Mix Out Noisy/Distorted

Discuss Nava construction and related issues
  • KlangGenerator wrote:Also very interesting:

    https://www.gearslutz.com/board/electro ... idual.html

    I will try replacing the caps with 10uf ones as I don't want to lose all that bottom end on the main outs.
    C153/ C154
  • Don't want to make another thread, so bumpin' this.
    I'm building the remaining seq&mixer part currently and if i understand correctly, i can omit safely all the parts that is belong to the muting circuit [ To name the parts exactly - C142, C143, D193, D194, D195, R468, R469, R470, R471, R472, Q82, Q83 ], if i don't need that muting circuit, that is used only once on power on. One thing i only think about, is to put some high resistance (100k-1M) between Q82, Q83 collector and emitter to have some ground current path for opamp.
  • redstorm wrote:Don't want to make another thread, so bumpin' this.
    I'm building the remaining seq&mixer part currently and if i understand correctly, i can omit safely all the parts that is belong to the muting circuit [ To name the parts exactly - C142, C143, D193, D194, D195, R468, R469, R470, R471, R472, Q82, Q83 ], if i don't need that muting circuit, that is used only once on power on. One thing i only think about, is to put some high resistance (100k-1M) between Q82, Q83 collector and emitter to have some ground current path for opamp.
    Dear Redstrom,

    To bypass the muting circuit simply omit both transistors Q82 and Q83 and you don't need all part from the muting circuit (C142, C143, D193, D194, D195, R468, R469, R470, R471, R472)

    Best regards,
    e-licktronic
    Best regards,
    e-licktronic
  • I also battled with an overwhelming noise floor on my master output. No amount of shielding or ferrite beads or good vibes managed to remedy the noise. Frustratingly, I found no issues with my board either. Fed up with the noise I verified that the muting circuit was the culprit and populated Q82 and Q83 with sockets so that I may test a new pair of 2SC2878. The next pair worked like a charm. I recommend that anybody populating a Nava PCB socket these transistors as it seems that many of them are leaky and ironically the source of much noise and bad juju.
  • After the last build of Nava I also had have terrible noise, but it its gone after complete cleaning the board. I found a little piece of wire shorted one of the transistor. After that master is absolute clean and free of distortions. My suggestion is check build for shorts and bad components (I repaired one Nava with noised master. One of the 69 ic was bad) first!
  • I had the same issue as the OP and found this is very likely because of a too weak external voltage transformer. E-licktronic tells us to get a 15VAC 1000mA, just as the Yocto, but I found that the Nava will eat two times more current (just measured). So if like me you used a same transformer, it may explain the issue... Additionally I was measuring the output of various transformers I had and found that the 12V ones were just giving 15V, so thought they were not accorded to their specs and lucky me it would then be just like a 15V one... but in fact they're totally right and it's planned that when loaded their voltage will drop and be as specs.

    What I think happens in this case is that the regulators will still want to reach their high spec'd voltage but the transformer can't give enough and the voltage constantly drop of a few mV, producing a more or less nice bassy saw wave which can be heard a bit in the background noise and in my case very noticeably in the Extra9 HH Steiner Parker filter.

    About the Master Out being (the only one) distorded, I think the issue is because its level is pretty high, so its amp would like to use the whole +-15V of power and when going high on the same frequencies that the saw/drops from the power rail(s), there will be some distortion.

    15VAC 1000mA transformers are not that common... this is just a bit higher than what can be found easily. I'm planning to order the Mascot 8710 (1000mA) or 8810 (1300mA) which should be fine.
  • I can confirm that using a Mascot 8810 spec'd at 15V 1.3A makes the background noise quieter, but there still is some (for sure wouldn't be as annoying without the HH Steiner Parker filter circuit addition) so the next thing I will consider may be to change the PSU capacitors for more expensive ones.
  • Beginning to finish my Nava 1.02 build (very nice indeed :D ) and I too had problem with stereo out distorsion. Removed R469 and R470 and way better. That's fine by me, the noise when turning on is not so bad.
  • An old thread I know, but really interesting here. I've built 4 Nava so far. None of them have had any distortion or issues on the Master. Building a 5th one for a customer and testing the BD and crazy distortion.

    They had ordered all the parts and the only differences with the other ones I've built :

    1. These are all metal film resistors ( built the others with 5% carbon) can't bieve that would be it.

    2. All poly box caps, vs the nichicon poly film yellow QyX in my others. Maybe?

    3. The 2SC2878. Came with the kit the customer ordered, back in 2017.

    Removed the two trans and distortion is gone.

    Really strange that never had this issue before. I've done the 10uF mod for the 1uF.

    Wondering if it could be down to the 2878s themselves. Will add some sockets and try some others I have.