Doepfer

Hi TD,

> I'm curious about whether the Frequency Shifter overload LED is 
meant to warn against the possiblity of distortion or is awarning 
light 
> that indicates potental damage to the circuit. It seems quite easy 
to overload and if one doesn't ride the input signal to that point, 
the 
> output isn't really that loud.  -anyone have any insight on this?

Looking at the schematic, and from memory (I studied this in-depth a 
few months back), it looks like the LED is there to allow the circuit 
to be operated at an optimum level. If the LED is on, the internal 
levels may become too high for the multiplication of the internal 
oscillator and the input signal to work correctly (i.e. likely 
to 'distort', whatever that might mean in this context!). If too low, 
then presumably one is likely to suffer unecessarily from any 'bleed 
through' of the internal oscillator. After the initial attenuator on 
the input, there is a x10 amplifier, which is why it is relatively 
easy to light the LED. However, as measured on my A126, inputting the 
sine shape from an A110, with the LED not quite lit, the output is 
about +/- 4V, which sounds plenty 'loud' enough to me! Increasing the 
attenuator so the LED comes on, and I can hear a distinct change in 
timbre, which suggests some kind of clipping or whatever. One would 
hope that operating it with the LED continually lit wouldn't give 
rise to any damage, but in this region the circuit is unlikely to 
work 'as advertised'.

Thus I would suggest two things: operating it with the LED not quite 
lit; and be guided by your ears (unless anyone else has anything to 
offer...)

Tim