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Reciver problem

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January 7, 2003 6:13:43 PM

I wnat to buy a 5.1 reciver and i can`t decide on what to buy: the Technics SA-DX950 or the Sony STR-DE685. Please help.
I have the Sony SS-MF600 200W 8 ohm. I understand that if i chose the Technics reciver witch gives only 6 ohm i will lose power. How much power will that be ? TnX

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Anonymous
January 7, 2003 7:01:15 PM

In all the cases that I am aware of, amps capable of driving multiple impedances always are able to put the most power into the smallest load that they are rated to drive.

I haven't really given it enough thought to convince myself of why this might be true, it's just an observation.

Typically the spec sheets will have these numbers quoted within. If you post links to spec sheets we could check them out(pardon me I'm feeling a little time crunched this afternoon). But yeah in general you would probably lose a little off of the total power available if you went with the 8 ohmers over some 6 ohmers.
January 7, 2003 7:06:56 PM

I have had two technics receivers, one i sold to a friend (still works like 10yrs old now) and one i still use. Very good never been in for service. By the way lower ohms usually give more power. Home stereos are normally 8 ohm, car stereo is normally 4 ohm. car amps put out more power at lower ohms but also more heat. but dont worry about that with the home receiver.
not sure on their specs but make sure they have digital inputs.
Were u planning on using it for your computer?
<P ID="edit"><FONT SIZE=-1><EM>Edited by sturm on 01/07/03 04:09 PM.</EM></FONT></P>
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January 7, 2003 7:54:03 PM

I'm pretty sure it's all about electrical current.

Often you will see ratings on amplifiers similar to, 100 watts - 8 ohm load, 150 watts - 6 ohm load, 200 watts - 4 ohm load. Using Ohm's Law then Power = Current x Resistance and in the first example to yield 150 watts of power the amplifier would need to deliver 12.5 amps (100 watts / 8 ohms) of current. 150 watts at 6 ohms requires 25 amps. 200 watts at 4 ohms requires a whopping 50 amps of sustainable power. Dynamic power demands require even more current, lots more current. This is why many home amplifiers can't cope with 4-ohm loads.

<b>99% is great, unless you are talking about system stability</b>
Anonymous
January 7, 2003 11:36:12 PM

I hate to say this but those data sheets leave alot of info out. I never have understood why manus don't just post the full data sheets for home audio equip. To be honest I wouldn't buy anything without viewing the actual data sheets as there is obviously much more to the story.

The fact that the Sony gives the 100W rating for 8 ohms leads me to belive that the amp is a bit beefier than the Techniques which rates theirs 100W into 6 ohms. Based on that, and all else equal I would be going for the Sony.
Anonymous
January 7, 2003 11:41:58 PM

that makes alot of sense especially considering the current amplifier configuration most audio equipment use these days as a final output stage. A FET which is biased to full on is limited by the current which flows through it, and thus the power dissipated by it.
January 8, 2003 12:54:52 AM

Quote:
that makes alot of sense especially considering the current amplifier configuration most audio equipment use these days as a final output stage. A FET which is biased to full on is limited by the current which flows through it, and thus the power dissipated by it.

Sorry, dropped out of circuits class long ago. I know solid state amps use transistors and the designs require bias currents. That's the extent of my knowledge. I didn't know the technical reasons for limited current output. I assumed it was limited by design because of the nasty heat issues if you don't limit current.

I hope never to see the effects of uncontrolled current from an amplifier. LOL!


<b>99% is great, unless you are talking about system stability</b>
!