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300 watt Hi-fi power amp project.

post #1 of 4
Thread Starter 

300 watt Hi-fi power amp project.


Hi all DIYers,

Building a 300 watt Hi-fi power amp, which we designed and prototyped few years ago. Please follow the links for details.

http://www.diyaudio.com/forums/solid-state/10387-310w-power-amplifier.html

http://www.diyaudio.com/forums/solid...ml#post1330047


PCBs have been fabricated and gathering all components on hand.
Few pictures of the same.

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IMG_4459 by hydrovac, on Flickr

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IMG_4458 by hydrovac, on Flickr

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IMG_4461 by hydrovac, on Flickr

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IMG_4462 by hydrovac, on Flickr

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IMG_4570 by hydrovac, on Flickr

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IMG_4575 by hydrovac, on Flickr

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IMG_4465 by hydrovac, on Flickr

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IMG_4464 by hydrovac, on Flickr
 
 
Assembling of PCB s almost done, trying to place them in the chassis.

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IMG_4617 by hydrovac, on Flickr

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IMG_4616 by hydrovac, on Flickr

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IMG_4618 by hydrovac, on Flickr

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IMG_4311 by hydrovac, on Flickr

Mounted them, power supply wiring done and commissioned.

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Holes for output devices drilled on heat sinks using a TO3 jig. Input and speaker binding posts holes done and connectors mounted.

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IMG_4448 by hydrovac, on Flickr

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IMG_4366 by hydrovac, on Flickr

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IMG_4556 by hydrovac, on Flickr

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IMG_4481 by hydrovac, on Flickr

This is the den for our hobby & passion, and where all our classics come to life.

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IMG_4399 by hydrovac, on Flickr

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IMG_4398 by hydrovac, on Flickr

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IMG_4397 by hydrovac, on Flickr

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IMG_4396 by hydrovac, on Flickr

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IMG_4315 by hydrovac, on Flickr

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IMG_4314 by hydrovac, on Flickr

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IMG_4313 by hydrovac, on Flickr


Power transistors mounting process and progress.

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IMG_4420 by hydrovac, on Flickr

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IMG_4412 by hydrovac, on Flickr

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IMG_4409 by hydrovac, on Flickr

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IMG_4416 by hydrovac, on Flickr

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IMG_4414 by hydrovac, on Flickr

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IMG_4412 by hydrovac, on Flickr

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IMG_4449 by hydrovac, on Flickr

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post #2 of 4
Thread Starter 

Hi friends,

Sorry for the long gap in my post as I was preoccupied with other commitments. In continuation to my earlier posts, here is progress in amp build.
Checking the DC rail voltages: Left channel, Right channel, both channels


IMG_4645 by hydrovac, on Flickr

IMG_4646 by hydrovac, on Flickr

IMG_4648 by hydrovac, on Flickr

Checking full rail voltages: Left channel, Right channel, - Ve and +Ve rails


IMG_4652 by hydrovac, on Flickr

IMG_4653 by hydrovac, on Flickr

IMG_4655 by hydrovac, on Flickr

I am supposed to get around +62 and -62 volts DC on rails. The increase in reading is because of the mains input voltage (250 volts AC). Toroidal transformer winding is rated for 230 volts primary.


IMG_4682 by hydrovac, on Flickr

IMG_4686 by hydrovac, on Flickr

IMG_4683 by hydrovac, on Flickr

Setting the quiescent bias current for output stage:
Fabricated a 10 ohm 5 watt wire wound resistor suitable for the fuse holder.


IMG_4671 by hydrovac, on Flickr

IMG_4674 by hydrovac, on Flickr

Inserted in +Ve side holder and switched on the power. Adjusted the trim pot to get, 1.0 volt across the resistor.


IMG_4658 by hydrovac, on Flickr

IMG_4660 by hydrovac, on Flickr

IMG_4661 by hydrovac, on Flickr

IMG_4662 by hydrovac, on Flickr

IMG_4657 by hydrovac, on Flickr

IMG_4659 by hydrovac, on Flickr

You can see the thermal sensing bias transistors mounted mid way between the power transistors on the heat sink. Good going so far.


IMG_4678 by hydrovac, on Flickr

IMG_4680 by hydrovac, on Flickr

IMG_4679 by hydrovac, on Flickr

Now, looking at output side. Measuring the speaker output terminals for DC.


IMG_4669 by hydrovac, on Flickr

IMG_4668 by hydrovac, on Flickr

IMG_4667 by hydrovac, on Flickr

Left channel looks clean without any DC. But right channel is showing 0.04 volts. There seems to be a hitch somewhere. I will get back with updates after trouble shooting.
Thanks for looking and following the post.


Edited by hydrovac - 8/2/13 at 4:25am
post #3 of 4
Thread Starter 

Actually 40mv dc offset isn’t that bad. I traced it to a slightly leaky cap. Replaced it and now it reads 1.5mv on right channel and 2.8mv on left channel, in 200mv range of multi meter.

My Dc offset is excellent and will not damage the speakers, but many say as high as 50mv is still OK.

I connected a source and performed an extensive listening session. Must confess the amp has an amazing sonic quality.


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Edited by hydrovac - 8/12/13 at 8:33pm
post #4 of 4

That is a pretty impressive build. Well done!

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