Extra 9 Mod Hihat filter humming

Discuss Nava construction and related issues
  • plaque@aon.at wrote:Hello there!
    I am almost finished with the E9 mod.
    Nava was tested without mod: perfect.
    Everything works fine with the mod, but when i switch in the filter on the Hihat, it basically works (HP/BP/LP) but with terrible hum on it, changing a bit when turning cutoff or envelope on the E9. Sounds a bit like a grounding problem...
    I built a second E9 pcb - with exactly the same behavior. I built it very carefully.

    Has anyone had similar issues. Or already got the HH filter working on the E9?

    Thank you very much for all comments!!!
    Check the three 1.5n caps at C77, C78 and C79. They are very sensitive and prone to cause filter issues. Replace each of them carefully and see if it solves your issue. ;)
  • @ Klanggenerator

    Thank you for for answer... These capacitors are good.
    As i use a 16V power supply now, most of the hum is gone - but, depending on the settings of utoff and envelope potentiometers there is still some humming to hear....also when i use a 18V power supply.

    Also: when i switch in the HH filter i can hear a loud noise, like there is DC on the output (which is not)...is that normal, or should moving the HP/LP/BP switch be silent?

    I found following in the forum from another one with this problem:
    "At last I had to change some resistors value to get the HH filter quiet. I replaced R71 for a 10K, R72 for a 200K and R86_2 for a 10K. This lower the level reduction to the filter input and the filter output at the same time."

    You seem to have a lot experience with Nava and the E9 mod....is it really neccessary to modify the HH filter circuit to get reed of the problem?
    Thank you!!
  • plaque@aon.at wrote: Also: when i switch in the HH filter i can hear a loud noise, like there is DC on the output (which is not)...is that normal, or should moving the HP/LP/BP switch be silent?
    The designer admitted it's normal and pretended he knew what it comes from, but didn't go until offering a solution for it.
    I found following in the forum from another one with this problem:
    "At last I had to change some resistors value to get the HH filter quiet. I replaced R71 for a 10K, R72 for a 200K and R86_2 for a 10K. This lower the level reduction to the filter input and the filter output at the same time."

    You seem to have a lot experience with Nava and the E9 mod....is it really neccessary to modify the HH filter circuit to get reed of the problem?
    Thank you!!
    This solution was the one the designer of the circuit told me to do, but without giving precise values, so I had to find some myself.
  • @gihaume

    Thank you very much - my Hihat filter is almost clean now!

    Another problem...i checked the bassdrum with the E9 mod now, and found that it gets noisy when the E9 mod is in place. It´s around the Pitch modulation of the Extra9. The circuit is passive and so simple that there can not be a mistake from my side.....is your bassdrum perfect with the E9 mod?

    UPDATE! I found out that the noise on the bass drum is induced by running the audio & noise signals from & to the Extra 9 through an unshielded flat cable.
    The problem disappears when you use shielded cables!! Also the snare is much much cleaner now!!!

    My Nava Extra 9 is finally finished....if someone knows where to get "second noise source" PCBs please let me know....
  • plaque@aon.at wrote: Another problem...i checked the bassdrum with the E9 mod now, and found that it gets noisy when the E9 mod is in place. It´s around the Pitch modulation of the Extra9. The circuit is passive and so simple that there can not be a mistake from my side.....is your bassdrum perfect with the E9 mod?

    UPDATE! I found out that the noise on the bass drum is induced by running the audio & noise signals from & to the Extra 9 through an unshielded flat cable.
    The problem disappears when you use shielded cables!! Also the snare is much much cleaner now!!!
    Hi.
    I just noticed that the BD with the Extra9 mod in fact does have a hiss, which I cannot seem to alter while turning the pots on the front panel. You can have a listen to it here:

    https://gofile.io/d/W1363v

    Is this the same behavior you were experiencing on your unit?
    Thanks,
    F.
  • FlavioB wrote: Hi.
    I just noticed that the BD with the Extra9 mod in fact does have a hiss, which I cannot seem to alter while turning the pots on the front panel. You can have a listen to it here:

    https://gofile.io/d/W1363v

    Is this the same behavior you were experiencing on your unit?
    Thanks,
    F.
    Not sure if it is the same issue, but try this:

    In the Bassdrum section, cable 1 and 2 (noise decay in/out) leading from the Nava to the Extra 9 board, must not be bundled with the other cables. There's a crosstalk from noise to audio.

    Simply separating these two cables and keeping them 2cm apart from the rest of the cables may solve the problem.