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Been in a conversation on a Magnepan group talking about amplifiers. We got into a conversation about current and the need for it on the large planar speakers.
I run an Ashly FTX 2001. 500 watts at 4 ohs, 675 at 2 ohms. The gentleman in the discussion was trying to convince me that the Citation 16 was a higher current amp, rated at 175 wpc. I know that the advertised ratings are not the 100% means to go by an amplifier's abilities. Both of these amps are class a/b, the ashly uses a Mosfet output stage and forced cooling - its a pro amp.
What are your thoughts on this, is my Ashly ok or do really need to consider something else in high current to drive these speakers??
The whole conversation started around a lack of bass in my MGIIIA speakers.
It can be expressed as the resistive impedance load of the speaker divided by the output impedance of the amplifier.
"The hardest thing of all is to find a black cat in a dark room, especially if there is no cat" - Confucius
Another point of reference is the energy capacity of the power supply. I located the schematics of each.
The Ashly runs 30,000 uF on 80V rails for 96 joules
The Cit16 runs 40,000 uF on 60V rails for 72 joules
Indeed both old and current production series 3 Magnepans are a bit shy on the first octave given their panel area.
Current can be described as a function of power and resistance in the following equation:
I 2 = P / R
This means that current squared is equal to power divided by resistance. Therefore, current would be equal to the square root of (power divided by resistance).
For the Ashly:
I 2 = 500 / 4 = 125
I = the square root of 125 = 11.18-Amperes
I 2 = 675 / 2 = 337.5 or 18.37-Amperes
For the Citation:
I 2 = 175 / 8 = 21.875
I = the square root of 21.875 = 4.677-Amperes
Alternately, if the power is based on 4-ohms, current would be 6.614-Amperes
It looks to me like your Ashly FTX 2001 produces more current than the Citation.
On the other hand, if you can borrow a Citation and connect it to your speakers, you can determine which amplifier produces better bass. That's probably the best way to evaluate the difference between the two amplifiers.
I haven't bothered to compare specs but what I gather he is referring to on the Citation 16 is it's ability to deliver during peaks (low impedance or heavy bass). It's a dual mono design with a very stiff power supply. Thus his belief that it is suited to the Magnepan speakers. Harman Kardon became known for there ability to deliver well beyond the stated power capabilities with the introduction of Stu Hedgeman's Citation II. When they went solid state they introduced the dual mono power supply.
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