A little off balance

[JohnnieB]

This is going to showcase some ignorance on my part but, I feel I got somewhat deceived by the company I bought my amp from. The company states my two channel amp is fully differential. Come to find out, that only applies to the input. The amp has XLR inputs but is not fully balanced thru to the output. Does this sound right? I understand that fully balanced designs are more expensive. Expensive being somewhat conjectural. I am happy with the sound and power of the amp, but feel somewhat misled. Probably my fault for not doing enough research. Am I missing out on cleaner sound by not having a fully balanced signal from start to finish? Would like to sort this out for future reference.

 

[AcuDefTechGuy]

Which amp is it?

Most amps are not fully balanced and they still sound great.

 

[slipperybidness]

This is going to showcase some ignorance on my part but, I feel I got somewhat deceived by the company I bought my amp from. The company states my two channel amp is fully differential. Come to find out, that only applies to the input. The amp has XLR inputs but is not fully balanced thru to the output. Does this sound right? I understand that fully balanced designs are more expensive. Expensive being somewhat conjectural. I am happy with the sound and power of the amp, but feel somewhat misled. Probably my fault for not doing enough research. Am I missing out on cleaner sound by not having a fully balanced signal from start to finish? Would like to sort this out for future reference.

Fully balanced designs absolutely have better specs on paper and by measurements. There are some advantages to the balanced input stage, but not as good as the full balanced design. In the consumer arena, you most likely won't notice any different with balanced vs. single ended, unless you are in a EM/RF noisy environment.

I agree with you 100% though. I think that the companies putting in unbalanced XLR connections or XLR connections with only a balanced input stage are being somewhat misleading. There was a previous thread where we were talking about the Parasound Halo series and how they do this practice.

What amp are you talking about here?

 

[Swerd]

This is going to showcase some ignorance on my part but, I feel I got somewhat deceived by the company I bought my amp from. The company states my two channel amp is fully differential. Come to find out, that only applies to the input. The amp has XLR inputs but is not fully balanced thru to the output. Does this sound right? I understand that fully balanced designs are more expensive. Expensive being somewhat conjectural. I am happy with the sound and power of the amp, but feel somewhat misled. Probably my fault for not doing enough research. Am I missing out on cleaner sound by not having a fully balanced signal from start to finish? Would like to sort this out for future reference.

By a balanced output from an amp, I take it you mean speaker outputs? Wouldn't that also require speakers with "balanced" inputs? I don't believe that exists, certainly not in home audio.

I'm also on weak ground here, but I don't believe speakers have or need such a thing.

Balanced audio - Wikipedia, the free encyclopedia

Internally balanced audio design
Most professional audio products (recording, public address, etc.) provide differential balanced inputs and outputs, typically via XLR or TRS phone connectors. However, in most cases, a differential balanced input signal is internally converted to a single-ended signal via transformer or electronic amplifier. After internal processing, the single-ended signal is converted back to a differential balanced signal and fed to an output. A small number of professional audio products have been designed as an entirely differential balanced signal path from input to output; the audio signal never unbalances. This design is achieved by providing identical (mirrored) internal signal paths for both pin 2 and pin 3 signals (AKA "hot" and "cold" audio signals). In critical applications, a 100% differential balanced circuit design can offer better signal integrity by avoiding the extra amplifier stages or transformers required for front-end unbalancing and back-end rebalancing. Fully balanced internal circuitry has been promoted as yielding 3 dB better dynamic range, as explained above.

 

[JohnnieB]

Emo XPA-2. As I stated the amp sounds great, I don't have any complaints. Just feel it's a bit of a bait and switch. This brings up another issue. Given the short runs of my interconnects, the benefits of XLR are arguable, so why put the XLR in the amp in the first place?

 

[RichB]

An amplifier with a balanced input stage can still provide common mode rejection and reduced noise.
I have heard this in my system even though the A51 is not balanced.

I have a BDP-105D dedicated XLR (Balanced) and RCA (unbalanced) connected to the Oppo HA-1 that is XLR connected to the Parasound A51 amplifier.
The BDP-105D is not balanced, the HA-1 is balanced, and the A51 is not fully balanced.

The unbalanced connection has more noise than the XLR's from the 105D.

- Rich

 

[Swerd]

This brings up another issue. Given the short runs of my interconnects, the benefits of XLR are arguable, so why put the XLR in the amp in the first place?

Because XLR connections are in demand among the audio fashionistas. The manufacturers would rather include it than risk loosing potential customers – even if they know it won't make a difference.

Something similar goes on with speakers with "bi-ampable" speaker connections.

 

[AcuDefTechGuy]

Emo XPA-2. As I stated the amp sounds great, I don't have any complaints. Just feel it's a bit of a bait and switch. This brings up another issue. Given the short runs of my interconnects, the benefits of XLR are arguable, so why put the XLR in the amp in the first place?

Emotiva says the XPA-2 is dual differential, which means it is fully balanced.

 

[PENG]

Emotiva says the XPA-2 is dual differential, which means it is fully balanced.

IMO the technical benefits with fully differential implementation is likely not audible to most people. It may also do more harm than good if not done right such as not hand picking/matching components to ensure practically identical characteristic in the + and - lines. I wouldn't mind fully differential preamp (mine is) but matter less to me for the power amp.

 

[AcuDefTechGuy]

IMO the technical benefits with fully differential implementation is likely not audible to most people. It may also do more harm than good if not done right such as not hand picking/matching components to ensure practically identical characteristic in the + and - lines. I wouldn't mind fully differential preamp (mine is) but matter less to me for the power amp.

How do we confirm that the dual differential was implemented optimally or correctly? When the measurement look great?

Do we have measurement of the XPA-2 or any Emotiva fully balanced amps to confirm that their implementation was optimal?

I don't think I could tell a difference. But I admit the fact that the ATI 3000 & 2000 amps and the Denon AVP-A1 are fully balanced appealed to me when I was buying.

 

[Speedskater]

...................... This brings up another issue. Given the short runs of my interconnects, the benefits of XLR are arguable, so why put the XLR in the amp in the first place?

Experts ask "Why didn't we stop using RCA connectors 50 years ago?"
An RCA interconnect and a high-end component is an oxymoron.

And fully differential from input to output is a solution in search of a problem.

 

[AcuDefTechGuy]

My Pre-pro is fully balanced. My amp is fully balanced (connected XLR). I stream lossless music from my iPad to my pre-pro. So everything seems fully balanced. But then the amp outputs to speakers. Since most speakers have more distortion than amps and preamps, does it really matter all that much whether the amp and preamp are fully balanced?

 

[Irvrobinson]

From the Audioholics Emotiva RPA-1 review:


[/COLOR]Using balanced inputs, I measured 79dB (unweighted) with 145mVrms driving an 8 ohm load. With unbalanced inputs the SNR dropped about 2.6dB as expected.

From the Audioholics Emotiva XPA-2 review:

In bridged mode at the same power levels, the even order harmonics of the FFT spectral distortion profile appeared about 10dB better than unbridged mode, bringing it to near equal footing with the RPA-1 but able to belt out significantly higher power levels (nearly 4X the power of the RPA-1) when driven to its limits.

These measurements are proof balanced topology can pay off in amplifiers. Can you hear the difference? That's a separate question. But balanced amps can be measurably better.

 

[AcuDefTechGuy]

These measurements are proof balanced topology can pay off in amplifiers. Can you hear the difference? That's a separate question. But balanced amps can be measurably better.

That's what I'm thinking. Measurement should be better if they are implemented correctly (as PENG says).

But the bottleneck is the speakers (assuming the source is great), right? Even the best speakers will probably have at least a 1% THD and higher with increasing volume. And the speakers are never as flat as the amps either.

 

[RichB]

That's what I'm thinking. Measurement should be better if they are implemented correctly (as PENG says).

But the bottleneck is the speakers (assuming the source is great), right? Even the best speakers will probably have at least a 1% THD and higher with increasing volume. And the speakers are never as flat as the amps either.

Actually, 1% is too high. Here are measurement of the M105 which does significantly better than that at high-frequencies at 100 DB:

Revel Performa 3 M105 Bookshelf Speakers - HomeTheaterHiFi.com


Most measurements are single tone, occasionally two tone.
IMO, if components sound differently operating within their limits, then harmonics are a likely source; Not the difference between 100 DB and 120 DB noise floor.

I have seen FFT measurements with 10 simultaneous tones, that were pretty interesting. .. but they are not public. I'd like to see more tests like those.

For Balanced, I have had good results in noise reduction from XLR on 6-foot runs. Yes, its a rats-nest back there

- Rich

 

[AcuDefTechGuy]

Actually, 1% is too high. Here are measurement of the M105 which does significantly better than that at high-frequencies at 100 DB:

Revel Performa 3 M105 Bookshelf Speakers - HomeTheaterHiFi.com


Most measurements are single tone, occasionally two tone.
IMO, if components sound differently operating within their limits, then harmonics are a likely source; Not the difference between 100 DB and 120 DB noise floor.

I have seen measurements with 10 simultaneous tones, that were pretty interesting. .. but they are not public. I'd like to see more tests like those.

For Balanced, I have had good results in noise reduction from XLR on 6-foot runs. Yes, its a rats-nest back there

- Rich

Well, okay, some speakers have better THD than others. But how reliable are those speaker THD measurement? Gene had mentioned that speaker THD numbers don't have much weight as some people think.

Even so, the speaker frequency response is still not anywhere close to +/-0.01dB like most amps. If it's not the THD, it's something else - on-axis FR, off-axis FR, room interaction, cabinet resonance, etc.

Bottom line, speakers have a lot more variables that affect the sound than amps.

 

[RichB]

Well, okay, some speakers have better THD than others. But how reliable are those speaker THD measurement? Gene had mentioned that speaker THD numbers don't have much weight as some people think.

Even so, the speaker frequency response is still not anywhere close to +/-0.01dB like most amps. If it's not the THD, it's something else - on-axis FR, off-axis FR, room interaction, cabinet resonance, etc.

I think HTHFI is a solid review site, so I would say they are accurate. More sites should measure speakers for THD. That is a good thing right?
Speaker THD numbers (from manufacturers may not have weight) but measurements from competent review sites do.
Measurements must include cabinet references but of course the room is huge. No doubt.

THD may not tell the whole story since these are simple tones not the complex tones found in music.
There are two main schools of thought.

1) All decently engineered components with good measurements THD etc. sound the same.
2) Many sound the same but some do sound different.

If you believe options 2 can occur (as I do), then you must assume that the measurements are currently insufficient to completely evaluate performance.
Of course, components that measure badly are not likely to sound good to me

The OP is about XLR and from experience, they are far from useless and help reduce hum/noise.

- Rich

 

[slipperybidness]

The real advantages of a true balanced design, balanced is better for:

Long runs
Noisy areas
Very small signals (i.e. microphones)

If you aren't dealing with one of these situations, then good quality single ended RCA will almost certainly be "good enough" and the benefit of XLR most likely won't be audible.

Still, I would prefer the XLR, but I know it's not necessary

A question for the OP: How do you know that the XPA-2 is only balanced at the input? It says "dual differential" on the spec sheet.

 

[Irvrobinson]

That's what I'm thinking. Measurement should be better if they are implemented correctly (as PENG says).

But the bottleneck is the speakers (assuming the source is great), right? Even the best speakers will probably have at least a 1% THD and higher with increasing volume. And the speakers are never as flat as the amps either.

I agree with Rich. In the few distortion measurements I've seen of the latest speakers with the latest technology drivers, they measure lower than 1%, more like 0.5% or less, and that's without an anechoic chamber. That said, I'm not convinced of the audible superiority of balanced circuitry in my own listening tests, between balanced and unbalanced products of the same component type. Not that I consider those tests definitive or rigorous in any way, but if anything I was biased to thinking if a component has a superior design there's a chance one could hear an improvement.

 

[Irvrobinson]

Because XLR connections are in demand among the audio fashionistas. The manufacturers would rather include it than risk loosing potential customers – even if they know it won't make a difference.

Something similar goes on with speakers with "bi-ampable" speaker connections.

This is incorrect. For those of us who run long interconnects, like me, balanced cables have proven advantages in noise rejection. Second, XLR connectors are far and away superior to RCA connectors in mechanical integrity and ease of use. This isn't at all comparable to passive biamping connections on speakers.