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mic for a Korg KP3 Kaoss pad?

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mic for a Korg KP3 Kaoss pad?

Postby ryan mead » Sat Jul 09, 2011 3:43 pm

<RANT>I don't understand these 2-conductor 1/4-inch prosumer "microphone" inputs. What am I supposed to do with this? Why can't they just give me an XLR input and enough gain for a dynamic mic? (Yes I'd have paid extra for that!)</RANT>

There's precious little information on the Korg KP3 page, and in the manual all it adds is "Mic input jack / monaural phone jack". Hmph. So it's a TS jack and I'm given no information at all about input impedance.

Let's say I want to keep things simple and light, so I'd like to avoid using any sort of preamp or other box between the mic and the pad.

Are we talking battery-powered capacitor mic? Can anybody suggest a good cheapish model? I've got $$ but would rather not spend it as I've got some good mics already and this would just be for live vocoder silliness. So I guess a tight cardioid pattern would be another criterion.

Also, this application's mono but a stereo mic's not out of the question as it might then do a bit of double duty with a field recorder. So feel free to suggest either mono or stereo models.

thanks in advance, all
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What mic for a 1/4-inch TS "mic" input?

Postby ryan mead » Mon Jul 11, 2011 2:32 am

Awful quiet here! I must have asked my question wrong or something-- here we go again:

"What mic for a 1/4-inch TS 'mic' input?" i.e. unbalanced and presumably needing to have a really strong output level.
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Re: What mic for a 1/4-inch TS "mic" input?

Postby ef37a » Mon Jul 11, 2011 7:54 am

http://www.maplin.co.uk/akg-d-44s-vocal-microphone-347524
Google is your friend!

But for that money I would go for a Prodipe and a Maplin inline debalancing transformer.

There is no reason why an unbalanced input should have low gain and be noisy. The mic input on my Philips DCC is fantastically good, as are those of my Teac A3440, just don't expect to run 30mtrs of cable is all!

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Re: What mic for a 1/4-inch TS "mic" input?

Postby ryan mead » Mon Jul 11, 2011 12:49 pm

Hi Dave, thanks for the reply. (Except for the Google reference, which I found a bit patronising, having done an extensive search before posting.)

I kind of assumed that the input on the kaoss pad would be weak and noisy because of the way it's presented (on a 1/4" TS jack) and because the unit has a very wide feature set, so they couldn't have had much of a budget for the mic input.

Hence the assumption I needed something battery-powered.

However if you're suggesting that might not be the case, I'd much rather use my SM58 if I can get away with it, with what you're calling a "debalancing transformer".

So by "debalancing transformer" (I did fruitlessly <ahem> Google it), do you mean this?

I assume not, as it and everything else I've found has an output impedance of 50kOhms and thus seems intended to work into an instrument input, not a baffling 1/4-inch TS "mic" input.

None of this is helped by the fact that Korg don't publish the input impedance of that jack. (I've sent an email of inquiry; no response yet.)
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Re: mic for a Korg KP3 Kaoss pad?

Postby Mike Stranks » Mon Jul 11, 2011 1:07 pm

I've been in this situation many times...

These days if the kit is not ancient I'll just take a low-impedance dynamic mic - SM58 is fine - and, using an XLR to TS cable, give it a shot. Most times it works fine as is with no apparent detriment to audio quality - given that you're using a cheap 'n' cheerful input in the first place.

In rare cases I have to experiment with if both pins 1 and 3 of the XLR should be connected to the sleeve of the TS, but this is seldom an issue.

HTH. Mike
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Re: What mic for a 1/4-inch TS "mic" input?

Postby ef37a » Mon Jul 11, 2011 1:25 pm

Yes that's the chap Ryan.
I would not worry about the 50k part I have used them on the inputs of my Teac and I do't have a clue what the Zin is!

Mikes' point about just unbalancing an existing mic is worth a shot. You should only run into trouble with hum if you need a long lead on a quiet source and thus a lot of gain. But then if you don't have "the bits" handy to make an XLR to TS lead you won't buy them for 9quid!

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Re: mic for a Korg KP3 Kaoss pad?

Postby ryan mead » Mon Jul 11, 2011 1:28 pm

Thanks Mike!

I was thinking of doing something similar. I assume that an XLR to TS cable would throw away one half of the balanced signal, thereby causing a loss of volume, no? Nevertheless, sounds like the cheapest way forward...
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Re: mic for a Korg KP3 Kaoss pad?

Postby ryan mead » Mon Jul 11, 2011 1:33 pm

Happy 3000th post Dave!

So is there anything to be gained by doing it one way or the other? What exactly is inside those inline impedance matchers?
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Re: mic for a Korg KP3 Kaoss pad?

Postby ef37a » Mon Jul 11, 2011 1:41 pm

ryan mead wrote:Thanks Mike!

I was thinking of doing something similar. I assume that an XLR to TS cable would throw away one half of the balanced signal, thereby causing a loss of volume, no? Nevertheless, sounds like the cheapest way forward...

Nope, no worries there. The only time you will get a 6dB drop is from a balanced output that uses an amplifier in each "leg", common on top grade mixers etc but for most of us mortals outs are impedance balanced.

Dynamic mics like the 57/58s are balanced of course but "floating" the signal wires have no connection to case. Some very old mics did have centre tapped output traffs I believe and here again using 1/2 the winding would lose you 6dB.

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Re: mic for a Korg KP3 Kaoss pad?

Postby ef37a » Mon Jul 11, 2011 1:48 pm

Wow! Doesn't time fly when you are having fun! (I think?).

"? What exactly is inside those inline impedance matchers?" At that price? A pretty small, pretty sad, pretty poor transformer*. The "500-50k" spec would indicate a 1:10 traff but I doubt that.If I can find mine I will measure it.

*But 'tis only rock and roll? (Sowter do far better but 40quid?!)

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Re: mic for a Korg KP3 Kaoss pad?

Postby ryan mead » Mon Jul 11, 2011 1:53 pm

You make it sound like it would be better to just use the XLR to TS cable, thereby avoiding said sad transformer and the impedance mismatch it would throw up anyway...
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Re: mic for a Korg KP3 Kaoss pad?

Postby ef37a » Mon Jul 11, 2011 1:59 pm

ryan mead wrote:You make it sound like it would be better to just use the XLR to TS cable, thereby avoiding said sad transformer and the impedance mismatch it would throw up anyway...

Maybe! They do have the benefit as I say of preserving a balanced line up to the XLR,something we needed with modest vocal levels around a lot of 50Hz kit but if you intend to yodel at zero mm not a problem.
Crap traffs also have their advocates and for voice frequencies you don't need superb ones, also this was into 15ips tape...Need I say more?
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Re: mic for a Korg KP3 Kaoss pad?

Postby ryan mead » Tue Jul 12, 2011 5:36 am

Well, I heard back from a guy at Korg who doesn't know what the input impedance is, and said just to use an SM58.

Nevertheless I might spring for one of those transformer-based doodads as it would do double duty around here on an instrument input as well.
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Re: mic for a Korg KP3 Kaoss pad?

Postby ef37a » Tue Jul 12, 2011 5:55 am

"as it would do double duty around here on an instrument input as well."

How so exactly? Actually if you make the adaptor leads up you can use the traff "backwards" as a tolerable DI device.

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Re: mic for a Korg KP3 Kaoss pad?

Postby ryan mead » Tue Jul 12, 2011 6:02 am

I don't mean plugging a guitar into the mic jack, I mean using an SM58 with the "instrument" input (so-labeled 1/4-inch TS jack) on yet another silly device (Electrix Repeater looping sampler), which (presumably, don't have the documentation here) has higher input impedance than the Korg.
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Re: mic for a Korg KP3 Kaoss pad?

Postby ryan mead » Thu Jul 21, 2011 4:57 am

Well, I got one of these (Audio Technica CP8201 impedance matching transformer), and it seems to work fine with an SM58.
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Re: mic for a Korg KP3 Kaoss pad?

Postby ef37a » Thu Jul 21, 2011 5:19 am

Morning Ryan,

I am happy that you are sorted. That transformer is very likely a far better quality device than the Maplin one tho' I do not believe the response spec for one moment! (they carefully ommit dB points!)Still, the 50's are not noted for a wide bandwidth.

The in and out Zs ("nominal" one notes) suggest a transformer ratio of 1:14 giving you a voltage boost of 23dB and that puts an SM into the lower end of a capacitor mic sensitivity spec*. This works I suspect because the pre amp is probably our good friend the TL071 and has a high, maybe 1M Ohm input impedance.

*FYI some tests I did recently showed an AKG P150 was 18dB more sensitive than an SM57. Not a super accurate test I will admit but close enough at mid band.

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