How many watts can the STK4221II IC output at 4 ohms?

techgeek72 · 21st September 2013, 12:21 PM

The STK4221II IC can output 80 watts at 8 ohms.

How many watts can the STK4221II output at 4 ohms?

KatieandDad · 21st September 2013, 01:45 PM

The datasheet only specifies the output at 8 Ohms = 80W.

I would summize that it can't go as low as 4 Ohms.

FoMoCo · 21st September 2013, 03:40 PM

Most likely it will run out of current, so a good estimation is one half rated power into half the impedance. You'd also want to use the lowest supply voltage possible as the extra voltage only produces extra heat.

While it's not true that it can't handle a 4 ohm load, it will be severely limited in power output. It may even die if not fully protected and you do something dumb with it. You'd be better off with a better match to your load.

KatieandDad · 21st September 2013, 04:30 PM

Can you substantiate how it will handle a 4 Ohm load ?

AudioSan · 21st September 2013, 04:36 PM

as long as one don't know the current limit, this will all be guessing.

KatieandDad · 21st September 2013, 04:50 PM

Unfortunately the datasheets are very poor. The STK4122 II was specified at 80W / 8 Ohm. There might be other information available with user instructions from units that used these chip amps.

FoMoCo · 21st September 2013, 05:07 PM

Quote:

Originally Posted by AudioSan

as long as one don't know the current limit, this will all be guessing.

Very true. But a safe assumption is that maximum output into 8 ohms is also close to current limit. It's probably a bit more, but short of measuring it, we don't know.

Quote:

Originally Posted by KatieandDad

Can you substantiate how it will handle a 4 Ohm load ?

Yes. Just take a course in electronics.

KatieandDad · 05:49 PM

I've got a degree in electronics.

As AudioSan stated, you can only suppose.

If the output devices are running at maximum current iaw with the datasheet then the maximum power will be halved.

You could always add your fuses to see what blows first.

FoMoCo · 21st September 2013, 05:54 PM

Quote:

Originally Posted by KatieandDad

If the output devices are running at maximum current iaw with the datasheet then the maximum power will be halved.

I'm pretty sure I already said that before you made your remark about me needing to substantiate my claim.

21st September 2013, 12:21 PM	#1
techgeek72 diyAudio Member Join Date: Sep 2013	How many watts can the STK4221II IC output at 4 ohms? The STK4221II IC can output 80 watts at 8 ohms. How many watts can the STK4221II output at 4 ohms?

21st September 2013, 03:40 PM	#3
FoMoCo diyAudio Member Join Date: Dec 2012	Most likely it will run out of current, so a good estimation is one half rated power into half the impedance. You'd also want to use the lowest supply voltage possible as the extra voltage only produces extra heat. While it's not true that it can't handle a 4 ohm load, it will be severely limited in power output. It may even die if not fully protected and you do something dumb with it. You'd be better off with a better match to your load. __________________ Account Deletion Requested: 1/26/2014

21st September 2013, 05:45 PM	#8
KatieandDad diyAudio Member Join Date: Nov 2011 Location: UK	I've got a degree in electronics. As AudioSan stated, you can only suppose. If the output devices are running at maximum current iaw with the datasheet then the maximum power will be halved. You could always add your fuses to see what blows first. Last edited by KatieandDad; 21st September 2013 at 05:49 PM.

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21st September 2013, 01:45 PM	#2
KatieandDad diyAudio Member Join Date: Nov 2011 Location: UK	The datasheet only specifies the output at 8 Ohms = 80W. I would summize that it can't go as low as 4 Ohms.

21st September 2013, 04:30 PM	#4
KatieandDad diyAudio Member Join Date: Nov 2011 Location: UK	Can you substantiate how it will handle a 4 Ohm load ?

21st September 2013, 04:36 PM	#5
AudioSan diyAudio Member Join Date: Feb 2009	as long as one don't know the current limit, this will all be guessing.

21st September 2013, 04:50 PM	#6
KatieandDad diyAudio Member Join Date: Nov 2011 Location: UK	Unfortunately the datasheets are very poor. The STK4122 II was specified at 80W / 8 Ohm. There might be other information available with user instructions from units that used these chip amps.

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