Doepfer

Dear members,

I just wanted to inform you about the results of our tests with several
switching power supplies for A-100. The main advantages of switching power
supplies are the wide range AC input (typ. 90-240V AC, i.e. no supply
modification if you move e.g. from USA to Europe and vice versa), low price
and small shape/weight. As some customers suggested switching supplies we
ordered three types of these supplies (Meanwell, Sun Power, Condor/SL) and
installed them into standard 6U cases and a monster case.

For all tested supplies the results are very poor. The main problem is the
unsufficient load regulation that may lead to VCO tuning problems. We found
up to 200 mV (=0.2 V) voltage change of the +/-12V supplies while the load
changes. Such load changes are caused e.g. by different LED illuminations
(normally a module will consume more current if a LEDs is bright compared to
the dark state) or other effects (e.g. frequency changes of VCO/VCF). For
the linear A-100PSU2 the +/-12V changed only by about 5mV under the same
conditions. Consequently switching power supplies can be recommended only
for "non-critical" DIY applications (e.g. if only CV sources/modifiers and
audio modifiers are installed). For frames that include one or more VCOs we
recommend the A-100PSU2 or another linear supply with good load regulation
(10 mV or better).

I hope this information will help some DIYers.

Best wishes
Dieter Doepfer