sss said:[snip]lets say u got a power amp with a gain of 20 and u are measuring the thd at 1Khz freq and the thd at that freq is 1%
now u are doing the same test but under load conditions and the thd is still 1%
if the gain of that amp under load is only 10 the thd metter wount show nothing!! the thd remains 1% even if the signal is attenuated
hope that helps u to understand things better
No I don't. If the no-load THD is 1%, how can it also be 1% at load? All amps I have ever seen get worse under load. I also have no idea what is meant with the statement that at a gain of 10 the meter would not indicate anything? I realise this may be a language problem?
Jan Didden
CRFX said:
If you think about it, the PS caps are in the signal path, at least in a class B amplifier. If you draw arrows indicating the momentaneous flow of current through the output transistors and the loudspeaker when the rectifier diodes aren't conducting, you'll see the current going through the PS caps!
To what extent that affects sound is another issue, for those inclined to debate such things...
Rune
Hi,
And he asked himself...What is an amplifier?
A modulated powersupply perhaps? Must be....
So you'll be in part listening to that too, so.....
Does it matter what class the amp is running in for the powersupply caps to matter?
Not really, they're always there those nasty electrolytics, aren't they?
So yes, it would matter more in a class B or class AB amp than in a pure class A design but it matters nonetheless.
Nobody ever built an amp with nothing but polyprops in the PSU?
Guess not.
I'll be the first to admit it's easier to do with tubes due to the much higher rail voltages used but the difference is easily heard...
Thankfully electrolytics have much improved over the years but filmcaps haven't exactly been sitting still either.
Give it a try guys,
And he asked himself...What is an amplifier?
A modulated powersupply perhaps? Must be....
So you'll be in part listening to that too, so.....
Does it matter what class the amp is running in for the powersupply caps to matter?
Not really, they're always there those nasty electrolytics, aren't they?
So yes, it would matter more in a class B or class AB amp than in a pure class A design but it matters nonetheless.
Nobody ever built an amp with nothing but polyprops in the PSU?
Guess not.
I'll be the first to admit it's easier to do with tubes due to the much higher rail voltages used but the difference is easily heard...
Thankfully electrolytics have much improved over the years but filmcaps haven't exactly been sitting still either.
Give it a try guys,
Hi,
No idea these even existed...
When using tubes most people use something like these caps:
SCR
Lowest available voltage is 250VDC which low for tubes yet too high for most thing SS.
Still the difference is easily heard when upgrading loudspeaker x-over series caps, for instance.
Not cheap but still worth every penny.
Cheers,
No idea these even existed...
When using tubes most people use something like these caps:
SCR
Lowest available voltage is 250VDC which low for tubes yet too high for most thing SS.
Still the difference is easily heard when upgrading loudspeaker x-over series caps, for instance.
Not cheap but still worth every penny.
Cheers,
Hi,
Indeed, I did.
For non-boutique caps they're among the best you can get in MKP.
Jadis uses them and I'm sure other branders have wound their wrappers around them too.
Unfortunately I can only get them in small values (~0.100µF) and high voltages (~1000VDC+).
For SS PSU use I'm sure there are alternatives by means of the excellent BG caps, for instance or if all alse seems impossible, just bypass elcos with decreasing values of MKP in //.
100µF elco + 10µF MPK + 1µF + 0.100µF + 0.10µF + 0.010µF...
Knowing where to put them so they can work their best is just as important though...
Cheers,
Indeed, I did.
For non-boutique caps they're among the best you can get in MKP.
Jadis uses them and I'm sure other branders have wound their wrappers around them too.
Unfortunately I can only get them in small values (~0.100µF) and high voltages (~1000VDC+).
For SS PSU use I'm sure there are alternatives by means of the excellent BG caps, for instance or if all alse seems impossible, just bypass elcos with decreasing values of MKP in //.
100µF elco + 10µF MPK + 1µF + 0.100µF + 0.10µF + 0.010µF...
Knowing where to put them so they can work their best is just as important though...
Cheers,
Hi,
Thanks for the kind offer, Christer...
Not yet, I'm still too busy for the coming months upgrading my current stuff to think about cooking up something new...
Tell you what though, I'll definetely build a new phono preamp with not a single electrolytic cap in sight....
Unfortunately it WILL cost me an arm and a leg to get it where I want it.
Ciao,
Thanks for the kind offer, Christer...
Not yet, I'm still too busy for the coming months upgrading my current stuff to think about cooking up something new...
Tell you what though, I'll definetely build a new phono preamp with not a single electrolytic cap in sight....
Unfortunately it WILL cost me an arm and a leg to get it where I want it.
Ciao,
Magura said:
I may be wrong, but I think the ones I meant were even bigger,
but not as high voltage.
I thought AVX's glass capacitors were interesting, too.
Available in similar range to silver mica, extremely low
DF and DA and virtually impervious to anything including
the sort of radiation you'd find in reactor cores.
From what I see in the Allied catalog, they're VERY expensive.
I have no idea what 'sound' they'd have, if any. Sort of like bulk foil resistors, but much more costly. Best left to your
scientific sample-and-hold instrumentation, I suppose.
I don't believe I will be using them in any amplifier bypass
cap locations, or even in the feedback loop.
http://www.avxcorp.com/docs/Catalogs/ck31-32.pdf
I have several 100 uF @2200 V caps sitting around that
are probably polypropylene/paper? in oil, originally used for
defibrillators. Planning to use them in a tube amp power
supply. I think my source has some more, at $25 apiece.
They're slightly larger than the biggest multi-section 'lytic
you see on many tube amp chassis.
For the really exotic, you might consider carbon aerogel
supercaps. Have to stack a number in series to get the
required voltage, though.
Available in similar range to silver mica, extremely low
DF and DA and virtually impervious to anything including
the sort of radiation you'd find in reactor cores.
From what I see in the Allied catalog, they're VERY expensive.
I have no idea what 'sound' they'd have, if any. Sort of like bulk foil resistors, but much more costly. Best left to your
scientific sample-and-hold instrumentation, I suppose.
I don't believe I will be using them in any amplifier bypass
cap locations, or even in the feedback loop.
http://www.avxcorp.com/docs/Catalogs/ck31-32.pdf
I have several 100 uF @2200 V caps sitting around that
are probably polypropylene/paper? in oil, originally used for
defibrillators. Planning to use them in a tube amp power
supply. I think my source has some more, at $25 apiece.
They're slightly larger than the biggest multi-section 'lytic
you see on many tube amp chassis.
For the really exotic, you might consider carbon aerogel
supercaps. Have to stack a number in series to get the
required voltage, though.
janneman said:
To smooth the DC you need to do something. This something you do that harm the transient. You don't need to think that I'm talking about voltage ripples or something. When I said "transient", it is more a "quality" that is known to my ears. This transient-or-noise, is the major trade-off in power supply.
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