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Old 28th January 2013, 04:16 PM   #1311
hesener is offline hesener  Germany
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sorry, forgot to take that scope shot. But the output voltage was fluctuating +/-100mV with frequencies below 1Hz, and when I blew on the input stage transistors the voltage was moving quite a bit.... On my well-run-in Paradise those fluctuations were much smaller.
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Old 28th January 2013, 05:11 PM   #1312
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Thanks. I was more curious if the scope showed any noticeable hf. Mine has a couple of mV @2MHz.
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Old 28th January 2013, 05:58 PM   #1313
hesener is offline hesener  Germany
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no high frequency there. I remember though that when I was measuring in our lab, there were traces of other stuff (22kHz from a fluorescent lamp, 65kHz from power supplies etc etc) visible. The lab I have at work certainly is not the most quiet place, and this amplifier requires shielding to excel ....
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Old 28th January 2013, 06:44 PM   #1314
FdW is offline FdW  Netherlands
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Here Paradise Builders you can see some 600~700uVpp (I would guess near 200uVrms) noise embedded in sampling artifacts of the scope. IMHO this noise is all/most due to fact that the PSU is operating unshielded. This all is at the measuring limit of the scope.
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Old 28th January 2013, 07:22 PM   #1315
Salas is offline Salas  Greece
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Noise is random not sinusoidal. Its either something produced in the circuit or in the environment picked up by it and/or the measurement loop.
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Old 28th January 2013, 07:28 PM   #1316
FdW is offline FdW  Netherlands
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Quote:
Originally Posted by Salas View Post
Noise is random not sinusoidal. Its either something produced in the circuit or in the environment picked up by it and/or the measurement loop.
Quote:
Originally Posted by FdW View Post
Here Paradise Builders you can see some 600~700uVpp (I would guess near 200uVrms) noise embedded in sampling artifacts of the scope. IMHO this noise is all/most due to fact that the PSU is operating unshielded. This all is at the measuring limit of the scope.
The sinusoidal signal is 5nS and is the scopes sampler triggering on the noise, you can filter this out, but then the signal is even more hidden. When you remove this sinusoidal (using imagination or Photoshop ) from the shown signal part then to will be left with about 700uVpp of random noise.

The main problem here (if it where a problem) is that the scope is on/over it's practical limit, and it is the best one (scope) that I have

One other 'problem' is me getting acquainted with the scope (more learning to do).

Last edited by FdW; 28th January 2013 at 07:49 PM.
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Old 29th January 2013, 01:19 AM   #1317
jj506 is offline jj506  Taiwan
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My paradise is running too.
In the beginning, I get PSU oscillating, add 4.7nF and 3.3nf compensation caps to solve it; then I have offset issue, the offset was fluctuating +/-200mV.
First, I used the 500R to trimming R15 but nothing change, after I reduce R43a/R43b to 9.1K then the offset was stable in between +/-20mV (change to 3.9K could down to +/-5mV)
I can see about 800uV of noise on my scope, I only used one transformer but LCLC filtering.

Will keep it to power on for stable, will listing it this weekend.

Regards,
jj
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Old 29th January 2013, 02:15 AM   #1318
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Cool, one more fish in the pool and thanks for the DC offset experiments. That can help other to get rid of that problem.
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Old 29th January 2013, 02:56 AM   #1319
jj506 is offline jj506  Taiwan
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Thanks Joachim Gerhard, you make very good design.
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Old 29th January 2013, 07:40 AM   #1320
FdW is offline FdW  Netherlands
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Quote:
Originally Posted by jj506 View Post
My paradise is running too.
In the beginning, I get PSU oscillating, add 4.7nF and 3.3nf compensation caps to solve it; then I have offset issue, the offset was fluctuating +/-200mV.
First, I used the 500R to trimming R15 but nothing change, after I reduce R43a/R43b to 9.1K then the offset was stable in between +/-20mV (change to 3.9K could down to +/-5mV)
I can see about 800uV of noise on my scope, I only used one transformer but LCLC filtering.

Will keep it to power on for stable, will listing it this weekend.

Regards,
jj
Nice, one more happy Paradise-ing!
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