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-   -   sx-Amp and nx-Amp (https://www.diyaudio.com/forums/solid-state/236522-sx-amp-nx-amp.html)

PMI 18th July 2013 02:05 AM

nx-Amp heatsink size
 
2 Attachment(s)
Looks like the heatsink required for one nx-Amp board will be a minimum of 5-inches tall, assuming a common-type heatsink w. vertical fins. The holes for the power transistors are fairly close to the edge of the board, and the leads on the transistors cannot be bent too close to the body of the part. So, the minimum space required is about 6 mm on either side, meaning beyond the outer edge of the circuit board.

Bonsai 18th July 2013 02:13 AM

Yes, the transistors do jut out beyond the edge of th PCB. Note also that the PCB edge must rest on the output transistor cases - they act as spacers.

You can also rotate the PCB on your heatsink if that gives you a better fit.

Check out the construction details In the write - up.

Good luck -I am really looking forward to seeing these amps built by you guys up and running and your listening impressions.

PMI 18th July 2013 02:50 AM

Quote:

Originally Posted by Bonsai (https://www.diyaudio.com/forums/solid-state/236522-sx-amp-nx-amp-post3565251.html#post3565251)
You can also rotate the PCB on your heatsink if that gives you a better fit...

Yes, perhaps better heat transfer to the heatsink that way from the power transistors. I will try that too, but in general I prefer the input connector to be close to the back of the chassis, with a short cable. Either way, five inches tall, or even six if one does not mind some empty space inside.

:cheers:

pinnocchio 18th July 2013 02:04 PM

Looks good! Yesssssssss! :D

Junie 18th July 2013 06:28 PM

Dear PMI,

Kindly include me in:

nx-Amp PCB +nx-Amp PSU+Protection PCB.

Thanks.
Junie

Bonsai 19th July 2013 04:44 AM

Further update/correction from my side

Q9 and Q11 are specified as BC547C and 557C which are 45V max Vceo rated, high hFE devices.

Please do not use these devices, but instead use BC546C and BC556C which have a Vceo rating of 65V for Q9 and Q11

For some reason, I had it in my head that the 547 and 557 were 50V Vceo devices - which would in any case be too close for comfort if your rails are running at the max specified value of +-50V.

This is another item I have added to the document correction list - if you see any others, let me know.

Thanks

(data sheet here: http://www.fairchildsemi.com/ds/BC/BC560.pdf)

ivanlukic 19th July 2013 12:10 PM

Could BC546B and BC556B used instead? Local shop does not have C rank.

Idefixes 19th July 2013 12:43 PM

Quote:

Originally Posted by ivanlukic (https://www.diyaudio.com/forums/solid-state/236522-sx-amp-nx-amp-post3566765.html#post3566765)
Could BC546B and BC556B used instead? Local shop does not have C rank.

Not only local shop, "C" rank are obsolete fore 546/556 and difficult to find.

Marc

Bonsai 19th July 2013 03:10 PM

Yes, you can use B types if you cannot get C.

I just checked Digikey has them ( Fairchild) . But if you cannot get them where you are, the B will do. NXP does not do TO-92 bipolar small signal anymore so my recommendation is you go with Fairchild ( I have no checked ON).

Project16 19th July 2013 03:27 PM

SX Amp (single-sided PCB)
 
3 Attachment(s)
Hello all!

I fully intend to make this amplifier in the SX version, but in its entirety.
I have designed a single-sided pcb that n is not yet checked a hundred percent but I post my work anyway.
When everything is ok (I hope), I'll post the file. Pdf with the consent of the author.

Regards!


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