JHS Pedals Overdrive Preamp

phi1 said:
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Completely different clipping arrangement seems like an overstatement for ge vs silicon diodes.
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I'll give him a tad bit of wiggle room with that statement. Most guitarists aren't electrical engineers and don't know how to build pedals. Josh definitely speaks to them in his marketing. So, two different sets of diodes to him is a "completely different clipping arrangement". Most guitarists understand what "clipping" is...but they don't always know what a diode is and, as such, don't know that "completely different" really just equates to "different diodes". Simply put, Josh is good at upselling a point that is rather mundane. :P
 
Ah cool I hadn’t been following that at all. I would assume so. Would be curious to see what they landed on.

With the klon the dirty and clean paths are mixed depending on gain pot, so the Vf is important to how much of each path is mixed together (higher Vf will make the dirty channel louder in the mix). That was part of my problem, eith the schottkys being similar Vf as the ge, adding series resistor made the dirty channel louder. The gain levels of the paths could be redesigned to compensate in theory.
 
It’s a fair point, he’s great at marketing and makes pedals that people enjoy, so good for guitarists in general, maybe. As long as they know what they’re paying for. Seems like he leverages the ‘educational’ aspect for more marketing hype, but obscures the actual info in self serving ways, I guess that’s what’s bothersome.
 
phi1 said:
Side note, has anyone been successful emulating germanium diodes with schotkey plus series R?
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What's All This Stuff About Germanium Diode Leakage?

Ok it looks like my multi meter is borked. The figures I'm getting are very weird. I've been wanting a new one for a while so I'll have a hunt to see what's suitable. As an example I have some figures below. My PSU is supplying 9.16v to my breadboard and everything is connected as you...
forum.pedalpcb.com forum.pedalpcb.com
 
Ok, so here's my first stab at getting a trace. I did a lot of comparing with a few different DOD 250 schematics. This one appears to be very, very similar. Because I don't have any way of knowing all the capacitor values, some of them will amount to a bit of guess work. What I have is what I think is damn close though. Will need to breadboard it and see.

Also, while working on this, I managed to break the ribbon cable on the pedal. Seems JHS is using cheap-ass ribbon cables for this one. Funny how my fix will actually be a bit of an upgrade for it. Definitely not keeping it. Way, way too much for what it is. :P

IMG_0200.jpeg
 

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jimilee said:
Dayum! That’s about 5 bucks worth of parts, isn’t it?
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If I had to guess, the total build is probably somewhere around $20 worth of parts....and that's at bulk costs. They probably have solder machines, custom PCB fabrication, and a bunch of employees too so...that does bring up the cost. Still, compared to what EQD does, I don't think it's the right price. I mean, $#!t, EQD sells the Plumes for $99, the Hizumitas for $149...both of which have twice the components. Just don't get it. Interesting study but, man, it's really revealing in terms of what the marketing strategy is for JHS.
 
jeffwhitfield said:
If I had to guess, the total build is probably somewhere around $20 worth of parts....and that's at bulk costs. They probably have solder machines, custom PCB fabrication, and a bunch of employees too so...that does bring up the cost. Still, compared to what EQD does, I don't think it's the right price. I mean, $#!t, EQD sells the Plumes for $99, the Hizumitas for $149...both of which have twice the components. Just don't get it. Interesting study but, man, it's really revealing in terms of what the marketing strategy is for JHS.
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Totally agree.
 
Hope you can get at least most of your investment back. Or, put the Ge's in there and you could sell it as upgraded!

On the bright side, this may re-spark an interesting (but not new) discussion about replacing Ge with Schottky effectively for diy-ers. I would be interested to hear if anyone does a comparison between GE diodes and the shcottky's in there. and how mush effect does the series resistor have? These would be very easy experiments on a 250 circuit (I may get around to it at some point, would be interested to hear if anyone else does).
 
Shouldn't there be a voltage divider providing Vcc? Usually it's 2 resistors around 20K.
 
phi1 said:
Hope you can get at least most of your investment back. Or, put the Ge's in there and you could sell it as upgraded!
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Oh, I'll get my investment back. I plan on returning the pedal. I have until April 1st to do so. Even then, thanks to Amazon, I'll have another 14 days to get it to the UPS store. Plenty of time to finish this little project. Just need to do a bit of breadboarding and testing. Might do a bit of recording with the actual JHS pedal just in case. Basically record a series of riffs that I can play back and compare to the one I breadboard. That way, if I do need to return the pedal before I'm actually finished, I'll still have a control to test against. :D
 
spi said:
Shouldn't there be a voltage divider providing Vcc? Usually it's 2 resistors around 20K.
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I'll double check...but I think that's what R2 is for. Some of the differences between it and the 250 circuit I already have breadboarded are a bit weird.
 
Jeff, make sure you record the signal split — dry and JHS, that way you can re-amp the exact same riff with all its nuances through your version of the circ.

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JHS says it’s a “replication”, then lists a bunch of changes from the original circuit; Maybe JHS needs to look up the denotative meaning of the word.
 
Just updated the schematic. Missed a resistor. Apparently, R2 and R4 work off each other to provide a voltage divider off the VCC.

@Feral Feline Good tip! Actually easy to do with my rig. Got a split rig already so I can basically just record it with two mono channels: one dry and one with the JHS. No problemo! :D
 

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I don’t think R2 and R4 would work to make Vref like that, I’m thinking there’s still a resistor or two missing?
 
phi1 said:
I don’t think R2 and R4 would work to make Vref like that, I’m thinking there’s still a resistor or two missing?
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Nope, a voltage decider is just vcc, two resistors and a ground. Sometimes, there’s an electro thrown in for power supply noise, but it isn’t necessary. You may just be used to seeing it in the power section of a schematic.
 
Robert said:
R2/R4 would make VREF around 0.09V, that can't be right.


BTW those T4 diodes are 1N4148.
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All the traditional (?) schematics have 4148. According to the live video he did after the release, he claimed he used 4001. I don’t know why, voodoo maybe?
 
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