redesign amp need

[prorms]

Could anyone get this amp to put out 250ws?

[AndrewT]

Hi,
having difficulty with my neck and my eyes. Must be my age!
can you confirm the output devices? 2pair MJ15003/4, drivers 1pair MJE?

[prorms]

they are mj15003
mj15004
mje15034
mje15035
bd139

[MikeB]

Okay, after having put my monitor on the side and rearranged my neck i wonder where you get your ground from ?
You should have a split supply (like 2x36v in series with ground in the middle) or have a virtual ground.
As you can see you have -10v for v- and +60v for v+. This will float as it is in its mood and you have no defined inputvoltage.
I am still convinced that your outputstage protection does not work.

Mike

[edl]

Sorry, but that's one of the worst amp design I've ever seen...

[prorms]

some one think could get this to work?????????????

[MikeB]

But that would be a new design and not a redesign. Anyway, the max watts into 8 ohms would be 60watts, not 250watts.
I suggest that you start with an existing proven design, just to get experience and less frustration.

You will definitely need a symetrical powersupply, giving a +/- voltage.

Mike

[destroyer X]

You will need to change some resistors into trimpot...the 100 ohms units, and also the input 1K or 1K5.....using fix plus series devices, to equalize exactly the current to both halves and to reduce the of set to minimum.

It is around 32 milivolts, and of course, can be reduced.

This amplifier was only simulated, it was not assembled.

Thank you to call me to help.

But may work fine.

regards,

Carlos

[Greg Erskine]

That face looks vaguely familiar.

Nice to see you back, Carlos.

[AndrewT]

Hi,
considering ONLY the output stage and ignoring the earlier comments on the design applicability.

You will need about 4pairs of MJ15003/4 for 250W into 8ohms with a phase angle of 60degrees and Tc max<45degreesC running on about 72Vrails drooping to about 69V fully loaded. This same output stage will also drive 4ohms to 35degrees phase. But most speakers have much larger reactance than this.
The suggested stage is for 8ohms speakers or above.
I do not know if the drivers could cope with 4pair but if you proceed I can do the calculations for you.

You will need BIG sinks to keep this much power that cool if you set up a large Iq (4pairs @ 50mA/pair) or squeeze lots of output power from the amp. If you can keep them cool the transistors are capable of driving your output all day at any audio frequency.