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Old 18th October 2013, 11:28 PM   #1
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Default Which amplifier is more stronger ?

I want to build one amplifier from these .. I have experience .. but i want to know which amplifier have more RMS power on 4 ohm .. Thanks to all
This :
1000W MOSFET LEGEND stage Master MK2
Or this : 700W Leach Amplifier

I think that legend is more powerfull but the number of transistors at leach amplifier makes me be suspicious ..
If i make the legend , and if i use 2x59VAC 1000VA (2x83VDC) for one channel instead the +-95VDC how much power can i get maximum ? maybe 800W at 4 ohm ?

And some word from someone that have made at least one from these awesome amplifiers

Last edited by DANIEL SPASOVSKI; 19th October 2013 at 07:47 AM.
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Old 19th October 2013, 02:52 AM   #2
Rieds is offline Rieds  Indonesia
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from supply 2x59VAC (2x83VDC) if Vswing about 70Volt peak (50Volt rms), it will deliver about 625Wrms to 4 Ohm load.

legend use higher V rail voltage, I think Legend is more stronger.
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Old 19th October 2013, 11:26 AM   #3
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Quote:
Originally Posted by Rieds View Post
I think Legend is more stronger.
Assuming "stronger" refers to supplying higher current for lower impedance loads, consider the Legend amplifier is a Hexfet design, with six pairs of TO247 devices. The Leach has 8 pairs of TO264 devices and so has a good basis for much higher total dissipation capability to drive lower impedance - a major issue for PA.

Using the same rail voltages, the more efficient BJT transistors of the Leach amplifier should be "stronger" by quite a margin, considering that lower power supply rails should be used. Note that 83VDC rails exceed the specified maximum of that version of the Leach amplifier, using 5200/1493 transistors. It would be necessary to use something like MJL21193-6 series parts to get a significantly higher rail voltage.

The real limitation to power, will probably be the protection circuitry which can easily cut the power by 50% or more in normal use, unless it is very carefully designed for the specified supply voltages, transistors and duty. Note that the Legend has no SOA protection at all. Mosfets are forgiving devices but not forgiving enough to protect against shorts or overload at high output levels. Whether BJT or Mosfet, choose a design with well designed, multi-slope SOA protection, if you want a serious PA amplifier that lasts.

Due to our ear sensitivity being somewhat logarithmic, you'll probably not hear much difference in power level, whether it's 400, 600 or 800W. The real load typically drops to much lower impedance than the nominal rating of typical PA speaker arrays so the amp's capability to keep driving such loads without overheating or exceeding the SOA limits is the measure of a PA amplifier's strength, IMHO.
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Old 19th October 2013, 05:11 PM   #4
Rieds is offline Rieds  Indonesia
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actually I said "stronger" refer to Voltage Swing on the Output PA.
IMHO six pair hexfet IRFP260 with +/-95Vdc supply should be able to give higher Voltage swing on the ouput than BJT with supply +/-83Vdc to 4 Ohm load.

I agree with you, if use the same rail votages Leach amplifier should be stronger than legend because Leach use BJT on the final stage.

thanks for the advice and sorry for my poor english,

regards
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Old 19th October 2013, 09:33 PM   #5
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Default The strongest one is the one has stronger power supply

More watts available is what makes the difference...into the supply.

You go decreasing speaker impedance and increasing the output power till the limit of your supply..then no more power than the power the supply can send to your amplifiers.

Power is the result of multiplication of voltage and current.... this way, differences in voltage does not matter...because 1 volt and 100 amperes is 100 watts and 100 volts and 1 ampere is 100 watts too.

So, both are the strongest..... put the stronger supply in A and it gonna be stronger...put the stronger power supply in B and it gonna be stronger.... it is a matter of efficiency (class A, Class B, Class AB, Class G, Class H, Class D) and your supply power.

If one of them is class D.... then, if you compare them with the same power supply, the Class D will deliver more power because of 99 percent efficiency compared to 65 percent (maximum) of class AB amplifiers.... but if the supply you gonna use to the Class AB, to compare with the Class D, if this particular supply to the Class AB is 50 percent stronger..then they gonna be even.

Got it?

regards,

Carlos
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Last edited by destroyer X; 19th October 2013 at 09:37 PM.
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Old 20th October 2013, 05:51 AM   #6
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I would build the Leach as it has short-circuit protection, that would be important to me in a PA situation.

The 12V difference in B voltage is not large enough to be a big deal, the VA rating of the transformer would be more important to me , the difference due to voltage will be on the order of 1dB (assuming similar VA in the transformer).

I might not feel comfortable running 100V caps with 95V either, what if the line voltage drifts up just a bit?
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Old 20th October 2013, 05:54 AM   #7
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"the Class D will deliver more power because of 99 percent efficiency compared to 65 percent (maximum) of class AB amplifiers.... "

Into 4Ω most class D are more like 87% efficient, and a three-rail class G/H can achieve that as well.
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