Balanced output to SE RCA input - Harrison Labs?

[john61ct]

Need a converter/adapter gadget

balanced output from XLR or Phoenix block to a single-ended RCA input

Quality transformers are pricey, ART Cleanbox Pro gets reco'd a lot, others?

Harrison Labs' universal Audio Patch Board, aka "Audio Parametric Patch Board XLR-RCA-1/4" Phone - Euro"

if I read it correctly, claims to accommodate any combination of XLR, 1/4” TRS jack, or Euro block connectors on the balanced side, and RCA or any of the above as unbalanced

in both directions! (?)

(Besides him being a dogmatic whacko, let's ignore that here)

I am skeptical that this board is safe to use (by a relative noob) going in the Bal-->SE direction? without input from the manufacturer of the balanced source device?

I would prefer to keep to the general Q, but my specific case here, is an output balanced pre- signal from a Phoenix block, to the RCA input of an SE-only power amp.

I want to keep the advantages of balanced wiring (long cables, noisy env) if possible.

 

[john61ct]

Seemingly unrelated but for my education

Is it possible for RCA connections to ever be balanced?

AudioControl Concert series of old-school crossovers, e.g. 2XS 6XS

have RCA in/out connectors, but claim "balanced differential input circuitry"

There is a 3-pin "input ground isolation" jumper inside, they say provides a "hard ground" to accommodate balanced inputs. That is default, must manually disable in order to set to SE (if needed?)

An RCA connection only has two wires, so there's no way to send a balanced signal through it, right?

Is the jumper insulating the "hard ground" from the chassis?

Is "differential but single-ended" a thing?

Besides the general principles, is this feature actually useful for helping ensure SQ?

And finally, is AudioControl's general reputation well deserved in this ancient realm of non-DSP active crossovers? I love the swapping modules rather than twiddling knobs...

 

[DVDdoug]

If possible, check with whoever makes the device with balanced-out. Otherwise, it's best to use a transformer or active device.

(It's always safe to go the other way around from unbalanced to balanced, and you still get most of the benefits of a balanced connection.)

Is it possible for RCA connections to ever be balanced?

AudioControl Concert series of old-school crossovers, e.g. 2XS 6XS

have RCA in/out connectors, but claim "balanced differential input circuitry"

Yes! A balanced input can work without a ground. I actually built a circuit like that to solve a noise problem. In my case, it's driven from an unbalanced RCA output with the output-ground connected as-usual through the shield but to the minus differential input.

 

[john61ct]

If possible, check with whoever makes the device with balanced-out.

The example source here is

miniDSP Balanced 2x4, maybe the "in a box" OG version?

I'm sure the Phoenix wiring diagram is available, but I don't think that will help me given my noobish brain.

I am skeptical miniDSP support would address that specific HLabs board.

I wonder if Amir would accept it for testing?

 

[Devnull]

Before you start spending money on adapters or converters that probably aren't necessary try this. Get an old RCA cable and cut one end off. Center pin to + shield to - on the phoenix connector. That's all it should take. Unless you're in a really noisy environment that's needs noise rejection you won't hear a difference.

 

[john61ct]

Before you start spending money on adapters or converters that probably aren't necessary

Thanks but, I've seen too many warnings that doing that going in the Bal-->SE direction can short the channels and destroy the amplifier

The price of a happy meal is well worth the peace of mind.

B. > I want to keep the advantages of balanced wiring (long cables, noisy env) if possible.

This is for a mobile system, so both factors will arise from time to time.

3. My learning process is top priority here, over and above practical considerations. If you know of authoritative resources to help me understand WHY your reco is safe, please post links?

 

[john61ct]

A balanced input can work without a ground. I actually built a circuit like that to solve a noise problem. In my case, it's driven from an unbalanced RCA output with the output-ground connected as-usual through the shield but to the minus differential input.

Above my paygrade I'm afraid. :-(

I also found this Khadas device, must work the same way?

https://www.khadas.com /tone2

Total Harmonic Distortion (THD+N):
Balanced RCA: -118dB
Single-end RCA: -116dB

Maximum DAC Line-Output:
Balanced RCA: 4Vrms@20ΟΚΩ
Single-end RCA: 2Vrms@100ΚΩ

 

[Bruce Morgen]

Everything depends on how the balanced output circuit was designed. With some gear, you can connect one side (pin 2 on an XLR, or the "R" of a TRS to ground -- in the latter case, just use a TS plug) and it will work a treat, but not with others.

 

[Devnull]

Thanks but, I've seen too many warnings that doing that going in the Bal-->SE direction can short the channels and destroy the amplifier

The price of a happy meal is well worth the peace of mind.

B. > I want to keep the advantages of balanced wiring (long cables, noisy env) if possible.

This is for a mobile system, so both factors will arise from time to time.

3. My learning process is top priority here, over and above practical considerations. If you know of authoritative resources to help me understand WHY your reco is safe, please post links?

Your own post is why it's safe . It defaults to differential if the jumper isn't moved. So you're using differential from the miniDSP to the RCA which isn't tied to ground.

 

[john61ct]

Everything depends on how the balanced output circuit was designed. With some gear, you can connect one side (pin 2 on an XLR, or the "R" of a TRS to ground -- in the latter case, just use a TS plug) and it will work a treat, but not with others.

Exactly. I want a solution that can be safely used with any output device, without relying on my memory or my current level of understanding, which varies with the seasons or even time of day.

Paying a bit extra for that? Well worth it.

Hopefully not compromising SQ.

Switching amps is of course another option

 

[john61ct]

Your own post is why it's safe . It defaults to differential if the jumper isn't moved. So you're using differential from the miniDSP to the RCA which isn't tied to ground.

What jumper? Maybe I should not have mixed the AudioControl in here?

My current understanding is, RCA using only two wires means it CAN carry differential signal but from a physical connection POV it cannot be Balanced?

 

[Devnull]

In you second post you said
There is a 3-pin "input ground isolation" jumper inside, they say provides a "hard ground" to accommodate balanced inputs. That is default, must manually disable in order to set to SE (if needed?)

So you have two choices, default and use RCA to+ - on miniDSP or the SE position using + GND on the miniDSP.

Your are correct about RCA carrying differential unbalanced connections. Don't forget every electrical signal is differential.

Audio people are terrible electrical engineers that have bastardized and misused electrical engineering terms for years and make assumptions about signals based on the connector type.

 

[john61ct]

In you second post you said

Yes exactly, that post has little relevance to the OP question, it's just a side note.

Should have created two separate threads, I apologize for the confusion.

If you are still willing to help, maybe just re-parse the OP #1 and only answer the question(s) there?

Never mind for now about your wiring suggestion with regard to the miniDSP specifically.

What I am really after is the general principles, and only WRT that Hlabs adapter board.

 

[Devnull]

I have no idea about the Harrison Labs board. ART makes some quality hardware. Look at someplace like sweetwater for other hardware possibilities.

 

[john61ct]

Just a side note, not relevant to what I've clarified I'm looking for more generally, but this blog post

Easy RCA Inputs and Outputs for a 2x4 Balanced miniDSP

After hearing the difference between low-fidelity amusical bass (any system with "full range" stereo speakers, or speaker set crossed over ...

seriousaudioblog.blogspot.com

gives the same advice, for both input (NP SE-->Bal) and output (maybe risky Bal-->SE)

as

Get an old RCA cable and cut one end off. Center pin to + shield to - on the phoenix connector.

EDIT - Found the manual for that model miniDSP, gives the unbalanced wiring diagrams explicitly. The connection of Shield to Negative applies to INPUT only (SE-->Bal).

For output (Bal-->SE) Negative on the balanced terminal is left unconnected,

RCA Tip goes tp Positive, Ring goes to Shield.

So that settles that one device, but leaves my main more general query about the Hlab "universal adapter" board.

Can anyone tell which of these two schemes that implements by looking at the graphic? Or would some instrument be required to test with the board in hand?

 

[john61ct]

Apparently this Rane Note 110 "Sound System Interconnection", is canon

Rane Library

The Rane Library contains RaneNotes, technical papers, powerpoints, and advertising.

www.ranecommercial.com

Also found this later one "Grounding and Shielding Audio Devices" RaneNote 151

Grounding and Shielding Audio Devices

Since the Audio Engineering Society has adopted the "pin 2 is hot" standard, what is the correct use for pin 1?

www.ranecommercial.com

both way above my pay grade!

 

[john61ct]

Emotiva passive cable adapter designed for this use case, much simpler than the Hlabs board, so long as you have XLR male from your balanced output and RCA male from your SE input.

Balanced XLR to Unbalanced RCA Adapter Interconnect

The XLR to RCA Adapter delivers excellent electrical performance and protects the integrity of the audio signal in a slim, flexible cable. Shop online today!

emotiva.com

The Proper Way To Connect a Balanced Output To an Unbalanced Input

When connecting a balanced output to an unbalanced input on modern audio gear, the proper way to do so is to connect the non-inverted output on the balanced output to the unbalanced input, and leave the inverted output unconnected. Many adapter cables, designed primarily for use with microphones, short the unused output pin to ground. While most equipment, including ours, will tolerate this without damage, it is not recommended, and may unnecessarily stress the output circuitry on your processor or preamp. This adapter was specifically designed to work optimally on modern balanced audio gear - and leaves the unused output line unconnected.

I wonder if this scheme matches that in the miniDSP manual above

and/or the Hlab PCB's traces layout.

And completely new thought on the Hlabs board, the fact that it accomodates two FMODs

is that just for unbalanced 2-channel SE use (separate paths), or does it allow for Bandpassing one balanced channel?

 

[john61ct]

Found a very pertinent note from the late great Jim Williams *

> That's not a problem with the Adcom 555. Just ground the low side (ring or pin 3) if the driver circuit is transformer coupled or electronically cross coupled outputs. If they are inverter balanced outputs, float pin 3 or the ring. The Adcom's use a 2 wire AC cable so grounding loops are avoided. I've installed Adcoms in many rooms with many consoles and monitor output circuit designs. There is always an easy way to integrate the two.

https://gearspace.com/board/geekzone/324255-add-balanced-inputs-power-amp-bryston-adcom.html#post3457065

...

I assume "ground the low side" here means to attach to the cable shield - which in turn should be chassis-attached, which should be wired to true Earth ?

and that "float" means "leave that wire disconnected" ?

* of Audio Upgrades fame

https://www.modwiggler.com/forum/viewtopic.php?t=39862

 

[babadono]

Start out by trying the connection recommended by miniDSP.
+ of balanced out to RCA center pin and shield of output to RCA shield .This SHOULD work.

 

[john61ct]

Yes thanks, but I'm not looking for advice wrt for any particular device, I'm asking these questions looking to confirm I am understanding what I'm reading, from a general learning POV.

If you (or anyone) could please parse and respond in that light, I'd really appreciate it.