Hello all! I searched but couldn’t find an exact answer, or any loosely linked answer either! I also checked info about normalizing jacks.
Basically I’d like to use the Meta with my banana synths (Serge etc) and wondered about the normalization probe, is it sensing a ground connection when you plug in a minijack? What would happen if I plugged a minijack → banana cable, ie a cable that had no ground (sleeve) connection at the banana end (for example via a format jumbler) - what would happen then, if the sleeve is floating? Do you think I would require a format jumbler with some switches that choose INT (normalized, switched to ground) vs EXT (signal from banana to tip)? Would I need this on all inputs and outputs to/from the Meta?!
Normalisation on jacks is usually done with switching contacts. When you insert the plug into the jack, it physically breaks the “normallled” connection at the tip.
If you;re connecting modules with jacks to modules with banana sockets then you only need the tip connection. The format jumbler will take care of that for you.
Hi CountModa, thank you - yes I’m aware how normalisation is usually done, but the Meta module doesn’t use switching jacks (as far as I can tell). It uses TRS jacks (stereo) where the ring contact seems to have some additional circuitry to ‘detect’ (?!) cable connection, I’m assuming via ground (?!). A little more here:
Unfortunately, as a simple person, enough of that is over my head to render it slightly beyond me (the coding aspect at least!)
My question is probably best suited as a direct email to the 4MS devs but I thought it might solicit an answer that would interest a few people with multi-format systems who wanted to explore the Meta - not just I!
I think if you have a jack on MM that isn’t mapped to anything in your patch, it won’t matter whether the cable detection sensing is happening, and you can patch a cable from that jack to your format jumbler for shared ground. The cable would need to be either 3.5mm to dual banana (with one banana plug being for signal and one for ground, and the signal one being ignored for this usage), or a custom 3.5mm to single banana cable in which the banana plug is wired to the sleeve of the 3.5mm plug instead of the tip.
Thanks mrfang - I think, from what I can understand of the Meta, that each cable connected to the Meta would need to have both tip and sleeve connected, ie always be signal / ground with 2 bananas as every single jack has the detection circuit on the ring. I think the usual approach of patching / sharing ground between devices once wouldn’t be enough, I’d need to do it on every connection. I was hoping to eliminate minijack->minijack cables entirely and just use custom banana->minijack (with one shared ground connection elsewhere via PSUs directly) but I think for it to work I’d always need to go via a jumbler box so that each connected minijack cable has ground (ring).
I’m pretty sure ring (used for plug sensing in the stereo jacks) isn’t important here since ground is on the sleeve. I think you can get by with one ground connection.
The easiest thing to do is to not have any format jumbler, but just use TS (mono 1/8") cables that have the shield floating and the tip connected to a banana plug. Then just patch normally – plug the 1/8" TS side to the MM and the banana side to whatever you’re patching to. The TS plug will tell the MM it’s patched and it’ll just work.
You will need to connect the ground of the eurorack system to the ground of the serge system in one place, but that’s always the case even if you’re not using a MM.
Edit: I think I understand the question (and misunderstanding) now!
Yes, you can do this without any minijack->minijack cables. If you have a minijack->banana cable that uses a TS plug (not TRS), then the TS plug itself will short the ring terminal to ground. This happens on the PCB: the metal on the plug itself shorts the ring terminal of the jack on the PCB to the shield terminal of the jack on the PCB.
Thus the shield conductor of the cable can be floating, and simple custom cables that connect the tip of a TS plug to a banana (and ignore the shield) will work.
If you use TRS plugs it won’t work. But TS plugs will work.
Since I this is not really documented anywhere, I can explain how the MetaModule jacks and switches work.
Each jack on the MM has Tip, Ring, and Ground. They are normal, unswitched, stereo TRS jacks.
Grounds
All the Grounds are connected together, which is connected to the power supply ground.
You will need to connect the ground of your Eurorack system (i.e. the MM) to the ground of your Serge system. This is done using one banana cable (or even I’ve seen people hack it with an alligator clip). It has nothing to do with the number or types of jacks, it’s just an electrical connection between the cases/power supplies
Tip
The Tip of each jack on the MM carries the signal. This is the same as for pretty much any module. There’s nothing special happening here.
Ring
The Ring terminal is used to sense if a cable is inserted. This is not a switch, it’s a normal ring connection of a TRS jack. For mono cables, the “Ring” portion of that cable is solid metal that attaches to the ground portion of the cable. Take a moment to visually look at a normal mono 1/8" cable side-by-side to a normal stereo TRS 1/8" cable and you will see what I mean – the spot where the Ring exists on the TRS cable is just regular ground on the TS mono cable.
OK, so what happens when you plug a mono cable into the TRS jack? The Ring terminal of the jack is shorted to ground. The cable itself provides this connection.
That’s how the MM detects if a cable is inserted: it detects when the Ring terminal of the jack is connected to ground.
Most of the time, if no cable is inserted into a jack, the MM will not send signal to the jack (or read signal from it).
So – what this means:
If using multiple systems (banana and eurorack), you must connect ground between your systems at one place (best to just do it in one place).
You don’t want to do anything special with the Tip signal. That’s just the normal signal.
The Ring signal needs to be grounded for the MM to recognize the jack as patched. Leave it floating for the MM to see it as unpatched. If you plug into the MM with TS (mono) plugs then this will happen automatically. But if you are using TRS plugs then you will need to manually ground the ring signal when you want the MM to see the jack as “patched” or “plugged”.
So, another more sophisticated way to convert MM to bananas that doesn’t use any special cables would be to make a custom format jumbler that has a TRS jack and a toggle switch for each of the MM’s jacks. Solder a wire from the Tip of each jack to a banana jack, and solder a wire from the Ring of each jack to a toggle switch (SPST) which switches to ground. The idea here is that there are always TRS cables running from the MM to the format jumbler. When you want to use a jack, flip its toggle switch closed, which will short the Ring to ground. This will tell the MM that the jack is “plugged” and it’ll start using the jack. Of course this is overkill if you have TS->banana cables!
Fantastic, thank you danngreen! Very detailed and exactly what I wanted!
If I may confirm one point, you say:
“Most of the time, if no cable is inserted into a jack, the MM will not send signal to the jack (or read signal from it).”
Does this mean there may be instances when the MM might read an input signal? Upon reading this I think for me the best solution would be a little box or module/panel of bananas and toggle switches, that way I can see what is going on and know when what is connected to where! I was leaning that way as I’m so used to it, and I like that the toggle being up or down shows the ‘state’. Cheers, Charlie
No, sorry I was being perhaps too precise. The only time when the MM firmware reads an input signal that’s not patched is during the factory hardware test. Otherwise, the MM only sends/receives signals when it detects a jack is patched.
So whether you want to use TS->banana cables or have an external patch-bay with switches is a matter of preference: both will work in 100% of music-making and patch-playing situations.