I simply built some inverters following the schematic posted here in the "files" section. (a .txt file called s-trig to v-trig.) 

I just followed instructions from  gregory zifcak on this forum :

> > 
> > here is the trigger out mod that i did:
> > 
> > 1. look at the schematic in the files section called "s-trig to
> > v-trig" or something like that.
> > 
> > 2. in place of the 9v battery, connect to a +5v point on the circuit
> > board. this should be findable with the 707 schematic.
> > 
> > 3. find the chips on the 707 schematic labeled "trigger A" and
> > "trigger B."
> > 
> > 4. connect those trigger pins for the sounds you want to have the
> > trigger outs (i only did six) to the s-trig input located on the
> > schematic.
> > 
> > 5. output of the trigger schematic to a jack of your choice.

I used a little strip board and bc 549 transistor

I've got the tr 505 too, and experiment a lot with it.I trig diy drums circuit and little vca with success. the problem is that the sound disappear when you tap its trig signal.

> >