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qoqzgood

Me being an idiot thinking my amp defies law of thermodynamics lol

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My amp is Soundstream Tarantula TR800/5 it sounds really good for class A/B and the sub output rated at 400W @2 ohms

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This what shakes my head

I have a current measuring device with a shunt. At full tilt it draws ±18 Amps @±11.7V, that is around ±250 watts w/ headunit and et cetera. I thought "maybe this amp is shot considering it's old" right?

Well, i grabbed my multimeter and measured ACV at full tilt and the results is 30ACV @2Ohms. I froze for a second because i freaked out "this amp delivers 450 - 500 Watts RMS yet my current measuring device say it's drawing ±19 Amps??!! WHAT??!"

Can someone shed a light with this? I'm totally confused right now. 😂😂😂

 

Edited by qoqzgood

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It's not making rated power if the voltage is dropping that bad to below 12v. You need a clamp meter to accurately measure its true output. 18a at 11.7v is 210w, it can't produce more than what it is drawing and no amp is 100% efficient.

Impedance is reactive, so the sub isn't at a constant 2 ohms, the impedance changes with every frequency so your measuing technique is not correct and you are lacking the correct equipment to properly measure what you are trying to do.

Whatever electrical system you are using to power that amp is too weak for the amp and you are getting voltage drop which is not good and can blow up the amp.


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2 hours ago, THATpurpleKUSH said:

It's not making rated power if the voltage is dropping that bad to below 12v. You need a clamp meter to accurately measure its true output. 18a at 11.7v is 210w, it can't produce more than what it is drawing and no amp is 100% efficient.

Impedance is reactive, so the sub isn't at a constant 2 ohms, the impedance changes with every frequency so your measuing technique is not correct and you are lacking the correct equipment to properly measure what you are trying to do.

Whatever electrical system you are using to power that amp is too weak for the amp and you are getting voltage drop which is not good and can blow up the amp.

Ah yes, i totally forgot that impedance is reactive.

Speaking of voltage, is it ok to set it above 13V? I don't know much about amp sweet spot voltage though. Since i'm using a variable power supply, any voltage is adjustable.

Thanks for the response 😉

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2 hours ago, THATpurpleKUSH said:

It's not making rated power if the voltage is dropping that bad to below 12v. You need a clamp meter to accurately measure its true output. 

Whatever electrical system you are using to power that amp is too weak for the amp and you are getting voltage drop which is not good and can blow up the amp.

Alright, i set my PSU @14.3V at idle, It dips @±12.5 - 13V under load, is it enough?

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This amp is not in a car is it?.. small bench or other power supply?

Just stand-alone power supply or possibly anything else?


JVC KD-X350BTS, RE Sx-18d4 9ft3 36.86hz, Synergy 3K@ 2 ohm, RF 500s, Polk DB comps, Cache Preamp/EQ

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3 minutes ago, shredder2 said:

This amp is not in a car is it?.. small bench or other power supply?

Just stand-alone power supply or possibly anything else?

Yeah, it's a standalone power supply rated at 40 amps

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43 minutes ago, qoqzgood said:

Alright, i set my PSU @14.3V at idle, It dips @±12.5 - 13V under load, is it enough?

I would set it a little higher at about 14.8v. That power supply is barely strong enough to power your amp.


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1 hour ago, qoqzgood said:

Yeah, it's a standalone power supply rated at 40 amps

I'd add something to the supply chain... even a small 12V agm like a motorcycle one... idk


JVC KD-X350BTS, RE Sx-18d4 9ft3 36.86hz, Synergy 3K@ 2 ohm, RF 500s, Polk DB comps, Cache Preamp/EQ

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Current draw on full range music averages out to less current than the peaks you read on your multimeter/shunt. Especially for midrange and tweeter frequencies. 

A 40a power supply should be fine for that amp although as it was said you may use all of its output depending on what each channels final impedance is and type of music 

Why are you using +- for your voltage and amperage readings?

Edited by wew lad

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10 hours ago, THATpurpleKUSH said:

I would set it a little higher at about 14.8v. That power supply is barely strong enough to power your amp.

Ok, i parallel'd my power supply at 14.8V now and now drops to only 13.8V and draws ±18A. It did reach 22A but it's a bit distorted, so i pulled back the gain.

9 hours ago, shredder2 said:

I'd add something to the supply chain... even a small 12V agm like a motorcycle one... idk

I actually wanted to install 1.2F caps, but the cap died, maybe i'll buy a new battery later.

4 hours ago, wew lad said:

Current draw on full range music averages out to less current than the peaks you read on your multimeter/shunt. Especially for midrange and tweeter frequencies. 

A 40a power supply should be fine for that amp although as it was said you may use all of its output depending on what each channels final impedance is and type of music 

Why are you using +- for your voltage and amperage readings?

I'm using ± because the refresh rate of my current and voltage meter is too fast, so i average it with my eyeballs.

Edited by qoqzgood
Wrong data

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14 hours ago, THATpurpleKUSH said:

Voltage drop is not good and can blow up the amp.

I don't understand why low voltage can blow up the amp? To my understanding is too low voltage would just make the amp doesn't work right?

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11 hours ago, qoqzgood said:

I don't understand why low voltage can blow up the amp? To my understanding is too low voltage would just make the amp doesn't work right?

Because the amp will still trying to draw the same current. They have a set operating range generally 11v-15v in which output fluctuates but As voltage drops resistance rises and as resistance rises so does heat.

 

As far as over voltage well you start pushing more current then individual devices can handle. As current flows it carries heat. At set ranges the heat can be dissipated and the device is fine but once you exceed the rate of dissipation the heat starts to cook the device


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On 2/10/2019 at 12:39 AM, qoqzgood said:

I don't understand why low voltage can blow up the amp? To my understanding is too low voltage would just make the amp doesn't work right?

He exaggerated it a little bit to make a point. It's kind of stereotypical to say that because its often thought that people who are new need to have a few key points driven home. I.e. the gain knob isn't a volume knob. 

By all means with a stable 11Dcv supply that won't even drop a thousandth of a volt run the amp in those conditions but we try limit the DC input fluctuation as much as possible for more output and it is better for components to have a stable power source.

 


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