給我一台線性電源

DigitalMana

張東尼@FB 發表於 2017-9-12 12:16
Measurement method probably very different.

If switching power supply is so good then no one will ...

Well DC is DC, whether it is 5/9/12V.  Ideal DC means NO ripple noise, or no AC noise.

In other words, every voltage has 2 components, DC + AC

By filtering out the DC component of the voltage, we left with the AC component which is the "noise/ripple" that we are concerning about.  It is this AC component causing bad sound.

So one can compare all the power supply's absolute noise/ripple (AC) voltage side by side, even they are of slightly different DC voltage.  

SamPoon@FB

CKL 發表於 2017-9-12 08:33
Why? I upgraded to the 25W power supply. 25W/5V = 5A, so 4A is safe enough.

What components limit ...

主要因為npn管同線路
確實答案你問偉良,偉良會答你

DigitalMana

CKL 發表於 2017-9-12 12:28
Apart from low frequency analogue noise, SMPS also contains high frequency digital noise that increa ...

agree, most SMPS has those HF spikes. Those are very bad for sound quality.



But looking at iPower's graph, iPower doesn't have any of those, may be this is one of the reason that iPower sound so much better than normal SMPS.

DigitalMana

張東尼@FB 發表於 2017-9-12 12:26
Ok, however 2.5A is marginal for my use.

I want something like 3A to go with my RPi3 which someti ...

agree, it is a bit marginal, you need something bigger

But from my experience RPi2/3 doesn't really use up all 2.5A, normally 2A is more than enough.

張東尼@FB

DigitalMana 發表於 2017-9-12 12:35
agree, it is a bit marginal, you need something bigger  

But from my experience RPi2/3 d ...

I am getting voltage drop warning under heavy load (e.g. playing metal slug).
May be not so much the "A" but the voltage drop itself.
Even the Apple 12W (i.e, 2.4A) is having this issue.
Had tried both 2.4A rated usb cable & 3.0A rated copper usb cable.

張東尼@FB

CKL 發表於 2017-9-12 08:33
Why? I upgraded to the 25W power supply. 25W/5V = 5A, so 4A is safe enough.

What components limit ...

my hunt continue

SAnalogue

一台好聲既線性電唔係咁簡單...
除左RIPPLE (AC) NOISE外...還有很多參數需要考慮, 如阻抗, 頻寬等...
一般IC (如78xx, 108x, LT30xx) 形式做的線性電 雖然易做價錢便宜...
但都唔會做到 HIGHEND 好聲...

SAnalogue

張東尼@FB 發表於 2017-9-12 17:21
my hunt continue

78xx 系列IC　穩壓，　規格標輸出１。５Ａ
http://www.st.com/content/ccc/re ... s/en.CD00000444.pdf

但實際情況更必須打些折扣

Hungmo

張東尼@FB 發表於 2017-9-12 13:33
I am getting voltage drop warning under heavy load (e.g. playing metal slug).
May be not so much t ...

Metal Slug?

張東尼@FB

SAnalogue 發表於 2017-9-12 17:49
78xx 系列IC　穩壓，　規格標輸出１。５Ａ
http://www.st.com/content/ccc/resource/technical/document/ ...

你意思 IAMD 都去唔到 4A ?  佢係 80瓦A级变压器.

https://world.taobao.com/item/52 ... 1.18.45c5a63fMZu2Eh

張東尼@FB

Hungmo 發表於 2017-9-12 18:14
Metal Slug?

Yes.
123456

SAnalogue

張東尼@FB 發表於 2017-9-12 18:24
你意思 IAMD 都去唔到 4A ?  佢係 80瓦A级变压器.

https://world.taobao.com/item/525221374183.htm?spm ...

看結構這是分立式穩壓電源...不是78xx 系列的ic 穩壓...
光看用料及手功...其質素小弟不予置評..但在這價格實在不能要求太多
想知它能不能供應它聲稱的12v 4a...很簡單...只要調至12v 時用3 ohm 電阻做loading
先不理會其輸出的noise...我估計電壓會掉得很嚴重....而且...用這樣小的機箱面積散熱....不用3分鐘就熱到飛起...4a 電流所產生的熱量決不野少.....

做4A Load 兩小時功率管 及 電阻 應該會燒毀

張東尼@FB

SAnalogue 發表於 2017-9-12 19:02
看結構這是分立式穩壓電源...不是78xx 系列的ic 穩壓...
光看用料及手功...其質素小弟不予置評..但在這價 ...

照理我又用唔至 4A.  我估 2.5A ~ 3A under heavy loading.  
咁我買 ipower 算數.

edison133

LPS要做得好真係不易的!
要上到5A及穩定輸出PCB及元件散熱已要求非常高了。

edison133

DigitalMana 發表於 2017-9-12 12:03
5.6mV (LPS) vs 1uV noise (iPower), 相差5600倍，你自己決定

1mV = 0.001V

hahahaha it is funny report!

edison133

以下測試片是我做的希望比到大家多D了解!

https://www.facebook.com/ediscreation/videos/1506876299353553/

https://www.facebook.com/ediscreation/videos/1506876299353553/

CKL

張東尼@FB 發表於 2017-9-12 17:21
my hunt continue

Studer900 should support 5V/4.5A, from here:
http://www.ebay.com/itm/25W-Tale ... ER900-/112114160969

ackcheng

我用這個
https://www.belleson.com
不錯的選擇

張東尼@FB

CKL 發表於 2017-9-12 21:17
Studer900 should support 5V/4.5A, from here:
http://www.ebay.com/itm/25W-Talema-Linear-Power-Suppl ...

That one only has 1 DC output.
I am not sure if it is more difficult to get 4.5A on an USB port.

張東尼@FB

ackcheng 發表於 2017-9-12 21:22
我用這個
https://www.belleson.com
不錯的選擇

Looks like diy.