euna/skeptical buffer C1 is 3pF but with large footprint on silkscreen?!?

retail board as in the 29 pedals retail board or the pedalpcb retail board? i can confirm that my pedalpcb retail board also reads 3p, but that wasn't my concern. i'm wondering if it's supposed to be '3u' or something. (i assumed it wasn't petafarads, which is several order of magnitude beyond present human technology)
 
I'm actually skeptical about this buffer. 3 picofarads is nothing. An inch of guitar cable.

Edit: maybe it's a placeholder cap just asking to be modded to a value that actually does something. I sometimes change cap values to almost nothing in circuit simulators to basically take them out of the circuit while I try something out, without actually deleting the symbol. Or I might temporarily change a simulated resistor to 100 Gigaohms for similar reasons. There. That's my theory.
 
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got it. i somehow didn't realize that the pedalpcb.com site didn't count as retail ('sales from business to consumer') in your mind. (as a pathological literalist i've got to get clarifications on everything.... my wife hates me!)
 
Robert said:
It's just an RF filter from the input to ground.
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I hate to ask, given how busy I imagine you to be—do you have the entire schematic for the EUNA? I’d love to see what the entire power supply looks like. I think it’s unfair to look at only the active circuitry and pass “judgements” without getting a better sense of what the entire jam looks like. Obviously the main parts cost on the EUNA are in the power supply. I don’t think the designer is doing this as an act of deception, just to give the appearance of something “special” under the hood.
 
I don't have the schematic for the power supply on this computer, but it's basically verbatim from the MAXIM datasheet for the MAX743 IC.

Full-wave bridge rectifier into a 5V regulator which powers the circuit below (from the datasheet), then into a pair of positive/negative regulators.

1666975625283-png.34645


I think it's a cool concept in theory, but who is this actually designed for? Are there that many people out there buying $270 buffers who don't have a suitable power supply? The amount of current wasted by this feature is a bit extreme. It's a cool gimmick, but is it really necessary?
 
Robert said:
I think it's a cool concept in theory, but who is this actually designed for? Are there that many people out there buying $270 buffers who don't have a suitable power supply? The amount of current wasted by this feature is a bit extreme. It's a cool gimmick, but is it really necessary?
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It’s for when you need exquisite tone but your only available source of power is a windmill hooked up to a field-issued emergency crank generator
 
Nope, I don't go by silkscreen values (I generally don't even use the printed RefDes). I remove and measure all SMD components.

It's definitely 3pF.

I don't think there were any "gotchas" on the EUNA, but the FLWR had some incorrectly marked values on the board. (Revisions I assume)
 
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JTEX said:
3pF across the input won't do anything of any significance for RF, and even less at audio frequencies. Heck, the TL072 on its own has higher input capacitance. Could it be a silkscreen typo? Or are 29 Pedals full of it?
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I was gonna say the same thing. 3pF on the input BEFORE a high impedance buffer aint doin’ shit.

I don’t get RF rejection of any appreciable amount on my Fuzz Faces until 1000pF input to ground.
 
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