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The diyAudio First Watt M2x
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Old 5th December 2018, 12:58 PM   #1081
Mark Johnson is online now Mark Johnson  United States
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The diyAudio First Watt M2x
Quote:
Originally Posted by xrk971 View Post
... Melbourne ... that comes from a single ended Class A front end ...
I think you need to adjust your marketing spiel. Your front end is a PNP differential amplifier, it's not single ended in the least. A single ended circuit is neither differential nor push-pull. Your front end does not meet the criteria.

However. Your second stage is indeed single ended Class A. Just like the second stage in every IC opamp including the uA741 from 1969. Just like the second stage in all of the beginner's power amps in Bob Cordell's book and Douglas Self's book and Ben Duncan's book and Randy Slone's book. (Before they begin to discuss push-pull second stages). But the second stage is not the front end and none of these amplifiers have a "single ended Class A front end".

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Old 5th December 2018, 01:06 PM   #1082
xrk971 is offline xrk971  United States
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Yes Mark, I know that the Long Neck Pair is not SE Class A , I mean the front end of M2X - since there are swappable “front ends”. But maybe you call them something else.
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Old 5th December 2018, 01:15 PM   #1083
Mark Johnson is online now Mark Johnson  United States
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The front end of M2x is whatever input circuit is included on the daughterboard you bolt in. So if you bolt in an Austin daughterboard, for example, then your M2x has got a push-pull Class A diamond buffer front end. If you plug in a Norwood daughterboard then your M2x has got a differential-JFET front end. And if you plug in a Melbourne daughter board then your M2x has got a differential-bipolar front end.

The only way to make your M2x amplifier have a single ended Class A front end, is to un-bolt the Melbourne daughter card and replace it with a different card whose input stage is indeed single ended Class A. If you do this then, yes indeed, a non-Melbourne M2x does exist whose front end is single ended Class A. But it misleads the reader to mention single ended Class A when discussing Melbourne itself.

"There is also an incredible smoothness that comes from a single ended Class A front end" -- on another card not named Melbourne.
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Old 6th December 2018, 12:48 AM   #1084
Sesquipedalio is offline Sesquipedalio
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Clarifying question here before I click purchase: The edcore part in BOM for M2X shows PC600-15K. The edcore site shows both 600 ohm to 15k ohm (1:5) and 15k ohm to 600 ohm (5:1). I assume that because the BOM has the 600 first I want 600 ohm to 15k ohm (1:5). But we all know Mr. Assumption...
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Old 6th December 2018, 01:07 AM   #1085
Mark Johnson is online now Mark Johnson  United States
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I think you had better read the

Official M2 schematic

thread here on diyAudio. It was started in 2015 by Nelson Pass, and to date it has accumulated more than 3170 posts. If there are pitfalls or difficulties or secret tricks to use when buying the Edcor transformer that Nelson Pass chose for the M2, that thread would be the first place, and the best place, to look.

Very closely study what went wrong when diyAudio member kbergsson tried to order Edcor transformers for shipment to Norway. Once you discover what he did wrong .... don't do that!

And continue with the remainder of anecdotes and tales of success / tales of woe, which fellow diyAudio members have posted. It would be a terrible shame to ignore their hard-won knowledge.
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Old 6th December 2018, 02:08 AM   #1086
JSA1971 is offline JSA1971  Canada
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Quote:
Originally Posted by Sesquipedalio View Post
Clarifying question here before I click purchase: The edcore part in BOM for M2X shows PC600-15K. The edcore site shows both 600 ohm to 15k ohm (1:5) and 15k ohm to 600 ohm (5:1). I assume that because the BOM has the 600 first I want 600 ohm to 15k ohm (1:5). But we all know Mr. Assumption...
Hi Sesquipedalio, The edcor transformer youíll need for each amp board is the PC Series Transformer, Impedance: 600 Ω to 15K Ω (1:5 ratio).
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Old 6th December 2018, 02:59 AM   #1087
Sesquipedalio is offline Sesquipedalio
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thanks Gentle ones
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Old 6th December 2018, 08:45 AM   #1088
MEPER is offline MEPER  Denmark
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About Edcor's I just got mine from Don-Audio which was ordered using the "DIYSTORE" code to get them a bit cheaper than normal price in Europe. Now this project can rest until I have built my preamps!
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Old 6th December 2018, 12:24 PM   #1089
Skylar88 is offline Skylar88  South Africa
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Finally, I managed to locate locally (South Africa), the only "do not substitute" item; the MV5075C red LED for the Mountain View daughter boards.

If any prospective M2x builders in South Africa read this and want some, just drop me a PM and I'll put you in contact with the supplier.
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Old 6th December 2018, 03:33 PM   #1090
nuconz is offline nuconz  United States
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Originally Posted by 6L6 View Post
Yep. I bummed a ride. I needed to go to SFO and get on an airliner home. Itís not that I didnít have the money for an Uber, but that I took the oportunity to have a 1/2 hour chat with Mark. You see, my entire point of going to Burning Amp is to actually see and talk to the people we interact with in the forums - this is a smart, fun, and neat group of people, and itís wonderful to actually see faces and chat during lunch while looking over the bay.

If you have the ability to go to Burning Amp Festival, I highly suggest you do! Itís great.

A few days later, I was on the phone talking about this project to Nelson, and he loved the idea. Super! Permission obtained, blessings received. (The M2 is his design, after allÖ)

Click the image to open in full size.


Click the image to open in full size.

Ishikawa - Want to build the ďoriginalĒ M2? Use this, and omit RV1 and jumper C1. Want to adjust your 2nd harmonic distortion? Install RV1 and get out the test software or hook it up to your distortion analyzer. Want to guarantee thereís no DC flowing through the auto dormer and saturating the core? Install C1.

Mountain View - This is the one that started the whole conversation. My memory is Mark saying, ďwhy donít I lay out a Firstwatt amp to use Fairchild Jfets?Ē Realizing that the M2 has no presence in the diyAudio Store and knowing that Linear Systems isnít able to provide many of the Toshiba replacement transistors anytime soon, this seemed like a simply wonderful idea! The daughter card feature was quickly thought of, and thatís what weíve got.


Tucson - Want to try different opamps? This is the board for you. Get a socket and some different single DIP-8 opamps. swap them in and out and see if you like one more than another. Remember to choose ones that are unity-gain stable. The addition of SMD pads allows for use of modern parts, as most of the made-specifically-for-audio new opamps are only available in SOIC-8 or other surface-mount parts.


Norwood - Honestly, this is the one that interests me the most, just to see what modern parts can really do. I was planning on trying this first, and made a silly mistake of mounting the active devices upside-down on the PCB, and totally gacking the board up when trying to remove my mistakes. Currently sitting hat in hand, waiting for a new PCBÖ

Never soldered surface-mount? Itís not that hard, and the parts used on this project are solderable by humans. Anyway, Iíll try to make a quick and easy video or something to show how easy it is.

Austin - BJT diamond buffer. This configuration is currently causing a lot of excitement in the DIY circles, there is a lot of people trying it in many different projects, and it's a great solution as well as wonderful sounding. More info in the link below

The diyAudio First Watt M2x - Page 2 - diyAudio


Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.



Now all this goings on about the differences input stage is quite possibly for nought, because in the M2 the voltage gain is provided by the autoformer - the active stage in front of it is merely a buffer, to make sure that the autoformer is driven by a well-behaved low-impedance signal. And the voltage gain in an amplifier gives much more impact to the sonics than a buffer

FIRST WATT M2

http://www.firstwatt.com/pdf/prod_m2_man.pdf

I'll add more photos and text to this soon, in the time being, here are some photos of my operative (and fantastic-sounding) amp:


Click the image to open in full size.

Click the image to open in full size.

TL;DR of this post - M2x. Sounds really fantastic. Build as originally designed AND/OR with different buffer stage. Daughter cards to swap front-ends.
wonderful effort - to make this amp so flexible. truly an inspired design!
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