OK. I have my sights set on some portable mic preamps...
1.)Studio Projects VTB-1 Mic Preamp (wall wart power option)
2.) M-Audio Duo Mic Preamp (USB and wall wart power options)

Most of which are not battery powered, but USB or wall wart powered. So I
ask these questions...

1.)
Is there a battery pack device i can make or purchase that can turn a wall
wart/USB powered preamp into a portable device?
2.)
Is there one that runs power into a USB connector, so i can take advantage
of preamps that use USB for their power source?

I know these are long shots, but it's basically what i need in order to use
the pre's I want to buy.Hopefully this discussion helps others on a similar
quest as I am.

Thanks,

Mike

You can turn any solid battery into a 120 Volt AC power source using the
proper DC to AC power inverter. The issue with powering a wall wat from a
battery is that ......

A) You may require a 10 to 15 pound battery that can provide enough voltage
and amperage to run the inverter long enough to make the electronic device
work for any exended period of time. Where I leve you can buy a 250 Amp
Motormaster Mobile Power Pack battery with a 12volt DC to 120 volt AC
inverter built in for $89 USD, but it is more than half the size and weight
of a car battery. So this solution may not make any real world sense to
power a preamp such as the ones you are looking at.

In terms of the USB option, I could be wrong, but I think that you will need
a hell of a lot of extra laptop batteries to continously run an external mic
preamp (especially the tubes in the Studio Project unit) from a laptop's USB
power supply, and I am not too sure that the USB port is capable of
supplying nearly enough volts and amps to run the thing at all.

If you want clean and small preamps that can work in the field, your choices
are limited. I have nothing against your two choices, but neither is the
right way to go for what you are trying to do, with the possible exception
of using the M Audio Duo as a decent cheap 2 channel A/D converter that
happens to have preamps and phantom powering.

I strongly suggest you consider Mr. Charles Tomaras' offer of a mint used
Sound Devices MP-2. He is a well respected location recordist and I am
certain he will provide a good and well looked after MP2 which will
definately have better electronics and will certainly sound much better than
either the M-Audio Duo or The Studio Projects unit. Besides, the SD stuff
has been field tested by many of us pros and has become our choice for a
damn good reason, they work amazingly well and run off AA batteries for long
periods of time.
RON CHARLES
..
"unibrow" wrote in message
news:PT5Va.165332$H17.59258@sccrnsc02...
OK. I have my sights set on some portable mic preamps...
1.)Studio Projects VTB-1 Mic Preamp (wall wart power option)
2.) M-Audio Duo Mic Preamp (USB and wall wart power options)

Most of which are not battery powered, but USB or wall wart powered. So I
ask these questions...

1.)
Is there a battery pack device i can make or purchase that can turn a wall
wart/USB powered preamp into a portable device?
2.)
Is there one that runs power into a USB connector, so i can take advantage
of preamps that use USB for their power source?

I know these are long shots, but it's basically what i need in order to
use
the pre's I want to buy.Hopefully this discussion helps others on a
similar
quest as I am.

Thanks,

Mike

In article PT5Va.165332$H17.59258@sccrnsc02 writes:

Most of which are not battery powered, but USB or wall wart powered. So I
ask these questions...

1.)
Is there a battery pack device i can make or purchase that can turn a wall
wart/USB powered preamp into a portable device?
2.)
Is there one that runs power into a USB connector, so i can take advantage
of preamps that use USB for their power source?

I've never seen a battery pack with a USB connector on it, but I don't
see any reason why you couldn't build one yourself. The USB connector
has four pins - the center two are serial data, the outer two are DC
voltage. It's 3 volts, I think, or maybe it's 5 volts. Easy enough to
measure or look up on a web page somewhere. The trick is to find the
connector. I haven't seen one on the shelf at Radio Shack yet, but you
can always buy a USB cable, cut off the end that doesn't mate with the
preamp, trace out the power wires, and connect them to your battery
pack. Clearly someone has thought about powering USB devices from
something other than a computer, as I saw a "USB wall wart" in the
latest Cyberguys catalog. I think it was about $12.

However, be sure that the USB-powered preamp that you choose doesn't
require that it be connected to an active computer in order for the
audio circuitry to work. I haven't looked closely at the analog and
digital gozintas and gozoutas of the units that you're looking at, but
in general, a USB mic preamp will have a digital output which only
goes through the USB serial connection, and it may not have an analog
output at all.

If there is indeed an analog output that you could use as a preamp, you
could test all of this out yourself for only the cost of destroying an
inexpensive USB cable and the investment in purchase of the unit or units
long enough to get them connected to your computer through a "test"
cable that provides only power, not data transfer. Once you determine that
you can indeed operate it independent of computer data transfer, the rest
is simple electrically, and only as difficult mechanically as you need in order
to make it neat.




--
I'm really Mike Rivers - )

1.)
Is there a battery pack device i can make or purchase that can turn a wall
wart/USB powered preamp into a portable device?

Yes, but the tricky part is generating 48V phantom power from a lower
voltage DC power supply. Transformers require alternating current to change
voltages, so they require a pulse inverter to generate AC from DC, and the
cheaper ones operate at 1kHz, creating a minor but audible noise. This is
either done inside the preamp, in which case it's almost certain to be a
cheap 1kHz one, or the preamp has an AC power supply. It's best to get one
with an AC power supply and use an outboard battery pack with a ultrasonic
pulse inverter based AC wave generator. Sounds complex, but the M-Audio DUO
is available in portable format with a good power supply from core-sound.com
for something like $435. I'd sooner take the offer on the used Sound
Devices MP-2 though.

2.)
Is there one that runs power into a USB connector, so i can take advantage
of preamps that use USB for their power source?

USB power is DC, so again you're running into a 1kHz power inverter.

Ron Charles" wrote in message ...
I strongly suggest you consider Mr. Charles Tomaras' offer of a mint used
Sound Devices MP-2.

I'll second that. If I had 500 bucks then you wouldn't even have the
opportunity to buy it (and still might not if someone else has snatched it
up already).

If you can find a good wall-wart-powered mic preamp that happens to
take a DC power supply and not an AC power supply, then building a
battery back for it is a simple matter involving a trip to Radio Shack
and perhaps Batteries Plus. I suspect that most decent mic preamps
will require an AC power source though, so this may not be helpful.
I don't know what the devices you're looking at require. Look up their
specs and figure out the power requirements (voltage AC or DC, and
current consumption). The sticking point with mic preamps is
generating 48VDC for phantom power off of a lower DC supply. If you
found one that simply didn't provide phantom power you could always
build your own phantom box that runs on batteries. You can get
higher-voltage batteries at Batteries Plus. The current requirements
for phantom power are very low, so battery life wouldn't be a problem
as long as you disconnect power when you're not using it.


ulysses


In article PT5Va.165332$H17.59258@sccrnsc02, unibrow
wrote:

OK. I have my sights set on some portable mic preamps...
1.)Studio Projects VTB-1 Mic Preamp (wall wart power option)
2.) M-Audio Duo Mic Preamp (USB and wall wart power options)

Most of which are not battery powered, but USB or wall wart powered. So I
ask these questions...

1.)
Is there a battery pack device i can make or purchase that can turn a wall
wart/USB powered preamp into a portable device?
2.)
Is there one that runs power into a USB connector, so i can take advantage
of preamps that use USB for their power source?

I know these are long shots, but it's basically what i need in order to use
the pre's I want to buy.Hopefully this discussion helps others on a similar
quest as I am.

Thanks,

Mike

Check out Sound Devices USBPre. It's a stereo mic pre with line in and
tape in and spdif in and out and 48v phantom powering with a switchable
15db pad. It powers off the computers USB buss.

unibrow wrote:

OK. I have my sights set on some portable mic preamps...
1.)Studio Projects VTB-1 Mic Preamp (wall wart power option)
2.) M-Audio Duo Mic Preamp (USB and wall wart power options)

Most of which are not battery powered, but USB or wall wart powered. So I
ask these questions...

1.)
Is there a battery pack device i can make or purchase that can turn a wall
wart/USB powered preamp into a portable device?
2.)
Is there one that runs power into a USB connector, so i can take advantage
of preamps that use USB for their power source?

I know these are long shots, but it's basically what i need in order to use
the pre's I want to buy.Hopefully this discussion helps others on a similar
quest as I am.

Thanks,

Mike

"Thomas Bishop" wrote in message
...
Ron Charles" wrote in message ...
I strongly suggest you consider Mr. Charles Tomaras' offer of a mint
used
Sound Devices MP-2.

I'll second that. If I had 500 bucks then you wouldn't even have the
opportunity to buy it (and still might not if someone else has snatched it
up already).


It has been officially snatched by me! ;-) Thanks Charlie.

John L Rice

"John L Rice" wrote in message
...

"Thomas Bishop" wrote in message
...
Ron Charles" wrote in message ...
I strongly suggest you consider Mr. Charles Tomaras' offer of a mint
used
Sound Devices MP-2.

I'll second that. If I had 500 bucks then you wouldn't even have the
opportunity to buy it (and still might not if someone else has snatched
it
up already).


It has been officially snatched by me! ;-) Thanks Charlie.

John L Rice


I hope it passed audio when you got it home...I had my fingers crossed when
you handed me the money.

Charlie

"Charles Tomaras" wrote in message
...

"John L Rice" wrote in message
...

"Thomas Bishop" wrote in message
...
Ron Charles" wrote in message ...
I strongly suggest you consider Mr. Charles Tomaras' offer of a mint
used
Sound Devices MP-2.

I'll second that. If I had 500 bucks then you wouldn't even have the
opportunity to buy it (and still might not if someone else has
snatched
it
up already).


It has been officially snatched by me! ;-) Thanks Charlie.

John L Rice


I hope it passed audio when you got it home...I had my fingers crossed
when
you handed me the money.

Charlie


Naw, I'm gonna wait until I get to the gig to try it. That way I'll be
sufficiently 'pleased' when it doesn't work! ;-)

Actually, it seems to work well although if pushed too hard ( mic gains and
headphone gain up too high ) it really flips out. At first I was worried
but I figured it's because of all the voltage trickery going on inside the
thing. Is this normal?

And holy crap you weren't kidding, those LEDs are freaking bright. You could
do sound on the surface of the sun and still see your levels. I wonder if
people have damaged their vision with the bright setting?

Hopefully I'll find the right people and be able to get into the gig with it
so I can try it out.

John L Rice

"John L Rice" wrote in message
...

"Charles Tomaras" wrote in message
...

"John L Rice" wrote in message
...

"Thomas Bishop" wrote in message
...
Ron Charles" wrote in message ...
I strongly suggest you consider Mr. Charles Tomaras' offer of a
mint
used
Sound Devices MP-2.

I'll second that. If I had 500 bucks then you wouldn't even have
the
opportunity to buy it (and still might not if someone else has
snatched
it
up already).


It has been officially snatched by me! ;-) Thanks Charlie.

John L Rice


I hope it passed audio when you got it home...I had my fingers crossed
when
you handed me the money.

Charlie


Naw, I'm gonna wait until I get to the gig to try it. That way I'll be
sufficiently 'pleased' when it doesn't work! ;-)

Actually, it seems to work well although if pushed too hard ( mic gains
and
headphone gain up too high ) it really flips out. At first I was worried
but I figured it's because of all the voltage trickery going on inside the
thing. Is this normal?

Can't really figure out what your are referring to here?



And holy crap you weren't kidding, those LEDs are freaking bright. You
could
do sound on the surface of the sun and still see your levels. I wonder if
people have damaged their vision with the bright setting?

It doubles as a flashlight if you need it.


Hopefully I'll find the right people and be able to get into the gig with
it
so I can try it out.

Just flash the LED's at them then quickly walk by the door while they are
still seeing stars!


John L Rice

"Charles Tomaras" wrote in message
...

"John L Rice" wrote in message
...

Actually, it seems to work well although if pushed too hard ( mic gains
and
headphone gain up too high ) it really flips out. At first I was
worried
but I figured it's because of all the voltage trickery going on inside
the
thing. Is this normal?

John,

I don't know what mic you were using it with but you should read this tech
note and see if this may have been your situation:
http://www.sounddevices.com/tech/mixpre_osc.htm

There are additional tech notes about the MP-2 which may prove useful as
well:
http://www.sounddevices.com/tech/index.html

Charlie


Thanks for the links Charlie. Yup, it's doing the oscillation thing. It
only really happens most of the time when using ridiculous levels or with
fairly high levels and there is a lot of really low frequency content being
picked up by the mics.

I managed to set good levels at the concert even though the low end at the
Fenix seemed to be unbalanced from the balcony where I was recording ( way
too much ). I set the roll off to 160 Hz just to get a reasonable
recording. ( it actually would of been surprisingly good if I hadn't screwed
up by accidentally flipping the DAT's 'auto level' switch to 'on' right
before the band started. Since I was smart enough to bring a small
flashlight but dumb enough to leave it on the front seat of the car I
couldn't see to figure out what was wrong once I noticed the levels didn't
seem right on the DAT meter. I think I'll be able to fix the main level
problems in Wavelab. A few times the low frequency level got so loud, mainly
from the bass drum, that it caused unfortunate distortion though.)

I just went through and tried a few different mics and I could get it to
oscillate with most condensers I tried. Here's a quick list ( best to
worst ) and I'll send it to Sound Devices too since they want to know what
mics have problems :

Any dynamic mic - ( perfect, no problems )
Kustom (EV) SRO-300 ( runs on a battery, no phantom used )
Audio Technica C-87 MkII - ( perfect, I couldn't for an oscillation )

Shure KSM-32 ( these two weren't very bad )
CAD E200

ADK A-51s ( these weren't too good )
MXL 603s
AKG C5900

Audix TR40 ( these are pretty bad )
AKG C1000s


And of course the TR40's were the ones I used.

But I am pleased with the purchase so no worries there. ;-)

John L Rice

unibrow wrote:

Is there a battery pack device i can make or purchase that can turn a wall
wart/USB powered preamp into a portable device?

Yes, we offer a really quiet inverter/battery pack/carry case for our
Portable Duo. Please see our Web site for details.



--
Len Moskowitz PDAudio, Binaural Mics, Cables, DPA, M-Audio
Core Sound http://www.stealthmicrophones.com
Teaneck, New Jersey USA http://www.core-sound.com
Tel: 201-801-0812, FAX: 201-801-0912