What to build?

[idsnowdog]

The vaporizer this board came out of died this morning and that noisy SOB won't be missed. So what should I build from its ashes? If the turns ratio on the transformers are correct I could build an Octavia or Green Ringer. The transistors 2N3804, 2SC1815, and A1018 are pretty general purpose. The diodes are 1N4148s and 1N4001s so they can be used for power filtering and clipping.

 

[idsnowdog]

What to build was sitting under my nose until I went looking for circuits that use the 2SC1815 and 2SA1015 today. Before the vaporizer died I was considering building a Harmonic Percolator since I now have the Germanium transistors needed. I was just waiting to find a broken Mr. Coffee maker so I could use the logo as a pun.

However, I found this schematic for a push/pull amplifier that uses the 2SC1815 and 2SA1015. The Harmonic Percolator also uses a PNP and NPN transistor in a push/pull configuration. If I socket the transistors I can switch to the 2N3565 and 2N404 of the original Harmonic Percolator if the 2SC1815 and 2SA1015 don't work out. I can call it the Harmonic Vaporizer to preserve the pun value.

 

[idsnowdog]

I completed the Harmonic Vaporizer wiring this morning. I haven't put it in a case yet. I would like to find a white metal case to go with the knobs I have. I was able to use a number of parts I salvaged from the vaporizer. I didn't use the transistors I salvaged because they had too much power and I would have had to redesign the circuit. So I used the 2N404 and 2N3565 that the original Harmonic Percolator uses instead. The original clipping circuit robbed too much output so I designed a new clipping circuit that has little output loss and sounds much better. The switch chooses between a GE or SI diode in parallel with a MOSFET for asymmetric clipping. Changes are in red. What a gorgeous harmonically rich growl!

 

[Lucius Paisley]

A snowman.

 

[Chistopher]

Man I love the Harmonic Percolator. How big of a change are you noticing when switching between diodes? When I tried it i didn't get much difference in sound.

Also I think you should try a comparator fuzz once you get this one down.

 

[idsnowdog]

The circuit has plenty of distortion without clipping diodes. I tried a lot of different diode clipping types but they all lowered output too much. The MOSFET has a really nice soft warm clipping and the SPDT switch allows me to choose a GE or SI diode in parallel. This configuration has the least volume loss. The SI is bright with a sharp attack while the GE is smoother and warbly as the note decays. The pot allows me to dial in the amount of clipping and the bypass capacitor emphasizes upper frequencies. The only idiosyncrasy with this setup is it gets brighter the more clipping you dial in. Which is the opposite of most other circuits.

Before Christmas I bought some comparators and sockets cheap at a surplus store. I was thinking about building this one https://www.parasitstudio.se/building-blog/lm311-comparator-fuzz . But after this morning's aggravation I swore off stripboard builds and deleted all of the schematics I had that used them. I have had more failures than successes with stripboard. Turretboard is a lot easier for me to work with.