H4's 700Hz tone removed - no AC adapter requied

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wqcr
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H4's 700Hz tone removed - no AC adapter requied

Post by wqcr » Tue Sep 29, 2009 12:43 pm

Hi,
I found a way how to remove 700Hz tone on Zoom H4 without AC adapter (adapter removes this tone while recording, but causes AC hum). It is based on external 8 AA battery pack (or 9V battery) with 0,35A fuse. Can I post this solution here?
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oxeneye
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Re: H4's 700Hz tone removed - no AC adapter requied

Post by oxeneye » Tue Sep 29, 2009 5:45 pm

Yes, please do!
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wqcr
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Re: H4's 700Hz tone removed - no AC adapter requied

Post by wqcr » Wed Sep 30, 2009 10:33 am

IMPORTANT NOTICE: NOT FOR USE WITH H4N, IT REQUIRES LOWER VOLTAGE AND HIGHER CURRENT...

Update 14.3.2010 -
I have made some measurements and reveal the tone again. This solution doesn't eliminate the tone or the "heartbeats" fully, however they are greatly attenuated (-30dB). Also I recommend using 7 Rechargeable AA batteries, the unit is very sensitive to input voltage. I discovered another noise varying between 17 - 19kHz. If you use 7 instead of 8, it disappears. The overall current will be greater (87.5mA for 8 AA, 98mA for 7 AA), lifetime will be less (18 hours instead of 22), but the unit will get 9V as it should. However, you must also replace the fuse with greater one. I replaced it with 1A F-type and it works great.
---

To removing this unwanted tone, according to ZOOM support, we should use included AC adapter. Well, but if you use it, another noise appears. It is called AC hum, which is also very difficult to remove. To solve both problems we will create battery pack from 8 pcs. AA rechargeable (!) batteries.

What about the fuse?
Fuse is very important if you want to keep your H4 safe. For this use, I recommend 350mA fuse type F. (According to adapter specification - 9V 300mA ~ 2,7W, 8.8V 350mA ~ 3,08W). But you can use any fuse ranging from 250 to 500mA.

Construction
We will need:
- power jack 2,1mm - commonly used by YAMAHA
- 2-3m 3,5mm power cord (can be shielded)
- 350mA fuse and fuse holder
- battery holder for 8 pcs. AA
- 9V jack if battery holder has its counter-connector
- and of course rechargeable batteries

Image

Construction is up to you, it is nothing hard, just solder up everything and it will work. Don't forget for isolatic tape and DON'T FORGET THE RIGHT POLARITY (+ out, - in). Always check it before connecting to unit.

Lifetime
Standard lifetime in operation manual is 4 hours. With eneloop you can get up to 6 hours recording. With this pack you will have more than 20 hours recording and 22 hours playback, which is enough for almost any recording session.

It is safer
No battery leakage can occur and region voltages (110V - 250V) can't damage the unit.

Low interference
There will be NO AC hum left and notice low average current (80 - 90mA)

Consumption
When powered on two AA, this unit requires approx 0,9W. With this pack it is slightly better, only 0,78W. Why? Because no voltage changer is active. Voltage changers are not 100% effective, they "eat" some of energy.

Do not be influenced with 700Hz tone while monitoring. This tone disappears when you lit display or when you start recording.

Tips for better recording:
- if you cannot use this pack and you must record on batteries, try at least record at 24/96. The tone is supressed, but you cannot "safely" use 4-track mode
- the tone disappears when recording any unbalanced source
- when using external battery pack for a long time and some important recording session is coming and you can't recharge the batteries so quickly, be sure to backup the power with internal ones, the unit will automaticaly turn on internal batts if external are discharged
- first connect your signal sources, then battery pack. After that, turn this unit on
- if you must use non-rechargeable batteries, insert 7 pcs instead of 8 (6 cells Panasonic OXYRIDE or Energizer Ultimate Lithium as they have higher voltage)
- when using H4 as a microphone for external recorder or amplifier that is plug-in powered, use Ground Loop Isolator (it removes any DC-type current)

* - 8,8V is minimal voltage for 8 pcs ENELOOP and some NiMH cells

I also found a solution how to remove pulsing inaudible noise (6Hz), I just call it heartbeats. I simply bought Transcend 8GB Class 6 SDHC card (included in Operation Confirmed cards) and it works.
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Last edited by wqcr on Sun Mar 14, 2010 1:24 pm, edited 4 times in total.
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daveredline
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Re: H4's 700Hz tone removed - no AC adapter requied

Post by daveredline » Sat Feb 06, 2010 5:36 pm

This solution is good for the H2 too?
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billconant
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Re: H4's 700Hz tone removed - no AC adapter requied

Post by billconant » Sat Feb 06, 2010 7:45 pm

Here's another solution that I made from the this post. I have made 2 others for friends H4's. The battery will fit between the H4 and the stand adapter tray.
http://www.2090.org/zoom/bbs/viewtopic.php?t=7838

Bill
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