What part is that?

[SimonRichie]

On the DBA Soundwave Breakdown layout there are two lavender circles, a 5K and a 100K. What exactly are those?

[IvIark]

Trimmers. Like these
http://www.ebay.co.uk/itm/361002110547

[dbat69]

Simon - they are trimmers (small variable resistors) so you can fine tune.  The alternative is to socket resistors and keep swapping until you get the resistance you want.

[SimonRichie]

Thanks to you both!