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Old 10th July 2005, 01:12 AM   #21
djk is offline djk
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A Crown VZ5000 has kind of a wimpy power supply, it only goes up to 2.5KW at 2 ohms (stereo) from 2KW at 4 ohms. If you use a bigger transformer it will do more.

The VZ5000 is a bridged design running on 82.5V with only four pair of MJ21195/96 per half, a total of sixteen outputs per channel.

The MJ21195/96 have 240W SOA at the 80V the amplifier runs at, and only cost USD$2.46 in small quantity.
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Old 12th July 2005, 07:32 AM   #22
bowdown is offline bowdown  Australia
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Hey guys thanx for all the help,i will decide on which way i go and let you know.


Cheers

Bowdown
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Old 20th January 2011, 02:38 AM   #23
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bowdown,
i hope someone share a step drive solution for your quest,
this is according to DJK,
The AB International 1100A uses the Leach topology with a tiered power supply and does 1000W+1000W@2R with only three pair of MJ15024/15025 with rails at +/- 0, 48, and 95VDC.
isn't it great?rather than going on 14 pair? better use tiered a CLASS H LEACH
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Old 20th January 2011, 07:12 AM   #24
AJT is offline AJT  Philippines
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all depends on the application, for home setting and high-fi, i will stay away from class H, for PA duties, that's is a different ball game...

PA amps tends to have higher voltage gains, so the leach amp's x19 can be doubled up to x40.....
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Old 20th January 2011, 10:05 AM   #25
AndrewT is offline AndrewT  Scotland
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see post
The Leach Amp
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Old 21st January 2011, 01:43 AM   #26
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bowdown application need is driving 2000w @ 2ohm,
i was thingking his application is for PA,
two ways he can achieve 2kw 14-16 pairs or tiered
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Old 21st January 2011, 09:50 AM   #27
AndrewT is offline AndrewT  Scotland
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2000W into 2r0 requires 89.4Vpk at the resistor.
The resistor will draw 44.7Apk

Now replace the 2r0 resistor with speaker/s that have an effective impedance of 2ohm.
The reactive load can draw up to 130Apk.
A 3pair output stage using conventional audio BJTs cannot deliver that current even if the ClassG or ClassH or Classx,y,z is implemented.
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Old 21st January 2011, 10:10 AM   #28
AJT is offline AJT  Philippines
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wonder how bowdown did with his subwoofer, it's been more than 5 years ago....
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Old 21st January 2011, 11:50 AM   #29
djk is offline djk
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"A 3pair output stage using conventional audio BJTs "

True, but four pair might handle the current.

The 2x 2500W/2R rated Crown VZ5000 is a class H bridge with only four pair in each quadrant (16 outputs per channel). Originally they used the MJ15024/25, and currently use the MJ21195/96. 15A driver transistors are used. The outputs are mounted without insulators on a copper tunnel for best thermal performance.

You can always use more devices. I probably would, they don't cost that much.
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Old 21st January 2011, 04:37 PM   #30
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Gents:

Don't forget that the W.M. Leach Super amp has a totem pole (cascade) output stage that greatly increases the SOA by dividing the Vce seen by each power transistor by 2 thus allowing each transistor to operate in a much more favorable area of the SOA. These are not normally labeled as output pairs but rather output quads as it takes at least 4 output transistors to complete an audio cycle instead of standard two.

Cheers’

Philip
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