Do you have a picture of you probe setup? I’ve been trying to make a probe to measure rotating objects using Rise and fall of a magnetic field. Have had some luck but am getting a lot of noise through – assume it is from the bias voltage?

Thanks for your help

Mark

I am hoping to use my ipod touch 4G and your app signal scope pro
to take some readings on rotating machines with an external accelerometer. Could you describe in detail or with pictures what I would need to make this work.

Thanks
Mark

Your best bet for developing iPhone accessories, including for the headset jack, is to join Apple’s MFi program.

Ben

I forgot to mention the microphone’s specifications:

# Sensitivity: -44 dB (+/- 3 dB)
# Output impedance: <2.2 kΩ
# Directivity: Omnidirectional
# Current consumption: 60 dB
# Nominal operation voltage: 2V
# Max operation voltage: 10V

To me they look like it should work no? just not sure, whether the level is low enough?

Is the clicking noise I hear what JB Tompton refers to as preamp clipping? and is that happening, because the sensitivity is not low enough (lower than -64db better)?

Thanks in advance!

I have an I phone 4 for which I am currently designing a headphones cable (3.5 4pole jack on one end, two RCA (left & right) for the headphone cups, and one sub-miniature electret microphone connected to ring 3 and sleeve of the 4 pole Jack). Now the problem is that even though the electret moicrophone gets recognised (particular load requirement’s met to signal the OS that a microphone is connected), I get weird clicking/ cracking noises in my recordings, pretty similar to an old vinyl. They are similar to the rhythm of a heart beat, going CLICK.click….CLICK.click….CLICK.click…. Any ideas why that is? I can hear the stuff I am recording but as I said these are accompanied by these load annoying noises. The mic needs a 2-10V power supply for its internal pre-amp, so, considering the bias voltage delivers 2.7V then that should be sound (excuse the pun), or not? Another electret lapel mic that (one without external power supply) I bought of ebay worked absolutely fine. It was advertised as working with the Iphone, Ipod etc. I opened it and found the FET, and three resistors (1 bigger and 2 smaller ones). I know that there needs to be at least one resistor in those mic circuits (often a 2.2k resistor) to set the output impedance, but what are the other 2 smaller ones for? Does apple have resistor coding for the headphone jack too? I know that the dock connector uses resistors on pin 21 for identifying different accessories (e.g. 1MOhm for belkin auto adapter). I am very confused about these clicking noises. I would really appreciate if someone could help as I am not able to find any more information on the internet.

Thanks in advance!

Thanks for your feedback. Actually what I want to do is to use the iPhone/iPod touch audio input to interface an external sensor (e.g. temperature,cardiac signal). I was wondering if you can provide me with electrical characteristics of the audio input such as max/min input voltages and currents,offset(bias) voltage etc. If you don’t have this information, I would be very grateful if you kindly let me know where to find it.

Thanks in advance

i’m reading this article with great interest. i’ve been thinking about doing something for my iPhone, and i have posted at various places already, with no luck … Basically, i’d like to be able to plug my guitar on the iPhone, and in the voice recorder record it, for example, instead of using the internal microphone.

But the big problem is that i’ve opened a senheiser handsfree kit, sadly my electronics skills aren’t sufficient for me to understand what would be the required circuitry for this to successfully work…

So far, i have bought 4-contact 3.5mm male jack (To go into the iPhone slot), and then one 3.5mm jack female stereo (For my headset) and a 6.5mm female jack mono (For my guitar). I’ve soldered directly everything together using common-sense logic, and i’m actually only having the headset working… But the iPhone doesn’t actually seem to “detect” that there is a mic on my circuit, and keeps using the internal mic… i believe the 3 very small components on the senheiser PCB were designed to allow the iPhone to “know” there’s a mic here.

Can anyone please help me with such project? i’d be glad to help myself anyone willing to do so, by offering beer, coffee, or similar help in my skill domain

Thanks a lot,
Pierre.

Note: i’m very sorry if i’m making some typos or mistakes, i’m not an english native-speaker.

Did u mean that I need to get a cable that’s created under MFI so that I can be sure it’ll work?

Yes. You can get a custom cable to work, but you have to know enough about the iPhone’s headset jack behavior (Apple makes the relevant specifications available via the MFI program).

I’m considering placing order for Protrack since I can’t get it in Singapore, but is there a cheaper alternative that can work like Protrack?

You could get a Belkin TuneTalk, or similar iPod microphone with line input, for considerably less than a ProTrack. You’ll also need a cable with a mini-plug on one end and a 1/4″ plug on the other end for your bass.

I tried connecting both my bass and guitar but neither worked so I don’t think the missing input is related to the roll-off of lower frequencies.

Did u mean that I need to get a cable that’s created under MFI so that I can be sure it’ll work?

I’m considering placing order for Protrack since I can’t get it in Singapore, but is there a cheaper alternative that can work like Protrack?

Thanks,
Wendy

As indicated in the article, above, the iPhone needs to see the right load on the headset mic input, before it will select it as the active audio input for your apps. It looks like you would have a similar problem with the PRS Guitarbud cable, since that cable does not look like it was developed under the MFI program (Made for iPod) either. Sometimes, you can get the iPhone OS to select your headset input cable, by plugging it in very slowly, but that can get frustrating since it often doesn’t work.

Another issue you may want to consider is that the headset input rolls off the low frequencies of your input signal, which would be particularly troubling for a bass guitar. (There is some discussion of the low-frequency rolloff elsewhere in the iPhone section of this blog.) Your best bet might be to work with a line-input accessory connected to the dock connector (like the Belkin TuneTalk, or similar, which is also discussed in other posts within this blog).

Ben

I bought Riotfx and followed the instructions on the app company’s website to create a cable that can connect my bass guitar to the iPhone.

However whether I’m plugging the yellow, red or even white RCA to my bass, I can never get any input from
the bass to the iPhone.

I have emailed Riotfx for help, but would like to try my luck here and ask if anyone might be able to suggest Amy possibly solution toy problem?

Thanks in advance

Wendy

I have found electrets rated at -64db tend not to overload the
input whereas the venerable WM-61A and others rated more sensitive
will.

All in all it’s a great little mic input from Apple but is not a
good prospect to make line level or pro caliber inputs possible which is why Apple designed in better options.

I suppose it is human nature for us to attempt to see just how
much we can get out of such a cool gadget…

I’d like to know at what SPL does the original iPhone mike input clip–How loud a sound is needed to drive the iPhone preamplifier into clipping?