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Old 13th September 2002, 05:06 PM   #11
leo529 is offline leo529
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dear vivek, is this what u need??

http://www.mif.pg.gda.pl/homepages/t...s/120_watt.gif
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Old 13th September 2002, 06:00 PM   #12
NickC is offline NickC
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marcus
how about decoupling the output section from the driver and ltp section via 10 ohm resistor and 470uf cap
helps in preventing any noise from the output section entering the cruical low noise areas(ltp)

for your emitter resistor, i feel u utilize slightly big value here
i used 0.1 ohm normally. it is enough to force sharing
bigger value means higher cost.

i see u include the miller dominating cap here, i guess the output transistors can be swap for sc3281,sa1302. Because motorola transistor hfe drop quite abit when current is higher while the toshiba as a relatively constant hfe throughout the current values

how come u utilize mje350 for the ccs? any particular reason
u could use the bs556 back rite?
i feel the design is solid and good. i guess no harm in tweaking it
who knows u could sell it as a kit
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Old 13th September 2002, 06:43 PM   #13
Vivek is offline Vivek  India
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Hey Leo,
I have that schematic. Thanks. I wanted to know how the M250 and this amp perform.

Vivek
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Old 13th September 2002, 10:18 PM   #14
guido is offline guido  Netherlands
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Vivek,

The elektor amp is from april 1982. I have a papercopy of the article, but it is in dutch (elektor is dutch). It is specked at being 100W into 4 ohm! I have build the amp for PA use long time ago. So 500VA transformer and 2 * 20000uF elko. Also using a fan with matching heatsink. It does not get hot, not even warm..
And a 19i case you can stand/dance on :->

In this setup it is fine for PA use, it was the only one to drive the FANE bas speakers we had in those days.. Fun. But i dont think it is serious hifi. Elektor published more amps after this one which are more serious hifi.

One think it lacked: a shortcircuit on the output terminals killed it.
Not really much PA there..... Case of replacing a BDX and back in business (i have a DC protection circuit installed, so only the amp breaks.).

Greetings,

Guido
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Old 14th September 2002, 11:03 AM   #15
Vivek is offline Vivek  India
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Guido,

Thanks for that piece of info.

Vivek
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Old 15th September 2002, 04:30 PM   #16
hugobross is offline hugobross  Europe
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Vivek,

the M250 looks like my new amp design, for which I've drawn the PCBs a few days ago, I'll get my PCBs tuesday. I'll publish the results of my amp soon if you're interested.

HB.
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Old 16th September 2002, 06:29 AM   #17
Vivek is offline Vivek  India
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Hi Hugo,
That would be nice. I am eager to see it. Let me know when it is done.

Vivek
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Old 11th November 2002, 02:28 AM   #18
Drafance007 is offline Drafance007
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Lightbulb THE M250

I also need some answers about the M250 amplifier...
What is with the diode on the input....what does the resistor 15 ohm does on the base of pre output ??? Please Whod do i Ask 4 Help ?
http://www.astro.uu.se/~marcus/private/m250.html
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Old 11th November 2002, 02:45 AM   #19
halojoy is offline halojoy  Sweden
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Default Re: THE M250

Quote:
Originally posted by Drafance007
I also need some answers about the M250 amplifier...
What is with the diode on the input....what does the resistor 15 ohm does on the base of pre output ??? Please Whod do i Ask 4 Help ?
http://www.astro.uu.se/~marcus/private/m250.html
The LED diode is used like a volt reference,
in the constant current source.
The resistor 15 ohm is used, when the current limiting transistors, T6/T7 gets active, to limit the current flow through the transistors.
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Old 11th November 2002, 12:08 PM   #20
Drafance007 is offline Drafance007
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Default Re: Re: THE M250

Quote:
Originally posted by halojoy

The LED diode is used like a volt reference,
in the constant current source.
The resistor 15 ohm is used, when the current limiting transistors, T6/T7 gets active, to limit the current flow through the transistors.
NO No What about naow 4 diodes 1n4148, what is their purpose ? ( D1-D4 ?
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