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Zoom PS-02, PS-04, MRS, H4, HD16cd, R16 and home recording information, discussion, and support

 

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PostPosted: Thu May 31, 2012 3:39 am 
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Hi there,

I have my Zoom R24 a few days now and was pretty impressed until I tried the USB audio interface function (with Cubase LE5 and a Acer Aspire TimeLine-X Notebook). As soon as I press the execute button to go into Audio Interface mode I have quite an amount of noise on the headphone output of the ZOOM R24.

Means:
Standalone Recorder Mode: silence
Audio Interface Mode: Noise (USB, PC with Midi Keyboard still connected)

Does someone have the same behaviour ? Is my HW bad/broken ?
Can the PC be the source of the noise ?
Cables ? USB is digital transmission.
Power supply ? Does not generate noise in stand alone recorder mode .

Appreciate if you can share your experience and also your hints.
Mr. Saxobeat


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PostPosted: Thu May 31, 2012 11:17 am 
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Yoda
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Location: Kentwood, MI
Searching the forum would probably find an identical topic...

1) is the laptop running on wall power? If it is; disconnect the power supply and run on batteries

2) is the Rx running on wall power? If it is; disconnect the power supply and run on batteries

If you need both on batteries, you may have a ground loop problem where both devices are seeing ground at different potential or need to shield the power leads, and keep them away from the signal leads.

If either on batteries is quiet, it may still be a ground loop, but with only one path to ground no loop exists.

If only one power supply is quiet, you may need to filter the other.

If none of the above work, you may need a high grade shielded USB with ferrite chokes to connect the gear. This is recommended in any case. And always keep the power leads away from the signal leads (at worst, don't put them parallel -- crossing at 90deg will minimize coupling)

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PostPosted: Thu May 31, 2012 11:17 am 
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Jedi Zoom Master
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Read this thread:
viewtopic.php?f=17&t=17828

I suggest the HumX by EBTech. I have used it personally and it removes (almost if not completely) the noise you are referring to.

Unfortunately, what you are experiencing is very common and is NOT the fault (not usually anyway) of the Rxx recorders.

Try unplugging the Notebook and see if the noise goes away. If it does, then you can be assured that the issue is indeed the common problem with laptops/notebooks and USB noise.

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PostPosted: Thu May 31, 2012 11:18 am 
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Jedi Zoom Master
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By the way, in my personal experience, I purchased many many ferrite chokes from Rad Shack and absolutely NONE of them worked. Could be just my situation...but there you have it.

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https://www.facebook.com/spasso.music <-- Live Performance


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PostPosted: Mon Jun 04, 2012 3:43 am 
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Thanks for the recommendations.
I have been doing some experiments with the setup and the Zoom R24 only adds just a little bit of noise, there were other sources for hum and noise:
I had a Bass guitar connected to the Hi-Z input and the volumes of all inputs were set at 100 which added some noise too.

My experiments:

1.) Setup: Noting connected to the R24 except power supply and headphones.
Each input obviously adds noise depensing on the volume setting. Starting at about volume 90 you can hear it in the headphones.
This basic noise adds up which every input I add. If I set all gains to 0 there is silence.
This basic noise probably cannot be avoided. What I don't know is wheter the R24 is worse here than other product - I have nothin that I could compare with.

2.) Especially input 1 but also input 2 (because it’s close to input 1 ?) are sensitive to crosstalk/stray pickup (I’m not sure if this is the right term, I’m german).
When I touch the housing in the upper left corner I hear hum in the headphones. This gets very strong when I touch the screws of the XLR connector.
Strehngth of the hum depends on the setting (Hi-Z or normal) and on the gain setting. Similar effect on input 2 bbut not as strong. The other inputs are not sensitive in that respect.
I guess this could be normal for Hi-Z input ? Are these just more sensitive than other inputs ?

3.) I had a bass guitar attached tot he Hi-Z input and this thing is humming (except you turn Gain down to zero).
I guess this is pretty much normal to abass guitar ?

4.) My Midi-Keyboard (Kawai ES6) has a slight humming on the line outputs.
It sounds like some crosstalk of the digital electronics part of the keyboard. I don’t think there is much I can do here :(

5.) When I connect both, the R24 and the Midi Keyboard to USB of my notebook at the same time, this adds some more noise to the keyboard line outs. Seems that this is creating som ground loop.

The power supply of the R24 does not seam tob e aproblem, I don’t here a difference between power supply and battery operation. The notebook was running on battery.

I think that the R24 is not bad or defect, I just have effects that you get when you plug things together with analog signals and usb.
Need to experience some more to find the best setup I guess.
Thanks for your help
MrSaxobeat


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PostPosted: Mon Jun 04, 2012 10:49 am 
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Yoda
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Location: Kentwood, MI
MrSaxobeat wrote:
2.) Especially input 1 but also input 2 (because it’s close to input 1 ?) are sensitive to crosstalk/stray pickup (I’m not sure if this is the right term, I’m german).
When I touch the housing in the upper left corner I hear hum in the headphones. This gets very strong when I touch the screws of the XLR connector.
Strehngth of the hum depends on the setting (Hi-Z or normal) and on the gain setting. Similar effect on input 2 bbut not as strong. The other inputs are not sensitive in that respect.
I guess this could be normal for Hi-Z input ? Are these just more sensitive than other inputs ?


Can you run a bare wire from your hand to a cold water pipe (copper) [I'm not going to suggest you try to attach to the ground posts of an electrical outlet -- though if you are talking Germany you probably have those large circular outlets with a ground prong on top and bottom, while the hot leads are recessed) and repeat the test. If the noise is noticeably less you have a grounding problem (namely -- lack of a ground point; The older HD16hd actually has one screw on the back side marked for connecting a ground wire).

High impedance inputs are designed to for maximal signal transfer from low-power sources (a passive pickup is as low-power as you can get -- all the power is developed by a wire [the string] moving in a weak magnetic field along with a fixed coil for transferring to the output jack). High impedance blocks current transfer (which takes power) sensing voltage changes.

power = voltage * current
voltage = current * resistance
=>
power = current*current * resistance

Pretend the pickup generates 1mW, and that the input is 1kOhm (low impedance) and 100kOhm (high impedance)

current^2 = power / resistance

current^2 = 0.001 / 1000
current^2 = 0.001 / 100000

current = sqrt(0.000001) => 0.001A [* 1000 => 1V]
current = sqrt(0.00000001) => 0.0001 [* 100000 => 10V]

Since consumer line level (full left gain) only runs around 0.8V peak, you can see just how weak a passive pick-up really is!



Quote:
3.) I had a bass guitar attached tot he Hi-Z input and this thing is humming (except you turn Gain down to zero).
I guess this is pretty much normal to abass guitar ?


What type of pick-up? Single-Coil or Humbucker? Does the amount of hum change when you fret (or otherwise) touch a string?

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Superscope PSD-300; BOSS BR-600, Zoom HD16cd, Zoom R16, BOSS BR-800, Zoom H2n
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PostPosted: Mon Jun 04, 2012 2:43 pm 
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MrSaxobeat wrote:
3.) I had a bass guitar attached to the Hi-Z input and it hums (unless you turn Gain down to zero). I guess this is pretty much normal for a bass guitar ?

If input 1 is switched to Hi-Z, I've found that more hum is heard.
As someone else said - Some pickups (e.g. HUMbuckers) are designed to reduce hum - depends if your bass has them?
You could switch Hi-Z to low impedance and use a preamp like "ART Tube MP"

MrSaxobeat wrote:
4.) My Midi-Keyboard (Kawai ES6) has a slight humming on the line outputs.
It sounds like some crosstalk of the digital electronics part of the keyboard. I don’t think there is much I can do here :(

You could use a passive transformer isolator box like "ART DTI Hum Eliminator"

all more money I know - but useful devices anyway


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PostPosted: Mon Jun 04, 2012 9:11 pm 
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Location: Darling River, Australia
You can also try holding onto the (ground) outside part of an input/output or headphone plug and see if this reduces the noise, if it does you may need to ground your equipment. the safest way to do this is to drive a copper rod/pipe (longer the better) into the ground and run a wire from this to the ground of the audio gear (the outside part of one of the plugs). You can get better grounding by wetting the area around the rod/pipe.


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PostPosted: Tue Jun 05, 2012 4:04 am 
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electrochrisso wrote:
the safest way to do this is to drive a copper rod/pipe (longer the better) into the ground and run a wire from this to the ground of the audio gear (the outside part of one of the plugs). You can get better grounding by wetting the area around the rod/pipe.


Sorry ElectroChrisso - Only posting because I know the "buried rod" thing could be against regulations.
- You could potentially introduce another ground loop but this time for the mains (for UK/Europe).

http://www.epanorama.net/documents/groundloop/equipment_grounding.html
The unbalanced audio inputs and outputs have their ground side of the connector wire to audio ground, which is typically connected to metal case of the equipment (because the connector are typically mounted on metal case without isolation between case and connector). In those cases the audio ground gets connected to mains input ground if the equipment has a grounded power connector in it. This is the "de facto industry standard" to do the signal wire grounding and you have to live with it.
If the connectors are balanced, then the connector grounds are typically connected to equipment central grounding point which is connected to mains ground (professional audio equipments are typically grounded).


Wouldn't the buried rod introduce another ground? Here's some more info about hum.

http://en.wikipedia.org/wiki/Ground_loop_(electricity)

http://www.audioholics.com/tweaks/connecting-your-system/ground-loops-eliminating-system-hum-and-buzz

http://www.epanorama.net/documents/groundloop/


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PostPosted: Tue Jun 05, 2012 9:37 pm 
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Quote:
Sorry ElectroChrisso - Only posting because I know the "buried rod" thing could be against regulations.
- You could potentially introduce another ground loop but this time for the mains (for UK/Europe).

Thanks for the clarification on that one Curly Wurly, not even sure what the regulations on this is here, not that I have to worry about that because I run my own independent solar power system and an inverter which can be grounded, as I explained previously, which totally eliminates the noise, even from the switching noise the inverter creates. I only suggested that way because I thought it would be safer than running a separate line from the mains earth.
Perhaps the best thing MrSaxobeat can do is consult an electrician and see the best way on that one, but I am pretty sure earthing should pretty much eliminate the noise as most appliances these days only have the two pins for active and neutral, so no separate earthing is getting there, except perhaps through the neutral.
I use to plug one of my old keyboards which had separate earth connection into the audio chain, to eliminate hum noise when I was on mains power in the past, that might be another way to go.


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PostPosted: Wed Jun 13, 2012 4:33 am 
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Hi Folks,

thanks to everyone for the valuable comments, recommendations and hints.
Now I have a couple of ideas that I can try :-)

Great Forum with great people !

Thank you
MrSaxobeat


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