How do you make a power supply umbilical cord?? - diyAudio
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Old 14th January 2003, 06:33 PM   #1
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Default How do you make a power supply umbilical cord??

Hi,
Im looking for advice for building the power supply umbilical cord to connect my BOSOZ to its power supply. Im also making a DAC that has a separate power supply.

From reading about the DAC "UC", Ive read that it may be best to use coax for the power feeds: analog +/- and then digital supply in separate wire braid sheilded sheaths.

Is this correct....if so what mini-coax should I use??? 50 ohm or 75 ohm????

The connected DAC will have on board regulators of course.
The BOSOZ will not. I have a raw power supply that will connect to Nelson's preamp boards. What is the drawback of not having "co" regulation...for the incoming power feeds? The cord will only be about a 1.5 feet.
How should I implement the BOSOZ umbilical cord??? Should I use coax or should I use twisted pair wire?? What guage wire???
Thanks!!!!
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Old 15th January 2003, 02:06 AM   #2
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Uh...which question did you want answered first?
I'm fond of twisted pair, myself. Self-shielding, inexpensive, effective. Unfortunately, it's not as tidy as coax. Either will work.
Keeping analog and digital separate is a good idea.
Unless you've got a good reason otherwise, I'd vote for regulation as near the BOSOZ circuit as you can get.

Grey
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Old 15th January 2003, 02:17 AM   #3
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Default I dont think I have enough real estate in my preamp chassis

Grey,
Thanks for the reply!!

I dont think I have enough real estate in my preamp chassis to do this. Can you recommend a way of doing this in a small footprint. Im using two NP BOSOZ power supply boards with alot more caps in a separate box that will feed the preamp chassis.

Whats the drawback of not doing regulation alongside the preamp boards in the preamp.

What guage of wire would you use?


Thanks for your help!
Tom
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Old 15th January 2003, 03:44 AM   #4
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Want a minimalist regulator? Look at Nelson's Zen part 3(?). Scale it down, current-wise. Low parts count also means small footprint.
16 or 18 ga wire should be super. Even 20 would do. It's not as though you're carrying huge amounts of current. I wouldn't go below about 24 ga. unless I was desperate.
Regulation away from the circuit tends to be one of those things that works, but somewhat less than perfectly. You lose some voltage to the resistance in the wire. You run the risk of picking up RF (the regulator would filter this out [hopefully] if it were between the RF and the circuit). You lose accuracy in maintaining voltage if you're using a circuit that corrects for voltage sags and such. Nothing huge--just a grab bag of niggling little things that will annoy you half to death.

Grey
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Old 15th January 2003, 05:47 AM   #5
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I like to use Kimber 4TC speaker cable as a umbilical cord. It is also self shielding. It has 8 x 19ga. wires and it's perfect for two channels of gainclone from a shared supply.
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Old 15th January 2003, 11:56 AM   #6
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I also like twisted pair as an umbilical cord for its simplicity. To keep the RF and hum pickup to a minimum with a remote supply, I usually add a small electrolytic (1000 uf) capacitor, bypassed with a 0.1uf mylar or polypro capacitor. I would not lose much sleep on the resistance in the cable with the low amperage requirements of a preamp. I think the biggest challenge is making sure the connectors work well as that is often the biggest souce of failure and RF pickup (from bad solder joints, poor contact, etc.). I would use gold plated contacts as oxidation is a great way to form a rectifier for RF detection.

PaulyG
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Old 15th January 2003, 07:14 PM   #7
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Thanks everyone for the help!!!

For my DAC, Ill probably go with coax. Any recomendations on any prefered coax?? I probably wont go with mini-coax....any suggestions??

My pickle is what to do with my BOSOZ. Thanks Peter for the Kimber suggestion....it did not dawn on me.....great idea.
Im using goldplated Neutrik DIN connectors for the chassis and cord.

My initial plan was to have transfomers, diode bridge, extra caps feeding the BOSOZ power supply boards in the same box. Can I take the output of this regulated supply>>>>>umbilical cord>>>to the preamp chassis box/boards that has second regulation circuit b4 it hits the preamp???? Ill lose a few volts with the double regulation....any other problems with this???
Do I have to modify anything on the BOSOZ power supply boards?? that will feed the second regulation circuit colocated in the preamp. Will losing a few volts be a problem????

Thanks!!
Tom
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Old 15th January 2003, 07:27 PM   #8
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Jon Risch appears to be the guru of DIY cables. His website is: http://www.geocities.com/jonrisch/s2.htm

He has all kinds of interconnects and speaker cables. Also check www.audioasylum.com and search for Risch.

For coax, he likes Belden #89259, which is a teflon insulated copper core, copper shielded cable.

IMHO. I think double regulation is probably overkill as class A current draw should be relatively constant and the sub 1 ohm resistance in the power cable should not really affect things too much.

-PaulyG
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Old 16th January 2003, 01:14 AM   #9
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That was my thinking on the BOSOZ, but everyone I talk to agrees with the dictate that I regulate close to the circuit. Which I much agree with except that Im not sure if I have physical space.

Can anyone comment on already built BOSOZ w/separate power supply enclosure. Have they implemented this with or without "colocated" regulation.

How about the "double regulation"??? Anyone else please comment.

Besides the voltage loss, stray noise, etc.., what are other problems (line sags ??) that the BOSOZ would have if implemented without regulation close to the circuit???

Thanks for all the help!!! Ive built the BOZ preamp a few years ago and am about to build some Aleph amps.......Ive got a engineering background.......but I have soooooo much to learn
Rave On Nelson Pass
Tom
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