Why hasn't this been invented yet?

Kabal · #1 06-13-2011, 10:31 AM

Or has it already and I just don't know about it?

An adapter for on-board preamps so we don't have to worry about 9Vs crapping out on us at the worst time?

Maybe because bass players don't want two cables coming out of their bass because it's unsightly or because preamp circuits in pedal format, i.e. sadowsky and aguilar, are becoming more widely made/used/accepted?

Would anyone here buy an adapter for their preamps or would you rather pull out/bypass your onboard electrons (maybe even change your pups in some cases) to throw down a preamp pedal? And not necessarily the aforementioned ones but from any company.

bassteban · #2 06-13-2011, 10:33 AM

I had a bass w/2 output(mag+piezo)- it was a PITA. I'm happy w/a simple bypass so that if/when the battery goes I can finish the song/set before slapping a new 9V in.

ZubenElGenubi · #3 06-13-2011, 10:43 AM

Heck yea, I would buy one. How about a 9V/18V battery pack that clips on the strap and runs a cable into the back of the body?

I should start building something like that now. All my acoustic guitars have on-board pre-amps too and I would love to have them externally-powered.

Another option I would like (and could DIY if I weren't afraid to drill) would be a manual power-off switch so that I can leave the signal cable plugged in the bass without draining the batteries.

Rebop · #4 06-13-2011, 10:47 AM

Power it with Phantom power and it can technically still be one cable (most likely not 1/4" though).

PSPookie · #5 06-13-2011, 10:48 AM

You mean like phantom power? Didn't Alembic do something like that for Phil Lesh back in the day?

Spencer! · #6 06-13-2011, 10:53 AM

Quote:

Originally Posted by Rebop

Power it with Phantom power and it can technically still be one cable (most likely not 1/4" though).

The preamp would have to have a balanced output for that to work.

Overdrive777 · #7 06-13-2011, 10:57 AM

EBS did this many (15?) years ago. But it didn't become a hit. Don't know why. They did it with a stereo 1/4" cable

funkinbottom · #8 06-13-2011, 10:58 AM

Acoustic Image and Euphonic Audio have phantom power. Not sure what other amps, but they do.

SGD Lutherie · #9 06-13-2011, 11:06 AM

It wouldn't be hard to do. You can use a stereo cable, and wire the ring terminal up for power. In bass you would just need to connect the two battery terminals together with another battery clip acting as a jumper. At the other end of the stereo cable would be a break out box that has the power going in and the signal coming out.

The drawback here is you need a stereo cable, so if it breaks during a gig, you either need a spare, or carry a battery with you as a backup.

You can also do it with with an external battery pack and a short stereo cable. From the battery pack would come your regular patch cord. You could put the battery pack on your strap. That would also allow you to use AA batteries, which would last longer.

maybe I ned to start making these?

If can be done with a regular patch chord, but you need some circuitry in the bass that isolates the signal from the voltage, and the same thing at the amp end. This is how phantom power works. It doesn't have to be balanced, it's just that mics already are.

Having said all that, I've been using active basses since 1977 and never had a battery fail on me during a gig. I always brought a spare just in case, as well as an extra set of strings, because I have broken strings on gigs!

**line6man** · #10 06-13-2011, 11:20 AM

Quote:

Originally Posted by Spencer!

The preamp would have to have a balanced output for that to work.

Why do you say that?

All you need is a positive DC voltage at the output. There is no need for a balanced signal unless you also needed a negative DC voltage below ground potential.

FunkMetalBass · #11 06-13-2011, 11:20 AM

People keep asking about these lately - probably 20 threads in the past few months.

Phantom power would be nice, but you'll need an additional unit to run it, unless you want to modify your amp to produce 9V phantom power. This also ruins all hopes of using a wireless system.

An external unit could work, (]9 Volt External Battery System for Active Electronics), or you could even build something smaller that houses one or two batteries and clips onto your belt, but you're still at the mercy of a stereo cable.

The quick-change battery portion on a bass is really the most sensible choice for 90% of uses, in my opinion. It's small, doesn't take up much room, built into the bass, and still allows you to switch out batteries in under a minute.

staindbass · #12 06-13-2011, 11:26 AM

yes, alembic had some basses with xlr connectors that ran to a box which also supplied the power for the preamp through one of the pins.

SGD Lutherie · #13 06-13-2011, 11:27 AM

Quote:

Originally Posted by FunkMetalBass

The quick-change battery portion on a bass is really the most sensible choice for 90% of uses, in my opinion. It's small, doesn't take up much room, built into the bass, and still allows you to switch out batteries in under a minute.

Plus, if you check your battery every now and then, it will never fail during a gig. Use an alkaline battery. So when you are getting ready for a gig, check the battery.

I suppose something like this can be handy:

STEWMAC.COM : Batt-O-Meter

I used to change my battery when I changed my strings, especially on basses where the battery was under the pickguard, but I realize some people don't change their strings too often.

PhiDeck · #14 06-13-2011, 11:28 AM

Quote:

Originally Posted by line6man

Why do you say that?
All you need is a positive DC voltage at the output. There is no need for a balanced signal unless you also needed a negative DC voltage below ground potential.

So that the signal output return current and the power supply input return current are not flowing in opposite directions in the same wire, rendering ground meaningless and corrupting the signal input to the (pre)amp.

JKos · #15 06-13-2011, 11:34 AM

You can definitely have a DC and AC signal on the same wire at the same time. It's done all the time in tons of electronic devices (like your landline telephone). You just have to have an AC coupling into the amp to block the DC from the amp's input. There is already an AC coupling at the preamps output since the preamp is operating on 0 to 9 V (or 0 to 18V) rails yet has a 0 V average output voltage to be compatible with standard amp inputs.

It's just like phantom power. An AC signal is imposed on the DC phantom power.

- John

Passinwind · #16 06-13-2011, 11:35 AM

Quote:

Originally Posted by Kabal

Or has it already and I just don't know about it?

Yes. Alembic was doing it decades ago. I ran my own basses that way for nearly 20 years too. Batteries are actually more reliable though, in my experience.

SGD Lutherie · #17 06-13-2011, 11:37 AM

Quote:

Originally Posted by PhiDeck

So that the signal output return current and the power supply input return current are not flowing in opposite directions in the same wire, rendering ground meaningless and corrupting the signal input to the (pre)amp.

You would have to use the older style of T-Powering or Line (PiP) powering for an unbalanced bass, and not the typical balanced mic type, which does require the signal to be balanced.

If would NOT work without the bass being specially set up, and seems like more bother than it's worth.

A stereo cable is a better idea.

**lowfreqgeek** · #18 06-13-2011, 11:38 AM

It can be done rather easily with a 1/4" TRS cable, but could also require rewiring the jack at the bass. You might be screwed if you forget your cable, or you'd have to have an active/passive switch on the bass to enable using a regular 1/4" TS cable in passive mode only.

It's something I've considered for many years, but never done simply cause I didn't want the hassle of ALWAYS having a special cable and special box and all that. I love the concept of the Alembic system (5-pin cable with gnd, +/-15VDC, and each pickup output separately), but the "stuff" is more than I want to deal with, even though the benefit is "studio quality" electronics in the bass. Though, I guess if your bass always sounded like it was run through a Neve console, that might be a good thing...

If anyone really wants to pursue it, PM me. I'm an electronics designer by trade. I also have experience with Lithium rechargeables and have often considered putting a Li+ pack with charge-port into my basses - kinda like the John East P-bass preamp. Consider that a single Li+ cell has nearly double the energy capacity of a 9V Alkaline, per charge. One cell with the supporting electronics can have several hundred charge-cycles, giving the equivalent energy of ~400 9V Alkalines, if handled right. Even with self-discharge and finite shelf-life, you'd probably get a good 3-5 years out of a single cell - and that's with high-current "studio grade" electronics in the bass.

Then again, nothing is so simple as a good old passive bass plugged straight in...

SGD Lutherie · #19 06-13-2011, 11:48 AM

Quote:

Originally Posted by lowfreqgeek

It can be done rather easily with a 1/4" TRS cable, but could also require rewiring the jack at the bass.

You don't have to rewire the jack at all. On an active bass the ring part of the jack gets shorted to ground when you plug in a regular mono 1/4" plug. This turns on the battery, which has its other end going to the circuit.

If you jumper the battery clip, now the ring connector goes straight to the circuit. To do this all you need is another battery clip with the two wires connected together and taped up.

So now the ring connection will supply power to the active circuitry.

Easy as pie, and reversible.

Quote:

You might be screwed if you forget your cable, or you'd have to have an active/passive switch on the bass to enable using a regular 1/4" TS cable in passive mode only.

Right, if you forget your cable, you would nee to open the bass, remove the jumper battery clip, and plug a battery in.

If you want to get fancy, you can wire in a backup battery and a switch inside the bass. Providing you have room to do so.

stflbn · #20 06-13-2011, 11:51 AM

John East has a rechargeable onboard preamp.

Additional cables, connections, outputs, blah blah blah... all would add additional potential problems for failures that are FAR beyond that of a battery going dead from 6 months to ayear.

However... IMHO... how freaking hard is it to replace 1 or 2 nine volt batteries every 6 months. I replace mine every time my dentist calls me to remind me I have a teeth cleaning appointment.