Noise problem on the last batch

Discuss Yocto construction and related issues
  • Hi,
    I have the same issue with the Noise section...
    I have two built Yoctos, and with one I cannot get below 700mV AC on Pin 1, and with the other Yocto, range is btw 16mV and 20mV AC.
    I built both Yoctos in parallel, so that is really weird...
    Both 4558 are properly powered (approx. +15v/-15v)

    On the first Yocto, the consequence is crappy-sounding Cymbal, Clap and Snare
    On the second Yocto, same thing, with nearly no decay on the clap and on the Snare.

    Here are pictures of the two Noise circuits :

    First Yocto (700mV AC) :
    Image


    Second Yocto (20mV AC) :
    Image

    Thanks in advance for you help!
  • Hi guys,

    I got the same issue yesterday with a Yocto a guy brought me, there's was no "snare strainer" (no pink noise) and the clap was pretty low in volume. So i tried to calibrate the noise but cannot get anything good, so I did the mod suggested on page 15 of the service manual (http://www.ericarcher.net/wp-content/up ... vc-man.pdf) and it's also mentionned on Masuto's website https://masutopedals.wordpress.com/2016 ... ding-tips/.

    To resume
    - R129 is replaced with a jumper,
    - R131 (originally 300K) is replaced with 100K,
    - R127 (originally 4.7K) is replaced with a 10uF polarized cap (Masuto show the correct orientation, negative side on the right side of R127, going to the ground)
    - add a 22pF cap in parrallel with R130

    After the mod, I was able to dial 130mV from the noise section, hope it solves your tuning issues!

    It's weird cause on the first yocto I built (from the first batch), I didn't had to do any mod for the noise section.
  • Hi everyone, hi Bastien!

    I did the mod but still wasn't able to perform a proper calibration.

    So what I finally did was using the ear calibration:
    1. tweaking TM3 until the clap attack was as I wanted to hear it;
    2.tweaking the noise trimmer until I found the sweat spot between "I cannot hear the clap reverb" and "I sounds like sh*t".
    3. verifying this setting with the Snare drum (and, of course, it also sounded nice)

    So my advice if you have difficulties calibrating is : trust your ears! ;)

    Cheers to you all!
  • I would recommend to build also a little daughterboard to control noise for the relevant sounds.. so handy.
  • I would also get a batch of sc828 and try different hfe'd transistors for the noise section.
  • Masuto wrote:I would also get a batch of sc828 and try different hfe'd transistors for the noise section.
    It doesn't seems related to hfe, I tried around 30 sc828 and only found two that gave a good result (all others were over 500mV RMS with TM4 at minimum), I mesured some "good" and "bad" ones and the difference in hfe didn't seems to have an incidence. Those transistors came from eBay, I ordered some others from Reichelt, I'll test to see if there's a difference.

    Before getting ordering those sc828, I tried with a 2SC945 as suggested in another topic of the forum, and I found one that suit more easily than with the batch of sc828 I had after. I'll check if there's a difference in sound but it seems pretty close.

    I'll do some other test soon and post the result here.
  • Hi,

    Also had trouble adjusting the noise level. Only adj. 20-70mV.
    But after modification mentioned earlier in this topic, it was Ok.
    Checked also with scope, Nice random noise...

    Regards,

    Hans
  • You need to put a 2SC828 with a hFE of at least 300.
  • Hi !
    I replaced the 2SC828 with another one, from another manufacturer, and the awfull-sounding claps and toms are now perfect. Old 828 hFE was 282, new 828 hFE is 350.
    So in my (narrow) experience, there's a connection btw hFE and sound.