6048e

[madmuso]

Tie lines almost done! One more box to do.

I was soldering today and because I was making balanced and unbalanced cables it occurred to me that all this time I have just assumed that all the inputs and outputs on the 6000e patchbay are balanced. I went through the patchbay section of the manual today but it doesnt say. Does anyone know? Is the entire I/O (every patch row) of the console balanced?

thanks,

[brewery]

quasi balanced for the most part, but yes, hot/cold/shield on all connections.
i would recommend lifting the shields on the non-patchbay side xlrs to avoid ground loops.
(this doesn't work for mic lines and mic pre inputs though, and i would keep the monitor feeds shielded too). just bend them over , so you can always connect them again later.

gets rid of a lot of hum issues.

[marcmozart]

Hi Brewery,
Grüsse aus Gießen nach Köln!!

What does "lifting the shields" mean? And "non patch bay XLRs" meaning the DLs from the patchbay that lead to my outboard rack, right?

Cheers,
Marc

[sintech]

Hi, Jim would be the best person to advise, but.. as I'm installing mine right now.

As standard: The Insert send and return's on Row E and F, only connect hot and cold to the outboard gear, the screen is disconnected at the patch point. From the bus card to the patch point, the screen is present.

The outboard should be screened to the patch point as standard.

General idea i guess, you play with the screens if you have any earth issues.

So far, I've only had to cut the XLR screen on my Neve 33609 inputs.

I've made a pair of small XLR mic leads, with the screen disconnected, patching them inline to see if it helps or not.. this saves a lot of cutting and re-soldering.

[jimlfixit]

Hi People.

First of all, could I suggest writing a new subject header into posts sometimes as I'm a bit bored by seeing the same old 6048e title (in this case for example)? In nearly every post I do, I change the subject title to match the change of thread. Sorry if I seem out of line here but it is 7:30 am, I'm very tired and last nights dinner is stone cold (plus I'm a grumpy git sometimes!).

Moving swiftly on:

The subject of studio signal grounds could create a whole new menu possibly involving up to 6,439 posts as this subject involves many vastly different views and I believe there is still no known proper answer as the overall studio grounding scheme (if any!) plus the individual equipment AC and signal ground layout wiring has an affect (technical, domestic earthing and equipment circuits, pin 2 or 3 hot balanced gear, unbalanced gear, position in racks, distance apart etc).

As a result, I won't attempt to deal with this now as it is too complicated.

I'll address a few points here based on my memories of SSL wiring plus other issues but intend to start a new post on SSL grounding when I have time.

1   All older (4 and 6K at least) SSL console connections to the studio (at least via DL's) were wired balanced. I have no knowledge of any being unbalanced unlike some cheaper consoles!

2   I am quite sure that all the internal wiring from the patch to any part of the console (channel 6 way Biccs, 651 centre section MRAC's, PCB's and other functions) were wired with the screen NOT connected at the patchbay but all the channel Biccs had their screens connected which were then connected to one of the copper bars running through to the connector panel end OBA (M6) grounding stud.

Only the 96 way DL connectors (which were always wired as balanced circuits) were wired to the patchbay with the hot, cold and screen wires connected at both the DL and patchbay ends whether they were mic's, multi send/returns, centre section echo, cues, monitors, stereo etc or outboard ('user option' in SSL terminology).

3   As the last few posts show, some experimentation is advisable. Use phase reversals on your patchbay (to experiment between 2 or 3 hot balanced XLR connections) plus a made up lead with the screen 'lifted' (not connected) to address any signal grounding issues.

4   This is a complicated issue and the whole studio and building earthing needs to be known before a proper answer can be given. As Sintech states, 'play with the screens if you have any issues' Brewery states 'lifting the shields on non patchbay side XLR's'. This is probably okay as XLR's are balanced connections but, if that piece of balanced gear is pin 3 or 2 hot and is then plugged into a device which is unbalanced, you may have lost your signal ground (big possible future topic).

5   As a general rule for now, I would say, keep all the patchbay, panels and other connections in a studio fully wired and only disconnect screens (shields or drain wires) at the studio equipment ends (outboard, ProTools etc) if really required if you have any problems. Don't cut them off as you may need them if or when you change your equipment in future. I will post some more findings on this in due course as I am about to complete a studio install shortly and will investigate the whole grounding issue in more detail. I intend to look at an SSL console, document the signal grounds and AC earthing, measure impedance differences within various equipment (signal screen verses metal case and AC earth) and come up with some sort of cunning plan!

Decades ago, I remember that there were two rules here in the UK. Either ground the signal at the source and lift at the destination or the other way round. I don't think that either of these applies especially now when everything has got much more complicated and involves far more signal formats than way back then when it was all analog.

6   Never lift a signal screen on a mic feed throughout the circuit otherwise the vocalist may die and you may be in court.

7   Never lift an AC earth on a piece of equipment as it could also result in death. I've seen this done in some big studios in the past and it is crazy. The earth wire was sometimes folded back and sticking out of the AC plug so someone else (probably the Insurance investigator or the Police at that point) could tell that the gear wasn't earthed …!

I reckon that some of the signal noise problems could result from balanced gear (either 2 or 3 hot) connected to unbalanced gear in the signal chain at the same time. I guess, in theory, if everything was routed through the SSL patchbay, one could disconnect the signal grounds at the other ends (except for the mics) for balanced gear if there were any grounding (not earthing) issues assuming everything was on the same electrical circuit and not shared with items such as fridges for instance.

Also, especially with more digital stuff being used within a studio setup, keep the analog cables away from all the others within the trunking areas if it is not too late already. I remember a Sony DAT machine frequency affecting audio cables back in 1987 at Steve Winwood's studio in Oxon, UK so, hum and noise problems may not just be due to lifting screens.

I am not a tech person and have only expressed my views after wiring numerous different studio types plus dealing with and observing these issues over some 30 years. I have constantly researched this subject on the internet and still don't have a definitive answer (there is also a lot of bullsxxt out there) even now especially as more digital, optical and Cat type gear is involved in studios which adds to the confusion as some of these at least, could affect the audio signal.

I hope this helps but this a huge and somewhat unknown subject even now as you can probably tell from what I have written unless, I am talking rubbish (trash) as well?

Regards for now from Jim Lassen (www.profcon.co.uk). Also on FACEBOOK

[brewery]

all of what jim said is correct, and there are lots of different approaches when it comes to grounding.
i came to find it easiest and most effective (i do around 3 major installs a year) to star ground everything from the patchbay.

you need all your mic lines and mic pre inputs shielded. both to ensure phantom power is working properly, and (like jim said) not to accidentally kill people.

i do however lift the shields on all other outboard and tape send/returns. the benefit is that it safes time (only 16 wires per d-sub, and no shrink tubing on the shields!) and, while it in most cases doesn't make a difference, it avoids ground loops. it can really only make the whole system quieter.

the only times i had to reconnect the shield is with a few really old american pieces (UA175b for example). if there is a hum, it will not at all be subtle, so you know instantly what to reconnect. the other good reason to only bent the shield back, and not snip it off, is that you might want to use some of them for mic pre ins in the future.

on converter d-subs, i snip the shield off right away. never had any issues there, and it makes everything easier.

like i said, there are different approaches to this, but i'm very happy with the noise floor this one achieves.

[brewery]

oh, one more thing - on unbalanced connections you can lift the shield too, but make sure cold is connected to ground. (which you should do either way, to not lose 6 dB from losing a leg :-)

[jimlfixit]

Thanks for backing me up Brewery (I am relieved that I wasn't talking rubbish!). A star system is my preferred choice as well really as it simplifies the wiring as you mentioned and references all the signal grounds back to the central patchbay on an SSL rather than some unknown grounding wiring route at the other ends. Also, some equipment may have a separate power supply which could mean it has no direct relation to a proper earth as it may be a low voltage feed on 2 wires (+ and 0V).

By using a proper console like an SSL and all analog signals going through the patch, the star grounding method is a sound choice (excuse the pun) assuming outboard and multitrack racks (everything really that goes back and forth to and from the SSL patch) are referenced back to the central star point perhaps even with the same length of cable meaning that, if the shortest length is 2m and the longest is 10m, make them all 10m. Then you know that they are all the same going back to the central grounding point. Also, use big wire, if you can afford it, as there is less resistance.

If you are not using a proper console, which is becoming more common these days, you may just have a powered 8 or 16 channel bucket, some convertors, a computer and no patchbay. That's when it gets a bit more difficult to work out as there may not be a central ground reference point and various items of equipment are interconnected between themselves.

Brewery's point about lifting the screen and connecting the cold to the ground contact on an unbalanced jack reminded me of an installation I was involved with over 20 years ago. By the way, don't do this as you will find out later. The tech at the time said he was going to wire all jack unbalanced connections to equipment with 'stereo jacks', which is the wrong expression in Pro-Audio installation terms as they are really balanced single circuit jacks even though they are sometimes used for stereo, unbalanced, circuits on a connector or even mono insert send and returns on smaller desks (notice I didn't say consoles!). I think headphones are the only professional use of balanced jacks being used for stereo purposes but may be wrong!

Anyway, back to the story. All unbalanced outboard with 1/4" type A jacks got wired with balanced jacks and plugged in (I did have my doubts at the time). By the way, don't get confused with the GPO type B jacks which do not make a proper contact ... SSL bought these once by mistake for the 621 Producers Panel and found out the hard way during testing but that's another story.

Again, back to the plot and finally the punchline. When it came to testing, some of the unbalanced outboard didn't work properly. The reason was that the units were fitted with unbalanced jacks so, with a fully wired balanced jack plugged in, the ring (cold) had nowhere to go (or be referenced to) as there was no ring cold contact wired within the unit so it floated until the problem was discovered and fixed, in this case by moving the cold ring wire to the screen connection by the embarrassed tech.

People, perhaps research your equipment a bit before wiring. Open the top, see the service manual and understand the wiring arrangement especially the relationship between the audio ground and AC earth. In 1999, at a Mutt Lange studio in Switzerland, we took apart about 100 pieces of outboard to fit new transformers or change the links as the stuff had to be converted to European AC voltages. At the same time, all the signal to AC grounding/earthing was looked at and documented. There were quite a few differences between the units and it was an eye opener for me.

Hope this proves useful and I have got my facts right ... gulp. Regards from Jim Lassen (www.profcon.co.uk).

[marcmozart]

Quick question as I'm just about to start the DLs for my converters. I have already done the D-Subs for the converters and they're fully connected +, - and Ground at the D-Subs.

Can I just connected the + and - at the DLs (and not the - I guess it's called - "audio ground").

FYI, we're also just figuring out the electric installation in my room and we will do a star grounding system.

[radardoug]

oh, one more thing - on unbalanced connections you can lift the shield too, but make sure cold is connected to ground. (which you should do either way, to not lose 6 dB from losing a leg :-)

Are you talking ins or outs? The subject of connecting unbalanced signals to balanced is huge.
Short answer, if in doubt, use a transformer!
Long answer, definitely new topic!

[jimlfixit]

Edited quote from Marc. "As I'm just about to start the DLs for my converters, I have already done the D-Subs and they're fully connected +, - and Ground at the D-Subs. Can I just connect the + and - at the DLs and not the audio ground? We're also just figuring out the electric installation in my room and we will do a star grounding system".

Marc (and others). You studio chaps need to address your technical ground ideas first of all before thinking about lifting individual grounds at various ends later on. Your D subs are already wired with ground wires but you are just figuring out the electrical installation, and will do a star grounding system. Surely, this is the wrong way round. Sorry Marc (I love your SSL refurb but call me or Eric ... Brewery ... on this so one of us can help).

Some SSL's (or other consoles) in professional studios may have a proper plan for technical grounding worked out beforehand but, these days, more smaller SSL studios may be located within a house. Therefore, you have to deal with the normal house electrics as well.

Balancing transformers is an expensive option and not necessarily required (although I have just posted an advert in the buy/sell menu for Sowter 5069 1:1 transformers). The whole technical grounding issue is indeed a complex subject but, to answer part of your question in a sentence, wire the DL as a balanced circuit including the screen (audio ground) drain wire.

The passive wiring in a studio (patchbays and panels as an example) should always be fully wired. Only the other ends (inputs and/or outputs) may need to be addressed in terms of lifting audio grounds but, as Brewery stated, a star earth system is preferable.

Perhaps some of us can swop ideas regarding grounding and present some proposals on this site. Eric (Brewery) plus Andy (Sintech), Mata and others could help. I haven't got time to draw some diagrams on this for now but it should be fairly simple.

More details from me (and hopefully others) later. One of the reasons I haven't posted something on this subject yet is that, when I draw something on paper (not computer) and try to scan it via my IMac, the pdf comes out as 12mb or something like that rather than 70kb or so. If I can master that problem, I will post many more topics on the forum (please advise and contact me directly if possible to save cluttering up the site).

Regards from Jim Lassen (www.profcon.co.uk). Also on Facebook FACEBOOK

[kilmister]

Offtopic.

Jim, check what dpi resolution your scanning software is using. 300dpi and text/line art (black and white) settings is  good enough for diagram pdf's. Hope this helps.

-Paavo

[michaeldtech]

I agree with Jim.  I did not look at this thread for a while because 6K's were always yawnsville for me.  Nuff respect because they are quite relevant today.
I am not familiar with the electrical codes in the UK or Europe.  In the US I have not needed a "star ground" system since the early 90's.  All that baloney with a third wiring infrastructure terminating at a bus bar under the console and alligator clip-leads going to floater outboard or synths in the CR became irrelevant when I started to specify "hospital grounding" for the electrical.  That has a separate third wire to every outlet box for third pin "ground" running back to the circuit box to it's own isolated bus bar which connects to the neutral bus bar at the box and then to the ground bond.

This style of electrical wiring creates it's own "star ground" eliminating any extra wire connections between chassis or 0000 welding cables run to mother earth.  All chassis are referenced to the electrical box bond to mother earth.  With that electrical foundation, everything plugs three-wire to the electrics.

Then on to the audio wiring where I connect all shields at the patch bay connections, DL's here, and lift at the opposite end.  As written previously, all microphone lines and utility tie lines get shields tied at both ends- more for P48 considerations than "death prevention".  In the 80's I was a purist and would lift all shields at the "load side" of a run, but that would make a mess at the DL's under the bay and make outboard changes more difficult that necessary- sometimes KEY inputs were on the top row or reverb AUX outs on the bottom.  Very 20th century and not much of an issue these days!  There are not many studios left with 32 I/O of digital reverb or a couple of Kepex racks.

As mentioned sometimes amplifier runs or vintage outboard would want to be connected at both ends, but everything else multitrack tape, DAW, outboard (except mic pre inputs!), externals, etc. has the audio shield lifted at the equipment end not the console end.

Not mentioned yet is what to do once you have everything wired.  You want to connect the room one system at a time.  Start with the monitors DL and test all monitors for noise.  Add multitrack outputs and listen (carefully!) to the noise floor.  Continue step by step with the multi inputs, aux i/o, outboard, etc. one DL at a time listening to the noise floor at each step.  It is easy to identify any problem equipment this way.

I think that anyone integrating an SSL into a studio is already starting with a HUGE advantage in regards to noise floor and "grounding".  One thing I had to deal with during the transition from tape and consoles to "boxes" was the lack of heavy metal in the room.  Besides the SSL overall quality, grounding is much easier with at least one huge chassis relative to everything else in the room.  It creates a greater potential for the flow of noise to ground.  The dynamics of grounding and system noise elimination are completely different when all of the chassis are relatively the same weight except maybe a large power amp.
Mike
PS: It's been years since I had a 4K bay out to tighten patchpoints, but I swear that all internal wiring shields are connected to bay sleeves in both integral and remote patchbay consoles.  Maybe a lift at the inserts only if any.  I always respected the tight wiring work and all that black shield sleeving.  Big sleeve fan here.

[madmuso]

Thanks for the replies and great info and advice guys! This is awesome.

I have finally begun testing the outboard via send and returns and insert points, as well as using small faders as fx sends. Every XLR to DL loom (for the outboard) is all balanced and so far there havent been any hum or interference issues and the system seems to be very very quiet, so we are happy about that. Obviously I havent had the chance to test out many different "real world" scenarios as there are a million possible combinations but as we use the studio more im sure some "grounding" teething issues will arise, at that point I will address them.

I do have a question though regarding the group outs on the console. I had the console in mix mode today and was using the small fader on a channel as an fx send, (i pressed the output button next to the small fader and in the routing matrix i pressed number 4) I patched group out number 4 to the input of a reverb unit, then patched the reverb units returns to a spare channel.
I happened to notice that channel 4 on our AD converters was also lighting up, so this meant that not only was the signal coming out of the group out patch row but was also simultaneously feeding the multitrack sends row beneath it. Is this normal? I thought the group outs only feed the multitrack send patch row when the "direct" button is pressed.

thanks guys, and hope you are all well!

[michaeldtech]

Group Out=Multitrack Send. You can either deadpatch the multitrack in, set DAW meters to output or ignore.
Mike