Patch bay for idiots help needed

[witzendoz]

The main concern there will be the potential to create ground loop buzz.

Make sure there is no common earth across the different channels on the patch bay and that the non common jack plugs are isolated from each other, this reduces the chance of an earth loop. Most are nowadays but some of the old ones around had a common earth across all jacks.

Alan.

 

[ecc83]

Make sure there is no common earth across the different channels on the patch bay and that the non common jack plugs are isolated from each other, this reduces the chance of an earth loop. Most are nowadays but some of the old ones around had a common earth across all jacks.

Alan.

+1 And, good idea to electrically isolate rack unit metalwork from the rack casing. This is a general rule for rack systems, you do not want ad hoc earth paths between chassis (which can be intermittent and drive you nuts!).

There are two products on the market AFAIK. 'RackSnaps' and 'Humfrees'. Of course, anything in a rack that is mains powered and needs an earth must be grounded back at the supply. The rack case itself should be bonded to a good earth via a separate, stout cable.

If this all leaves some of you boggled I can do a scribble.

Dave.

 

[ashcat_lt]

I was talking about using a half-normalled patchbay to multi a signal, and more generally just about splitting signals via straight wire. Yes, there are ways to get around a ground loop, and simple things you can do to minimize the likelyhood that a bad one will cause you problems, but when you start splitting signals, you always increase your chances of having those kinds of problems.

 

[miroslav]

Or you can also use a balanced power distribution system, plug all your stuff into that...and really reduce the potential for AC/ground loop issues.

 

[ecc83]

Or you can also use a balanced power distribution system, plug all your stuff into that...and really reduce the potential for AC/ground loop issues.

I would REALLY like to see some technical support for that assertion friend M! I can see how hum INDUCTION is reduced but ground loops are caused by a different mechanism and 'earths' stay the same.

And I must repeat a warning I gave a while ago that balanced mains power CAN put service people in danger, especially where you have 240volts.

Dave.

 

[miroslav]

I don't know what technical info is sufficient for you to not be skeptical....or that's it's even important that you're not.
Balanced power is used in many studio facilities among other environments where its benefits are of value.

Here's some basic info from Equi-Tech, though in my case, I'm using the Furman product.
Balanced Power from Equi=Tech

AFA what works in the 240 world...it may require more of a "ground up" build to properly implement balanced power rather than using more simpler, plug-n-play devices like we can with 120.

I think the biggest drawback...for even the plug-n-play devices, is that BP is not cheap, never mind when you get into the bigger facilities that require much bigger solutions and/or need to have it built in from the ground up.

I can tell you this...my studio equipment hasn't heard any hum or seen a ground loop....dead quiet.

 

[ecc83]

Crosstalk: Readers' Writes |

The above covers the safety aspect of balanced power. The article does state that BP is more common in the US than here where there is only the potential to have an 'unexpected' 60volts or so ref ground in the event of an equipment fuse failure. Even so it states that US Code requires "Only qualified service staff" to be allowed access to equipment when BP is installed.

The attached Jensen document states that the claims of the 'BP Industry' are often very inflated and unrealistic. For my money I can see some benefits (as indeed ARE mentioned) but since the attached, ad hoc equipment still has unsymmetrical, i.e. one single winding mains transformers and the earth leakage currents can still be present, the potential (boom! Boom!) for ground loops must exist. Bill W goes on to say, (as does the SoS note) that much of the perceived improvement in noise in a BP fed system comes from the rationalisation of the mains connection and their 'one source' property.

I have read the .pdf in the link and, "well they WOULD say that wouldn't they?"

I have no doubt Miroslav that your studio has benefited from symmetrical power but as you say, not cheap and before anyone embarks on such a venture they should ensure that their studio equipment is ALL balanced properly to begin with, following best practice. In UK and other 240volt parts of the world, the safety aspect needs very careful consideration.

Dave.

 

[witzendoz]

Apologies to the OP, who asked a simple question about a patch bay and has now go so many suggestions and theories that he has run a mile.

The only reason I originally mentioned earthing was that a common earthed patch bay can cause an audio ground loop so try to get one that does not have this. How did we get onto mains earthing systems? There is another thread here that went on for weeks about it LOL.

Alan.

 

[ecc83]

Apologies to the OP, who asked a simple question about a patch bay and has now go so many suggestions and theories that he has run a mile.

The only reason I originally mentioned earthing was that a common earthed patch bay can cause an audio ground loop so try to get one that does not have this. How did we get onto mains earthing systems? There is another thread here that went on for weeks about it LOL.

Alan.

Agreed Alan, an unfortunate diversion. However, once BP was mentioned I could not fail to mention the safety issues which are much more serious here with our higher supply voltage.
A thought occurs. There is a tendency for very expensive 'studio' equipment to be produced in a simpler, cheaper form for the HR market. This is to be welcomed as a rule although sometimes 'cheap' goes too far and people buy things THINKING they are 'pro' when they are far from it. All this is cool so long as the factories are just turning out cheap mixers and mic pres but my fear is that someone will latch onto BP and produce a 'Magic Box' that claims to rid the nooob of his/her hums. It might but will render the system potentially lethal.

Sorry OP!

Dave.

 

[bouldersoundguy]

Yeah, I wouldn't trust BP. That thing with the drill rig in the Gulf of Mexico was pretty bad.

 

[miroslav]

It might but will render the system potentially lethal.

You keep going on about it being potentially lethal, as though utilizing a balanced power scenario is something that is going to be jury rigged without any oversight.

The BP boxes we have available for the 120V market are all design tested and approved for audio equipment use, and of the 2-3 main brands out there, most have already seen a lot of studio use. I've not heard of anyone dying from using them.

I mean...seriously...there is nothing "lethal" about using them, not any more than any other electric device.
AFA the 240v usage...again, if there are design tested and approved BP boxes out there for 240v use, I wouldn't concern myself about using them. If there are not...then it's a moot point talking about it being "potentially lethal".

TBH...I would trust a designed/approved purpose built device more than jury rigging common ground lines and/or augmenting your power supply in some non-typical way in an effort to minimize hum and noise.

AFA the cost...well...it's kinda relative to how bad someone needs a solution. You know...we work hard just to see a 10-15% improvement.

AFA the OP's patchbay questions...the only reason we segued into the power discussion was because of the whole grounding/ground loop stuff that was brought up. I don't think most home rec folks need to employ a balanced power system for a handful of outboard gear and where they mostly work ITB. I was just saying that a balanced power system *can* help with those issues, as another alternative.

 

[miroslav]

I have an 8 input recording console as well as a P.A.. I would like to have one input split to two outs on the patch bay so that I can either record, practice (through my rack system) or even both.

I'm just curious what you mean by "so that I can either record, practice or both"...and what's the actual gear and I/Os that would come into play.
IOW...your consoles is already somewhat of a "patch bay" in itself, especially if it's a decent recording console. I mean, most have multiple routing options that allow you to split signals and route to multiple outputs.

I think if it was clearer what/how your doing and the gear being used...then the best-case scenarios for employing patch bays would be more obvious.

 

[ecc83]

You keep going on about it being potentially lethal, as though utilizing a balanced power scenario is something that is going to be jury rigged without any oversight.

The BP boxes we have available for the 120V market are all design tested and approved for audio equipment use, and of the 2-3 main brands out there, most have already seen a lot of studio use. I've not heard of anyone dying from using them.

I mean...seriously...there is nothing "lethal" about using them, not any more than any other electric device.
AFA the 240v usage...again, if there are design tested and approved BP boxes out there for 240v use, I wouldn't concern myself about using them. If there are not...then it's a moot point talking about it being "potentially lethal".

TBH...I would trust a designed/approved purpose built device more than jury rigging common ground lines and/or augmenting your power supply in some non-typical way in an effort to minimize hum and noise.

AFA the cost...well...it's kinda relative to how bad someone needs a solution. You know...we work hard just to see a 10-15% improvement.

AFA the OP's patchbay questions...the only reason we segued into the power discussion was because of the whole grounding/ground loop stuff that was brought up. I don't think most home rec folks need to employ a balanced power system for a handful of outboard gear and where they mostly work ITB. I was just saying that a balanced power system *can* help with those issues, as another alternative.

The lethality Miroslav is not with the mains transformers. I am sure they are built to the very best specifications. The problem arises if a person opens up a piece of gear for servicing after a fuse has blown. Said fuse is of course in the LIVE line (it is illegal here to have two) but of course the neutral side of the supply is still present at 60volts ref ground. A 60V shock is probably survivable by 95% of the population but 120V rather less so.

We do have balanced supplies where the greatest possibly noise suppression is required. Hospitals and labs but of course such place do not allow UTC et al to poke about in the kit!

I agree that the above shock scenario is of very low probability but the history of electrical safety has always been one of reducing danger, however unlikely, to the minimum.

The SoS letter makes this clear as well. If you wish to pop 'electronically' over to Blighty you can read the discussion on Sound On Sound | The World's Premier Music Recording Technology Magazine

Dave.

 

[miroslav]

The problem arises if a person opens up a piece of gear for servicing after a fuse has blown. Said fuse is of course in the LIVE line (it is illegal here to have two) but of course the neutral side of the supply is still present at 60volts ref ground. A 60V shock is probably survivable by 95% of the population but 120V rather less so.

Well, I think that applies to most electronics....so there is no reason to specifically stress the point just because it's a balanced power device.

Poking around most any tube amp without understanding can kill you just as easily...even after you unplug it.

 

[ecc83]

Well, I think that applies to most electronics....so there is no reason to specifically stress the point just because it's a balanced power device.

Poking around most any tube amp without understanding can kill you just as easily...even after you unplug it.

No, with the greatest respect you miss the point. A piece of kit can be opened by a TOTALLY EXPERIENCED TECH but if he is unaware that there is live mains present when there should not be he is at risk. This is why US Code warns that only specified staff should work on the equipment, they need to know about the unusual mains wiring.

I also do not agree that a valve power amp capacitor dump can "kill you just as easily" The shock is usually short lived as the caps discharge and current limited. The current from 120V (our case) will be sustained and deliver 100s of times the lethal dose. (, I have had a few amp shocks in my time, never REALLY got across the mains, maybe not COMPLETELY daft?)

I really don't want to 'fall out' over this Mir'! US mains supplies seem noisier than ours? (a point touched on in the link) and so BP is likely to show very big improvements. The general opinion here and shared with Bill Whitlock, is that it is better to has a properly installed BALANCED audio system and sort out grounding by the now well known best practices.

Dave.

 

[miroslav]

If anyone is "experienced" with electronic gear...I'm not sure how they can be unaware that the gear they are working on is powered and live....?

The "potentially lethal" perspective is blown out of proportion here.
You can contrive all kinds of scenarios where even the more benign situations can become "potentially lethal".
Your bathroom hair drier can be "potentially lethal"...or your electric stove...etc...etc....but generally speaking, when used properly and provided cautions are observed, we live with many "potentially lethal" devices every day, and it's not a problem.

Same thing with balanced power devices for audio that are commercially available.
I just don't get why you need to put some unnecessary fear into their normal use....it's really pointless.

Oh...and if you've been zapped by 450V amp capacitors, and lived...you're lucky.
I've had my share of electrical encounters, but it only takes one bad one.

 

[ecc83]

If anyone is "experienced" with electronic gear...I'm not sure how they can be unaware that the gear they are working on is powered and live....?

The "potentially lethal" perspective is blown out of proportion here.
You can contrive all kinds of scenarios where even the more benign situations can become "potentially lethal".
Your bathroom hair drier can be "potentially lethal"...or your electric stove...etc...etc....but generally speaking, when used properly and provided cautions are observed, we live with many "potentially lethal" devices every day, and it's not a problem.

Same thing with balanced power devices for audio that are commercially available.
I just don't get why you need to put some unnecessary fear into their normal use....it's really pointless.

Oh...and if you've been zapped by 450V amp capacitors, and lived...you're lucky.
I've had my share of electrical encounters, but it only takes one bad one.

Technicians work on 'live' gear. I have done so for over 50 years. A good proportion of kit has only a single pole mains switch (and fuse) in the live line. If a tech does not know that EVEN WHEN the live side is switched off there is a serious voltage on the (normally grounded) neutral line he is at risk.

Read the link etc. People vastly more electrically qualified than you or I have reservations about the ad hoc use of balanced power, especially here. Your own Code includes the warning I mentioned.

I say again. It is NOT the balanced power device that is potentially unsafe, it is the condition it can put equipment in unbeknown to even an experienced technician.

Dave.

 

[miroslav]

*sigh*.....

I'll let you know if I ever hear of anyone dying from properly using a balance power unit in a studio environment.

Careful with that hair dryer...

 

[ecc83]

*sigh*.....

I'll let you know if I ever hear of anyone dying from properly using a balance power unit in a studio environment.

Careful with that hair dryer...

You are constantly misconstruing my words. No one is going to die from a balanced power UNIT! They MIGHT however catch a packet off a 'neutral' they fully expected to be at earth potential.

And yes, I was a bit alarmed at the suggestion of a hair dryer in a bathroom!

Dave.

 

[ashcat_lt]

K. But in the real world, we create redundant connections between the chassis grounds of our devices all the time, and there are a number of reasons that this might cause noise - at least some of which don't really have anything to do with how "clean" your power is. "Best practices" will help in most cases, but there is always potential for ground loop hum when connecting two active devices, and adding a third increase that risk.

My real point was that splitting an active source via the half-normalled patchbay module using normal TRS cables shouldn't have much effect on either volume or tone. It might be noisier, but you can't really know until you try it, and then you decide if it's enough noisier to warrant trying to lift a shield or introduce a transformer or whatever.