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Dinas Humming at Low Volume

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cotinus0
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@tvor-ceasar One very last question : Would these be ok ? The store is next door.

https://www.kge.ca/en/product/diodes-bridge-rectifier/15890-diode-schottky-45v-10a-r6.html


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TVOR-Ceasar
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They'll work.

-Charlie
https://www.youtube.com/user/TheTrueVoiceOfReason


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cotinus0
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Thanks.


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Andrewluz
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I have been having the same issues as the original poster. I just finished building a pair of DINAS. They both buzz very loud with and without the RCA cables plugged in. Loud enough that my wife who doesn't care about audio at all asked me from 15 feet away if that was the the speakers making that noise. I have even tried different RCA cables but it doesn't make a difference. I have also tried different power supplies and the speakers buzz the same with either supply. I have even plugged the power supplies into a Tripp-lite Isolator but that doesn't change anything. I am going to some outlet adapters with no ground. 

 

It doesn't look like the video is uploading correctly. 


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TVOR-Ceasar
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@andrewluz

The more I hear about the problems people are having, I'm wondering if there's more going on than what "we" (et.al.) were talking about earlier in this thread. 

I'm sitting here listening and, yep, that's 120 Hz tone, which you would expect out of a standard linear supply, ie, a transformer -> rectification (usually a bridge) -> 1st smoothing -> regulation -> second smoothing with bypass. (120 Hz for 60 Hz lines and 100 Hz for 50 Hz lines) But these are switching supplies that run at many times the wall line frequency so any rectification hum should be inaudible.

At this point, I'm wondering if there's been a batch of amps where some quality control issue has left them open for such interference. I'm really at a loss right now as to what to even speculate. About the only thing I can go on is the tone and the fact you have it with and without the patch cord plugged in and you've switched out power supplies. That leads me back to the amp being in question. 

Those amps don't happen to have a Bass Boost button or control, do they? If they do, turn it off or down, as the case may be, and report back.

And yes, a 3 prong to 2 prong adapter is a good idea to test out.

-Charlie
https://www.youtube.com/user/TheTrueVoiceOfReason


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Andrewluz
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@tvor-ceasar 

 

There is no bass boost button. You can adjust the subwoofer volume with a knob but it doesn’t make a difference with the buzz. 

I tried using an adapter without a ground but it doesn’t make a difference. I also tried plugging the speakers into a power conditioner and a Variac with and without the 2 prong adapter. No difference. 

After all this testing I am positive that it is the amp itself making the buzz and it is not caused by any outside factors. 


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TVOR-Ceasar
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@andrewluz okay, you've confirmed my suspicion.

I was reading some reviews of other class D amps and some noted that if you touch or ground the heatsink, the noise stops. It's worth a try.

-Charlie
https://www.youtube.com/user/TheTrueVoiceOfReason


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Andrewluz
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@tvor-ceasar

 

I appreciate the advice  I will try this sometime this weekend and report back  

 

 


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Andrewluz
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I removed one of the amps but was not able to find a heat sink on it…

 

Also, the actual power supply that came from Parts Express says it is 4.8 amp 19v.  But the description on the website says it should be a 4 amp 15v power supply. It the supplied power supply too powerful? 


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TVOR-Ceasar
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@andrewluz The description on PE's website says a range of 15-22 Volts. IF you add up the wattages listed (2x30 + 60), you get an output of 120 watts. If you divide that by the power supply voltage (19), you get ~6.32 amps. So, in all actuality, the power supply is actually underpowered. Especially when you take into account the amp is about 80% efficient at full power and there's also overhead to run the rest of the amp's circuitry. But you most likely wouldn't notice that fact in use. It's just a point to consider.

Also, when looking at the photos on PE, you'll see that the chips labeled TPA3118 in the middle of the board don't have heastsinka - these are the actual amp chips. If you can hook the board up while it is out like that and very carefully touch the top of one of the chips, maybe even pressing down just a bit, to see if that helps, you might be able to discover if they are the culprit. Just keep your other (non-touching) hand away from any circuitry or anything grounded - maybe put it in your pocket like they recommend  for tube amps, so you don't short anything or get a shock.

-Charlie
https://www.youtube.com/user/TheTrueVoiceOfReason


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cotinus0
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@tvor-ceasar Would a 22V, 6,5 A be overpowered and not safe to use ? Thanks


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TVOR-Ceasar
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The thing that is important is that you don't exceed the maximum voltage. The device will draw the current it needs, no more. That's why you can plug a 60 watt light bulb into a 2500 watt circuit and not have problems. But if you try to put a 12 volt lamp on a 120 volt circuit it'll blow.

To directly answer your question, it is within the maximum voltage range and the total power is 22x6.5=143 watts, which covers the max output of the amp plus some overhead. So yes, it will work, just don't go any higher in voltage.

-Charlie
https://www.youtube.com/user/TheTrueVoiceOfReason


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cotinus0
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@tvor-ceasar Thanks again for helping a newbie.


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