DonMaico said:
Which is why its important to use efficient speakers with maximum sensitivity of about 90 db right?My kefs are supposed to be 90 db but sound cr#p with leak whereas the Hb!s sound fine to me????( just realised i am talking about something completey different - efficiency not Loads). I wonder how a pair of Rogers LS35 a would sound like? 15 ohms but only about 83 dbs- flat I guess!
Any way I notice transistor amp specs rarely mention amperage or for that matter wattage into 4 and 2 ohms - just 8 ohms. What are they hiding? They also tend be fairly lightweight suggesting small transformers which I guess would make them cheaper.the chap who said " its not as simple as that" was a dealer and I am guessing he thought I was the kind of guy who couldnt afford an amp with large transformer delivering plenty of amperage so he just shrugged my question off.
With lower output amps,valve or transistor,high sensitivity speakers are essential,and a lot of the horn designs run at over 96dB/W,whereas things like my N805s are allegedly 88dB/W but very current hungry designs.
As far as a valve amp is concerned,with proper output transformer matching,you will get the same output into 8 or 15 ohms if the taps are set correctly,and the LS3/5s would sound lovely,but you wont get high levels out of them...you wouldnt anyway,as they werent designed for that.
Transistor amps and output into lower loads.....always a contentious area,but you have to consider the cost of incorporating a power supply capable of delivering increasing output into decreasing loads.
It isn't an issue with most valve amps as it just doesnt happen,but in the early 80s a lot of manufacturers went a bit mad with claims of power output etc,and along came a wonderful old speaker called the Apogee Scintilla,which sounded superb(a ribbon speaker with an impedance of 1 ohm(!)),and about the only thing that would drive it was the Krell KSA100,with a 2kW transformer,and around about 150,000uF capacitance per channel.
The thing weighed a good 70kgs(I know as I had one)and thats the reason that most lesser designs are a bit cagey about decreasing load impedance.
It's not quite as simple as a bigger transformer,but includes either very large supply capacitors,or switch-mode supplies a la Linn or Chord,and none of those things are cheap to engineer properly,to be fair.
If you look at the transformers and power supplies in a lot of AV amps,they are just about able to sustain rated output into 8 ohms,never mind below that,although there are many decent exceptions.