PROJECT: Louder Blaster

Over the past few months I have been pondering a project on how to boost power, performance and of course VOLUME!

3 Months ago I bought the GPX 990. It's a very large box, with 8 inch speakers, roughly the size of a Lasonic TRC-931. In my opinion it's a gorgeously designed box in classic 1980's silver paint, aluminum control panel with a nice large volume knob, large analog tuner, analog VU meters and lots of chrome.



Unfortunately, this radio was a big empty giant! Empty inside and empty on power. The large 8 inch speakers that were in it were from the 931 and distorted at 3 on the volume knob, no bass to be had at all and very thin in tone.

After having the box apart for cleaning I started thinking of how I could upgrade this system and get some real performance out of it.

What I did was open up the radio and I added a small but powerful BOSS 200 watt 12 volt car stereo amplifier and two new 8 inch 4 ohm Kicker Free Air sub woofers with MASSIVE magnets. The amplifier is 100 watts per channel and I ran the stereo's speaker leads out of the GPX amp into the "HIGH Input" on the amp, meaning it won't fry the new amp yet I can control the new amp with the volume knob. All functions remain the same, bass and treble controls, balance left and right all remain the same.

You will see the speaker modifications I needed to make to get the speakers in, the other electronics that I had to move to make space for the MASSIVE Magnets, how I had to move and rewire the power supply, create wiring harnesses for the new power supplies PC board location, wiring for the amp board as well as finding a location to mount it, wiring up the power switch and over coming the fact that the GPX is a 13.5 volt 9 D Cell system and the new amp is a 12 volt system = 8 D cells. The new speakers are wired in with nice heavy gauge wire, all contact points soldiered and all wiring neatly zip tied in place to prevent vibrations or rattles.

The out come of this project is STAGGERING! This Radio is going from mild to MONSTROUS! It will not only live up it the potential one would expect from a Blaster of this size, it will SHATTER IT!

Below is the project in stages on you tube.

[youtube]zo9HsQIRjqo[/youtube]
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[youtube]bF2UpfXP2bc[/youtube]
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[youtube]IhGT5phi-qY[/youtube]

Stay tuned as there is much more to come as I get this project finished and get the video's posted online!

You should probably leave it at 9 batteries if you're using a 12 v car amp. Alkaline batteries are 1.5 volts for a very short time and average more like 1.25 volts over their life. Car amps are built to take 14-15 volts max as the alternator operates at a higher voltage so there's no risk at 13.5v.

I want one

spectacular project and success story
and-- thats such a great looking box --
so worthy of any and all upgrades

Good project. I don't think I'd ever want to ship that boombox though. I'd be too nervous.

great project. Can't wait to hear the report on how she sounds. Are you upgrading the tweeters as well?

Thanks for the comments....More video's coming soon!

steedums said:

You should probably leave it at 9 batteries if you're using a 12 v car amp. Alkaline batteries are 1.5 volts for a very short time and average more like 1.25 volts over their life. Car amps are built to take 14-15 volts max as the alternator operates at a higher voltage so there's no risk at 13.5v.

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You know this ran through my head! All my testing with the amp wired up has been at 13.5 volts as I figured that the amp could take a little without causing damage and I did think about the fact that a car alternator varies in voltage. I figured it would be more robust.

petergriffin said:

great project. Can't wait to hear the report on how she sounds. Are you upgrading the tweeters as well?

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I did not up grade the tweeters as they actually seem fine and the radio has a ton of mid's and high's, now it has the lows to go with it!

Am I the only one thinking that NED209 would be so proud?

Lookin' good so far, Chris! I can't wait to see the video with it bumpin'.

wow that is a awesome project one thing thou dont forget to add a small piece of aluminum for the ic on the amp even a small piece would work fine that must be the best mod i have seen,,

Yes.


Cheers OSS

I had the same idea..just never got a donor to work on

Excellent project!!..and the magnets on those speakers are huge...can't wait to see, and hear, more...

monchito said:

wow that is a awesome project one thing thou dont forget to add a small piece of aluminum for the ic on the amp even a small piece would work fine that must be the best mod i have seen,,

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GOOD CALL MAN! The original amp packaging had one and I needed to find a way to attach it...But I will make that happen!

It's a cooling issue correct?

Here are some more video's on the project...Almost done!

[youtube]J3N4ZtCLCnY[/youtube]
[youtube]kHGuqOJ5w54[/youtube]
[youtube]owx8--XAhr8[/youtube]

The final video's....the complete project

[youtube]i4niNzUNXkk[/youtube]

CAN YOUR BOOM BOX HIT AN 808 NOTE? LETS FIND OUT IF THIS ONE CAN!

[youtube]aWQyF0c0LSA[/youtube]

So there you go, the completed project....I hope you enjoyed watching the video's....on to the next one!

Lasonic TRC-920 said:

The final video's....the complete project

https://www.youtube.com/watch?v=i4niNzUNXkk

CAN YOUR BOOM BOX HIT AN 808 NOTE? LETS FIND OUT IF THIS ONE CAN!

https://www.youtube.com/watch?v=aWQyF0c0LSA

So there you go, the completed project....I hope you enjoyed watching the video's....on to the next one!

Click to expand...

OMFG Chris, top job on the modification & top job on the videos as well.

Nice to put a face to the user name after chatting in the Boom Room so many times.

I could feel that bass thru my computer speakers man, and I see you didn't even turn it more than a quarter of the way up!

Oh yeah baby! Nice.

Lasonic TRC-920 said:

monchito said:

wow that is a awesome project one thing thou dont forget to add a small piece of aluminum for the ic on the amp even a small piece would work fine that must be the best mod i have seen,,

Click to expand...

It's a cooling issue correct?

Click to expand...

Terrific Job! Didn't follow all the videos until just now because there was so many. It might be a little late but I have a few notes and suggestions for you.

(1) It looks like the original power switch is used to power up the car amp too, is that right? While it may work properly now, for long term reliability, I highly suggest you use the original power switch to power ONLY a relay to switch the amp. The reason is that these puny switches are not designed to switch that much current. The initial power on surge could be tremendous. Over time, arcing will eat up and destroy the switch internally. I don't think replacement switches are going to be easy to find.

(2) I wouldn't worry about 13.5 volts being an issue since the car amp should easily handle that. I'd be more concerned that the AC transformer and power supply might not be powerful enough to provide the current necessary for sustained operation without overheating. However, my guess is that on AC, the actual rail voltage will be MORE than 13.5 volts, which is the battery voltage of 9-D cells. Most system voltages on AC is about 10-20% higher on AC than DC. You should check it. Anything much higher than 15 volts might be cause for concern. Alkaline D cells however, have plenty of current capability. I have read that a typical alkaline D cell can output 10,000mah. That is a lot. But battery life probably won't be very good when drained like that.

(3) Ramon was right on about the aluminum. Except that I'd suggest a much larger piece. Many people don't know this but the fancy aluminum case of car amps serve more than just a packaging and cosmetic purpose. The entire case of the car amp is actually the heat sink for the amp. That's why you often see car amps have lots of fins. It looks like you stripped the entire case off from the board. You have it working right now so I guess it's working for you and I'm not going to second guess that. But I highly recommend a very substantial heat sink to carry the heat from the IC chips. Those output devices sink a lot of current and could overheat rather easily. Once again, for sustained long term reliability, consider adding huge heatsinks to those IC's. If you look carefully at how the original IC's were mounted, I bet that it was done in such a way that the heat is drained away from the chip and into the finned aluminum housing, which is now gone. Until you add some heatsinks, I would take it easy.

As an example, right now, this is the BTL amp that I built for another member's Rising. We decided to do this project because the 20/20 is far underpowered for such an imposing looking boombox. This module is comprised of 4 Class A/B amps with 2-pairs running in bridged mode. The input signals will be taken from the low level signal from the original amp location. As you can see, the amp boards themselves are quite small but the entire module is almost all heatsinks. This module can probably be run at full blast forever without any concern of overheating. Finding enough room to shoehorn this in might be the only issue. If space becomes an issue, I will then work on downsizing the heatsinking package but only if space is an issue. Estimated power output will be 20-watts RMS / channel. Maybe when it's done, he will provide a write up on it.

Once again awesome job, and the results look terrific.

I'm LOVIN' it bro, really, excellent job on the vids and the mod OF COURSE!

Cheers, and now get a few brews and head out to the park with that biatch!!!!!!

Hey Super,

Thanks for all the great advice. I have a feeling that this project is going to be an on going effort to not just build a powerful box but make it real world use able.

Heat Sinks....CHECK, I need to open up the box to do some work and I have a few GOOD heat sinks off some computers as well as all the parts off the original amp casing. Can I GLUE the heat sink to the IC's?

As per the power switch, Right now I have the amp wire "Power" to "Power", "Ground" to "Ground" and the "Amp On" switch running off the hot line I found for the power switch to the switch the amp on. What do you think about running the low voltage power from the switch to a relay and then running all the hot power through the relay?

I'm not sure what this thing will do on batteries or how long it will last. I have a few technical hurtles to over come before I can put this thing into service and see how long the batteries will last, but I am getting closer.

I am really considering mod'ing in 8 more batteries and running the amp only on them. As I mentioned, the rechargeable batteries are half the weight of regular D Cells, meaning 16/17 batteries is still the weight of 8/9.

We'll see. It's still weigh's less then the 777z.

As of right now, I have a small laundry list of things to handle along with whats above, including

Deck Belts
VU Meter diode
Move the amp green LED to the front and use as a battery light
move the amp power adjust knob to a place where I can adjust it

Terry said:

Lasonic TRC-920 said:

The final video's....the complete project

https://www.youtube.com/watch?v=i4niNzUNXkk

CAN YOUR BOOM BOX HIT AN 808 NOTE? LETS FIND OUT IF THIS ONE CAN!

https://www.youtube.com/watch?v=aWQyF0c0LSA

So there you go, the completed project....I hope you enjoyed watching the video's....on to the next one!

Click to expand...

OMFG Chris, top job on the modification & top job on the videos as well.

Nice to put a face to the user name after chatting in the Boom Room so many times.

I could feel that bass thru my computer speakers man, and I see you didn't even turn it more than a quarter of the way up!

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Hey Terry, yeah not many of us have faces on here....we all know our radios and yet we'd walk right past each other at the store!

Yeah, I'm barely cracking the volume knob....It's a nasty Mo Fo....once I do some more tests and feel like I have things worked out, I will let that volume knob ROAR....I can't wait....

Chris