The diyAudio First Watt M2x

Keep it simple and reduce the number of possibilities... First thing I would do is shut it down and pull the speaker input to the DC board and test from there and see if the 250Hz is still there and at the same level. If it's unchanged you have ruled out anything from the DC boards and can move on to the next thing.

Short the inputs and test, un-short and test changes?
I did everything you mentioned.No changes in 250Hz. Still at - 85dB. Of course it was measured only by the application on the phone but my ears can hear the noise.
May be the problem is with edcor and needs to be shielding as mentioned by Avitkauskas. The power transformer is already in the steel casing.
 
Both of those brands of opAmp fit the IPS7 boards without any modification?
Looks like it would be tight


Yes, the Staccato fits, I listened to the Sparkos on a friends system, so I don't know about that one. The Staccoto needs to be the single, the double won't work. The Burson needs to be cut out of it's little case to make it fit.

The bummer is, I didn't think about these tall boys when I designed the amp. I need to lower my M2X boards, or cut a hole, or run with tops off. The are 1/8 to high to put the covers on. I'm actually leaning toward some kind of access panel, so I can swap boards and chips without taking the cover off. It's doable with my setup.

One thing I noticed is the retention of the Staccato is a little weak. If I leave them in, I'm going to get a couple dabs of hot glue, or like to make sure they don't move.
 
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Exactly. I'll check Mountain View cards tomorrow and next mount it to amp. I'll see the noises

No need to try other cards, it doesn't hurt, but if it's the same on both chances are ground issues or Edcore. The power supply is clean right? You don't see anything funky on the supply output?


I've been lucky, or good on my design as none of my 3 MX2 builds has ever had a whisper of hum... :whazzat:

I read where lots of people had issues, so I tried my best in placement. I even have an MX@ running mono config with flying leads and no problems. 😛
 
Well ya, 2 of those views show around 17mVpp which it okay, but one shows 170mVpp which is way more than I see on mine, by a factor of about 10, so which is it now? Is it 17-18mVpp or 170-189Vpp?

If it's a 100hz then it's unlikely the issue behind your 250hz issue, but it's good to know what the PS ripple/noise is.

From what I see you have a ground or Edcore issue, show us the the supply wave and output waves under load.
 
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It was 170mV. 17mV was at probe x10.
As Jeff wrote, 170mV is a good value and if he says so, I believe him.
"Supply wave and output waves " - Please give me more information what you mean.
The photo from the oscilloscope with a visible wave of 170mV is from the power supply output under load