Huge volume difference ('invisible' clipping) between Outputs 1/2 and 3/4 - is it a fault?

Quad Cortex
1

I nearly always plug my QC in to my FR cab, or monitors, using Output 3/4 (TS cable) - mainly because I have loads of TS cables.

Recently I noticed that when I plugged in to my Hadrush FR Go speakers, via Output 3/4 in to the Headrush 1/4" inputs, it sounded awful - there was lots of unwanted distortion, and what I would describe as a sort of crackling sound, almost as if the sound was clipping horribly. But there is no visible clipping on any of the levels I can see anywhere on the QC (for example via the output block on the Grid, or on the I/O page). This happened both on high gain and even fairly clean presets.

I immediately assumed it was the Headrush FR Goā€™s, because letā€™s face it theyā€™re pretty cheap. But Iā€™d never noticed this before. So as an experiment I then plugged the QC in to my Yamaha HS3ā€™s, via Output 3/4, and to my surprised, sane problem. This seemed especially odd, as I have never noticed this before with the Yamahas.

It then occurred to me to try both sets of speakers connected via the QC Outputs 1 and 2 (XLR outputs).
immediately this sounded much much better - or in other words exactly how you expect the QC to sound.

The reallt weird thing, however, which was instantly noticeable was the huge volume difference between Outputs 1/2 and 3/4.
I have definitely never noticed this before, but the difference is extreme - see video attached - and thinking about it, it explains why the sound from 3/4 is so bad, as the volume must be clipping horribly, even though it doesnā€™t show on any of the level gauges.

As you can see in the video, both outputs are set to 0db, and I canā€™t think of anything else that would explain why one set of outputs is so much louder that it is distorting/clipping.

Has anyone else had this same problem, or can anyone suggest what I might be doing wrong (for example is there a menu setting Iā€™m overlooking?)

Failing that, Iā€™m starting to wonder of my QC has caught a nasty bugā€¦

2

3 and 4 have a +6dB boost from the balanced outputs when using TRS cables

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3

Hmm, I thought I could attach a vid, but seems I canā€™tā€¦:face_with_monocle:

4

Thatā€™s interesting, I didnā€™t know that (has this always been the way? Iā€™ve never noticed this issue before - and weirdly some speakers do play nicely with Outputs 3/4 with no problem whatsoever)

To clarify, are you saying that if I have connect TRS cables to 1/2 then 1/2 are 6dB LESS than 3/4?

Because Iā€™m not actually using TRS cables in 1/2, Iā€™m actually using microphone cables, so XLR male at one end and 1/4" mono at the other end;

And in fact, when I was experimenting earlier today, I was using male XLR to RCA adaptors and RCA to 1/4" mono cables in to the Headrush, as they were the nearest cables to hand.

5

Is this written in the manual, and can you please explain why this is the case? Is this a standard sort of thing with modellers?
Thank you

6

Yes. Hereā€™s a screenshot.
Not sure why, thatā€™s just how it works with balanced connections

Screenshot_20250127_191649_Microsoft 365 (Office)
Screenshot_20250127_191649_Microsoft 365 (Office)1080Ɨ592 65.6 KB

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Ah, Iā€™ve never noticed that, thank you.

So thatā€™s pretty standard on devices with both XLR and 1/4ā€ outputs?

Isnā€™t that saying though that there should only be a volume difference if Iā€™m using TRS cables in Output 3 and 4? Because in my case Iā€™m using TS cables, which if I read that correctly means there shouldnā€™t be a difference?

And if there is a difference, wouldnā€™t that mean that for a given output on any of the QC outputs, the volume should be the same (so 0dB from 1/2 is the same as 0dB from the 3/4) as itā€™s only the MAXIMUM output that is different?

Oh, and does that mean you can use a stereo cable in EACH of Output 3/4? If so I never knew that either! :thinking:

8

Hi again - Iā€™ve just re-read the screen shot and I noticed that the they refer to Max Input Gain for the XLR outputs, and Max Output Level for the TRS outputs.

These sound like different things to me, but does it equate to the same thing?

9

I donā€™t have the QC yet and havenā€™t used FRFR speakers, however, you cannot always use TS instead of TRS. If the devices are designed to only carry a balanced signal, using a TS cable can sound bad.
Does your speaker also accept unbalanced signals?

10

Thanks for that reply - please understand that I have ONLY ever used TS (unbalanced) cables with the QC since Iā€™ve owned it (2 years) both live and at home and in all that time Iā€™ve never had a problem. For example I use it with TS cables from output 3/4 in to my Fender FR10, and in to PA speakers and it has always been fine.

The only thing that made me start looking in to this further is when I bought the Headrush FRFR Go speakers. As I said, at first I thought it was a problem with the speakers, but tried the QC with my Yamaha HS3ā€™s and they have the same issue - even though in the past this has not been the case.

Hence why I wonder if this is some sort of glitch with my QC; it certainly wouldnā€™t be the first volume related glitch the QC has suffered from (not too long ago, I had a problem where my QC would make no sound at all when I turned it on, and the only solution was to restart it sometimes up to 6 or seven times, a problem shared by others on this forum)

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So is it fine if you turn down the output? Maybe you are hitting the inputs of the speakers too hot.

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Yes, itā€™s fine if I turn down the QC master volume to about 75, so that does imply itā€™s hitting the speakers too hot.
But thatā€™s not how the QC is meant to be used of course, itā€™s meant to be unity at 100.

And also it works fine at 100 coming out of the XLR outputs.:face_with_monocle:

13

if youā€™re not using TRS cables, then Iā€™d contact Support ASAP, if you havenā€™t already.
Supposedly that 6dB boost only occurs w/ Tip-Ring-Sleeve cables bcz youā€™re essentially doubling the summed signal.

Youā€™re sure the swipe-down I/O menu shows Output levels at 0 for 3/4?

(the ā€œmax input gainā€ discrepancy in the manual seems to be a typo, of which there are quite a few)

14

Ah, thanks for explaining the typo, that would make sense rather than it deliberately saying ā€˜max input gainā€™.

Yes, the output 3/4 levels are definitely at 0 on the I/O page - I did show that in the video, but I didnā€™t realise I canā€™t actually add videos here :smirk:.

Iā€™ve contacted support too, and managed to send the vid to them, so Iā€™ll report back.

Can I just check something with you though; the way I read the manual is that if I use TRS cables from Output 3/4, it increases the maximum output level available to +15.5dBu.
Are you saying though that it boosts the current volume - so it basically increases the volume just by plugging in a TRS cable instead of a TS cable?
Because that is a good description of what is actually happening on my QCā€¦

15

it will essentially double your output volume- irrespective of the level meters.
Whatever level youā€™re set to, changing from TS to TRS (provided the other device has balanced inputs too) will DOUBLE your output. Not just the maximum achievable (thatā€™s just how they word those spec details)- your signal is essentially boosted by that amount no matter your settings on the QC

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16

Well firstly, every day is a school day! Iā€™ve just learned that a 6dB increase is double the volume, so thank you for teaching me that :+1:t2:.

It certainly sounds like the volume is being doubled, with the expected clipping so would you agree the problem here appears to be that the volume is being doubled when it shouldnā€™t be - ie, it is doubled when Iā€™m using TS cables, rather than when Iā€™m using TRS cables?

And a basic question, if youā€™re using TRS cables, are you supposed to simply turn down the output levels by 6dB?

17

Iā€™m not sure if my QC is exhibiting some of the same issues your having but it certainly is similar. Iā€™ve had my QC for close to two years now and have also had no problems both at home or on the road. It has been a few months though since I gigged with it. I just recently set it up the way Iā€™ve used it gigging and noticed I just couldnā€™t get anywhere near the same volume from outputs 3 & 4 that I get from 1 & 2 no matter whether I use TR of TRS cables. Unlike your setup though, I send the QC outputs into a mixer then to my powered speakers. No matter how high I set the levels on my mixer or speakers, I canā€™t get sufficient volume out of outputs 3 & 4. The kicker is that if I go direct to my speakers, I donā€™t have any problem.
Iā€™ve been in contact with support multiple times and have sent videos but since it works going direct into the speakers, they say it canā€™t be a QC problem. That actually makes sense to me but here I am with a problem I never had before and have tried everything I can think of to rectify it to no avail.

18

Oh man, I feel your pain.

Iā€™ve emailed support and got this reply back;

ā€™ Thanks for reaching out.

The difference in volume between XLR and TRS outputs is properly indicated in the PDF Manual. We recommend you use balanced TRS cables instead to avoid noise issues.ā€™

Which is basically no help at all, because a) it doesnā€™t answer the questions I posed to them in the first place, and b) the manual, as weā€™ve established in this thread already, is inaccurate and contains many typos :smirk:

19

Well, just to add my cents. I have the same issue here. When i use a TS cable in Out 4 connected to Headrush GO, i get for example 85 Dbs. When i use the XLR/P10 cable, itĀ“s a huge drop in DBs, i get 75 dbs (measuring with a external tool).

Reading the answers, seems to be a expected behavior. ĀÆ_(惄)_/ĀÆ

Plus, my OUT 3 works only with TRS cable (with a TS i got no sound, zero), and OUT 4 works ok with TR or a TRS cable.

20

Iā€™ve had this happen too, they give the ā€˜by-the-bookā€™ answer first, which doesnā€™t exactly fit the question asked.

If you restate the question differently, maybe theyā€™ll give further info.
Iā€™ve had to repeat questions several times (usually reworded differently) to try to get a clearer explanation in the past.

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