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electrical hum
 

offline sadist from the dark side of the moon on 2007-01-21 08:18 [#02035490]
Points: 8670 Status: Lurker



yesterday i played this gig before murcof and i realised
one terrible thing in my laptop - when i connected it to the
mixer some terrible hum and squeek came through which i
couldn't get rid off.

the problem was solved taking out the power adapter but my
battery would last max about 15 minutes.

murcof himself told me i should buy a di-box.

but the someone told me about something called
"ferryt-filters" which are just some weird rings that you
put on the cable of the power supply and it should work
fine...

anyone knows something about this ?


 

offline wizards teeth from Newcastle (United Kingdom) on 2007-01-21 08:27 [#02035493]
Points: 1070 Status: Regular



some info about the rings you talk of

http://www.goaskalice.columbia.edu/2318.html

teeth


 

offline Ophecks from Nova Scotia (Canada) on 2007-01-21 08:29 [#02035494]
Points: 19190 Status: Moderator | Followup to sadist: #02035490 | Show recordbag



If Murcof was a real friend, he'd have given you his di-box.


 

offline woj on 2007-01-21 08:29 [#02035495]
Points: 468 Status: Regular



no generalnie zasilacz powinien miec na kablu, najlepiej
przy samej wtyczce do laptopa okragly filter dookola tak jak
TU


 

offline Ophecks from Nova Scotia (Canada) on 2007-01-21 08:31 [#02035497]
Points: 19190 Status: Moderator | Followup to wizards teeth: #02035493 | Show recordbag



''Ball by ball, the testicles go through''

I didn't know you slid them over the testicles. I'm really
uninformed when it comes to cock rings.


 

offline sadist from the dark side of the moon on 2007-01-21 08:33 [#02035499]
Points: 8670 Status: Lurker | Followup to woj: #02035495



o kewl thanks i wondered on which cable i would have to
place it.


 

offline stilaktive from a place on 2007-01-21 08:42 [#02035502]
Points: 3162 Status: Lurker



yeah mine does it too. it usually helps to wiggle the wire
round a little bit.

then again my laptop cn last 4 hours without acnd thast much
longer then anything ill ever do live.


 

offline sadist from the dark side of the moon on 2007-01-21 08:44 [#02035503]
Points: 8670 Status: Lurker



it was really horrible - i hope i get rid of this soon
because you could even hear my mouse moves in very silent
moments.


 

offline chaosmachine from Ottawa (Canada) on 2007-01-21 08:45 [#02035504]
Points: 2330 Status: Lurker



sounds like a ground loop. this can happen, for example,
if you're running connected electronics off two different AC
circuits.


 

offline dave_g from United Kingdom on 2007-01-21 08:58 [#02035506]
Points: 3372 Status: Lurker



Those rings are ferrite rings. They are wrapped around the
DC cable to power the laptop and work by eliminating AC
components.

The laptop has a small box which connects to the mains. Then
the box has another cable which connects to the laptop. It
is the cable that goes to the laptop which needs to be
looped through the ferrite rings.

If the mixer has a "ground lift" feature, you could try
using that if the problem is with ground loops.


 

offline sadist from the dark side of the moon on 2007-01-21 09:03 [#02035508]
Points: 8670 Status: Lurker | Followup to dave_g: #02035506



no ground loop option...

so if i understand corectly i have to make a loop from the
cable over the ferrite ring and not just clamp it on the
cable?


 

offline dave_g from United Kingdom on 2007-01-21 09:10 [#02035511]
Points: 3372 Status: Lurker | Followup to sadist: #02035508



depends on the type of ring. Some have hinges and clip over
the cable, others are larger rings where you loop the cable
through it as many times as you can.

You can also modify your audio cables to lift the ground.
For example you can paint over the ground contact on one end
on each cable you use. Don't do it on both ends or the cable
will be unsheilded. If you do it on one end, the cables are
grounded on one end so the shielding works, but the ground
connects through the AC ground connection only, not through
the cables sheild as well.
This way the loop is broken, but the signal levels still
work because the 0V refererence level goes via the AC ground
instead of the audio cable ground.
This is effectively what a ground lift switch on a mixer
does.

BTW make sure you NEVER take out the AC ground connection or
else you can die, its an essential safety feature.


 

offline sadist from the dark side of the moon on 2007-01-21 09:17 [#02035514]
Points: 8670 Status: Lurker | Followup to dave_g: #02035511



will such a ferrit ring get rid a 100 % of the problem or
would a direct box be the better (but about 50 times more
expensive) solution


 

offline dave_g from United Kingdom on 2007-01-21 09:28 [#02035518]
Points: 3372 Status: Lurker | Followup to sadist: #02035514



dunno. try the cheap one and if that doesn't work try the
more expensive one!



 

offline futureimage from buy FIR from Juno (United Kingdom) on 2007-01-21 09:56 [#02035528]
Points: 6427 Status: Lurker



I bloody hate hum, especially when I'm DIYing a synth and
getting it from BATTERIES!!!


 

offline dave_g from United Kingdom on 2007-01-21 10:07 [#02035537]
Points: 3372 Status: Lurker | Followup to futureimage: #02035528



That's poor shielding then, or some other kind of pickup.
That's not conducted interference (ground loops) but
radiated (pickup), unless you are getting nasties coming up
the audio cables, but that can be cured quite easily with
the whole ground lift thing.

Since you are into DIY, here is another tip....
If you ever make a diy phaser with light dependant
resistors, make sure that it is properly contained in a box
so no outside light gets on them or else your signal is
modulated by the light bulbs in the room to give a 100Hz
buzz. (100Hz cos light bulbs light on both halves of the
50Hz sinewave).


 

offline EVOL from a long time ago on 2007-01-21 10:42 [#02035554]
Points: 4921 Status: Lurker | Followup to dave_g: #02035537



that's just good advice everyone should know.


 

offline sadist from the dark side of the moon on 2007-01-21 11:13 [#02035564]
Points: 8670 Status: Lurker | Followup to dave_g: #02035537



do you think it would be difficult to make a di-box diy ?


 

offline futureimage from buy FIR from Juno (United Kingdom) on 2007-01-21 12:07 [#02035579]
Points: 6427 Status: Lurker | Followup to dave_g: #02035537



Yeah, I think it was a bit of both to be honest, could've
been amplifying my (already dead) signal too much = NOISE.

I'd always put vactrols in a very very very darker than dark
box anyway.

Sadist: I would have thought it would be pretty easy.
Depends if you want phantom power or not.


 

offline JAroen from the pineal gland on 2007-01-21 13:17 [#02035611]
Points: 16065 Status: Regular | Followup to dave_g: #02035537



not to be a nitpicker, you seem knowledgable and im
curious..

isn't it true that you only get interference from tube
lights? the wire in regular light bulbs cools down too
slowly, you can't see the sine wave that way.


 

offline Taxidermist from Black Grass on 2007-01-22 06:20 [#02035862]
Points: 9958 Status: Lurker | Followup to sadist: #02035564



Here is a little bit of a review for some DI boxes of
various price range. This website is all round pretty good.

DI


 

offline sadist from the dark side of the moon on 2007-01-22 06:31 [#02035864]
Points: 8670 Status: Lurker



just to clear things up:

i realised that the direct boxes convert a signal from a
jack input to xlr.

but what if i need to connect it to a mikser that has only
chinch inputs?

would soldering such a connection (xlr-chinch) work?


 

offline big from lsg on 2007-01-22 07:12 [#02035872]
Points: 23728 Status: Lurker | Show recordbag



don't you just need a grounded plug


 

offline sadist from the dark side of the moon on 2007-01-22 07:15 [#02035875]
Points: 8670 Status: Lurker | Followup to big: #02035872



yeah but where to ground the audio interface?


 

offline Ezkerraldean from the lowest common denominator (United Kingdom) on 2007-01-23 16:15 [#02037022]
Points: 5733 Status: Addict



yep. connecting laptop to the mains causes the buzz. the
buzz is the 50hz AC mains. i dont know how to get rid of it,
but i know how it happens. just get a better battery. or
there must be some way you can filter out the buzz. dunno
like innit


 


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