Keeley Katana...is this right? And popping.

[alphadog808]

Hi guys, so I just finished building the katana and have it wired up for testing. Everything seems to work, but maybe it's me, but it seems the clean boost is REALLY dark. As there isn't a tone/treble knob, I'm wondering if something is wrong or if it's supposed to be this way. I'm thinking not as it's touted as being very transparent.

When testing with a battery, I get 16.9v.

IC pinouts are 8.6--4.3--0--0--0--4--3.6--8.6

JFETs are both D8.4--S1.2--G0

The second issue I see is there is a big pop when you switch modes(I'm using a push/pull pot).  Would putting a resistor(unsure of the size) inline with the 2 caps on the switch remedy this?  Would it cause any type of tone change?  As far as I can tell, the real katana doesn't pop, so I wonder if maybe the layout is missing a few part/s?

[induction]

Could be a misplaced component or wrong value.

If you post some pictures of your build, maybe we'll spot something.

[alphadog808]

Thanks induction, you're always ready to help, I appreciate it.  Well, I was able to swap out the 150nf cap on the switch to 15n and now everything sounds good...except the pop.  

I have since put a 75k resistor inline with the 10uf electo on the switch(positive side) and it does lower the pop.  As I increase the resistor, the pop gets smaller.  However, I do notice a tone change, but I'm not sure if it's due to a volume drop or a tone change.  It's hard for me to tell as by the time I swap back and forth the actual tone is long gone from my memory.  

That being said, would you know if that resistor is actually changing the tone or just lowering the volume?  If it's just a volume drop, that's fine, there is alot of volume to go on this pedal!

Thanks!

[induction]

That 15nF on the switch is only in the circuit with the boost mode on, so it shouldn't affect the sound with the boost off. If the non-boost mode sounds different when you swap caps, the switch is probably wired wrong. (It sounds like you have the cap in the circuit in non-boosted mode, and switch it out of the circuit for boosted mode. That would explain why it was so dark in non-boosted mode, and much brighter in boosted mode.) Of course, if you like it, that's all that matters.

Putting a resistor inline with the 10uF will affect the amount of boost. The gain of that jfet stage is dependent on the ratio: drain resistor/source resistor. The switch puts the 10uF in parallel with the source resistor, which reduces the effective value of source resistance, thus increasing gain. Putting a resistor in series with that cap increases the effective source resistance, so the gain will not increase as much with the resistor in there.  The larger the resistor, the lower the boost, which is why the pop gets quieter. No matter how large the resistor, the gain will never be less than in non-boosted mode, but above 100k the boost will be too small to notice. The resistor shouldn't affect the frequency content very much. It will add a bit more bass (technically, it will cut the bass less than the treble), but it's mostly below 100Hz, so it shouldn't be too noticeable.

I think the reason it pops is that the floating (positive) side of the 10uF will hover around ground, and the jfet source will be higher than ground, so there will be a dc shift when you flip the switch. You might be able to get rid of the pop by keeping the 10uF connected all the time, and put a 500k or so resistor in series for non-boosted mode. Then use the switch to jumper around the resistor. I'd breadboard it first, though. I haven't tried it, and it might pop anyway.

Edit: Of course, if your switch is wired wrong, fixing it may fix the pop (or make it worse, I guess). I'd figure out the correct switch wiring first, and work on the pop second.

[alphadog808]

wow, that's for that, Induction!  

I agree, I was a bit confused as how changing the cap value, "fixed" my non boost problem as I swear the issue I was seeing was on the non boosted side.  Maybe I got confused on which was what, not sure.  

I have the switch part of the circuit hooked up to a push/pull pot and the wiring layout for it mimics what the dpdt switch; I'll have to double check it tho because to my ears, it seems the pedal is a *little* more dirty when those 2 caps are OUT of the circuit.  I can't be sure how much more grit the boost is supposed to give though as I really haven't tried a real katana.  

Thanks again, buddy, I appreciate it!