ExtremA, class-A strikes back?

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Do you have any other way of lowering the bias even if just a little, other than emitter resistors which I already did (3x 1ohm 5 watts - 0.33 ohm). I'm at 65 celcius on the heatsink after 3 hours and stable but it is a little too hot... I'm thinking of fans but prefer not to use them.

Thanks
Do
 
@Do,

You mentioned in a previous post your PCBs were starting to wear out due to swapping out parts etc. I'd be happy to send you a new set if required. It would be a shame to abandon this project after all of the work you've put into it. Just let me know and I'll get a new set sent off to you.
 
Hi Sander,

No need for PCB yet. I've been able to solder under the PCB (top traces were just pads) without any issues so far.

Here's the PCB with drivers mounted on the Sanken since one of the tap hole has a broken screw inside and cannot be removed. Since the drivers need to track the Sanken heat to prevent thermal runaway then this should be more than edequate but a little less elegant. You can also see the new 5watts 1% 50ppm non-inductive emitter resistors (3x 1 ohm instead of 4x 1 ohm) in order to help dissipate the Sanken emitter lead heat transfer and lower the bias. I'm at 59 watts in Class A under 8 ohms load at the moment.

2015-10-05%25252022.16.31.jpg


Ciao!
Do
 
jacco vermeulen said:
I take it you have someone to do that machining for you ?

(~100 bucks on your end, a set for engine short-block bolts does a whole lot more )
Click to expand...

Hi Jacco,

I do my own machining, sorry not a broken screw but broken tap inside... It is a 4-40 hole so it is extremely hard to remove but I still had some grip for a screw, just a little short and cannot put too much force to it. I tried a punch to break the tap pieces by pieces but it was getting too deep for the punch to be effective. Other option is to drill the tap with carbide bit but the tap has to be flush for this to work properly.

Anyways, should be all fine the way it is now?

Thanks
Do
 
Plugged in the second channel and adjusted the offset, a little more difficult to adjust than the first channel, it drift a little but not bad.

So far it sounds fantastic! I have to cool it better than I can listen to it for a longer period of time and do a full burn in as well.

I'll keep you posted

Do
 
I have found a thermal pad product far superior to Kerathern Kerafol Red according to the specs here

http://industrial.panasonic.com/lecs/www-data/pdf/AYA0000/AYA0000CE2.pdf

Keratherm Kerarol Red 0.25mm is 6.5 W/mK but this Panasonic PGS Sheet is anywhere between 700 and 1950 W/mK (2 to 5 times as high as copper) according to their spec sheet. Anyone tried those? The price is really good so I was thinking of using this for the Sanken.

Do
 
Hopefully I'm reading this properly...

The only thing that worries me are the ones with low thermal resistance are rated 100 celcius max... and the thermal resistance is not specified, just "low thermal resistance" is written...
 
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