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[CAS] 給我一台線性電源

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發表於 2017-9-11 19:41:40 | 顯示全部樓層 |閱讀模式
首先我要知道 Raspberry Pi 3 需要多少電流:
https://www.pidramble.com/wiki/benchmarks/power-consumption

以前我喜歡用LT1085 DIY, 原來是浪費時間.
我有一台 Paul Hynes SR1 9V/1A, 熱得像 class A 後級一樣, 用了八年多 24x7 還未燒壞腦.
今天我的選擇是 Studer900. ps.jpg

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 樓主| 發表於 2017-9-11 19:42:11 | 顯示全部樓層
本帖最後由 CKL 於 2017-9-12 09:56 編輯

ps.2.png
ps.2.jpg
發表於 2017-9-12 00:35:28 | 顯示全部樓層
你呢隻偉良版Studer900行唔到3.5a最多1.8a
發表於 2017-9-12 07:30:16 | 顯示全部樓層
I.AM.D 個隻又如何?
 樓主| 發表於 2017-9-12 08:33:04 | 顯示全部樓層
SamPoon@FB 發表於 2017-9-12 00:35
你呢隻偉良版Studer900行唔到3.5a最多1.8a

Why? I upgraded to the 25W power supply. 25W/5V = 5A, so 4A is safe enough.

What components limit its output to 1.8A? I don't understand.
發表於 2017-9-12 09:10:47 | 顯示全部樓層
 樓主| 發表於 2017-9-12 09:25:09 | 顯示全部樓層
張東尼@FB 發表於 2017-9-12 07:30
I.AM.D 個隻又如何?

The power supply is using 7805 as the regulator.
According to this datasheet:
http://www.st.com/resource/en/datasheet/l78s.pdf
It is a 5V/2A regulator. When input is 10V, load is 500mA, the output noise voltage is 40uV, very good. I am surprised that an old 7805 has such a good value. iamd.jpg
發表於 2017-9-12 09:27:18 | 顯示全部樓層
CKL 發表於 2017-9-12 09:25
The power supply is using 7805 as the regulator.
According to this datasheet:
http://www.st.com/re ...

5V2A ?  The seller told me 4~5A when I asked him yesterday.

I want at least 3A for my RPi3.
 樓主| 發表於 2017-9-12 09:27:33 | 顯示全部樓層
張東尼@FB 發表於 2017-9-12 09:10
https://world.taobao.com/item/520731611524.htm?fromSite=main&spm=a312a.7700824.w4002-15260864961.31 ...

The noise shown is 5.6mV.
 樓主| 發表於 2017-9-12 09:33:15 | 顯示全部樓層
張東尼@FB 發表於 2017-9-12 09:27
5V2A ?  The seller told me 4~5A when I asked him yesterday.

I want at least 3A for my RPi3.

According to here:
https://www.aliexpress.com/store ... 65_32487451197.html

There are two outputs. The primary output is 32V/8A and the secondary is USB 5V/2A.
發表於 2017-9-12 09:38:18 | 顯示全部樓層
CKL 發表於 2017-9-12 09:33
According to here:
https://www.aliexpress.com/store/product/I-AM-D-LPS200-Linear-Power-Supply-For- ...

https://world.taobao.com/item/52 ... 08.3.7407e6bexIGTgs

U can pick the different voltage 5V/9V/12V...

I believe he was referring to the 5V model.
 樓主| 發表於 2017-9-12 09:48:16 | 顯示全部樓層
張東尼@FB 發表於 2017-9-12 09:38
https://world.taobao.com/item/525221374183.htm?spm=a312a.7728559.2014082608.3.7407e6bexIGTgs

U ca ...

According to your link, there is only one output. So, 5V with 4-5A is absolutely possible. Could you ask the seller about the output noise voltage?
發表於 2017-9-12 10:27:50 | 顯示全部樓層
CKL 發表於 2017-9-12 09:48
According to your link, there is only one output. So, 5V with 4-5A is absolutely possible. Could y ...

Capture.JPG
發表於 2017-9-12 10:42:29 | 顯示全部樓層
Another question is if LPS is really better than iPower?
發表於 2017-9-12 11:57:53 | 顯示全部樓層
老虎魚 LPS stable !!!!

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發表於 2017-9-12 12:03:56 | 顯示全部樓層
本帖最後由 DigitalMana 於 2017-9-12 12:11 編輯
張東尼@FB 發表於 2017-9-12 10:42
Another question is if LPS is really better than iPower?


5.6mV (LPS) vs 1uV noise (iPower), 相差5600倍,你自己決定

1mV = 0.001V
1uV = 0.001mV = 0.000001V

這裡有兩篇線性電源的測試報告:

http://blog.sina.com.cn/s/blog_1323b8cac0102wtkz.html

http://blog.sina.com.cn/s/blog_1323b8cac0102wv7l.html
發表於 2017-9-12 12:16:09 | 顯示全部樓層
本帖最後由 張東尼@FB 於 2017-9-12 12:22 編輯
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


Measurement method probably very different.

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

From head-fi, the iPower only provides very subtle improvements on the SQ and seems many reports than it dies after few months.  I plan to use if with RPi3 so 2.5A is very marginal.

I will only take a grain of salt with the Sina report.  How do you compare 12V/9V/5V together in the same test.
發表於 2017-9-12 12:20:45 | 顯示全部樓層
本帖最後由 DigitalMana 於 2017-9-12 12:25 編輯
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 ...


Agree with you, most switching power supply (SMPS) is bad, very bad! In fact, horrible!

However, the iPower is a very different beast, it is the only SMPS that I found which is much better than LPS .

In conclusion, from my experience, all SMPS I used are much worst than LPS, except iPower, which is quite a bit better than LPS.

Those links also confirmed my findings, but YMMV as always
http://blog.sina.com.cn/s/blog_1323b8cac0102wtkz.html
http://blog.sina.com.cn/s/blog_1323b8cac0102wv7l.html
發表於 2017-9-12 12:26:58 | 顯示全部樓層
DigitalMana 發表於 2017-9-12 12:20
Agree with you, most switching power supply (SMPS) is bad, very bad! In fact, horrible!
...

Ok, however 2.5A is marginal for my use.

I want something like 3A to go with my RPi3 which sometime I will use it as a PSX1.
 樓主| 發表於 2017-9-12 12:28:17 | 顯示全部樓層
Apart from low frequency analogue noise, SMPS also contains high frequency digital noise that increases the jitters of your audio system. That's why CAS should keep away from SMPS.
smps.jpg
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