Aeroic, Did You Wire Up The AxeFx/M4 yet?

[aeroic]

Well, I fired up the rig last night. With just the M4 going through the dry cab, I hear a good healthy ground loop. I had nothing coming out of the wet stereo cabs because currently, the Axe doesn't have any patches on it that have an FX Loop block in it so nothing was being fed to the outputs.

I've got work to do.

On another note, here's something that seems odd to me though. Even if you put washers between the rack unit and rails, isn't there a chance that the shaft of the screw that passes through the hole in the rack ear (calm down Eric! ), will touch the rack unit's face plate and still ground it to the rails? I mean with all the concern of rack units being space enough so that they don't touch and isolation and all this other stuff, how realistic is it to think that no rack unit will make any contact with the rails at all?

Dave

I would call VHT today and ask them where in the chassis you can lift the chassis ground (like the ground lift switch on the egnater). Dave Friedman says that you can do it, and just have VHT tell you where. That will get rid of one ground loop.

Eric

 

[dfrattaroli]

I would call VHT today and ask them where in the chassis you can lift the chassis ground (like the ground lift switch on the egnater). Dave Friedman says that you can do it, and just have VHT tell you where. That will get rid of one ground loop.

Eric

Eric, I'll do that. Now, I'm going to assume that's not the same as say, removing the grounding prong from the plug since, if it was, I'd also assume you'd have said, just cut the prong. Because, if it's the same thing as removing the prong, I don't think I'll do that for safety reasons. Can you shed some light on that? Or Dave?

Thanks.

Dave

 

[EWSEthan]

Well, I fired up the rig last night. With just the M4 going through the dry cab, I hear a good healthy ground loop. I had nothing coming out of the wet stereo cabs because currently, the Axe doesn't have any patches on it that have an FX Loop block in it so nothing was being fed to the outputs.

I've got work to do.

On another note, here's something that seems odd to me though. Even if you put washers between the rack unit and rails, isn't there a chance that the shaft of the screw that passes through the hole in the rack ear (calm down Eric! ), will touch the rack unit's face plate and still ground it to the rails? I mean with all the concern of rack units being space enough so that they don't touch and isolation and all this other stuff, how realistic is it to think that no rack unit will make any contact with the rails at all?

Dave

I would call VHT today and ask them where in the chassis you can lift the chassis ground (like the ground lift switch on the egnater). Dave Friedman says that you can do it, and just have VHT tell you where. That will get rid of one ground loop.

Eric

Dont you mean call Fryette? Isnt VHT a seperate company now that he has nothing to do with?

 

[jlbaxe]

Did I read somewhere that Axe Fx might make a unit that is only effects without amp sims? Id be into that. Maybe they will put a ground lift switch in it also.

 

[dfrattaroli]

Dont you mean call Fryette? Isnt VHT a seperate company now that he has nothing to do with?

That's correct. Gold star for you. I just posted at the web site as well. Should have an answer in a month or so.

 

[dfrattaroli]

Did I read somewhere that Axe Fx might make a unit that is only effects without amp sims? Id be into that. Maybe they will put a ground lift switch in it also.

It was requested but that's not going to happen.

 

[aeroic]

I would call VHT today and ask them where in the chassis you can lift the chassis ground (like the ground lift switch on the egnater). Dave Friedman says that you can do it, and just have VHT tell you where. That will get rid of one ground loop.

Eric

Eric, I'll do that. Now, I'm going to assume that's not the same as say, removing the grounding prong from the plug since, if it was, I'd also assume you'd have said, just cut the prong. Because, if it's the same thing as removing the prong, I don't think I'll do that for safety reasons. Can you shed some light on that? Or Dave?

Thanks.

Dave

Dave:

It's doing the same thing as what the ground lift function switch on your Egnater M4 does. Lifts chassis ground. No safety issues here.

And yes...Matt you are right...call Fryette. I always forget that they changed names!

Eric

 

[Suhr]

The only thing you might have to do is cut the shield on one side of your Y cable, and/or flip the ground lift switch on your M4. I'd try those two things before spending the money on the iso's.

cutting the shield on a cable is more band-aid than using iso transformers

Agreed
Cutting shields on audio cable is a bandaide.
A transformer or balanced outs would be the correct way or balanced outputs/inputs, also the studio standard. It is much cheaper to do balanced active outputs/inputs instead of transformers so this is the path usually taken. Transformers only change the frequency response and harmonic content when you use the wrong transformer for the job, IE: too great of a load for the size.
If all the makers could have a consistent internal grounding method we could come up with a standard to isolate the chassis from the circuit ground but that ship has sailed when it comes to consumer products.
Unfortunately when you deal with all these different makers they all have different spec's and dealing with ground loops in rigs turns into a job needing experience with individual units quirks.
Here is a great link if you want to spend your own time figuring it out.
http://www.rane.com/note110.html
http://www.jensen-transformers.com/an/an004.pdf

 

[dfrattaroli]

The only thing you might have to do is cut the shield on one side of your Y cable, and/or flip the ground lift switch on your M4. I'd try those two things before spending the money on the iso's.

cutting the shield on a cable is more band-aid than using iso transformers

Agreed
Cutting shields on audio cable is a bandaide.
A transformer or balanced outs would be the correct way or balanced outputs/inputs. Transformers only change the frequency response and harmonic content when you use the wrong transformer for the job.
If all the makers could have a consistent internal grounding method we could come up with a standard to isolate the chassis from the circuit ground but that ship has sailed.

Here is a great link if you want to spend your own time figuring it out.
http://www.rane.com/note110.html
http://www.jensen-transformers.com/an/an004.pdf

Thanks for the time, info and links John. Maybe using balanced cable where possible would be an option.

Dave

 

[Suhr]

Absolutely IF you have balanced outs and ins. That is a big if since most amps are not balanced. Our minimixII is balance send and return using transformers and it is very transparent.

And remember an "iso" is a transformer, nothing wrong with a good quality transformer but sometimes there are easier ways to deal with ground loops. Less is more, but we could take that all the way back to just using a cord, guitar and an amp. And again.... I DO NOT ADVISE lifting third pin ever, even though it can work to trouble shoot with no issues if you think carefully about what you are doing and how secure it is. Using a balanced differential ins and outs is really the right way to deal with it (but not common in our business), transformers can be used there with no problems if they are chosen for the job. Discussions like this should not turn into a pissing contest, lets help each other here Last I checked this was not Harmony Central

 

[dfrattaroli]

I just read the Rane document that John posted a link for. It basically defines what ground loops are and how they cause noise. It then describes 3 ways to combat them. The best way applies to balanced cables only. This method involved grounding the shield of the balance cable directly to the chassis. This doesn't apply to my rig as I don't have any balance lines in it. The 2nd best way is to use ISO transformers between balanced and unbalanced. Again, I don't think this applies to my rig. The 3rd best way is to remove the shield from the output side of the cable.

That said, if I wanted to try ISO boxes, which ones are in the $50-$80 range? I'm assuming that a DI box with a ground lift is not necessarily the same thing. Would a Radial Bigshot be an ISO box? They have a ground lift and ISO switch on Output B.

I'm going to read the Jensen doc now.

Thanks.

Dave

 

[aeroic]

I just read the Rane document that John posted a link for. It basically defines what ground loops are and how they cause noise. It then describes 3 ways to combat them. The best way applies to balanced cables only. This method involved grounding the shield of the balance cable directly to the chassis. This doesn't apply to my rig as I don't have any balance lines in it. The 2nd best way is to use ISO transformers between balanced and unbalanced. Again, I don't think this applies to my rig. The 3rd best way is to remove the shield from the output side of the cable.

That said, if I wanted to try ISO boxes, which ones are in the $50-$80 range? I'm assuming that a DI box with a ground lift is not necessarily the same thing. Would a Radial Bigshot be an ISO box? They have a ground lift and ISO switch on Output B.

I'm going to read the Jensen doc now.

Thanks.

Dave

Dave:

Dave F can make you some. Call him, he'll be able to help you.

Eric

 

[dfrattaroli]

I just read the Rane document that John posted a link for. It basically defines what ground loops are and how they cause noise. It then describes 3 ways to combat them. The best way applies to balanced cables only. This method involved grounding the shield of the balance cable directly to the chassis. This doesn't apply to my rig as I don't have any balance lines in it. The 2nd best way is to use ISO transformers between balanced and unbalanced. Again, I don't think this applies to my rig. The 3rd best way is to remove the shield from the output side of the cable.

That said, if I wanted to try ISO boxes, which ones are in the $50-$80 range? I'm assuming that a DI box with a ground lift is not necessarily the same thing. Would a Radial Bigshot be an ISO box? They have a ground lift and ISO switch on Output B.

I'm going to read the Jensen doc now.

Thanks.

Dave

Dave:

Dave F can make you some. Call him, he'll be able to help you.

Eric

Thanks Eric. I didn't know Dave built them. I guess I'd have to know how many I need. I suppose my needs would be similar to yours since we're using alot of the same gear.

Dave

 

[aeroic]

I just read the Rane document that John posted a link for. It basically defines what ground loops are and how they cause noise. It then describes 3 ways to combat them. The best way applies to balanced cables only. This method involved grounding the shield of the balance cable directly to the chassis. This doesn't apply to my rig as I don't have any balance lines in it. The 2nd best way is to use ISO transformers between balanced and unbalanced. Again, I don't think this applies to my rig. The 3rd best way is to remove the shield from the output side of the cable.

That said, if I wanted to try ISO boxes, which ones are in the $50-$80 range? I'm assuming that a DI box with a ground lift is not necessarily the same thing. Would a Radial Bigshot be an ISO box? They have a ground lift and ISO switch on Output B.

I'm going to read the Jensen doc now.

Thanks.

Dave

Dave:

Dave F can make you some. Call him, he'll be able to help you.

Eric

Thanks Eric. I didn't know Dave built them. I guess I'd have to know how many I need. I suppose my needs would be similar to yours since we're using alot of the same gear.

Dave

Yeah...I had considered to just build my own rig, but my time isn't what it used to be, and just decided to have Dave do it for me . Just email Dave and he'll hook you up for sure.

Eric

 

[dfrattaroli]

Yeah...I had considered to just build my own rig, but my time isn't what it used to be, and just decided to have Dave do it for me . Just email Dave and he'll hook you up for sure.

Eric

I'm going to continue to work at it first. I have NO time whatsoever but I can't just send all my gear to Dave either. It's been a learning experience to say the least. In the end, I may call Dave for some ISO action.

In my humble, inexperienced opinion: ALL things considered, it would appear to me that since ground loops are what they are, any SAFE solution is good solution. I don't think any one is more or less valid than another. I do prefer however, to understand each one and to know why one is better or worse for my application. Haha, it's all a band-aid when you get right down to it. I'm just really thankful that it's 2009 and not 1989 otherwise we wouldn't have resources like this at our finger tips. Oh, and I didn't have any money in 1989. But I did have great hair and 8-pack.

Rock on!

 

[bobw]

Wow! - where to start with this?!

Wow, I never thought in a million years that I would ever hear a well respected audio pro like yourself make the statement that iso's are the proper way to do things. To even think that a floating audio connection has anywhere near the same properties as a hard-wired audio connection is fucking comical at best. And to come out in public and state such bullshit is a fucking insult to true pros that understand.

For someone with a degree and a myriad of "certificates", you should know that a transformer is far better than "anywhere near" the properties of a hard-wired connection - to the point of not being able to discern the difference between the two. It really depends on the "properties" that are required for operation.

Another baffling statement is that lifting the shield never works in a guitar rig. Really? That's funny, the M4's ground lift does nothing more than lift the shield, and it works amazingly well. Same with a 3+'s ground lift jack. It's also worked amazingly well in the past on Triaxis, MP-1's, JMP's, and so many others I can't even remember.

The voltage imbalance alone will cause audio issues, let alone the capacitance & inductance issues. One club still uses there old hard-wired 1980's split snake because whenever a fancy tour rolls in with a transformer isolated snake, it makes everything worse. I don't care if your rig is built buy Dave, Bob, or Jesus himself, it's gonna be problematic. Even the mega expensive Furman AR-PRO's don't stand a chance, the buzz gets so bad with those you can practically see it!

Yes, lifting a ground return on an interconnecting cable will eliminate the ground loop. However, you are relying on the ground return being through the EARTH ground of your power cable. And all AC not being equal around the world, you run the risk of that ground becoming a garbage (RF) INJECTOR, not a garbage COLLECTOR as it was intended to be. The ISO transformer performs dual duty - it eliminates the ground loop and PROPERLY references the secondary ground to the LOAD CIRCUIT. Keep the earth ground out of the signal path!

One final note, if transformer isos are so great, and so inexpensive, then why doesn't Fractal, or any other company just put them in from the start? It doesn't take someone with a degree or even road experience to learn this stuff. All it takes is few minutes on the internet, or even a couple calls to Klark Teknik or BSS. Those two companies alone are well known for being about the best you can buy. Every piece of gear they sell does NOT come transformer isolated as standard, but rather as an option. Why? Because only in extreme cases do they ever want you to opt for the isos.

The answer to that question is simple - cost. They are NOT inexpensive as you believe. I suggest you do some costing. Transformerless, balanced, opamp drivers are far cheaper and do the job better - i.e., better frequency response, THD, and cable drive. Virtually all pro gear use this method. The basic circuit was conceived at MCI (I believe by Jeep Harned) many moons ago and gives Spice a convergence run for its money. It is the ideal replacement for a transformer.
This is the main reason transformers are utilized to a much less extent. They are relegated to ancilliary functions such as single-ended to balanced ISO interfaces.

Yes, some of your bandaid fixes may have served you well, but professional rig-builders whose clients have had to rely on their rigs working all over the world have long ago investigated these bandaids. Most are rejected, as they bring problems of their own. The fact that professional rig builders such as Dave Friedman are still in business proves that they know what works. And yes, you can take a short cut here or there, but will it be effective 100% of the time the world over?

What I find objectionable about your post is your personal attack. You should know better - it's okay to disagree, but to attack someone's reputation is intolerable. You diminish your stand by this sort of rhetoric. Lighten up - it would make for a far better discussion.

 

[RACKSYSTEMS]

Thanks Bob W.

 

[mentoneman]

i don't think anyone has suffered from substandard tonal performance under dave f.'s watch, so there is no reasons to suspect his methods. one indispensable piece of gear i have carried around with me in my gig bag from the day i took it from bob bradshaw's hand 15 years ago is a simple isolation transformer.

klark you have noteworthy things to share but dude --bull in the china shop!

ps i use soundcraft series 5 48 ch console, bss soundweb 9088ii for house dsp/matrix across 5 zones of coverage, klark teknik dn540 quad noise gate, , lexi pcm 91, tc 2000, yamaha spx2000, dbx 160xt/presonus acp88, EAW KF 850 EF/KF852 cluster w/ sb 850 and sb 1000 subs, every week

all wired up bysound image and tied to two independent hospital grade transformers providing squeaky clean power to our audio and video systems

and i have seen every option of grounding mentioned here used successfully

in the end when all is said and done, this next little tidbit will help diffuse the crux of the angst here, which should be safety, and not how many picofarads of tone i'm losing:

You can use an outlet tester first, to weed out obviously bad outlets. If it shows any fault, don't use it. If it shows good, you can use a digi volt meter to further inspect.

Meter testing of a 120v outlet should show:

From the ground, 120v to the hot (narrow) blade slot.

From the ground, 0v to the neutral (wide) blade slot.

Between hot and neutral, 120v.


Voltage can be 110-125v without much trouble.

Small leakage from neutral to ground, indicates problems with the service neutral.

Excessively high or low voltages, especially if they swing widely as various loads are introduced, indicates a completely missing ("floating") neutral connection at the service. If this is discovered, do not use any electrical service in the building! Floating-neutral problems will cause voltages to swing as high as 240v on a 120v circuit.

If you read 120v from neutral to ground, and 0v from hot to ground, the hot and neutral are reversed. This is most likely a simple matter of pulling the receptacle and switching the leads correctly, but in a commercial establishment, do not do this unless you're a qualified electrician. This problem would also be picked up by the outlet tester.

The meter can also be used to check for the presence of any leakage between service phases....this is the "I get zapped when my lips touch the mic while my hands are touching my guitar strings" problem. Before anyone gets zapped, if you've plugged into two different outlets at all, and don't know for certain that they are on the same branch circuit, put the meter between the mic barrel and the guitar strings. Any voltage at all is a problem, but a volt or two won't usually be felt by skin contact. I've however read voltages as high as 40v.

If the building is metal or there is considerable metal staging, you can meter between the ground and any metal components to be fairly certain they are close to ground potential. I've heard of people being seriously injured by touching their instrument and a metal building component, specifically a low roof truss or support column that was not bonded to the service ground and had been energized by faulty equipment.

Never 'lift' or otherwise disable the ground of any power circuit. "Adapter plugs" have no business in this business. If your gear is humming, use XLR ground lift adapters, lift the ground on your DI, but never leave out the supply ground.

On a side note, never trust anyone else's work. Test everything, even if it means insulting the house electrician's pride by metering something he just did. If he's a pro, he *expects* you to do this.

 

[mentoneman]

and here's the system i use weekly, in action:

Doyle Dykes

Sarah Macintosh


and if you liked what you heard and are in the southern california area near Redlands, these two artists will be our musical guests for our Easter church services on April 12, so you can hear them live, for free! consider this an official Rig Talk invitation! spammin' for the Lord!

sunrise service is 6:30 in the amphitheater

and our normal 8:00/9:30/11:00 am services will be in the main sanctuary
info


aloha

 

[suzuki211]

Takes me back to the 80/90's!!! Off to play!