Noise

ibenko · Post by **ibenko** » Wed Jul 07, 2004 6:38 am

I am slowly loosing my nerves, I just can't get anywhere by testing. Only computer and preamp plugged into wall outlet are already making noise. Everything else is unplugged. Now I'm thinking about line isolation transformer. I gues this could help, because cutting the ground wire (kind of stupid :>) helped. I read somewhere that DI-box is also transformer. My preamp actually has function of being DI-box, but I guess this doesn't help. Would it help if I would buy aditionall one. Behringer makes those for stereo and for eight channels. I would need one for eight channels, but I think that that one is grounded to, so if I'm not wrong I guess I would get noise again.

Now I'm thinking what about if I would plug Mini disc between preamp and soundcard, I guess this could solve the problem.

Nah, I tried. Same problem

Tnx in advance for your really great answers, I hope we'll find the right answer :>

Best regards, Igor

Post by **garyb** » Wed Jul 07, 2004 2:58 pm

well the di box is not really right because of impedance(it's for going from high to low). you CAN use a good isolation transformer(hum eliminator). here's one:

http://www.hosatech.com/hosa/products/hem-331.html

bassdude · Post by **bassdude** » Thu Jul 08, 2004 7:55 am

Can you post up a recording of the above setup (computer and pre-amp) with noise. I'm curious to hear what kind of noise you're getting?

blazesboylan · Post by **blazesboylan** » Thu Jul 08, 2004 11:56 am

Bassdude:

Noise MP3

ibenko · Post by **ibenko** » Thu Jul 08, 2004 7:05 pm

Tnx blazesboylan!

I noticed today that I also hear movement of my mouse.

Best regards, Igor

blazesboylan · Post by **blazesboylan** » Thu Jul 08, 2004 8:33 pm

Put some cheese and a trap out for it. Just make sure you don't get your fingers caught.

"Squeak squeak!"

Igor, have tried turning on *all* your gear *except* the computer? You mentioned there was even a bit of noise from the K2000. Sounds like the computer may be the worst offender -- but not the only one.

I really do think the earliest suggestions from GaryB, Astroman, et al -- to call in an electrician -- make the most sense at this point. If you can get a friend, or a friend of the family, etc, who is an electrician you should be able to save a few bucks. But just getting them in to check it out (and maybe give you a quote too, if something is wrong) will be worth it in the long run. There are some things even Mastercard can't buy, and sanity is certainly one of 'em.

Incidentally I'm feeling particularly sympathetic today. Was getting hum from an old 2 prong guitar amp last night so decided to turn on one of these 3-way (pin A / pin B / off) ground switches. Zzzzzzzt. My thumb is still freakin' sore from the jolt.

Johann

astroman · Post by **astroman** » Fri Jul 09, 2004 2:58 am

On 2004-07-08 20:05, ibenko wrote:
I noticed today that I also hear movement of my mouse.

the source is almost certainly a bad or too weak powersupply.

@blazesboylan : 'thumbs up' probably wouldn't be appropriate here

luckily you only pushed the switch, but with a guitar strapped on and 'accidently' touching the cable or a metal part with the other hand...

tnx for this vital example

cheers, Tom

[ This Message was edited by: astroman on 2004-07-09 03:59 ]

Post by **garyb** » Fri Jul 09, 2004 4:50 am

grounding is tricky.....

(get a grounded cord on that thing, please)

ibenko · Post by **ibenko** » Fri Jul 09, 2004 8:31 am

OK, tnx for great advices. So I'll try to get an electrician. I don't know about power supply but it's a 350w chieftek one.

Best regards, Igor

astroman · Post by **astroman** » Fri Jul 09, 2004 12:35 pm

chieftec is a cheapo brand - any quality stuff will do.
Must be heavy, quiet (!) and a bit expensive

Good PSUs CANNOT be cheap (due to the parts required) and don't forget:
if it fails (some even prefer to quit service with a nice little explosion of the caps) it may fry anything in your system - including the Scope card(s)

cheers, Tom

blazesboylan · Post by **blazesboylan** » Sat Jul 10, 2004 1:24 am

On 2004-07-09 05:50, garyb wrote:
(get a grounded cord on that thing, please)

I'm the first one to lecture people on that stuff.

I should listen to my own advice sometimes. *Sigh*.

I am deathly afraid of modding guitar amp power supplies myself though. Gotta find a decent repair shop in Victoria...

@Astroman: Nothing lucky about it. 110 volts and god knows how many amps right into my thumb. The thing with these old guitar amps is that the chassis is tied to ground and the ground is switchable. If you push the switch the wrong way, you might as well be sticking a fork in the wall outlet. (Incidentally I know someone who did that, too.)

Needless to say I used a wooden broomstick to switch the ground back to "off".

Grounding isn't difficult unless you're stupid like me!

Cheers & good luck Igor,

Johann

Post by **garyb** » Sat Jul 10, 2004 2:45 am

just solder the two conductors to the same place as the old cable and solder the ground to the chassis is the usual way. you really won't touch the power supply. you will need a pretty stout iron to solder to the chassis. you can get a cable at your local electronics surplus or off of something that doesn't work anymore or an extra computer type power cable(cut it).

what amp is it? most amps will use this method, fenders and the like for sure. some ampegs may be weird.

[ This Message was edited by: garyb on 2004-07-10 03:49 ]

bassdude · Post by **bassdude** » Sat Jul 10, 2004 7:21 am

On 2004-07-08 12:56, blazesboylan wrote:
Bassdude:

Noise MP3

That's RF you're getting there, and not a ground/earth loop so at least you've eliminated that one. A UPS might help if it offers filtering/line conditioning. But that won't help if the RF is being induced into all of your cabling. It's best to track down the source of the noise if you can. Cheap (switching) plug packs, Fluorescant lighting, motors, etc etc.

blazesboylan · Post by **blazesboylan** » Sat Jul 10, 2004 5:01 pm

Bassdude: We've been through it all.

I think we're starting to go in circles.

Tom's suggestion (computer PSU) sounds like the best one I've heard. Though partly because I've never "heard" a bad computer PSU. I think the only other thing Igor hasn't tried yet is bringing in an electrician to check the mains.

(I do agree with you though, it sounded to me like light or monitor interference. But that *is* a ground problem still, since the interference is picked up on the ground cables.)

GaryB: Holy crap! Pardon my French, but you just saved me a trip to the repairman and a solder job.

I have a morbid (and perhaps irrational) fear of capacitors. Of course changing the power supply cord on a guitar amp means getting in close with the power supply. Fortunately the specs indicate that the amp (Dual Reverb Showman) doesn't have any capacitors this side of the transformer.

However I picked up my trusty MagLite to go figure out which model it is that I have (AA270 or AA769). Lo and behold -- there's a three prong power cable input that someone must have added at some point in the past.

So unplug the two prong plug and -- what's this? It's actually a three prong plug! Gaaa! Someone cut the ground pin. I can't believe it. I can't believe I never paid any attention to it before! Typical of me: I don't change my habits until I get burned or electrocuted.

I bought this amp used several years back. I can't believe I never had the presence of mind to fix the freakin' power supply on it. All it would have taken was a 3 prong cord. No soldering, nothing.

Checked all the pins with a multimeter. The modded 2 prong corresponds to the 3 pin socket perfectly, and the chassis is also tied to the three pin socket ground.

Now my only question is: what do I do with the modded two prong power cable? Ain't no way I want those metal prongs sticking out and zapping me... Would a thick dosage of electrical tape provide sufficient resistance to prevent that plug from frying me and my equipment? Or should I cut the connector and tape over the raw wire? (I'll need a bloody chainsaw to cut through that cord...)

Thanks for your prompting GaryB! I love this place...

Johann

astroman · Post by **astroman** » Sat Jul 10, 2004 6:33 pm

On 2004-07-10 18:01, blazesboylan wrote:
... Though partly because I've never "heard" a bad computer PSU...

we've had a test about the reliability of PSUs in one of the German computer mags some time ago, with the focus on cheap big sellers.
It was frightening - but that article seemed to have at least some consequences, at least regarding safety

The 'mouse noise' is a thing I can reproduce immediately if I re-install the original 90 Watt PSU of my system. That thingy is really good (considering it's specs and how I've tortured it) but of course totally underpowered to drive 2 Pulsars and a CD Writer

With that PSU I had a -60 dB noisefloor on an empty analog in, now it's -86 dB.

I share your concerns about worn out caps.
My Casio midi sax had the usual broken cap killing the internal sound generation - very pleasant because it made the instrument cheap as hell, a mere 35 bucks

When preparing my K4 for sale I noticed the volume slider didn't work anymore - close to the slider there was a filtering cap, of course it was the culprit.
I just a aquired a 2nd hand A16. The one on eBay Wayne mentioned - 316 Euro were just to good to let it pass

2 channels had a worse noise floor than the rest - one already fixed by exchanging a cap...

cheers, Tom

[ This Message was edited by: astroman on 2004-07-10 19:45 ]

blazesboylan · Post by **blazesboylan** » Sat Jul 10, 2004 7:58 pm

Good to know, thanks Tom! That noisy mouse thing will be something to watch out for...

A word of warning though: do NOT replace the caps in your power supply unless you really know what you're doing. Those things can be lethal.

Cheers,

Johann

astroman · Post by **astroman** » Sat Jul 10, 2004 9:04 pm

yeah - that's agood advice !
while probaly everyone knows that tube amps are driven by high voltages, this even more applies to switching power supplies found in almost any kind of gear.
Several THOUSANDs Volt inside are not unusual.

And I definetely knows how it feels - the fork in the wall outlet is nothing compared to that

The caps can hold the power over hours, if not unloaded !
Since switching PSUs are really complicated beasts it's in fact best to properly get rid of them once they fail - the repair isn't worth the risk.

But while we're at it

the physical sensation can even be increased by the hit of a crt tube if one removes the 'big, dirty rubber' cable. The inside of the tube acts as a large scale capacitor keeping up to 25 KV for extremely long periods after switching it off.
We've had to deal with this frequently when Apple offered an upgrade to the original Macs and we had to exchange the tube connector. Once a collegue used his right hand as a discharging device - and though this guy wasn't the most shy dude on earth, his face truely reflected the meaning of 'a whiter shade of pale'

...but back to (useful) caps replacement, in case someone wonders:
of course I was talking about the low voltage electrolytic types used to buffer or filter circuit voltages.
Some of those get worn out over time due to chemical processes in the fluid contained in the caps.
HiFi experts usually exchange all those by high quality types in advance, if they handle vintage equipment.

cheers, Tom

Post by **garyb** » Sat Jul 10, 2004 11:22 pm

as to the modded plug, just cut it off and put a new one on(or replace the cable). i think that that outlet was stock...

Zeitlicht · Post by **Zeitlicht** » Sun Jul 11, 2004 11:19 am

Hi,

I had the same problem about two years ago.
I is the luna I/O. Not the powersuply or your gear.

I used 3 PC´s and several synths, fx, etc. and had horrible noise while moving mouse etc. I tryed some soldering and different cables and so on.

The solution is easy, but not realy cheap.

You need a line isolation box for every i/o you use.

I tryed the Palmer line isol. box and it is good. and I tryed a optical isolation thing
from http://www.elv.de electronic. It worked good too.
I tryed a cheap 8 DI box from MAM and it does
not solve the problem realy acceptable.

So my conclusion was to turn to ADAT because
there is no electrical transmission of the signals. If you count the palmer thing for 8 I/O´s you need about 300 €. With adat all the noise was gone in my case.

But i have to use the luna i/o in the future, because of 96khz/24 bit. And i will try now the behringer ultra di pro DI800. This is a 8 channel di box with ground lifting and line balancing. Just look on there page an download the manual ...

I hope this will help you if not turning to adat. Btw. I make pro.masterings an it is not true, that every gear from behringer is
bad. It depends on the productline.

You can find a good article on the noise problem on the http://www.swissonic.com page.

I hope you get calm signals and wish good luck.

Stefan

astroman · Post by **astroman** » Sun Jul 11, 2004 12:02 pm

On 2004-07-11 12:19, Zeitlicht wrote:
Hi,

I had the same problem about two years ago.
I is the luna I/O. Not the powersuply or your gear.

I used 3 PC´s and several synths, fx, etc. and had horrible noise while moving mouse etc...

there are 2 different situations regarding the infamous mouse move noise:
the video update of the mouse cursor puts a load on the video processor, which is quite some power sucker - they don't mount coolers for fun on them

In my case a definetely underpowered PSU couldn't catch up with the load demand - hence the sensible audio inputs reflected the load change.

In your case (I assume proper PSUs in your PCs) that part of the video signal probably emitted disturbance in the audio range of the frequency spectrum.

Since interconnection and cabling in studio PCs are complex by nature it may in fact be extremely difficult to get rid of this by cabling and shielding alone.
As your experience shows, one can work around this by optical insulation.

I focused mainly on the PSU culprit because it's frequently added as a cheap part - and it's very easy to outrule by just lending a bigger/better one.

cheers, Tom