As for voltage, I think that you will find the actual domestic supply in Germany is closer to 220V. Some while back, it was decided that countries across the EU should pretend to harmonise supply voltages; so they hit upon the idea of using a declared voltage of 230V. The catch is that in the formerly 220V countries the adopted tolerance was 230V -10% +6%, whereas here in the UK (formerly a nominal 240V) the new standard is 230V -6% +10%. But the supply voltages did not actually change (hence the jiggery-pokery with tolerances), for the simple reason that such a change would entail an enormous cost in re-equipping the distribution infrastructure (new transformers at all the local substations), not to mention problems with some (mainly industrial) machines which are designed to run within narrower voltage tolerances.
That is not to say that your supply will be spot on 220V - it will vary according to the state of your local distribution grid, and with the time of day (due to fluctuations in total load). I find anything between about 238V and 247V here in south-west England.
This is not a problem for most new domestic electric appliances - those made for the EU market must be able to work over the range 230V ±10%. If I buy a Euro-standard electric kettle in my local Lidl, it will come to the boil faster here than it would in Germany (incidentally affording us a marginal saving in heat loss, thus saving the planet or some such nonsense). Most modern electronic gear working with an internal low voltage from a regulated step-down unit will automatically adapt to a much broader mains supply voltage range. Older kit, which just relies on a fixed transformer winding turns ratio for its internal voltages, is often equipped with mains voltage selectors, jumpers, or requires some soldering to adjust to the local supply voltage. If your tranny is marked 220V, then you are probably OK. But if you are worried, I would first suggest putting a voltmeter on your wall socket at the times when you typically play the Wurli, in order to see what your actual supply voltage is.
Where supply voltage can be a problem is exemplified by the Twin Reverb amp I use with my Fender Rhodes. This twin is a reissue (i.e. modern), and labelled 230V for the European (including UK) market. Now I know that the power transformer has multiple taps on the primary windings to cater for 220V, 240V etc., which suggests that this order of internal voltage accuracy is regarded as important; but the only schematic I can get for it is some years out of date, so I cannot check/adjust the primary connections to suit my 240V supply. In theory, if I am putting 240V across the 230V taps, the B+ and all the related plate voltages are going to be 4.3% too high. Happily, my grid voltages will also be correspondingly more negative, affording some correction, so the set-up is probably near enough to avoid red-plating the output valves (tubes); but goodness knows how Fender set the bias at the factory. Do they anyway use for this a bench supply which gives exactly 230V anyway, or is it 230V ±lots, close enough for those weird folk across the Atlantic?
The moral of this story - take nothing for granted.
