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Author Topic: powering tube mics in the field?  (Read 16723 times)

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Offline Jhurlbs81

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powering tube mics in the field?
« on: August 28, 2009, 08:18:02 AM »
Hey Guys-

I'm trying to help a friend  come up with a rechargeable option for powering his tube mics in the field.  I am curious how the battery pack for the Schoeps/Elvo tube set-up works.  Currently, we are powering Telefunken USA's redesign of the Ela m260s tubes with 4 30v cells.  The batteries are extremely expensive and taping a single show runs at least $40.  I really don't know what my options are for rechargeable cells that might be practical for this application.  Any ideas gents?

Thanks!
Jesse

Offline sunjan

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Re: powering tube mics in the field?
« Reply #1 on: August 28, 2009, 09:17:31 AM »
Three wally world batteries serially connected? 3*9V=27V
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Re: powering tube mics in the field?
« Reply #2 on: August 28, 2009, 09:48:17 AM »
If you need roughly 110v/120v to power this stuff, then I'd look into a DC up converter of some sort. Do they really eat 110v of DC power or does it take that and drop it down in the mic power module? Is it 60v per mic or 120v per mic?
"This is a common practice we have on the bus; debating facts that we could easily find through printed material. It's like, how far is it today? I think it's four hours, and someone else comes in at 11 hours, and well, then we'll... just... talk about it..." - Jeb Puryear

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Offline Teen Wolf Blitzer

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Re: powering tube mics in the field?
« Reply #3 on: August 28, 2009, 11:32:50 AM »
I want this too!!!  So I will follow this thread with interest.   ;D

Offline NOLAfishwater

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Re: powering tube mics in the field?
« Reply #4 on: August 28, 2009, 11:40:05 AM »
I am guess in you will need some kind of DC to AC adapter inline between your battery. Then figure out what voltage you want to run them on. I use a Batteryspace 10-14-100 to power my two Schoeps M222/NT222 DC, which take DC power so I do not need any dc to ac adapter.

I wonder if something like this would work in reverse?
http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=2660
« Last Edit: August 28, 2009, 11:44:45 AM by NOLAfishwater »

Offline H₂O

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Re: powering tube mics in the field?
« Reply #5 on: August 28, 2009, 11:47:17 AM »
I have a Grace Custom Power Supply/Pre amp that was built in 1995 and uses a Apogee DC-DC converter (these are no longer produced) to generate 120V needed for the Capsule voltage - the 4V heating voltage is provided off the 5V bus power through a Zener Diode.   The unit runs off +6V and pulls a max of about 600mA with the PreAmp and Power Supply running for 2 Channels.  This powers my AC701 Schoeps Vintage m221b mics.

I also have a pair of Elvo NT222DCs - These run of 10-16V and pull about 300mA each when running (peak at about 1A a piece when the tube is warming up - according to the manual).

You could look to have a DC-DC converter built that output's 120V and then the heating voltage as well, or you could grab some off the shelf isolated dual output convertors and have them chained together (4 x 15V/-15V DC-DC convertors to get to 120v)

Here is a link to a company that makes high quality DC-DC convertors - and in particualar the line I would look at for your needs:
http://www.recom-international.com/powerline.html

I would definitely look at the DC-DC converter route versus using banks of batteries.
 
« Last Edit: August 28, 2009, 11:53:44 AM by H20 »
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Offline NOLAfishwater

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Re: powering tube mics in the field?
« Reply #6 on: August 28, 2009, 11:47:27 AM »
You need an INVERTER



http://www.i4at.org/lib2/inverter.htm




An Inverter is a device that converts 12 volts d.c to 120 volts a.c. , which is what we use in our homes.  This project will handle about 300 watts, which is perfect for lights, small T.V.'s and radio equipment.

This Inverter takes 12 volt d.c  and steps it up to 120 volt a.c.  The wattage depends on which transistors you use for Q1 and Q2, as well as the "Amp Rating" of the transformer you use for T1. This inverter can be constructed to supply anywhere from 1 to 1000 (1 KW) watts. If Q1, Q2 are 2N3055 NPN Transistors and T1 is a 15 A transformer, then the inverter will supply about 300 watts. Larger transformers and more powerful transistors can be substituted for T1, Q1 and Q2 for more power. Note: Don't try to run inductive loads (motors...) off this inverter.

Parts

.  
C1, C2     68 uf, 25 V Tantalum Capacitor
R1, R2     10 Ohm, 5 Watt Resistor
R3, R4     180 Ohm, 1 Watt Resistor
D1, D2     HEP 154 Silicon Diode
Q1, Q2     2N3055 NPN Transistor (see "Notes")
T1    24V, Center Tapped Transformer  
Misc.    Wire, Case, Receptacle (for output)
    Fuses, Heatsinks, etc.

 


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Re: powering tube mics in the field?
« Reply #7 on: August 28, 2009, 11:49:11 AM »
I am guess in you will need some kind of DC to AC adapter inline between your battery. Then figure out what voltage you want to run them on. I use a Batteryspace 10-14-100 to power my two Schoeps M222/NT222 DC, which take DC power so I do not need any dc to ac adapter.

I wonder if something like this would work in reverse?
http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=2660

You can get them for cars. We used to travel on business and plug them into the the cigarette lighters so we could use our laptops while traveling. We had an older one that was loud (e.g. older computer fan from the 90s type loud), so I don't know if there are quieter ones. Had maybe 3 or 4 AC outlets on the box. Thats the first thing I could think of.
"This is a common practice we have on the bus; debating facts that we could easily find through printed material. It's like, how far is it today? I think it's four hours, and someone else comes in at 11 hours, and well, then we'll... just... talk about it..." - Jeb Puryear

"Nostalgia ain't what it used to be." - Jim Williams

Offline NOLAfishwater

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Re: powering tube mics in the field?
« Reply #8 on: August 28, 2009, 11:49:32 AM »
Here are more schematics for 12DC to 120VAC  INVERTERS

http://www.discovercircuits.com/C/co-dctoac.htm

Offline H₂O

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Re: powering tube mics in the field?
« Reply #9 on: August 28, 2009, 11:52:33 AM »
Tubes run on DC not AC!   You do not need to covert back into AC to make this work.  An inverter is overkill - unless you want to go out and buy one in the store.
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Re: powering tube mics in the field?
« Reply #10 on: August 28, 2009, 11:54:20 AM »
Tubes run on DC not AC!   You do not need to covert back into AC to make this work.  An inverter is overkill - unless you want to go out and buy one in the store.

Bingo. If Jesse can find someone to build him a DC-DC converter, thats optimum, but if he can't find someone to build one, then your down to the DC-AC-DC conversion, or continuing your exercise program...
"This is a common practice we have on the bus; debating facts that we could easily find through printed material. It's like, how far is it today? I think it's four hours, and someone else comes in at 11 hours, and well, then we'll... just... talk about it..." - Jeb Puryear

"Nostalgia ain't what it used to be." - Jim Williams

Offline H₂O

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Re: powering tube mics in the field?
« Reply #11 on: August 28, 2009, 12:22:51 PM »
Here is an original schematic for the m260 - looks like in this version a different tube is used (AC701).

The newer version uses a Telefunken EF-732  (there may have been many versions with different Tubes of the original - i.e. the m 251's)

Jesse - Can you provide the input voltages and required current?  Looks like Pin's 2 and 4 from the Schematic - Pin 2 = Heating and Pin 4 = Capsule - pretty simple deaign.

More info on the EF732:
http://recforums.prosoundweb.com/index.php/t/19774/0/
http://www.radiomuseum.org/tubes/tube_ef732.html

Looks like filament/heating is 6.5V at 150mA (i.e. Pin2)


« Last Edit: August 28, 2009, 12:48:43 PM by H20 »
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Offline Jhurlbs81

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Re: powering tube mics in the field?
« Reply #12 on: August 28, 2009, 12:35:22 PM »
Wow! Thanks for all the replies and interest.  I'll share this info with the designers of the original box I've nbeen using and see what other info I can gather.

Thank you guys so much!


Imaginary +Ts all around :)


Offline Walstib62

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Re: powering tube mics in the field?
« Reply #13 on: August 28, 2009, 02:00:31 PM »
Most vacuum tubes use about 6.3 v ac to heat the filament. The cathode in the tube pictured in your schematic employs an indirectly heated cathode, very common to tube circuits. you still need ac to heat the filament, more than likely.
If the power supply unit itself has a 110 ac plug on it, then the easiest way to power it is to get a 12v battery and connect a store bought ac invertor to it, then simply plug in your power supply.
There is some power loss within the invertor ckt. whenever it is turned on, even if whatever is plugged into it is off because it will be generating ac all the time.

Offline Walstib62

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Re: powering tube mics in the field?
« Reply #14 on: August 28, 2009, 02:21:09 PM »
actually, the filament could be ac or dc. If you had a shematic of the power supply unit, it would be very helpful.

 

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