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Old 11th June 2009, 08:21 AM   #21
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I wonder how many of us would buy the boards if it were the same A30 layout as per pic for the fets, i would struggle unless i could get the right chassis and i do not see that happening, unless someone can point me in the right direction.
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Old 11th June 2009, 08:54 AM   #22
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Yes I agree it is not my preferred layout.
However with this layout it does have the benefit of mounting it vertically (ie directly to the heat sink) so less space is taken up in the case. So you have more room for your transformer and power supply.

I generally like to use heatsinks with the built in bracket for easy mounting of transistors (no need to tap threads) just bolt them down and you are good to go.
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Old 11th June 2009, 09:08 AM   #23
EUVL is offline EUVL  Europe
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a) Why not make the PCB ready for an AJ-X ?
b) What pin layout for input diff pair (2SK109) ?
c) How much ? (price and X-Readiness will determine my quantities)


Patrick

PS As you all know, you can still use 2x 2SJ74BLs with the 2SJ109 pin layout.

http://www.diyaudio.com/forums/showt...38#post1690438
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Old 11th June 2009, 09:16 AM   #24
EUVL is offline EUVL  Europe
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> I wonder how many of us would buy the boards if it were the same A30 layout as per pic for the fets ....
> Yes I agree it is not my preferred layout.....

Please kindly explain this to me, as I do not quite understand the problem.

For Class A amps, you always want big heatsinks. The layout show will simply allow you to lay the PCB parallel to a heatsink with a flat (vertical) mounting surface. There are many of those, like the ones from Conrad (though I use something else personally). Just 4 tapped holes, 4 insulators, 4 screws, and it's done.

Or not ?


Patrick


PS Here is an example (my balanced F5) :

http://www.diyaudio.com/forums/attac...amp=1213462615
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Old 11th June 2009, 09:38 AM   #25
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I generally mount transistors exactly like Nelson does it, and I already have the heat sinks.
If we go with the current layout I will have to buy new heatsinks.

However, maybe it is time I learnt how to tap threads.

By the way we have almost reached the half way point in 5 days.
At this rate we should have the numbers we need within another week.
It looks promising.
I really hope this one goes ahead, as I think this really is a special amplifier. I don't have full range drivers so F1, F2, are out of the question. My speakers are 4 Ohm so F3 is not that great either. I have a B1 preamp so F4 is out of the question.
So it is either Aleph J or F5. I know I love the sound of 2nd harmonic from experience with playing Bass guitar.
So Aleph J I predict will be my favourite (Well F3 will be my favourite for headphones). The only adjustment is for higher bias for 4Ohm load. I think the Aleph 30 or was it 3 (or was it both) was biased to give 60W into 4 ohms.
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Old 11th June 2009, 10:32 AM   #26
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Quote:
Originally posted by EUVL


Please kindly explain this to me, as I do not quite understand the problem.


No special problem.
However my experience tells me that the efficient layout of the heat sources gives me better chances for the reduced heat sink temp. By the way, I also like to have better spaces between each component for relaxed soldering job . . . unless the short signal path is required for better sound . . .



ahh . . . isn't this GB . . . ?
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Old 11th June 2009, 11:17 AM   #27
flg is online now flg  United States
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I beleive the theory is that devices mounted on a heat sink horizontally spaced is more efficient. And, devices spread somewhat evenly accross the heat sink is also good. Verticle mounting requires taller heat sinks that will not perform as good with convection. You basically get more air with a horizontal configuration.
However, there is the philosophy that devices mounted in close proximity will force better tracking, stability and DC offset at the output
I would prefer the "longer" layout rather than the square or rectangle of Peter's current boards. A board about 8-10" long with all the power devices on one side
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Old 11th June 2009, 11:54 AM   #28
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Put me in for 4 boards
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Old 11th June 2009, 01:05 PM   #29
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I'll take a set for stereo
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Old 11th June 2009, 02:49 PM   #30
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Please correct me if i am wrong but my impression was that the board pictured is Peter's style of using short circuit paths and narrow columnar chassis. So the two channel's output devices are spaced only a few inches across from one another. Heat sinks in these Pass designs tend to be large, and nearly all chassis i come across are your standard rectangular enclosures with a face plate of about 15-19 wide. So that left and right output devices sit on the large heatsinks on either side panel and its adherent heatsink. How can Peters small board be made to meet this standard enclosure?????as per nearly all Pass lab designs. Do we buy one very elongated narrow enclosure with the power supplies either end and the circuit board in the middle?? Is there enough air convection capability in such a narrow design without drilling lots of holes in all directions for ventilation?? Or is my eyes decieving me and the board shown is actually dual mono which can be split in half??
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