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Old 07-04-2020, 07:14 PM   #41
eq1
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New issue - I thought it might be worth posting, in case one of you know off the top of your head what this might be.

The replacement audio interface I bought seems to have a problem. The #2 left and right analog inputs, 1/4 inch, have quite a bit of noise. I have insert peak meters on those channels and I can see them simmering 'a few bars-worth' of noise. I can hear it, too, if I turn the volume up. The # 1 inputs have no noise.

And, when I tap on the audio interface case around those rear 1/4 inch jacks, the right channel peak meter goes 'boop, boop, boop' along with the tapping, i.e. the meter jumps every time I tap on the case (it doesn't actually make a 'boop, boop, boop', noise)...

With my limited knowledge of these sorts of electronics, all that comes to mind is bad solder joints or something like that.

Could it be that, or maybe there's pretty generic types of design for analog inputs on audio interfaces - and there's a component that typically goes bad and can create noise?? It's just a fuzzy noise -white noise? Pink noise? That fuzzy noise noise...

Here's an image showing the noise on the meters, at 'rest' and with me tapping on the case:


edit:
hmm, I just noticed something: If I insert a plug into the left jack, the noise in the right channel goes away - and if I insert a plug into the right jack, noise on the left one goes away... So maybe this isn't as bad as it could have been. Is this normal, typical? Wonder why I don't see this on the #1 channels?...
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Last edited by eq1; 07-04-2020 at 07:30 PM.
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Old 07-04-2020, 09:47 PM   #42
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I vaguely recall that there are inputs enabled which are noisier, and paired with other inputs, that you can disable. Phono inputs possibly?

It's been years since I used one of those, but I remember hearing noise at first until I checked all the inputs/outputs and disabled/muted the things I wasn't using.
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Old 07-04-2020, 10:25 PM   #43
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What happens if you just put dummy jacks in those inputs?, does it solve the problem?
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Old 07-05-2020, 04:37 AM   #44
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I do not know the unit specifically but jack insertion selecting a different input with different gain rings a bell as other posters have mentioned.

However what you describe in terms of noise seem like either microphony (unlikely given it is 'white noise' ish in character as microphony is like the description like the vibration of components) and I would think your other idea of a bad joint or a dry solder joint is more likely.

If you are testing for or locating noise though you really ought to have the input terminated correctly. For most mic inputs a 200ohms resistor is 'standard' (unless a very high or low mic impedance is the designed for source) and for those inputs designed for higher impedance sources (like DI boxes etc) an appropriately higher value resistor should be used. All between hot and cold terminals (balanced) or hot and ground (unbalanced) inputs. That then test the device correctly in it's designed operating mode.

If you do that and still have your noise (you probably will have!) greater than the expected s/n ratio, then you have a fault.
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Old 07-05-2020, 03:10 PM   #45
eq1
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Quote:
Originally Posted by JamesPeters View Post
I vaguely recall that there are inputs enabled which are noisier, and paired with other inputs, that you can disable. Phono inputs possibly? It's been years since I used one of those, but I remember hearing noise at first until I checked all the inputs/outputs and disabled/muted the things I wasn't using.
That could very well be the case. It does have phono jacks. Truth is I rarely use beyond 1 pair of left/right inputs, rarer still that I use 2 pairs. And I usually only have channel strips for channels I'm actively using.

But, I never noticed the noise on my older unit, and I don't see it on the channel 1. And the behavior when tapping seemed odd, like 'that shouldn't be happening if all's copacetic'...


Quote:
Originally Posted by jiff 41 View Post
What happens if you just put dummy jacks in those inputs?, does it solve the problem?
That's exactly what I did at the end of my previous post. I just inserted plugs, no cable, into the jacks. So I'd say, yes, the problem goes away - the noise disappears. So if I'm actually using the inputs then it appears there IS no problem...

The only issue, now, would appear to be this: If I unwittingly had those channels active in the software mixer, and they weren't muted or if they were sent in some way to the DAW, then the noise would get into the mix. Otherwise, I just need to make sure I deactivate them and/or make sure they're not routed to the DAW.


Quote:
Originally Posted by Allybye View Post
...However what you describe in terms of noise seems like either microphony (unlikely given it is 'white noise' ish in character as microphony is like the description like the vibration of components) and I would think your other idea of a bad joint or a dry solder joint is more likely.
I might open it up and check the joints. I don't think those inputs are connected in any way to the mic inputs. Those are at the front of the device, seem quite separate, with their own pre-amps, phantom power, and what-not...

Anyway... Thanks, all, once again for your advice. I really appreciate it.
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Old 07-05-2020, 04:09 PM   #46
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Quote:
Originally Posted by JamesPeters View Post
I vaguely recall that there are inputs enabled which are noisier, and paired with other inputs, that you can disable. Phono inputs possibly?
I feel so 'Duh', now: This is exactly what the 'problem' is. The number 2 inputs on this device are connected to phono inputs (RCA jacks right next to the 1/4 inch). I thought the RCAs/phono were on a third pair of inputs - but there is no third pair! Hey, it's all on the back of the device, I almost never see it...

I opened-up the manual, and right there in the margin it has this warning:

"It’s a good idea to mute MicroDock inputs 2 in the PatchMix DSP mixer when
nothing is plugged in, since the turntable preamp has a very high gain (60dB) and could contribute extra noise to your mix/monitor bus."

Well, glad that's solved.

edit: Just for completeness-sake, here's an image of the front and back of the 'Microdock', clipped from manual:



And to be even more thorough, here's something from the manual that adresses what jiff 41 asked:

Quote:
Originally Posted by jiff 41 View Post
What happens if you just put dummy jacks in those inputs?, does it solve the problem?
Manual:
"RIAA equalized turntable preamp input allows you to connect a turntable
without using an expensive external preamp. Note: These inputs are
automatically disconnected when plugs are inserted into inputs 2L & 2R."
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File Type: jpg E-MU_1616m_Doc_IO.jpg (56.3 KB, 30 views)

Last edited by eq1; 07-05-2020 at 04:27 PM.
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Old 07-05-2020, 04:25 PM   #47
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Glad to help! It had annoyed me too. The noise floor was very low especially at the time it was released. But the first day or so, I kept wondering what that noise was about. Stupid phono preamp lol. It's easy enough to mute those inputs, and from what I recall if you connect cables to the 1/4" jacks it uses the switching on the jacks themselves to mute the phono preamp for the RCA jacks.
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Old 07-05-2020, 04:31 PM   #48
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Quote:
Originally Posted by JamesPeters View Post
...and from what I recall if you connect cables to the 1/4" jacks it uses the switching on the jacks themselves to mute the phono preamp for the RCA jacks.
You have a good memory - see my last edit in my previous post!
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Old 07-05-2020, 11:06 PM   #49
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I opened up the full input preset yesterday to try it out (I normally only open the inputs I'm using) & the noise is there with mine as well! muting or plugging a dummy in gets rid but so does getting rid of unused channels which is what I normally do as I don't even have a turntable anymore which made me feel quite sad when I realised it? as I still got all my vinyl?
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