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The diyAudio First Watt M2x
The diyAudio First Watt M2x
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Old 14th April 2019, 09:29 PM   #1691
JSA1971 is offline JSA1971  Canada
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The diyAudio First Watt M2x
Quote:
Originally Posted by 6L6 View Post
For what it's worth, the NuTube B1 isn't really a tube circuit for this conversation, as it has a fet buffer on the output, and can easily drive any reasonable load it may be connected to.
Thanks for pointing that out Jim, greatly appreciated!
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Old 16th April 2019, 09:55 AM   #1692
meanie is offline meanie  Singapore
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Click the image to open in full size.
Click the image to open in full size.

Freshly built, but still trying to rid off the elusive humming on both channels.
I decide to move the left channel away from the PS unit, true enough the hum reduced, then i experiment by placing a iron chassis in between, and trial by turning the heatsink at an angle to the PS unit. And the hum went completely away, dead silent on left channel. So i can conclude there was no ground looping in my case, except radiation from the tranny.

I may consider caging both channels like a Faraday cage when i house it into a proper chassis then, or follow the MuMetal tape method.

Just sharing...
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Old 16th April 2019, 10:39 AM   #1693
MEPER is online now MEPER  Denmark
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I wonder if the relative high noise figure for the original M2 specified at Firstwatt (500 uV) is caused by noise pickup of the Edcor?
Would it be possible to reach 100 uV by take care of PSU and screen the Edcor?
Has somebody measured noise on the M2X?
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Old 16th April 2019, 11:23 AM   #1694
WKCox is offline WKCox  United States
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The diyAudio First Watt M2x
All builds will likely measure differently, but I was able to reduce hum from ~500uV to ~200uV by shielding the Edcor with MuMetal.
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Old 16th April 2019, 11:48 AM   #1695
chede is offline chede  Germany
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The diyAudio First Watt M2x
I have one channel below 100 uV, the other 100-200 uV on my M2 (not X), built on JPS64's boards. Measured with two of my DMMs set to mV AC.

Needed a copper belly band (The diyAudio First Watt M2x), a sheet metal case for the Edcor (Teko 3710, The diyAudio First Watt M2x), and some magnetic steel partition between transformer and PSU / amp boards. I also have a CLC PSU with a Hammond 159ZL choke (2.5 mH, 10A, 44 mOhm).
The diyAudio First Watt M2x

So ... yes, it is possible

Best regards, Claas
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Old 16th April 2019, 12:11 PM   #1696
chede is offline chede  Germany
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The diyAudio First Watt M2x
One addition:

My SissySIT, which uses Cinemag CMOQ-4HPCs, is totally silent over my 100dB/W sensitive widebander speakers.
In that build, I also have used chokes in a CLC PSU, but the smaller Hammond 156B.
There is only a belly band on the Cinemags; no steel or mu-metal cover. On the other hand, according to Zen Mod and others, high-nickel transfomers are less sensitive to hum pickup than those with ordinary steel laminations.

Babelfish M25, SissySIT - general building tips and tricks


Best regards,
Claas
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Old 16th April 2019, 12:39 PM   #1697
Mark Johnson is offline Mark Johnson  United States
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CLC, CRC, Capacitance Multiplier are delightful ideas which reduce supply voltage ripple nicely. But they do not reduce hum in an M2 or M2x. Hum in these amplifiers arises from electromagnetic coupling between the AC mains power transformer on the chassis floor, and the two Edcor transformers on the two amplifier PCBs. Hum reduction in these amplifiers comes from screening the mains transformer, shielding the mains transformer, boxing the mains transformer, moving (e.g. rotating) the mains transformer, screening the Edcor transformers, and boxing the Edcor transformers. Not from ripple reduction.
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Old 16th April 2019, 02:18 PM   #1698
chede is offline chede  Germany
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The diyAudio First Watt M2x
Thanks Mark, and I'm with you on that . Might not have been very clear as to my intentions.

That the mains transfomer is the primary agent in induced hum has been exactly my experience in experimenting with rotating or shielding the mains transformer, or shielding the signal transfomers on the amp boards.

I did mention the chokes not because I think they have been reasons for less hum, but because I had been suspecting that they might add to the hum because of their own radiated magnetic fields ... but in fact, as written in the referenced post, I could detect little difference when holding a magnetic steel sheet between choke and Edcor in my M2

Best regards,
Claas
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Old Yesterday, 01:57 AM   #1699
garyalex is offline garyalex
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Quote:
Originally Posted by cubicincher View Post
O.K.! Sounds good.


Have a good week and hopefully your M2X will give you the same listening pleasure as my one!


Greets
Dirk
Thanks to Jim's stellar help I now have a working M2X. My only previous experience with Nelson's First Watt amps was the ACA. As amazed as I was with the sound quality of that amp, the M2X is in another league. I've had amps that cost a lot more, but I've never had one that sounds as good as the M2X. I'm using the Tucson board and will also try, at minimum, the Mountain View. I'm using it with a preamp I've had forever, the Cary SLP-98P.

Jim, Mark - thanks again for your help, and for making this remarkable amplifier available.
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Old Yesterday, 02:26 AM   #1700
6L6 is offline 6L6  United States
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The diyAudio First Watt M2x
Fantastic news!!!! Told ya that a Firstwatt is in another universe from the (excellent) ACA.

So glad you like it, but it’s a very easy amp to like!
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