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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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In Reply to: What in the design makes an amp drives 4 ohm speaker happily? posted by hc122 on January 15, 2004 at 20:34:16:
As stated in another response, it is mainly basically the current available from the power supply. This is mainly a question of the transformers VA ratinging.However, in addition to that it depends on also on the output transistors. All transistors have an SOA "Safe Operating Area" which is an envelope of voltage and current combinations. If for any reason, the transistor is subjected to conditions beyond this envelope, it fails - fast. The usual way to avoid this is to add output transistors
Most amps you buy have some kind of circuitry to prevent this. That will save the transistor but it usually does so by cutting the drive current, which not so great for getting sound out of your speakers!
Even if all the above are addressed satisfactority, driving a 4-ohm load draws more current which produces more heat. To much heat and the transistors die unless there is a thermal protection circuit. Such a circuit usually just opens a relay killing any output untill it is reset. This also does little for the listening experience.
Finally there is the myth that halving the load gets you twice the watts. Although, specs can be spun to give that impression, in fact you get an increase in watts more like 70%. I.e., if you have 36W @ 8 ohms, you will get more or less 60W at 4 ohms.
So will, you unit drive a 4 ohm speaker? Maybe. Regretably I doubt that unless it is specifically stated, there is nothing on the spec sheet to tell you. However, manufacturers find is a poor markrting strategy to have their unit fail in large numbers, so at the least I imagine there is protective circuitry in your unit as described above. You can give it a try while taking a couple of precautions. First don't stack it with anything or shove it into a cabinet - let it get as much ventilation as you can. Next keep the volume moderate for a while (s couple of week)and increase volum levels gradually over time. I say this because sometimes (I speak from expensive experience) the protection circuits are not quick enough to prevent very slight cummulative damage - let them activate repeatedly and eventually you will need repairs.
good luck.
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Follow Ups
- Re: What in the design makes an amp drives 4 ohm speaker happily? - sam9 10:56:00 01/16/04 (0)
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