View Full Version : Further to my umbilical


Bemused
21-09-10, 05:45 AM
So I have probably chosen my connectors.
Thease are to run DC supplys from a PSU to a Dac
Estimate of the supplys is
PSU
1 x R-core / Hacker cap +35/0/-35v @ 10mA
1 x R-core / 1500uF +14/0 @ 20mA
1 x R-core / 2000uF +14/0 @ 10mA
1 x EI-core 860uF +22v/0 @ 5mA
2 x EI-core 860uF +22v/0 @ 10mA
2 x EI-core 860uF +22v/0 @ 15mA
1 x EI-core 1000uF +22v/0 @ 20mA

Umbilical
Diy 10 twisted pairs of 7/0.2mm - 0.22mm˛, overall braided screen.
Using RS491-380 & 494-330 connectors both ends.

In the Dac
Supply termination strip on a diy etch board using RS 220-4260 terminals.

Loads
STR +15/0/-15V
All the remaining loads are fleas.

I anticipate adding some capacitance to the termination strip which is were I have little idea.
My feeling is for 20uF Tant // 0.1uF Film per rail.
I could add in a little series R if its thought to be benificial.

Do you guys think this capacitor arrangment / value is ok?

Thanks
Tony

martin clark
21-09-10, 12:48 PM
Frankly either /or will work fine.

Since 100nF - 1uF is a convenient size for film caps I often use those and forget it. No need to go mad on size or complication, it's before the final reg(s) and only serves to bypass its input (present a low source impedance at HF). But 10uF of even the very cheapest electrolytic is preferable to nothing.

The resistance in the umbilical and connectors is useful enough on its own, unless you are proposing short fat cables, a 3-pin reg offboard feeding a film cap at the far end (hint, bad idea..). If there are supply volts to spare you can deliberately add a larger resistor based on allowable Vdrop and a bigger local cap, which definitely helps suppression of noise from all sources. Obvius example is Naim's approach to shared or offboard supplies (27R/47uF (http://www.acoustica.org.uk/t/naim/317_%20RC_filter.html)) but DPA similar things did in their original preamps, and very many others too.

Bemused
21-09-10, 01:01 PM
Thanks Martin, all regs are at the far end