On many East UK preamps, the treble control includes a Pull for Bright function.

This adds extra high-frequency lift or presence without needing to overuse the main treble control.

It is especially useful when a little extra top-end detail is needed, but the exact result depends on the bass, pickups, strings and amplifier.

The spring is to keep the upper knob grounded during rotation.

Yes, since many players find it a plus to have the passive roll-off in active mode as well as passive, the system was designed that way.  

PASSIVE TONE WITH ACTIVE MODE 

+ Players who work with lots of styles in the same gig such as functions and theatre productions, for example: 

* Often set up a brighter sound with the active controls. 

* Then for more mellow pieces, leave the active controls put, and just back off the tone. 

* Fully up again for the brighter sound setting. 

The thought was that it’s more of a bonus overall, and we’ve that many pro players breathe a sigh of relief when they find the passive tone works in active and passive. And comments like – “why doesn’t everyone do it that way?” 

Our preamps were designed first and foremost  to unlock and expand the great sounds within passive pickups. They work with active pickups too.

Yes, some looseness in the treble push/pull knob is normal, particularly compared to standard single-shaft knobs. This is due to the complex mechanism required for the dual concentric rotation and the up/down motion of the bright switch within a compact 9mm pot. Rest assured, ALPS pots are known for their durability and reliability, and the looseness does not affect their functionality.