With the adjusters on the back what is the correct way to turn the trim pots to stop the bleeding of sound in a VCF. The inverted state works well... also what is a recommended screwdriver to use for this part of calibration that wasn't done so I botched the back so its going to have to be repaired. Maybe the direction and tool should be as a note in the manual.
Hello, all.
I never got around to building my Knead EQ/Mixer, and did not save the BOM for while it was still available. Does anyone have a copy of it? If you have the expander as well, that would be lovely.
thanks!
jf
Hey Jeremy,
That’s quite an old one, so some of the links and components may be outdated, discontinued, or no longer in stock.
Cheers,
Stefan
Hi, I'm busy assembling all the parts for a Cause and Effect S&H module and the BOM calls for an SMD LM398 amp with 8 pins. Unfortunately the correct component doesn't seem to be available in the UK. I can only get the through hole version with long pins.
Does anyone know of a source for these components or if it's possible to use the long pin version at all?
Rich.
Hi Rich,
the part you need is LF398S8#PBF, the 8-pin SOIC version. Farnell UK, RS Components and DigiKey UK all list this part, although current stock can change.
Best,
Stefan
hey there, I`ve built a Duck, checked for cold joints, right orientated components and so on. But no matter what I try I cannot get audio out of this module.. the yellow led is constently on. red led works with gates and settings.
Any idea, what do to check first?
Hey Nys, I would start with the VCA/main board:
Reflow suspicious solder joints, start with the ICs.
Check the board connections with the headers
Check the supply rails: +12 V / -12 V at TL074 and LM13700 (U2), and the +10 V reference around LM4040 (IC6) and U1 (Pin 1).
With no audio connected, measure VCA_OUT DC (lower pad of R31) voltage. It should be close to 0 V. If it is strongly positive, negative or near a rail, check U1B, R31, R32 and LM13700 (U2), especialy for solder bridges or bad joints.
Apply a gate and measure CV_TO_VCA (left pad of R15). The voltage should clearly change with the envelope. If it does, continue through U1C → Q2 → LM13700 pin 1. This is the VCA control-current path.
The constant yellow LED is especially interesting because its driver monitors VCA_OUT. So I would measure the DC voltage at VCA_OUT first. If you send me that voltage plus the voltage at CV_TO_VCA with and without a gate, we can narrow it down quickly. Thanks,
Stefan
Hey Anthony, There is no fixed turning direction. It depends on the current offset. The goal is to get the output as close to 0V as possible when the envelope is inactive.
Use a multimeter to measure the OUT voltage and carefully turn the corresponding trimmer in whichever direction brings it closer to 0V.
I recommend a small, non-conductive flat-head trimmer screwdriver to avoid damaging the trimmer or PCB. Cheers,
Stefan