Passive Euro Level to Line Converter Module Advice


#1

What’s the simplest way to passively attenuate Euro audio level to line level?

a|x


#2

Signal => attenuator/mixer => turn down the volume => run into a line level mixer


#3

I want to make a passive level converter module, with 8x minijack on the front panel, and 8x 1/4" sockets on the back, so I can permanently connect it to my audio interface without having to patch in 1/4" cables at the front. I can turn down the gain on the interface, and use it as a mixer, as long as the signal isn’t distorting on the way in.

a|x


#4

This module looks to just have three fixed resistors and a 2-position jumper per channel, and the description says it offers /3 or /10 attenuation.

I can’t see what values the resistors are though, and I’m not sure how to calculate the values.

a|x


#5

Oh, I get it now. Correct me if I am wrong, but you just want a voltage divider.
The Ladik module has x/3 and x/10 as the options. I’ve seen a lot of talk about Ladik modules recently.


#6

@toneburst I think I suggested this to you before and it is a bit overkill. But it works. Link


#7

It’s kind of dumb to give precise attenuation ratios (or to try to design precise attenuation ratios) in a passive device! The actual attenuation ratio will depend on the output impedance of the module, and input impedance of the mixer/audio interface. That’s why passive devices are such a pain…

Most modules have R_out = 1k, but some have R_out = 0k and use a different output protection scheme (or no output protection at all).

As for R_in, it’s between 5k and 15k for most audio interface, except when they have the “HIGH-Z” switch, in which case it can be made to drop down to at least several hundred k.

So I’d go with something like 2k and 1k to ground for small attenuation

You get the following attenuation factors:

R_out = 0, R_in = 5k : 0.29
R_out = 0, R_in = 15k : 0.32
R_out = 1k, R_in = 5k : 0.21
R_out = 1k, R_in = 15k : 0.24

And for larger attenuation, 8.2k and 1k to ground.

If this thing is meant to be used with an audio interface with high-Z inputs, I would use 20/10 and 100/10.


#8

@pichenettes thanks for the detailed explanation. I’m kinda happy it’s not as simple as I thought it might be. Makes me feel a bit less stupid… :wink:

The intention is that the outputs on the back will be connected to my MOTU 828Mk.3 line-level inputs, so I can record straight into my computer, or use the interface standalone as a mixer and headphone amp.

a|


#9

@sammy123 I was considering one of those, but my plans have changed since then.

I’m mounting my Euro modules in a 19" enclosure, with my rack mount audio interface below them. Since the i/o of the interface is on the back it makes sense to have them connected at the back, too. With the NW2S::IO, I’d need to get the fat multicore connector from the front to the back of the rack, which would require leaving a gap of some sort (I plan to fill the rack completely, so that’s not going to work), or passing the multicore around the side, or over the top of the enclosure, which would look a bit silly.

I also like the idea of not having to bother with minijack > 1/4" converter cables at the front, and keeping the front of the rack clear for patching. It’s quite an obscure usage-case, I guess :wink:

a|x


#10

You could consider this one as well. It will certainly look cool :slight_smile:
Tsyklon Labs - CORE


#11

@pichenettes if I were to fine-tune the resistor values to my particular interface, would a Braids in FOLD mode, with TIMBRE and COLOR at minimum values (to produce a sine wave) provide a useful average reference level for a Euro module, do you think?

a|x


#12

@rumpelfilter does look cool. On the other hand, I’m thinking ‘why pay $220 for something I could do with 2 resistors…?’ :wink:

a|x


#13

https://www.modulargrid.net/e/racks/view/196421


#14

@rumpelfilter: this one is cool, a balanced output from am modular is what i would be killing for…
Unfortunaltely one always needs more than one !


#15

@nightworxx the balanced version of the NW2S::IO has 8 ins and 8 outs.

a|x


#16

@toneburst did you see Scott now has cables for routing from the back of the module?


#17

@sammer123 ah, I remember seeing that picture (showing the rear cables) before, now I think about it.

It would work, but it’s messy, and unnecessarily complicated, I think, so be honest.

Also, the extra HP of the D-Sub sockets on the side (which I wouldn’t be using) would annoy me…

a|x


#18

I made up this little module with a Scheafer alu panel.

This one is completely passive (no attenuation), and is connected to the outputs of my interface. I intend to use it with Silent Way, and make or buy an amplifier module to boost audio to modular levels, if I want to process it through my FX modules.

The plan is to make another version, with resistors in the inline 1/4 jack sockets, for passive attenuation of modular level audio to line level for connection to the MOTU 828 inputs.

That should cover my i/o needs for the moment.

In the future, I might make a version of the output module with a PCB, and jumper-selectable attenuation, like the Ladik module, but with outputs on flying leads on the back, as above. I can also add holes to the PCB to attach some kind of strain-relief for the flying leads, as 8 inline sockets, 8 jack plugs and the cabling between the interface and the module weigh quite a lot.

a|x


#19

Finally actually got around to testing signal out of my modular straight into the line inputs of my audio interface (MOTU 828 Mk.3).

I tried dry outputs straight out of several different modules- Braids, Radio Music, Tides, and also Braids through my Doepfer Wasp Filter.

The result in all cases: it looks like the 828 can cope with modular signal levels without requiring attenuation! I can’t hear any obvious distortion, and there are no clipping warnings in the software mixer. I haven’t tried recording and analysing waveforms, yet, but it sounds fine to me.

Should I try a little passive attenuation, anyway? I was under the impression that modular signal levels were way above standard line-level. Maybe that’s not the case, afterall.

a|x


#20

I just found out the same. I had a Fast Track Ultra, and I used to send it signal through Shades with the knob at 5%. Now I have a Fast Track Ultra 8R, the 8R is a 1U rack variant. It seems that the internal hardware is also a lot different because it can just take eurorack-level input signal. I tried several modules at full output and the signal comes through nicely. The clip leds in front of the 8R don’t light up and ALSA and JACK (linux audio) show normal levels.

So yes, looks like attenuation isn’t always required :slight_smile: