damonrpayne Posted June 23, 2003 Share Posted June 23, 2003 Can someone explain to me the basics of a high power (watts) amp versus a high voltage (volts) amp, and the relationship of Ohms to these things in the audio world ? Its been a loooooooooong time since my physics classes so looking up Ohm's law (V=IR and the various derivations) didn't really help me here. This might be too technical but someone here has to have a general answer. (If anyone has a link that might be best?) Quote Link to comment Share on other sites More sharing options...
Jef Posted June 23, 2003 Share Posted June 23, 2003 Hi Damon if you look to the thread 'RF3II owners' of 6/12/03 in this forum you will find some answers on your question. In a nutshell: the relation between current and voltage is defined by the resistance (V=I * R) the relation between power, voltage and current is P = V * I. as you can see, one cannot 'just choose' between high voltage or high current amplifiers as these relationships are fixed by the above formulas. But as an amplifier has to drive loudspeakers which are not just resitive but have capacitive and inductive characteristics the issue becomes much more complex. As a result, to really control / drive a woofer an amplifier must deliver much more current than what you would calculate with the formulas. So amplifiers which high current capabilities will sound better (asuming the other charateristics are comparable). Jef Quote Link to comment Share on other sites More sharing options...
marksdad Posted June 24, 2003 Share Posted June 24, 2003 i too am trying to get solid answers on this question, when i bought my current reciever 1 of the points that brought me to my conclusions is that the denon 5803 is supposed to have a max p-p output of 15 amps, and my b&k 42 p-p, it is something that can be heard especially in ht, but i want a clearer explanation, and i owe an explanation to fish, i keep trying to call b&k, but because of work ant time differences from east to west coast i havent been able to talk with them, i always get home late, sorry fish Quote Link to comment Share on other sites More sharing options...
Fish Posted June 24, 2003 Share Posted June 24, 2003 Thats OK Marksdad,BUT I'm still waiting,gettin weak,please hurry. Quote Link to comment Share on other sites More sharing options...
damonrpayne Posted June 24, 2003 Author Share Posted June 24, 2003 The main reason I was asking was that HK markets themselves as high current amps, for exampe the 325 I have is only rated at 50 wpc but certainly seems more "Powerful" than that. The mental picture I have is that its sort of like torque versus horsepower on a car I'll dig up my physics books and do some research this weekend. To be continued! Quote Link to comment Share on other sites More sharing options...
Jef Posted June 24, 2003 Share Posted June 24, 2003 The reply I wrote actualy covers your question. But I see a more visual explanation is in order. Power output of amplifiers is given in Watts and when used on a resitive load this covers 'all' as it can be interpreted as heat generation. But a loudspeaker is not a resistor at all. Imagine your 50 Watt amplifier accelerating the woofer outwards then have to stop the moving mass and bring it in again. At the moment the woofer has to be stopped and has to move inwards again a large current is needed to generate a forcefull magnetic field that counteracts the inertia. If your 50 Watt amplifier is 'just' capable of generating the currents associated with the specified resistance - lets say 4 ohm - that would be something like 3.5 Amps (on a resistor). That will bring the woofer back ... eventualy ... Compare this with the 35 Amps capacity of a H/K (or other decent amp), you can immediatly see that the H/K has 10 times more current (read magnetic force) to stop and restart the woofer. So the more current an amplifier can genenerate the more 'control' it has on the moving mass of the woofer cones = a tighter and better controlled bass. one has also to understand that sound is logarithmic in nature meaning that to perceive a doubling in sound level a 50 Watt amplifier must go to 500 watts (10dB increase). All the intermediate values of amplifiers like 90, 110 or even 150 Watts don't even come close to this. The only reason they sound 'louder' is that amplifiers with higher power ratings are given larger transformators and are genereraly able to provide more current. Hope this helps ... Jef Quote Link to comment Share on other sites More sharing options...
dougdrake Posted June 24, 2003 Share Posted June 24, 2003 Jef - That's very helpful. Thanks. Re the doubling of volume with 10x the power...I think we also have to remember that you really wouldn't be consuming 50 watts, in most cases, as your ears would long since have stopped working. Probably more like 2-3 or maybe even 10 watts, so to double volume would take, say, about 100 watts, still within striking distance of many receivers/amps out there. I think... DD Quote Link to comment Share on other sites More sharing options...
damonrpayne Posted June 25, 2003 Author Share Posted June 25, 2003 Yes, Jef you saved me a lot of painful research! Quote Link to comment Share on other sites More sharing options...
Jef Posted June 25, 2003 Share Posted June 25, 2003 Hi Dougdrake, well you are touching the subject of peak power versus average power. On average most amps are running around 0.001 and 0.01 Watt(-30dBW and -20dBW) when playing out loud as (and) refering back to the 50 Watt (+ 17dBW) amplifier you have 37 dB headroom for the peaks in the music - the 100 Watt amp would give you 3 dB more. 3 dB is a noticable difference at low soundlevels but not at high soundlevels as the ear becomes insensitive. Most music is situated below 1 Watt in a houseroom with high efficient speakers :-) Jef Quote Link to comment Share on other sites More sharing options...
lastin1 Posted June 26, 2003 Share Posted June 26, 2003 I have no idea what Jef is talking about. What HK means by high current amp is that the amp is capable of passing high current (Amperes). The power supply is capable of feeding large amounts of current through beefier output power transistors. The difference between a "high current" amp and a regular amp is that a loudspeaker's impedance (electrical resistance) is not a constant 8 ohms so when the speaker dips to say 2 ohms at some frequency, the power supply's rail voltage won't drop as much as a cheap amp and the power transistor is capable of passing that current. Quote Link to comment Share on other sites More sharing options...
Jef Posted June 26, 2003 Share Posted June 26, 2003 Hi Lastin, actualy there is not so much difference between our explanations. Mine is electro-mechanical based, yours comes from the pure electrical model. For visualisation I prefer the electro-mechanical one as it immediatly goes to the heart of the matter - i.e. why do high current amps sound better. Maybe I can use your numbers to show the difference. Again using the 50 watt amplifier and your dip of 2 Ohm. At 2 Ohm (resistive) the amp has to produce 5 Amperes when delivering 50 Watt. What happens with the other 30 Amperes that the H/K can deliver ? When would he ever do that ? Jef Quote Link to comment Share on other sites More sharing options...
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