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Old 5th December 2012, 04:29 PM   #2741
AndrewT is online now AndrewT  Scotland
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Originally Posted by Bonsai View Post
.....................That delivers 500W per channel into 4 Ohms. I never had the guts to try it on a 2 ohm load - it also used 10 trannies per channel which is not quite enough...............
A 4ohms rated amplifier should easily drive a 2r0 test load. This 2r0 test load stresses the output stages less than a very reactive 4ohms speaker load.
I would test an 8ohms rated amplifier into a 2r0 test load as a matter of course, to prove that the PSU does not collapse when delivering high current.
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Old 5th December 2012, 09:09 PM   #2742
Bonsai is offline Bonsai  Taiwan
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The tests (8 Ohm and 4 Ohm) were done with resistive loads. The 8 Ohm power was actually 280 W.

I don't agree that a 2 ohm load is easy to drive. This would imply something of the order of 1 kW into the load with 5 out put devices. To close for comfort.

Highly unlikely BTW that the PSU's in there amps will collapse. That a trick commercial amps do ;-)
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Old 5th December 2012, 09:37 PM   #2743
Bensen is offline Bensen  Belgium
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Bonsai,

Andrew is right, concerning the 2r load.
A reactive load consisting of 4 ohm and 45degrees phase angle (real speaker), will bring you in many cases closer to the SOA curve than a pure resistive 2R load. The non conducting side of the OPS will have to deliver a lot of current while having the entire rails voltage between collector and emitter.

PS: your PDF documents about your amplifiers are great!
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Old 6th December 2012, 02:43 AM   #2744
Bonsai is offline Bonsai  Taiwan
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Bensen, I know that . . .

My amplifiers were tested on resistive loads only.

I simply stated I had no desire to push the Ovation 250 to 1kW output :-0
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Old 6th December 2012, 05:25 AM   #2745
a.wayne is offline a.wayne  United States
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You have a 2kva transformer .....load her up , err ahh down ..
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Old 6th December 2012, 05:41 AM   #2746
DQ828 is online now DQ828  Australia
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Aussie Amplifiers 3 Channel build, well six channel actually I built 2 of them.
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Old 6th December 2012, 08:38 AM   #2747
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@ DQ828: Too good.
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Old 6th December 2012, 08:52 AM   #2748
DQ828 is online now DQ828  Australia
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@ DQ828: Too good.
Thanks, broke the bank & the will to live getting them finished
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Old 6th December 2012, 09:05 AM   #2749
Bonsai is offline Bonsai  Taiwan
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Very nice!
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Old 6th December 2012, 09:48 AM   #2750
AndrewT is online now AndrewT  Scotland
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Quote:
Originally Posted by Bonsai View Post
The tests (8 Ohm and 4 Ohm) were done with resistive loads. The 8 Ohm power was actually 280 W.

I don't agree that a 2 ohm load is easy to drive. This would imply something of the order of 1 kW into the load with 5 out put devices. To close for comfort.

Highly unlikely BTW that the PSU's in there amps will collapse. That a trick commercial amps do ;-)
It then depends on whether you have a 4ohms capable amplifier, or an 8ohms capable amplifier. It sounds from your reservation on SOA for the 5pr output stage that you are not claiming 4ohms capability. Have you tried Bensen's SOA spreadsheet, or do you have an alternative SOA modeling method?

If it's 280W into 8ohms, then a minimum test load I would use would be 2r0, but more probably 2r67 to check Vpk when 1/3 rated impedance is connected.
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