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Old 19th February 2003, 04:47 PM   #1
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Question high power amp..

what i need to do to make my amp stronger?
1) to change the medium transistros to more power?
2) to change the output transistros to more power and more transistros?
3) to change the power supply to get more V and A ??
4) change to caps to more volt ?
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Old 19th February 2003, 04:54 PM   #2
JBL is offline JBL  Canada
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Build another amps becaus you will need to change most of the amp anyway.

And the bias circuit of alot of amp will not be able to stay stable with bigger output stage(mostly becaus of thermal stability)

The heatsink will need to be bigger also.
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Old 20th February 2003, 12:24 PM   #3
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how to the "300W Subwoofer Power Amplifier (ESP)" are 300W RMS and the amp work on 56V with 4 output transistors -2sc5200

and my amplifier us in 8 transistors of 2sc5198 and the power supply is 70V and in CARaudio forums thay say to me that my amp only 25W RMS....

how it can be ???

* the medium transistor is matter?



"300W Subwoofer Power Amplifier (ESP)"
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Old 20th February 2003, 08:38 PM   #4
Jeff R is offline Jeff R  United States
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They rate the amp at 150 W, not 300 W.

I am not aware of the amp you are using, so I can't comment on its actual power. If powered off of +/- 70 VDC, I agree, it would seem to be a lot higher than 25 W.

In general, more transistors equal more power, but it is not an absolute. So, if one amp has 4 and other has 8 output transistors, one can't assume one has twice the power of the other. The ratings of the transistors and the heatsinking have a lot to do with how many of them you need for a certain power level. Likewise, rail voltages are a pretty good indication of output power, but one also has to look at how beefy the power transformer is.
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Old 20th February 2003, 09:08 PM   #5
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the power supply of my amp is 50~0V AC 750VA it is big power supply... in my amp i have a 8 transistors of 2SC5198-2SA1941
and i connect the amp to home speakers of 300W MAX on 8 OHM and the amp dont out a high power... the i double the medium transistors (2sc2690A - 2sa1220A) from 2 medium tran' to 4 tran' and the power become stronger.... it can be?
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Old 20th February 2003, 09:30 PM   #6
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look !
in the start the amp work on 8 medium transistors... i take them out and i connect all 8 transistors to 2 medium transistors...

because i connect him only for 2 ransistors the output power can down ????? in the start was 8 ransistors...
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Old 21st February 2003, 09:25 AM   #7
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someone
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Old 21st February 2003, 10:12 AM   #8
JBL is offline JBL  Canada
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Maybe it was designed to drive two ohm load so the power at 8 ohm is quite low.

But cahnging the medium power transistor should not change the power output of the amp.
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Old 21st February 2003, 10:24 AM   #9
JBL is offline JBL  Canada
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25W from that is kind of low their must be a mistake somewhere.

From eing that low it would be firly easy to make it clip is that the problem you have oy can't you just make the gain high enough. Maybe it's the signal level that is to low.
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Old 21st February 2003, 11:11 AM   #10
moamps is offline moamps  Croatia
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Hi, DJ.

some A:
maximum output power with +-70V DC is about 300W/8E and 600W/4E in these condition (IMHO):
1.enough voltage amplification (from ca 1V RMS to 50VRMS),
2. enough current amplification-delivery from output BJT-s ( for 8E is ca 6A, for 4E ca 12A), global Beta must be enough (from ca 100mA to 6 or 12 Amps)
3. enough DC power from power supply (if Amp is in class AB for 300W/8E is ca 450W for one ch)
4. enough power capability of output BJT-s (SOA)( current, voltage, power disipation)
5. enough heatsinkig

With new bigger BJT-s you reach points 4 and maybe 2. You must check point 1 (with ca 1V on input, on output must be ca 50V without load), and 3, and after longer work point 5 (temperature on BJT-s)

Can you post shematic of amp? May help in discusion.

regards
zzeenn
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