Does this mean your tubes turn on and music flows through as the volume knob changes from 0+
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Is it OK to use a 5ar4 in a Stratus? When I read @andrisā writeup of his time with the Stratus, I thought he mentioned that Donald had to build a special 5U4G/5AR4 switch, and that was only available on the Stellaris?
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So, Donald said that a GZ34 is okay to use even without the switch, but that the circuitry is not optimized for it, and therefore, might not be dead quiet. I felt it sounded really great (and still very quiet) even on the demo unit with no switch. I had to turn the attenuator all the way up to get any hum, and it was super low, even then.
Now, as for the switch, Donald says that the tubes it allows the amp to actually be optimized for include GZ34, GZ37, and 422A.
Now I donāt actually know whether or not 5AR4 falls in that group of either okay without switch or okay with switch. I know that these types of tubes are often interchangeable, but not always. For example, several amps I know of can take a 5U4G or a 274B, but the Stratus / Stellaris cannot take a 274B at all (with or without the switch).
I strongly encourage checking with Donald to explicitly tell you whether or not 5AR4 is okay to try.
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I had my Stratus upgraded with a rectifier switch that allows 5ar4, gz37 and others on top of the normal 5u4g stock. One can get a custom adapter for 422a tubes which switches two pins up from Deyan on headfi.
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5AR4 is the same as GZ34. I think the former is the US designation and the latter is the UK/European designation.
Itās good to know that Donald is willing to provide the switch on the Stratus.
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Okay, cool - good to know! I just didnāt want to give a thumbs up without being sure myself. I appreciate the clarification 
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One minor point of clarification, one will need to specify which indirectly heated rectifier configuration: GZ34/GZ37 (cathode pin 8) or 422A (cathode pin 2).
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Might I suggest that we move or copy the preceding 7ish posts to the DNA thread? Not because they donāt belong here, but because this is great information that should be accessible in the topical thread for posterity. 
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While on the subject of rectifiers, people may want to consider the 5U4GB tube. I tried this tube following discussions with Donald, where I indicated to him that I might sometimes prefer the sonics of indirectly heated 5AR4 over directly heated 5U4G. Directly heated 5U4GB has a lower forward drop that is closer to 5AR4, what some refer to as less sag. Iāve found 5U4GB to hit a nice sweet spot of bass extension/speed/tightness/detail while maintaining the integrity of the rest of the sonic presentation. To my ears, 5U4G can lean softer and not as tight and fast in the bass. 5AR4 addresses those, but can sound like there is too much gain.
For those wanting a bit more tightness whilst preserving directly heated magic, 5U4GB might be the best of both worlds without needing to alter the ampās stock form. Note that 5AS4A appears to be an equivalent substitute.
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@Earmuffs can we get a post comparing your stratus to the ampsandsound amps? I know youāve had Mogwai, Bigger Ben and the nautilus. Iād like to know what you feel the similarities and differences are.
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Thanks for the interest. Since I have bought the Stratus Iāve been meaning to do a long write up of the Stratus and Nautilus using them as companions.
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Anybody have some used 2a3 tubes they would like to sell?
The used Acme 2a3ās I bought ended up having a loud repetitive click in one tube so those are sadly being returned. Iām thinking either buy another pair from woo audio for $600 or try out an EmL 2a3 single plate or mesh plates for around $750? Itās hard with the linlai Elites being only around $525 too.
I really liked the acmes as they had amazing clarity over the stock tubes and compliments my Sylvania 2a3ās as they are a much more warmer tube. Not the same airyness as the acmes. Nice to have both.
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I have 1 Acme 2A3 (I broke the other one) Iād sell, a set of 4 Gold Lions, and probably a pair of PSVane 2A3-Tās.
The LinLai Elites are similar to the PSVane Acmeās, a little thinner sounding, but there isnāt much in it.
I havenāt tried the EmLās.
Iād like to try these https://shop.best300b.com/collections/tubes/products/copy-of-kr-2a3 ,I have their 5U4G, both the Anniversary and the RK Special Edition which I love, along with matched 242ās PX25ās and T100ās, all of which impressed me.
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I was looking at those KR 2a3ās too. Kr is very confusing as there are a few modifications to each of their tubes. Those KRās have circular getters vs. here at tubesusa.com have rectangular ones. Usatubes still have a few Kr tubes in stock atm but really thinks the EMLās are more preferable especially in reliability. I think Iām going to grab a pair of the solid EMLās as well as an acme or linlai pair too. One of these days it would be nice to try some RCA mono plates too but those are bookoo big bucks level.
There is an old 2A3 tube rolling thread over on SBAF, that compares the Acmeās to the Single Plate RCAās quite favorably after a few hundred hours of burn in.
The KR Ricardo Kron Special Edition 5U4G is my favorite rectifier so far, the only way I know of to buy one is internationally from best 300B. I recently got a small fortune in KR tubes included with a purchase, but no 2A3ās, but the overall sound of them has impressed, and Iām tempted to splash out on the 2A3ās.
I do know Donald likes the EML rectifier, I havenāt heard their 2A3ās.
These tubes are at price points I donāt like to roll, but I have two amps that take 2A3ās, one has a matched quad of Acmeās in it, on the Stratus I replaced the Acmeās with the Lin Lai Elites when I broke one of the Acmeās moving the amp (donāt ask).
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How do the PSVane 2A3-T compare? You mentioned you might sell a pair, but did not mention them in the sound comparisonsā¦ 
Noting what is on the EML website - 2A3-Mesh Emission Labs Data Sheet
Where 2A3-Mesh is not advised:
- Mesh tubes used as output tubes in a separate pre amplifier, or used in a head phone amplifier, may occasionally cause a spurious noise. Though this is rare, it is not a tube issue when it happens. Otherwise we recommend the EML solid plate tubes.
This warning has kept me from considering them but the solid plates might be great.
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I like the idea of mesh but the seller stated the solid plate as having a fuller sound and better for all genres of music.
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They are a middle ground, a step up from the entry level PSVanes that came with my Stratus, increases in resolution, and an overall cleaner presentation, but the Acmes are still a significant step up from that.
Having said that IMO you get a lot more value from spending on a Rectifier in the Stratus than you do on the 2A3ās.
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Obviously not the same tube, but really happy with the KR KT-88s in the Bigger Ben.
Also Grant Fidelity has a Black Friday deal on the Lin lai Global Elites.You have to pay $5 to see the pricing, if you spend more than $350 youāll get your $5 back.
Might be worth a look
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