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Old 7th April 2012, 04:47 PM   #151
fotios is offline fotios  Greece
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Quote:
Originally Posted by comasus View Post
Then what could be the frequency range ??
Practicaly speaking, will be the same. 20Hz to 20000Hz +/-1dB.
Don't worry so much about this, here we have to do with a PA audio power amplifier.
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Old 7th April 2012, 04:52 PM   #152
comasus is offline comasus  India
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Originally Posted by fotios View Post
Practicaly speaking, will be the same. 20Hz to 20000Hz +/-1dB.
Don't worry so much about this, here we have to do with a PA audio power amplifier.
Yes sir however we cannot hear beyond 20Khz

then we cannot find change in the clarity of sound right??
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Old 7th April 2012, 07:22 PM   #153
fotios is offline fotios  Greece
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Quote:
Originally Posted by comasus View Post
Yes sir however we cannot hear beyond 20Khz

then we cannot find change in the clarity of sound right??
I cannot hear beyond 8KHz
But keep in mind that PA speakers are very revealing of any difference due to high sensitivity (101 to 103dBSPL/1W/1m). In a same way, because we know that a PA power amplifier is designed to drive PA speakers, mid-high frequency area is of less importance than low frequency. Big 15 - 18" PA woofers demand lot of power to move, while mid - high compression drivers loaded with horns demand less power.
The difference is that: MJ15024-25 have Ft = 4MHz while MJ15020-21 have Ft = 20MHz in the expense of Ic = 4A. While the new MJL3281A-1302A have both Ft = 30MHz and Ic = 15A.
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Old 8th April 2012, 12:38 AM   #154
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Hi Foti, how are you doing?

I have a power amp module with 5 pairs of MJ15024/25...I tested it and it pushed out 550Wrms into 4 ohms. According to your experience,will this amplifier survive under such continuous usage?
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Old 8th April 2012, 06:16 AM   #155
fotios is offline fotios  Greece
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Quote:
Originally Posted by JohnTubeamp View Post
Hi Foti, how are you doing?

I have a power amp module with 5 pairs of MJ15024/25...I tested it and it pushed out 550Wrms into 4 ohms. According to your experience,will this amplifier survive under such continuous usage?
Hi Yanni
Your test results:
Vrms = square root ( Prms X Load ) = sqare root ( 550 X 4 ) = 46.9Vrms.
Vpeak = Vrms X square root 2 = 46.9 X 1.414 = 66.32Vp.
Irms = Vrms / 4Ω = 46.9 / 4 = 11.72Arms
Ipeak = Irms X square root 2 = 11.72 X 1.414 = 16.57Ap
This Ip is shared among 5 output transistors, so Ip per transistor:
Ipeak = 16.57Ap / 5 = 3.314Ap per transistor.
MJ15024-25 SOA curve (Safe Operating Area) shows:
Ic = 4.5A max for Vce = 70V
Well, you are inside SOA curve by 120%. You could feel safe yet under continuous operation of amplifier for many hours in peak power. I think is not necessary to remind you that blowers are needed for such usage.
Καλο Πασχα και καλη Ανασταση!
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Old 8th April 2012, 08:53 AM   #156
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Thank you Foti for the information. Yes of course I use air force cooling for this amplifier...I don't want to cook my coffee on it....

Καλο*Πασχα*και*καλη*Ανασταση*επισης!

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Old 24th May 2012, 06:28 AM   #157
emmi is offline emmi  India
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PCB for this amp?
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Old 24th May 2012, 07:30 AM   #158
fotios is offline fotios  Greece
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Originally Posted by emmi View Post
PCB for this amp?
In few months. I have to finish two audio projects for which i received payment in advance. That will take me at least 4 months. Next from this i will design new, more flexible PCBs and upgraded protection circuit for Dirty Harry.
Please be patient.
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Old 26th May 2012, 06:07 AM   #159
emmi is offline emmi  India
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Originally Posted by fotios View Post
In few months. I have to finish two audio projects for which i received payment in advance. That will take me at least 4 months. Next from this i will design new, more flexible PCBs and upgraded protection circuit for Dirty Harry.
Please be patient.
Ok sir we will wait for it
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Old 26th March 2013, 04:05 AM   #160
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Default great sound

thanks from my heart core that you gave us a design who's sound response i was searching since 2 years ,though i am not so skilled ,but i tried to make this amp.
but a problem i am facing that it heats much in spite of force cooling.i have used 1943/5200 in output as well as in place of mje15021/20.
sir i will wait for your kind suggestion.
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