Nobsound

durkla18

Member
2007-10-30 4:57 pm
Hi everyone! I purchased a Nobsound mini amp and can't for the life of me figure out what is wrong with it. Nobsound Mini 200W Digital Power Amplifier HiFi Class D Home Stereo Audio Amp 328076922737 | eBay I also bought a douk 24V 6A power supply to go with it. Even with the volume completely down, it makes this high-pitched whistling sound. It doesn't matter what level it is at, as you can still hear it. I took the top off and was wondering what I could do to it to make it quiet--touching pretty much every component. I finally pressed down on the heat sink and it made the pitch change. It didn't disappear, the sound changed a bit. The reviews aren't that great on amazon either: Amazon.com: Nobsound 2.0 Channel Power Amplifier ; Hi-Fi Audio Amp for Home Speakers ; 200W (100W x 2): Electronics Wish I read those first before buying!

Any thoughts on what I could do to fix this problem before I try to get my money back? LOL! Thank you in advance for your help and suggestions.
 
Hi everyone! I purchased a Nobsound mini amp and can't for the life of me figure out what is wrong with it.

A lot of these mini-amps ship out with 19 volt supplies... and that's for a reason. Usually it signals they've used 25volt capacitors on the bulk supply rails (see the thumbnail). Plugging in a 24 volt supply without checking this first can lead to damaging the caps, even exploding them, if any are even slightly off tolerance.

In general, Nobsound, Breeze Audio and Douk audio are pretty marginal designs, sometimes using recovered or counterfeit parts, which explains how they're cheaper than "equivalent" products.

Given the problem you're having a refund makes perfect sense. Fixing it is going to cost you more than a new amp.

You could try one of these ... Senucn Audio ... amplifiers which are also bassed on the tpa3116/ne5532 combination but built correctly. They come with a 24 volt supply and the bulk cap is 50 volts. My review is ... here ... and, yes, I use one with my home entertainment system.
 

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Hi


i guess that this is the thread - this amps looks nearly the same.
New Breeeze Audio TPA3116 2.0 100W dual chip
i am not an expert in class D but i try something- i choose this amp because of the "idea" of dual chip and every chip is for one channel.;)

i use 24V PSu and the caps are lickly 35V - 24V are too closed to 2%v of your caps -change the psu to 19V.
if you are good in soldering you can check and re-solder all solder points.

the gain is also too high - generally the gain is set 30db or higher. try to set this down!


strange at this amp is that the amp is always in idle mode if you connect it to the psu.:rolleyes: and mine (2 amps) are strange because they not always switch on if i use the switch on the left side. sometimes one channel is off or the amp is still complete quite -strange:mad: when the amp is playing its not bad- sound good, but i am still not very satisfied compared to my others - so if i am hungry for modding i go ahead..
chris
 
The dual TPA116D2's should have their oscillators slaved together, but clearly don't, leading to a beat frequency being audible. Probably is fixable if you have the expertese, but not trivial).



[ 25V caps should work at 24V. Electrolytic caps have working voltage ratings, not absolute maximum. However cheap unbranded caps may be crap at any voltage... ]
 
The dual TPA116D2's should have their oscillators slaved together, but clearly don't, leading to a beat frequency being audible. Probably is fixable if you have the expertese, but not trivial).



[ 25V caps should work at 24V. Electrolytic caps have working voltage ratings, not absolute maximum. However cheap unbranded caps may be crap at any voltage... ]


Hello Mark
Thank you for your hint.

do you refer to this? i ask if i checked the layout of this amp. nobody gave feedback - post 22
https://www.diyaudio.com/forums/cla...tpa3116-2-0-100w-dual-chip-3.html#post5791089
chris
 
[ 25V caps should work at 24V. Electrolytic caps have working voltage ratings, not absolute maximum. However cheap unbranded caps may be crap at any voltage... ]

Yes they should. But when you're spending $30 for a whole amplifier you have to know you're not getting top line parts.

One of my ways of making a little extra cash is to bring in, improve and sell these little mini-amps to friends and friends of friends. I've had several of them come in with 25volt caps that explode only a few minutes into using them. ... like in this video

It's likely they are counterfeit or recovered parts, so I make a habit of replacing them. And you'd probably be quite surprised how many of these things have the provision for it right on the boards...

They really sound quite good when they work right.
 

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I believe there could be a further reason for the 19V supply and that is cooling inside a closed compact cabinet. It should be a cooling bridge connected to the metallic cabinet directly rather than a heatsink passing the heat onto still-standing air and then from the air to the metallic cabinet.

Actually the 19 to 24 volt switch (either way) doesn't seem to make much difference in the chip's temperatures, maybe 5c. I use these things personally and I sell them to others. Never had one overheat yet.
 

durkla18

Member
2007-10-30 4:57 pm
Thank you all in the much needed schooling on what brands to buy and which ones to avoid. After troubleshooting the amp, I found out that it was actually a faulty power brick. Douk Audio 150W 24V/6A AC/DC Power Supply Adapter Transformer US/EU/UK/AU Plug | eBay

I suppose I should've been more suspicious when it claimed it is a 'Real' [email protected] 6A power supply. The electrical outlet plug is not grounded, and it is very flimsy. One review left said that it was noisy.
I tested the amp with a car battery which was out the car and played music through it. At the minimal level, there wasn't any interference or whistling.

I would like to also replace the capacitors based on everyone's consensus. There are ten 470uf 35 V capacitors. 5 have both leads connected to the positive portion of the circuit board while the other five have the negative lead going to the negative and the other going to the positive etching. I don't know what the purpose is of that is or how to figure out the total capacitance to add in one large capacitor. At first, I thought it would be 4700 uf, but since both leads from the 5 of the capacitors are connected to the positive etch, I'm not sure.

And Douglas, if after all the capacitor swapping and it all blows up in my face, I'll gladly buy a Senucn amp if you approve! They look really well made and cost the same for what I paid for the Nobsound amp and power supply.
 

durkla18

Member
2007-10-30 4:57 pm
I added some pictures of the power supply and amp board, if anyone is interested.
 

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One of my ways of making a little extra cash is to bring in, improve and sell these little mini-amps to friends and friends of friends. I've had several of them come in with 25volt caps that explode only a few minutes into using them. ... like in this video

Fully acknowledging your (somewhat disappointing) experience with the Nobsound TPA3116 amplifier, I will point to a "mistake" made by the guy in the video - he loads only one channel and leaves the other unloaded. That, we have been informed early in the TPA3116 thread may be fatal. The undamped output filter may send energy reverse back to the supply rail and the voltage and current ripple may be (much) higher than assumed.
The capacitors should clearly be rated 35V or better. If the capacitors had blown with both channels loaded remains unknown.
 
Fully acknowledging your (somewhat disappointing) experience with the Nobsound TPA3116 amplifier, I will point to a "mistake" made by the guy in the video - he loads only one channel and leaves the other unloaded. That, we have been informed early in the TPA3116 thread may be fatal. The undamped output filter may send energy reverse back to the supply rail and the voltage and current ripple may be (much) higher than assumed.
The capacitors should clearly be rated 35V or better. If the capacitors had blown with both channels loaded remains unknown.

It's not my experience. I looked at quite a range of these amps with a number of different chips and configurations and figured out early on that Douk audio and it's brands aren't the way to go. Just looking at their board photos told me they were not likely to be well designed.

With a proper low ESR cap (or caps) in the bulk supply, inductor feedback should be minimized although it still makes it into the chip itself.

Of late I've narrowed this down to a short list of models that I buy.

For the bare bones I generally go with the senucn amp. It is well designed and nicely assembled for the price... A502 Review

If you want tone controls I mostly order the Linkfor tpa3116d2 Review

If you want bluetooth I order the Proster version (No Review, yet)

I find these to be of adequate quality, after upgrading the caps.

Speaker wise I usually match them up with entry level Fluance or Elac to make "soundbar killer" systems that everyone seems to like well enough.
 

ubergeeknz

Member
2018-08-31 12:32 pm
is it right that really the second row of the caps are shorted??!!
pic 1 and pic 3...??
chris
Hilarious! So they can put the really, really defective ones in that row and they won't blow up [emoji28]

Edit: on closer inspection, the pads on one side are isolated from the large area (barely). Probably they connect with the rail on the other side of the board.
 
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......
Of late I've narrowed this down to a short list of models that I buy.
For the bare bones I generally go with the senucn amp. It is well designed and nicely assembled for the price... A502 Review
If you want tone controls I mostly order the Linkfor tpa3116d2 Review
If you want bluetooth I order the Proster version (No Review, yet)
I find these to be of adequate quality, after upgrading the caps.

Speaker wise I usually match them up with entry level Fluance or Elac to make "soundbar killer" systems that everyone seems to like well enough.


Many thanks for this overview that is useful for our less experienced members.