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回覆 (203): "A Piece of Cake"
If memory serves, Limage was referring to a subtle change of 4 notes of the low registers of the Organ, not the overall subsonics during the intro before the brasses kick in.
davidchan
12-11-15
04:18:33
回覆 (202): "A Piece of Cake"
咁隻碟買嚟做咩呀? 播到 = 衰聲, 播唔到 = 冇嘢聽o 我妖!
Derek2A3
12-11-14
20:44:21
回覆 (201): "A Piece of Cake"
 
>I can surely hear the bass before the horn kick in on side one opening track lor! As the old English say "A piece of cake"! <  
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According to Limage, the only system he has even heard that could reproduce that effect sounded bad with every other piece of music! Now, I know that is true, lor! :-)  
 
 
thekong
12-11-14
17:47:37
回覆 (200): "A Piece of Cake"
Kong, come sndcollect your prized Big Decca. I can surely hear the bass before the horn kick in on side one opening track lor! As the old English say "A piece of cake"!  
 
bobui
12-11-14
16:40:38
回覆 (199): On power supply
But if he is more into controlling AC resonance, ripple or such. I would think a regulated power supply would be even more effective than a choke or use of a Schottky.  
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i doubt it. for a start, it does nothing to the AC resonance problem. secondly, unless you build your own discrete regulator, many chip regulator will throw in the towel in relatively low frequency.
drwkng
12-11-02
12:42:43
回覆 (198): On power supply
The addition of a choke is more effective in filtering out AC ripple which is not frequently found in digital circuit such as DAC. I believe JS may actually done extensive research before he tells everyone Schottky is more linear.  
 
But if he is more into controlling AC resonance, ripple or such. I would think a regulated power supply would be even more effective than a choke or use of a Schottky.
bobui
12-11-02
12:24:39
回覆 (197): On power supply
 
 
The next question to ask then: is the AC resonance a true problem in real life?  
 
 
limage
12-11-02
12:04:36
回覆 (196): On power supply
 
 
Of course, these frequencies are well out of range for the human ear, but resonances have the tendency to modulate other frequencies that may fall into the human range.  
 
I had experiences of oscillation due to a dying tube, but I don't recall any persistent resonance of any kind ever in my system.  
 
 
limage
12-11-02
11:59:29
回覆 (195): On power supply
 
 
Oh yes, get it.  
 
The whole thing seems to quibble over an AC resonance in the range of 40KHz to 200KHz. I don't think I have been bothered much by such experience over the years.  
 
 
limage
12-11-02
11:43:41
回覆 (194): On power supply
suppress resonance  
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Is it not that to suppress reasonace is to put a small cap across each schottky?
bobui
12-11-02
11:39:31
回覆 (193): On power supply
this part..  
 
The third part is a damping network across the power transformer which damps the winding resonance so it will not resonante from noise coming in from the outside world.
drwkng
12-11-02
11:24:45
回覆 (192): On power supply
 
 
To address the problem of AC resonance feedback, I thought Mr. Swenson meant the addition of a smaller cap C2 along with the choke L1.  
 
limage
12-11-02
11:13:15
回覆 (191): On power supply
What in fact is the function of the series C1, R1 prior to the bridge rectifier?  
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you don't read the paper^-^  
suppress resonance.
drwkng
12-11-02
11:00:05
回覆 (190): On power supply
 
 
What in fact is the function of the series C1, R1 prior to the bridge rectifier?  
 
 
limage
12-11-02
10:51:05
回覆 (189): On power supply
That's what Mr. Swenson does : )  
He knows his stuff well!  
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yes and a very nice gentlemen as well.
drwkng
12-11-02
10:40:37
回覆 (191): On power supply
the small first cap allows the large conduction angle, but it also allows the filter to not need nearly as much minimum current as a true choke input filter  
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Seems to me what Mr. 史雲生 wants to achieve is a low minimal current choke input filter. This way, the choke that he employs has much less inductance & consequently can be smallish enough for most applications.  
 
If space & cost is not ones concern, just go with the standard choke input filter.
Derek2A3
12-11-02
10:33:49
回覆 (190): On power supply
Some prefer schottky, others may not. Some designers purposely use a lower uf first cap in a pi filter to increase voltage regulation, others insist that is not desirable in Class A circuitry.  
 
The use of schottky and pi fiter is the 中心思想? Am i missing something? Enlighten please!
bobui
12-11-02
09:28:42
回覆 (189): On power supply
Nice thread here...need to catch up all these pages : )
CFT
12-11-01
20:06:15
回覆 (188): On power supply
"I am an electronics engineer working for a semiconductor company (I'm not allowed to say which one), I layout integrated circuits, mostly large high speed digital with sensitive analog circuitry as well. My specialty is power distribution networks in these chips, providing low noise power and ground networks to provide very low jitter on the interface between the digital and analog sections. This jitter needs to be kept in the single digit ps range, which is not easy. In order to meet this we need on chip regulators, these regulators are always linear regulators, switching regulators simply produce too much noise. "  
 
From post #69:  
http://forums.slimdevices.com/showthread.php?82648-Linear-Power-Supplies/page7  
 
That's what Mr. Swenson does : )  
He knows his stuff well!
CFT
12-11-01
19:55:06
回覆 (187): On power supply
 
 
咁長一篇,中心思想......  
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我已經「咳」咗三分一,囉播!  
 
肥強話長D就好D嘛。  
 
 
limage
12-11-01
18:33:37
回覆 (186): On power supply
John Swenson  
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咁長, not necessary better ah!  
 
I google his name and the first one came out is a man in Geology. 2nd one is a musican, third one is a professor at Fuji Uni teaching modern Jap politics............  
 
One thing for sure is that this JS below is not a professor lor! He spell Pannsonic with two nn. It should be Panasonic lor!  
 
bobui
12-11-01
18:21:39
回覆 (185): On power supply
John Swenson  
________  
 
屎暈生,整雞湯嫁?咁長一篇,中心思想系mud?
icefox
12-11-01
17:44:52
回覆 (184): On power supply
 
 
This is an extract taken from the link suggested by CFT from his thread. It is written by John Swenson in response to questions against linear power supply.  
 
 
John Swenson:  
 
"Many years ago I was building audio DACs for myself and found out that what power supply I used had a significant impact on the sound. I set out to find out what differences in these supplies caused the difference. I ran many hundreds of tests with different supplies, listening and measuring the supplies and trying to come up with correlations, it was not easy and took a couple of years. One thing I learned from these tests was that most supplies feed a fair amount of noise back into the AC mains as well as the noise feed to the audio circuits. This noise injected back into the mains turned out to be one of the most important aspect of the tests, and one which is frequently completely ignored in power supply tests.  
 
It turned out that frequency range that caused the most impact on sound quality was the 40KHz to 200KHz range. MHz and up was usually well controlled and filtered, and frequencies in the audio range were usually handled very well by the regulators in the circuits, but the intermediate frequencies were not well dealt with. And it was the amount of this noise injected back into the mains that had the most impact on sound quality, presumably by being carried to other components in the "stereo system" such as power amps and preamps. I tried this with many different audio systems, from inexpensive consumer systems, expensive audiophile systems, pro audio systems and all of them seemed to be susceptible to this incoming noise on their AC.  
 
Many of these components contained "line filters" designed to block incoming noise, but most of those only seemed to be effective in the MHz and up range, having very little affect in the 40KHz to 200KHz range. I probed around inside these other components and watched what happened to this noise coming in over the AC mains and found many of these components actually had resonances in this range which significantly magnified incoming noise. In quite a few cases even if their own power supply was not generating noise in this region, the resonances wound up feeding significant noise into the circuitry when noise in the right range was on the AC.  
 
So the summary of all these tests was that the biggest requirement for a PS was to not send noise in the 40KHz to 200KHz range back down the AC line, keeping noise out of the DC fed to the DAC also made an impact, but it actually was not as big a concern as what went to the mains. It also had to not be susceptible to noise in that range coming from OTHER components.  
 
So I set out to design a PS that met these goals. Since this was going to be a onesie for my own use it was a lot easier to build a linear supply. I did a LOT of spice simulations trying out different topologies and components which eventually evolved to what I have today. I built several and proved that the real world did in fact closely match the spice results so I was quite confident that doing the exploration with spice was a reasonable approach.  
 
The result is very different than most linear supplies. Most linear low voltage supplies employ a single stage very large value cap after a bridge regulator. This of course only conducts over a very narrow portion of the cycle, giving rise to very high current pulses in the transformer. Common rectifiers produce switching noise in the bad frequency range, with in conjunction with the current pulses cause the power transformer to ring like a bell right in the bad range. This noise goes right through the power transformer and into the mains. Even if you have a good regulator which blocks this noise from the circuit beeing fed from this supply, the noise still goes out to the mains.  
 
My design attempts to alleviate these issues in several ways, first it uses Schottky rectifiers, second it uses a choke based asymetrical PI filter after the rectifiers. The first cap is much smaller than the second cap. The result is a supply which has conduction over almost the entire cycle, thus no large current spikes. Having the small first cap allows the large conduction angle, but it also allows the filter to not need nearly as much minimum current as a true choke input filter. What comes out of the filter is almost pure sine wave which is very easy for the regulator to deal with. In a traditional linear supply the sawtooth output has a lot of high frequencies which are much harder for simple regulators do deal with. The third part is a damping network across the power transformer which damps the winding resonance so it will not resonante from noise coming in from the outside world.  
 
The result of all this is a design which has extremely low noise injected back into the AC line and very low noise sent to the audio circuitry. It's simple, does not contain any custom components, no special "audiophile" parts, is easy for inexperienced DIYers to build. Is it the only design possible? of course not. Can a switching supply be made which can match this performance, almost certainly. But its not going to be nearly as simple, will probably need custom magnetics and could very well cost more money to make and will be way out of the range of a DIYer to build."  
 
 
Here is the schematic of the design mentioned above:  
 
limage
12-11-01
10:56:58
回覆 (183): new toy for my own indulgence
Congrats, king. So the new toy is balanced, double 27 + 5687, isn't it?  
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it is not quite balanced yet. the two 27 is part of a differential circuit. so with a new volume control and source selector pcb, it should be able to take either RCA or XLR. the output is still single end. there is simply not enough space to make it balanced. with the differential circuit, a phase switch can also be incorporated without much hazzle.  
 
BTW, what are those orange color caps?  
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those red caps are just run of the mill PP caps. mdlover recommended to me. they are fine as power bypass. but they are no vcap of course. so as output it is no comparison to vcap.  
 
Not sure if it's the angle the pic was taken, seems to me there is no tube socket, am I right?  
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there are sockets. just the standard 27 pin sockets.
drwkng
12-09-29
00:19:20
回覆 (182): new toy for my own indulgence
Congrats, king. So the new toy is balanced, double 27 + 5687, isn't it? BTW, what are those orange color caps? Not sure if it's the angle the pic was taken, seems to me there is no tube socket, am I right?
Derek2A3
12-09-29
00:08:28
回覆 (181): new toy for my own indulgence
Photobucket  
 
 
Photobucket
drwkng
12-09-28
20:31:41
回覆 (180): CD
""""This is one of the CD that we used, in case you are interested."""  
 
Thanks, Icefox. This one is really a sound system killer!
ThomasC2
12-09-19
21:38:31
回覆 (179): Chicken stuff
of course the LS 3/5a  
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and Lowther too la!  
 
Well, the brits did handle the Olypmic rather well given that it is much smaller than the previous host country.  
 
We do not diagree "Small can be beautiful". Right?  
 
bobui
12-09-19
16:50:26
回覆 (178): Chicken stuff
 
 
Good conversation bobui. Britain has been very successful shedding all her encumbrances — the colonies which include Hong Kong, the World Cup, the peerless air forces, Rolls Royce, London Bridge and of course the LS 3/5a. Brits are now pretty free with nothing to worry about except perhaps the acuity of their ears which somehow remains unchanged.  
 
 
limage
12-09-19
11:08:10
回覆 (177): Chicken stuff
乜突然間進步咁X多架?  
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you try to talk to the brits.........complete waste of time lor!  
 
I asked him to join 1peking. He said he would take a look at it and see if he can fit in. He is a bit concern about offending people here and bring embrassment to me. I told him, no lor. I embrass myself enough!  
 
By the way, the PS audio, DAX Decade and chord/802 does sound very nice. My BIL called B&W some years back when he first got the 802 and telling them the sound is thin and asked if it was lack of power. B&W sent over an engineer to his home and adjust the air pots of the mid and bass at the rear and it all sing well since then. A luxuary we wont even have a tiny chance lor!  
 
bobui
12-09-18
22:40:44
回覆 (176): Chicken stuff
He has recently just purchased a Voyd turntable, Omega arm!  
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乜突然間進步咁X多架? 記得叫你兄弟唔好用雞頭呀!
Derek2A3
12-09-18
22:20:15
回覆 (175): Chicken stuff
"Oh why you play with those DIY chicken stuff, get serious man?"  
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icefox, you got me right on the spot. Thats exactly the long night talk my brother in law and me had over the few bottles of white/red a few days back in that AV room. Sting, Chris Botti, N Jones, Pink Floyd were all there the whole evening with us! And the talk went something like this.  
 
bobui: Cheese to good health and a long life ahead  
Brother in law (BIL): Good luck to your trip to Zurich, for how long?  
bobui: About 6 days.....oh, lets not talk about the shit old boring work now. Lets put Sting live Italy on. Shall we?  
BIL: Sound ok to you? Oh, U dont like CD anyway. Doesnt matter?  
bobui: No no no! You will be surprise. You ready????? I just got myself a Meridain 6 series combo and a Naim CDX. Both 2nd hand. Ha Ha!  
BIL: You silly boring old man? Are you not into LP only? What for? And what the hell you doing with CDs in 21st century? Download USB, you get a hell lot more for the dollar.  
bobui: Yeah right! Hate the fxxking tech. Always more convenient for sure worst sound. So what the hell you doing with that Voyd and Omega anyway? Look, you have zero space in this bloody small room. Lucky there is no boom boom bass here.  
BIL: i have bloodly nothing in the other room which is even larger than here.  
bobui: You had it all long long ago, Kef 107, Tannoy D700, now the 802. And then of course you went side way and got stuck on this money sucking AV. Now you want to be back on LP. You brits just have too much time to spare. Cheese, you silly boring old man!  
BIL: I just dont know what to do with amps. I like the valve sound and i need hundreds of watts if i were to shift my 802 to the audio room. Can you build me one?  
bobui: Oh, Piss off! you pulling my leg! What you mean you dont know what to do with amps? Just take out 10k from your savings and you got plenty of choices. I told you valve amp last longer to your ears and the lush sound you never get from modern trans amp.  
BIL: the one thing i so concern is the lack of power from valve amps.  
bobui: oh, you are ancient! Some gangs in HK have tied up a few pairs of CJ monos with Apogee and Meganpan. Not a problem with power at all.  
BIL: So, can you build one for me, 200Watts and good looking like the photos you show me.  
bobui: Oh, Piss off! No chicken, you need to pay la.  
BIL: Chicken.......? you mean small  
bobui: small and ugly looking primitive junior garage put together little creature  
BIL: You can have my Chord in exchange if you can build me a nice looking sounding pair of 200W monos valves.  
bobui: Oh, Piss off! you pulling leg! Over my dead body. I dont sell my stuffs and i dont do exchange. You come to HK and you can borrow mine. You know Alan, the photo guy....... he has gone so mad with his audio now that his horns are so large that his studio flat is actually sits inside of horn speakers! Ha Ha Ha Ha!  
BIL: Brits have so much time spare. You Hong Kong guys have so much money spare!  
bobui: Cheese! Good health to our audio and long live LPs!
bobui
12-09-18
22:09:27
回覆 (174): CD
N802 + Chord + Lexicon Suround Processor...... this is a very high end AV system..... I believe abc also has the Lexicon........  
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Did your b-i-l asked, "Oh why you play with those DIY chicken stuff, get serious man?"
icefox
12-09-18
20:53:51
回覆 (173): CD
N802 + Chord.........  
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Exactly!  
 
Here is the Chordsssssss! Its has five channels. What you just saw from these photos is not really Hi Fi or Lo Fi lor. The 802, the Chord and the Lexicon were parts of my brother in law AV system with a big Sony projector/100 inches auto screen and Blue Ray as the source. There are two B&W mid size rear speakers at the back of the room making up a true 7.1  
 
Well, not bad having the 802 and big Chord for an average home size AV lor. He is seriously considering setting up a proper LP audio system in the other room. He has recently just purchased a Voyd turntable, Omega arm!
bobui
12-09-18
19:31:37
回覆 (172): CD
The PS Audio CD transport and the DAX Decade are just there filling up some spaces in the shelve. Not frequent use at all! Despite a complete lack of attention to the CD source, the sound does come out very good in a room about 15 X 14 feet.  
 
 
 
bobui
12-09-18
19:15:10
回覆 (173): CD
bobui..... try to find my one unit of Leak TL10.
icefox
12-09-18
19:10:10
回覆 (172): CD
N802 + Chord......... oh.... it reminds me of our friend abc2009...... hehe......
icefox
12-09-18
19:09:22
回覆 (171): CD
In case you don’t know what 雞頭 is like:  
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Oh! My goodness! Thanks for enlighten me lor! Ha Ha! OK, Ok, the 雞頭 name must come from the digging action.  
 
Below is my brother in law system in London. B&W802. Yeah, I know what you are thinking. Not very highend, right! Total agree. No question! Just wait and i show you whats hidden.  
 
bobui
12-09-18
19:04:40
回覆 (170): CD
 
 
In case you don’t know what 雞頭 is like:  
 
 
limage
12-09-18
18:55:27
回覆 (169): CD
Oh! I was going to resell and make a big chuck of margins on it to pay for the Fish and Chips and the many pints of Stout lor.  
 
Not until you are out in the juke, you not realise Hong Kong is the best place!
bobui
12-09-18
16:41:04