Two designs, one BOM...

[phasetrans]

Sort of...

I'm experimenting with having SMD boards pick and placed in Shenzhen, and I thought it would be fun to make a couple of different designs using the same group of parts to get a bit more of a price break on the components. LTspice sim schematics are below.

Note that "D360" is actually a double PIN diode part from Infineon, the BAR-64-04:
https://www.mouser.com/ProductDetail/Infineon-Technologies/BAR-64-04-E6327?qs=mzcOS1kGbgdpNkjbG0xQzA%3D%3D





I'll get these back after CNY, and presuming that I didn't make any mistakes on either of them, I will do some sound clips, BOM, and gerbers.

[antonis]

Can't figure out the use of input clipping stage of 6db gain..
Could you plz elaborate..??

[phasetrans]

Can't figure out the use of input clipping stage of 6db gain..
Could you plz elaborate..??

This is something I've wanted to try for a while, but I don't really think of it as a clipper:
1. Pull the diode out of the feedback loop, and you have a 6dB shelving filter. Mid boost / bass cut, whatever way you prefer to view
2. From pp. 4 of the BAR64 datasheet, the dynamic impedance at Vf of 0.5V is about 25kOhms at 25C
3. So, if we plug the dynamic impedance in parallel with the 15k, we get gain of about 4.2dB at 0.5V input, rather than the full 6dB
4. The same math gives a gain of 0.4dB at 0.7V input level
5. So, as the input level comes up, the mid boost goes down.
6. They'll be some minor soft clipping artifacts, but those will get swamped by the intentional clipping farther upstream
7. Asymmetry of the duty cycle above the diode threshold will also drag the DC point of C2 around a bit.

Hopefully my way of thinking about it makes sense (and is correct ).

[phasetrans]

Got cold feet and changed the input stages, did some component golfing, and tried to make sure the inverting opamps will always be stable:

[antonis]

tried to make sure the inverting opamps will always be stable:

Can't see any obvious reason for instability (other than the absence of LPF caps inside NFB loop, perhaps..), but you can "easily" verify it..
https://en.wikipedia.org/wiki/Nyquist_stability_criterion

[StephenGiles]

CNY??? I'm guessing Crosby Nash & Young?