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QTY PART-REFS VALUE CODE --- --------- ----- ---- Resistors --------- 8 R1,R5-R7,R13,R16, 30.1k R25,R27 2 R2,R10 60.4k 2 R3,R11 1M ***Possible Mod*** 8 R4,R8,R12,R14,R31, 100R R35-R37 15 R9,R15,R17-R22,R26, 10k R28-R30,R32-R34 1 R23 14k 1 R24 11.5k Capacitors ---------- 4 C1,C3,C5,C8 330pF 2 C2,C6 22uF *AC Coupling caps (jumper for DC) 6 C4,C7,C9-C12 100pF Integrated Circuits ------------------- 2 U1,U3 LM13700 3 U2,U4,U6 TL072 1 U5 LT1013 Transistors ----------- 2 Q1,Q2 2N3906 Diodes ------ 3 D1-D3 1N4148 Miscellaneous ------------- 3 BIAS,VB1,VB2 100k ***R3 and R11 can be changed to lower values to impact the overall bias of the VCAs. 1M was chosen as a trimming value. VB1 and VB2 will only impact the bias slightly. Low values (like 10K, will shift the signal all the way to one side of DC, but may introduce some changes/distortion to the waveform.) More extreme (lower) values may be more interesting when these controls are brought to the panel. 1M is perfect for trimming in cases where VB1 and VB2 will be trimpots internal to the module.***
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12V Modifications: For 12V operation, please change the following resistors: R23 from 14K to 11K R25 and R27 from 30.1K to 24.3K R24 from 11.5K to 12.1K The new range of the CV section should be 0V to -11V, with a crossover point of around -5.5V.
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Notes: One thing I would like to call attention to after thinking about it a bit. VB1 and VB2 are bias pots. Not input attenuators. I'm not sure that this has been clearly called out up until now. Clarke's panels leave these controls open to however people would like to use them, which is cool. One could easily wire the pots up as input attenuators for the VCAs, and use trim-pots internally for VB1 and VB2. Or, VB1 and VB2 can be brought to the panel, and R3 and R11 can be tweaked to taste for biasing the signal around DC. I'm going to set these resistors to an extreme value, and post some results in this thread. (just to give an idea of what these will do. I've seen some fairly interesting results in the simulations that I ran, and hope they translate to interesting audio. I'll post notes on this shortly. One more note. The output resistors can be bumped up to whatever your preference is for output protection. The op amps only source around 20ma of current, so 100R should be ok in most cases (unless you connect it to a power rail or something. :deadbanana: There's no reason not to stick 1K resistors there to be on the safe side.
So here is the requested crossfader thread.
Since it will have different uses, (as a part of the dual 291 configuration, stand-alone, etc.) I made the thread title very generic.
I'm calling it the FadeX for my own purposes, but also like the name that Clarke chose for his panels. It kind of falls in line with some of the other panels out there. So call it whatever you like, but here's where we can discuss it.
The test boards will be here in a few days. Once I get one tested, I'll toss up the BOM, start making some build notes, and put up other materials as needed.
One issue that has come up, is that I'm trying to standardize my board sizes and mounting hole spacing. I'm trying to make all of my boards 3" wide, by 1, 1.5, 2, 3, and 3.5 tall. I want them all to use 2700 thousandths hole spacing (2.7") The 291 boards I believe are either 2750th" or 2800th" so this creates a bit of a mounting issue. One approach that I've been discussing with Clarke, is to do one side in 2700, and the other in 2800 or whatever the 291 turns out to be. (I'll be checking this later.) I'm not sure that this will work as it might go beyond the board edge though, so that's one more item I have to figure out before the final production run gets ordered.
If anyone has any novel mounting ideas that would allow us to match these up in a usable way with the 291s, but allow it to keep the new, normalized spacing, I'd love to hear them.