iRig (with DIY impedance matching cable?)

[Skruffyhound]

How crucial is the ferrite bead?

Probably not that important, I got my version to work without one, but if you want to use it in a lot of different environments you can find one in just about any old piece of electronica or on the ends of your computer connectors usb/firewire/power cables. Used to cut down EMI and RF interference.

There's loads of clone mac gear now, just hack a video cable.
Good luck.

[Keeb]

How crucial is the ferrite bead?

Can it be omitted? And if it was, what are the possible side-effects  

Also, can anyone recomend a good US based contact for the 4 pole 3.5m plug that is used?

I didn't use one and don't think it's needed. I mean I'm sure it has a use in blocking unwanted noise,like others have said, but I haven't experienced feedback issues at all.

I bought a cable that had plugs at both ends, so I got two plugs... (http://www.ebay.co.uk/itm/200639836878?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649)
A bit of a hassle to use the wires for soldering but not to bad. Can't help you with a US distributor though.

[DavenPaget]

How crucial is the ferrite bead?

Can it be omitted? And if it was, what are the possible side-effects  

Also, can anyone recomend a good US based contact for the 4 pole 3.5m plug that is used?

I didn't use one and don't think it's needed. I mean I'm sure it has a use in blocking unwanted noise,like others have said, but I haven't experienced feedback issues at all.

I bought a cable that had two plugs on each side so I got two plugs... (http://www.ebay.co.uk/itm/200639836878?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649)
A bit of a hassle two use the wires for soldering but not to bad. Can't help you with a US distributor though.

Seemingly , i know how irritating soldering headphone type wires are , but it's manageable if you have a soldering station with a thin tip and skills built up .
I tried soldering a 0805 blank form to wires and succeeded , i don't need a vias for everything !

[BoxOfSnoo]

Yeah!

I finally built this and got it running using Keeb's layout.  My own was too massive and unwieldy 

I had a bad J201 so it didn't work for a while (again).  Once I swapped it out it works!  I tested it in AmpKit.

However, in the meantime while trying to get this thing running, I bought an AmpKitLink adapter.  Now that I test both of them back to back, let me tell you the sound quality of the Peavey thing is miles beyond the iRig.  The iRig thing has feedback like crazy on distorted amps, the AmpKit Link has none.

As for the software, it's pretty close, between AmpKit and Amplitube, from a few quick tests.  The AmpKit Link still makes Amplitube sound better though.

Unfortunately I haven't got the guts to open my AmpKit Link just yet, so no pics or schematics yet.

[fakcior]

Can you do reverse engineering of Peavey Ampkit?

Cheers

[reppa]

I tried this one http://www.planetz.com/?p=1531   . I used  a 2n3819  instead of mpf102 . For me it worked , I used a 10k trimmer instead of R3 for testing but it's not necessary if you don't have active PU in your guitar you can remove it , I removed it. The sound is clean , I only have some problems when I use distortion in Amplitube but I think it's due to the input level setting on the Iphone . When you turn up level  distortion get very noisy . 

Anyone compared it with this one http://sgitornado.altervista.org/diyirig.html ?   What's the better ?

[Govmnt_Lacky]

Unfortunately I haven't got the guts to open my AmpKit Link just yet, so no pics or schematics yet.

Can you do reverse engineering of Peavey Ampkit?

+1 

[bananu7]

I've built one for myself too. Fit it into (approx, I am from Europe ) 1"x1.5" plastic box. I used 2n3819 and added the additional 10kOhm at the end. I don't think it really matters, but I've put 100kOhm at the front (before the transistor, it varied from circuit to circuit). I've attached about 4" cable with male 3.5mm jack from one side, and the 1/4" jack socket at the other.

It works OK, but I've experienced some feedback problems, which were ended by turning no-feedback to "auto". I also didn't ground the 2nd output channel, which might be a good idea.

I can send some pics and schematic that I used if anyone is interested.

[Skruffyhound]

Post what you've got, I'd like to see it.

[bananu7]

Here they are. It's my first circuit on board ever, so it might look a bit sloppy. Who cares, it works

http://dl.dropbox.com/u/31542899/MagicBlackBox/photo_1.jpg
http://dl.dropbox.com/u/31542899/MagicBlackBox/photo_2.jpg
http://dl.dropbox.com/u/31542899/MagicBlackBox/photo_3.jpg

//EDIT: It might not be clear why I didn't use male TRRS connector and embed the headphone jack in the box, too. There are two reasons for that:
1. I already had TRRS plug - 2x TRS socket splitter.
2. It's now more versatile, as it can also be used with devices with separate mic input, such as PCs.

[Skruffyhound]

Thanks, looks good.
I'm actually waiting a bit with this again, until I eventually upgrade my iPhone , the 3gs is not powerful enough.

[bananu7]

Did some live tests recently - the feedback appears only on high gain amps/distortions/presets in general. It's pretty funny, because there seems to be a hard limit (feedback - no feedback) rather than linear increase as with real hardware.

Do any of you have any ideas for the possible solutions for this?

[ragulka]

Hey, has anyone tried their cable with a Macbook Air or Macbook Pro Retina headset port? Does it work?

When I plug in my iPhone headset into the Macbook Air, it detects the headset microphone and uses that instead of the built-in mic - I'd like to use my diy irig cable the same way.

I built my cable based on this: http://www.planetz.com/?p=1531 (I used 2N3819 instead of the MPF102) - and while it works beautifully with my iPhone, I cannot get it to work with my Macbook Air. The headphones work, but the external microphone/line-in is not detected. Maybe I am missing something very obvious, impedance matching or something?

I wish I could get this to work with the Macbook

[pappasmurfsharem]

THere are certain MacBook models that the interfaces don't work with. Since they are designed for the 2.2v or whatever it is that the iPhone Mic Input  runs on. Certain MacBook models use line in more Mic inputs.

[add4]

Sorry for reviving this, but i have a few questions i'd like to ask.

So i plug my guitar on this little box and the output pulg into the headphones plug of my iphone and it takes the signal from there and routes it through the iphone's speaker after processing? seems like a strange signal flow to me ..

my other question is : the circuits i see, there is no power source?? does this transistor powers itself magically?

Thanks for making it clearer

[mthibeau]

Sorry for reviving this, but i have a few questions i'd like to ask.

So i plug my guitar on this little box and the output pulg into the headphones plug of my iphone and it takes the signal from there and routes it through the iphone's speaker after processing? seems like a strange signal flow to me ..

my other question is : the circuits i see, there is no power source?? does this transistor powers itself magically?

Thanks for making it clearer

The signal flow makes sense as the headphone jack on an iphone/ipad is both input (the mic) and output (the headphones). The irig just passes the headphone output from the iphone to a jack on the iRig. I don't think you would want to use the built in iphone speaker, that would sound like crap, I would run the headphone out of the irig into a stereo or mixer.

The phone provides power (normally for the microphone that is part of all iphone earbuds), so that is how the transistor gets power (2.2v I believe).

[OBITO]

> I drawn the iRig circuit

Thank you for your very sharp eyes.

> WTF are the components marked as FB? Circuit breakers?

Ferrite Beads to reduce radio frequency signals (an iPhone is full of digital and radio signals).

> Can someone read the code for Q1? Is it a JFET, MOSFET or what?

If R5 is missing, then it has to be a JFET.

> The capacitors C1 and C2 form a band pass filter. Can someone specify those using filters theory?

Not without values.

And I bet it turns out that C1 cuts subsonics, C2 cuts supersonics. Technically it may be a 50Hz-15KHz bandpass, but that is such a wide band that we can usually consider it as a hi-pass and a low-pass which hardly affect each other.

> C3 is also meant to filter high freq signal.

Yes.

> For its acurate calculation we need to know what semiconductor Q1 is.

Maybe not. At higher voltages all the semiconductor devices are "high" impedance, circuit impedance is dominated by resistors. This FET is working at quite low voltages, so may not be very-high impedance, but not much less than the R4 VR1 iPhone resistor network.



R2 can't be 39 ohms. Could it be 39K?

R1 should be a resistor and probably larger than R1 because guitar signals are bigger than the working voltages we can get from an iPhone jack. The maximum clean JFET gate signal is probably 0.1V-0.3V, guitars often exceed 0.1V and can go as high as 0.5V.