Fosi Audio ZA3 - XLR vs. RCA

[Steamrolly]

I was trying a comparison between my Fosi Audio ZA3 and SMSL AO200 amps combined with a SMSL DO300 DAC and Totem Skylight speakers. Using a dB meter, I wanted to compare volume variance between the two amps, XLR and RCA inputs and a couple pairs speakers but found something unexpected (to me anyway).

With the ZA3 with the volume set to 12’ O’clock there is a 6 dB (average) difference in volume between XLR and RCA whereas with the SMSL AO200 (with a volume level as close as possible) there is barely a difference (0.2dB) between XLR and RCA.

As I only have the two amps (with XLR) for comparison I am curious if this is, normal between various amps, an issue with the ZA3 or has SMSL compensated for a variance in signal from the DAC (XLR vs RCA) where FOSI has not? In other words, is this normal for the ZA3 or did I receive an amp where the gain is set too high on the XLR output similar to what Amir describes in his review? “Upon testing, I noticed that the gain was substantially increased…”

 

[MaxwellsEq]

If you have a device that does full differential working on its balanced input and is non-differential on its RCA input, then normally you would expect the balanced line to produce more output from a source that has a fully differential output on its XLRs and normal single ended working on its RCAs. If you don't get a difference, it might be that the gain is deliberately matched so that there is no difference in output levels, or it could be that something isn't actually differential when it should be.

 

[Steamrolly]

My first thought was that SMSL has deliberately matched the gain and Fosi Audio have not but I don't know what the industry standard is (if any) for amplifiers. It was due to @amirm 's comments regarding gain being increased on the initial ZA3 unit he received that made me question if I may have received a similar unit. That said I may have misunderstood his comments; it could be unrelated.

 

[Graham849]

Bit confused here. I used to run SMSL do100 xlr to AO200 and rca to Azur 650 and the Azur 650 speakers were loud at 11 o'clock.

Now running XLR to ZA3 stereo mode and RCA to Azur 650 and the Azur speakers are not loud at 4 o'clock.

Does the ZA3 xlr inputs suck power out of the DO100, leaving less for RCA?

 

[Graham849]

mea culpa, I had the ZA3 at 5o'clock, and controlling volume using DO100. Now DO100 at 90% and ZA3 at 12 O'clock all is well.

 

[LSPhil]

I was trying a comparison between my Fosi Audio ZA3 and SMSL AO200 amps combined with a SMSL DO300 DAC and Totem Skylight speakers. Using a dB meter, I wanted to compare volume variance between the two amps, XLR and RCA inputs and a couple pairs speakers but found something unexpected (to me anyway).

With the ZA3 with the volume set to 12’ O’clock there is a 6 dB (average) difference in volume between XLR and RCA whereas with the SMSL AO200 (with a volume level as close as possible) there is barely a difference (0.2dB) between XLR and RCA.

As I only have the two amps (with XLR) for comparison I am curious if this is, normal between various amps, an issue with the ZA3 or has SMSL compensated for a variance in signal from the DAC (XLR vs RCA) where FOSI has not? In other words, is this normal for the ZA3 or did I receive an amp where the gain is set too high on the XLR output similar to what Amir describes in his review? “Upon testing, I noticed that the gain was substantially increased…”

Symmetrical signal transmission, commonly used in professional audio systems, such as through XLR connectors, works in a way that significantly reduces noise while amplifying the signal.

Imagine that at the start, a single signal is split into two wires: one wire carries the signal in its original form, while the other wire carries the same signal, but inverted by 180 degrees (in opposite phase). Both wires run together, for example, inside a microphone cable.

If interference or noise occurs during the signal transmission (due to electromagnetic interference, for instance), the noise will affect both wires equally, with the same polarity, meaning it adds to both signals in the same way.

At the receiving end, before the signal reaches its destination (such as a mixer), the signal in the inverted wire is flipped back by 180 degrees. Now, both signals, which were previously out of phase, are aligned in phase and thus combine. This leads to a doubling of the signal's amplitude, which corresponds to a +6 dB boost.

However, the noise that was present in both wires in the same polarity is now out of phase after one of the wires is flipped. As a result, the noise cancels itself out (it subtracts), greatly reducing any interference in the final output.

To summarize, symmetrical signal transmission works by:

1. Transmitting two versions of the signal: one in the original phase and the other inverted.
2. Flipping the phase of one signal before the final reception, which leads to the signals combining and boosting the amplitude by +6 dB.
3. Noise, which affects both wires equally, is canceled out when the phase of one signal is flipped, leaving a cleaner output.

This makes symmetrical signal transmission highly resistant to interference, which is crucial for professional audio applications.

 

[40 Inferno]

I switched my ZA3's inputs from RCA to XLR and there was a noticeable increase in gain (that was my purpose, my gain is lowered during preamp for DSP to prevent clipping on Windows). I'd say I turn the volume knob 20% lower.

 

[Steamrolly]

For my ZA3, using a dB meter app for approximate levels, to achieve the same volume level as XLR at 9 o'clock and need to sent the volume at 12 o'clock using RCA.
I am curious if this is consistent for others with a ZA3.

 

[stupendousredman]

Symmetrical signal transmission, commonly used in professional audio systems, such as through XLR connectors, works in a way that significantly reduces noise while amplifying the signal.

Imagine that at the start, a single signal is split into two wires: one wire carries the signal in its original form, while the other wire carries the same signal, but inverted by 180 degrees (in opposite phase). Both wires run together, for example, inside a microphone cable.

If interference or noise occurs during the signal transmission (due to electromagnetic interference, for instance), the noise will affect both wires equally, with the same polarity, meaning it adds to both signals in the same way.

At the receiving end, before the signal reaches its destination (such as a mixer), the signal in the inverted wire is flipped back by 180 degrees. Now, both signals, which were previously out of phase, are aligned in phase and thus combine. This leads to a doubling of the signal's amplitude, which corresponds to a +6 dB boost.

However, the noise that was present in both wires in the same polarity is now out of phase after one of the wires is flipped. As a result, the noise cancels itself out (it subtracts), greatly reducing any interference in the final output.

To summarize, symmetrical signal transmission works by:

1. Transmitting two versions of the signal: one in the original phase and the other inverted.
2. Flipping the phase of one signal before the final reception, which leads to the signals combining and boosting the amplitude by +6 dB.
3. Noise, which affects both wires equally, is canceled out when the phase of one signal is flipped, leaving a cleaner output.

This makes symmetrical signal transmission highly resistant to interference, which is crucial for professional audio applications.

I agree. What's important is that with the XLR output, as opposed to the RCA, from ZA3 to my KEF LS50 META's I can hear so much more dynamism, detail and clarity and bass in the music now, even with Spotify let alone my FLAC music files. So the KEF's are being driven much more strongly in XLR balanced as opposed to RCA SE. The downside is realising just how much variance there is in the production levels of music released and available on streaming services these days. This is most notable when comparing these newly remastered albums to their original album production versions, an annoying trend which became more marketing technique rather than quality improvement with the advent of music streaming services. Volume levelling?

 

[DVDdoug]

I can hear so much more dynamism, detail and clarity and bass in the music now, even with Spotify let alone my FLAC music files.

Sorry, but only one of those words (bass) has any agreed-upon scientific meaning, and something would have to be terribly wrong for there to be a change in the bass.

If something is undefined or unmeasurable it could be verified with a proper, blind, level matched, scientific listening test. What is a blind ABX test?. (And in reality, things can be usually be measured better than we can hear.)

Audiophoolery describes the 4 REAL characteristics of "sound quality", of which only 3 apply to electronics, and usually only one (noise) is a potential issue, unless you are over-driving an amplifier into clipping/distortion.