A long time ago, a young designer (*) made a preamp with modules that sat above the main PCB and secured with bolts that also made the electrical connections as shown here -
An externally hosted image should be here but it was not working when we last tested it.
We figured that M3 hardware is common enough to find, sturdy, and if it was good enough for that guy working at Threshold way back when, it's a time-tested solution.
* Initials N.P.
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i have used the Panasonic resistors in my Pass clone amps but will try the 0.47 Ohm resistors, but the Xicon metal oxide resistors have somewhat lower ESL (for those worrying about performance above 1MHz).
If one tries this hardware it will sound significantly different... the sound of silence. 😎
Somebody was hearing rumors of fantastic sound from Soviet-era solid gold hardware. It was only made in M2.5, but it will still fit if carefully aligned.
Sonic Bliss! Better soundstage, bass slam, and that "you are there" feeling.
/sarcasm
Sonic Bliss! Better soundstage, bass slam, and that "you are there" feeling.
/sarcasm
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If there were a large number of signals communicating back and forth between the daughter board and the mother board, then a connector might have been more advantageous. But the M2x daughterboard has only four I/O terminals -- one fewer than the Threshold NS10 daughter board below. I happen to really like the solidity / ruggedness of bolts + star washers + threadlocker fluid / Loctite (or nail polish), especially when transporting the amplifier. So that's what I lobbied for and that's what we ended up using. Yep, it's a little different. Maybe that's a feature instead of a bug.
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Kudos to Mark Johnson and 6L6, for bringing a compelling (and beloved) design to the changing demands of techno reality. Soup to nuts... awesome.
Don't the bolts prevent 'live swapping' preventing true A/B testing?? 
Great idea - nice job. How hard would it be for someone to home etch a couple daughter cards if they want to try yet something else?
Great idea - nice job. How hard would it be for someone to home etch a couple daughter cards if they want to try yet something else?
Awesome, looking forward to seeing where this goes. To scale up the power with a balanced input would I be looking at the original Ishikawa input stage? I have F4 monoblocks on the midbass horns now, have always wanted to hear the M2.
A long time ago, a young designer (*) made a preamp with modules that sat above the main PCB and secured with bolts that also made the electrical connections as shown here -
We figured that M3 hardware is common enough to find, sturdy, and if it was good enough for that guy working at Threshold way back when, it's a time-tested solution.
* Initials N.P.
I wonder who is the young punk. ;-)
I bought 50 pieces of Panasonic 0R47 3W resistors back in January, and since then they have become Not Recommended for New Designs. If you look very VERY closely at 6L6's photographs of the amp main boards, you can see these. They are the blue resistors with the M-in-circle (Matsushita) logo of Panasonic, that I sent to him to assemble the Build Guide amplifier. I have found another vendor of 3W 0R47 resistors and listed it in the BOM. Luckily the inductance is not terribly important; remember that many not-designed-by-Nelson-Pass amplifiers have explicit series inductors in the output leg, with 100X greater inductance than a wirewound resistor.
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Can you remind me the power dissipation and tell me whether both boards could be put in the new ACA chassis? I rather like the smaller footprint.
cheers
Beardy
cheers
Beardy
Ah, I've heard from this guy!
As I was just curious about your decision I'd asked, because it was obvious for me that both of you have had seen other solutions as well.
Nice to see something different!
For me this means to hurry up getting all the amps build which are on my list, so I can hear the differences of the input stages for myself!
As I was just curious about your decision I'd asked, because it was obvious for me that both of you have had seen other solutions as well.
Nice to see something different!
For me this means to hurry up getting all the amps build which are on my list, so I can hear the differences of the input stages for myself!
Yes, that's right Mark and Jim.
Very nice that your put your heads together to pull out new possibilitys for us- greedies....
My interess was waked up for Mountain Viev- SE J112 + KSC3503 and OPA 604.
So i reed a bit "unity gain stable opamps".
Will interested follow only for now.
Regards.
Very nice that your put your heads together to pull out new possibilitys for us- greedies....
My interess was waked up for Mountain Viev- SE J112 + KSC3503 and OPA 604.
So i reed a bit "unity gain stable opamps".
Will interested follow only for now.
Regards.