Hi Roel

> Fascinating to hear that when you reach the highest position
> on the input of the 138 mixer, a small feedback resistor comes
> to action on the new models, compared to the older ones, which
> didn't amply!

This is a misunderstanding.

An signal transfering operational amplifier circuit _always_ uses
feedbackloop.

+-RRRR-<<-+
| | <............This is the Feedbackloop.
| |\ |
sig.in >>--RRRR---+-| \ |
| \ |
| +>>-+-->>---Out
| /
+-| /
| |/
|
|
Ground


RRRR means Resistor

>> shows the direction of the signal flow

As long as the both resistors have the same value there happens no
amplification. If the resistor in the feedbackloop has a larger value than
the input resistor, then the circuit will amplify the signal.

> When I understand the lin. versus exp. bit, and I extrapolate that
> to the lin and exp. mixer,

Lin / exp for the mixers only means, that the potentiometer have
logarithmic or linear characteristics. You simply can make on eout of the
other if you exchange the pots.

> am I right to say that one type of mixer
> is better to use for audio signals and the other for cv

That is right.


Florian