The diyAudio First Watt M2x

Jump to Latest
#6,484
Yes the M2(x) is special for the reasons Adam has mentioned.

But what ties it all together in the end, is this which Nelson invented ~35 years ago while at Threshold. Understanding this gives credence to all that is M2 and associated with M2 (and others with follower output stages). This includes all the applications of such by ZenMod and his designs:

https://patentimages.storage.googleapis.com/5a/4f/48/558eaf6b4c903c/US4752745.pdf

There is lots to learn with the M2 and it’s variants. Have fun!

Best,
Anand.
 
Last edited:
#6,485
jimk04, I've built the Aleph-J, F6, F2J, and M2x. They're all fantastic amplifiers. Some day, I hope to find a great speaker for the Aleph-J. The M2x is my favorite one to drive a pair of B&W 805D3's. I haven't tried all the input cards yet. I use the B1K (from DIYAudio kit) as a pre. This combination is just a tad warm sounding, and provides excellent differentiation of instruments, depth, and clarity.

I also love the F2J with a pair of Abby speakers; but that's a whole other ball of wax.

If you build the M2x, there's a ton of info here to help guide you. I had issues with noise from the power transformer and resorted to converting to dual-mono with external power. This delivered a slight improvement with bottom end transients, too. Others have solutions using mu metal. Some experience no issue at all.

The only reason it's not the last amp I'll build is that I can't suppress the urge.
 
#6,488
poseidonsvoice said:
... what ties it all together in the end, is this which Nelson invented ~35 years ago while at Threshold {US Patent 4,752,745}
Click to expand...

To be fair, Douglas Self published a similar but non-infringing autobias design in May 1995, within his Trimodal Amplifier project. Self's circuit eliminates the huge variability of optoisolator Vfwd and Current Transfer Ratio, however it does occupy more area on the PCB.

(notice that he drew TR8 incorrectly! Oh Doug...)

_
 

Attachments

  • trimodal.png
    trimodal.png
    47.3 KB · Views: 175
Last edited:
  • Like
Reactions: poseidonsvoice and Holzarbeiter
#6,489
Eslheadphone said:
I started building amps many years ago and have gone through a lot of amps. Starting with tube amps and switching to transistor amps , not being satisfied with transistor class AB , went back to tubes. I wasn't until I built a Firstwatt F5 I was satisfied. My next Firstwatt build was the Aleph J. The J has a more relaxed sound and in my opinion more musical ( at least in my system ). My most recent build is the M2X with the Ishikawa input stage. I bought the parts for the Mountain View minus the LEDs. I just can't bring myself to taking this amp out of service long enough to change the input board. I absolutely love this amp. It sounds like music. The top end doesn't have that hifi sizzle ( I cant stand that ) . It just sounds natural. Nelson has done it once again. Can't thank Nelson and the DIY community enough.
Click to expand...
@Eslheadphone - my amp progression is similar to yours: tube, ACA stereo then dual mono, now Aleph J. Just ordered M2x boards and bits, Ishikawa will be first up with Toshiba Jfets. Question: what are the boards residing between your power supplies and amp boards? Thanks in advance! Jim

https://www.diyaudio.com/community/attachments/20210401_132530-jpg.942485/
 
#6,490
Good info all thankyou. I currently am building the 6-24 xo and so my obvious intention to biamp leads me to wondering which amp to use for what. And I also have DCG3, Wayne's line stage and also Doug self pre amps to play with.
My Aleph with 300x160x 64 sinks gets pretty toasty. The dissipation of M2X maybe a bit lower and save me a bit of heat.
Shame about the availability of that pesky LED for Mountain View !

I'm tempted to jerry rig in some 'chineseum' 600:15k signal trafos I have that used in a DAC build . Just for laughs to see .
 
#6,497
Ahem. Some people may not automatically and reflexively read post #1 of a thread when they have a concern or a doubt about part numbers, substitutions, alternate sources, and so on. Let me quote post #1 of this thread, the one you're reading now, and underline a section which might be useful in today's context. Feel free to double check post #1 yourself to verify that this is an actual quotation and not some kind of malarkey shenanigans, fabricated by me to deceive or mislead members.

Mark Johnson said:
...
MOUNTAIN_VIEW uses single-ended, class A, discrete circuitry and no feedback. If you are a big believer in single ended class A, if you love this quote from a famous article by Nelson Pass: "For reproducing music as naturally as possible, push-pull operation is not the best approach. Air is not symmetric and does not have a push-pull characteristic. ... Only one linear circuit topology delivers the appropriate characteristic, and that is the single-ended amplifier. Single ended amplification only comes in pure class A," then you probably are interested in listening to the Mountain View input stage. Parts note: please see post #3318 in this thread if you're having trouble finding a few MV5075C LED parts. That post suggests alternatives.
...
Click to expand...
 
  • Thank You
  • Like
Reactions: jimk04, Holzarbeiter and ItsAllInMyHead
#6,499
JKiriakis said:
@Eslheadphone - my amp progression is similar to yours: tube, ACA stereo then dual mono, now Aleph J. Just ordered M2x boards and bits, Ishikawa will be first up with Toshiba Jfets. Question: what are the boards residing between your power supplies and amp boards? Thanks in advance! Jim

https://www.diyaudio.com/community/attachments/20210401_132530-jpg.942485/
Click to expand...
One board is the soft start and the other is the speaker protector, both available from the diy store. Those monster relays are part of the speaker protector. Tyco prd-11dy0-24. The relays came from allelectronics.com who unfortunately announced a going out of business sale. I will miss them.
 
  • Like
Reactions: JKiriakis
#6,500
An eagle-eyed builder has spotted two mistakes in the Detailed Parts List (.xls file) for the new Milpitas / IPS9 daughter card.

1. The smaller electrolytic capacitor's part number was wrong! The correct part is shown in the photo below. 47uF / 35V / 6.3mm case diameter / Mouser 710-860080573003 . See whether you can decode the purchase order number

2. The optional-and-I-hope-you-don't-use-it DIP8 socket part number was severely incorrect. One of the appropriate Mouser parts is number 437-1108730841001101 although you could buy a bag of 50 or 100 milled-pin DIP8 sockets on eBay or Amazon for not much money at all. Mouser's sales page for the above part, has unfortunately attached an incorrect photo but if you click on the Datasheet link you'll see the socket itself is correct.

Here are some nice gold DIP-8 sockets for $0.25 each (ebay link) -- if you trust eBay

Sorry for the errors! --MJ

_
 

Attachments

  • bagcaps.jpg
    bagcaps.jpg
    373.7 KB · Views: 109
Last edited:
  • Like
Reactions: bullittstang
You must log in or register to reply here.
Top Bottom