Help with a little project I'd like to do.

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unreal89

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Joined 2008
#1
Hi, I just signed up because I'm interested in getting my extra Klipsch 2.1 Promedia sub working.

Long story short I had a problem with my Klipsch 2.1 Promedia speakers for my computer. Now that they are fixed I am left with one extra satellite and one subwoofer with the box and a busted amp. I never liked how the subwoofer would distort at the higher levels. Now that I have an extra 8" woofer with a ported box I wanted to try and get an amplifier board that I can use with it to get more bass without added distortion. The subwoofer is rated for 130w RMS at 4ohms I believe. Can you guys suggest a simple chip amp that I can use with this. For input I'd like to use a headphone jack and just split my laptop's output into two and have my klipsch system plug into one of the outputs and the extra sub into the other.

I hope this all makes sense to you guys. At least enough to point me in the right direction.

Thanks.
 
#3
Well the 100W dayton amp is $100 and I do not want to spend that much. Since I have the blown klipsch amp I thought I can make a little project out of it. I could use the transformer that it has, and just build a cheap chip amp. I was thinking of maybe on of those LM4780 I believe they are 120w. I'm just not sure of everything I would need.

Can i build a chip amp using the power from my klipsch transformer and just plug it into my laptop? Or do i need a pre-amp?

Can a small car amplifier be used? I know it needs a 12v source, so maybe the klipsch transformer can provide that.

Thanks
 
#6
Hi Unreal,

What amplifier did the Klipsch module use? E.g. what chip or transistor types?

What usable parts does the remainder consist of? E.g. what transformer, what capacitors, what cooling arrangement, etc.?

A car amp usually needs a stabilized supply of relativly high current capability, something your trafo certainly won't be the best for. But ripping up the PSU connection inside a car amplifier and injecting the PSU of the Klipsch module could be an option.

Cheers,
Sebastian.
 
#7
the only chip i see says:

TL074CN
GK60116U
V6 GK CHN

and the company logo is ST

also the transistors say:

1st one:
IRF9640
I R 608P
KK Q5

2nd one:
IRF640N
I R 535P
G4 F8

those are the transistors with the tiny heat sink on the back.

There are also two 63v 4700 uF caps and two 35v 4700 uF caps.

There is also a blue box thing thats says:
GOODSKY
UDH-SS-124D

let me know if i can use these things to build a little chip amp.
As you can probably know, I don't know much about this stuff, but I'd like to experiment.

Thanks for the help so far.
 
#8
Hi,
TL074 is an opamp - input stage for the amp.

IRF9640 and IRF640 are mosfets - output stage for the amp.

These capacitors are most likely power supply smoothing. The 35V caps are most likely for a +/- 15 V supply for the op amp.
The 63V ones say the main power supply is probably in the 30-50 volts (+/-) range. This may be too much for a chip amp. You will need to measure the voltage, but first you need to educate yourself about power supplies, so that you don't get shocked.

Rod Elliot's ESP site has tons of useful information.
 
#9
The UDH-SS-124D is a relais for speaker protection.

I'd say almost all components - except for the mosfet transistors - can be reused, even for the lower power requirements of a chipamp.

But you forgot to mention the transformer. 😉

Cheers,
Sebastian.
 
#11
Because those are the components that make up the core of the old power amplifier.
And as you wanted to make a chipamp, they just don't fit in...

On another note: you mentioned the amp is busted. I thought I don't recommend reusing the parts that are busted most likely: the mosfets.

In case they survived, feel free to reuse them the way you want. 😎

But I still don't get your silence about your transformer. 😉

Cheers.
 
#16
So, is there any simple chip amp that i can build that makes about 120w at 4 ohms using some of these parts, like the caps and the transformer? I don't need super high quality sound, its for a sub. I just want to be able to hook it up to stereo jack. No need for fancy mute/volume controls. I just want it to get louder with the volume of my computer.
 
#17
Did you get that 130W RMS rating from the box or the speaker specs, or did you look up the specs for the subwoofer driver itself?

If those are just the "box specs", there's a good chance it really won't handle 130W RMS and pumping that much power through it would fry it.

Actually, I have no idea where you got those specs from. Looking at the Klipsch website for the ProMedia 2.1, it looks like the driver is 6.5", not 8", and also they claim 50W of power in the sub. Since it wouldn't make sense for a manufacturer to put in a driver with great power handling with an amp that will considerably under-power it, it makes sense to assume that the driver in that sub won't handle anywhere close to 130W RMS.
 
#18
Hi Unreal,

Why not try to repair the original amp? The parts you've described are cheap (IRF's are ~$1.50 each). The distortion you describe is probably not coming from the amp, but the speaker.
Chip amps are fairly easy to build, but they still require a lot of attention and not to mention the finicky power supply requirements.
A discrete amp (your original) will run on a wide range of power without a problem. You could conceivably replace every suspect component on the amp board, save yourself some time.
IMO chip amps are not the best choice for sub amps anyway, due to limited current capacity.
 
#19
Hmm.. wierd you're right it is a 6.5" sub. I think I was confused because I was looking into buying the logitech z 2300 after my amp blew because they have an 8" sub. Also I thought the sub was rated for 120w. I'm not sure what to do. Maybe I should forget about it and enjoy what I have 🙂.
 
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