Zynth in a Rack

I have done something similar . . .

Here is where you can learn in excruciating detail a journey to enlightenment!

I use the Epic vangelis sound alike patch from Helm on pedals with an acoustic bass

cloned on top of it.

and here’s an alternative rack arrangement!

I’m nothing if not a self promoter ! :slight_smile:


Someone has got to do it :stuck_out_tongue:.

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Nice rig :+1:

Don’t you miss the 4 USB ports for connecting some midi interfaces ?
Front panel is really good.

That’s new for me, is it something like this ? :

I’m curious to know what’s the purpose of these parts, and also what means “lifting the ground”.

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AAah the great and glorious subject of balancing and what it is about…

It’s basically a telephone trick for sending a signal a looooooong way with some hope of it emerging at the far end of a wire looking a lot like what went in. Afailry important consideration if you are building a telephone network for instance!!

So lets start with a simple microphone…which is nothing more than a magnet attached to something something flimsy which is moved by the voice, inside a coil of wire.

That coil of wire has two ends and it’s the voltage between those two ends that you are wanting to pass down that long bit of wire.

Now for reasons best just accepted it’s wise to stick one of those coil ends into the ground at some point, so you end up with signal on the other end of the coil and what’s generally known as ground on the other side.
This is relevant in screened cables because the ground is a good electrical protector. (See Faraday Cage; no electrical field inside a close conductor ) and it keeps out electrical interference to a certain extent which is good.
But what about magnetic fields? They are much more insidious, and will induce nasty hum on your signal wire no matter how much shielding you put round it.

How do you buck the hum… ?

Well you use two coils one either side of your thin moving magnet and use these wires because they have a VERY useful characteristic. IF you join the adjacent ends of the two coils to gether and then join that to ground, you get two signals on the colil ends that are exactly 180 degrees out of phase with each other. i.e. when one coil is generating a maximum positive voltage, as the magnet moves back and forth, the other coil is at maximum negative voltage.

So if you send these two wires twisted together to the far away place you want to get the signal you can perform an amazing trick using the clever transformers we have here.

A transformer in this case is three coils of wire all wound onto the same lump of metal, so the magnetic field travels through all of them together.

By inverting one of the coils and connecting the two wires from our microphone. We can produce a signal on the third coil which is the anto sum of the two signals so that the two add together and produce a signal twice the size…

But even better, any passing magnetic field on the way, has made a signal on BOTH cables that this inversion and addition process will remove.

That’ why balanced is used.

I did initially use USB out from my Teensy Midi controller, you’ll see a large hole underneath the power switch on the right of the front panel.

I learned the hard way that USB Midi is limited to 16ft/5 meters, while a standard Midi cable is rated up to 50ft/15.5meters. I ended up ordering a Roland cable at 20ft/6meters.

I may end up replacing that jack, so that I could once again use USB Midi.

And yes, that is exactly the transformer I used! It may have been overkill for me to add the direct box feature, but I really wanted crystal clear sound with no hum or buzz. I intend to perform with this live at some point, and a lot of the clubs in my area have very “noisy” power setups.

@wyleu that was an excellent description on ground lifts and the purpose of balanced connectors!!

Why thank you.

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Thanks you guys.

I think, direct box has confused me as I always associated it to line inputs. But you are using it on the output side for driving a power amplifier with a balanced signal.

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There are several nice things about doing balancing with transformers…
You don’t need a power supply or active electronics.
The transformer will turn balanced into unbalanced AND unbalanced into balanced. And thirdly they handle peaks gracefully without clipping and even sound nice…fifthly they also isolate the equipment thus preventing electric shocks if something goes wrong somewhere.

Lifting the ground is simply the process of disconnecting the earth connection at the input. If your rig contains other paths from the input equipment to the receiving kit input it can be useful to easily disconnect one of the earth’s which MIGHT prevent hum loops.


I own that DAC hat:

It’s really cheap regarding the technical specs (pcm5242 chip has better specs then the pcm5122) and it provides a 4.2Vrms balanced stereo output that I didn’t use yet.

So, I imagine that these kind of transformers wouldn’t be needed in my case for sending audio output on long distances. ?

I also have an Iqaudio Dac Pro but am not able to make it work (I only find Iqaudio Dac and Iqaudio Dac+ in the menu to select and both end up with a booting error). Would you be so kind as to help me out to configure the hardware in Zynthian? What am I doing wrong?
Thanks in advance,


Yep, but you will have to provide more info:

  • screenshot of Zynthian webconf home page, to know your setup
  • output of “aplay -l” command (*) to see if your DAC is recognized
  • output of “dmesg” command (*) to see how kernel register your hardware
  • output of "systemctl status jack2 (*) command to see if jackd sound server is running. This is mandatory for Zynthian-UI to start
  • output of “cat /var/log/Xorg.0.log” command (*) to see if there’s something wrong in your display subsystem

(*) through a ssh connection or from webconf=>interface=>terminal

As a side note, In think your specific troubles deserve a specific topic.

maybe see here:

and please do not cross post same questions on old threads (that are not especially related to your specific problem).

Thanks so much ! :slight_smile:
Here’s the requested info: (Which probably pictures the kind of noob I am…)

Zynth a5

and I didn’t get anything worthy for your last request:
Zynth cat

I’ve got more from the “dmesg” but I think that I uploaded the part that is related to the sound card. If not, just let me know.
Thanks again, and sorry to everybody for the mess I made with my posts.
Kind regards,


Sorry for that… I just saw that you were talking about the specific subject on another post after sending the first message.

I had seen this… quite not sure how to do this specifically: “setting hw:IQaudIODAC in place of hw:0 in the jackd parameters”

It’s in the weconf, Hardware=>audio=> select your IQaudio sound card and check “advanced settings” box. Then modify jackd sound server options.

I’m not at home to check it exactly. But as is:

  • Alsa (the linux audio hardware low level interface) see just one sound device (aplay -l): device 0, also called [IQaudioDAC]
  • so these defaults jackd parameters in webconf looks good " -P 70 -t 2000 -s -d alsa -d hw:0 -r 44100 -p 256 -n 2 -X raw" (hw:0 is here the good parameter but the numbering of the card, eg “0”, is subject of change whenever you plug any kind of audio USB hardware for example, while hw:IQaudioDAC is stable and won’t change)
  • it’s not related to your Sound config: it’s confirmed by “systemctl status jack2” wich told that jackd2 is started and running.

So it’s maybe more display related.

What’s the output of “systemctl status zynthian” ?

also, from webconf you’ll be able to start zynthian UI in debug mode.

IT WORKED !!! IT WORKED !!! Thank you so much for your time an patience !!! I really appreciate it!!!
Kind regards,