Home made XLR cable phantom power problem

[evolver]

So -- i have never run into this problem before and was wondering if anyone might have some insight that could help me out. I put together some xlr cables the other night with canare starquad and neutrik connectors. they work fine in the following circumstances:

1) connected to my motu 828 preamps directly with phantom/condensor mic
2) connected to my motu 828 preamps directly with a dynamic mic
3) connected to my Seventh Circle Audio pres with a dynamic
4) connected to my Sytek MPX with a dynamic

Both the Sytek and seventh circle do not pass phantom over these cables, but for some reason the 828 does. Also, when i test the 828 with my multimeter i get a steady 48v. When i use a monster cable on the SCA and Sytek i get a steady 48v, but my custom cables pass nothing.

I tried wiring the cables with two of the wires being soldered together as a ground for pin 1 -- when that didn't pass phantom, i rewired the cables so that each of the two colored wires were soldered together and to pin 2 and 3, and the shield was soldered to Pin 1.

What could be going on that would allow the Phantom to pass from the Motu but not the Sytek and SCA pres ?

edit: admin: could you change the title to home "made" please --- i missed my silly typo.

[Matt Syson]

Hi
Shield is pin 1 OK. ALWAYS
Two of the diagonal opposing wires in the quad go to pin 2.
The other two wires go to pin 3,
Repeat at the other end and it will work.
It sounds as if you have got yourself into a muddle somewhere, perhaps the numbers are so small you have misread them?
Matt S

[Toolbag]

did you mix up the pins? When soldering (if you have them both in the vice at the same time), the pin on the left on the male goes to the pin on the right of the female - that is if you have them both sitting in the vise like this: ^ ^


Of course, if you have them like this ^ v then the right pin connects to the right pin, left to left

[evolver]

Originally Posted by Matt Syson

Hi
Shield is pin 1 OK. ALWAYS
Two of the diagonal opposing wires in the quad go to pin 2.
The other two wires go to pin 3,
Repeat at the other end and it will work.
It sounds as if you have got yourself into a muddle somewhere, perhaps the numbers are so small you have misread them?
Matt S

when you say two of the " diagonal opposing wires" do you mean take one blue and one white and treat that as, say, the hot wire, then take the other blue and white and treat that as the cold wire ? then i wire the same "pairs" to the respective pins on the opposite end ?

if so then i did this (my third possible configuration of the wires ) and i STILL get phantom from the Motu and no Phantom from the Sytek using these cables -- phantom works on a commercially made cable.


by the way, i have to believe i have it mostly correct as these cables work a-ok with a dynamic mic (ie signal IS passing through them).

[evolver]

Originally Posted by Toolbag

did you mix up the pins? When soldering (if you have them both in the vice at the same time), the pin on the left on the male goes to the pin on the right of the female - that is if you have them both sitting in the vise like this: ^ ^


Of course, if you have them like this ^ v then the right pin connects to the right pin, left to left

i don't *think* i mixed the soldering up -- i used the multimeter to test them and all the pins are connected to their correct destination on the end. i also get signal through on a plain old dynamic -- just no phantom power on the SYTEK -- but i do get phantom on the motu.

[tINY]

Check for continuity between Pin 1 and the metal shell.

What connects to this shell inside the units can vary (also check for shorts of the other pins to that shell).



-tINY

[evolver]

Originally Posted by tINY

Check for continuity between Pin 1 and the metal shell.

What connects to this shell inside the units can vary (also check for shorts of the other pins to that shell).



-tINY

hey tiny

by shell, you mean the barrel of the XLR connector on the cable, not the case of the preamp correct ?

[Rick Sutton]

When you checked for continuity with a multimeter did you also check for shorts between the pins? Also, are you reading the numbers on the xlr's when you check with the meter? I made a trip to help out another studio with a wiring problem and it was all caused by wiring done without constant double checking of the numbers on the connectors...it's a very common mistake.

[evolver]

Ii set up my experiment one last time -- tried my new cables on the motu 828's pres --- had phantom -- tried them on the SCA and Sytek -- no phantom. I then proceeded to completely desolder both cables and remake them (second complete remake).

.... phantom power was available from all three units. yay!


i would love to know how it is that the 828 was able to provide phantom over my (obviously poorly made) cables every time, but i did something subtly wrong that stopped the SCA and Sytek with my first make, and my first attempt to remake.

thanks for the advice -- i think *maybe* i might have had a short i didn't notice, but the advice on here to watch for shorts made me extra careful to pay attention this time. so your advice was not offered in vain.

[tINY]

Originally Posted by evolver

Ii set up my experiment one last time -- tried my new cables on the motu 828's pres --- had phantom -- tried them on the SCA and Sytek -- no phantom. I then proceeded to completely desolder both cables and remake them (second complete remake).

.... phantom power was available from all three units. yay!


i would love to know how it is that the 828 was able to provide phantom over my (obviously poorly made) cables every time, but i did something subtly wrong that stopped the SCA and Sytek with my first make, and my first attempt to remake.

thanks for the advice -- i think *maybe* i might have had a short i didn't notice, but the advice on here to watch for shorts made me extra careful to pay attention this time. so your advice was not offered in vain.

It's hard to tell now, but I bet you had a short from Pin2 or Pin3 to the shell. Sometimes the shell is grounded at the mic input to a pre-amp and sometimes it isn't. Motu probably doesn't (just have a good EMI snubber). Smaller, old-school style manufacturers are likely to ground the shell for shielding...




-tINY

[mixedupsteve]

Its also possible that your ground connection on the cable wasn't good. Some pres have the chassis grounded and the audio grounded to the same place. So a pre like that would still have a ground for the dc phantom power to work with through the chassis ground. Some pres have the chassis grounded but the audio ground has a cap between the chassis grd. and the audio common. Those types of pre would have to get the dc ground through pin 1 of the cable for their phantom.

[Old Goat]

Not quite OT--should I jump the 1 to the shell in XLR connectors?

[Rick Sutton]

Originally Posted by Old Goat

Not quite OT--should I jump the 1 to the shell in XLR connectors?

I don't.

[tINY]

Originally Posted by Old Goat

Not quite OT--should I jump the 1 to the shell in XLR connectors?

That's not considered good practice. If the shell is floating, then the tab connects to chassis ground and works as a shield. If you ground the chassis through the ground reference at a sensitive input, you could run into trouble.

Go with the grounding scheme of the equipment, don't provide bridges with out a good reason (and most of us don't make our own gear anymore anyway).




-tINY