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Green Wagon

Nelson Pass First Watt M2

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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.

 

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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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Edited by Green Wagon

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Wow, how much output does this amp have?   But nice to see the pics and is this an upgrade or a new amp build, thanks :)

Edited by Ping

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Wow, how much output does this amp have?   But nice to see the pics and is this an upgrade or a new amp build, thanks :)

 

Most of Pass designs run at low voltage pure class A. This amplifier is rated at about 25 watt per channel. Don't be fooled by the enclosure size for a measly 25wpc, due to its nature of being a pure class A it puts off a stinking amount of heat so they need to be 'ventilated' with an appropriately sized case.

 

Btw what is the heatsink size with the L support brackets across them? Looks like a modushop case.

Edited by liteneasy

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Yup.

EDIT -> Some of Nelsons First watt designs are 25w class A. Some will double with lower impedance loads, some don't.

Method behind that idea. When a different design comes along, you can reuse the case and power supply. Just build and install the amp modules.

 

This is a full on ground up new build. The previous f5/f6 was limited by a case with heatsinks that were not really able to handle proper biasing.

 

As a Pass design, it may be 'only' 25wrms/8, but it will draw 200w from the mains.

 

Yes, case is a 5ru deluxe through diyaudio, which is a hifi2000 / modu case from italy. http://diyaudiostore.com/collections/deluxe/products/deluxe-5u-ultimate-amplifier-chassis

Heat sinks are quoted as - Two 40mm thick x 200mm deep, wave profile, black anodized aluminum heatsinks per side and about 200 high.

So each side is roughly 200x400x40.

 

EDIT - As Dave says below, I goofed, not all his designs are 25w. 

Edited by Green Wagon

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200w, really for 25W RMS, but it must be worth the effort... all good :)   

 

Be interesting to see pics of the final build ... thanks :)

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Those heat sinks are bloody huge!

 

Very neat work Green Wagon.

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Yup. 200w in equals 2x25w out.True class A. Very wasteful. Very nice to listen too.

 

His (Pauls) previous Pass amps (Pauls original case) were very undersized in heatsinking. If I'd set the bias to the right level, you'd burn your hands within seconds and the outputs would have a very short life.

 

Transformer will be 500va with twin secondaries and a belly band.

 

Yep Biiiig heatsinks. But their not very deep, so need to be enlarged in other areas to get the thermal dissipation.

Each side is made of 2 heatsinks, and totals 40mm thick, 208mm high, and 400mm deep. (just measured them)

 

Always have to allow for brisbane summers.

 

And thank you.

I'm approaching this build more and more as if it was mine.

Who knows, maybe it will never leave the house :D

Edited by Green Wagon

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All Hail Pappa ....  for designing amplifiers which cover the whole range of needs.

 

 

Options with low gain, no feedback and/or low output impedance.    :party  :love

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I am putting my hand up to say that this is my amp & Nigel is building for me

Just to much ( normal work ) on at present to do any DIY myself

Looking good so far Nigel

All parts were well chosen for ease and assembly - The 5U chassis is the Deluxe model that has everything pre-drilled and tapped and has the best air circulation when used with the perforated sub floor panel

All components were chosen for sonic abilities and or the highest grade available from all the different brands used & A class matched Jfets

As you have seen in the photos I elected to have an illuminated switch on the front panel, because it's very difficult to reach the rear panel switch

I will keep an eye out as the build progresses and will update on the speaker thread my impressions

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The 2 watt non magnetics sound considerably better than the 1 watt versions and the 2 watt silver versions remarkably better again. Good luck with your build as it should sound sweet.

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The 2 watt non magnetics sound considerably better than the 1 watt versions and the 2 watt silver versions remarkably better again. Good luck with your build as it should sound sweet.

If you have any AN Silver resistors of the values in the photo, that you have used as testers ( used ) and lying about feel free to PM me so I can exchange some cash for them and I can evaluate what's best for this amp build

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If you have any AN Silver resistors of the values in the photo, that you have used as testers ( used ) and lying about feel free to PM me so I can exchange some cash for them and I can evaluate what's best for this amp build

Sorry, only new and the ones I brought in for testing replaced 2 watt non magnetics. They are crazy expensive and crazy good.

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Sorry, only new and the ones I brought in for testing replaced 2 watt non magnetics. They are crazy expensive and crazy good.

On the last build (F6 amp ) I used Charcroft Z foils - and they are superb

Decided on a change for the M2 amp build in keeping with its tube signature credentials

When choosing I weighed up both Audio Note Silver or Audio Note Non Magnetic but chose the Non Magnetic because of the area it's in on the PCB

Price was a medium issue for me - but it's good to know your first hand impressions

Thanks for any more info you may share in advance

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The body of the silver resistor is the same as the non magnetic but with solid silver end caps with a small percentage of germanium to give a spring function to the end caps maintaining tension and solid silver legs. Have a look at the posts I put up in the DIY what are you building thread. If you come to Melbourne in October you can hear a full silver resistor system.

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The body of the silver resistor is the same as the non magnetic but with solid silver end caps with a small percentage of germanium to give a spring function to the end caps maintaining tension and solid silver legs. Have a look at the posts I put up in the DIY what are you building thread. If you come to Melbourne in October you can hear a full silver resistor system.

Audio Note Silver resistors is an upgrade path that I had thought of should the Non Magnetics not gel in there synergy with the M2 Design

Even the Tantilum NM is an upgrade to the standard

Will see how the M2 performs and take it from there

Just waiting for the custom Harbuch Toroidal to be manufactured - taking a while as its been about 4 weeks

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Audio Note Silver resistors is an upgrade path that I had thought of should the Non Magnetics not gel in there synergy with the M2 Design

Even the Tantilum NM is an upgrade to the standard

Will see how the M2 performs and take it from there

Just waiting for the custom Harbuch Toroidal to be manufactured - taking a while as its been about 4 weeks

The NM's will sound very good in there without a doubt and you should be very happy. The silver version is only for the obsessive and financially non restrained or at least that's what I keep telling myself. They were the single biggest sound change I have made with any component substitution.

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The NM's will sound very good in there without a doubt and you should be very happy. The silver version is only for the obsessive and financially non restrained or at least that's what I keep telling myself. They were the single biggest sound change I have made with any component substitution.

When I was building the crossovers I used Duelund resistors

That was a revelation - and based on that experience I chose components carefully for the amp build

Another reason I chose Audio Note is that they will be around a while - as many other brands have stopped production

One never knows Audio Note may release another top quality resistor sometime in the future and give me another upgrade path

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When I was building the crossovers I used Duelund resistors

That was a revelation - and based on that experience I chose components carefully for the amp build

Another reason I chose Audio Note is that they will be around a while - as many other brands have stopped production

One never knows Audio Note may release another top quality resistor sometime in the future and give me another upgrade path

I first heard of the prototype 4 years ago so I wouldn't be holding out in the short term. All resources at the moment are going into full finished product, not componentry other than the blackgate replacement capacitors. Cheers.

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Transformer was ordered on the 28th of april.

 

"Yes that'll be done this week" x4

 

Companies winge about lack of business, yet don't deliver on their word when they have an order.

Nope. I don't see any correlation there at all.

 

I have another lead so I'll check with that company on monday.

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A quick update

We are still waiting for the Toroidal transformer from Harbuch

It's lucky that work has kept me busy to get to worried - but now after several weeks delay I'm getting a little frustrated

I'm wondering if any other equal or better quality AU manufacturers of Toroidal transformers to source / look at as an alternative ?

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A quick update

We are still waiting for the Toroidal transformer from Harbuch

It's lucky that work has kept me busy to get to worried - but now after several weeks delay I'm getting a little frustrated

I'm wondering if any other equal or better quality AU manufacturers of Toroidal transformers to source / look at as an alternative ?

Unfortunately it's par for the course with his transformers - a bit loose in terms of project management - they are great though and I have them in most of my amps. I used to use nuvotem but once I started using Harbuchs stuck with them. I don't have a recommendation for alternatives - tortech maybe?

Sent from my iPhone using Tapatalk

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Unfortunately it's par for the course with his transformers - a bit loose in terms of project management - they are great though and I have them in most of my amps. I used to use nuvotem but once I started using Harbuchs stuck with them. I don't have a recommendation for alternatives - tortech maybe?

Sent from my iPhone using Tapatalk

Thanks for you input AJ

One reason we chose Harbuch is that they have a high quality build product - and to me that's worth more that a few dollars extra

Even more important in this A class amp build - so a little extra time to manufacture was factored

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Speaking of parts, has anyone noticed when using rs and ordering a few small things, they seem to get spread over a multitude of small deliveries. The pickers must have sense of humours as I received 5 x 1/4 watt resistors (1 tiny packet) delivered in a large box with a ton of foam dog biscuits to protect them.

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Speaking of parts, has anyone noticed when using rs and ordering a few small things, they seem to get spread over a multitude of small deliveries. The pickers must have sense of humours as I received 5 x 1/4 watt resistors (1 tiny packet) delivered in a large box with a ton of foam dog biscuits to protect them.

 

E14 do the same thing.  No local stock is the problem so they get stuff in from US/UK/wherever to make the order but get a few bits out to you to keep you happy.  Mouser and Digikey don't do this...they keep stock (admittedly in the US) and it all comes in the one box.  One of the shitty things about being in a small country/market.  Mouser by DHL is in my hands same week, and they are usually cheaper than local for the stuff I buy, except for the big high voltage electros where Digikey are hard to beat.

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