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Author Topic: powering tube mics in the field?  (Read 17350 times)

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Offline Jhurlbs81

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Re: powering tube mics in the field?
« Reply #30 on: September 01, 2009, 08:28:51 AM »
Just out of curiosity, if one were to go with a bank of batteries to make this happen, what would you guys suggest?


Online H₂O

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Re: powering tube mics in the field?
« Reply #31 on: September 01, 2009, 11:06:39 AM »
I know of 4 portable tube power supplies that where made for tapers in the last 15 years or so:
 2 by Mike Grace
 2 by ??? maybe Bill Bradley

Both sets where for AC701 tube mics and ran 120v and 4v DC.

2 by Mike Grace used DC-DC converters (one for a sm69 and one for a pair of KM56's (I now have this one))
2 by ??? used Banks of Alkaline Batteries (one for a pair of KM254's and don't know the other)

For batteries, There are probably a few ways you could do this as the 120V current will be very low - you could use 10 small 12V SLA's and then recharge as needed (i.e. similar to the ones in the m148).
May be something like 10 of these:
http://www.advancedbattery.com/itemdesc~product~abs+12v0.8t5lt+-+12v+0.8ah+sla+battery~ic~12v0.8t5lt~eq~~tp~.htm

Suppling the 6.5V you need for filement voltage would be fairly easy and you could use a linear voltage regulator off another SLA to get the right voltage (if you are concerned about noise).
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Online H₂O

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Re: powering tube mics in the field?
« Reply #32 on: September 01, 2009, 12:32:42 PM »
Another option would be to have Battery Space build a custom ~120V pack.

http://www.batteryspace.com/index.asp?PageAction=VIEWCATS&Category=894

I would see if you can find out the high voltage range (i.e. The Grace I have output more like 110V under load instead of 120V and I verified with Schoeps that this would be ok before I tried to run a show on it).

The more critical voltage is the filament voltage (i.e. AC701 tube needs to be within 0.2 V of 4 V or you will start to damage the tube and shorten the lifespan) - don't know about the EF732 it seems to be a newer design than the 701 so it may have greater tolorances.

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Offline Walstib62

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Re: powering tube mics in the field?
« Reply #33 on: September 03, 2009, 06:11:15 PM »
So Jesse,

What did you figure out? Anything?

Offline Jhurlbs81

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Re: powering tube mics in the field?
« Reply #34 on: September 04, 2009, 11:07:57 AM »
I'm waiting to hear back from Telefunken on the voltage tolerances..

Offline Jhurlbs81

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Re: powering tube mics in the field?
« Reply #35 on: December 28, 2009, 02:32:01 PM »
I figured I'd update this for those who were interested.

I finally got the PSU schematics.

Input voltages/tolerances
6V, 140mA (250mA peak)
140V, 4.8mA (5.2mA peak)

A TSer has offered to build me a custom box using DC-DC convertors to generate the 120V off a 9+V battery.  The circuit will also provide the 6v heating voltage.





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Re: powering tube mics in the field?
« Reply #36 on: April 27, 2010, 01:07:09 AM »
Maybe this black box can help  >:D
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Offline Jhurlbs81

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Re: powering tube mics in the field?
« Reply #37 on: April 27, 2010, 09:36:48 AM »
There she is!!  ;D

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Re: powering tube mics in the field?
« Reply #38 on: April 27, 2010, 12:04:17 PM »
Wait...Is that a portable tube power supply?#@$  I must have one.  Did you make that?

Offline Jhurlbs81

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Re: powering tube mics in the field?
« Reply #39 on: April 27, 2010, 05:33:51 PM »
H2oDC+  8)

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Re: powering tube mics in the field?
« Reply #40 on: April 28, 2010, 03:02:15 PM »
It's in the mail!


Looking forward to hearing some recordings made your new setup - sounded great in my basement recording the TV!
« Last Edit: April 28, 2010, 03:52:26 PM by H2O »
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Offline Jhurlbs81

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Re: powering tube mics in the field?
« Reply #41 on: May 02, 2010, 11:08:14 AM »
I ran the DC box last night for the first time.  Everything went very smoothly. I ran the Telefunkens stagelip XY for a multitrack recording.  I used a Tekkeon 3450 to power the DC box and my Microtrack 2 off the USB.  After the show (2hr 30min) I still had 5 of the 8 LEDs on the Tekkeon, so battery life will not be a concern.  So far, so good!  :)

Offline tbone65

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Re: powering tube mics in the field?
« Reply #42 on: May 02, 2010, 02:36:30 PM »
telefunken usa will have  a magic box out in  a few moths.specifically being made to power up tube mics. call tony and talk to him .im sure he can be of assistance.

Offline Jhurlbs81

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Re: powering tube mics in the field?
« Reply #43 on: May 04, 2010, 10:39:03 AM »
LOL! This is the magic box.  TS member H20 is the one developing the box for Telefunken USA.
« Last Edit: May 04, 2010, 10:49:09 AM by Jesse Hurlburt »

Offline 108Ω

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Re: powering tube mics in the field?
« Reply #44 on: May 07, 2010, 11:35:34 AM »
My old Atwater-Kent used two batteries, A and B
"A" voltage was for filament and it came from the A-battery; "B" voltage fed the plates and (oddly) came from the B-battery.  (B+)
Sometimes a "C" cell was used to power grids, but usually a rheostat could provide it, tapped off of the B+ line.

Then the power company came along an put up all those dag-burned poles and it all changed.
Lot of good men lost putting up those wires, back in the day, yessiree.
No one even remembers the sacrifices made to bring utilities to these here parts atall.





Be careful with 120 vdc field wiring, it can burn and/or kill.
In fact, high DC voltages are even more dangerous than wall outlets.
« Last Edit: May 07, 2010, 11:44:57 AM by 6o6 »
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