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    M125 anniversary look back


    Posts : 218
    Join date : 2016-08-07
    Location : Ontario, Canada

    M125 anniversary look back

    Post by LeGrace on Mon Sep 11, 2017 3:36 pm

    Elation all the way through to despair about describes it. Today am enjoying them greatly, but it wasn't always sunshine. I started out with zero knowledge of tube amps, just dove right in. What a difference a year makes!  

    I remember the sense of relief when I first turned them on and they worked! A high five for the very detailed and clear instructions. But I was downtrodden a week later when I flipped the switch, saw an arc flash, and one of the amps died. At that point I had no idea why. Just knew that I had spent a fair bit and one was already broken. This became my first lesson, actually two lessons. First one being M125's devour 5AR4's, secondly when it comes to tube amps, panic slowly! (and keep lots of spare fuses on hand) Because 3 weeks later it happened again! Panic attack! But with great help from this forum I learned about the yellow sheet diode mod and stouter rectifier options. (such as GZ37's!)

    So I'm thinking I'm good now after about 6 months of stable operation post diode mod. Wrong, the amps weren't done with me yet. Next a power tube goes. Tube will still fairly new and mainly I was feeling ripped off. But then I experience two red plate events in succession. confused Then another power tube goes. Paranoia ensues! Well all of it boiled down to crappy power tubes! Installed new ones recently and talk about an improvement. Bias used to swing all over but is now stable. Another lesson, stick to reputable tube outfits!

    Meanwhile through all of this I'm also experiencing varying levels of amplifier hum. Funny at first it didn't bother me much, but as I invested more and more into my audio system it really started to get on my nerves. My amps are dead quiet now, but I had to resort to cheater plugs. Currently looking for a safer solution and if I find one will definitely share.

    So finally my amps are  silent, they sound amazing, and they are stable. If you have just built a pair of these fantastic amps, are just getting into tubes like I was, then hopefully some of this can save you repeating some of the mistakes I made. FWIW.

    Posts : 562
    Join date : 2013-03-19
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    Re: M125 anniversary look back

    Post by corndog71 on Mon Sep 11, 2017 5:49 pm

    My first tube amp story went pretty much the same way. I picked up a used and rebuilt ST70 from a local hifi store and learned just about every which way things can go wrong. I went through lots of cheap rectifiers and power tubes. This was about 13 years ago. Since then I've built and rebuilt several tube amps and it never gets old. The simplicity, flexibility and sonic bliss were all factors with channeling my energy into these.
    Just wait until you see what I'm cooking up next!

      Current date/time is Thu Sep 21, 2017 7:13 pm