Rack Development

[rabidgerry]

Ok guy's, changed my setup to what I had said I was going to.

UK/Ireland Rack Rig:
Power Conditioner
Power Amp              (Rocktron Velocity)
Noise Gate               (Boss NS-50)
Pre-amp                  (MP1 or Rockmaster)
FX Unit                    (Boss GX700)
Midi Control             (Behringer FCB1010)

Took me a very long time to program the FCB1010 the way I wanted to.  I go on tour next week and I was hoping to get it all sorted so I could take the new setup on the road with me.  Spent most of this week battling the FCB1010.  Had it pretty much programmed they I wanted but I had issues with the god dam expression pedals.  To summarize they were acting totally broken and as though they needed calibration.  They did not.  The way they were behaving also seemed as though they were suffering from a known issue where the optical sensor that operates the expression pedals was too sensitive and basically screwing up.  I spent a long time trying the few fixes that are out there but to no avail.

It turned out I had programmed a little bit of conflicting instructions into the 1010 that was causing haywire behaviour but I had a eureka moment last night and got it sorted!

Tomorrow I test it all out in the live / rehearsal situation.

Few question for you all and any help is appreciated.

Should I try my best to isolate my gear to prevent ground loops?  The reason I ask, is because now I've added another piece of rack gear to my rig and another power supply I am getting a hum.  It can barely be detected with noise gates etc working, but I'd like to try resolve it or reduce it as best I can.

Should I use my ground isolator (ART Clean box II) which has sorted the issue in the past by having my send from FX unit run through it first before going into my pre amp?

also should I do any of what this guy is doing on this website?

https://aperioguitar.com/2012/02/23/grounding-fizz-and-cable/



Any advice is appreciated.

[rabidgerry]

No one got nothing to add on isolating units within racks to eliminate hum then?

[MarshallJMP]

It sometimes helps and sometimes makes it worse. Some of my rack units are isolated, some are not.

[Kim]

I just screw everything in without isolators initially.  If there's a problem after that, then I determine which unit or units need to be isolated.

[rnolan]

Hey RG, it also depends on what's causing the hum, isolating works (I suspect) with ground loops which can be very tricky to pin point.  But it can also be caused by gain structure issues, and as is the case with my IPS33, mechanical vibration from the transformer into the case/lid.
The link you posted is a good one, he makes lots of sense and provides good advice.  Seems I'm lucky with my rack, I haven't done anything special, some of my cables are good quality, some are just the multi colour ones you buy in packs of 8 (or whatever), these are ok in the rack coz they don't get connected/disconnected, with these cheap cables, the plugs aren't soldered, the cables attachment is held in place by the plastic molding.  I do my best to keep power leads away from signal leads.  Once I have everything plugged in, I tidy the leads with cable ties.
Maybe to track this hum down you should turn the noise gates off ?

[rabidgerry]

I'm pretty sure my hum is coming from the fact that two units are powered by a wallwart/power pack.

I'll give you an example, before I dropped the floor unit for FX I got hum going into the rockmaster.  I was able to determine that this was because I had a ground loop being cause from running a pre in fx unit loop.  I did this by detaching the earth in the rockmaster plug.  Hey presto no hum.  So the solution to this was use the Art Clean box II.  Yes worked a treat.

Toward the end of the floor unit use I started running a different way,  I was going direct into the pre and then having the pre out go into the return of the fx unit.  This sacrificed the use of front end effect from the fx unit but also eliminated the need for clean box II which is a ground loop isolation box.

So moving onto where I am now.  I use two unit loops, one for noise gate and one for FX.  Using the clean box gets rid of the hum and basically the noise gate keeps it 95% unnoticeable.  However there is still a bit of hum.  And it's because there are two loops being used.  The noise gates loop and the fx units loop.  I could run the clean box in both loops I guess since it has two separate transformers for decoupling earth loops but I was just wondering if there are any other things I could try instead hence the question about isolating on the rack itself.

[MarshallJMP]

Can you give a bit more info about those 2 loops you are using, maybe a schematic of the routing?

[vansinn]

Some devices have everything internal fully insulated from ground, with only the earth pin in the power cable acting as ground.
This is the preferred way of ensuring single-point grounding, in order to avoid ground-loop [hum], because the builder can now use ordinary jack cables, and arrange single-point grounding for each device at the common mains summing point.

Other devices have their in/out jacks grounded to chassis.
This not preferable, as there's the possibility of ending up with grounding through both the mains prong and simultaneously through the signal cables - because of the chassis-grounded in/out jacks.

As Kim said, the builder can start with simply mounting and connecting the whole shebang, and see if all is ok.
If hum is present:
* either disconnect everything, and then reconnect one device at a time, until hum appears.
* or, disconnect devices one by one until the disappears.

Hum most often develops when using, say, external processors in send/return loops, simply due too signal cables carrying ground in a loop-structure, while this external device is also being grounded through the mains prong.

When the hum-hum device has been found, a usual remedy is to isolate it from the rack rails using insulated bolts and washers and maybe a strip of gaffer on the rails to avoid chassis contact.
Sometime it's possible to use custom signal cables having the ground flex connected at only one end - best option is to leave the open-ground end of the cable connected at the Send jack.

[rnolan]

Hey RG, a thought, it may be a dud wall wart ?  There were posts previously about the wall warts to phantom power the ADA midi pedals causing noise.  Worth a try  :dunno: .BTW, most of the ADA jacks don't earth to the case, eg Mike had really bad hum on his B200s when he changed the output jacks to standard, to fix he changed them to the plastic collard jacks that don't contact the case (as they came with).
At the end of the day, isolating each unit from the rack rails etc seems a good idea (though good quality units "shouldn't" need it).

[Soloist]

Hey RG, you might want to isolate the velocity. In my experience the Rocktron equiptment is usually the culprit. Great gear, shitty ground loop hum. My old Pirhana pre amp was the same way.  :headbanger:

[MarshallJMP]

Also use different wall warts for different fx stuff, don't use one and split it up.

[rabidgerry]

I shall post a diagram later of how I have everything hooked up.

Ok so most of my power is coming from the Furman, I have one walwart for the NS-50 plugged into it.  I noticed this power supply has a plastic ground pin, not sure if that's relevant.

Then the power supply for the GX700 has a separate power supply.  I have no more adapters to plug this into the furman so I just have to connect it to the mains.  The plug on this also has a plastic earth pin.

Richard, no dud walwarts mate, just think it's to do with my setup.

[rnolan]

Hey RG (Richard, no dud walwarts mate, just think it's to do with my setup), good to hear, can you split the Furman feed (output) so it does both wallwarts off the same Furman outlet ? use a double adapter or small powerboard ? Then all the earths are off the Furman.  Obviously the plastic pins mean the wallwarts don't earth that way (as most wallwarts don't (haven't come across the plastic pins before, here they just have 2 (active/neutral), however, the units will join the ground via their jacks and/or through the rack rails (which I hadn't considered until the article/blog you posted the link to).  Having one WW outside the Furman earth chain "may  :dunno: " be causing the hum ??

[rabidgerry]

Hi all,

just back from a week long tour of England.  Dam tired!

Anyways before I went I randomly isolated the GX700 using tape on the rack ears and also the same with NS-50.  Then used washers with the rack screws and one little rubber tab on top of the ns-50 to separate it from the gx700 above it in the rack.

The outcome, well the whole tour I heard no hum.  One place had terrible noise, but that must have been down to either the lights or the wiring as it was that horrible buzzey noise you get.  It musta have been bad because I have a shielded guitar and also a noise gate which did silence it, but you could hear it if I didn't have hand on strings.

Anyways the earth hum seems to have gone.  And I only isolated the two units using walwarts.  I will be able to tell properly if there is hum once I am back in the rehearsal room.  I didn't use the Art Clean box once the whole tour to safely remove an earth.

[Dante]

What a GREAT tip  :thumb-up:

Thanks Gerry, now I'm going to take all my racks apart and put a thin piece of rubber behind all the ears. Wait, better yet, I can just plastic-dip the rack rails and then reinstall.