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Author Topic: 3wire batt bocx for AT943  (Read 13977 times)

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Offline whatboutbob

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Re: 3wire batt bocx for AT943
« Reply #30 on: April 22, 2006, 07:15:21 AM »
Hey folks,

Since running this box I've had an issue with cell phone interference coming through on my recordings..  Any ideas what I can do to shield against this?

Better cable?

Aluminium box?

Unbalanced? (have i got this right?  think i read somewhere that disconnecting the ground on one end makes some difference...I might just be making it up tho).
Mics: Audix m1290's, AT943's (w/ AT853 C/O/H caps), AT853's
Power: PS-2, Homebrew 3wbb, SPSB-6
Pre/AD: UA-5 (BM2p+), CA-9100, AD-20
Recorder: iriver H120, H160

Offline jeromejello

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Re: 3wire batt bocx for AT943
« Reply #31 on: April 22, 2006, 10:40:18 AM »
Hey folks,

Since running this box I've had an issue with cell phone interference coming through on my recordings..  Any ideas what I can do to shield against this?

Better cable?

Aluminium box?

Unbalanced? (have i got this right?  think i read somewhere that disconnecting the ground on one end makes some difference...I might just be making it up tho).

the box would be where i would first start... the more shielding for rf (whether from the unit [selfnoise] or others cellbies) the better.
open: mbho 603a (ka200n/ka500hn) > SD 722
stealth: AT853a (o/sc/c/h) > SD MP-2 > ihp120
misc: Earthworks SR77 | Shure VP88 | PCM-M10

bt & dime

Offline poorlyconditioned

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Re: 3wire batt bocx for AT943
« Reply #32 on: April 22, 2006, 01:25:53 PM »
Hey folks,

Since running this box I've had an issue with cell phone interference coming through on my recordings..  Any ideas what I can do to shield against this?

Better cable?

Aluminium box?

Unbalanced? (have i got this right?  think i read somewhere that disconnecting the ground on one end makes some difference...I might just be making it up tho).

I have never heard any interference (with any mics), so I don't know what this sounds like.

What were you running before?  Do you think the 2-wire would have less interference?  The first thing I would check is the length of the cables.  I don't see how an aluminum case would help (it is all low impedance circuitry), but I guess you could try covering the case in aluminum foil and see.  You can also get alumium "tape", used to fix heating ducts.  Try covering the case in this if it makes a difference

Good luck anyway...

  Richard
Mics: Sennheiser MKE2002 (dummy head), Studio Projects C4, AT825 (unmodded), AT822 franken mic (x2), AT853(hc,c,sc,o), Senn. MKE2, Senn MKE40, Shure MX183/5, CA Cards, homebrew Panasonic and Transsound capsules.
Pre/ADC: Presonus Firepod & Firebox, DMIC20(x2), UA5(poorly-modded, AD8620+AD8512opamps), VX440
Recorders: Edirol R4, R09, IBM X24 laptop, NJB3(x2), HiMD(x2), MD(1).
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Offline whatboutbob

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Re: 3wire batt bocx for AT943
« Reply #33 on: April 22, 2006, 07:26:10 PM »
I have never heard any interference (with any mics), so I don't know what this sounds like.

What were you running before?  Do you think the 2-wire would have less interference?  The first thing I would check is the length of the cables.  I don't see how an aluminum case would help (it is all low impedance circuitry), but I guess you could try covering the case in aluminum foil and see.  You can also get alumium "tape", used to fix heating ducts.  Try covering the case in this if it makes a difference

Good luck anyway...

  Richard


If anyone's curious, this is what it sounds like: http://download.yousendit.com/FDA22FC34AFD2ADB

Its not usually quite this prominent - this sample is from me testing by putting my cell right next to my rig (and calling it).  The strength decreases the further the phone gets from the rig (can't isolate exactly which because cables are too short).  Richard, I don't *think* its cable length because the cable out of the batt box is only ~3 feet (and that's the only cable that has changed).  It might be the type of cable I'm using - its not particularly well shielded because its the only cable I could find to fit into a 3.5mm plug.

Previously I ran AT943(h) > SPSB-6 > H120. I'm now running AT853(c) > AT943 bodies > 3wire bb > H120.

Hehe...I was wondering if wrapping it in alfoil would replicate an aluminium box...I'll give that a shot today.  Do I need to ground the alfoil somehow? If so, how?  (i think i read somewhere that if I don't it'll actually act as a conductor...but I might be making that up).
Mics: Audix m1290's, AT943's (w/ AT853 C/O/H caps), AT853's
Power: PS-2, Homebrew 3wbb, SPSB-6
Pre/AD: UA-5 (BM2p+), CA-9100, AD-20
Recorder: iriver H120, H160

Offline Will_S

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Re: 3wire batt bocx for AT943
« Reply #34 on: April 22, 2006, 09:04:35 PM »
My iRiver iHP-120, for example, provides a 2K2 pull-up resistor to allow the mics to be used without a battery box.

Does this mean that there is no advantage to using a two-wire battery box with the iRiver?  Or just that the iRiver can get adequate levels from mics sans battery box, but SPL handling would still be better with even a two-wire box?

Offline poorlyconditioned

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Re: 3wire batt bocx for AT943
« Reply #35 on: April 22, 2006, 09:35:35 PM »
My iRiver iHP-120, for example, provides a 2K2 pull-up resistor to allow the mics to be used without a battery box.

Does this mean that there is no advantage to using a two-wire battery box with the iRiver?  Or just that the iRiver can get adequate levels from mics sans battery box, but SPL handling would still be better with even a two-wire box?

Like MD, you can use "plug-in-power" without a battery box.  Good for low level recording, but likely to overload for *any* type of amplified music.  Go ahead and try it though.  You might be surpresed.

2-wire battery box uses a higher voltage ((v) so gives you more headroom.  3-wire is the best, though!

  Richard
Mics: Sennheiser MKE2002 (dummy head), Studio Projects C4, AT825 (unmodded), AT822 franken mic (x2), AT853(hc,c,sc,o), Senn. MKE2, Senn MKE40, Shure MX183/5, CA Cards, homebrew Panasonic and Transsound capsules.
Pre/ADC: Presonus Firepod & Firebox, DMIC20(x2), UA5(poorly-modded, AD8620+AD8512opamps), VX440
Recorders: Edirol R4, R09, IBM X24 laptop, NJB3(x2), HiMD(x2), MD(1).
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Offline whatboutbob

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Re: 3wire batt bocx for AT943
« Reply #36 on: April 22, 2006, 10:08:07 PM »
wrapping the box in alfoil amplifies the interference by 3db...  ???
Mics: Audix m1290's, AT943's (w/ AT853 C/O/H caps), AT853's
Power: PS-2, Homebrew 3wbb, SPSB-6
Pre/AD: UA-5 (BM2p+), CA-9100, AD-20
Recorder: iriver H120, H160

Offline poorlyconditioned

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Re: 3wire batt bocx for AT943
« Reply #37 on: April 22, 2006, 10:42:19 PM »
wrapping the box in alfoil amplifies the interference by 3db...  ???

Interesting.

How about putting some aluminum "tape" over it then?  This is available at hardware stores (I think).  It is probably better than (thin) foil.

  Richard
Mics: Sennheiser MKE2002 (dummy head), Studio Projects C4, AT825 (unmodded), AT822 franken mic (x2), AT853(hc,c,sc,o), Senn. MKE2, Senn MKE40, Shure MX183/5, CA Cards, homebrew Panasonic and Transsound capsules.
Pre/ADC: Presonus Firepod & Firebox, DMIC20(x2), UA5(poorly-modded, AD8620+AD8512opamps), VX440
Recorders: Edirol R4, R09, IBM X24 laptop, NJB3(x2), HiMD(x2), MD(1).
** This individual has moved to user "illconditioned" **

Offline whatboutbob

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Re: 3wire batt bocx for AT943
« Reply #38 on: April 22, 2006, 11:48:04 PM »
Would I need to ground the aluminium foil (or tape) somehow?  If so, how?
Mics: Audix m1290's, AT943's (w/ AT853 C/O/H caps), AT853's
Power: PS-2, Homebrew 3wbb, SPSB-6
Pre/AD: UA-5 (BM2p+), CA-9100, AD-20
Recorder: iriver H120, H160

Offline poorlyconditioned

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Re: 3wire batt bocx for AT943
« Reply #39 on: April 22, 2006, 11:53:49 PM »
Would I need to ground the aluminium foil (or tape) somehow?  If so, how?

I don't know.  I would just try it as is.  I guess you could experiment running a wire from ground of the box (eg., shield on the output miniplug) to the metal around the case.

  Richard
Mics: Sennheiser MKE2002 (dummy head), Studio Projects C4, AT825 (unmodded), AT822 franken mic (x2), AT853(hc,c,sc,o), Senn. MKE2, Senn MKE40, Shure MX183/5, CA Cards, homebrew Panasonic and Transsound capsules.
Pre/ADC: Presonus Firepod & Firebox, DMIC20(x2), UA5(poorly-modded, AD8620+AD8512opamps), VX440
Recorders: Edirol R4, R09, IBM X24 laptop, NJB3(x2), HiMD(x2), MD(1).
** This individual has moved to user "illconditioned" **

Offline whatboutbob

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Re: 3wire batt bocx for AT943
« Reply #40 on: April 23, 2006, 01:56:38 AM »
Hrmm...ok...the ground didn't help any, but then I disconnected the ground from the 3.5mm plug and it virtually eliminated the interference.

Any thoughts on why that would've fixed things?

Is there any reason I should reconnect the ground?
Mics: Audix m1290's, AT943's (w/ AT853 C/O/H caps), AT853's
Power: PS-2, Homebrew 3wbb, SPSB-6
Pre/AD: UA-5 (BM2p+), CA-9100, AD-20
Recorder: iriver H120, H160

Offline poorlyconditioned

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Re: 3wire batt bocx for AT943
« Reply #41 on: April 23, 2006, 02:10:59 AM »
Hrmm...ok...the ground didn't help any, but then I disconnected the ground from the 3.5mm plug and it virtually eliminated the interference.

Any thoughts on why that would've fixed things?

Is there any reason I should reconnect the ground?

What do you mean "disconnected the ground from the 3.5mm plug"???  Please explain.

  Richard
Mics: Sennheiser MKE2002 (dummy head), Studio Projects C4, AT825 (unmodded), AT822 franken mic (x2), AT853(hc,c,sc,o), Senn. MKE2, Senn MKE40, Shure MX183/5, CA Cards, homebrew Panasonic and Transsound capsules.
Pre/ADC: Presonus Firepod & Firebox, DMIC20(x2), UA5(poorly-modded, AD8620+AD8512opamps), VX440
Recorders: Edirol R4, R09, IBM X24 laptop, NJB3(x2), HiMD(x2), MD(1).
** This individual has moved to user "illconditioned" **

Offline whatboutbob

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Re: 3wire batt bocx for AT943
« Reply #42 on: April 23, 2006, 03:35:18 AM »
Bah...never mind...it loused up the noise-floor anyways. I simply cut the ground so that it wasn't attached to the 3.5mm plug.  Clearly i have no idea what i'm doing...i'm just playing around.
Mics: Audix m1290's, AT943's (w/ AT853 C/O/H caps), AT853's
Power: PS-2, Homebrew 3wbb, SPSB-6
Pre/AD: UA-5 (BM2p+), CA-9100, AD-20
Recorder: iriver H120, H160

Offline Weazel

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Re: 3wire batt bocx for AT943
« Reply #43 on: April 26, 2006, 07:40:29 AM »
i constucted a pcb with this schematic. and made a pdf file. let me know what you think.
http://www.globalxs.nl/home/w/weazel/3wirebox.pdf
-[ pop goes the weazel ...]-

Offline kuba

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Re: 3wire batt bocx for AT943
« Reply #44 on: May 04, 2006, 12:17:59 PM »
i constucted a pcb with this schematic. and made a pdf file. let me know what you think.
http://www.globalxs.nl/home/w/weazel/3wirebox.pdf

Nice!


Would it be possible to run AT831 with this?? Would it give a "better" sound or just higher SPL handling??
AT831 > bb > iRiver H120

 

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