Sound Quality Vs. Measurements - Page 381 - diyAudio
 Sound Quality Vs. Measurements
 User Name Stay logged in? Password
 Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read Search

 The Lounge A place to talk about almost anything but politics and religion.

 Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
 20th March 2012, 11:32 AM #3801 diyAudio Member   Join Date: Sep 2004 Location: Belgrade, Serbia @gootee You may be interested to know that Dan d'Agostino uses a LOT of 47 uF capacitors to decouple his rails everywhere. I haven't counted them, but off hand, I'd say no less than 10 or more per rail, in addition to smaller value caps. The main PSU uses 6,800 uF caps in parallel, if memory serves, three in parallel per each rail. But, given the fact that EVERYTHING is electronically regulated, and that his supply lines are rather high, even those seemingly not-too-big caps in fact provide a LOT of energy storage when added up.
 20th March 2012, 12:01 PM #3802 diyAudio Member   Join Date: Sep 2004 Location: Belgrade, Serbia In a design note from Motorola, I think the one in which they propose two power amps, there's a good sideline on how to calculate your capacitor requirements. Not scientific, more a rule of the thumb, but most useful nevertheless. Essentially, they say that experience has taught us that we need 1...2 Joules of energy for every 10 Watts of dissipated power, depending on how complex and demanding the load is. So when Wayne () sits down to work it out, he can easily "double down" as he pleases. Since one knows what the rails will be, and assuming we use plus and minus rails, PER RAIL capacitance can be worked out using a simple formula: Joules = (V+ x V+) Farads If my rails are +/- 50V, and I use 10,000 // 10,000 uF // 3x2,200uF for each device, I can have: (50 x 50) 0.0266 = 66.5 Joules good enough for 332.5 Watts into an evil load dmanind the maximum from the amp, to 665 Watts into a pristine clean and easy load. Over time, this formula has shown itself to be very true indeed. Obviously, it applies to the power supply only, for this to REALLY happen in REAL life, you also need beefy power tranformers, powerful rectifiers and an amp output stage capable of actually delivering this kind of power. For power amp transformers, again there's a rule of the thumb - use as many VA in the transformer as you want watts out. If you want a 2x150W amp, minimum transformer value should be (2x150)2 = 600 VA for a stereo amp. Not scientific, but hey, it works.
Account disabled at member's request

Join Date: May 2006
Quote:
 Originally Posted by ThorstenL Hi, With respect, having HD content at -90dB in an Amp also has no other effect than self satisfaction. Despite repeated requests by me you have not offered anything that demonstrated either that such low levels of HD reliable produce "good sound" or indeed that such low levels of HD can be delivered to the listner using any available speaker... Ciao T
Yet it has also not yet been demonstrated that amps with large THD sound or low or no feedback sound better, in fact there are more hi end amps demonstrating very low THD and higher feedback winning awards than the other method........ makes one think

Previously: Kuei Yang Wang

Join Date: Nov 2002
Dejan,

Quote:
 Originally Posted by dvv The only problem here, Thorsten, is that commerical devices with small caps usually also have small transformers - NOTHING like the Goldmund. Then again, for one Goldmund, you could buy like 10+ of such devices. Let's not mix cranberries with watermelons. Which is why you plan to use 144,000 uF instead of 13,600 uF.
There are two issues here.

One is the evidence that low value power supply capacitors limit power delivery (they do not, undersized mains transformers do however).

The other issue what I personally, as supposed High End Guru and merchant of questionable (according to some) audio ideas, concepts and devices plan to do for myself. I mean they'd revoke my High End Guru licence if I made the Amp with a 250VA Torroid and 4 * 4,700uF, even if it did deliver 180W into 8 ohm (one channel) and was adequate with music...

Less tongue in cheek, as a rule (I have yet to find exceptions), there are no limits up to which one may increase PSU capacitance AND power transformer size (other than practical/monetary), with some benefit. Though at the levels I intend to use we are already pretty far past the point of diminishing returns.

Then again, there is something to an amp that runs of eight stacked 12V SLA Batteries (for +/-48V) that is hard to get with mains powered amp's...

Ciao T

Previously: Kuei Yang Wang

Join Date: Nov 2002
Hi,

Quote:
 Originally Posted by dvv Since one knows what the rails will be, and assuming we use plus and minus rails, PER RAIL capacitance can be worked out using a simple formula: Joules = (V+ x V+) Farads If my rails are +/- 50V, and I use 10,000 // 10,000 uF // 3x2,200uF for each device, I can have: (50 x 50) 0.0266 = 66.5 Joules good enough for 332.5 Watts into an evil load dmanind the maximum from the amp, to 665 Watts into a pristine clean and easy load. Over time, this formula has shown itself to be very true indeed.
As I happen to have 36,000uF per rail and 56V rails it would seem I'm well past that (twice actually). So I should be fine for 665W into a nasty load, which is probably quite nice for an Amp I'd call notionally 150W... Maybe my mains transformer is a wee bit undersized.

Ciao T

Previously: Kuei Yang Wang

Join Date: Nov 2002
Hi,

Quote:
 Originally Posted by homemodder Yet it has also not yet been demonstrated that amps with large THD sound or low or no feedback sound better, in fact there are more hi end amps demonstrating very low THD and higher feedback winning awards than the other method........ makes one think
Well, first, there are by far fewer Amplifiers of (for example) the SE DHT no-NFB variety and Sturgeons rule applies. So the statistics you quote do not help us much.

As to: " it has also not yet been demonstrated that amps with large THD sound or low or no feedback sound better", I think the solution for everyone is to go and listen. We must also realise that we do not listen amplifiers, but to whole systems.

Ciao T

diyAudio Member

Join Date: Feb 2007
Location: Tashkent
Quote:
 Originally Posted by DF96 Unless your waveform contains an infinite number of finite discontinuities or any infinite continuities you can use Fourier and it will perfectly preserve the waveform. All music waveforms are bandwidth-limited (if only by the microphones) so have no discontinuities, therefore a Fourier transform fully contains the information in the waveform. Whether this is useful or not is a different issue, because a problem is best tackled in the way which works best, but let's not have any loose talk about Fourier not capturing things like envelope. It might not do it in a useful way, but it does do it.
Music waveforms are non-periodic. Fourier transform, strictly speaking, can not be applied to non-periodic functions. But it is nevertheless applied, with definite degree of accuracy. A devil is in the limitations of its applicability. For some cases limitations are not essential, but they are essential for exploring audio perception.

Account disabled at member's request

Join Date: May 2006
Quote:
 Originally Posted by ThorstenL Hi, Well, first, there are by far fewer Amplifiers of (for example) the SE DHT no-NFB variety and Sturgeons rule applies. So the statistics you quote do not help us much. As to: " it has also not yet been demonstrated that amps with large THD sound or low or no feedback sound better", I think the solution for everyone is to go and listen. We must also realise that we do not listen amplifiers, but to whole systems. Ciao T
I take my stats from reading about 15 audio publications from tubes to solid state, a lot of the facts about the circuits are unknown to the writers of these so they just state the little the manufacturer tells them.

The 2 best amps I have listened to are on opposite sides of the fence. One a french amp with very high feedback Lavardin (more so then usual) and one with fairly low NFB a electrocompaniet monster I own. Each one has its stronger and weaker points but I cannot say that one or the other sounds better because of the amout of feedback used or their THD figures.

 20th March 2012, 12:56 PM #3809 diyAudio Member   Join Date: Feb 2003 Location: .. not true as engineers know - yes the math is a little more complex to satisfy pure mathematicians but can still be made to work for bandwidth and time limited continuous signal representation the simple gedankenexperiment version: for recorded music we can just loop the recording - instant "infinitely periodic" signal to analyze Windowing functions are well studied - you can calculate the time domain "flitering" loss - can be way below real signal thermal noise, beyond recording microphone bandwidths the time series and the full complex Fourier repesentaion of a Digital Audio signal are exact Duals - no information is lost in the conversion from one ot the other (finite rounding errors can be made small by working with long enough wordlength) sorry for your "conspiracy theory" - but engineers do test, verify, use tools that really do work with real world signals, electronics - just how do think the 3 Mbaud DSL signal is made to work over voice telephone twisted pair?? by a million mathematically illiterate monkeys with soldering irons?? – that’s more the DiyAudio “just try it” version (a little overlapping editing - SY has given the example before - its still a good example to "debug" your "nonperiodic" signal objection without heavy math) Last edited by jcx; 20th March 2012 at 01:09 PM.
diyAudio Moderator

Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 2
Quote:
 Originally Posted by VladimirK Music waveforms are non-periodic. Fourier transform, strictly speaking, can not be applied to non-periodic functions.
Actually, it can. Any function of finite duration can be made periodic without changing the physics. For example, let's say I want the frequency spectrum of Roland Kirk's performance of Seranade to a Cuckoo. It's 4:32 long. Call the time domain function SC(t). The boundary conditions are SC(0) = SC(4:32) = 0, since the song starts and ends. Then put SC(t + 4:32) = SC(t - 4:32) = SC(t). Voila, a periodic function!
__________________
"You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is."

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are Off Pingbacks are Off Refbacks are Off Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post KT Class D 3 4th June 2014 12:02 AM Marik Solid State 2 2nd January 2012 08:59 PM dchisholm Equipment & Tools 5 16th July 2011 09:40 AM okapi Everything Else 13 2nd September 2008 03:06 PM jackinnj Everything Else 2 5th July 2003 03:02 PM

 New To Site? Need Help?

All times are GMT. The time now is 01:29 AM.