Active Electronics
bas...@yahoo.com
require the use of my killfile(I hope) because it has really gotten a
workout lately. I don't remember this being dicsussed here, so I'll
ask if any one has used the x-bat
(www.precisionmusictech.com/xbat.htm), which is an external battery
system for active electronics. My cousin is playing a Peavey
Millenium AC BXP 5 string with 18 volt electronics and is using up a
pair of batteries in 6 to 8 hours. The x-bat places 2 nine volt
batteries in an external case with a mono cord out and a stereo jack
in, so that you use a stereo cable to your bass to send power to and
signal from the bass. A nine volt model is also available. The next
question is, would a unit similar to this using an 18 volt power
supply (hospital rated) instead of the batteries work without picking
up interference? I am playing a Curbow Petite International, and I
change the battery aout every 20 hours just in case and I would not
give up my wireless anyway, but he is worried about losing power
during a church service. He is also just a little bit cheap and two
batteries a week does add up!!
js
though.
What's the price on it?
<bas...@yahoo.com> wrote in message
news:st2fs35e1p7vogc3v...@4ax.com...
bas...@yahoo.com
supply without interference or hum? On Fri, 29 Feb 2008 00:07:50
Benj
> $69.95, but the question is can one be built with an 18 volt power
> supply without interference or hum?
I've been considering building something like this only powering the
bass through a stereo cable using the power from inside my amp(s).
Here's the deal in a nutshell. In active basses (and some other
things) you have a stereo jack. The "tip" of the jack is the signal
output from the bass. The "ring" contact of the jack which is
designed to contact the second wire in a stereo cable, instead
contacts the body of the mono cable plug and shorts that terminal to
"ground" which is the shield of the mono cable. Typically the 9v (or
18v) NEGATIVE of the battery goes to that terminal on the bass jack.
So dig. When the bass has no cable plugged in the jack terminal floats
and the battery is disconnected. When you plug in a mono cable it
shorts the "ring" terminal (battery negative) to the body of the plug
(ground) and it thus turns on the battery by putting the negative side
to ground. THAT is how an active bass turns on and off by inserting
the cable.
OK. So what if you insert a STEREO cable? Well the "ring" terminal
that formerly was grounded now goes to the OTHER wire in the cable.
And that cable then goes to whatever. So the bottom line is that the
NEGATIVE of the internal battery goes to that wire. So NOW if you take
an old 9v battery apart and take the terminals off the top and solder
a wire between them you now have made a shorting plug for where the
battery goes. So if you take the battery OUT of the bass and install
the short instead, with a stereo wire you now have the "RING" on the
cable going to the POSITIVE wire of what used to be the battery. In
other words your extra wire in the stereo cable is now a POWER line
direct to the instruments electronics! Hence to power the instrument
remotely all you need to do is connect a 9v or 18v battery at the FAR
end of the stereo cable between ring and ground (body of the jack).
"OK, Mr. Bongo, if you are so smart, then why haven't you done this
yet?" Here come the "problems". One is that if you use a battery for
power, the battery is REALLY isolated from all powerlines and hum and
noise. This is what makes battery power so cool. If you try to use a
"wall wart" there will be some coupling or even ground loops or even
perhaps some line voltage between that power supply and the one in
your amp. Expect HUGE hum and noise! This was why my idea was to
actually use the power in the AMP to provide the "phantom" power to
the bass. That way both amp preamp and the bass active circuits use
the SAME power and it avoids all the problems. A good start. Of
course you may have to 'adjust" the amp power (most likely 12 or 15
volts) if your bass can't take that voltage. Getting 18v may be even
more tricky.
But wait there is more! Notice in the description of that PMT battery
box they talk a lot about short protection and "fault warnings". This
has to do with the fact when you plug a stereo jack into your bass
that is supplying power on the "ring' terminal, that terminal will
SHORT for an instant as you jam the plug into the jack hole! The
power supply MUST, repeat MUST be able to take that short without
damage. This means that if you suck power from the amp, there must be
a "protection circuit" between the amp power supply voltage and the
line to bass. The protection fault circuit just opens up the
connection when there is a short. As you can see this is where things
start to get a bit more complicated!
Of course you COULD just take a vow to ALWAYS have the power off when
plugging and unplugging bass cords... Yeah SURE! How long to you think
it would be until you forget (right before the most important gig of
your life, of course)? Bottom line: I"m still using batteries. But
the general concept is certainly doable and I'd love to set up my amps
this way! Any engineers out there with a nice short protection
circuit...Please dump it in here!
That's the story!
Benj
Derek Tearne
> My cousin is playing a Peavey
> Millenium AC BXP 5 string with 18 volt electronics and is using up a
> pair of batteries in 6 to 8 hours.
You're not kidding I assume?
A pair of batteries in 8 hours?
That's just completely wrong on so many levels.
Replace the active electronics in that bass with something better.
And someone go and punch the designer of that preamp in the face.
If the electronics in a bass really have to use that amount of power,
build in an external power supply.
I've got batteries in preamps in basses that have been in their for
years - and these are basses I use on a regular basis.
A Wal bass, with electronics designed in the early 80's, will go for 3
months with the preamp on *all the time* (I fixed that problem when I
discovered it 3 months and a couple of hours after taking possession of
the bass).
For a battery in any bass to last only 6 - 8 hours is criminal.
That's not even a days work. That's a battery a gig.
And we wonder why there's a looming environmental crisis.
I change the batteries in my Wal basses every year or so *just in case*.
People keep expressing concerns about active basses and short battery
life, but there's really no excuse for this.
--- Derek
--
Derek Tearne - de...@url.co.nz
Many Hands - Trans Cultural Music from Aotearoa/New Zealand
http://www.manyhands.co.nz/
js
for their basses, or at least they used to. It was this super secret thing;
made them nervous to even talk about it (Mr. And Mrs. Alembic ara a little
weird...).
Anyhoo, Would a separate XLR 3 prong arrangement kill the noise?
I'm thinking that you would use a mono input jack, take the + and - battery
cables, run them out to an XLR jack, run a ground from the input jack to the
XLR, then out to your power supply. You might even be able to use a
commercial FX supply unit.
Actually, I'd probably use some other shape of DIN plug, so I don't confuse
it with an input. If you wanted to get fancy schmancy, you could install a
switch to select battery or external supply.
What do you think?
I'm damn sick of dealing with/worrying about batteries.
"Benj" <bja...@iwaynet.net> wrote in message
news:c7504850-d333-4d3c...@x41g2000hsb.googlegroups.com...
Clive
"Derek Tearne" <de...@url.co.nz> wrote in message
news:1id3ds8.4vg9sa4tjxw0N%de...@url.co.nz...
The battery life of a few hours puzzled me too.
Something is wrong.
I change mine once a year even though they test OK.
EMG state life of around 3000 hrs for a single pick up, about
half that if powering an add-on preamp as well which equates
pretty much to a 4 hr gig every night for a year.
18 volts won't give longer life (in EMG installs) but more headroom.
Just my 2p worth!
-C-
bas...@yahoo.com
possibly be paranoia of a bass dying in a service, but that is not the
way he is. On Fri, 29 Feb 2008 12:14:19
Benj
> Alembic makes some sort of proprietary DIN cable plug in power supply box
> for their basses, or at least they used to. It was this super secret thing;
> made them nervous to even talk about it (Mr. And Mrs. Alembic ara a little
> weird...).
More than a little!
> Anyhoo, Would a separate XLR 3 prong arrangement kill the noise?
Depends. The main advantage of an XLR 3 pin is that you don't have
that "short the power supply" problem when inserting the plug. And
XLR 3 pin plug is a bad idea because it's the same as mic connectors.
That could lead to mis-plugging disasters (48v phantom power into your
bass! Yikes!) I'd use XLR 4 pin connectors. Also remember that the
power lead is running all along through the cable right next to the
signal lead. This means that any noise in the power supply will
transfer over to the signal wire. So for the system I'd use special
shielded cable that has TWO separate coax lines in it. That way the
power line is shielded from the signal line. It may take some looking
to find that kind of wire! You could try standard stereo cable wire
and see how it works as a trial.
The down-side of this is that the connectors are large and non-
standard. Wire is non-standard too. (Stereo ring-tip wires are
slightly more standard) DIN plugs are smaller but not especially
robust. I'd go 4 pin XLR.
> I'm thinking that you would use a mono input jack, take the + and - battery
> cables, run them out to an XLR jack, run a ground from the input jack to the
> XLR, then out to your power supply. You might even be able to use a
> commercial FX supply unit.
YOU only need to run battery +, Signal out, and Ground to the XLR
jack. Yes a commercial FX supply is designed to eliminate some of the
noise feed-through I talked about. Always plug the supply into the
SAME AC line as the amp, however! Best would still be to use power
from the same supply in your amp as the amp preamp.
> Actually, I'd probably use some other shape of DIN plug, so I don't confuse
> it with an input. If you wanted to get fancy schmancy, you could install a
> switch to select battery or external supply.
Actually if you do it as I said above, you don't need a switch. If you
plug into the XLR and NOT the phone jack the battery negative is
disconnected and the battery is not used. On the other hand if you
plug in a standard cable and NOT the XLR then battery gets connected
and the XLR power is not used. It switches automatically! The only
problem is if you were to use BOTH the XLR and a standard cable. Then
the XLR would charge the battery and the bass explode! (just kidding
about explode, but the power would try to charge the battery which is
not good) Of course the whole idea with these setups is to NOT have
two wires running to the bass so probably using both is not any real
problem.
> What do you think?
>
> I'm damn sick of dealing with/worrying about batteries.
Me TOO! I'm ready to build!
Benj
(Who really likes the idea of having power from the amp for MY rig but
still being able to use a standard cable and battery for someone
else's amp (like at jams etc.) )
Bevan Weir
crow
Normals are little metal flanges that make contact when a plug in inserted
into a jack. With this type of jack the neg battery lead is connected to the
sleeve normal. The circuit ground is connected to sleeve. When a plug is
inserted (stereo OR mono) the connection is made between the battery &
circuit ground.
2 batteries a week is just wrong. Something is not right. The batteries is
Spector bass 9V circuits are good for 3000 hours. Our 18 V circuits that use
a single battery & a voltage transformer are good for 2500 hours. If your
batteries are going dead in days instead of months, they are most likely
miswired and probably are not able to shut off.
-- jim eppard
if it sounds good...IT IS GOOD!
"Benj" <bja...@iwaynet.net> wrote in message
news:c7504850-d333-4d3c...@x41g2000hsb.googlegroups.com...
Steve
>
> You're not kidding I assume?
>
> A pair of batteries in 8 hours?
>
> That's just completely wrong on so many levels.
>
I have Bartolini 2-band EQ preamps in both of my active basses. I
haven't changed batteries in either bass for at least 2 years. A preamp
that uses up batteries in 8 hours has something wrong. End of story.
--Steve