EC Studio Junior (not AF)

Discussion in 'Eddie Current' started by purr1n, Mar 2, 2019.

  1. purr1n

    purr1n Finding his inner redneck

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    I have the EC Studio Junior pre-production in the house to help Craig troubleshoot some issues. This amp is configured with 300B tubes and uses feedback from the tertiary winding of the output transformers. The most significant difference from the AF is the output transformer. The SJR transformer is a custom deal, not the Cinemag used in the AF. It was based on a pre-existing transformer (quite pricey). This original transformer was taken apart, disassembled, and dissected to discover the secrets of its core laminations. The tertiary winding (based on an old McIntosh design back in the day) was then put into this transformer. I've heard both the original and tweaked with tertiary winding version and I can say that have the same or similar sound. The experiment was a success.

    The AF transformer is slightly drier. The SJR transformer is slightly wetter and richer. A most important change with the SJR transformer is the availability of 4-ohm and 8-ohm taps. The headphone out uses the 8-ohm tap only. The output impedance from the 8-ohm tap is probably 2-3 ohms, and the 4-ohm probably just a little over 1-ohm. Don't quote me on this. These are just predictions. The speaker outputs are Neutrik Speakon (the best thing ever - used by pros - screw you audiophiles with your lame gigantic lugs and banana plugs that tend to break shit more than offer better sound). Pin 1 +/- are the 8-ohm taps and pin 2 +/- are the 4-ohm taps. The reason this transformer has a 4-ohm tap is because of the JBL 4698Bs which Craig owned for a while: the woofers are 4-ohms. Necessity was the mother of invention.

    The SJR can be ordered with 2A3 tubes instead of 300B. Standard, the SJR comes with 300B and feedback. Those who prefer a bassier, thicker, and heftier sound a la Amp&Sound will want to order it without feedback. The SJR never gets quite as thick and rolled sounding as the Amp&Sound stuff with or without feedback. I like the transformer in that it doesn't have overblown mid or upper bass, but it packs a ton of punch just below the mid-bass and is full-bodied in the mids. This effect is exaggerated in the non-feedback version. The non-feedback version has quite a punch! The downsides are less controlled and articulate bass and slight high-end roll-off. It's a 300B after all and this is how 300Bs sound. The good thing is that the sound isn't soft. The AF 2A3 is a little softer and less punchy, feedback or non-feedback.

    The feedback version of the 300B is what I would recommend. This approach tones down the 300B sound and results in what I would like to say as "the best of the 300B without the worse of the 300B". The resultant sound is very stately, controlled, perfectly damped. In comparison, the mids and highs of the non-feedback AF 2A3 tended to be a bit jumpy and overly lively (this is more of a transformer issue than feedback issue). Nothing is for free of course. The feedback does constraint the soundstage and immediacy factor by a tiny bit, but with the 300B, I find that the positives outweigh the negatives - this keeping in mind that I am not exactly a 300B fan.

    I am uncertain if balanced inputs (iso transformers in the chassis) will be offered. I'll check the metal work next time I am in the lab.
     
    Last edited: Mar 2, 2019
  2. EagleWings

    EagleWings Friend

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    @purr1n , does SJR's wiring allow for a FB/NFB switch like what @JK47 did for his AF? If yes, would Craig be willing to do it.

     
  3. purr1n

    purr1n Finding his inner redneck

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    Since the SJR comes standard with feedback and the design was never to have the tertiary outputs used for an SE line out like on the AF, there are no holes in the back plate that can be repurposed for a switch. I can check the back plate to see, but I am not aware of Craig wanting to offer such an option.

    The AF feedback thing drove Craig nuts. Not my fault. His own doing by saying certain things to the wrong person, who in turn blabbed to the public about certain things Craig said to him in confidence (implied, but young customers can be impetuous and dumb). You know, that comzee guy who berated me of "intentionally nerfing the AF because the Jupiter caps and feedback mod were not publicly available options". What happens is that Craig wants to be a nice guy, but then bitches to me about non-original owners (or even original owners) wanting him to do mods. I believe that consumers should NOT be given options for a product - that those different configurations should be entirely different products altogether. The reason is that EC, or even Schiit for that matter is not Dell or Audi, with sophisticated just-in-time supply and manufacturing chains.

    I would hope that the SJR 300B just comes in one package: with feedback. Of course, now that I say this, people will now call and ask for the non-feedback mod. I'm hoping Craig will have now learned this lesson and just tell people "no" to no-feedback, or "buy Woo".
     
    Last edited: Mar 2, 2019
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  4. allegro

    allegro Friend

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    @purr1n which 300B tubes were you using? Are the lower cost new tubes like Genalex Gold Lion PX300B satisfactory?
     
  5. purr1n

    purr1n Finding his inner redneck

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    Yes, get cheap shit. I was and am using EH 300B cheapo specials. Sounds damn good. I like the JJ 300Bs quite a bit too, they are smoother (maybe a wee bit) but more lively. Great tube amps will sound great with decent tubes. There is no need to buy $2800/pair Albacore Tataki or $1600/pair WE Retcon tubes. This is why I love Craig's (and also Donald's) amps. They just sound good with whatever stuff you plug into them.

    I do immensely dislike the TJ Full Music tubes though. Their construction is shit, the metal creaks and pings when the tube is heating up, and the sound is way too bloomy and romantic, but hey, people love that stuff. The fake metal mesh Chinese tubes also sound like ass, like ass caked with dry shit.

    You can't go wrong with JJ, EH, Genalex, etc. The EMLs are very nice, focused and rich, but have gone up hundreds of dollars in a few years. FWIW, I have no intention of spending more than what JJs or Genalex cost. So sick of listening to tubes. I listen to music now and don't GAF about tubes.

    BTW, gain on the two triodes on the driver tubes will be important for channel balance. Less an issue with 300B since gain is low on 300B. The driver tubes are for the gain. The 396A is fairly high gain, so easy for stuff to be off.
     
    Last edited: Mar 14, 2019
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  6. Thenewerguy009

    Thenewerguy009 Friend

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    I always wanted to ask, but can't the RCA inputs just be removed & replaced with balanced inputs if you just want one set of XLR inputs & no RCA?
     
  7. purr1n

    purr1n Finding his inner redneck

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    Just confirmed with Craig on the phone. It will come with only unbalanced inputs x2.

    The amp is still being worked on. Final tweaks to eliminate some intermittent noise which seems dependent upon the state of the power lines. The metal is in.
     
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  8. fp627

    fp627 Friend

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    Sounds like the amps are "largely" the same but roll transformers?

    2 other questions:
    - @purr1n Given your distaste for config/customization options, is there any way to have both feedback and no feedback via a switch or something similar? Ex flip switch to connect or bypass resistor from output circuit path? On the flip side I can also totally see how this can go very wrong via user error.
    - Similarly, while I'm not a fan of excessively chasing components/tubes/etc, I'm still curious if different caps and other components will make a "significant enough" difference in this new amp (lets say more than switching between copper only and silver coated copper RCA cables that are otherwise similar)? If so, are components something that can be spec'd at time of build/order? (Excuse me if this 2nd question sounds dense after mentioning "AF feedback", but that isn't one I'm familiar with, if it was just a case of a bad customer or something much more of a headache.)
     
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  9. purr1n

    purr1n Finding his inner redneck

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    Yes. I believe a few users installed a switch or had one installed by Craig. It's more than just bypassing the two feedback resistors. Without feedback, there is the addition of a cap and resistor paralleled for the cathode bypass of the driver tube. So it's kind of a PIA for Craig. He's done the mod for his customers but will not do it for people who did not buy the amp from him.

    The interstage cap is worth playing with but which one is a matter of preference. With the feedback, I think the interstage cap differences are less. Audiophiles are strange creatures and once the cap rolling option is available, then cap rolling suddenly makes "massive" changes. What makes big changes is the output transformer.

    The other caps, cathode bypass on the power tubes. Other people have rolled different ones and values, for the worse. I'd stick with what Craig did here.
     
    Last edited: Mar 16, 2019
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  10. songmic

    songmic Gear cycler East Asia edition

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    Has anyone bought and listened to the Studio Jr (preferably, the default feedback version)? It's been quite a while since it was announced but I'm surprised no one has written a review or impression of it. Or is it still being built and the first batch has not even been shipped out?
     
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