Nice! I really liked the Utopia and Senns with it. I wasn’t super impressed with the VC.
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Definition of Synergy, it’s amazing how differently it presents on the Stratus.
It’s about 3.5W out total. But I’d guess based entirely on the quoted output impedance for low impedance out, the transformer is about 12:1, probably 17:1 on SE/low gain, so you’ll see a lot less than that into 32/64 Ohms.
So anything 150 Ohms and greater you’ll probably want on the high impedance setting (IEC) and that only works through the 6.25 socket. XLR is always low impedance/High Gain.
Doesn’t really surprise me.
But remember it’s a logarithmic pot, so half volume is about 10% signal. Having said that tube amps increase in distortion with larger signals, and while it would get the Susvara or 1266 loud enough for me, they were not a great match for it.
Some of the tubes people roll for the pre tube have a lot less gain than the 6n1p, because for a lot of headphones 3.5W is a bit much and you end up at the very start of the volume dial.
And FWIW the Recifier and powertube IME have more impact than the pre tube on the sound.
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Yeah I will probably stick with the 1/4" output for most of my listening since you lose the gain and output impedance controls on the 4 pin xlr jack. And I couldn’t hear much of a difference with the different modes on the xlr output.
I thought that the IEC settings made things like Atrium and Verite closed sound a bit too muted in the top end so will need to experiment with that more but I haven’t found a case yet where I outright preferred the IEC setting to the low one. Maybe with 800S it could be better.
I did find that the volume knob is quite sensitive especially for utopia so rolling the pre tube as you suggested could help. I don’t plan on rolling any of the other tubes since it’s just a demo.
There shouldn’t be any, the only thing that has any effect is the SE/Bal switch, and all that does is change which pin on the socket is ground. The fact it does anything is just a function of the way the 6.25 is wired.
What rectifier is in it?
It’s worth noting that low gain actually has a lower impedance out than high gain (about 3.5 Ohms rather than 8), which can be useful with some easier to drive planars, I preferred SE low gain on the D8KP for example.
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I think it’s a 5U4G winged C
Do yourself a favor and pick up an RCA 5U4G (I think I paid $70 for mine though it was a while ago). the winged C it ships with is IMO terrible, and should be the first tube to go.
Makes the amp much slower than it can be. RCA greatly improves the speed and incisiveness. And without spending a ton it’s a huge improvement.
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alright I’ll look into it. If it’s under 100 or so I don’t mind trying it out. Just don’t want to spend a fortune on tubes for an amp I have to return 
.
Looks like it’s 170 on tube depot. TubeDepot.com | RCA 5U4G
There are also 5u4gb variants but I assume those aren’t compatible
Yes always an issue.
On the plus side 5U4G’s are very common rectifiers, and the RCA is about the best of the not silly expensive tubes, so having one around if you pick up another tube amp, can sometimes be nice. I probably own 5 of them.
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GB is just the higher powered version, it’ll work, but you really want the none GB version.
What’s Brent Jesse’s price?
It’s also a common enough tube I’d take a chance on EBay.
Buy this
5U4G blackplate RCA made for other brands, ST shape, getting very scarce.
New old stock in white boxes. This is the classic coke bottle shape (ST) rectifier tube. These gems are exactly the same as the RCA ST shape 5U4G above since they are RCA made, except they have other brands (or no brand) on the label. Watch these babies, they are going fast as any G type 5U4 is getting scarce and vintage NOS versions are in high demand! If you don’t need a designer label, you can get the same RCA vintage 1940s to 1950s quality for less! Stock up now, this batch is probably the last at this price!
$79.00
In Stock
Or this if you don’t mind the cosmetics
5U4G blackplate RCA “Butt Ugly” tubes, ST shape, used
Used? NOS? but test like NOS in white boxes. Man these are uglier than Bertha Butt and the Butt Sisters! Scratched bases, tilted glass, oddly shaped getter flash spots, less than sparkling glass, they are just…well…Butt Ugly! This is the classic coke bottle shape (ST) rectifier tube. These are tested as new old stock, but they are truly not for the squeamish. Some with other brands on the label but are RCA made. Exactly the same RCA tube as above, fully guaranteed, save big time on this stock of buttheads!
$69.00
In Stock
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I went here and searched for 5u4g http://www.audiotubes.com/audtube.htm
I’m seeing up to 170 for a JAN RCA and as low as 70 for a “butt ugly” rca
Edit: Just saw your post above, thanks! And ordered the non butt ugly one
Agree here. Wasn’t a fan of the GB, the G was definitely better.
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You can get a decent RCA 5u4G for $50 or less, $170 is way too high.
Edit: check out Andy at Vintage Tube Services, or go with eBay from a reputable seller. They are plenty of them available, Sylvania or Nat a union are good alternates too
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Thanks for all the help regarding tube rolling and for those of you who reached out directly. I ended up ordering one a bit impulsively but sounds like it’s shipping tomorrow and should be here in a few days.
As for pairings with the Stratus I just tried 800S and wasn’t really blown away it sounded nice but I didn’t get much more body or warmth that I would like with that headphone. Certainly no slouch but just didn’t tilt it in the direction I’m looking for. Same story with the 580 Precision, it still sounded a bit too lean.
Next I tried the 650, actually Orrman’s old pair, and that sounds great.
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Just not what it’s about, DNA amps are pretty much straight neutral, tubes are there if you know what you’re listening for, but it’s not trying to be warm/rich.
They do tend to be on the relaxed side.
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Gotcha and that’s definitely what I’m hearing. I do enjoy that sort of presentation but just trying to find which headphones I like with it the most.
Presentation reminds me a bit of the WA33 but maybe a bit more laid back
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WA33 is a lot more detail forwards, and generally aggressive.
But PP amps like the WA33, have almost no 2nd harmonic content.
The whole neutral sound is very common in higher end tube amps, there are places like Decware that specialize in the more full bodied sound.
The dryer sound is probably more prevalent in headphone amps, just because your using so little power, at 700mV on a 2A3 your probably getting better than -70dB for the second harmonic distortion, use the same amp to drive speaker, and it might creep up to -40dB.
Transformer choices are also very critical.
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The 5U4G arrived today after a bit of a shipping delay as it made a trip down to Puerto Rico first . Sounds good out of the box but will let it run for awhile just to get some hours on it. The material that came with it recommends about 50 hours minimum for this tube.
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I’ve let the RCA 5U4G run during the day since I got it and have done some listening along the way. It didn’t sound like it changed much but I also didn’t take any notes as I listened during the burn in. I just did a bit of a comparison between the stock and the new RCA tube and the changes are not exactly what I expected but it does seem fairly noticeable comparing notes between the same set of tracks:
I’ve used these tracks for comparing dacs as well so I’m pretty familiar with them.
I did this comparison with the Atrium not because it’s the most resolving headphone I have but I’ve been using it a lot recently and after reinstalling the mesh over the driver and swapping the rectifier I found that it was more enjoyable off of the stratus.
Starting with the RCA everything sounded nice. I liked how I could hear the decay really clearly in all the tracks, especially in Let Me Down Easy and Two Life. The reverb of the cello in the second track was really cool. It also sounded fairly punchy but nothing sounded muddy. Separation was pretty good for atrium as well as that is something I’ve disliked on it in the past. The only complaint I had listening to these songs was how some percussion like cymbals or it sounded like a tambourine didn’t have enough sizzle to them but that’s more of an atrium issue I think not so much the amp or tube.
Switching to the stock 5U4G winged c and the tonality sounded the same but as I went through the tracks it sounded like the decay was abbreviated sort of how a planar decays vs how a dynamic can decay. Also on the track Blood in the Cut the sound became muddy when all the instruments came in whereas I didn’t have that issue with the RCA. My impression of the stock tube is that it’s a bit softer overall and struggles a bit with separation and decay but is otherwise pretty good. I wasn’t expecting to hear differences in the length of decay but was an interesting difference and I prefer a longer decay for these tracks.
I don’t have any plans to roll 2A3s at the moment but if I have the amp for awhile longer I might give that a try.
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I may be in the minority here but when I added the EML mesh 5u4g, I felt like it gave me some of those micro details, better separation, I felt an improvement in stage depth and maybe even some of the sizzle you’re speaking of.
Also I feel some headphones responded better than others. Utopia was much more responsive than something like the 650.
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