> I have Analogue Solutions ATT4 passive attenuator.
> http://www.users.globalnet.co.uk/~concuss/concussor/att4.htm
>
> When I route for example the clock signal from A-154 or logic high
> output from A-166 (10V) through the ATT4, I get only 50% output (5V),
> when the attenuator knob is in full clockwise position. However,
> with most other sources (including other 10V logic signals) I get
> 100% output as expected.
>
> I found this, when testing, how my modules would respond to softer gate
> signals. I wonder, what is the explanation
>
> Best regards
> Jari Jokinen

There's a simple reason and that's the load of the passive attenuator.

An example. Most of the digital outputs of the A-100 work like this: a
transistor switch at the output with e.g. a 10k pull-up resistor connected
to +12V. The transistor switches to GND in the low state (i.e. the output is
switched to GND, a bit like Moog's S-trig) and opens in the high state. In
the high state the output is connected to +12V via the 10k pull-up resistor.
If the load is about 10k too one obtains only 50% level as you have a 1:1
voltage divider (10k pull-up, 10k load).

If the output is an analog voltage (in the majotity of cases the output of
an operational amplifier) things are different as the typical output
resistance is in the 1k range. In this case a 10k load lowers the level by
only about 10%.

Best wishes
Dieter Doepfer