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Old 18th February 2010, 10:06 AM   #1
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Default A ...power amplifier

i am going to play with this amplifier in the next days i would like to have opinions about the schematic

also i have allready made pcb and will be very ineteresting to have suggestions on how to stress the amplifier as much is possible for testing

allready i will perform all the known tests with a dummy load and so on and on but i would like to have more sugestions regarding tests with more or much more stress

( i have a big solenoid coil and i thought that since this a very reactive load like a speaker may i put this on the test also )

thank you very much
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Last edited by east electronics; 18th February 2010 at 10:12 AM.
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Old 18th February 2010, 08:18 PM   #2
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some updates ( eventhough it seems that there is not much interest )
some more will also come the next few days ....

Just come in to my shop 1943 5200 labeled as 1K26AA A1943 and 1K48AB C5200 from FAIRCHILD ... by the looks it seems that is an excellent product will see the next few coming days

ok ...working with the fairchild transitors seem that base resistors are not needed amplifier operates way much better and cooler with out them ....

Emmiter resistors i used 0R39 since this was only available in my shop

biassed the all thing arround 90ma and made some tests in 68 and 78 volt rails ...with 78 volt rails i get about 50 volts in the output and amp works perfect for a very good bandwidth and also square wave starts to get round just about 20khz fairly good i thing for a thing like that so simply made


take a look at the tranistors
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Old 18th February 2010, 08:19 PM   #3
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at 1khz with a dummy load
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Old 18th February 2010, 08:20 PM   #4
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ar 10khz with a dummy load
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Old 18th February 2010, 08:21 PM   #5
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at 40 khz with a dummy load
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Old 18th February 2010, 08:24 PM   #6
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construction mess ....and 1khz signal just before cliping ...meanwhile and as we speak various tests have been done and for starts all is running very cool ...so lets see ...

there is a lot more to be done
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Old 18th February 2010, 08:38 PM   #7
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for this circuit the VI limmiter is not ready made yet in the next few days we will come to that also .....

given thwe oportunity and in any case somebody is reading this there is something to state and i would like to listen comments please .

In the forum there is a practice regarding number of outputs versus rail voltage to be calculated from the soar plots of the given transitors ....

there is ofcourse other ways to do it only thing you have to do is take a look at the comercial approach existing everywhere and mostly in the Japanese market or philosophy

the story is very simple .... just put a couple of transitors with 50+50 or 60+60 volt rails and limmit the current that flows from them with the vi limmiter

now i can listen to a lot of things of what is right or wrong but lets face it this was the Japanese approach ages now ...

Amplifier that has 50 volts output is a PA amplifier and a VI limmiter is a must and a fact

so ...opinion have to be given taken all the above as a fact ....

thanks for your time ...

regards sakis
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Last edited by east electronics; 18th February 2010 at 08:55 PM.
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Old 18th February 2010, 08:40 PM   #8
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For this sort of layout the square wave response looks very good
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Old 18th February 2010, 08:53 PM   #9
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yes you are right ...i was also amazed by it cause normally amplifiers on testing state like this one and especially while using 60 cm of rail cable and generally messed up wiring usually loop even if you breath next to them ...

i expect it to perform better when cased ( together with my power supply that forum rules will not allow to post )
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Last edited by east electronics; 18th February 2010 at 08:57 PM.
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Old 18th February 2010, 09:01 PM   #10
jaycee is offline jaycee  United Kingdom
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Only useful contribution I can make - consider an LED instead of 2x1n4148, and either dont share this between LTP current sink and VAS current sink, or put in a 1K base resistor at the VAS current sink to avoid problems with clipping.
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