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Long DC cable

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Posted on October 5, 2023 at 09:16:24
Maril555
Audiophile

Posts: 262
Location: Philadelphia
Joined: March 9, 2004
 I need to make a longer DC cable for the linear PSU that feeds TT motor, as it induces hum in SUT/Phono stage being 3 ft away from the SUT/Phono.
Moving it away about 5-6 ft. dramatically reduced the hum.
The problem is that is order for the PSU to be in an acceptable location, the DC cable needs to be at least 10-15 ft long.
So I'm wondering if there any downside to having a long DC cable (15 ft)?
Thank you

 

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RE: Long DC cable, posted on October 5, 2023 at 10:50:02
6bq5
Audiophile

Posts: 4278
Location: SF Bay
Joined: August 16, 2001
 just pay attention to wire gauge for voltage drop - though I am sure that even at 20' you should be ok-
Happy Listening

 

RE: Long DC cable, posted on October 5, 2023 at 15:15:18
zacster
Audiophile

Posts: 2115
Location: NYC
Joined: November 22, 2003
 Maybe try some shielding on what you have.

 

An option, posted on October 6, 2023 at 10:45:22
Fluter
Audiophile

Posts: 110
Location: MI
Joined: August 11, 2019
 To avoid any inadvertent hum induction via the DC supply, you could also try a 4-wire star-quad configuration. This would have the additional benefit of increased current delivery capacity as well, depending on your specific choice.

 

RE: An option, posted on October 6, 2023 at 18:24:25
Maril555
Audiophile

Posts: 262
Location: Philadelphia
Joined: March 9, 2004
 Thats what Gotham GAC-1 is, Star Quad
So, to be clear two red wires connected to center pin and two white ones to the barrel?

 

Yep, posted on October 6, 2023 at 18:44:15
Fluter
Audiophile

Posts: 110
Location: MI
Joined: August 11, 2019
 Yes, as simple as that. Check out the following for more info...

 

I would also add a capacitor, posted on October 12, 2023 at 03:03:51
1973shovel
Audiophile

Posts: 10053
Location: Greenville SC
Joined: February 25, 2007
 ...say several thousand microfarads worth, with an adequate voltage rating, where the cable terminates at the turntable motor.

 

RE: I would also add a capacitor, posted on October 12, 2023 at 10:42:28
Maril555
Audiophile

Posts: 262
Location: Philadelphia
Joined: March 9, 2004
 Could you explain this, please?

 

Sure, but before I do, posted on October 13, 2023 at 09:31:56
1973shovel
Audiophile

Posts: 10053
Location: Greenville SC
Joined: February 25, 2007
 You list a TechDas Air Force 3 as your turntable in your system, but according to a 2018 TAS review, the TechDAS has an "AC synchronous motor". So is this DC cable for a different table? If so, maybe you could include a picture or two where the DC cable terminates at the table, and we can go from there. Thanks.

 

RE: Sure, but before I do, posted on October 14, 2023 at 05:06:37
Maril555
Audiophile

Posts: 262
Location: Philadelphia
Joined: March 9, 2004



TechDas been gone for a while. Now it's SpJ a Luce with Dereneville DAE-01 motor,
Which is DC and takes DC 2.1 connector

 

Nice!, posted on October 14, 2023 at 12:14:38
1973shovel
Audiophile

Posts: 10053
Location: Greenville SC
Joined: February 25, 2007
 Then I would add a radial lead cap at the 2.1 mm DC barrel connector, being sure to observe correct polarity and voltage requirements. A low ESR,
1,000 uF Nichicon will work, and cost you less than $1

What are you using for a DC power supply? There's possible room for improvement there, depending on what you're using.

 

RE: Nice!, posted on October 14, 2023 at 12:27:25
Maril555
Audiophile

Posts: 262
Location: Philadelphia
Joined: March 9, 2004
 Could you provide some details on how to connect that resistor?
And what purpose does it serve?
I'm using Hewlett- Packard E3616A Linear Power supply.
I've tried a few "audiophile-grade" LPS before and all of them hummed more than the HP.

 

I didn't suggest a resistor, posted on October 14, 2023 at 18:52:03
1973shovel
Audiophile

Posts: 10053
Location: Greenville SC
Joined: February 25, 2007
 I suggested a capacitor near the load, at the end of your fifteen foot DC cable. This would be to further reduce supply ripple/noise. The configuration would be standard, positive to positive, negative to negative.

You may not even need it, but as noted, they're only about $1.



 

RE: I didn't suggest a resistor, posted on October 15, 2023 at 04:44:12
Maril555
Audiophile

Posts: 262
Location: Philadelphia
Joined: March 9, 2004
 I meant "capacitor"

 

I was just making sure we were on the same page (nt), posted on October 15, 2023 at 07:36:34
1973shovel
Audiophile

Posts: 10053
Location: Greenville SC
Joined: February 25, 2007

 

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