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Old 17th April 2007, 09:56 PM   #881
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Default I hope so Sparkle, as we have not those fake specifications.

Depending the voltage you decide to use some range of power will result...we do not know exactly how many watts of heat some fake transistor will hold.

hehe....i think we have to make a burn test....when burned we will conclude the fake unit limit of power..ahahahha...not way to do that...so..we never know exactly if it will hold 50 watts of heat...80 watts of heat or even 150 watts of heat.

Also the maximum current....we just do not know...the better is to use your MJs...as they are something that we can trust.

I feel good...very happy, as you made the Dx amplifier choice.

I hope i can help you in something.

Inform the supply voltage and output impedance and i will suggest a lot of things...of course, if you need some.

regards,

Carlos
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Old 17th April 2007, 10:12 PM   #882
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Default It is very strange, as Klaas enclosure may hold 430 watts.


I was using my "eye calculator"...and i have concluded that Klaas heatsink is more than enougth...as 2 channels will dissipate 320 watts of heat when driving 4 ohms loads and near the clipping.

Klaas heatsinks...even reducing heat sink capacity because some panels are not in the correct convection position..also the heatsinks are not in the best position...even this way, the case may be able to hold 2 channels of the Dx amplifier.

I am extremelly curious about.

Klaas is hardly busy...having small time those days...we will have his informs, i hope soon.

regards,

Carlos
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Old 17th April 2007, 10:19 PM   #883
Nordic is offline Nordic  South Africa
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I had alot of trouble lapping one of the transistors... took forever to get it to lay flat... eventualy used asmall to220 heatsink on top of the transistors to help pull it flat...


Then I realised one of the pins is conected to the heatsink tab.... so I guess I will have to use those seethrough ceramic disks that came with the transistors... luckily there are 4...

Klaas, don't you think the back of you amp should be the top. to help with thermal dissipation....
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Old 17th April 2007, 10:32 PM   #884
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Default It is very positive that you are extremelly carefull about those details Nordic.


Not flat transistors use to create enormous problems...many of them are bent in such a way that air bubbles are retained under the capsule...between the heatsinks and the transistor back.

This is one of the main cause of problems...i had so many that i cannot count.... but happened dozen of times.

Warped Chips use to produce problems too...very common in Panasonic Class H chip amplifiers... sanding and making it flat...return to work fine, without the protection entering and that damn relay clicking cutting your music... I do not remember if those chips were made by Panasonic..i think another factory was producing to Panasonic.

I do not think you must go to be a Gardener dear Klaas..compared with others that i was testimony of the mess they done, you are many times better...and those ones i was using as reference in my thougths, would not be a good gardener.

There are science to a Gardener too...as you know, you have that experience surrounding you...your country is a big garden as i know.... very old tradition related flowers.

But when we install amplifier boards into cases....many times, we start to have problems because of capacitances created from the lower ground place (the case) referenced to the board copper lines.

Ground loops happens usually.... not good solder joints in the ground can create a hell problems.... noises from the transformer and magnetic pickup from the nearby transformer...sometimes the amplifier has small input cap and low sensitivity, and we do not listen that hummm easy...but for sure they are affecting too.

Well.... sonner or latter you will find the guilty...if not...please, arrange a place to me in Holland.... i will be a gardner too.

regards,

Carlos
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Old 17th April 2007, 10:40 PM   #885
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Default If the suspect goes to the case..the heatsinks position or size.


The good test is to put a fan over it...a ventilator...well, to force it to run cool outside....it can be producing too much heat because of circuit problems...and even cooler the outside...the transistor may overheat.

If the amplifier continue beeing unstable. even forced to work cool....for sure the problems will be in the circuit.

regards,

Carlos
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Old 17th April 2007, 10:41 PM   #886
Nordic is offline Nordic  South Africa
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I will use some computer thermal compound for that chip... too expensive to use on all 4, the cheap white stuff will have to do for the others...

Do the first transistor after diffirential pair need heatsinking too?

I put some DIY sinks pulled from a PC PSU and sawed smaller on the drivers... probably good for about 3 to 4W

I always enjoy the wireing the amp up part....useing the same power cable that is inside the walls of my house... just cant start with the case, until I know how big the transformers are, and I won't know until I get them, as they are custom... I guess about 15cm cubed...
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Old 17th April 2007, 11:15 PM   #887
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Default I think your trafos will be around 12 centimeters each side.


For sure they will be big.

What will be the heatsink position?

Will be atop the amplifier or at the amplifier sides?

regards,

Carlos
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Old 17th April 2007, 11:23 PM   #888
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Hi Klaas,

If you suspect oscillation place an AM portable radio very close beside the amp - not tuned to a station - and switch the amp on and off.
Do you hear anything at different frequencies ?

You could try increasing the VAS connected C.dom; try 47 to 100pF. The value necessary will depend upon devices being used.

Keep all output wires away from input, and keep source impedance low.

Is your heatsink grounded to the star point ? Should be !

Even experienced constructors can have oscillation problems, so don't be worried.

Cheers ......... Graham.
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Old 18th April 2007, 06:26 AM   #889
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Default Dx amplifier can play using "unobtanium" input plugs


Also can receive audio from a "demagnetized" CD.....and it is the only one that will sound the same after those modifications done.

Only your pocket will be different...a little bit more empty.

Be free to change things into your amplifier...but do not believe that those modifications will always sound.

regards,

Carlos
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Old 18th April 2007, 09:21 AM   #890
kvholio is offline kvholio  Netherlands
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The problem i have with overheating is with both amps,
it has nothing to do with Greg's new pcb.
I'm sure the problem is somewhere in my build, i will investigate some of the things suggested but my time
is very limited the next days.
The heatsinks i'm using are the smaller ones i used earlier, they're about 0,87 c/w .

Best regards,

Klaas
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