Had me more of a think on this...

> if the mod is a resistor and a capacitor in the a155
> control board,then this is the mod i was telling you
> about...it's the mod for letting you clock the a155
> from an imperfect clock pulse(with not sharp

...and I don't think this can be the reason (the clock pulse goes
through 2 gates anyway, which should sharpen any sluggish pulse up
plenty!). But I do now believe _this_ must be the reason:

> edges).also,with this mod ,you can step manualy the
> sequencer from the tiny step button more
> properly(without almost jumping
> steps...).

Without the capacitor contact bounce on pushing the clock button
could well cause it to skip several steps unintentionally. And I
certainly believe this...

> but,also,this mod stops the a155 from
> running in high audio frequencies!even if you clock
> the a155 from an a110 you will notice that,the a155
> can't run above a certain speed limit(which is rather
> low!)all these are valid only if we're talking about
> the same mod,though....
> by the way,i removed this mod from two of my a155's
> because i want them to be graphic vco's too!

...so if you don't care about the skipping several steps problem,
snipping through one of the wires to break the link formed by the cap
& res will let it run at higher speeds. Details for those unsure what
we're talking about: the 'control board' is small on the right hand
side of the module, marked 'A-155-4' on underside ('A-155 board 4' on
top); if you have the mod, on the solderside you'll find a capacitor
(marked '104') and a 1k resistor (brown, black, red, gold) soldered
together and bridging two pins of the 4011 IC; cutting or desoldering
either end of them or where they join will do it!

Tim