Recent content by JTEX

  1. JTEX

    Variable capacitor

    ^ Depends on the circuit. Panning adds a significant series resistance when not fully at one end or the other. The circuit above acts like a pure cap with no series resistance.
  2. JTEX

    Variable capacitor

    I read somewhere that there's a floating version, but haven't investigated further.
  3. JTEX

    Variable capacitor

    If you've used (or thought about using) something like a rotary switch to switch between different capacitor values in a circuit, you might want to consider a continuously variable "active cap" instead. It can be made with a simple pot and a couple of op amps that form a capacitance multiplier...
  4. JTEX

    How do YOU clean your boards?

    I used to use no-clean but stopped. Rosin just works better for me, especially on non-perfect, somewhat oxidized stuff such as older parts or wires or PCBs. And it smells a lot better too, as a bonus. Oh the other hand, if I do want to clean "no-clean" flux (because it still looks greasy and...
  5. JTEX

    How do YOU clean your boards?

    99% isopropyl alcohol from a dispenser and a standard-issue short-and-stiff-bristled brush from the dollar store (natural fibers, as opposed to plastic, if I can find one). I cut the bristles shorter if it helps. I pat the wet board with (allegedly) lint-free Kleenex to wick as much...
  6. JTEX

    Canadian PCB Manufacturers?

    I'm in Canada and my "local" PCB manufacturer is JLCPCB.
  7. JTEX

    Power Filter Section

    The second picture will do a much better job of filtering power supply noise because the series resistor R7 forms a low pass filter with C4. This comes at the cost of a slight voltage drop across R7. With most pedals drawing only a few mA though, the drop is very minimal: 10 ohms x 10mA = 100mV...
  8. JTEX

    New (to me) opamps

    Don't people mostly use AC adapters to power pedals these days? In which case super low power is not really important... Might as well use something like an LM4808 if you can spare 1mA idle. It's also a max 6V part, so it would need a regulator.
  9. JTEX

    New (to me) opamps

    I tested an OPA2310 the other day to see if it makes sense as a headphone amp, given its high output current capability (150mA) and very low idle current (~165uA per channel). Great for battery power! Only problem is that it doesn't take more than a 6V supply. But a low quiescent voltage...
  10. JTEX

    when to use mlcc capacitors

    MLCCs (with an X5R/X7R dielectric) are fine in the audio path (certainly as far as pedals go, at least) as long as any voltage across them is far less than their rated voltage. This avoids voltage-dependent loss of capacitance and distortion. I use 10% tolerance X7R rated at 50V (or more) and...
  11. JTEX

    Voltage Supply Question

    Check R44 if the ICs don't get power. Also, make sure it's 100 ohms and not 100k.
  12. JTEX

    What are the most rugged 1/4" jacks people are using?

    I feel that this style is the most reliable of them all, but it needs a bit more space than other designs:
  13. JTEX

    Resistor values and Noise

    The caps do not contribute noise. The 3 circuits have the same output level and frequency response. Not sure I understand the last question.
  14. JTEX

    What kind of pot is this?

    I thought the most common, garden variety log type is 10% at mid travel. Is this not the case?
  15. JTEX

    What kind of pot is this?

    The first 10 probably means that you get 10% of the total value when it's at the half rotation point, measured between the CW lug and middle (it's the opposite of a log pot, which would be 10% measured from CCW to middle)
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