Adding i2c on 301


I bought my 301 used and the previous owner ordered it with a power option (I think) instead of the i2c thing. Is it possible to add it and what do I need to do so?


There were never really any “options” - its just a matter of when the previous owner bought the unit. It sounds like you have a rev 7 board, which does require a slight modification. Have a look here to help determine which board revision you have, and then what you need to do.

1 Like

Yes. You are absolutely correct :slight_smile: I found an explanation when I searched for rev 7. Is this the only thing you need to do?

It’s the only thing you need to do to the ER-301.

Depending what you want to connect and how, you might have to modify other hardware. For example if connecting a 16n in leader mode, you might need to add pull up resistors to the 16n.

Connecting teletype on the other hand would require no further modification.

Thanks a lot!

1 Like

A question; I did this modification and it worked fine. I have now disconnected the i2c cables since I’m not using that module anymore. But I’ve starting to experience massive amount of noise coming from the 301 when I crank the volume of my system. Could it have something to do with this?

I wouldn’t think so. Have you made other changes? Moved cases? Added other modules?

Nope no new modules. Just switched back to the one I used before. I tried plugging each and every module to the output to see if it was any of them but they’re silent. I made a video just showcasing what happens when I crank the volume on the 301. I filmed this but aren’t allowed to upload film formats. I’ve attached a picture of my setup. I use the intellijel 1u quadratt into the 4 ins of the 301 to control volume of the different mixers in the chain. When I crank them there’s a lot of noise. It seems like the signal into the INs from the quadratt is leaking?

I’ve never had noise issues but others have. Wish I had a magic silver bullet to offer you but I don’t. This is probably the most comprehensive thread of tips to isolate and troubleshoot. I’d take a tour of that and see if you can find an answer.

I have a very small case, but when I plug it into my mixer directly via the case’s electrically balanced jacks (using symmectrical cables) I still get digital sounding high pitched noise, even if I remove the USB connection for the MIDI interface module.

I put a DI Box in-between: instant silence.

The only noise remaining is a very, very faint high-pitched noise that comes directly from within the ER-301 (so it is not in the audio path!), it changes due to LCD activity and is only audible when everything else in my room is totally quiet and I move my head over the ER-301.

Thanks for the tip joe! I’ll look
through there. A quick question though: would it be better to plug the quadratt into the ABCD inputs instead of the INs? I’m away from my system, otherwise i could just test :slight_smile:


Hmm weird. I have quite a high volume noise. And I don’t think I had it before so I don’t know what has happened really.

The INx ports are optimized for audio. ABCDx is optimized for CV, are calibrated for V/Oct, and can also take audio.

In short, probably so. Save INx for audio is probably the best strategy.

I believe the only difference between the ins and abcd is that the inputs have a configurable preamp. That way you can send line level signals in.

There are other differences, though they might only matter in certain circumstances.

Yeah. Tried this now but it doesn’t really help. It is this connection that generates the noise but what I can’t figure out is why the 301 is letting signal from the inputs through to the output? It feels like a user error i.e I’m doing something weird :slight_smile:

I have it setup like this:

  • Channel 1-2 is a stereo track.
  • In this I have a couple of different mixers for my synthvoices that are plugged into a bunch of inputs.
  • I run the 4 outputs from my quadratt to the ABCD inputs that are connected to The levels of 4 linear VCAs that lies as sub chains to the individual mixers (see picture).

Can I use another module to control the volume of the mixers so the signal from the quadratt doesn’t leak through?

You have to set the level bias on your unipolar VCA to slightly negative otherwise it will not close completely when modulated by an analog voltage.


Thanks! I think the problem was i had to much gain om the mixers so a lot of noise came from that.