Merging vs switching with balanced signals

[Ropeburn]

You guys completely ignore the fact that TS/TRS is instrument standard and XLR connectors are comparably rare on these.

A big advantage they also have is switching jacks. Awfully practical not just for patchbays. Example Casio RZ-1 because it's sitting here:

That stereo out is usable in three ways:

1) stereo on 2xTS
2) mono mix on right, if no plug in left, like in picture
3) TRS stereo on left if no plug in right

All possible options, couldn't be better thought out. Switching stuff like that is everywhere on all kinds of gear. Try doing that with XLR. Switching XLR exists iirc but is hardly used anywhere. Because TS/TRS is ubiquitous.

 

[john61ct]

I do love me an up-facing Big Knob for MLP volume control, and source switching is icing in top!

control freak?

TC Electronic "Level Pilot"

Mackie's

Lots more options in the digital domain, especially PCs / DIY project components

 

[john61ct]

As for XLR vs 1/4"

So long as the wiring and ports are balanced

the plugs being XLR vs 1/4" TRS really is a non issue IMO, go with personal preference either way

bullet adapters are cheap, robust basically foolproof in either direction.

I happen to favour Combo ports on inputs (in either flavour but Neutrik preferred)

so an SE TR plug can be inserted without conversion, which can in turn be bullet-adapted to RCA analog if needed.

Am I wrong?

 

[john61ct]

Any custom wiring I order, usually from https://hartaudiocables.com

4-pin mini-XLR is the standardised termination they (and I now) use for any cables I think may need converting in future, if cheap bullet adapters aren't ready OTS

Called "modular interconnects" at that website:

Stock interconnects

Custom interconnects

Custom Twisted Braid Interconnects

Custom Braided interconnects

Gorgeous colours, very reliable build quality, reasonable pricing...

https://imgur.com/hk3Y1CR

 

[Parker_knoll]

In the end I've gone for one of those relay based volumes from AliExpress that I'll use for the vinyl only. I can use the digital volume on the DAC. I lack any overall master volume in that case but it's not really an issue since I'm only using one source at a time.

 

[john61ct]

In the end I've gone for one of those relay based volumes from AliExpress

Very interesting unit, please let us know how it goes once in use!

Is that what's known as a "ladder attenuator", supposed to be the cleanest analog type of passive attenuation ?

I am especially interested in the SE vs Balanced conversion aspect...

I notice they list three paths

1. Unbalanced input, unbalanced output.

2. Balanced input, balanced output.

Above no conversion ofc.

3. Balanced input, unbalanced output.

I wonder if they omit #4 Unbalanced input, (pseudo) balanced output

because it is shorting one of the balanced pins to ground (or Pin1 to Pin3?)

and this can be risky with some components?

I wonder if this path is physically blocked by this attenuator?

Or they justbleft it out of the feature list to reduce liability ?

...

#3 may not be risky like #4 but will likely (certainly since passive?) drop 6dB in signal strength, since the balanced input only sees one "leg" of the audio signal.

Plus ofc lose the noise suppression benefit.

 

[john61ct]

Does it use transformers?

If not, what functionality would passive ones add?

 

[Parker_knoll]

Does it use transformers?

If not, what functionality would passive ones add?

you can see the board on the listing. it doesn't look like it.

without googling, as I understand a balanced signal is:

1. sound programme
2. goes to ground
3. inverse of sound programme

So obviously the only way to have a fully balanced unit throughout would be to have a set of switchable resistors for 1. and another set for 3. Looking here I don't think that's what's going on, so the signal is unbalanced during the volume change. This is pretty common - none of those Chinese (Nobsound etc.) "balanced volume" controls on Amazon etc. are actually balanced, nor is the Palmer, nor the Mackie. The Heritage Audio Baby RAM I think is judging by the internal photo I saw.

But if there's no transformer to rebalance the signal, this can be done with an opamp. I don't know enough about electronics to be sure.

That said, for my use case this is moot - I'm going to run unbalanced vinyl into it and out of it into my two active EQ units which will then balance the signal.

 

[Ropeburn]

This is pretty common - none of those Chinese (Nobsound etc.) "balanced volume" controls on Amazon etc. are actually balanced, nor is the Palmer, nor the Mackie. The Heritage Audio Baby RAM I think is judging by the internal photo I saw.

I kept wondering about that (in general), and indeed it isn't:

Not a problem most of the time but definitely something you need to know.

Interestingly, this dirt cheap "Swissonic" (Thomann house brand) monitor controller I have does really seem balanced through. Hot and cold throughput is clearly separate (says ohmmeter), and the pot is 4-gang, so are the switches.

Seems like price isn't an issue, particular models and their design are.

 

[Parker_knoll]

I kept wondering about that (in general), and indeed it isn't:

View attachment 530676

Not a problem most of the time but definitely something you need to know.

Interestingly, this dirt cheap "Swissonic" (Thomann house brand) monitor controller I have does really seem balanced through. Hot and cold throughput is clearly separate (says ohmmeter), and the pot is 4-gang, so are the switches.

Seems like price isn't an issue, particular modelsand their design are.

tell me now, i could have saved some money! is it any good though?

Actually the balanced signal wasn't a deal breaker. I just want good consistent imaging.

Yes, in the Mackie "balanced" output two of the connectors go to ground. it's not balanced at all. Bit of a fraud to label it as such.

EDIT: hold on, that Swissonic (blatant copy of the Palmer btw) doesn't have balanced ins does it?

 

[Redacted]

"Actually the balanced signal wasn't a deal breaker. I just want good consistent imaging."

You think "imaging" stems from signals being balanced?

 

[Ropeburn]

tell me now, i could have saved some money! is it any good though?

Actually the balanced signal wasn't a deal breaker. I just want good consistent imaging.

Yes, the in Mackie "balanced" output two of the connectors go to ground. it's not balanced at all. Bit of a fraud to label it as such.

EDIT: hold on, that Swissonic (blatant copy of the Palmer btw) doesn't have balanced ins does it?

It's very good in the sense of just works. There must be some channel imbalance from cheap pot, but I didn't notice anything. Only use it at either half or full volume though, where pot tolerance usually isn't much of an issue.

So yeah, definitely balanced all the way through input, switches, and pot. Can't complain at all, especially for the price.

Edit @Parker_knoll it does have TRS input.

Overall very proper. Wouldn't have expected, a nice surprise.

 

[Parker_knoll]

"Actually the balanced signal wasn't a deal breaker. I just want good consistent imaging."

You think "imaging" stems from signals being balanced?

no. You've misunderstood me. I'll explain better.

I want to try the relay based attenuator because it should avoid the mismatches between the two stereo signals that can occur with a ganged potentiometer, as referenced by Ropeburn above. Whether it's balanced or not is less important to me since I'm not going to use it in a balanced context.

Is that clearer? I'm sorry if you don't like the word I used. Feel free to use a different one.

 

[somebodyelse]

Yes, in the Mackie "balanced" output two of the connectors go to ground. it's not balanced at all. Bit of a fraud to label it as such.

Cold goes to ground via a resistor that is presumably the same as the resistor between the output buffer and hot, matching impedance on both legs. That's what's required to maintain balance for the CMRR benefits, so there's no fraud although some refer to this arrangement as 'impedance balanced'. There's no need for both legs to be driven - that's more about getting a higher signal level when PSU rails are limited.

 

[Davey2156]

Cold goes to ground via a resistor that is presumably the same as the resistor between the output buffer and hot, matching impedance on both legs. That's what's required to maintain balance for the CMRR benefits, so there's no fraud although some refer to this arrangement as 'impedance balanced'. There's no need for both legs to be driven - that's more about getting a higher signal level when PSU rails are limited.

Very well stated.
Balanced interfacing doesn't require active signal on both legs.
This is a very common misunderstanding in the audiophile community.

 

[Parker_knoll]

Very well stated.
Balanced interfacing doesn't require active signal on both legs.
This a very common misunderstanding in the audiophile community.

thank you, that was also my misunderstanding

 

[Ropeburn]

Cold goes to ground via a resistor that is presumably the same as the resistor between the output buffer and hot, matching impedance on both legs. That's what's required to maintain balance for the CMRR benefits, so there's no fraud although some refer to this arrangement as 'impedance balanced'. There's no need for both legs to be driven - that's more about getting a higher signal level when PSU rails are limited.

"Bal/unbal" labelling on in/out here simply means "usable with" both, which it is. They certainly aren't lying directly.

However you can't expect a layman = average customer to know that. If I had no clue about these things I'd very much expect the whole thing to be balanced. It isn't even consistent with other gear of theirs, which has identical labelling but is indeed properly balanced, at least the i/o circuitry.

It's not fraud and legally perfectly fine. But misleading.

 

[somebodyelse]

Is that what's known as a "ladder attenuator", supposed to be the cleanest analog type of passive attenuation ?

No. A ladder is done with rotary switches to select a pair of resistors giving the chosen attenuation. The relay-based ones almost always switch in or out a series of attenuators, each half the preceding one until you reach the smallest step available, so you can achieve a lot of steps with only a few relays (2 to the power n steps for n relays). For a small example you could have 1dB steps with 1dB, 2dB, 4dB and 8dB attenuators, giving 16 steps with 4 relays. You need to be careful about the order they're switched in, or mute before setting volume then unmute, to avoid large intermediate steps in volume when one of the larger attenuators is switched out.

http://www.twistedpearaudio.com/docs/control/jt/jt2_schematic.pdf will be pretty close to the relay part - the control logic is another matter.
https://goldpt.com/attenuator_types.html shows the options for rotary switches, including the ladder.

 

[somebodyelse]

"Bal/unbal" labelling on in/out here simply means "usable with" both, which it is. They certainly aren't lying directly.

However you can't expect a layman = average customer to know that. If I had no clue about these things I'd very much expect the whole thing to be balanced. It isn't even consistent with other gear of theirs, which has identical labelling but is indeed properly balanced, at least the i/o circuitry.

It's not fraud and legally perfectly fine. But misleading.

I responded about the output which is balanced, but could be connected to a single ended input without issues. You're addressing the input which is more problematic depending on the implementation of the balanced source connected to it, as discussed in detail in the many threads where people ask about balanced to single ended cables.

 

[Redacted]

The important thing is using resistors that have very tight tolerances and to some extent low temp coefficients.
Any rotary or relay unit is only as good as the resistors (and for relays the lack of switching noise).
While dual-gang pots are poor at channel matching, a lot of modern kit eschews those and uses rotary dials that use sensors for pulses, so volume control is done using pretty accurate electronic voltage control, usually mapped using software - the latter often results in hilarious "knob spinning" (steady on Trevor!) until you get to a decent volume from zero.