the trimpots on the Tremulus panneur

[kissack101]

Hey,

Has anyone here built the Tremulus Panneur from 4ms? I posted this message on the commonsound forum but thought i'd repost it here too (i'm in the studio friday and i'd love to have this ready)

My brother got me a kit from 4ms for the stereo tremulus panneur for christmas and i'm in the middle of putting it together. Firstly, I made a PCB using PnP instead of the wooden board they give you with the kit. However, when I did so, I erased the parts marked 'trimpot' on the layout (the grey rectangles on the right-hand side here: http://commonsound.org/panneur/panneurboard.pdf) as I didn't think they should be on the pcb.

How are you supposed to mount the trimpots? What should they be connected to? I've been through the commonsound forum and this one but nothing seems to be conclusive (are they a gain pot?).

Any help would be appreciated.

Adam.

[RickL]

I believe the trimpots are mounted on the back of the board (i.e. on the trace side).

[kissack101]

So between the 0.1uF capacitor and the Cds? If that's the case, why isn't this incorporated into the pcb layout? Oh well, I suppose I could mount the pots to the side of the PCB and use small lenghs of wire as jumpers. In terms of the actual trim pot, does orientation matter? It only uses two legs according to http://commonsound.org/panneur/panneurboard.pdf, I assume as long as I use the short leg and one of the long legs i'll get the right result?

Many thanks

Adam

[RickL]

Yes, but it also forms a variable resistor between the inverting input and the output of each of the opamps. I'm pretty sure it sets the gain of the opamp. It might be worth using panel mount mount pots in place of the trim pots, in fact I think I may have done that on mine. You do use the short leg (wiper) and one of the long legs or the wiper and one of the end lugs if you choose to use panel mount pots.

Having the trim pots on the back of the board may just be a design quirk, or they may be placed there so they can be adjusted when the board is mounted in an enclosure (with the back of the board facing out).

Check out the schematic at the same site to see how the trims function in the circuit.