Eddie Current Super7

Discussion in 'DIY' started by Jh4db536, Jun 27, 2021.

  1. Jh4db536

    Jh4db536 Friend

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    This amp came across my repair desk and i found it to be a very interesting piece that's been passed around the block a few times. The driver filreg is out and i believe it took the RC201 rectifier with it. I'll post a lil commentary on this

    I prefer the amp with only 1 driver + 2 6SN7 power tubes instead of 6 as a headamp.

    It's actually using BOTH internal triodes of the 6SN7's for power in self bias configuration (missing those blackgates in the cathode section, but got NOS carbon compz... i bet this sounds good). So actually it's like 6 triodes of power each channel.

    The amp PSU is designed like a big boi quad power tube EC amp with a hybrid classical CLC and solid state section (green) that gives it three B+ (Purple: L/R power and Driver B+) and hexfred HV rectification, and a dedicated DC filreg for teh driver (red...failed part) all crammed on this tiny board WOW

    always wondered what the HVmosfet does on ecs. don't think it's there for active regulation as the 12v zener biases the gate open. I suspect this one isolates the b+ for the driver tube. there are usually one per Channel on quad tubed ECs

    [​IMG]

    The previous owners have hotrodded and pimped it out. Appears to have either EP or Cinemag EI core OPTs in it...these things are chonkers. They are probably Cinemag as i dont think EP makes EI cores in this shape and by rumors of prior ownership. tbh, i dont even know what a stock one looks like inside and i kinda wish i did. This amp weighs like 50% more than a stock one it's pretty nuts.

    [​IMG] [​IMG]
    The regulated filament DC is Only for the driver tube. I think the Belleson (green) went bad and took out the bridge rectifier (red) behind it. The pinout might not even match the PCB, im not sure. Possibly shorted on the heatsink as no insulating washers were installed on the metal tab power transistor. the regulator operates at 600mA at a fraction of its limit so I don't know why it would die.
    [​IMG]
    The replacement regulator has a insulated power transistor. Verifying function and pinout.
    [​IMG]
    I socketed the area for testing (thank god i did because i think pinout is not matching and i verified something else is broken) and that should make future replacement easier just in case. For now im using test leads until this thing behaves the way i want and waiting for parts to fi it
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    Don't try this at home kids. I just wanted to see what the amp sounds like and confirm that the amp will actually work after i resolve this. It needs life support to work right now
    [​IMG]

    I think someone should make a "Super 3" dedicated headamp version of this. That would be a really cool and use the extra space freed up to use a tube rectifier instead of SS hexfreds.

    Aside from revoicing the amp, there's no much more that can be done with this amp it's pretty maxed out in its current design. Maybe throwing an assortment of value of blackgate cathode caps on each power tube row (3) so one could change the by putting power tube pairs in different rows.

    So maybe the first row would get 10uF caps, second row would get 47uF caps, and third would get 100uF (stock value)?

    The values on the driver tube probably would change the sound (amount of bass coupling?) the most. Just a thought.
     
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    Last edited: Jun 28, 2021
  2. Jh4db536

    Jh4db536 Friend

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    As i suspected the bridge rectifier died. I cut it out and replaced it and now the amp works flawlessly.

    This amp can push my BK20 with 3 tubes lol. The stock one has MASSIVE bass distortion with 7 tubes on speakers probably due to OPT saturation...i would not even consider that usable.

    This unit however, seemed to be able to do the job without tripping on itself, but it wasn't good or anything. I need to roll some better tubes in here and see what it can do.
    [​IMG]
    [​IMG]
     
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  3. Marvey

    Marvey Super Friend

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    I believe the HV Mosfet is there for slow ramp up of voltage during turn on.
     
  4. Jh4db536

    Jh4db536 Friend

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    Ohhh so that's the soft start for the B+? That makes sense since this is Hexfred rectified

    Even the quad tube rectified EC amps have them? I guess softer start?
     
  5. Hands

    Hands Overzealous Auto Flusher - Measurbator

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    Oh, hey, this was my S7! Yes, it went through quite a journey over my few years of ownership. I made several updates and/or new mods before selling it to the current owner.

    I also made plenty of mistakes here and there along the way, the kind that required ugly bandaids and workarounds. This added up over the years in a cumulative fashion. I barely knew how to solder the first time I cracked it open! (And still much I have to learn.)

    Not to mention, it's fuckin' HARD to cram this much stuff inside the S7 case. Especially with different OPTs and those large motor run caps (and dual 5ufs, since I couldn't find 10ufs cheap enough). More excuses: toddler at home, crazy busy with work, limited time and energy to make everything perfect in the amp. I was transparent about this upfront, and the buyer/owner was OK dealing with this monster.

    It was a pretty unfortunate coincidence that it went out on the owner like this. I never had major problems with it (all easily solvable, like hum/ground issues and partially melting caps), despite all my tinkering with it, and gave it a lot of runtime post-mods before I felt comfortable shipping it out.


    All that said...I really appreciate you taking this on for the owner and apologize for any headaches my modding/repair activities might have caused you. I know it's exponentially less fun fixing problems when someone else's less-than-artistic (i.e. messy, amateur) work gets in your way. Please do not hesitate to reach out if you have any questions or concerns. I'm more than happy to help make sure this amp keeps running strong in the future, even if it's just sharing what I know about the amp.


    Bridge rectifier was one thing I suggested as a possible culprit. From what other owners have told me, not the first time it has happened. And that Belleson regulator went out on at least another owner's amp as well.

    Glad to know it was a relatively simple fix in this case!


    The OPTs are based on the Mable Advanced 300B transformers, at least before those apparently revised. I got them from a shady, black market dealer. About all I'll say on that for now. Maybe some of you can figure out exactly what they are. :)

    One little mod I find surprisingly interesting is the potentiometer. It's a vintage Tocos Cosmos. Randomly found someone selling a few of them on eBay a year or two ago for like $20 total. Using alligator clips, I "rolled" those and other pots in my collection, both to find what sounded best and had good channel matching. These pretty easily sounded the best to my ears, and channel matching, while not quite at Alps level, was noticeably better than most carbon pots. Overall, reminds me of the Noble pots.

    I don't think folks give potentiometers enough credit in amp voicing. Sometimes I think they do more than caps and tubes...

    And those motor run caps are great at giving a sense of drive and dynamics. But, dear lord, it was a big pain to figure out how to fit them in the case! I got it eventually, albeit with some ugly power transformer to PCB wiring rework. And many broken wires going to the very-artistically-taped cap leads when pulling the top of the chassis off just a bit too much...


    It's definitely a Frankenstein's monster sort of amp. Weird, but cool, creature how it turned out.

    I'm biased, but I was really pleased how the amp sounded before I shipped it out to the new owner. Ballsy, the right kind of warm and smooth (didn't sound veiled or soft), just a lot of fun to listen to without giving up technical strengths and nuance.
     
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  6. Jh4db536

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    Great!! the original owners weighed in. very cool.

    It's technically much better than the original one (had a stock one to compare to), also quite different sounding. I never would've guessed it had mixed metal opt, but very well as they seem to hold up to their power ratings. I had the same Opt in my 300b amp and it sounded a bit different than this amp.

    Now that i socketed things, replacement will be much easier in the future if it goes out; the PCB might not be able to take too many more repairs in that area. The belleson the new owner bought looks updated and more rugged as well. Could use a lot more sockets and plugs so it would be easier to repair and take apart, but i figured i should just get it working first so the owner can decide what he wants to do with it.

    I did notice the parallel motoruns. Things are chonkers. Not sure if they are PSU related or in the signal path? Are they cathode bypass caps on the driver tube? Dont seem to be driver to power tube coupler caps since those are the audyn coppers.

    I find the amp to be a little harsh in the highs and i will fatigue after a few hours (but improved a lot with belleson...it was really hard sounding with the lab PSU powering driver filament). Might be the tubes i borrowed or maybe the SS rectification. It's tastefully warm, but not overboard compared to its big brothers.

    Hopefully we can compare it to a stock one and put some different tubes in
    [​IMG]
     
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  7. Hands

    Hands Overzealous Auto Flusher - Measurbator

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    I believe it's a 10uf cap for feedback loop, smaller one for interstage.

    Good idea on socketing what you can.

    In case you haven't seen them, here are a few old links from Changstar on the Super 7, a couple of which have some notes on modifications:

    https://www.changstar.com/www.changstar.com/index.php/topic,582.0.html
    https://www.changstar.com/www.changstar.com/index.php/topic,2358.0.html
    https://www.changstar.com/www.changstar.com/index.php/topic,7.0.html

    And there's at least one thread floating around on SBAF as well, but that's easier to find.
     
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