and accurately

Your Price $149.99

Scosche SPL Meter SPL1000F

Handheld boomSTICK measures your SPL range from 60 to 135 dB

Your Price $21.99

Browse 9 questions and 29 answers
Hide answersShow all answers | Sort by
Why did you choose this?
Sonic Electronix Store
Best compact amp out there! Easily fits behind most stereos in dash.
Rory O on May 14, 2015
will suffice until i can install a full blown amp and subs (or at least better then the head unit alone.....
Keith S on Dec 22, 2014
Wanted to amplify my front and rear speakers without needing a big amp or wiring kit and 45rms x4 channels is good enough for now so I thought I would give this a shot.
Darius P on Jan 20, 2015
fits in tight places
wayne c on Nov 6, 2014
Hi there, I am wanting to look at using this for a set of Apline SPR-60C components up front, and SPR-60 coaxials in the rear. since the speakers are rates 110w and this 45w, am I going to be causing damage by underpowering them? Cheers
Ben W on Sep 9, 2014
Best Answer: Hello Ben,

Out of the box and right away, this setup will Not cause any damage. However, obviously DON'T expect a 100w+ experience per speaker. If you push the Amp to Clipping, then THAT will cause damage to Any speaker. Really the only "concern" here - besides clipping, which is on you not the product - is that you are going to spend your budget on a set of speakers that are at their Optimum Quality when being power 75-100% of what they ask for; ~45w RMS will be under 50%. A better 'match' will be the S-Type series, but that - like all things Car Audio - comes down to Your preference.
Reply · Report · Customer SStaff on Sep 9, 2014
· Add Answer · I Have This Question Too (1)
If I choose to run the the amp in the "2 channel" mode would that be 90W X 2 instead of 45W X 4?
Jon K on Sep 30, 2014
Best Answer: Hello,

There are two ways to answer this, so please read carefully to get the answer to your specific approach.

1) If you only use, say, Ch 1 & 2 , but do not use Ch 3 & 4 , you will only receive 45wRms per channel.

2) If you Bridge (Ch 1 w/ 2) & (Ch 3 w/ 4) THOSE newly created Two channels will provide 90wRms .
Reply (1) · Report · Customer SStaff on Sep 30, 2014
· Add Answer · I Have This Question Too (1)
Hey guys, will this product work if I have a line out converter as well? I drive an 09 Chevy Impala with the factory head unit (hence the LoC). The Line Converter is PAC AOEM-GM1416A. Thanks!
A shopper on Feb 2, 2015
Alpine KTP-445U
Alpine KTP-445U
Best Answer: I initially had an AudioControl Lc2i between my factory head unit and the Alpine amp. I ended up taking the Lc2i out and running high level inputs from the head unit to the Alpine. I honestly believe the sound is better without the line converter inbetween.
Reply · Report · Shane B on Feb 3, 2015
· Add Answer · I Have This Question Too (0)
So I have a aftermarket JVC head unit that puts out 22rms x4channel, would this alpine amp just add more rms so would it be 45+22rms to equal 67rmsx4channel ?or would the speakers only get 45rmsx4channel and not include the power of headunit?
Simpson29 on Nov 19, 2014
Best Answer: Hello Andrew,

You ONLY get what the amp Provides. In this case, it will in fact be the 45w RMS x 4.
Reply · Report · Customer SStaff on Nov 22, 2014
· Add Answer · I Have This Question Too (0)
Im thinking about purchasing this but my factory speakers are part of a bose system....what do you suggest??
A shopper on May 29, 2015
Best Answer: Your bose system probably sounds better without this. If you're looking to upgrade get a proper 4 channel amp and upgrade the entire system
Reply · Report · piyush s on May 29, 2015
· Add Answer · I Have This Question Too (0)
Im trying to hook this up, any tips on how to do this?
Dustin D on Dec 29, 2014
Best Answer: If you've never wired up an amp before look on YouTube for a how to video, or take it to a stereo shop and have them do it before you blow something up. It's pretty straight forward. Power, ground, turn-on, and plug the rcas in.
Reply (1) · Report · Alex M on Dec 29, 2014
· Add Answer · I Have This Question Too (0)
can this amp be bridged to 2 channels @ 2 ohms? For 90x 2
A shopper on May 11, 2015
Best Answer: No, it cannot. Bridging the amplifier will obligate the setup to a 4ohm final load and above. Anything less will harm the amp and void the warranty.
Reply · Report · Rick MStaff on May 11, 2015
· Add Answer · I Have This Question Too (0)
If I am using the KTU-445U connected to a head unit that has 2V outputs compared to a unit with 4V outputs does it make any difference in quality of sound? In otherwords can I go with a less expensive HU with 2V outputs and not notice any difference in sound quality because I am going through the KTU?
b m on Jan 10, 2015
Best Answer: Thank you.. Being I am spending a fair hunk on the new system, it sounds as if to keep the monster inside of me at bay I better use a 4V system.. lol..
Reply · Report · b m on Jan 12, 2015
· Add Answer · I Have This Question Too (0)

Product Summary


Model Number






Internal SKU


Internal Product ID


Sonic Electronix Wiring Guide

Wiring Diagram Legend

Warning: The image depicted shows the resistance change when wiring multiple subwoofer terminals. Please refer to your subwoofer's owner's manual for the proper wiring of its terminals. Sonic Electronix, Inc. is not responsible for damage caused to your audio system or vehicle due to improper installation. Please call tech support at 1-877-289-7664 if you require additional assistance.

Product Name: Alpine KTP-445U