Grounding Problem/落地問題

你個底板的地已經有輸出處和機箱連在一起，輸入的地亦落了地，因和輸出連在一起。請問原來有 dee dee 聲是如何接的。

[quote:9155613bc1="alfcat"]Dear Accphoto,

Original Design:

1. Signal In using silver plated copper wire, NOT coaxial. Signal (L+R) into Volume Switch L,R in. Volume Switch GND goes to PCB GND.

2. Volume GND just goes to PCB GND. No extra wire going to chasis.

3. 13A plug GND goes to Signal in / out common GND (the thick copper wire), not to the chasis.

CAT[/quote]

咁你係地連水線，無落機箱地，90% dee dee 聲......
另外輸入，和輸出線最好用 co-ax, co-ax 線在輸入端接地，另一處空接，這樣不會有 gound loop.
你的 dee dee 聲是因為你機箱無落地，所以 dee dee 聲。
做前級,我通常在輸入端連水線跟機箱接,然後連 volume 地和 pcb 地。 Output 地連 pcb 地但不會接機箱。
做後級則真接在 power  -Ve 處落地。

GND is something that normal connect to the metal part of the building .
Neutral  is 火線的回路，completely different.

USA power supply  has GND, look at the "real" USA plug. There is a ground.

I do not Japan power supply had gound or not.

Some equipment will normal gound to Chasis only, this should be ok but gound to "GND" wire will normally has a slient background.

For CO-ax socket, normally , I will solder the  -Ve to gound on  socket side and the -Ve  is not connected on other end.

其實師父以前教落，Co-ax cable 只 ground 一面因為 ground 兩面會有 Ground Loop, ，那一面就看每個人喜好，我兩面都試過，發覺 ground RCA socket 那面噪音小點，你可自已試試。

I just finished my SP-10 last Sunday. For grounding, here is some tricks :
1. Use input gound to connect to the chasis and earth wire.
2. For the input wire, it is better to connect only one side, I use the volume gound as the connecting point for the gound.
3. All power supply negative connect to the gound wire,

No more "dee dee" sound in my case.

Enjoy your DIY work.....  

SHow your circuit before I can comment on it. 150ma should be good enough for a lot of application. Most per-amp will only take 10ma and some take up to 20 ma. Even a 300B poweramp will take about 80ma per channel.  It should not be any problem for you to use 150ma choke on 100ma transformer but not  the reverse.