Eddie Current Super 7

The power transformer in my S7 produces a lot of hum noise even without load. I asked Craig, it seems the hose clamp is loose, I tightened the screw but no help. Is there anything I need to check either or I need to change with a better power transformer? Thanks.

 

Happily contributing to a thread nobody has any interest in, just in case anyone who sees this may have once been in my shoes and could offer guidance or share experiences.

I lucked into a Super 7 that has an issue, and I'm determined to fix it (and improve the amp.)
I don't know enough to tackle this myself, but luckily I live in a city with lots of options for people to work on it for me.

The current issue is that the left channel is louder than the right. I bought a 20k Alps potentiometer (ALPS 20KAX2 20K Ohm Audio Taper Stereo Potentiometer 6mm Shaft) since some Googling seemed to say it should work. If not, no biggie, I can order something else. Old threads recommended a DACT stepped attenuator but I was hesitant to get the Chinese knockoff because a) a month or three from China and b) the real ones were like $350 from what I could tell - worried the knockoffs would suck. Alps supposedly isn't the best, but hopefully it's serviceable and I was able to source one for $15. It'll be here in a week or so.

Previous threads on Changstar and SBAF basically walked me down the aisle of exactly what I need to do in terms of mods, so that was extra helpful.
I happen to have some VCap Elite Reference CuTF .1uF caps on hand for interstage caps, so that takes care of that.

I tried to track down the CDE SCRN224R-F motor run caps that @Hands recommended but they're nowhere to be found. @gaspasser used some SCRN224R (seemingly very similar) caps and was thrilled with them but sadly those too couldn't be located.
Both of these are huge and look like they're probably amazing and not meant for the task (so even better to me). @dBel84 recommended yet some other motor run caps that were 10uf 300vac but I couldn't source those either. The danger of trolling 6 year old threads on a dead website.

I ended up ordering some Jantzen Z-Silver 10uf 800V caps recommended in the same Changstar thread from like 6 years ago because I'm a sucker for clarity, resolution and soundstage.

I messaged Cine-Mag about their CM-13111 transformers which the internet research led me to believe might be a near drop-in replacement for the output transformers. We'll see what they come up with.

@MisterRogers was super helpful in another old Changstar thread with info on a mod for the driver tube regulator, so I emailed Belleson about their SPJ 6.25V regulator that's 317 pin compatible because I couldn't find exactly the right part on their website. He gave the part number but searching revealed no matches.

Add in a Nichicon 25V 4700uF capacitor and a 50mm, right angle, 3 pin male connector (still not sure exactly which one, but I'll find out), and that should be that.

In a perfect world, I would have experience with working on amps so that I could take this one step at a time and see what each improvement brings to the table before installing the next. Instead, I'm going to pay a local tech to do everything at once.

@purr1n has said that the Aficionado is just a better amp. I have one of those so I can compare it when the S7 is finished just for fun. The S7 is meant for a different system, so should be complimentary. One might wonder why to sink so much research and funds into a seemingly lesser amp and really it's to bring an old warhorse back from the dead, breathe new life to it, see what I can squeeze out of it, and hopefully get a lot of enjoyment out of it in the process.

I just like Eddie Current amps, and I wanted to take this one on as a project. Thankfully those who came before me left instructions and have already walked this path (and have surely since abandoned the S7 in favor of other amps).

Anyhow, whether anyone reads this or not, I'll update when things are done. I still listen to the amp though the left channel is louder than the right. I want to get a feel for the amp, and the ears seem to lessen the effect or get used to it a little bit after awhile. It's a good amp so far. I'm hoping to improve it further.

 

I tried to decrease the 6sn7 numbers at output stage, make it as super3 or super5, for super3 I found the noise level is lower than super7, also I like the tonal of super3 a bit more. Currently if I use a sensitive headphone, I usually put only two 6sn7. I know the resistance has been changed and it’s not the original design, but it gives more fun from the amp Thanks Craig for giving us this great design.

 

So a follow up to the post I made a few months ago, now that I've had time to get it all done, break it all in, and live with it for awhile.

Modifications:
OPTs changed to Mable Audio 300B OPTs (note these have changed after I bought mine, no guarantees on how the new ones sound. Mable couldn't get me the ones I ordered because of the change- I lucked out and bought some from a member here.)

Interstage caps:
.1uF +/-5% 600VDC CuTF VQSX-10J6
VCap Elite Reference

Feedback caps:
10uF +/-2% 800VDC Jantzen Audio Silver Z-Cap

Belleson driver tube regulator with Nichicon 25V 4700uF cap

Alps rk27 20kohm pot (I bought a Noble 10kohm pot too, but the Alps got installed for some reason.)

Anyhow here are some listening notes in the form of a kind of review-ish:


Excellent layering and separation, lots of front to back space for the instruments.
Vocals stay centered but everything else seems to fill in the surrounding areas quite nicely, including height presentation and little details that tend to sparkle or come in from behind the ears.

Bit of a warmer balanced tone to things, lots of presence, not fuzzy, easy to tell the difference between DACs so there's good transparency and clarity even with the bit of a splash of warmth over things.

I tend to use very neutral driver tubes as I strive for extended at both ends with tons of detail and hopefully good depth and width of soundstage without being too blown out or artificial, and without leaning too far towards the leaner or darker side of things. Even brighter drivers don't hide the warmth or bit of bloom this amp has, which is strange because the capacitor choices I made were done to bring the amp as close to neutral and extremely detailed as it would go. I think it must be the transformers I chose that give it that bit of a big, full, warmish hug with lots of density and weight.

My baseline is a modified Aficionado which in feedback mode is relatively neutral though not as clear as my Elekit TU-8800 (made by @tommytakis). Aficionado has EML Mesh power tubes and WE 396A driver (normally, those these things change sometimes).
Super 7 changes around, but is currently driven with a 6SN7WGTA Sylvania mil-spec tube, with some other Sylvania 6SN7GT and two pairs of RCA 6SN7GT powering it.

Overall I think the mods gave more body to the sound, more balls/cojones, increase the impact and overall heft on the low end, made the tone a bit sweeter and more engaging, and actually increased the overall warmth (I wasn't going for that and it's not something I chase, but it's there and it's ok with me since I don't feel like I'm missing out on any detail/resolution.) Bass texture could be better but it's kinda a high bar and really it's probably as good as most amps I've heard.

Associated gear:
pi2AES> Some Kinda Audioquest USB cable/Some Kinda fancyish Coax cable> ECP Walnut DAC/Jolida Glass DAC> modified Super 7> Black Dragon XLR cable> Verite Closed

This is a good foil to the SW51 because while I love the absolute clarity/purity of the SW51, it's a bit lean on the lower end and the stage isn't the biggest though the former bothers me more than the latter.

The inherent warmth of this amp and the denser tone with the heavier low end make these two amps excellent companions.
Sometimes you want apples, sometimes you want oranges.

It seems hard to me to find warmish amps that DON'T hide details. Black Widow was good at having an overall warmer presentation but didn't seem to hide anything that I could pick up on. That was weird but welcome for a solid state amp, and I think it did that far better than Jot 2. I've tried things like a McIntosh 4100 that were warm but smoothed and smeared (after a high end restoration even), and I can't hang with that. I think this Super 7 treads that fine line of having inherent warmth but still giving me as much as I can possibly pull out of the music for this particular piece.

Overall the mods definitely improved the amp, but I do wish I could have gotten it closer to the absolute neutral and viciously revealing beast I wanted it to be. It definitely has a flavor/color. It puts rose-colored glasses on everything and it's a beautiful sound, and I realize that's what many people want, but I'm a Neutralhead so I crave something else. I'm happy to have this as a flavor amp, but I'm glad I have others as my hyper detailed extremely neutral alternative amps.

Separately, it actually drives my modified Klipsch Quartets pretty damned well until I compare it with a 60WPC tube speaker amp that I have. If I didn't know what these speakers were capable of with more power, I could be totally happy with the Super 7 powering them. It's a stark contrast to trying to power them from my Aficionado. Both amps supposedly put out about 3WPC but all the mods must have added some watts to the S7 because it far outclasses the Aficionado in terms of powering these speakers, mainly in how the bass performs.
Elekit does even better than either headphone amp at 11WPC, but the crown may go to the 60WPC amp. We'll see.