That is a good point had forgotten the 4dbu differance, just have a x1 (1Meg) probe between 2&3 on xlr. and on the phone side same again 1x probe but between ground and hot.
Really appreciate you doing that! Thanks! So it does appear there is a difference?
Hi all, I was a bit concerned about these reported sound issues. Being a bit biased I did a gig on my new P4 and also thought that RCA Output would sound “better”. So when in doubt - wipe it out: Yesterday I spent some time measureing a bit.
I did a typical “NULL” Test. For some of you maybe not being familiar with Sound/Electrical Engineering: A Nulltest follows the equation: (1) + (-1) = NULL This means:
- switch Prime_4 to mono
- play some Pink Noise on Channel A
- use Out_L and Out_R and feed them to an external Mixer (here Soundcraft UI12)
- “Phase reverse 180 degrees” of Out_R on external Mixer;
- adopt gain to be 100% same for L and R; no EQs, no FX or dynamics on external Mixer
- Open Faders on the external Mixer
- Theoretically there will be a fader-level where both channels wipe out each other–> 1+(-1)=0; You hear nothing in the Master but some hiss. Then both channels under test are 100% the same.
- If you hear somehthing on Master then you know: Both channels under test differ. You can hear what is different but you cannot determine which channel is different. Fun fact:Try this with P4 outputs switched to Stereo …Understood?
Here the results:
- Reference Test: Comparing RCA L/R: Both are identical; Gain is properly adjusted on my P4 (i.e. L&R the same)
- Reference Test: Comparing XLR Out L/R: Both are identical; Gain is properly adjusted on my P4 (i.e. L&R the same)
- Comparing XLR R with RCA R: You hear a little Bass artefact in the range 20Hz-150Hz, so either XLR or RCA brings out more Bass ( I assume XLR Out, me knowing the typical XLR circuitry, however I wasn’t able to measure the difference even after heavy filtering of the single channel) . I’ll follow up on that one.
But the most important thing: RCA OUT and XLR OUT are per se phase reversed!!! So if you use XLR and RCA both at the same time for whatever reason: Remember this!
Finally I wanted to quick test the THD of each output using my FFT-Analysator but were not able to finish these tests. Sneak preview: I wasn’t able to measure any unwanted THD neither on XLR nor RCA. But I will follow up on this.
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Most XLR balanced outputs have imperfect phase matching of the extreme lows and/or extreme highs between the + and - components, meaning that the differential amplifier on the input end isn’t going to produce exactly the same source signal (ignoring the levels difference) to the RCA unbalanced connection on the frequency extremes. Usually the one universal aspect of improved measurable fidelity in the XLR over RCA connections is in Total Dynamic Range due to the (usually) higher output, but this only makes any practical difference if there’s a massive amount of RF interference and/or the source signal is able to take advantage of such an increased TDR, and then there’s lots of other factors that will prevent you from really hearing that particular difference, anyway. Balanced is a ‘utility’ connection meant for very long runs and/or around very high interference. Balanced (other than when used for push-pull amplifying of drivers, like some reference headphones) is not intended as an audiophile connection.
THD tests on Prime’s playback software is mostly a waste of time, as THD is easy to get good values with digital signal processing even if other stuff is fouled up. You’d need to drill down to real-time spectrum analysis of a tone sweep to see the harmonics generated, test for frequency response, and also look at various forms of IMD to get much useful information on the cause of DSP sound quality degradation.
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I just purchased a Prime 4. The RCA outputs produce a much better sound with my PA speakers than do the XLR outputs. It’s not a problem for small venues but could be problem for bigger ones.
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Seems there are quite a few people finding this xlr issue is better with the RCA outputs.
An update: I switched to a different xlr adapter and that solved the problem. My PA system needs an unbalanced connection and the balanced adapter was cancelling out part of the signal. So I run balanced xlr cable from the Prime 4 for distance to avoid feedback, but then use a short unbalanced adapter to connect to each PA speaker. I’m now getting great sound.
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Thanks for the update. Do you have a link to the adaptor you are using?
I just ordered these. Are these what you are using? TISINO XLR to Jack Mono Adapter, Unbalanced Female XLR to Quarter Inch 6.35mm TS Male Adapters - 2 Pack
Yes, that’s the type of adapter I used. Hope it works for you.