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Determine balanced input/output from block diagram

matteorizzo

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The mixers:

Mackie MIX12FX
Diagram page 9: https://mackie.com/img/file_resources/Mix5_8_12FX_SS.pdf

Wharfedale 1202FX/USB
Diagram page 17: https://www.wharfedalepro.com/wp-content/uploads/2021/02/Connect-Series-Manual-new.pdf


Short question:

I'm trying to determine if these two mixers have proper balanced inputs and outputs.
The product pages and the labels make it look like they are balanced but I'd like to be sure (after I bought a controller with 1/4 inputs that turned out to be unbalanced).
I understand what balanced cables do but I can't read the diagrams.


Full question:

I'm setting up my first proper home audio system and made a lot of mistakes. I now understand the importance of balanced connections and I'm trying to rectify my routing.

I have 3 audio sources, all outputs are balanced now. Audio goes to a pair of powered monitors with XLR inputs. Should be good so far.

The problem is the connection in between. I've been looking for a mixer with balanced I/O.

I don't want to make the same mistake I made by buying a "Swissonic M-Control +" which after a closer look, offers no balanced I/O at all (that's where the confusion started for me).
Link to details: https://images.static-thomann.de/pi...0_c_438690_quick_start_guide_v2_en_online.pdf

XLR is (usually) balanced. RCA is always unbalanced. But most budget mixers use a pair of 1/4 input jacks and they remain misterious to me.
I do understand I need TRS cables in between, but if I understood correctly using them is not enough: the inputs and outputs need to treat the signal for it to be balanced right?

I've been reading for a couple months now and I'm still confused, so I apologise if I'm asking basic questions.
 

charleski

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Both diagrams show differential inputs going to the + and - inputs of an opamp, so according to the diagrams you should be fine.
 

solderdude

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XLR is (usually) balanced. RCA is always unbalanced. But most budget mixers use a pair of 1/4 input jacks and they remain misterious to me.
I do understand I need TRS cables in between, but if I understood correctly using them is not enough: the inputs and outputs need to treat the signal for it to be balanced right?

XLR is different from TRS (when used in mono, balanced) situation.
Both can carry +, - and neutral but the XLR has a separate 'ground/shield' connection where this usually is combined on a TRS on the S connector.
This could make a difference on a stage or under circumstances with lots of interference signals near the (many) audio cables.

Another difference is that when using a TS (not balanced mono) source on a TRS input the - signal is automatically shorted to neutral (ground) where with XLR one would have to connect the - and ground pin in the connector.

A problem in the balanced world for TRS jacks is that when plugging a TS cable into a TRS output one shorts the - output signal to neutral (ground). Depending on the used output construction (resistors or current limiting) this could lead to distortion being added.
 
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matteorizzo

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Could you not use 75 Ohm RCA coaxial cables?

Well that's what I'm trying to do by choosing mixers with (hopefully) balanced 1/4 jack inputs. Or am I missing something? Is 1/4" somehow the same as RCA?

(Just in case you're referring to the Swissonic passive controller I'm currently trying to replace with proper mixers, I'm not using the RCA anymore - but all other inputs don't seem to be balanced anyway)
 
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matteorizzo

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Both diagrams show differential inputs going to the + and - inputs of an opamp, so according to the diagrams you should be fine.

Thank you very much for your reply.
After also comparing those diagrams to other mixers they do seem to be quite different, but I was waiting for someone with an actual understanding to confirm.
Hopefully in the future I'll understand what those arrows and dots coming from the ground and touching the signal mean.

( I went for the Wharfedale - got it just in time at 100€ instead of 160€ )
 
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matteorizzo

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XLR is different from TRS (when used in mono, balanced) situation.
Both can carry +, - and neutral but the XLR has a separate 'ground/shield' connection where this usually is combined on a TRS on the S connector.
This could make a difference on a stage or under circumstances with lots of interference signals near the (many) audio cables.

Another difference is that when using a TS (not balanced mono) source on a TRS input the - signal is automatically shorted to neutral (ground) where with XLR one would have to connect the - and ground pin in the connector.

A problem in the balanced world for TRS jacks is that when plugging a TS cable into a TRS output one shorts the - output signal to neutral (ground). Depending on the used output construction (resistors or current limiting) this could lead to distortion being added.

Thank you for your reply, very interesting!

I first heard about the shorting when it comes to guitars, where it's intentional. I'll keep it in mind from now on.

I have a couple of unbalanced outs (ie an RCA from a midi controller, no other options).

On those I put a ground lifting box in between: RCA in the box, TRS cable out of it, so I'm assuming that should carry the signal as TRS and not short it? Or am I still missing something?
 
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matteorizzo

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Some extra context:
- cable runs are relatively short (longest cable is 10 meters and it's the XLR going to the speakers)
- I'm keeping inevitable unbalanced connections (RCA and 3.5mm stereo) as short as possible to then (next point)
- "convert" those with a passive DI box before using a TRS cable to go to the mixer

The box I use to (hopefully) lift ground is the Behringer HD400 Passive DI Box.
 

charleski

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If I can put on my pedantic hat for a moment
c28d4027-8ad6-4986-bf75-6a1e9787d373.png


I'll point out that 'balanced' and 'differential' are actually different concepts:

Your passive DI box works by feeding the signal into a couple of small line-level transformers that break the ground connection and produce a differential output that should be balanced as well. For low-power, low-voltage situations like this the transformer can be a lot smaller than those needed for speaker-level signals.
 
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matteorizzo

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If I can put on my pedantic hat for a moment

I'll point out that 'balanced' and 'differential' are actually different concepts:

Your passive DI box works by feeding the signal into a couple of small line-level transformers that break the ground connection and produce a differential output that should be balanced as well. For low-power, low-voltage situations like this the transformer can be a lot smaller than those needed for speaker-level signals.

You're more than welcome to! I'm here to learn and do things right : )

So it's actually even more complex than I anticipated. It's clear now that I need some more reading to understand this fully, in the meantime thank you for your replies : )
 
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