Zoom Gear & Home Recording Forum

I am getting a very noticable high pitch whine when using phantom power on batteries, when I have the int 1&2 gain set at either medium or high. It is there even with nothing attached. It's probably there at the low gain setting, but it isn't as obvious.

It isn't apparent (or is significantly reduced) when I use the AC adapter. I tried both rechargeables and alkalines, same problem (actually worse with the alkalines).

Up to this point I have been using the internal mics to great success, but I just got a stereo omni mic from sound professionals, and it sounds great, but it blocks the AC adapter port, forcing me to use batteries. Plus, I got this unit for its portability and phantom power...

Any ideas? Has anyone else discovered this, or is my unit possibly defective? It sounds good otherwise.

If there was a difference in the batteries, it could be due to the battery's internal resistance. Alkalines tend to have higher internal resistance than NiMHs. NiCDs have even lower internal resistance than NiMH. So if it worked better with NiMH compared to Alkaline, going to NiCD is worth a test to see if it gets better than the NiMH.

The drawback is that NiCD has lower capacity than NiMH. Worth a test anyway to see if you get better sound. If capacity is the issue, you can always put "fake" batteries into the compartment with wires running out to a "D" cell pack, such as this primitive D to AAA converter I built in about 5 minutes with about $2 worth of parts by drilling out a 3/8" dowell:
http://mclements.net/Mike/BattPack.jpg
It runs my iRiver T30 continuously for over a week straight!

This whine is unacceptable. I have a couple examples. I recorded the sound with no input, just the phantom power turned on at 24 and 48 volts.

How do I post them for review?

You can post them here for free:

http://www.box.net/home

MRC01,

After looking at that photo of your battery mod, I ended up browsing your website and I really liked your photos. You have a terrific daughter, Emma. And I was very touched by your obituary for Thing 2. Hope the dogs stay away!

Thanks for the info. Here is the link for the example noise:

http://www.box.net/public/16q3i6na9p

Great pictures on yrou site, MRC01. I espectially enjoyed your kitchen remodel, since I am workin gon the same project.

Thanks - that kitchen remodel was several years ago from our old house - the "tax deduction with a roof". Quite a fixer-upper that place was!

Wow, that sound is really annoying. I tested my H4 with phantom power, and it has the exact same noise. You don't even have to turn up the volume to hear it. It's quite loud. I tested with no mic attached. Have you tested with a mic attached to see if that makes a difference?

I tested with a mic and there was no whine.

I also tested without the mic but with the (long) mic cable still connected. No whine. As soon as I disconnected the cable, the whine came back.

Let me know if you get similar results.

hi guys, looked at the whiney 24v wav, and it indeed a very
disturbing sound...

it contains the same 689-Hz disturbance as in the other discussion thread.
http://www.2090.org/zoom/bbs/viewtopic.php?t=7221

but it also has a tone around 4190 (and multiples thereof).
to create 24/48v, usually a "charge pump" is used. one integral part
is an oscillator running at a high frequency. should be a lot higher than 4kHz, though...?
http://en.wikipedia.org/wiki/Charge_pump

phantom power requires high voltage, but it is primarily a capacitive load, so the current will be small. when the phantom power is on, and no cable is connected, i suspect that one of the balanced signal cables are connected to ground. this will create a much higher current than in the case of a real microphone load. connecting an XLR cable breaks that and reduces the current = no whining.
the current will have the frequency of the charge pump, in this case we can assume it is responsible for the 4 kHz. so again, if the analog power supply fluctuates periodically, we will see it as a disturbance. probably it travels along the ground circuit and not through the batteries. so maybe the best solution would be to put a nice capacitor on the digital supply part...

in this case, this corraborates the power supply theory, since:
assume Va = V * (1 - c_1*sin(f_1))*(1 - c_2*sin(f_2)) (or something

where c_1 and f_1 correspond to the digital processing power fluctuation.
c_2 and f_2 correspond to the phantom power charge pump power fluctuation.

then we would expect to see disturbance frequencies of (f_2+f_1) and
(f_2-f_1) too, according to simple trigonometry. and they are also clearly visible in a spectrogram.

this as opposed to if the disturbance signals traveled into the analog circuits independently. then (f_2-f_1) and (f_2+f_1) would not be present... i think ...?

/p

Cut that out Pajen, you're giving me a *headache*!

But seriously, I am so happy we have someone who can put some engineering analysis into the mix to verify what many seem to be experiencing empirically.

update:

I contacted zoom and they said my unit must be defective.
Audio-midi.com supplied me with a new unit, and it does NOT have the problem. So far, this unit seems perfect.

I'm glad that it was not an inherent design problem.

Sorry for bringing that on top again but I have two questions - I read a lot aof threads here, but I am not sure if I understand that right - or let's say if that is the same problem as mine:

.) The last post before mine says the 'high pitch wine' is a reason to send the unit back, do I read that right? On the other hand - don't have a lot of guys here that problem? Everyone sent it back?

.) I have that 'high pitch wine' only for the open Input - that means it IN2 'whines' when a mic is connected only to IN1. That is disturbing in stereo mode, in coupled mode everything is ok. So - should I send the unit back or not?

Sorry again if I did not get the problem right

Use four track mode if you only record one input, the whine on the vacant input in stereo mode must be caused because there is no mic to power there.

I guessed that, thanks - seems that is a problem in design. That could easily be solved by a firmware 'coupling option' in stereo mode - maybe Zoom is reading here

I understand that, but when I read this thread again - according to this post

something must be wrong.

Anyone tried to contact zoom and get it replaced? Maybe worm.ouroboros could make this clear?