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Old 15th January 2012, 03:52 PM   #1001
Pano is offline Pano  United States
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Quote:
Originally Posted by ThorstenL View Post
The direct DAC feed to headphones reduced but not removed this issue, so at the time I figured "it must be the recording" (to a degree it may actually be).
Recording engineers seem to think it's a recording problem. Look at any pro audio catalog under "De-Essers".
They may be happy to hear that they need only fix the playback, not the recording. IME, poor crossovers are a large part of the problem at the playback end.
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Old 15th January 2012, 03:55 PM   #1002
Previously: Kuei Yang Wang
 
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Folks,

The problems created by SMPS illustrated:

Click the image to open in full size.

The above is a rather excellent result. Sticking even a generic 20MHz 'scope on the DC Output of most SMPS's is very illuminating.

It is possible to reduce the problems, but it tends to get so complex that you loose the cost/weight/size benefits for which you where introducing the SMPS to start with.

An alternative could be a Sinewave inverter running directly off the mains at 400Hz output and the use of 400Hz transformers for aircraft/ship/military use instead of 50/60Hz. This can give many of the advantages of an SMPS and keeps the RF noise controllable.

Ciao T
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Old 15th January 2012, 04:05 PM   #1003
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Pano,

Quote:
Originally Posted by Pano View Post
Recording engineers seem to think it's a recording problem. Look at any pro audio catalog under "De-Essers".
Thank you very much. I am very familiar with De-Essers and their use. And no, they do not really fix the problem either.

A funny thing is that we did not have any severe problems with this back in east germany where recording consoles used Transformers and discrete circuitry.

Quote:
Originally Posted by Pano View Post
They may be happy to hear that they need only fix the playback, not the recording. IME, poor crossovers are a large part of the problem at the playback end.
Please re-read what I wrote. Certain recording techniques (which interestingly seem to rarely if ever involve the use of a De-Esser) seem to avoid this problem becoming audible or to appear at all (it would be interesting to know WHY).

However my experience is that certain types of replay systems appear to handle what is on the recording in a way that aggravates the audibility, often severely so, while others appear to not cause such aggravation and if such a thing is even possible seem to "fix" the problem.

Of course, I have no real interest in debating this, as I do not have the problem. I merely found the fact that I do not have this problem, despite the fact that if measured performance using the traditional set was a reliable guide to sound quality my system should sound completely awful) both interesting and significant as well as a bit bewildering...

I was mainly sharing my bewilderment and considered that some may derive some benefit from sharing it...

Ciao T
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Old 15th January 2012, 04:20 PM   #1004
Pano is offline Pano  United States
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Please re-read what I wrote
No need. Actually, I agree with you. So no debate needed, TL.
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Old 15th January 2012, 07:01 PM   #1005
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Quote:
Originally Posted by ThorstenL View Post
Folks,

The problems created by SMPS illustrated:

Click the image to open in full size.

The above is a rather excellent result. Sticking even a generic 20MHz 'scope on the DC Output of most SMPS's is very illuminating.

It is possible to reduce the problems, but it tends to get so complex that you loose the cost/weight/size benefits for which you where introducing the SMPS to start with.

An alternative could be a Sinewave inverter running directly off the mains at 400Hz output and the use of 400Hz transformers for aircraft/ship/military use instead of 50/60Hz. This can give many of the advantages of an SMPS and keeps the RF noise controllable.

Ciao T
I don't understand the point being made with this measurement, also since I do not know what was measured and how. But two observations can be made.

The first is that up to 300Khz, ripple is below 10uV against a 100mV reference level, so that would be better than 0.01% or 80dB down. Show me an linear PS under a realistic load that does better. The second is that all the nasties are at RF, most of them pretty high up in the MHz scale. Provided the source of this RF contamination is properly shielded, I don't see what would be complicated in getting rid of it.

vac
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Old 15th January 2012, 07:20 PM   #1006
benb is offline benb  United States
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Quote:
Originally Posted by vacuphile View Post
...
The second is that all the nasties are at RF, most of them pretty high up in the MHz scale. Provided the source of this RF contamination is properly shielded, I don't see what would be complicated in getting rid of it.

vac
I've bolded what I suspect is the thing that has many people flummoxed with SMPS's.
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Old 15th January 2012, 07:28 PM   #1007
tvrgeek is offline tvrgeek  United States
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The supply in my Aimor amp is almost as bad! Dried out caps, cheap rectifiers, no snubbers, and nice torrid transformer.
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Old 15th January 2012, 07:35 PM   #1008
wahab is offline wahab  Algeria
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Originally Posted by tvrgeek View Post
and nice torrid transformer.
This amp is really insane...
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Old 15th January 2012, 07:41 PM   #1009
BFNY is offline BFNY  United States
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Quote:
Originally Posted by vacuphile View Post
...
The first is that up to 300Khz, ripple is below 10uV against a 100mV reference level, so that would be better than 0.01% or 80dB down. Show me an linear PS under a realistic load that does better. The second is that all the nasties are at RF, most of them pretty high up in the MHz scale. Provided the source of this RF contamination is properly shielded, I don't see what would be complicated in getting rid of it.

vac
I would not draw that conclusion at all from this data. If you said from 100kHz up to 300kHz, fine. The horizontal scale STARTS at 100kHz.

Since this is obviously a spectrum analyzer (RBW and VBW gives it away) and most SA show nothing below 100kHz, (high pass filtered) you can't say anything about what the supply does below 100kHz.

While on the subject of test gear, another tip - This relates to scopes. Scopes have a linear display. This means they show at most about 40dB of dynamic range.

Can anyone hear more than 40dB? If so, don't expect any amazing revelations from a "single" scope display. Dual displays with different input ranges, of course, are different.
Conversely, if you can't "see it" on a single scope display, that proves very little that it's not there.
This fundamental problem has been a big detriment of folks looking in the "time domain" for things they can hear.
To truly do it right, you need to grossly oversample with a LOT of resolution and BW, and view the time domain on a log scale. This means using something like a 16 bit 10-100MS digitizer.
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Old 15th January 2012, 07:43 PM   #1010
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Switching supplies IM garbage back, and, as well, the HIGH frequency garbage MUST be 'nulled', if possible, by power supply rejection, which REQUIRES the feedback loop to work extra hard, OR it becomes part of the output signal.
Wow, do our 'critics' actually think anything through?
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