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Old 7th May 2003, 02:25 AM   #11
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Default Any Noise Annoys An Oyster....

My whole system hangs off a mains isolation transformer, and not in use audio and video items are unplugged.
Items like microwave oven and TV's and my washing machine containing SMPS are turned off at the wall when not in use.
I find that these loads on the mains can cause audible degradation despite the isolation transformer, but the ISO TX does give very great benefit in terms of smoothness and cleanliness in the sound of my hifi, and the day/night difference is very much reduced if not eliminated.

Eric.
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Old 7th May 2003, 02:45 AM   #12
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Quote:
Originally posted by mrothacher
I've always felt it was primarily the result of these effects:

1. Far less power line noise at these hours
2. Far less ambient noise at these hours.
3. Our auditory acuity peaks at night, and arguably more so in the critical midrange.
Agreed, although #1 can and should be addressed by correct PSU design. Frank is correct in his post below that a high PSRR is A Good Thing.

Tim said,
Quote:
'Nother one of those ironies...people push tube rect's yet say PSUs need good regulation
I'd rather not have all the wideband hash that SS rectifiers generate. Snubbing and filtering seldom works anywhere near as well as not generating the problem in the first place, esp with SE circuits where the rectifier duty cycle will vary with load. Then there are a number of dampers with quite low series resistances (very cheap too), and of course a differential PP circuit is much closer to a constant draw, so the rectifier resistance is much less of an issue IMO/IME. Finally using a decent <i>regulator</i> properly implemented makes the diode resistance moot. I have CCS's as the first stage in my shuntregs with impedances (depending on which one) of 100k -> Gig ohms.
It'll be interesting to try the Cree HV Schottky's later and get Paul to measure them in circuit.

It all depends how and what you're trying to do. If you want to build an amp for $100 from junkbox parts, then there will inherently be compromises that could be aleiviated for a little more outlay, even if that simply means another choke and cap, that you don't already own, for another LC stage. Both approaches have equal merit, just depends on the results you're seeking.

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Old 7th May 2003, 05:47 AM   #13
Aiace is offline Aiace  Italy
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Default Cortisolo

Since 11pm your blood is rich of cortisolo, so you can hear light better.
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Old 7th May 2003, 06:23 AM   #14
Morse is offline Morse  United States
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Interesting topic guys;

I agree that line noise is a big problem that helps explain the 'wee hours' phenomenon - which is one reason that I put together a JR Isofilter for my CD source.

Okay, let's go all the way then to cut out line noise - a battery supply on the amp. Anyone here tried it and if so, what are the ups and downs? I've thought about getting about a dozen of those rechargeable 12V gel cells together and using it for a headphone amp. Good or bad idea? And, with only about 144V to play with, what valve would you recommend for a headphone amp - pref something cheap (er, uh that's affordable...)!

Suggestions?

Thanks and all the best,
Morse
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Old 7th May 2003, 08:38 AM   #15
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I highly doubt it's line noise; I have my comptuer running basically any time I'm awake, and my amps being plugged into the same strip as the computer, surely experience quite a bit of line noise.
Earlier today (or yesterday I should say) the radio didn't sound all that great at all, but now it's listenable, and the computer's been on all the same.

Think I'll try listening during the day with the computer off to complete the proof..

Tim
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Old 7th May 2003, 08:55 AM   #16
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Quote:
Originally posted by Sch3mat1c
snip...
Earlier today (or yesterday I should say) the radio didn't sound all that great at all, but now it's listenable, and the computer's been on all the same.
snip...
Tim
Tim,

If your radio is anything like ours over here, the quality is variable by the hour. It depends who puts what presets into the Optimod (generic), who sets the studio out levels, and which lines are selected.
I am currently listening to a station called BBC Radio 2 (for old fogies) on FM, and the announcers voice has clearly audible compression artifacts bordering on distortion.
The BBC used to be the pinacle of standards and quality....
Things 'aint like they used to be


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Old 7th May 2003, 09:06 AM   #17
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Quote:
My whole system hangs off a mains isolation transformer
I've been thinking about oneday getting one of those wound with electrostatic screen....what would be a rough guide to the current such a thing should deliver?

Cheers,
Bas
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Old 7th May 2003, 09:26 AM   #18
dhaen is offline dhaen  Europe
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Bas,

Go for as big as you can afford. Maybe 500 to 1000 VA.
The larger you go, the better the load regulation becomes.
If you're having it wound, I'd recommend adding some taps for + & - 5% to optimise your mean mains voltage.

Including such a transformer with an ES will reduce the mush from "outside", but mush produced "inside" will spread more, due to the increased power source impedance.

Cheers,
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Old 7th May 2003, 09:46 AM   #19
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Hi John,

Quote:
but mush produced "inside" will spread more, due to the increased power source impedance.
So seperate isolation transformers for each component is preferable?

Regards,
Bas
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Old 7th May 2003, 09:48 AM   #20
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I'd recommend adding some taps for + & - 5% to optimise your mean mains voltage.
Brilliant idea!
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