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Old 7th October 2011, 09:25 AM   #671
AndrewT is offline AndrewT  Scotland
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that looks like a gauss band around the transformer winding. An indication that they have spent a bit of money on trying to improve the performance standard of the transformer.

Are those the mains connections exposed on the bottom side?
In their present exposed condition they could be accidentally shorted to each other or to core. Take care.
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Old 7th October 2011, 11:25 AM   #672
Bicolor is offline Bicolor  Sweden
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AndrewT: Yes, both the primary and secondary connections are exposed, they were mounted facing the bottom of the amp. I am thinking of mounting it upside down so that the connections are easilly accessible. I will most likely put it upside down so that the connecions are easy to access.
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Old 7th October 2011, 04:41 PM   #673
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Originally Posted by FastEddy View Post
Your comfort zone may be different than mine ...
Or we may be talking about different aspects of comfort. E.g. you may be uncomfortable with so little power, while I am comfortable, because the supply voltage leaves safety margins in the IC's voltage rating and heatsinking.

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Originally Posted by FastEddy View Post
Your comfort zone may be different than mine ... I like to see the power supply noise floor down at least -110 db = snubbers help.
Liking to see -110 dB is a personal preference, not an objective necessity, but that is absolutely OK if you have such ambitions. Or if your speakers are so revealing and you live somewhere remote, where no ambient noise covers anything below -70 to -80 dB anyhow.

What I fail to see is, how those snubbers should bring the noise floor in the audio band significantly down. The caps in that "Snubberised PSU" are so small, they only work far above the audio band, if at all. And resistors don't remove noise, but add their own. What makes it worse is that those snubbers are in the wrong place to do any good.

You want to bring power supply noise down? Add 10-100 nF capacitors next to the rectifiers to fight diode switching noise. Then add big smoothing caps to filter the AC components out, and that is where you really determine the power supply noise floor. Finally you need 10-100 nF decoupling caps next to the supply pins of all ICs and that's it.
You may still need a mains filter to achieve your ambitious goal, but the noise that comes in from mains does not really count as the power supply's own noise and will certainly not be impressed by snubbers.
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Old 7th October 2011, 05:49 PM   #674
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Originally Posted by pacificblue View Post
Or we may be talking about different aspects of comfort. E.g. you may be uncomfortable with so little power, while I am comfortable, because the supply voltage leaves safety margins in the IC's voltage rating and heatsinking.
Granted, except that higher voltages give the designer the option of improving dynamic range and improving PS noise levels. (More volts and less current can result in the same power output, no?)

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Liking to see -110 dB is a personal preference, not an objective necessity, but that is absolutely OK if you have such ambitions. Or if your speakers are so revealing and you live somewhere remote, where no ambient noise covers anything below -70 to -80 dB anyhow. ...
Well, a bit more than just personal preference. 16bit CD quality is in the 80+db dynamic range, so that benchmark might be your personal preference. Mine is 24bit or better DVD quality = 100db to 115db range.

Building to that quality thresh hold = more, better.

Quote:
What I fail to see is, how those snubbers should bring the noise floor in the audio band significantly down. The caps in that "Snubberised PSU" are so small, they only work far above the audio band, if at all. And resistors don't remove noise, but add their own. What makes it worse is that those snubbers are in the wrong place to do any good.
Yes ... No ... Yes, maybe. Placing "snubbers" on the +/0/- power rails right next to the amp (or op-amps) is a recommended chip maker design (TI, National, Analog Devices, et al).

Quote:
You want to bring power supply noise down? Add 10-100 nF capacitors next to the rectifiers to fight diode switching noise. ...
Mmmmm ... I do both, add plastic 10-100uF across the big PS electrolytic caps (both xformer and output rails) AND the same plastic caps across the power rails very, very close to the +/0/- power pins on the input gain stage of any amp I build.

Your results may vary, but I have come very close to (IMHOP) the ideal -110db PS noise floor = which compliments the 105-120db dynamic range of 24bit-48k/96k/192k of DVD audio track (and pro music recording studio quality).

---

"All of the world's problems can be fixed by resolving the impedance mis-matches ..." - Bob Porter / Mad Science

Last edited by FastEddy; 7th October 2011 at 05:55 PM.
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Old 8th February 2012, 10:56 AM   #675
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Hello friends!!
I have no more idea about it.But I think you can more help about by google search.
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Old 4th March 2012, 12:37 AM   #676
redjr is offline redjr  United States
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The link in post #1 is invalid. Is there a new link Nuuk?
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Old 4th March 2012, 12:42 AM   #677
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This one works for me.

Building a Gainclone chip amp power supply.

John
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Old 4th March 2012, 01:27 AM   #678
redjr is offline redjr  United States
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Thanks John!
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Old 5th March 2012, 04:55 PM   #679
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Originally Posted by john blackburn View Post
All very good advise ...
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Old 5th March 2012, 05:08 PM   #680
redjr is offline redjr  United States
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Originally Posted by FastEddy View Post
All very good advise ...
I haven't read through the document fully yet, and I won't be constructing my own PSU, but one quick question before I start wiring up my chip-amp. This is very basic and easy... Is it common practice to tie the PSU ground to earth ground at some point, or does it float internally? What about all the connectors that fit to a metal enclosure?
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