| JCoffey |
| I have an amp that I purchased about 6 years ago for around $100, that is a really nice sounding little amp made for Computer sound systems( although it makes a great little integrated, with a bypass for the EQ). I just found out last night that it uses 2 LM3876 chips. Problem is, it hums. It's not very quiet at all. I really like the sound, but dont like the noise. I snapped some pics of it last night, and was wondering if some of you gurus can look at the pics of the layout, wiring and topology and come up with suggestions of things to check. I looked at the grounds a couple years ago, and tried to clean them, but it do any good. Any other suggestions? |
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| JCoffey |
| Here's the front. Aint pretty, but it works. |
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| JCoffey |
| Heres the topology. They transformer makes this little thing weigh a ton. |
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| JCoffey |
| Heres the pair of LM3876TF chips |
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| JCoffey |
| Herss the Preamp, eq section. |
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| JCoffey |
| Here are the inputs. |
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| JOE DIRT® |
I have one suggestion for you...unscrew that input board at the back and look for some cold solder joints on the bottom.....I had a sony A/V receiver that was humming every once in awhile.....I touched up all the joints and never had a problem again
Cheers!!The DIRT® |
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| JCoffey |
| at the risk of sounding like a NOOB, What do you mean by a cold solder? I notices that night that one of the 4 blue caps by the ICs, is loose on the board. I need to fix that right away. i'm just curious if all the little gizmos, like the output level leds, the eq, the eq bypass, Sub out Mike in, etc is causing too much interference. |
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| JOE DIRT® |
I was referring to a cold solder joint...it can happen after repeatively plugging in and out at the back.....if you have a loose capacitor then definately solder that.....while your at it inspect the rest of the bottom of the board and touch up any joints that dont look good....its just something simple causing your noise....the amp is definately worth fixing it has a hefty power supply
Cheers!!The DIRT® |
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| JCoffey |
| Oh I definately want to get it working like it should. The sound is really good, I love the fact that it has a pair of inputs, and that it has a built in pre amp, headphone jack, and sub out, makes it even better. I wish I knew more about electronics than I do, cause if I did, I'd rebuild it with only the parts I wanted, and leave off the ****.Still, not a bad amp for only $100 |
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| JCoffey |
| Oh I definately want to get it working like it should. The sound is really good, I love the fact that it has a pair of inputs, and that it has a built in pre amp, headphone jack, and sub out, makes it even better. I wish I knew more about electronics than I do, cause if I did, I'd rebuild it with only the parts I wanted, and leave off the ****.Still, not a bad amp for only $100 |
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| JCoffey |
| Sorry about the double post. Not sure what happened. Well, I checked the input board, and all the solders look fine. I need to get a jewelers screwdriver to get the heatsink off, and I'll check out the rest of the board. I was wondering though, I've been dealing with car audio for a few years now, and one of the biggest forms of noise is signal wires being too close to power wires. Could that be casuing the problem? |
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| Cradle22 |
Hi!
The amplifier section should be OK sounding, but the Pre-Amp could be crappy...
Take a look at the ICs in the pre amp, what OPs are used?
Maybe substitute them for better ones...
Maybe bypass the equalizer...
Budget hifi often uses crappy OP amps for preamp, and cheap euqalizers do not enhance the sound like they should, they rather make it worse... |
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| karma |
allso if you get a chance try making the sheilded wires going to
rca's longer and moving them away from the transformer they look a little close. one thing i would do is just find somthing to sheild the transformer. try a small pot from the kitchen. sounds weird but it worked for me;) in the past
o and some better brand of caps helps to
what's the brand name of the amp? |
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| JCoffey |
well, after some research, All I could come up with is that the company is (was) called Micro Multimedia Labs. The Model of course is the TC-1490. It actually one PC Magazines #1 for multimedia packages, when it was purchased as a set with a matching powered sub, and two bookshelf speakers.
I was able to track down a number but the company doesnt apear to still be in business.
I agree that the Pre-amp could be cuasing the problem. There's just too much junk there. and I'll also try to make the cables longer. Any suggestions as to what brand of high quality wiring should be used? (without breaking the bank of course) |
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| karma |
leave the sheilded cables for last. try replaceing all 4 caps first one may be dried out or bad. if it was me i would just pull it apart and make a gainclone out of it;)
but thats me:clown: |
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| JCoffey |
| LOL, Ya, I've thought about that. If i had more know-how, I would. But, since this is going to be for a high end computer system, the layout is fine, and it will support a 20" monitor. (although it will sit on the top of my desk.) What I would like to do, though is rebuild it as much as my knowlage will let me, swapping out caps, wires, ics, binding and RCA posts, etc. Then my plans are to paint the chassis black, and make an aluminum faceplate, and replace the power, and level LEDs with blue ones. :devily: |
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| JCoffey |
| Just thought about somethnig last night. I have quite a bit of Cat5 cable laying around. How good is Cat5 for hookup wire? Or should I just bite the bullet and by Cardas? |
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| Vivek |
| The STK chip amp I built used to hum a lot. I just ran a wire from the power supply ground to the earth socket in the wall outlet. The hum was completely gone. |
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| JCoffey |
| I did think about redoing the power cord, since it's only a 2 prong with no ground. Definately put that on the list as well. |
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