Nelson Pass First Watt M2

[Full Range]

I popped in to Nigel's on the way to work this morning and had a look at the amplifier. It was not running at the time so I could drool over it without electrocuting myself. It's an excellent build and that is a fantastic enclosure. I'd be very interested to find out what it sounds like after it's been run in a bit.

 

Mark

Nigel normally runs my amp builds for a few days to make sure all the settings are correct and then puts them against his First Watt J2 and the other Pass Labs amps he has

So you have a small window of listening to it before it's collected

[Guest BobbyD]

Very nice build Nigel. I love the simplicity of design and layout and sure it will sound stunning as 25 W class A should.

 

Looking forward to Pauls feedback......

[Green Wagon]

Nigel normally runs my amp builds for a few days to make sure all the settings are correct and then puts them against his First Watt J2 and the other Pass Labs amps he has

So you have a small window of listening to it before it's collected

 

Yeah no.

To much to do currently sorry.

[Guest scumbag]

Nigel, you need to start doing crap work, that way people won't get you to do projects like this and your windows will be much bigger  I'm sure an opportunity will avail at some point in the future!

[Green Wagon]

More a combintaion of lots of stuff all hitting at the same time.

 

And I'm getting old

[Full Range]

A quick update on this amp build 

 

Due to the 104db sensitivity of my system, it was discovered that one of the components was making the M2 hum 

The iron PCB transformers are very sensitive and noted by Nelson Pass but that's what makes this amp special and gives it that unique sound signature 

 

After trying a variety of earth schemes as it's normally the cause in such matters, it was eventualy discovered that my toroidal was not a good match with this amp even though it was high quality audio grade 500VA 

 

I ordered a custom made Noratel 240V - 300VA - 2 X 18 V with a flux ring seal from the local Australian distributor RF Waves 

 

After a month it arrived from the Noratel Factory in Europe 

That was 2 days ago

Yesterday I fitted the new toroidal and after turn on - the hum was no more - gone in an instant 

Its now so quiet you would think the amp is not turned on 

 

So I will upload a few photos of the build for now,  showing a few changes and additions for now and after a week or so I will revisit and post a review 

 

Also warm thanks to @Green Wagon for all the help and guidance 

 

[acg]

Damn hum.

[Full Range]

4 minutes ago, acg said:

Damn hum.

 

In the end it was a simple swap over of a component that in itself is of a high quality build 

 

The test that proved it was the toroidal, was to remove the first toroidal and connect it up again 1 mt away with extended leads 

 

I have really learnt a lot during this process and my internal knowledge base is always hungry for more 

 

@acg When are you coming to visit me 

[Full Range]

Oh I forgot this photo where it shows the M2s place in relation with the other amps and components 

M2 is the one with the blue power indicator light in the centre 

Sorry you can't see the Nakamichi Control amp  

 

 

[Guest scumbag]

32 minutes ago, Full Range said:

Oh I forgot this photo where it shows the M2s place in relation with the other amps and components 

M2 is the one with the blue power indicator light in the centre 

Sorry you can't see the Nakamichi Control amp  

 

 

A thing of imposing beauty.

[acg]

2 hours ago, Full Range said:

 

In the end it was a simple swap over of a component that in itself is of a high quality build 

 

The test that proved it was the toroidal, was to remove the first toroidal and connect it up again 1 mt away with extended leads 

 

I have really learnt a lot during this process and my internal knowledge base is always hungry for more 

 

I fear that I will be chasing hum when I get my 6 channel amps built.  The power supply is in a separate chassis altogether and the chokes for the active crossovers will be encased in very thick steel so they don't pickup hum from the AC heaters/filaments.  Hopefully I will be able to sort it out easily enough if/when it happens...but I don't like any noise at all from my speakers.

 

2 hours ago, Full Range said:

 

@acg When are you coming to visit me 

 

To be honest, I am just putting all my spare (and some not so spare) time into getting my project done.  I really would like to come down the hill to meet you and have a listen to your horns...we will see...I just want to get some noise happening in my room first...maybe this winter I will get down to see you.

[Full Range]

@acg  I can help with a some very good, & some very demanding test tracks if you like 

Specifically chosen and compiled by me for horn systems  

[Full Range]

As promised I have come back to update the First Watt M2 Amplifier thread with a review

 

Components used in this test 
Pre - Nakamichi CA5 II
Source -

Cyrus CD8 SE

Garrard 401

Bluesound Node
Medium - CD , Record & Digital sources
Speakers - Klipsch La Scala ( Highly Modified ) 
Sensitivity min 104db 
Album - Pink Floyd - Dark Side Of The Moon

My brutal mixed track test CD

A variety of Records of all genres

Warmed the M2 up for about 1 hour

 

I have put the M2 through its paces sometimes returning to play again the same record or CD the next day for balance

 

The M2 is extremely precise, but with a presentation that is more reserved with sharp targeted control that has an emphasis on instrument separation and vocal areas of the recording.
In playback the M2's signature is warm at low to medium volume levels however its not holding anything back when the volume is increased. The M2 only gives the listener whats required from the recording to get the job done.

Its very analytical and has excellent 3D presentation in high sensitivity speakers
The M2 portrays the feeling and tempo of the music genre beautifully, by emphasizing a slightly more controlled and a warmer feel coupled with a wider presentation 

Extremely sharp on changing passages but with a little more warmth, prat is still there in abundance with enough volume

 

Treble -  Is very clean and clear with lots of hang time and controls the full spectrum until it trails off 
Midrange -  Is where the M2 shines and it shines on vocals and softer instrumental passages, beautiful separation but also precisely knitting together congested and melding sounds together
Bass - Abundant but with a little less thump than my F6 on the other hand the M2 has more control through the whole range

 

Summary

Warm without losing any prat with knife sharp instrument separation 

Good with all genres I listened to

Add volume and you would think a larger amp was driving this system

 

 

 

[tcressida]

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

[Guest scumbag]

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. 

[Full Range]

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 

 

[dewdrop]

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.

 

 

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

 

 

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

 

 

Boards for the actual Amp modules.

 

 

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

 

 

Underside, populated, cleaned, ready to go.

 

 

Top side.

 

 

Mounted onto the heatsinks.

 

 

Neat trick from a gent on diyaudio.

 

 

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

 

 

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

 

 

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

 

 

Back panel.

 

 

Inside the floor of the case is a sub floor.

 

 

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

 

 

 

 

 

EDIT 1. 2-6-2016

 

Front panel now has the power switch.

 

 

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.

 

 

 

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.

Build can resume...

 

 

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

 

 

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

 

 

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.

 

 

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.....

 

 

 

 

 

 

 

 

Hi Nigel,

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

[Full Range]

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 

 

 

[Full Range]

@dewdrop

 

For the M2 

BOM Link - https://docs.google.com/spreadsheets/d/1ZZavX5UjpKlB7kEhH9YMSXkL0s0l0HVg6NHbedx5RN8/htmlview

 

Thread link for the group buy and other relevant links to build Tea Bags design ect 

http://www.diyaudio.com/forums/group-buys/286699-gb-pass-m2-clone-boards-120mm-ums-spacing-tea-bag.html

 

 

[dewdrop]

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. 

[Full Range]

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

 

 

 

 

 

 

[dewdrop]

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.

[Full Range]

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 

[dewdrop]

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

Edited May 19, 2018 by dewdrop

[Full Range]

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