Germanium Overdrive

[dthurstan]

Hi

Here is another pedal I've built recently. The idea was I had some low gain AC128 transistors (~27 & 60 hfe) laying around, why not try and come up with a germanium overdrive. I watched a JHS video about stacking pedals and a That Pedal Show video about hitting a overdrive pedal with a rangemaster (to mimic a rangemaster going into a cranked amp) then put this together. So it's starts with a more full range rangemaster into a germanium ce amp then a lpb-1/ce amp to add volume after those first two stages. I like it although I think it might stray into distortion territory really.

[duck_arse]

too much whitespace = too much scrolling - down down down down across across across up up up up .... what? nothing here but white! down down etc etc ..... edit! resize! post!

but otherwise, well done. no pulldown resistor on the input cap?

[antonis]

Are C1 & C2 placed inside enclosure as spare parts..?? 

[dthurstan]

too much whitespace = too much scrolling - down down down down across across across up up up up .... what? nothing here but white! down down etc etc ..... edit! resize! post!

but otherwise, well done. no pulldown resistor on the input cap?

fixed. Haven't noticed any popping but would be a good idea.

[dthurstan]

Are C1 & C2 placed inside enclosure as spare parts..?? 

Yeah, meant to draw up the bipolar supply circuit for the -9v but forgot. I'll do it at some point.

[mozz]

Is C6 really needed or is it acting in series with the .1 before it? Think I'm gonna breadboard one of these and see what (how) low gainers work.

[dthurstan]

Is C6 really needed or is it acting in series with the .1 before it? Think I'm gonna breadboard one of these and see what (how) low gainers work.

You are probably right. I don't know if it's obvious but I'm a bit of a hack. I just slap bits of circuit together & give it a name.

I was surprised how good & loud low gain transistors sounded. Just bias the stages appropriately & it works.

I used a silicon stage at the end to add volume after the overdrive/distortion. That maybe distorting too, but like I say I'm a hack.

[dthurstan]

I've added the bipolar supply now.


I should probably add stuff like pulldown resistors, power filtering and protection to these schematics I'm posting.

I'm not sure with voltage multipliers (ICL7660S/MAX1044 etc) if the filtering should go before or after the IC. Since in this case you're only interested in the -9v.
Would a 1N5817 in series with the +9v mean that you get a little less out from the -9v, it does tend to be a little lower without it.

[Eb7+9]

... and, WHY did you use a charge-pump ic instead of just swapping the power supply wires ??!

[dthurstan]

... and, WHY did you use a charge-pump ic instead of just swapping the power supply wires ??!

Hi, because I wanted to use it with a common PSU.

[antonis]

BY "common", do you mean PSU feeding a daisy cain or just an ordinary PSU for individual use..??

[niektb]

I've added the bipolar supply now.


I should probably add stuff like pulldown resistors, power filtering and protection to these schematics I'm posting.

I'm not sure with voltage multipliers (ICL7660S/MAX1044 etc) if the filtering should go before or after the IC. Since in this case you're only interested in the -9v.
Would a 1N5817 in series with the +9v mean that you get a little less out from the -9v, it does tend to be a little lower without it.

I think you may have inversed the polarity on C2

[Ben N]

Kewl! I'd like to give this a go, and possibly try NPN and/or different power options.

[duck_arse]

C4 is upside down for a positive ground circuit.

[antonis]

C4 is upside down for a positive ground circuit.

Not for an down under area..

[dthurstan]

Me and my schematics 

BY "common", do you mean PSU feeding a daisy cain or just an ordinary PSU for individual use..??

Yeah, daisy chaining effect.

[antonis]

You and your schematics   

[dthurstan]

fixed it

[bushidov]

Hi D Thurston,

I liked the design, so I quickly threw it together in EAGLE and made some gerbers and a BOM
http://www.cyclone-radio.com/pedal/dthurstan_drive.zip

Schematic


Top PCB


Bottom PCB


I did add an input anti-pop resistor, a reverse polarity diode, and a bulk cap, just for kicks.

Should easily fit into a 1590B enclosure.

[dthurstan]

Hi D Thurston,

I liked the design, so I quickly threw it together in EAGLE and made some gerbers and a BOM
http://www.cyclone-radio.com/pedal/dthurstan_drive.zip

Schematic


Top PCB


Bottom PCB


I did add an input anti-pop resistor, a reverse polarity diode, and a bulk cap, just for kicks.

Should easily fit into a 1590B enclosure.

Nice one bushidov. Good work. Here is the vero layout if anyone is interested.

I did it that way because I had some board ends I wanted to use up.