Balanced output to unbalanced Input, to Float pin 3 or short pin 3 to Grd?

[ecc83]

""

On the other output Non-Transformer Post Mic OP.... I get pin 2 tip to 3 ring = 199 k ohm. So this data shows it is fitted with a "DC Drain resistor"
Now pin 1 to 2 is 100k ohm and pin 1 to 3 is 100k ohm.

I would say that is an impedance balanced output. You should be able to use a TRS jack to jack cable and not link anything.

No, very unlikley you will damage an op amp with a short but not a good idea. A discrete, 'snake oil' output stage* could well suffer damage.

*Yes, I know! There are vintage designs that peeps claim a great 'sound' from...Yer pays yer money?

Dave.

 

[CoolCat]

While on this topic, appreciate the info. , the LOAD or Audio Interface

The audio interface is Line6 UX8, says Unbalanced Line In..... it has a 3 prong 1/4" jack? not 2 prong.

Out of curiousity I stuck in a TRS 1/4" cable and measured Tip to Ring to Sleeve.
Oddly I didnt get 0 ohms between Ring and Sleeve? the unit was powered off.
Powered up I got a 3V dc from Tip to Sleeve but nothing on Ring?

I suppose the correct is a T/S jack for Un-balanced, but then why does it have the 3-prong jack in the interface pcb and not a two conductor female?

 

[ecc83]

While on this topic, appreciate the info. , the LOAD or Audio Interface

The audio interface is Line6 UX8, says Unbalanced Line In..... it has a 3 prong 1/4" jack? not 2 prong.

Out of curiousity I stuck in a TRS 1/4" cable and measured Tip to Ring to Sleeve.
Oddly I didnt get 0 ohms between Ring and Sleeve? the unit was powered off.
Powered up I got a 3V dc from Tip to Sleeve but nothing on Ring?

I suppose the correct is a T/S jack for Un-balanced, but then why does it have the 3-prong jack in the interface pcb and not a two conductor female?

Inventory: If the factory are using 10,000 TRS jacks a week it is simpler not to bother stocking a TS when it makes no difference to the operation.

Dave.

 

[CoolCat]

hmm? so basically just a TRS jack with no circuit to the ring. interesting and makes sense.

funny and really nice manual on all this balance unbalance is the APHEX 207 manual! I was moving on to that preamp and pg 26 or so shows a good deal of connections.
very similar to the RANE link. It does show to float the pin 3- for Voltage Balanced to Unbalanced, and IMpedance Balanced circuits though.
However the APHEX Unit seems to have a XLR out and 1/4" Out...not to short 3 to 1 sometimes....

of course if a person doesnt know what circuit they have none of it would matter and they could "smoke the curcuit", or just rely on the geargod to help.

added some screen shots but for another confirmation the Transformer does show to take Pin 3 to Pin 1, which is what everyone here has said (not Focusrite?).

imo all this is not 101 basics, a bit more knowledge needed and many manuals dont include it. Makes me wonder when people say "this sounds like ASS!!? and maybe have a wrong cable or mismatched chain?"

If I had only floated pin 3 for the transformer out, like FS mentioned, it sounds like ASS, but tying 3-1 its huge full sound, different in a huge huge way. Yet the 430 manual says nothing about this? DO they assume people/users already know? I wonder.

Thanks for the Electronics Class!! Lab!! Dave....also the assuming guess of why L6 might use the 3 prong for a TS, that one has boggled my mind before too.

 

[rob aylestone]

We are making this entire thing way way too complicated. Unbalancing is simply giving one of the signal pair a link to ground, so it does two jobs. Output devices have always been immune to shorts because jack plugs forever have a habit of shorting when a unbalanced one is shoved into a balanced output. Balanced on a jack socket just didn’t care if one leg was shorted to ground. It works by default. All we are doing is using a different connector. All we have is a really tiny audio current. For sixty years we’ve been shorting them on old tube gear, transistors then ICs. That simple resistance test shows it all. Both pin 2 and pin 3 have the same electrical state, so short either of them, it doesn’t matter.

Did you notice the spec given for the socket? 0 degrees and 180 degrees? Even that is wrong. Phase differences suggest a time difference, which there simply is not! Like when we stopped calling the switch that changed polarity, ‘phase’. It never changed phase, ever - but it was a convenient term. The only accurate way to talk about the difference between pin 3 and pin 2 is by saying pin 2 is positive going, when pin 3 is negative going - as in when the audio starts, does it go one way or the other. Hot or cold works for me too. Clearly one does not start later, but manufacturers seem very unsure how to indicate it. They can’t say plus or minus, or hot and cold or 0/180 degrees, or enthusiasts moan.

pick 2 or 3. Ground it to 1. job done. The key thing in your studio and kit collection is to ALWAYS do it the same way.

 

[ecc83]

I totally agree with you Rob...almost! For sure 'back in the day' kit did not mind if one leg was shorted because valve gear used a cathode follower OP stage driving a transformer and the secondary winding was floating i.e. not referred to chassis so it did not matter if you grounded it. In fact, as has been explained you HAD to ground the ring/P3 side to preserve a signal if driving an unbalanced input.

The coming of discrete transistor OP stages would I assume use series resistors but I don't have any schematics of discrete balanced drivers. Neve solved the problem of course with a socking great 2N3055 transistor driving a traff so, same as a valve.

The situation is different for an IC driver. Short one output and the op amp will still drive current into the series stabilising* resistor, likely about 75 Ohms. Naturally the amp will clip severely and could induce spikes into the other stage with which it shares a substrate. With noise floors now typically below -100dBu such clipping could easily be audible. In days of tape? Nah.

As for "kit being capable..." At least one top end headphone amp maker's product sports the now fashionable 'near zero output Z headphone outputs and cautions against plugging in a TS plug. I have news for them? 'IT'APPEN!

*All such output devices need a series impedance (R or L ) to isolate the active device from cable capacitance. If a resistor usually in the range 47 to 100 Ohms.

Dave.

 

[CoolCat]

last, I wonder is there any need to know what the Line In is on the audio interface?

the manual says UN BALANCED LINE IN on the audio interface, but it has a 3 Prong TRS socket soldered in. (maybe a cost savings in mfg.?)

I stuck in a TRS 1/4" cable in the socket and measured on the other end of the cable. I expected Sleeve/pin 1 and Ring/pin3 to be 0 ohms TS, but it wasnt.

Tip/pin 2 is Signal and readings were Tip to Tip= 0 ohms, Tip to Ring is 400k ohm, Tip to Sleeve is 10 k ohms.
Ring to Ring is 0 ohms, Ring to Sleeve is 400k ohm.

Which I was expecting Ring to sleeve to be 0 ohms if its a TS unbalanced circuit? but instead theres 400 k ohm.? any idea why?

I guess I can just plug anything into it and the op amps can handle shorts to grounds, but the tone differences kind of answer the question too I guess?
My other concern is I have one UX8 in the garage dead, the mic/line inputs are shot and were burnt out somehow?, the headphone amp and lights and USB seem to work, but its like ALL the preamps are shot.
I bought another one this weekend for $65+shipping and it works perfect. But I wanted to make sure I didnt short the other or something.
I have a 3rd UX8 that works perfect too but it has no outboard other than a DI and the rest microphones straight in, no Outboard interfacing.

Im not convinced a human cant damage these units with wrong cables or mismatched config's.... I could be wrong, maybe the burtn out unit just blew a cap or something that effected the whole unit?

 

[rob aylestone]

Not sure in this particular case, but 3 circuit chassis jacks are usually cheaper than 2 circuit ones. The mouldings for this are the same, so it's just simpler to make 3 circuit and even if it's an unbalanced connection just link sleeve and ring on the PCB. It's also a simple way to interface a balanced or unbalanced output or input. If an unbalanced plug is shoved in, then it automatically unbalances the balanced output, but if a 3 circuit plug is put in, balanced operation happens without thought.

 

[CoolCat]

just to add some more confusion...another F-rite tech support responded to my question saying "definitely dont tie 3 to pin 1..."
but this is bad advice? I wonder if the Tech Supports are even looking into which unit Im talking about or are they just in a hurry to say anything and close the thread?

ive gotten good advice before form them, like old part numbers from Mouser etc....but this one I have both TechExperts saying wrong advice?

 

[ecc83]

just to add some more confusion...another F-rite tech support responded to my question saying "definitely dont tie 3 to pin 1..."
but this is bad advice? I wonder if the Tech Supports are even looking into which unit Im talking about or are they just in a hurry to say anything and close the thread?

ive gotten good advice before form them, like old part numbers from Mouser etc....but this one I have both TechExperts saying wrong advice?

Tying pin 3 to pin 1 will do no immediate harm with a modern AI such as a F'rtite. Try first with it O/C.

The world has become dumb. Trying to get information from almost any organization is maddeningly difficult (I tried a surgery a week ago "you are number...sixteen in the cue") 'king ridiculous. Even if you get hold of a person they are probably not qualified to give an answer to a specific question.

Back in the day I could phone up Sony UK, Hitachi, Ferguson, Grundig, Philips and others and be put through to a technical guy in seconds. They all just want to save money and good people COST!

Dave.

 

[CoolCat]

maybe its the "cycle", the senior with 35 yrs experience experts...retired or kicked the bucket....

the new ones have more experience but only 5yrs, now its 5 yr Experts, maybe they know software, not hardware, maybe they have experience withUSB, Apple vs Windows, and mainly deal with plugins on Scarletts and not ISA 110?

 

[rob aylestone]

I've had a five email too and fro, and eventually the response was, One of our senior team has conformed you are correct and this will be rectified from the next invoice, however we are unable to process refunds for over payment made during this time - we suggest you take this up with XYZ company. So - the person in customer care made her own decisions and confirmed them many, many times, eventually discovering she was wrong. Trained to the lowest denominator, not the highest. No knowledge, but wielding power. Bad combination.

I and others have been unbalancing by grounding since we started - 73 for me. The only time it ever caused issues was when a manufacturer, I'm sure you can guess who, brought out a range of kit that did it the 'wrong' way, and a cable used in unbalanced mode both ends would be totally shorted, 2 to 1 at one end and 3 to 1 at the other. If we had had forums back then, it would have been amazingly useful. EVERYONE carried an XLR polarity swapped adaptor!

 

[CoolCat]

thats a funny thought, 3 to 1 on one end and 2 to1 on the other..lol.

I was reading unbalanced line in was and is pretty common on classic mixing boards. Never have owned one...TRIDENT etc...unbal line in.

re read that RANE, specific to transformer balanced to line IN unbalanced the chart and drawing clicked.
Not to beat it to death.... RANE shows 1 to 3 tied together.

 

[gianluca68]

If they say to leave pin 3 open, it is because pin 2 and pin 3 are simply two outputs with opposite polarities. It isn't a transformer or servo-balanced output. You can take the signal from one of the two pins. In a transformer (floating) output, if you take the signal from a pin leaving the other disconnected you have o signal, because it is like a battery with one of the two poles disconnected!
Anyway, there is no risk connecting a low level signal to gnd, because signal is low and impedance is enough to limit the current.

 

[drtechno]

Just an old revisit relearn.I was confused. I have a Focusrite XLR balanced output of a Rack unit and a 1/4" unbalanced Line IN on the Line 6 interface. No schematics.

Focusrtie tech support says "float" pin 3.
Seems others say "never tie an output to ground!"
While many post around says its ok to short pin 3 to pin1.!!!...which is what confused me.

The Line 6 Tech support replied "do it either way and see what sounds better" pretty much. hmmm?

I went with "floater"...shorting an output to ground sounds too risky.
And its a Focusrite product and they said "float" pin 3 OUTPUT on ISA 430 to my unbalanced interface Line In.
**********************************************************************************************************************
All 3-pin XLR audio connectors (Outputs, Mic/Line Inputs, Insert Send & Return) are wired as follows:

Pin 1: Screen/Chassis
Pin 2: Audio 0°
Pin 3: Audio 180°

For an unbalanced connection you would leave Pin 3 floating. - Focusrite Tech Support
************************************************************************************************
Thanks for reaching out. It shouldn't matter, as the ring connection of the jack is not connected to anything. You can try it both ways to see if one or the other works better for your setup.
All the best, Line 6-Yamaha
*************************************************************************************

The Cable I have, with XLR to 1/4" TS, was opened up at the XLR end and Pin 3 was soldered to Pin 1!!!,
so I snipped it and now Pin 3 is floating.

I guess I dont have schematics for either unit, so I dont know. Seems the Line 6 interface Input is UNBalanced but I dont know with what? Op Amp I assume.
The ISA430 is transformer output BALANCED but there might be something else there too, the above shows there is a signal....180deg ...so doesnt seem right to short it to ground.

Just thought Id post this. Seems Floating PIN 3 is the safe route.
Maybe some volume loss? My line noise is on a desktop so not so worried about that line noise on long runs for this application.

Well, there are only two connections you can do balanced out to unbalanced in:


Pin 2+ to tip
Pin 1 to sleeve


This is called dc referenced common balanced to unbalanced. This means the DC grounds are connected between the two pieces of equipment and the signal common is referenced to DC ground in both units. The drawback of this connection is a -6db attenuation, and all power supply noise is applied to the signal. Some people like this connection because it attenuates it, but in certain situations, causes a ground loop (hum in the audio).

Pin 2+ to tip
Pin 3- to sleeve

This is called virtual ground reference balanced to unbalanced connection. This means the virtual ground from the previous unit is tied to the shared dc ground and signal ground of the next unit. The advantages of this are that you eliminate the ground loop that would be present in the other connection, and the signal maintains its signal level. The drawback to this connection is that the line level might exceed the maximum input level of the unbalanced connection (+22dbu vs +18dbu).


So there you go: the both ways you can do it, and the advantages and drawbacks to both.

BTW, It stills seems that Focusrite still have their heads up their butts when it comes to explaining things to people.

 

[ecc83]

The 'non-electronic' muso/recordist is often rather confused about balanced systems but in fact it is the 'normal' single source/destination (often called a "sink") electrical regime that is really the oddity.

All devices that generate an electric current, be that AC or DC must have at least* two connections, The humble torch battery has of course a positive terminal and a negative one and a lamp must have wires going to and from those terminals to make a "circuit" usually with a switch. The car battery is no different, Pos and neg but, cars are almost always made of metal, steel for the most part. It makes therefore for a huge saving of Copper wire to utilize the chassis and bodywork as the negative 'earth' return. Car electrics can be 'KING complicated. Think how much more they would be if every lamp, motor and heater had to have two wires instead of one! Cars made of GF need such wiring (and are a PITA to suppress!)
There are downsides of course. Anyone who has had an old car has surely had electrical problems due to a 'bad earth'.

Electronic gear is the same. Be it a pre amp or a telly, the power circuits are referred to a common side of the supply. Audio circuits almost all have two 'live' rails, positive and negative but zero volts is still the ground reference. This is where connecting external devices starts to get tricky, ground loop and all that swaddlin'.

Many years ago audio engineers solve the problem with transformers. Gear had outputs and inputs using transformers (N.B. a '600 Ohm' output transformer is a very different beast from a '10k line bridging' input transformer in fact the latter type is very rarely seen these days) But, traffs are bulky, expensive, prone to hum fields, degrade audio especially at very low and very high frequencies, need special terminations in many case (Google 'Zobel' network) so the practice has largely died out and ground loops continue to be a problem, compounded of course with the need to NOT compromise any safety measures.

*AC can have several outputs. Most of you will have heard of the "Three phase mains supply" and even the humble car alternator has effectively six phases. BUT leave that there. I am NO multi-phase power engineer!


Dave.

 

[CoolCat]

I will guess most "non electronic" musicians start with a guitar cable.
Then rise to the complex Mic XLR and maybe delve into the science of the instrument cable vs speaker cable.

Later on , if into recording gear and seeking holy grail sounds, the Engineering and Marketing confusion happens.
Questions of "Why do some preamps have transformers or not, discrete or IC or tube?" Things get more confusing and articles saying warm, clean, fuzzy, overdrive, Neve, Beatles mics lead to Neumann Mics, Preamps, Impedance, condensor, tube, hybrid..yikes! Input, Output, TRS , XLR, T/S Line, T/S Speaker and more.

Then mix matching Balanced and Non-Balanced gear might be asked to 1) get best signal transfer 2) not damage any gear.

I just assume Focusrite techs are a mixed bag, some have ISA experience aka Hardware, while many have 2i2 audio interface type experience and not up on Transformers instead USB and software expertise.

Why does one system offer balanced Line In and others offer non-balanced Line In anyway? just to save a buck it seems.

 

[drtechno]

I will guess most "non electronic" musicians start with a guitar cable.
Then rise to the complex Mic XLR and maybe delve into the science of the instrument cable vs speaker cable.

Later on , if into recording gear and seeking holy grail sounds, the Engineering and Marketing confusion happens.
Questions of "Why do some preamps have transformers or not, discrete or IC or tube?" Things get more confusing and articles saying warm, clean, fuzzy, overdrive, Neve, Beatles mics lead to Neumann Mics, Preamps, Impedance, condensor, tube, hybrid..yikes! Input, Output, TRS , XLR, T/S Line, T/S Speaker and more.

Then mix matching Balanced and Non-Balanced gear might be asked to 1) get best signal transfer 2) not damage any gear.

I just assume Focusrite techs are a mixed bag, some have ISA experience aka Hardware, while many have 2i2 audio interface type experience and not up on Transformers instead USB and software expertise.

Why does one system offer balanced Line In and others offer non-balanced Line In anyway? just to save a buck it seems.

I would naturally assume my fellow musicians wouldn't care very much about how things work, they just want to plug in and jam and just want to know how to hook stuff up nicely.

Later on, it seems they asked me about one complexity or another, because the internet if full of audiophile garbage propaganda to sell an item, and they wanted to know an opinion from me that builds and repair electronics including audio but it all goes down to this: Some audio units are created with the intention of being transparent, in the regards it only does its function (like compression), but some are intentionally created to enhance, transform, or 'color' the sound besides to provide its basic function. Now someone might use a device like a vacuum tube induce this characteristic, but in reality, it all depends on how the circuit is created to provide its 'coloring' effects. A tube circuit can be clean and transparent if it is created to do so.

mixing and matching different types of i/o (balanced & unbalanced) with someone that is conscientious of the quality of sound will try the possible connections with cabling, but in certain settings (like a bunch of rack mount unbalanced gear) most will use signal transformers to convert to a balanced audio to isolate the self noise the unbalanced units add when they are normally connected with unbalanced i/o.

I've notice over the years the simple mistakes new electronics engineers make get slowly incorporated into their gear. Even their ISA amp is a victim of this and why the older models are sought after by audio engineers that know and hear its differences.

A 100% balanced circuit is actually two unbalanced circuits where the signal's ground (actually its 'common' instead of 'ground' because its AC) is not referenced to the power supply and rejects differences between the inverted (-) and non inverted (+) signal. Creating a 100% balanced circuit throughout requires tight tolerances between the same parts the inverted signal and non inverted signal stages. So, a collector resistor in the + signal's 1st stage has to be exactly equal to the collector resistor in the - signal's 1st stage. So someone has to match these devices instead of throwing the parts in a hopper and have a robot indiscriminately insert it into the board at high speed. Besides high end equipment, no one designs these audio circuits this way. They make unbalanced circuits because its half the parts build, and its much easier to mass produce. On converters, there is little choices they have because they are using an IC someone else designed and have to conform to the design standards the IC was created. So, if TI only makes a usb a/d d/a converter chip and chooses to design it with unbalanced analog in, the circuit created around it has to created in the same unbalanced fashion. The only reason why an ic circuit like this would have a balanced input is that they purposely wanted a balanced input, but that stage's output is unbalanced. But a short answer is yes unbalanced circuits are cheaper to build.

Until sometime in the 70s unbalanced gear only existed in musical instruments. Mainly because the low noise amplifying devices that can be used as unbalanced signal circuits were not easily mass produced as it is today. The older analog mixers that all of them are unbalanced internally were much more expensive because they had to hand pick parts. Old studio guys still force balanced connection compliance because they know its the correct and established standard that studio signal interconnections should fallow. Unbalanced was a live sound interconnect (insert jack) and musical instrument interconnection and did not belong in the studio world back in the day.


BTW, I have Dave (ecc83) ignored on purpose because he rambles on sensuously in threads, and doesn't provide intelligent answers that make sense.

 

[ecc83]

I would naturally assume my fellow musicians wouldn't care very much about how things work, they just want to plug in and jam and just want to know how to hook stuff up nicely.

Later on, it seems they asked me about one complexity or another, because the internet if full of audiophile garbage propaganda to sell an item, and they wanted to know an opinion from me that builds and repair electronics including audio but it all goes down to this: Some audio units are created with the intention of being transparent, in the regards it only does its function (like compression), but some are intentionally created to enhance, transform, or 'color' the sound besides to provide its basic function. Now someone might use a device like a vacuum tube induce this characteristic, but in reality, it all depends on how the circuit is created to provide its 'coloring' effects. A tube circuit can be clean and transparent if it is created to do so.

mixing and matching different types of i/o (balanced & unbalanced) with someone that is conscientious of the quality of sound will try the possible connections with cabling, but in certain settings (like a bunch of rack mount unbalanced gear) most will use signal transformers to convert to a balanced audio to isolate the self noise the unbalanced units add when they are normally connected with unbalanced i/o.

I've notice over the years the simple mistakes new electronics engineers make get slowly incorporated into their gear. Even their ISA amp is a victim of this and why the older models are sought after by audio engineers that know and hear its differences.

A 100% balanced circuit is actually two unbalanced circuits where the signal's ground (actually its 'common' instead of 'ground' because its AC) is not referenced to the power supply and rejects differences between the inverted (-) and non inverted (+) signal. Creating a 100% balanced circuit throughout requires tight tolerances between the same parts the inverted signal and non inverted signal stages. So, a collector resistor in the + signal's 1st stage has to be exactly equal to the collector resistor in the - signal's 1st stage. So someone has to match these devices instead of throwing the parts in a hopper and have a robot indiscriminately insert it into the board at high speed. Besides high end equipment, no one designs these audio circuits this way. They make unbalanced circuits because its half the parts build, and its much easier to mass produce. On converters, there is little choices they have because they are using an IC someone else designed and have to conform to the design standards the IC was created. So, if TI only makes a usb a/d d/a converter chip and chooses to design it with unbalanced analog in, the circuit created around it has to created in the same unbalanced fashion. The only reason why an ic circuit like this would have a balanced input is that they purposely wanted a balanced input, but that stage's output is unbalanced. But a short answer is yes unbalanced circuits are cheaper to build.

Until sometime in the 70s unbalanced gear only existed in musical instruments. Mainly because the low noise amplifying devices that can be used as unbalanced signal circuits were not easily mass produced as it is today. The older analog mixers that all of them are unbalanced internally were much more expensive because they had to hand pick parts. Old studio guys still force balanced connection compliance because they know its the correct and established standard that studio signal interconnections should fallow. Unbalanced was a live sound interconnect (insert jack) and musical instrument interconnection and did not belong in the studio world back in the day.


BTW, I have Dave (ecc83) ignored on purpose because he rambles on sensuously in threads, and doesn't provide intelligent answers that make sense.

I have just deleted that ramble. Something important came up and I had to leave it unfinished.

Dave.

 

[ecc83]

The Old Rambler* is about to comment. "Balanced" audio of course started with the telephone (though the principles upon which the concept works go way back to Wheatstone) Even a hundred mtrs or so of unbalanced telephone line would pick up all the noise in creation.

Yes indeed, good noise rejection depends upon very accurately matched resistances around the input amplifier and this is expounded very well by D Self in his Small Signal Audio Design. He shows that although op amps can have massive intrinsic rejection ratios exceeding 100dB, practical circuits rarely do better than 70dB or so even with very tightly selected components. He does say however that using 1% resistors ratios of 45-50dB are easily obtained.

*Hmm, might adopt it as a new sobriquet?

Dave.