Quick Tip: Differences in Eurorack Modules

When you have multiple modules of the same brand and type , you might sometimes experience small differences between those Eurorack modules.
Sometimes oscillators are tuned differently and you can't get them to match.
One may sound lower than the other with each's controls identical, yet they sound different..

This is often not something to worry about.

Four A-110 VCOs that look the same,
all sounding (slightly) different.

Although most modules are thoroughly tested, some batches may indeed sound a little different due to (internal) trim-pot settings, differences due to tolerances of the electronic parts, etc...

If you want to compare your modules, it is always smart to check the production date/ batch number on the test label and/or on the PCB (version nr) first.
Usually this can be found at the inner side of the front panel.

If the numbers match, and one of your modules does sound different than the other one, you might check out the trimming pots on the backside of the module on the PCB.
In most cases this can be easily fixed with a small screwdriver once you located the right potentiometer (often printed on the PCB or can be found in a manual).

Sometimes it just has to do with other components.
During the production-years of a module the values of all kinds of parts of your module may have been changed a bit (for example R77, R86, R88).
These differences can sometimes be audible, sometimes only to the trained ear...

Especially the specifications of a main circuit like the 74HC4046 (Used in the Phase Locked Loop - A-196 PLL module) may differ for different manufacturers (even different batches from the same manufacturer) of this circuit.
Because the PLL module is not a precision module like a VCO there are no trimming potentiometers available to balance such tolerances.
You'll just have to live with that...

Sources: Doepfer website and Doepfer A-100 Yahoo Usergoup

How NOT to Modify

The rail is still visible through the
new hole i drilled

Okay... sometimes you have to learn the hard way.

I made a slight mistake while drilling a new hole in a front panel for my latest DIY-project.
(blogpost will follow soon)

Although i knew there was not a lot space where i had to drill, i did not calculate that the rail would still be visible.

Hardly visible, but i had to scrape almost
one mm. off the module's PCB

I am glad that i didn't have to put a mini jack connector but only a switch there, but that didn't even fit here.
Okay, maybe I should have drilled a smaller hole in the first place.

My bad... but still very annoying.
On the other side of the hole there's the module's PCB, so i couldn't put the switch higher without also modifying the PCB board.

Luckily i could solve the problem with an extra large ring.
It has not trned out to be my most successful modification.
More info on what i was working on will follow later this week.

Finished switch, with extra large ring

Sadly i also damaged the front-panel a little bit (bottom left and under the D from Doepfer)

I should be more careful next time, and take a little bit more time for my modifications... 

Make a plan first... and work step-by-step.

That would spare me a lot of trouble.