Input options and microphones

[jorgren]

Thanks 36. I would imagine it would be pretty easy to adapt that to copy/paste - the functionality of copy/paste is actually simpler.

[Agent36]

Thanks 36. I would imagine it would be pretty easy to adapt that to copy/paste - the functionality of copy/paste is actually simpler.

I'm sure they are testing the waters the investment on hardware alone makes me think they have plans.

[pstidworthy]

I develop RiotFX and over the past couple of years I have tried many circuits to get a clean tone into the iPhone - including audio transformers, resister networks and active circuits. JOgren - I haven't yet tried your circuit yet (I will - thanks for sending it!) but I was interested to know what the total DC resistance was across the JFET/resistor (i.e. what the iPhone 'sees') - the device can be quite picky about this, and in my experience it should be between the 1Kohm - 4Kohm range: outside of this some devices may not detect its presence (so you end up just getting audio from the built-in mic).

The solution that works best for me (currently) is a simple resistor network with a DC blocking cap. The cap is located between the guitar and the shunt resistor, which means that DC resistance presented to the device is that of the drain. Unfortunately as mentioned this needs to be fairly low (3.3Kohm). For this shunt you need a fairly low series resistor otherwise you get too much attenuation - so the input impedance is low. Still beats the guitarbud by a mile though

WindyCitySpud: If you find that RiotFX is too 'hot' this could be down to two factors:
1) Your guitar is overdriving your iPhone/pod/pad leading to digital clipping.
2) RiotFX is amplifying the signal too much.

I would say that in the case of (1) it would be much more noticeable in RiotFX than in Amps&Cabs because of the nature of the effects, some of which are more complicated in RiotFX than A&C (no offense intended to ground up audio - its a nice app!)... if an digitally clipped signal is passed through some of the effects in RiotFX the artifacts coming out the other side may not be too pleasant

In the case of (2) this could simply be fixed by giving you more range on the 'gain' control (above the master volume at the bottom). Currently it boosts the signal, but it could be easily adapted to attenuate the signal too. This seems like a sensible modification to make - I'll be releasing a minor update when I get hold of an iPhone 4 (hoping for greater improvements in the sample rate/latency tradeoff) so I'll put the gain fix into that - I hope it helps. In the meantime feel to contact me about any other concerns (publicly here or privately: contact@riotmode.com).

[jorgren]

pstidworthy,

I believe the JFET circuit will provide an apparent resistance in the 1.5K-4K range. It is of course somewhat dependant on the properties of the individual JFET used, and they do vary. I know of two units built (mine and one other user here), and both have worked fine, but that is an admittedly small sample.

We're looking forward to the new version of your app, hoping it has recording and copy/paste capability so it works with Multitrack DAW.

[RolfBertramDotCom]

I want to do one-track at a time, multitrack recordings with ipod touch synths. If I want to record from a soft synth that runs on Ipod Touch, would I need to have 2 ipod touchs? It would be nice to have this work without going Digital-Analog-Digital.

[pwnified]

I've been thinking about this a lot actually. Right now it's fairly limited as all operations must be done using copy/paste. A typical workflow using NLog synth:

Close MultiTrack and open NLog synth
Set the tempo to the same as multiTrack.
Record in NLog to a temporary file (cant listen to backing track or reference)
Use the copy feature of NLog to copy the file
Close NLog and open multiTrack, paste the audio, move and trim
Repeat the whole process for each "overdub"

With multitasking, this process is a lot less painful.

There really needs to be some kind of inter-app communication now that we have multitasking. The idea is that multiTrack will be running in the background, recording, but getting it's input not from the audio subsystem but from some decided up protocol (similar to rewire, possibly using the network protocol). There is much to be thought about for this to work. But if we could come up with a protocol and get all the app companies on board, it could be great. The workflow would then be something like:

Start recording in multitrack (indicate you want to record from "rewire")
Switch to other app (multiTrack continues to record, and playback other tracks for monitoring)
Other app sends it's output to the "rewire" node instead of the audio subsystem.
MultiTrack recieves the audio, records it, and blends it with playback audio (input monitoring)

It's a thought, anyway. I'm fairly certain that we have everything we need to build such a protocol. Design and implementation, and getting app makers to use it, is another story.

[jorgren]

pwnified, you're exactly right.

I have just finished a song using the method you describe, in fact Nlog is one of the main synths I used. The apps with good copy/paste functionality that I've used are MultiTrack DAW (obviously), Nlog, DrumTrack8, and Noise.io. Argon has copy/paste, but records only a few seconds, so in real life I have to record with an analog connection to my computer and WiFi it back. By keeping everything at the same tempo and using the same scale/key, I make clips that fit together pretty easily. But the piece would have more life to it if I could hear the existing material as I play new material.

A real-time app-to-app connection for audio (and better yet MIDI for sync, notes, FX automation...) is exactly what would take us to the next level.

One interim method would be to make a backing track (perhaps just drums, or drums and a bass line), WiFi it to the computer, and add it to your iTunes library so you can play it in the background while you record new stuff. The current OS (I'm using 3.1.2) does support this type of multitasking.

[Forkmann]

Jorgen - Can you clarify which is source/drain for the JFET in your cable schematic?

Thanks!

[jorgren]

Forkmann,

Interestingly, the MPF102 is perfectly symmetrical, so "source" and "drain" are interchangeable. However, if you want to follow the labeling, as I've drawn it the source would be the pin connected to ground through a resistor.

[Forkmann]

Thanks. I realized it was a bit of a dumb question after thinking about it a bit. And then of course buying the part and seeing it didn't matter anyway. I wired this up last night and for guitar it is MUCH better than a straight connection. I was using the free version of Amplitube and have to say I wasn't blown away or anything. Not sure if my expectations were just too high for using a phone as an amp simulator or if it is just the limitations in the input interface.