adapter for sound *in*?

[mane]

Hi all!

For sound out, there are adapters (I already have one), which convert from that custom 2.5" jack to a standard 3.5" - which even let the built in microphone active. OK.

But is there any adapter for the opposite? Converting the microphone / sound in part of that custom 2.5" to an e.g. 3.5" - so that some standard microphone or some other sound pickup could be attached?

Wether built in speaker would be left active or not isn't relevant for me.

Background: I have one of those programs for tuning musical instruments. It works fine with the built in mic in relatively silent rooms and for acoustic instruments. But imagine beeing on stage between two songs while the crowd is cheering!

If no such accessory is available: I would spend some extra Euros for a second hands free thing, cut off the side with the 2.5" plug and tinker a 3.5" on the open end.
But will this work - or have I to include some resistors or such?

Thanks, greetings
Manfred

[hanmin]

There are such adapter on sales

http://www.expansys.com/product.asp?code=113967&tab=0

As for the issue of resister, I don't think you will be needing any. I've no experience on electric musical instruments, but a microphone is a essentially an active resistor/capacitor that convert sounds to resistance/capacitance-variation and hence electric signals. It does not produce any form of voltage itself (eg. you do not need battery for microphone).

Hence, it depends on your musical instruments. If you were to get the adaptor above, perform a voltage test on all 6 combinations (of the 3 contacts) to make sure your instruments does not produce any form of voltage/current. If it does not produce any form of voltage, you ought to be safe for a direct plug-in.

[mane]

(oops, did I mix up " with mm in my initial post :o )

Are you using this adaptor yourself? With a Prophet? Does it work?

Not to appear nagging, but there are three facts that make me doubt:
- the description there tells me, that it "converts the standard 2.5mm three conductor jack"
- which can also be seen on the "larger image" (those pictures at expansys often are near causing eye cancer >;-) ), where the plug has *three* contacts
- description also tells us, the adaptor converts to a "3.5mm Mono Headphone Jack".

Well, the jack of Prophet has *four* contacts, and sound out comes in *stereo*. I guess that: tip and first ring are - stereo - out; 2nd ring is mic in; last "ring" obviously is ground. This I take from the fact, that my adaptor for standard 2.5mm to standard 3.5mm stereo earphones really delivers stereo out, but the internal mic is still working.

So I also guess, that this adaptor here has e.g. *mono* out on tip, mic in on 1st ring - and ground on third and last ring - which also would lead to connecting Prophet's mic to ground.

Or am I totally wrong here?

The question about resistors (and such) comes from looking at
http://wiki.xda-developers.com/index.php?pagename=Connectors
(but that's Wallaby and Himalaya wiring, and with the latter there's also an extra (5th!) "outer sleeve" connector); but you can see in the drawing there, that there are a diode and three capacitors between mic and ground, and serially a resistor (but all without values).
So I fear, that just connecting a (passive) guitar pickup won't deliver satisfying results. :(

[hanmin]

Hmm. didn't notice that one is a mono output. Anyway, can't really find one with mic and headphone out for streo (actually, gave up searching). I guess there aren't enough market for people pluging in their own mic.

As for the diagram, it looks like that, for the micrphone, the circular wiring thing is an inductor, not a resistor, since it is marked as L1. From what it seems, it looks like those capacitors and inductor is there to bias the circuit such that the mic is to be in the right impedance to pickup speech. That is more to "adjust" the mic such that it will gives the correct values (probably due to its small size?). So, if you were to plugin in your instruments directly, the result may not be that good. But probably it will. You may need to tune your software to adjust for this?

As for the z-diode there, it is a mystery to me. Can't think of anything useful for it, except to ensure the mic-in is always >= 0 (greater or equals to zero).

[mane]

Well, first of all: thanks a lot for your answers!!

I also gave up searching before posting here; also searched for a separate 4-ring 2.5mm plug; but before investing in a second headset just to get that plug, I thought I'd ask here ... :)

Inductors, resistors et all ... it's been way too long since my physics intensive course on grammar school ...

Your thoughts sound logical.

So I'll get me the headset for the plug and tinker an adaptor myself - without any extra inductors or capacitors. Will see how it works - if not, well, I'll come back here again to ask for the values of them ... and tinker along ;-)

[colida]

I build an adapter on my own out of the standard hands free headphone which was included in delivery.Unfortuately I had to destroy the case a bit :( I just made a kabel with a 3,5 mm jack and soldered it on the circuit board and bridged the build in mikrophone.Now I am able to connect a stand alone microphone to my Prophet.
Cheers

[Repose]

you can order one @ http://mobile.brando.com.hk/

[mane]

@ Repose: you mean the handsfree headphone? I already ordered one at expansys :)

@ colida: that's another idea, keeping the circuit board. Such, all capacitors etc. are in place ... maybe just looks a bit ugly, you really have to break that little housing.