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Old 8th March 2010, 08:34 PM   #1
sekhar is offline sekhar  India
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I am planning on making powerfull sub woofer amp nearly (600-1000W RMS)
I am including a circuit which i know works very well cause i designed it and has very good sonics .......

I need to know the following :-
1.How much voltage can be used in this amp safety ?
2.need help in reconfiguring the bias control scheme
3.Wat modification r needed.........
4.R the output & drivers good enough?

circuit
Click the image to open in full size.


regards
sekhar
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Old 8th March 2010, 09:26 PM   #2
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I dont like the bias due to an open wiper might wipe out all your output transistors.

Put the pot in the bottom leg wired as VR and put a set resistor in the top leg.

Teh 2sa1837 might need a 100pf from base to collector to stop oscilation.
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Old 8th March 2010, 09:40 PM   #3
sekhar is offline sekhar  India
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Quote:
nigelwright7557
I dont like the bias due to an open wiper might wipe out all your output transistors.

Put the pot in the bottom leg wired as VR and put a set resistor in the top leg.
can show how is it supposed to be done .......AND how much voltage can this amp handle

regards
sekhar
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Old 8th March 2010, 09:48 PM   #4
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Quote:
Originally Posted by sekhar View Post
can show how is it supposed to be done .......AND how much voltage can this amp handle

regards
sekhar
You wont need the zener, thats just me being overprotective.


Click the image to open in full size.

Last edited by nigelwright7557; 8th March 2010 at 09:51 PM.
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Old 8th March 2010, 10:03 PM   #5
sekhar is offline sekhar  India
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component values r nt readable .............
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Old 8th March 2010, 10:08 PM   #6
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Quote:
Originally Posted by sekhar View Post
component values r nt readable .............
1k resistor
MPSA42 transistor.
1k pot.
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Old 9th March 2010, 03:41 AM   #7
sekhar is offline sekhar  India
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Quote:
by nigelwright7557
HI, is this the way it should be and does the bias tranistor needs to sit on main heatsink ?????and wat is the maximum voltage applicable......??????

circuit
Click the image to open in full size.

regards
sekhar

Last edited by sekhar; 9th March 2010 at 03:51 AM.
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Old 9th March 2010, 12:55 PM   #8
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Is it me or would the 1n4007's across the Vbe multiplier limit the bias to barely on? Good safety for open wiper as originally drawn, like Nigel's zener. It just strikes me as too safe.

How much rail voltage the amp can handle depends on a number of factors, including the load, your heat sinks, your isolator choice and a few other things. Pull out the data sheet for your outputs and take a look at the safe operating area curves. Just a guess, but with 4 pairs of outputs, you should probably limit your rails to +/-60V or so. With 4 pairs of plastic outputs you should think 200W/ 8R max.

Output device Safe Operating Area (SOA) will be your main factor determining the maximum rail voltage your chosen design can handle - especially for Subwoofer duty which tends to be high power and low impedance. There are plenty of threads here discussing SOA calculations. Time to read.

For 600-1000 W out into 4 ohms (or is it 2?) you should have at least 8 pairs of outputs, if not 12. The more heat sink you have the fewer you can live with but reliability will be better with more. You may need to update the driver section to handle the increased drive current needed by the additional outputs.

I probably should have mentioned this first, but if this is your first amplifier build, for safety you should probably do something smaller first or buy something like HPA-NXV1200 1200 watt MOSFET Audio Amplifier Module The rail voltages needed for 1,000W are potentially lethal. In the US there are plenty of PA amp choices that work well for subwoofer duty that can be purchased for well below the cost of building something reliable yourself. Maybe you can find something used.
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Old 9th March 2010, 01:41 PM   #9
sregor is offline sregor  United States
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2 minor nitpicks. 1) you have the collectors and emiters reversed on the positive output transistors and 2) The outputs are mislabeled (2sa1943 x 4 should be on the positive side and 2sc5200 should be on the negatives side. Also a questtion going back to the 1n4007 diodes across the bias circuit. It looks like the current limiting circuit won't be able to current limit very well with this bias circuit. Good luck with it.
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Old 15th March 2010, 03:49 AM   #10
sekhar is offline sekhar  India
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Quote:
Sregor
2 minor nitpicks
thanks for pointing out my mistake actually i was out of town for a few days i am uploading the corrected image and with bias arrangement kingly give out ur drawings an suggestion and wat do u think about multi slope vi limiter

corrected circuit

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regards
Sekhar
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