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Old 9th June 2012, 12:33 PM   #1
Vostro is offline Vostro  South Africa
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Default Is 200W possible with simple topology ?

I was wondering what Possibilities are possible with this simple topology?

Maybe VAS not good enough?

Triple Output should not draw to much current

Load is 8R

Thanks
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Last edited by Vostro; 9th June 2012 at 12:55 PM. Reason: Forgot to add 8R as load
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Old 9th June 2012, 01:34 PM   #2
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I have made 250WRMS out into 4 ohms with triple output pairs with MJE340/350 as drivers and a 2N5401 as VAS, so yes you can make 200+ W with a simple topology like this.
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Old 9th June 2012, 02:13 PM   #3
AndrewT is offline AndrewT  Scotland
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3pr of 1943/5200 will be OK for ~200W into 8r0. But, you must keep them cool !!!!
1943/5200 have a pretty poor SOAR when Vce gets high, as in this amplifier.

BTW, how did you arrive @ +-61Vdc? If that is from a 115/230:40+40Vac transformer, you will not get anywhere near 200W into 8r0. and don't be tempted to use 45+45Vac to get to your 200W target. The 1943/5200 will not like it.
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Last edited by AndrewT; 9th June 2012 at 02:16 PM.
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Old 9th June 2012, 06:44 PM   #4
Vostro is offline Vostro  South Africa
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Quote:
Originally Posted by AndrewT View Post
1943/5200 have a pretty poor SOAR when Vce gets high, as in this amplifier.
Thanks, do you advice more pairs or other transistors.

Any Transistors you would advise.

This pair are not to expensive. (MG6330-R, MG9410-R)
http://docs-europe.electrocomponents...6b80f8a10b.pdf

This pair cost 50% more than pair above. (MG6331-R, MG9411-R)
http://docs-europe.electrocomponents...6b80f8a11c.pdf

Quote:
Originally Posted by AndrewT View Post
BTW, how did you arrive @ +-61Vdc? If that is from a 115/230:40+40Vac transformer, you will not get anywhere near 200W into 8r0. and don't be tempted to use 45+45Vac to get to your 200W target. The 1943/5200 will not like it.
Yeah I was thinking 45+45Vac 500VA transformer,
A local supplier has stock of two left at equiv. to 70U.S. dollars.
They are decent quality toroidals, I don't think Ill get them at this price
in my country again.

thanks.

Last edited by Vostro; 9th June 2012 at 06:50 PM. Reason: added VA rating
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Old 9th June 2012, 07:09 PM   #5
AndrewT is offline AndrewT  Scotland
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I used a 230:40+40Vac transformer fed from 240Vac (UK voltage) and got 170W into 8r0 using 3pr of mjl4302/4281 in a Leach clone.
They have much better soar than 1943/5200.
That 3pr of ONsemi can drive 6ohms speaker, but I would not rate the amplifier for 4ohms duty.
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Old 9th June 2012, 07:28 PM   #6
Vostro is offline Vostro  South Africa
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Thanks, we use 220 Volts at 50 Hertz here.
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Old 9th June 2012, 07:41 PM   #7
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My amp used three pairs of 2SD2155 and the complement 2SB1429 and ran off 2x60V supplies from a "800VA" transformer that in reality based on possible power output from the amp in 4 ohms seemed more like 350-400VA, i got 240WRMS from this amp in 4 ohms before the sinewave started getting clipped.

This amp even took a dead short for several seconds several times as i increased and decreased volume and survived, it got real hot in a hurry though. This caused by a overheated voice coil shorting out during a power test at low frequency around 10Hz.

I guess what kept the amp alive was that the transistors are mounted directly onto the heatsink with nothing but thermal paste between the heatsink and the transistors, instead the heatsinks are electrically insulated from each other and from the chassi mounting points.
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Old 10th June 2012, 01:33 AM   #8
jaycee is offline jaycee  United Kingdom
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You could also consider TO-3 package transistors which have better thermal capability. Look for MJ21193/4 transistors from Onsemi.

If you prefer flat packs, then the MJL4281/4302 or MJL21193/4 transistors from Onsemi are good, rugged devices. The Semelab devices you mentioned are also good devices from specification - the important part is good cooling. I'd probably suggest at least 4 pairs of transistors, though.

Also for your predriver transistors (Q15/Q16), try to find some TO-126 type transistor that can handle ~1A, while still being fairly fast. For example spec 2SC2690/2SA1220 or 2SD669/2SB649 type devices work well there.
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Old 10th June 2012, 11:49 AM   #9
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Default 200 watts

maybe this can help you
warm regards
andrew lebon
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Old 10th June 2012, 12:23 PM   #10
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hope this PCB helps. i will post full PCB later

Warm Regards
Andrew Lebon
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