CS9 Chorus Two Ways

[Bio77]

I've been working on this layout for awhile now.  It's a CS9 chorus adapted from Diablochris' Agua Net.  CS9 is my all-time favorite chorus and I don't have one any more (lost two to band mates over the years  ).  Thanks to everyone that helped with advice to finish this up! 

I added a blend pot from the PorkBarrel.   It also has a LAG control to adjust the clock frequency manually (similar to the SPACE control on the EQD Julia). I also added a volume trim for the output.  The idea was that you could build it stock with two knobs or go full feature.  The stock circuit sounds awesome, I love it. 

I'm still working out one last bug with the full feature version.  It has a slight volume drop when the pedal is engaged.  I'm guessing the problem is with the blend pot because there is a volume boost when it is removed in the classic version.  I tested a lot of values in the blend pot and settled on 50kB.  This gave the smoothest transition form wet to dry.  However, math wise a 100kB would be closer to the original fixed values.  If anyone has any ideas, I'd appreciate some advice, the schematic is attached.

EDIT: Replacing the BLEND pot with 250kB resolves the volume drop.  Sounds incredible!

Enclosure treatment is no-film on a Tayda powder coat for the classic and polished metal for the full feature version.  The kanjis on the Space Chorus are the google translation of "super beautiful wave device"  I'm not sure what the kanjis on the skull picture say 







Here's the schematic

[LaceSensor]

looks like its gonna be a great project once the last gremlin is resolved.
The graphics are super slick too

[gordo]

Those both look fantastic.  Even the photography is top shelf!!!

[cooder]

Amazing work, top stuff inside out! Swish to the max.

[Bio77]

Thanks fellas!  This project has been super cool and informative.  It's really motivating to learn the ins and outs of a circuit I'm such a big fan of.

[Bret608]

These are both really awesome! Let me know if you make these boards available at some point in the future.

[benny_profane]

Those look incredible! Great work. I've never played a CS9, but this has got me very curious. I think the level issue might be the result of putting the blend pot in without adjusting the surrounding resistor network. Compare the Pork Barrel schematic with and without the BLEND knob. You'll notice that the resistors in the network around the control have been scaled to account for the added resistance of the pot.

[Aleph Null]

These both look great! I love the idea of standard versus deluxe versions.

What about upping the 47k resistors that are connected to the blend pot to 68k or so (75k if you have them)? Most blend circuits that I've seen set up that way have resistors that are around 1.5x the value of the pot. You might also try keeping the proportions the same and using a 100k pot and 100k resistors. This would increase your resistance to virtual ground through the pot, which could increase output. You'd also be doubling the series resistance of the output signals, but series resistance doesn't seem to effect volume as much as resistance to ground most of the time.

[EDIT]

If the Pork Barrel is any indicator you should do the opposite of what I suggested and decrease the resistor values.

[Bio77]

Thanks everyone!

What about upping the 47k resistors that are connected to the blend pot to 68k or so (75k if you have them)?

If the Pork Barrel is any indicator you should do the opposite of what I suggested and decrease the resistor values.

My understanding is that the values around the pot are chosen so that when the pot is removed the two resistors in series are the original values; 47/47k in the Porkbarrel and 82/91k in the CS9 (I choose values close to this 86/96k).  Also, Brian recommended testing out different blend pot values to change the response of the blend.  I wasn't specifically paying attention to volume when I did this, but nothing surprising happened even with a 10k pot.

[Bio77]

BLEND pot corrected!  250kB sounds fantastic!

[benny_profane]

BLEND pot corrected!  250kB sounds fantastic!

Nice! Did you end up altering the other resistors as well?

[Bio77]

BLEND pot corrected!  250kB sounds fantastic!

Nice! Did you end up altering the other resistors as well?

Nope, just the pot value.  I still don't understand how the Blend pot value would cut the volume.  I assumed a 100k would be the right value, but on the scope still cut the output.  200-250k was a surprise, but definitely sets everything back to normal.  I'd love to hear an expert explain this 

Edit:  After playing with this for awhile, I don't think the blend knob is right. Back to the drawing board.