Official M2 schematic

Member
Joined 2002
Paid Member
I'm collecting parts together to build an M2. I already have a B1 buffer but I am wondering - is unity voltage gain is enough for the M2? I should think it's ok right?

Cheers

My room is small so I don't think I use too much power. I used a
cd player directly into the M2. Variable volume control was used
on the cd player. For me, it was loud enough. The max output
of the cd player was around 2V RMS.

Dennis
 
Dear all;

I have put together a Mouser BOM, and exported it to a google spread sheet.

It can be found here:

https://docs.google.com/spreadsheets/d/1iR01w9395KnLCubzezIL6BdYyVRI1vBBPMfFm71SDy8/edit?usp=sharing

A few comments:
All resistors 1/4 Watt, except where noted.
Had to guess on voltage of the Caps, feel free to comment, and I will change as needed
Not sure on the Pot, so used the same one as suggested for F5

Only order one set of IRFP as matching is not REQUIRED ( I think ) again, feel free to comment.

Dave
 
Regarding the MOSFETS, there is no matching between N and P devices, but pay attention to what Nelson said earlier in this thread.

...This used the Fairchild output devices and pot location assumes that P channel Vgs is slightly higher than N. You can use other devices...
:cool:

If the Vgs difference between the devices in a given channel is larger than between typical Fairchild ones, you may have to tweak the effective value of the trimmer to be able to set the output offset to 0.
 
Member
Joined 2010
Paid Member
Hello to our US based friends! I've a request for help if anyone is inclined to do so. With a GB on PCB's done there's obviously a few of us who'll be chasing the edcor transfo's. Whilst very reasonably priced the shipping costs are ...exciting!

Anyone know of any alternate ways of sending transformers from the US to Australia?
 
Hello to our US based friends! I've a request for help if anyone is inclined to do so. With a GB on PCB's done there's obviously a few of us who'll be chasing the edcor transfo's. Whilst very reasonably priced the shipping costs are ...exciting!

Anyone know of any alternate ways of sending transformers from the US to Australia?
Could possibly do a group buy if there is enough interest.
 
Got a few minutes in before starting the day job.

BOM edited as per comments

R5 added, Caps Changed, pot changed.

Link to Mouser here:
Project & Cart Sharing | Mouser
Access ID: e2fb9dfa77

When I get some off the clock time I will update the Google sheet as well Just in case you are not a Mouster Fan

Dave

Thanks for doing this!

I did have a problem with the access id as it said project not found.

Never mind I missed a number.
 
Last edited:
Member
Joined 2012
Paid Member
M2 frontend is sounding Mega Giga Super nice, as frontend for a headphone amp :)
I combined it with the upcoming DIY Headphone amp output stage and it's a keeper...
So I made a quick PCB, found some old Teko TK3710 RF-cases for shielding the Edcor's and the M2 Headphone amp is born :D

Strange....I always hated the combination of transformers and audio...but I was so wrong... CSX1, F6 and now M2 they all sound so nice.

Makes me wonder how the M2 sounds on my big loudspeakers... :eek:
 

Attachments

  • IMG_5884ww.jpg
    IMG_5884ww.jpg
    268.1 KB · Views: 1,027
  • IMG_5893ww.jpg
    IMG_5893ww.jpg
    429.7 KB · Views: 1,016
  • IMG_5895ww.jpg
    IMG_5895ww.jpg
    329.6 KB · Views: 994
  • IMG_5896ww.jpg
    IMG_5896ww.jpg
    458.6 KB · Views: 982
  • IMG_5900ww.jpg
    IMG_5900ww.jpg
    315.9 KB · Views: 977
  • M2-HPA-ww.jpg
    M2-HPA-ww.jpg
    120 KB · Views: 2,580
One more thing...

Regarding the BOM, I added a resistor and a 5 mm LED to the schematic used to create the boards. Those two components are optional but I thought some people might want to install them. The resistor's designation is R15 and the value used in other published First Watt schematics is 10K.
 
Regarding the MOSFETS, there is no matching between N and P devices, but pay attention to what Nelson said earlier in this thread.


If the Vgs difference between the devices in a given channel is larger than between typical Fairchild ones, you may have to tweak the effective value of the trimmer to be able to set the output offset to 0.

[from zen Mod]
or value of resistor in series with pot

If I could get some input on these values, it would help me greatly. Unlike some DIY folks, I do not have a "parts bin" So, the marginal cost of a few resistors and a different value pst is often a week in lost time, and 10 times the value of the parts in shipping!

The answers are certainly in the F5 thread, and in fact, I remember scanning them, finding them is another matter :whacko:

Thanks for the help

Dave