Diy Gallery

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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IMG_4367 by hydrovac, on Flickr

Neat work, how do they sound?

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_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_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_4416 by hydrovac, on Flickr

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IMG_4412 by hydrovac, on Flickr

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IMG_4442 by hydrovac, on Flickr

Quote:

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Originally Posted by realysm42

Neat work, how do they sound?

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Thanks realysm42,

The prototype sounded really pure with low noise floor. Even audiophile grade prompting me to build one with soft start and speaker protection against DC.

The specs are as below:

POWER OUTPUT: 200W rms/8 ohm
310W rms/4 ohm
800W rms/8 ohm (Bridge mode)
FREQUENCE RESPONSE: 20HZ-20KHZ +/-0.5dB
INPUT SENSITIVITY: 1V for 200W/300W
HUM AND NOISE: -105dB
THD: <0.1%
DAMPING FACTOR: 65

Hooking up output devices to PCB s.


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IMG_4419 by hydrovac, on Flickr

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IMG_4447 by hydrovac, on Flickr

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IMG_4551 by hydrovac, on Flickr

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IMG_4562 by hydrovac, on Flickr

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

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IMG_4648 by hydrovac, on Flickr

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

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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.

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

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

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

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IMG_4679 by hydrovac, on Flickr

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

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IMG_4669 by hydrovac, on Flickr
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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.

Nice job ;) have you had a listen yet?.
40mv dc offset isnt that bad both of mine are 20-30mv could be a slightly leaky cap try C7. I would have used 0.1% precission matched all the resistors in the ist stage as well.
Not sure I understand the method of setting the Bias current ? normally its a mv reading accross the emitter resistors or disconnect the +ve lead to the board and measure the total current draw (unloaded output) in ma

Alan

Quote:

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Originally Posted by 337alant

Nice job ;) have you had a listen yet?.
40mv dc offset isnt that bad both of mine are 20-30mv could be a slightly leaky cap try C7. I would have used 0.1% precission matched all the resistors in the ist stage as well.
Not sure I understand the method of setting the Bias current ? normally its a mv reading accross the emitter resistors or disconnect the +ve lead to the board and measure the total current draw (unloaded output) in ma

Alan

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Hi Alan,

Thanks for that. I replaced the C7 cap with a new one and now its reading 1.5 mv on right ch and 2.8 Milli volts left ch, in 200mv range of multimeter. Shouldn't this be zero volts? Can I connect the speaker in a condition like this?

The author suggested to setup the Bias as shown in the link.
http://users.otenet.gr/~athsam/300w.htm

I will have to remount the transistors and give it a listening test.

Your Dc offset is excellent and will not damage your speakers dont worry ;)
Mine ar 30ma in both channels as I use a Mil spec wet tants in the feed back position and they are a bit leaky as well but it still will do no damage if mine goes over 50ma I will change the caps but many say as high as 100ma is still OK.

Alan

ITS ALIVE !!!

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Finally got around to fitting new CCD's & the B4 lives :wowzer:

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As you can see I paid special attention to the wiring :lol: :upyours: