Balanced or not balanced . . .

[HIFI]

I have no experience with Balanced XLR connections in any home audio I have owned.

 

I am seeking a new Amp (mono block) and new pre amp.

 

What is the advantage of XLR Balanced connections?

 

Does mating of different brands become more/less important?

 

Thanks in advance.

 

[barrows]

BALANCED

 

[Bob Stern]

A small minority of expensive preamps have a fully balanced topology. However, most preamps are unbalanced designs with an extra phase inverter stage to produce the inverted signal required for the balanced output. If you buy the latter type of preamp, you may be better off with unbalanced because you'll eliminate one stage of amplification.

 

However, some people (like me) require balanced cables to overcome hum problems.

 

Other advantages of unbalanced: The cables usually are cheaper, and they are available with countless varieties of exotic RCA plugs if you are into that sort of thing. Balanced cables mostly use XLR connectors made by Neutrik.

 

[HIFI]

Bob, thanks for helping.

 

You use balance to overcome hum. I have not experienced hum in the unbalanced RCA connected systems I have owned.

 

I have shopped amps and most of the Mono Block amps have both RCA and XLR inputs. While my question is not simply specific to "is there a SQ advantage' using XLR connections but do I now need even more careful matching of amp and pre amp. I am purchasing new amplification and pre-amp. Let's assume I would only consider a "Fully Balanced" pre-amp to mate with mono block amps.

 

[Christopher]

Personal opinion on balanced...

 

For me, “balanced” means fully balanced internal circuitry. In other words, not just XLR connections that are a connection "accommodation” without fully balanced internal circuitry inside the component. I think Bob just touched on this.

 

In my experience, fully balanced internal circuitry can have a solid advantage in noise rejection. It’s possible that balanced circuitry sounds better because it avoids extra amplifier stages and/or transformers that require front-end unbalancing and back-end rebalancing (and I trust there’s a lot more to it).

 

This being said, I have listened to...and experienced first hand...the downside of XLR connections with an amp that *did not have* fully balanced internal circuitry. It just didn’t sound right with XLR cables.

 

What was the amp?...Rotel RB-1080.

 

A few years ago, my system sounded less dynamic and less resolving with XLR connections vs single ended connections with the Rotel RB-1080. After I changed cables from XLR to single ended, the exact same amp sounded better.

 

Today, my system is balanced with Ayre gear and I would probably not go back to RCA. But, I think results can vary based on equipment and the quality of cables. Balanced may not *always* yield improvement.

 

On a side note, I still love my Rotel RB-1080 amp. Today, I use it with outdoor speakers and it really shines. And yes, I use RCAs with the RB-1080.

 

Barrows and Bob, please let me know if you have any corrections or clarifications re my logic on this.

 

Best regards

Chris

 

 

 

 

[barrows]

Has sonic advantages, but you really want components which are actually balanced internally to take full advantage of the sonic benefits, except, possibly, with power amplifiers.

 

Sources, you want balanced: most DAC chips have balanced outputs already, so converting to single ended actually requires the additional gain stage-this is usually accomplished with a high feedback IC opamp, even in expensive DACs with otherwise discrete circuitry like the dCS Debussy. If you use a DAC, you want a balanced one with balanced outputs to take advantage of the fact that the DAC chip itself has fully balanced outputs.

 

Preamps: if you use one, you want balanced, and as mentioned you want a balanced circuit all the way through.

 

Power amps: here, it gets tricky. You definitely want a true balanced input stage-this is where your final common mode rejection will occur, eliminating any noise pickup in the signal. But very many, excellent, true balanced input (meaning the input stage, usually the voltage gain stage) amplifiers have single ended current stages. My PS Audio Classic 250 is this design, a balanced voltage gain stage, followed by a single ended current stage. My PASS is also a two stage amp, but the currnet stage is also balanced. Some amp designers feel there is no benefit to balanced at the current out stage, and using balanced design there does raise the output impedance somewhat, so it can be a trade off. As long as the amp has a true balanced input stage, I would not worry about the current/output stage. The signal is at a high level at this point, and not easy to degrade. Choose the amp for how it drives your speakers, not whether it has a balanced output.

 

[winst]

Don't forget one very important factor,which is the ability of an output device being able to drive a signal at a required level into the input of device being fed.

In this case, if the driving unit have an output impedance of say 100k ohms and the receiving device input impedance is 10k ohms, then you would not be able to basically get full output of the receiving device say a power amplifier, because you would have just reduced that signal by 100k/10k or ten times less.

Most pro gear that uses xlr have very low input impedance on the order of 6k - 8kohms, so trying to connect a consumer driving unit to

a pro unit with xlr and or low in z creates a performance limitation.

Winst

 

[HIFI]

Barrows, thanks for you input.

 

How can I be sure a pre-amp is descrete and "Fully Balanced".

 

The reason I ask is what Bob mentioned earlier in this thread . . .

 

" A small minority of expensive preamps have a fully balanced topology. However, most preamps are unbalanced designs with an extra phase inverter stage to produce the inverted signal required for the balanced output."

 

As a follow up question is this aforementioned "quazi" balanced design in other products . . like DACS?

 

[sandyk]

Winst

The vast majority of DACs and preamps have an output impedance more like 100 ohms or less, although some may go a little higher. Anything MUCH higher and the treble would be terribly rolled off due to the interconnect's cable capacitance.

Alex

 

[dallasjustice]

It depends on the gear. Some manufacturers design their gear to sound best single-ended and some others favor the fully balanced design. I know there are many others, but Dartzeel and Spectral make excellent amps and pre-amps that are designed to sound better single-ended.

 

 

[barrows]

to do your research! Find the product you are interested in, and learn as much as you can about it.

 

It is unusual for a DAC to feature a "quasi balanced" design, but not unheard of. I am pretty sure, but not positive, that the Metric Halo pro ADC/DACs are "quasi balanced", this allows them to use single balanced DAC chips as four channel DACs (they are 8 channel products).

But most two channel DACs use DAC chips which are balanced on their own output-it would be really poor implementation to not take advantage of the balanced DAC chip output... Usually DACs with single ended outputs at least sum the two balanced outputs, rather than just taking half of the DACs output to make the single ended version-but I have seen DACs which do this as well (lame). And of course there are some DACs using old fashioned single output chips still. This can get quite complicated to think about-just one possibility among many: consider a true balanced output DAC, and a quasi balanced input preamp. If the preamp sums the balanced signal with, say a transformer, it will still be a big advantage to run balanced from the DAC to the preamp, as you will get the full advantage of common mode noise cancellation in the summing transformer.

Then, as mentioned by Dallas, there are unusual designs like Spectral, with their incredibly high bandwidth, entirely undamped outputs, which require special damped cables to keep the circuit stable, or dartZeel, who prefers that their gear be connected by a (mostly proprietary) impedance matched 50 ohm coax cable to reject noise. But those designs are exceptional, the vast majority of gear uses either traditional single ended and/or balanced connection on normal cabling...

There are a lot of true balanced preanps out there, they are not rare at all... most high end solid state preamps are balanced, and many tube ones as well. Most reviewers of any quality will reveal in reviews the internal general topology of components, I would not trust what most dealers will tell you, although there are exceptions. If you contact tech support at a manufacturer with questions about their product, reputable manufacturers should be able to tell you the truth. Although trying to distinguish between actual tech support and marketing can sometimes be a challenge, ask for tech support, not sales!

 

[Mark Powell]

You don't have to be. Does not matter a damn whether it runs on solid state, tubes, balanced or unbalanced, or as a set of miniature musicians inside.

 

Your ears, and only your ears, not the silly technicalities, such as how many pins there are on the ouput sockets, are the only things that matter.