Chuck D. Bones
Circuit Wizard
LoL. I'm glad you guys are deriving some benefit from my ramblings.
This Week on the Breadboard - The Engineer's Middle Finger Compressor
- Thread starter Chuck D. Bones
- Start date
To Sum it up, Do you think it is worth building or not???
Chuck D. Bones
Circuit Wizard
I'm not going to take it beyond the breadboard stage. So, in summary, no. It's given me some ideas on tweaking the Thumbsucker and also caused me to reconsider optical compressors.
fig
Village Idiot
Well, at least I don't feel as bad about not finishing it
Chuck D. Bones
Circuit Wizard
Back to the Engineer's Thumb...
This version is sounding pretty good. Some of it is easy to kludge onto the Thumbsucker board, other parts not so much.
The ATTACK control was in the wrong place. When it was inside U2A's feedback loop, it did almost nothing because U2A would just drive harder and longer to overcome the delay caused by the ATTACK control. Located outside the feedback loop, the ATTACK control can actually slow down the attack response. I wanted a solid Vref, so I used a 78L05. Vref2 is very clean, Vref1 is not quite so clean but can source more current.
This freed-up U1B, so I configured it to drive U3 differentially. Makes for lower distortion, although the difference is small. R202 biases the linearizing diodes for very low distortion. R200 & R201 balance the currents into pins 1 & 16 of U3. I consider the THRESHOLD control to be useless at best, so I replaced it with R207 & R208. C200 was added to prevent oscillation in U2A. The BRIGHT switch was replaced with a BRIGHT control. It can add up to 8dB treble boost. C201 was added to improve DC bias stability. D6 & D7 absorb some of the initial overshoot when RATIO is maxed. R206 was added to smooth out the bottom-end of the RATIO control's rotation. R210, Q200 & D200 provide an option level indicator. Use a superbright LED for D200 and adjust R210 to vary the maximum brightness.
As Valve Wizard says in his write-up, this is a compressor, not a limiter. It reduces the dynamic range but does not flatten it. The RATIO control sets how much the dynamic range is reduced by limiting the maximum amount of gain available.
This works very well as drawn. I'll see if I can simplify it a bit to make modding the Thumbsucker easier.
One more thing: C5 & C6 must be film for minimum leakage. Aluminum electro is too leaky and even tantalum is borderline.
This version is sounding pretty good. Some of it is easy to kludge onto the Thumbsucker board, other parts not so much.
The ATTACK control was in the wrong place. When it was inside U2A's feedback loop, it did almost nothing because U2A would just drive harder and longer to overcome the delay caused by the ATTACK control. Located outside the feedback loop, the ATTACK control can actually slow down the attack response. I wanted a solid Vref, so I used a 78L05. Vref2 is very clean, Vref1 is not quite so clean but can source more current.
This freed-up U1B, so I configured it to drive U3 differentially. Makes for lower distortion, although the difference is small. R202 biases the linearizing diodes for very low distortion. R200 & R201 balance the currents into pins 1 & 16 of U3. I consider the THRESHOLD control to be useless at best, so I replaced it with R207 & R208. C200 was added to prevent oscillation in U2A. The BRIGHT switch was replaced with a BRIGHT control. It can add up to 8dB treble boost. C201 was added to improve DC bias stability. D6 & D7 absorb some of the initial overshoot when RATIO is maxed. R206 was added to smooth out the bottom-end of the RATIO control's rotation. R210, Q200 & D200 provide an option level indicator. Use a superbright LED for D200 and adjust R210 to vary the maximum brightness.
As Valve Wizard says in his write-up, this is a compressor, not a limiter. It reduces the dynamic range but does not flatten it. The RATIO control sets how much the dynamic range is reduced by limiting the maximum amount of gain available.
This works very well as drawn. I'll see if I can simplify it a bit to make modding the Thumbsucker easier.
One more thing: C5 & C6 must be film for minimum leakage. Aluminum electro is too leaky and even tantalum is borderline.
Last edited:
Chuck D. Bones
Circuit Wizard
Now that I have the EMF working the way I want, I'll run another comparison with the Delegate and report back here.
