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Green Wagon

Nelson Pass First Watt M2

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2 minutes ago, tcressida said:

DIY just like home cooking u can use the best  ingredients, nice job n looking good too .

You can be assured that Paul only uses the best and freshest ingredients. 

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I have found that you must look at any build in a holistic way and above all try and see components working as a team 

Building and tweaking crossovers has given me an appreciation and understanding that both capacitors and resistors have a sound signature getting this combination right can achieve nirvana in an audio component 

 

The M2 is a lovely amp 

So much so that I end up turning on the system and start listening to something on a daily basis 

 

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On 01/06/2016 at 7:33 PM, Green Wagon said:

Before we start,

I would like to say, Many thanks to Nelson Pass for his generosity in freely sharing his designs with the world.

I also need to thank 'Tea-bag' from diyaudio for his time and effort in designing and making available the boards seen here.

 

Ok this is no where near complete.

But I think the owner is wanting to see some pics displayed.

Expect gradual updates. Eventually.

 

SO.

 

Paul has been bitten by the Pass bug. Bought a second hand Decky F5, Got me to change it to an F6, And has now decided he wants a fresh M2.

After much discussion, the plan was enacted, parts were ordered, parts have arrived, parts are being assembled.

 

I present the pics below as a 'work in progress'.

 

Just a few boxes of parts. And some of those boxes contain several deliveries.

 

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Not all of the parts, just enough to get started on the various boards.

 

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Selected positions will use Audio Note Tantalum Non-magnetic resistors.

 

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Boards for the actual Amp modules.

 

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Boards for the power supply section. CRC filter fed by fast diodes with snubber caps.

 

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Underside, populated, cleaned, ready to go.

 

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Top side.

 

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Mounted onto the heatsinks.

 

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Neat trick from a gent on diyaudio.

 

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Using smaller TO220 heatsinks as a way of spreading the mounting screw pressure across the transistor. Also happens to give a tiny bit of heatsinking to the top side of the output transistors :)

 

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Although not needed, I've 'thermally coupled' the input jfets for fun. In this design they are acting as input buffers only.

 

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Amp module and heatsink assembly ready for assembly into a case.

 

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Back panel.

 

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Inside the floor of the case is a sub floor.

 

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Yeah this shall be a BIG amplifier. 5 Rack unit.

 

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EDIT 1. 2-6-2016

 

Front panel now has the power switch.

 

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Back panel, I wasn't happy with the speaker terminals being so damn close together.(Pre punched panel)

Quick chat with owner, New holes to move the outer terminals and we'll find some blanks to fill the holes.

 

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Just waiting for the transformer before I decide how to position the rectifier and filter boards. Then the wire up can commence..

 

Stay tuned...................

 

EDIT 2. 30-6-2016

 

Ya, Ve now have transfoomer frum Germaany. :D

Build can resume...

 

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Is Goot, Has nice solid plastic foot. Shall keep windings raised of floor for air flow and extra insulation.

 

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Ya, 500 of them VA's just for fun.

 

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Now I can haz sort out interior placement and stuff like. Filter board placed, drilled, screwed down. Transformer positioned, bolt hole drilled (need to get bolt).

Rectifiers positioned but I will make a little plate for them to sit on to make sure they get proper heat transfer to the bottom plate.

 

post-106429-0-35222400-1467260561_thumb.

 

Looking at the build of this transformer, I'm impressed. It's really bloody nice. 

It's a Sedlbauer 'Sealed' from it_tronics on ebay.

'Sealed' means it handles higher temps (60 ambient vs normal 40 ambient), has 1250 self resetting thermal breakers in the primaries, and has the potted core.

 

For $161 to my door from Germany in a week, well, You'd have to be nuttier than squirrel poo not to short list this beast.

 

 

EDIT 5-7-2016

 

So close I pulled several midnight shifts to get her done.

 

Time of birth 10 am 5-7-2016.

 

Actually It was fired up last night about 10pm, but first up was a slow variac rise for testing (no smoke:D ) 

But I did need to swap out one resistor on both boards to 'center' the dc offset.

Once that was done it was time to let it stablise, offset is now under 3mv.

Both channels are so close you'd think they were matched.

 

So far the massive heatsinks are doing their job very nicely. Just over luke warm so far.

 

Some final pics.

And No, I won't tell you what it sounds like. It's fresh and needs some serious break in. I'll let Paul give his impressions as he finds them.....

 

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Hi Nigel,

Could you share your BOM list used to build the M2? I need some help especially on the PSU parts. TIA.

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46 minutes ago, dewdrop said:

Hi Nigel,

Could you share your BOM list used to build the M2? I need some help especially on the PSU parts. TIA.

 

Here is the BOM 

But this is based on the design and boards supplied by Tea Bag 

Links available on his Group buy area along with build instructions 

 

 

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32F05CBA-910C-441C-BC9F-6A7BF428FA0F.png

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Thanks Nigel, I have downloaded the BOM list but I do not have the power supply cap details - hence I wanted to just get whatever you did. 

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7 hours ago, dewdrop said:

Thanks I have downloaded the BOM list but I do not have the power supply cap details - hence I wanted to just get whatever you did. 

 

The details are on the link I posted - you need to read the details a couple of times 

The BOM is located at the bottom 

 

But here is the link to the PSU section - 

http://www.diyaudio.com/archive/blogs/tea-bag/923-dual-rail-power-supply-power-amplifier.html

 

 

 

 

 

 

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Thanks Nigel. I read at the top of Teabag's blog that it is meant for F5T and F6 designs, means that the capacitance for the former is more. I know that I can always opt for the same for M2 but it will also mean my inrush current will increase and result in side effects.

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8 minutes ago, dewdrop said:

Thanks. I read at the top of Teabag's blog that it is meant for F5T and F6 designs, means that the capacitance for the former is more. I know that I can always opt for the same for M2 but it will also mean my inrush current will increase and result in side effects.

 

Note - I am not Nigel

I am the fellow builder and the owner of the amp 

We opted for larger 27000uF caps (as per photo) over the recommended 22000uF

 

I went through the BOM and discussed with Nigel the critical areas of the signal path and opted for specific changes in brand & materials of some components 

Using Harris/Vishay Transistors and Audio-note non magnetic resistors in R1,R2,R3,R4 

 

Paul 

7A628586-2824-4771-B6A7-22D8DC68032F.jpeg

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Apologies Paul! Thanks for the photos, much appreciated! I will love to put the AN tantalum resistors per your recommendation. 

Edited by dewdrop

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8 minutes ago, dewdrop said:

Apologies Paul! Thanks for the photos, much appreciated! I will love to put the AN tantalum resistors per your recommendation. 

 

Above all 

Make sure as it’s very critical the Jfets you purchase are matched pairs 

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Got it. I have bought some matched pairs for my F5T and B1 from a Singapore seller, so far so good.

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