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jwheeler 6th August 2012 09:50 AM

Internally Miked Accordion Project (5 x WM-61A)
 
Hello all, first post :D

<Start of Unnecessary Preface>
I play accordion for some songs in my band and currently we use a velcroed on mic system to amplify it (MicroVox M310). Due to mid-set instrument changes (and also my clumsy band mate using it for 2 songs) we keep pulling off the bass / "tiny button" side mic off or pulling the cable out and once pulling the entire unit off.

The inside of the mic unit is very simple. Its 3 electret mics wired in parallel and passively mixed with the bass mic and all powered by a single 1.5V AA battery.

</End of Unnecessary Preface>


I am looking to build an internal accordion mic system that possibly uses phantom power.

What I have found so far:
  • Panasonic WM-61a Microphones (and modification)
  • Bill Wall's Circuit (and upcoming circuit)
  • Conductive Tape for wiring up to the Bass Side (death to droopy, dangly wires! :p)
  • An email reply from Bill Wall saying that passive mixing isn't ideal:
    • "You’ll need to include a mixer stage for the two (or more) mics, otherwise you’ll have losses if you mix them passively (although, the passive mixing will work)"
  • Linkwitz's Circuits
  • Specifically the Stereo unbalanced circuit

Do I need it to be balanced out? Am I just creating problems for myself by doing this?

If I do a balanced circuit, do I need to mix the individual pins of the microphones together, or use a non balanced circuit for mixing and balancing later?

Are there any phantom powered mixers? (When I've searched for this, it comes up with mixer circuits that provide phantom power *face palm* :scratch:)

For linkwitz's pre-amp circuit, you can't use the same battery for the reversed voltage, can you? ('cause that would be a short right?)

Having to use two 9V batteries would be annoying :(

Cheers for reading,
James

mickeymoose 6th August 2012 01:50 PM

Interesting!
I assume you are using a full-sizzed accordion (I was just given a Camillo JR, only 2 octaves)
Where will you place the microphones?

If you intend to use the conductive tape, glued to the bellows, for getting the mic signal from one side to other, I think you would be asking for trouble. I would use a flexible thin wire (like that of a discarded heasdset) attached to one of the straps with enough lead length to accomodate standing and seating positions, 3,5 mm TRS plugs on both ends.
Active mixing is necessary (a small preamp at each mic). A balanced output will allow you phantom powering. E

Pano 6th August 2012 03:15 PM

Passive mixing will work, we do it with hand-held mics from time to time. Obviously your present system uses it. You just have little or no control over the relative levels. But that may not matter.

As for balanced, it will be lower noise than unbalanced in most practical situations (on stage), but again, it may not matter. If you use good shielded cable and a fairly low input impedance, the noise may not be bad. It's easier to do unbalanced.

kevinkr 6th August 2012 04:37 PM

:cop: This clearly belongs in the Instruments And Amplifiers forum and I suspect will get a lot more useful input in that forum. Moving it...

jwheeler 6th August 2012 04:40 PM

Quote:

Originally Posted by mickeymoose (Post 3116612)
Interesting!
I assume you are using a full-sizzed accordion (I was just given a Camillo JR, only 2 octaves)

My accordion is an 80 Bass in size.
Quote:

Originally Posted by mickeymoose (Post 3116612)
Where will you place the microphones?

Mic placement is something I plan to experiment with once I have created the microphones. I will make them with plenty of wire and I will hold them in place with blutak until I'm happy. Probably one on top and bottom of both the treble and the bass side, but one in the middle of the treble as well.
Quote:

Originally Posted by mickeymoose (Post 3116612)
If you intend to use the conductive tape, glued to the bellows, for getting the mic signal from one side to other, I think you would be asking for trouble.

What trouble do you reckon I'm asking for? :P.
I plan to, yes, stick it to the bellows but i will be going as close to diagonal as possible so as not to spread each fold apart too much. The tape is very flexible, very durable, and very thin. I was incredibly surprised how thin it was.
Quote:

Originally Posted by mickeymoose (Post 3116612)
Active mixing is necessary (a small preamp at each mic). A balanced output will allow you phantom powering. E

Do you know of any phantom powered mixer circuits?

I'm still considering unbalanced out for wireless purposes, but maybe I can do both :P

Perhaps I do everything in unbalanced, but build in a DI box before exiting the Accordion???


Quote:

Originally Posted by Pano (Post 3116686)
Passive mixing will work, we do it with hand-held mics from time to time. Obviously your present system uses it. You just have little or no control over the relative levels. But that may not matter.

Alright, probably worth a test.
Quote:

Originally Posted by Pano (Post 3116686)
As for balanced, it will be lower noise than unbalanced in most practical situations (on stage), but again, it may not matter. If you use good shielded cable and a fairly low input impedance, the noise may not be bad. It's easier to do unbalanced.

True. It's also easier to do wireless with jack. We put all our unbalanced inputs through a DI and our longest unbalanced wire is 6m but most are 3m.

Quote:

Originally Posted by kevinkr (Post 3116772)
:cop: This clearly belongs in the Instruments And Amplifiers forum and I suspect will get a lot more useful input in that forum. Moving it...

Thanks :D

AuroraB 6th August 2012 06:35 PM

FWIW - my late father was an accordion geek, and he had his Hohner mic'ed already in 1960. It was a single omni mike mounted internally on the main manual side, with an external volume/tone control, all run single ended as was customary at that time. Hum was never a real problem, even with the early 60s amps, and bass was plentiful.....

I don't think I've ever seen a mixer powered by phantom feed.... what's wrong with a wall wart, as I take it you need power for the real amps...????
Do you really want or need each channel ( bass/trebel/more..) adjustable in the main mix? If you use several mic's, I would think a simple summer with trims should do the trick to set up an overall tonal balance...??

Have you thought about cabling a multimic system...? Two or more cables exciting.....?

jwheeler 7th August 2012 08:47 AM

1 Attachment(s)
Quote:

Originally Posted by AuroraB (Post 3116891)
FWIW - my late father was an accordion geek, and he had his Hohner mic'ed already in 1960. It was a single omni mike mounted internally on the main manual side, with an external volume/tone control, all run single ended as was customary at that time. Hum was never a real problem, even with the early 60s amps, and bass was plentiful.....

I think you may be confusing what I mean about the bass. The bass side is the side with the small round buttons arranged in a parallelogram. It has its own set of reeds and all the sound comes out of this side only.

The positions of the reeds are spread out along the size of the accordion. If I was miking up for recording I would position one mic in front of me, with variations of position to capture more or less of one particular side of the accordion. But because I will play live, I'd like to get the mics up close, but not too close that it only picks up one note.
http://www.diyaudio.com/forums/attac...1&d=1344328984
Something like this?

Quote:

Originally Posted by AuroraB (Post 3116891)
I don't think I've ever seen a mixer powered by phantom feed.... what's wrong with a wall wart, as I take it you need power for the real amps...????
Do you really want or need each channel ( bass/trebel/more..) adjustable in the main mix? If you use several mic's, I would think a simple summer with trims should do the trick to set up an overall tonal balance...??

Have you thought about cabling a multimic system...? Two or more cables exciting.....?

Nothing wrong with a power socket (I'm from UK so no wall warts :p) But I'd rather use batteries than a separate supply as it'll be on my accordion. And that is the point of the phantom powered mixer. It would be built into the accordion. The only output from the accordion would be xlr (or jack if I go that route)

Cheers for the replies :D

Nigel Goodwin 7th August 2012 12:23 PM

Quote:

Originally Posted by jwheeler (Post 3117519)
Nothing wrong with a power socket (I'm from UK so no wall warts :p)

I suspect you don't understand what a 'wallwart' is?, they are as commonplace in the UK as anywhere else - for example every mobile phone charger is a 'wallwart'. It's simply a generic name for a PSU built inside an oversized mains plug.

Quote:


But I'd rather use batteries than a separate supply as it'll be on my accordion. And that is the point of the phantom powered mixer. It would be built into the accordion. The only output from the accordion would be xlr (or jack if I go that route)
It would certainly be easily possible to build a simple mixer fed from phantom power, you're only really looking at a single opamp and a handfull of components.

EDIT:

Have a look here, it would be simple to make this design into a phantom powered mixer:

http://sound.westhost.com/project35.htm

jwheeler 7th August 2012 01:20 PM

Quote:

Originally Posted by Nigel Goodwin (Post 3117678)
I suspect you don't understand what a 'wallwart' is?, they are as commonplace in the UK as anywhere else - for example every mobile phone charger is a 'wallwart'. It's simply a generic name for a PSU built inside an oversized mains plug.

Haha, no I meant we didn't call them wallwarts :P.

Quote:

Originally Posted by Nigel Goodwin (Post 3117678)
It would certainly be easily possible to build a simple mixer fed from phantom power, you're only really looking at a single opamp and a handfull of components.

EDIT:
Have a look here, it would be simple to make this design into a phantom powered mixer:

ESP - Direct Injection Box for Recording and PA Systems

Yes I found that, along with Universal Preamp/ Mixer (Part 2)

Do you know why Bill Wall's Microphone circuit has transistors before the matched resistors?

AuroraB 7th August 2012 02:03 PM

I'm perfectly aware of what the "bass side" on the accordion is..... :-)
I dabbled a little bit on it in the late 70s, when my father injured a couple of fingers and was out of bussiness for some years......

But as I was saying,- there was only one omni mic inside the main voice chamber..... the bass side still came trough plentiful......


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