Macheen: switch to SHO?

[rowland1]

Hi. I read in the project document that the Macheen has an SHO at the front of the circuit. When I compare the schematics (Macheen vs. Slambox) I can see the core of the SHO at the front of the Macheen schem. But it is not exact, as the output from Q1 goes thru R5 and C3 into Q2/Q3.

Is it possible to insert a switch somewhere in that area (R5/C3) to redirect the output bypassing the rest of the circuit? That way you could switch between SHO and Macheen. I am guessing it would be fairly easy - but am still new to this stuff.

Thanks for any comments or help!!

[B_of_H]

there is a sho section to start and then a 2nd later.

the differences:

there is a 2m2 pull down on the macheen that isn't on the sho. 

there is a 22k resistor in series with the output cap and the value of the output cap is 10u on the sho and 1u on the macheen. 

there is also a 47k to ground prior to output on the sho that isn't on the macheen.

I'm not sure how rational this mod is because the SHO is so low parts count wise anyway that it just seems like more hassle than it's worth.

I guess you could try taking the signal off c3 with a 47k to ground and see how it sounds? 

[rowland1]

Thanks Alot!! I'll give that a try.

[stecykmi]

One other thing to watch out for, however, is the polarized nature of C3. If you're using C3 as the output of the boost, it's positive side will be at 0 VDC while it's negative side will be at some small positive VDC (maybe 1.5V as a guess). This is bad, so you'd likely have to include another outboard cap to rectify this (ie, tap it from the R5/C3 node).

[rowland1]

One other thing to watch out for, however, is the polarized nature of C3. If you're using C3 as the output of the boost, it's positive side will be at 0 VDC while it's negative side will be at some small positive VDC (maybe 1.5V as a guess). This is bad, so you'd likely have to include another outboard cap to rectify this (ie, tap it from the R5/C3 node).

Nice catch! I never would have caught that. I think I agree B_of_H, it is probably easier to just build a separate SHO. I have already built one so no big reason to insert a switch into the Macheen. Thanks so much for the helps!