[sdiy] Ultrarough draft of my hot-rodding of the Music Easel ring mod

[Dave Manley]

Aaron Lanterman wrote:
> Yes, I know my Eagle schematic looks like crap. Yes, I plan to clean 
> it up. :)
>
> http://users.ece.gatech.edu/~lanterma/easelrm_draft.png
>
Hi Aaron,

Comparing your schematic to the original, in addition to Grant's 
comments, I see the following differences:

1. Perhaps obvious: Buchla always uses two grounds - one labeled N, for 
the Vactrol's LED return current, and a second, labeled Q, for the 
signal path.   I assume these labels stand for "noisy" and "quiet".  You 
may have already been planning to do something with the grounds, but it 
isn't documented on the schematics.

2. The feedback path that has the VT5 and VT6 LEDs is missing a resistor 
33K resistor (R33 in the original).

3. Not sure about this one: A common resistor, R11, is used connected to 
the + input of IC1B, IC2B, and IC2A.  R31 is used in a similar manner on 
IC3A, IC3B and IC4A.  I don't think you want to do this as it becomes a 
summing point for the bias/offset currents of the connected opamps.  
Don't you really want separate resistors for all of these?  I defer to 
the analog masters on sdiy :-)

The Easel's a cool thing to browse through, I look forward to your 
future posts on the subject.

-Dave