An XLR Challenge to All !!!

[boogietube]

I've read every thread concerning XLR outputs, and I haven't come across anything that I can either understand or build.
I am a relative noob.

Here's the challenge:
Come up with a pcb design with balanced (XLR) output using readily available components. As well, have the standard 1/4" output avaliable to use at the same time as the XLR.This is mostly for bassists to use stuff like the flipster, but guitarists may benefit as well (cabinet simulators etc)

Hope you guys kick up the jams man!!

Boogietube

[O]

You mean something like this?

[Pushtone]

I've read every thread concerning XLR outputs, and I haven't come across anything that I can either understand or build.

What do you plan on connecting to? A balanced bass out into - what.

I can tell you from experience here that fourmites will help you out with questions or point you to an existing schem
But no one will just do the work for you. If you want it built, it's up to you.

What your asking has been the job of the lowly DI for years.
A DI box has:
1/4" input
1/4" output
XLR out (mic-level 600ohms)

Do you need a XLR +4dB line-level out?

Knowing what you want to connect to would be helpful.

[boogietube]

Say to connect the ROG flipster or the Moosapotamus Acoustic 360 or Bass paralooper to a mixing console for live or studio application.
I realise that it's a lot of work. I just don't understand schematics like I should and it's very daunting. I am learning though. I issued the challenge because I have seen every concievable device laid out here and no one has addressed this issue. If I had more knowledge (and talent!) I'd attempt it myself.

The challenge remains!!

Sean

[Paul Perry (Frostwave)]

I guess it should be possible to make a "rock and roll" quality DI from a pair of transistors with a high value common emitter resistor & smallish collector loads.
Like a "long tail pair" phase splitter as it was called Way Back When.
And I'm almost certain AD would have a custom chip... that runs on 3.3 volts, has astounding specs, and is out of production

[Pushtone]

Say to connect the ROG flipster or the Moosapotamus Acoustic 360 or Bass paralooper to a mixing console for live or studio application.

Yeah, that is a job for a DI for sure.
I was just reading a post today where someone had a layout for the Jensen active DI schem.
That would work.

But now that I know you are going to connect an AC powered device between the bass
and the mixing console I would highly reccomend a good quality passive DI.

The DI transformers will decouple the grounds and you won't get any 60 cycle hum.
Ground isolation is very important here and with any source that is AC powered like keyboards,
guitars connected to effect and amplifiers, drum machines etc.

Active DIs don't isolate ground potentials (hummmmmm).

I still think it would be way more easy to just use a DI for this.
As a stage tech I put plenty of DI out for every show.

[Gilles C]

I saw 2 kinds of circuits that people asked for when the asked for a DI Box. One was a simple and not too costly to build, the other one was a complete DI Box with all the bells and whistles.

I already found how I would make both of them after looking at all these articles and schematics from the recent posts, but even then, if doesn't mean that it would satisfy those in need of a DI Box...

It's harder to satisfy someone else needs than to satisfy our own needs and then post the circuit to share it. But I will try to experiment with a DI circuit, all together with the other projects I am trying to finish...

Gilles

[lovekraft0]

You mean something like this?

There ya go - replace the the TL072 with a NE5532 (or similar), use tantalum caps and metal film resistors, and add a quiet +/- 15 volt 250mA supply, and you've got pretty much mid-level pro audio quality (at least as good as the M@ckie/Bëhringër mixers it's likely to be plugged into).

[markusw]

I did a layout for this xfmr less gesign  http://sound.westhost.com/project35.htm (fig 3).

Fits in a 1590BB, with only one battery though. If you're interested I can post the layout tomorrow (or on weekend).

Markus

[Gilles C]

Here is the first circuit I will try to experiment with.



I left the pins for the opamp not connected for now. I was wondering if it was worth using the Phantom Power, or if a battery would be ok.

Markusw posted while I was writing this... so that's good news, people are interested.

Gilles

[markusw]

I was wondering if it was worth using the Phantom Power, or if a battery would be ok.

Since I prefer to use it with phantom power (and since I managed to put in only one battery due to the huge non-polar caps) I inlcuded this option. Also phantom power doesn't eat battery

Markus

[Cliff Schecht]

Phantom power would be a good idea. It would be one less thing to worry about (I don't use batteries in anything anymore).

[Pushtone]

Passive DIs don't need any power what so ever to do this.

They're like, passive.



Most pedals used for this are like the Sans Amp Bass Driver or the Bass Tonebone.
A preamp section coupled to a DI output.

How about a SansAmp Bass Driver Schem. What circuit do they use to get that XLR output.

[markusw]

Passive DIs don't need any power what so ever to do this.

They're like, passive.

As far as I understood for a good passive DI box you need a good xfmr (e.g. Jensen) that are pretty expensive. Didn't check the prices though.

How about a SansAmp Bass Driver Schem. What circuit do they use to get that XLR output.

I would like to see this schem too

Markus

[boogietube]

The challenge is still on - lots of great ideas guys!! PCB and an elegant solution is coming - I can see it now!!
Sean

[Mark Hammer]

Hi Sean,
The thing to recall about balanced lines is that they are fundamentally a solution for keeping noise at bay in low level mic signals.  Your average passive dynamic mic doesn't put out nearly as big a signal as a guitar, and traditionally it often had to run very great lengths to get to the PA.  The output impedance of the mic was low enough that cable capacitance and treble loss would not be a big issue. However, with that length of cable (think Bob Hope wandering about with a handheld mic on stage in Viet Nam entertaining the troops on a 60ft wide stage with a PA parked somewhere way off to the side), the odds are pretty good that noise would be accumulated between the mic and PA input. 

That's the benefit of balanced lines.  If any noise is picked up along the way, it is shared in common between the two hot leads, and cancels out at the mixer input. 

So why am I telling your this?  Because if you're going to run a hot output (and all the circuits mentioned in this thread are bloody hot compared to an SM58n or Radio Shack "highball" mic) for a grand length of a couple of feet, the odds of accumulated noise getting in there and needing balancing to cancel it out are pretty damn slim.

Make no mistake, balanced lines ARE useful and important, just not so much in this instance.  Indeed, a standard mono phone plug, wired up to two pins on an XLR plug is probably all you really need.  I may be wrong, but my gut sense is that you can worry about this much less than you're currently doing.

[Pushtone]

I may be wrong, but my gut sense is that you can worry about this much less than you're currently doing.

He still wants to connect to the PA. That means connecting through the mic snake which could be anywhere from 100 to 300 feet.
At the end of the mic snake will be the consoles mic preamp so you will need to reduce the level down to mic level anyway.

This sure sounds like a DI to me.
On stage you have two things connected to the snake and PA; that is mics and DIs.
If it can't use a mic then its a DI. No other options.

[Gilles C]

I second that.

My use for a DI is when I connect my guitar (accoustic or not) direct to the console. And that includes effects before the DI Box.

Some places like to have control on the sound from the console.

One of the best DIed sound I had once was with my Behringer DI Box with the 4 x 12 cab Simulator ON. And the console was on the second floor.

Gilles

[boogietube]

Yes Mark, you may be right. The other guys have a point too. I want to run long cable lengths for my bass player and have one of those pedals I mentioned dictate the tone to the mixing console. We are playing all of the large venues in town and it would be great to add a DI out from the Flipster, Blender or any other Bass preamp type of pedal out there (while still having the provision to have a 1/4" to the amp) As a matter of fact, there are two other threads concerning this subject that are active right now on this page. Every Bassist would benefit from this incoroprated design.
The challenge continues!
Sean

[Gilles C]

I just remembered another use for a DI Box.

You can connect your guitar amp speaker out to "some" DI Boxes to send your amplifier output to the console. But you need resistors inside the DI Box to do that. They adjust the level of the signal for the DI Box circuit.

That's the best of both worlds.

Gilles