Narosla—Partially verified

[Droogie]

So I built this up today and get boost, running at 9v, trim set to 4.5. It certainly boosts, but the switches don't do anything. I disconnected the switches so I could swap leads in case my assumption about which pole to connect to the square pad was incorrect. Hopefully I'm just being a dope!

[selfdestroyer]

Heres mine from Sunday:


I am having a bit of issues getting it biased as Q1 is not being happy. I HATE J201's lol

But my Hot switch definitely brightens up the sound considerably. You may have a bridge or the wrong cap for C5... maybe.

Cody

[Droogie]

Okay. I've got a something amiss! I'll check the 3n3. I know it's hard to tell from the blurry solder-side pic, but no bridges found. I'll check again tho.

[midwayfair]

Use your multimeter not your eyes. Measure the resistance across R6. Does it go to 0 when the switch is flipped, and is it 15K when it's not?

Cody: Bias isn't really important here. Anything below 7V and above 3V is fine but will make a difference. Not really sure what could go wrong with the bias on something like this ...

I'm going to drop a criticism into this thread, though. The original used a 2N5457 and a fixed 8.2K drain resistor. The J201 requires a much larger drain resistor, which in turn increases the output impedance of the stage, as much as tripling the resistance seen by the 3n3 (could be even more with a particularly high-gain J201 or a lower bias) and severely lowering the low-pass frequency cutoff. The 15K is actually likely to be less resistance than the value the trimpot is set at, so it doesn't even raise the cutoff by a whole octave, whereas the original raised the cutoff an octave and a half.

I would give serious thought to recalculating the 15K and 3n3 and/or going back to the 2N5457 so that a "flat" treble setting exists. Otherwise, I'd expect the pedal to be much darker than the EP Booster.

[selfdestroyer]

Use your multimeter not your eyes. Measure the resistance across R6. Does it go to 0 when the switch is flipped, and is it 15K when it's not?

Cody: Bias isn't really important here. Anything below 7V and above 3V is fine but will make a difference. Not really sure what could go wrong with the bias on something like this ...

I'm going to drop a criticism into this thread, though. The original used a 2N5457 and a fixed 8.2K drain resistor. The J201 requires a much larger drain resistor, which in turn increases the output impedance of the stage, as much as tripling the resistance seen by the 3n3 (could be even more with a particularly high-gain J201 or a lower bias) and severely lowering the low-pass frequency cutoff. The 15K is actually likely to be less resistance than the value the trimpot is set at, so it doesn't even raise the cutoff by a whole octave, whereas the original raised the cutoff an octave and a half.

I would give serious thought to recalculating the 15K and 3n3 and/or going back to the 2N5457 so that a "flat" treble setting exists. Otherwise, I'd expect the pedal to be much darker than the EP Booster.

Thanks Jon for the note. I can get it to around 6/7v but not near the 4.5v that I was shooting for (As per the doc). I will need to do some more reading on what your pointing out with the frequency cutoff but it looks to be worth looking into.

Cody

[verr76]

Tried this out and I'm getting overdrive and not a clean boost, and volume is higher than unity even with pot fully CCW. All parts seem to be right. Using a 2n3904 for Q2. Biasing Q1 (tested with normal through hole and smd adapted to a small piece or perf) doesn't help . Anything in particular to look for?