Madamp M15 with JJ E83CC in Phase Inverter position causes a very loud and uncontrolled hum

  • I wanted to get a better set of tubes than what the amp kit shipped with. My default tube is the E83CC (…ectronic?number=NN032-SYM). I ordered a balanced tube for the PI of the amp.

    However, when it's installed, the amp has an extremely loud humming sound. The amp is still functional aside from this really loud hum. I put this tube in V1 and there was no issues. I've put a standard JJ ECC83S tube in the PI and it works fine. I am able to use E83CC in V1 and V2 without issues, so it seems to be specifically putting an E83CC in the PI triggers something.

    Any ideas why this tube cannot work properly in the Phase Inverter? Is there any sort of biasing or something which might cause this issue? Do I need to make changes to the amp to make this tube work in this position? I'm using it in the PI of another amp and really like these tubes.

  • That's what I thought, but the tube works fine in the V1 and V2 positions, and I have tried multiple other tubes in the V3 (PI) position

    This seems to be a specific incompatibility with the E83CC tube in the PI position.

    I'm wondering if maybe the E83CC, which is a variation of the ECC83 has a different attribute somewhere which pushes the M15 circuit out of tolerances?

    As I like this tube, and it wasn't cheap, I'd really like to use it if it's possible.

  • Honestly - I'm confused by JJ's naming schema. It was already different in the past to other tube vendors, but is now even more confusing.
    In short, this is what was valid until some years ago:
    1) Until the early 70s of the last century, there were ECC83, E83CC (technically the same but longlife and low tolerances), ECC803S (frame grid version from Telefunken, made initially for measurement systems, with balanced systems, low microphonic). All three are fully compatible in audio systems
    2) When TFK stopped their production, they sold the production line for E803S to Tesla, who then started manufacturing this tube. For whatever weird reason they named their then "new" frame grid tube not ECC803S but E83CC and named their standard (long plate) ECC83 then ECC803S
    3) When (privately owned) JJ bought the production line(s) from Tesla, the Tesla E803S became JJ E803S and they renamed the Tesla E83CC to JJ ECC83S.

    At one point in time (2020?) JJ realized that they could get much more money for their frame grid ECC83S and seem to have renamed (at least some of) their ECC83 types. It's not really clear to me, but this is what I understand:
    1) ECC83S short plate => it's unclear to me if this is still the "old" TFK ECC803S, maybe they installed a new production line and these are now standard (no grid frame) ECC83?
    2) ECC83MG medium plate => JJ states "medium gain" for this ECC83 tube but mutual conductance and amplication factor is the same as for a standard ECC83 !?
    3) ECC803S long plate => standard ECC83 values but long plate
    4) E83CC => not listed on JJ website, sold by various resellers stating that this is a frame grid tube. So this seems to be the old TFK ECC803S sold for years as JJ ECC83S

    All these variants are fully compatible in audio frequency systems, there might be strange circuits where slightly different capacitance values of the ECC83 tubes values can result in oscillations but definitely not in MADAMPs. So I don't know why your JJ E83CC is not working in your MADAMP. Can you post a high resolution photo of your E83CC, I would like to compare it to my JJ ECC83S from the last decade...

  • Wow, that's a lot of changes! I know very little about the different tubes, but I do know that the E83CC tubes sound great compared to the Ruby tubes they replaced.

    I remember some marketing about how it was based on some Siemens design if I recall correctly. I find it really strange, since the tube was a new model for 2020 and then completely discontinued by 2021...

    I have taken a photo of the relevant E83CC tube alongside the ECC83S tube that works in the PI position. They definitely are different designs internally, but I am no expert nor do I know the name of the parts.

    In both photos, it's E83CC on the left and ECC83S on the right.

    Differences I could spot:

    1. the "shells" are different shapes, and they "fit" together opposite
    2. the small circular shafts that run inside the dull gray "shells" are thicker on the E83CC

    Otherwise, to my untrained eye, they looks surprisingly similar!

    The ECC83S came out of an Orange Rocker 15 that was purchased 1-2 years ago.

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