The diyAudio First Watt M2x

[Mark Johnson]

Have a look at listening reviews posted in this thread by other builders; quite a few people built several different M2x input stage daughter boards and found that they don't all sound alike. Predictably, there was a wide range of preferences when builders stated "input stage XXX sounded best to me, by far!". You'll have a lot of fun building a few different cards and listening to them, to discover which one(s) YOU like best. IPS7 might use the fewest out-of-stock components in today's environment so that could be a possibility, plus it gives you the experience of ordering PCBs yourself. Oh boy!

 

[Toadroller]

plus it gives you the experience of ordering PCBs yourself.

You know, it would be a great small project to take the schematic and do a layout myself and order (easyEDA or whichever tool). With your permission, of course. Or design my own buffer.

Many thanks to you and 6l6 for bringing this project to reality!

 

[Mark Johnson]

Sure go ahead but you don't need my permission to lay out a PCB from a public domain schematic. And you certainly don't need anybody's permission to design your own brand new unity gain buffer circuit, then lay it out to fit the M2x daughter card physical dimensions.

In case it might not be clear: IPS7 gerbers are attached to post #3408 of this thread. They can be downloaded for free, then ordered from whatever PCB house you choose. One way to choose a PCB house is to visit the website pcbshopper dot com and look around.

 

[6L6]

Also don’t forget to ask in the thread if anybody has IPS 7 boards on hand… the PCB minimum order amount virtually guarantees that you’ll have some excess.

 

[MEPER]

Can I ask a question regarding M2X and feedback?
There is a connection from output which goes back to in between D2 and D3?
What is the purpose of this connection if it is not a feedback loop?
If I go to FW homepage and read about M2X this connection is not in the principle M2X schematic.

 

[Mark Johnson]

It appears in Nelson Pass's Official M2 Schematic from seven years ago (see post #1 of that thread). Nelson created that topology, including the diodes connected to the amplifier output, and it's quite likely he felt there was a good reason to do it.

 

[MEPER]

The diodes are there to get symmetrical clipping (have never tested if it works). Then I assume that the "feedback" connection from output to in between D2 and D3 is part of that "symmetrical clipping" circuit.

 

[Mark Johnson]

A very similar looking circuit, with very similar diode connections, also appears in Nelson's AB100 amplifier. The amplifier output terminal is directly connected to D3-D2-D1, and also is directly connected to D4-D5-D6. The AB100 diodes even "point" in the same direction as the M2 diodes.

 

[MEPER]

But the 3 + 3 diodes in each half looks more "symmetric" than in M2 circuit.
In AB100 3 x 1N4001 and 3 x 1N4004 are used to create the "asymmetri" needed to get "symmetric" clipping?
I guess they have a bit different voltage drop. If not I need to think more about it.......

 

[namghiwook]

Are 150*75*150 size heatsink 4pcs good enough for M2X?

https://www.aliexpress.com/item/100...da9!12000027137837640!im&gatewayAdapt=glo2kor

 

[6L6]

Yes.

 

[topicreader]

Hello!
I have 2 Question:
1. I have almost all parts to M2X amp and Norwood daughterboard except the transformers (mono block). I want to order them now.
The rail of transformer as I saw 2x18V AC. The manufacture of transformator ask me that the 2x18V AC is loaded or unloaded voltage?

2. The rail after graetz is approximately 24VDC without loaded.
Op.amp of Noorwood are HA5002 and AD744. Maximum supply of HA5002 is 44V (+/-22) AD744 is +/-18V (from the datasheet).
Something I misunderstand or the op.amps are tolerate the overvoltage?
Thank you

 

[6L6]

Take a look at the parts SMA5927 in the circuit. 🙂

https://www.mouser.com/datasheet/2/308/1SMA5913BT3_D-1101349.pdf

 

[topicreader]

Take a look at the parts SMA5927 in the circuit. 🙂

https://www.mouser.com/datasheet/2/308/1SMA5913BT3_D-1101349.pdf

Thank you, I was blind, so it works from +/-12V.😀.
I chose only this daughter card, because Mark wrote that is his favourite, what is your favourite?
And 2x18V loaded or unloaded?
Gy.

 

[6L6]

They are all very good, but my favorite is unquestionably Norwood.

😎

Yes, get a 2x18VAC transformer. (Loaded) That will rectify to approx +/-24VDC

 

[Mark Johnson]

Mark's favorite is, obviously: The Next One. When it will appear, nobody knows, certainly not me.

Your favorite need not be the same as anyone else's.

 

[henryyyy]

Hi,

I just finished assembly but have a problem. The power board holds at about 24.5V when not connected to the M2X boards. But when I connect either or both M2X boards the voltage starts dropping after about 20 seconds. Does anyone have advice on trouble shooting?

Thanks!

Henry

 

[6L6]

What is the voltage dropping to? The 20sec delay is about the time the bias circuit takes to charge up, so things may be operating normally…

 

[henryyyy]

It drops to about 12V after 30 seconds. At that point I turned it off - afraid that I might fry something.

 

[6L6]

That’s a big drop. Bias pot may be set way too high.

Also double check that you have the 240 and 9240 in the proper locations.