I found this description on an old DAT-HEADS digest:
"Denecke AD-20 modifications. Date: Mon, 2 Sep 2002 02:40:13 -0400 I'm starting to get mail in response to my for sale post. Sounds like a few Denecke AD20 users may be interested in increasing the size of their knobs. Sounds like the penis enlargement spam email... anyway... back on topic... Here's how I got READABLE gains on my AD20 that I could also easily manipulate. At your hardware store they usually have a bunch of drawers or boxes filled with small parts. Cotter pins, rings, special washers. I bought two knurled knobs that were made to press fit onto the heads of cap screws. They are used to make your own "finger tight" fasteners from cap screws. If you dont know... a cap screw has a cylindrical head that is usually knurled on the outside and is used with an "allen wrench", "hex key" tool. The knobs on the AD20 look just like the heads of cap screws, minus the hex socket. Since cap screws have a hex socket, these knobs have a plug that fits into the hole. You need to remove the plug, using the tool of your choice :-). The knob will now slide onto the AD20 mini gain knobs. You need to glue them on. The knobs are about 1/2" dia. Maybe 5/8". I printed gain markings "0 thru 9" and "hash marks" onto some adhesive backed labels using AutoCAD. Turned the gains all the way down.. and applied the adhesive labels aligned to 0. Remember that the gains dont turn a full 360. Using AutoCAD, it was relatively easy to configure the spacing. Now I have easily read gain pots on My AD20. Sounds like a lot of work. It was really quite easy... takes a long time to explain."
I'm interested in this mod too...are your knobs just like the ones of the radioshack link in this thread Church?