DuoX noise and screen brightness

Using MOD devices
#1

hi folks!

i know this has been written about in a number of other threads, but there’s one important bit of info which i think needs re-stating on its own:

please run your DuoX with the screen brightness at either 0% or 100% – it is much quieter at those settings than at the three intermediate settings.

note that this is NOT related to any of the discussion about ground loops… hum and buzz related to those problems needs to be controlled with proper configuration of your entire connection and powering ecology, and i won’t begin to address that here.

this is ONLY related to the whine which is primarily at about 1.266kHz.

at those two outer screen brightness settings, that noise virtually disappears. this is a great relief to me, because that is definitely the most noticeable and objectionable Duo and DuoX noise. the lower-frequency pulsating noise is unaffected by screen brightness settings, but i can live with that… it’s just such a relief to be rid of the higher whining noise. :slight_smile:

i don’t yet have my Dwarf, but i’d be interested in any reports about this on that device. i’ll report back once mine arrives…

happy MODing, all… cheers!
.pltk.

later note for clarity: re-reading another thread [ MOD Duo background noise level ], and noting that this particular whine does NOT drop an octave if i switch to 256 frames, it seems that this is actually completely related to screen brightness, rather than the old kernel buffering noise which i originally noticed on my DUO.

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Background noise: steady rhythmic pulse
#2

Thanks for sharing this with the community :slight_smile:

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#3

Are you talking about if i put the brightnes off or at 100% the noise is going to dissapear?

#4

ok, i’ve spent some time documenting this as well as i can! :slight_smile: @Elk_wrath and @jon in particular might find this interesting as well. :wink:

one particular noise disappears… whether or not this is significant for you really depends on the specific noise problem you’re having.

here are some details:

100% screen brightness (0% is the same):

balanced output connection:

balanced_100bright
balanced_100bright3908×1050 403 KB

unbalanced output connection, through DI with ground lifted:

unbalanced_groundlift_100bright
unbalanced_groundlift_100bright3905×1183 420 KB

unbalanced output connection, through DI (ground not lifted):

unbalanced_100bright
unbalanced_100bright3905×1183 472 KB

50% screen brightness (25% and 75% are similar, although 50% is the noisiest):

balanced output:

balanced_50bright
balanced_50bright3952×1094 403 KB

unbalanced output, ground lifted:

unbalanced_groundlift_50bright
unbalanced_groundlift_50bright3905×1183 423 KB

unbalanced output, ground not lifted:

unbalanced_50bright
unbalanced_50bright3905×1183 476 KB

these outputs are all with a blank pedalboard - no plugins and no connections from input to output.

important notes:

  • using balanced output connections or lifting ground on an unbalanced connection makes noise a non-issue.

  • these graphs are all with the outputs at 0 dB (maximum), but note that the background self-noise of the MOD devices does not change with output volume adjustments (i’m referring to the device output volume in settings, not any gain changes on a pedalboard). this has an important consequence: we need to maximize our output level in settings as much as possible, to bring signal level above the noise floor as much as possible.

  • IF (and only if) we have not resolved grounding issues (either with a balanced connection or by lifting ground on an unbalanced connection), then intermediate screen brightness settings yields a 6.25kHz tone which is enough louder than other background noise that it is clearly noticeable.

  • that 6.25kHz tone certainly stands out, but all the other background noise makes the signal pretty unusable anyways, if you haven’t resolved ground issues.

…so, in the end my conclusion at this point is that it’s just an interesting curiosity. i suppose there MIGHT be instances in which getting rid of that 6.25kHz tone MIGHT make an improperly grounded DuoX usable, but it’s much better to use a balanced connection, or lift ground with a DI… once you’ve done that, the screen dimming noise becomes unnoticeable. if you look carefully at the balanced and ground-lifted 50% brightness graphs, you can see that there is a small peak at 6.25kHz, but it’s small enough (and the general noise floor is low enough) that it is not an issue.

as a side-note: these graphs are taken with my recording preamp level set where i need it for good levels when i’m running a healthy signal out of the DuoX. so, it’s an illustration of the excellent job MOD has done in terms of self-noise in this device… other than some low-frequency “thumping” between 20 and 40Hz, everything is at -114dB or less, and even that low-frequency
noise doesn’t get above -100dB.

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#5

This is indeed a super nice experience and perfectly documented!
Thanks for that!
I will ping the engineering team to take a look on this.

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#6

btw: this is a DuoX LE… can’t say whether any of these observations would be the same on a DuoX from the later production runs.

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