Blue, huh? I haven’t tried them, but I would guess they’d feel right at home atop a Stellaris. 
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It’s really a fantastic pairing. My buddy borrowed mine and a few hours after I handed them to him he texted me “How much did you want for these?”
I wasn’t selling them.
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I haven’t been impressed with the Sophia’s in general.
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Stellaris > Utopia mystery: I own a Stellaris Special in location #1, and a “normal” Stellaris in location #2. Both with Takatsuki 2A3s, 6BK7B input tubes. #1 “default” rectifier is EML, #2 is (originally NOS) RCA JAN. On #1, I can’t null AC hum with the bias pots. It’s faint, but clearly noticeable. This happens also with the stock input tube, and with different rectifiers.
On #2, the hum is barely noticeable. No noticeable hum with ZMF Atrium open on either amp. The only way I found to almost null the Utopia hum on #1 is by putting back the stock 2A3s, which is a step back in other ways.
I’ve talked with Donald about this, his suggestion was that different 2A3s have different tolerances. My next step is to bring the Taks from #2 to #1 to see if it’s an issue with the particular tubes I have in #1 rather than with the tube version in general.
The almost vanished hum with the stock 2A3s indicates it’s not an environmental (cabling, electronics nearby) issue. In any case, I’ve done quite a bit of experimentation turning off various things, replacing signal cables, and more.
Any other suggestions?
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Have you tried bringing one of the amps to the other location? It might narrow down the issue, either power or amp related.
It’s very likely the Utopia with its 104 dB sensitivity, along with the Taks amplifying this hum you are picking up. While the ZMF have a higher sensitivity, that jump to 104 is quite a lot to introduce all sort of weirdness.
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FWIW I could never quite null out the hum on my Utopia with the Stratus, it was really low, but still present, I was using PSVane 2A3’s, and later LinLai.
While I can get most of them into the barely audible range the only tube amp I can’t hear the noise floor on with the Utopia is my Studio T, with its esoteric heater circuit.
My own designed 2A3 amp has regulated DC heaters, because one the Utopia I couldn’t null out all the hum with various hum pot configurations, on that amp I can hear a faint crackle instead.
The simplest solution is to add a resistor divider on the output (you need to be careful about the load it presents) the hum likely originates in the 2A3 heater, so it’s input volume invariant, so attenuating the output and increasing the in our volume in effect makes the headphone less sensitive and attenuates the hum.
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The two amps have been swapped before. No issues then, but that was before I had the Utopias. It’s quite a chore, they are heavy and they aren’t exactly next door to each other.
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Interesting however that the hum is much reduced (from faint to very hard to recognize consistently) when going from Taks to the stock Psvanes. Something to do with heater differences between the tubes?
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I was able to get the stock and ACME Psvanes as well as whatever NOS RCA 2a3s essentially silent with my Utopia. Linlai Globals always had a little hum to my ears.
I imagine there must be some inherent variability within the tubes themselves combined with a headphone that can easily pick up little noise iissues.
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The Utopia is absolutely a microscope into your chain, so if there is any noise, you will know about it. I suspect, if one of your amps is silent, it is down to one (or more) of your tubes just being slightly more noisy, which can happen due to tube variation. How and where noise can arise starts to get beyond where I can comfortably claim a good level of understanding, but through experimentation, I have found that tubes can be at fault, but also physical resonances. I’ve had some very interesting experiences with tube dampers, where one could even make it worse by changing the resonance of the tube to something that more closely coupled with whatever was causing it, and then adding another killed the resonance.
To that end, one of the most important purchases I’ve made for my Stellaris, and indeed, my chain, has been these chunky, Mapleshade tube dampers. They killed the last iota of perceptible noise floor from my tubes, firmed up the bass, and smoothed and extended the highs. Much better than the more common Herbie’s tube dampers (which are still better than no tube dampers, to be clear).
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This would absolutely be my suggestion before you do anything more. I would suggest bringing the whole tube complement from unit #2 and swap them into unit #1. If no hum, put back the input & rectifiers and try it again. If still no hum, it’s your RCA 2A3s (or one of them, at least).
FWIW, I have zero hum with Utopia + Stellaris, BUT I did have to return a NOS 2A3 for being incredibly noisy. Fortunately, my seller gladly replaced it and the new one is utterly silent.
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Both amps have Taks and 6BK7B at the moment, but different rectifiers, at the moment. I don’t think the hum in amp #1 is rectifier or input, because I put back the stock tubes and the hum stayed until I put the stock 2A3s. The only thing that remains is trying other 2A3s, including the Taks I have in #2.
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I think what ChrisNYC is trying to say, which some of us have also alluded to is the pair of Taks are the issue, to verify it would be best to take them to the other Stellaris. Quite confident we have narrowed down the 2A3 as the culprit here. Which happens, I also had a paid of NOS spring tops, one was noisy as hell so received a replacement. Second replacement set also had one noisy tube. It happens.
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Yes, thanks, that’s what I’m planning to do, take #2 Taks to #1 amp.
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Problem solved in practice, but why this worked is well beyond my understanding. To summarize, I had Tak pair #1 on a Stellaris Special (S); and pair #2 on a “normal” Stellaris (N). With Utopia, #1 on S showed a faint but consistently noticeable AC hum. #2 on N did not. When I put #2 on S, I was able to null hum with a small adjustment of the bias pots, Then I put #1 on N, and surprisingly, no hum.
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As crazy as it may seem, the physical movement may have knocked off some floaty bits causing the hum. This is more common with NOS tubes, but hell it could be any tubes. Good you got it sorted out finally!
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Anyone compare wa23 to stellaris ?
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What are your highest priority aspects when comparing the two?
wa23 is available with a short wait time. Stellaris is a year.
wa23 is black and gold. Stellaris is blue and silver.
wa23 has a fancier volume control and is designed to serve as a preamp as well.
wa23 uses 6C45 driver tube and Stellaris uses a 6n1p. Some people have a preference of one over another.
Both use 5u4g and 2A3 tubes.
wa23 has an outboard power supply. Stellaris doesn’t.
Woo is a company. Donald, I believe, is just himself.
I prefer the sound of the Stellaris but I’ve not had both in my home system and likely have a “team blue” bias, along with a general avoidance of Woo equipment.
You’ll likely be happy with either.
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I have not had both in my home, but I own a Stellaris and have heard the WA23 with my own headphones (but not my own source gear) on multiple occasions and really like it. They’re the two tube amps I enjoy the most, and they’re the two I’d consider buying if I were looking today.
Just a couple of small additions to @genefurit 's notes:
This depends on which attenuator you choose. You can get an upgraded, custom-built-for-Stellaris stepped attenuator on the Stellaris, but please keep in mind that this is a $2K option (at least at the time I built mine)
I personally am not a fan of the 6N1P, but really like the American alternatives (e.g. 6BQ7A), which also work in the Stellaris
Is Woo actually more than just Mike Woo and a couple of assistants? I think Woo might be a bit bigger, but not much. If I’m not mistaken, Donald (of DNA) also has a few assistants.
Hell yeah, you will!
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