As I mentioned above if not specifically supported, a 5AR4 could push the amp out of Spec if it’s designed for a 5U4G. I would check with the manufacturer.
Having said that Fuses generally have a lot of headroom, and we’re talking maybe 20% additional power being dumped through the circuit.
Rectifiers are the most commonly damaged tubes in shipping though, they are large and the wire bits inside can fracture during shipping even if the bottle is undamaged, I once received a Takatsuki rectifier intact with the getter rattling around in the bottom of the bottle.
I also had an NOS RCA 5U4G I received that I know was tested by the seller, that instantly died with a dramatic flash in the Amp, taking the Fuse with it.
Most NOS tubes are built to or exceed NOS spec’s.
All modern 6SN7’s I’m aware of for example are built to 6SN7GT specs.
There are some odd variants that never really existed, like 2.5V 300B’s sold as 2A3’s, and some tubes that modern variants of had variance issues 6C45Pi for example, though I think EH makes them any more and the NOS ones were somewhat notorious for spec variation.
Amps don’t always play nice with rectifiers, there are specifications with rectifiers for the maximum amount of Capacitance that can be in the circuit before the first Inductor, and a few modern designs don’t respect that. That can damage the tube on power on, though it depends on a lot of things. It’s one of the reasons Elrog insists on knowing what amp your going to put the tube in when you purchase it, so he can not sell to owners of amps he’s had previous issues with.
That makes sense some modern tubes reacty differently from NOS even though they are labeled the same model. I think I remember on the main tube thread where even if its the same brand and model # as the RCA 45 I got, the internals will be different either because it was near the last production. Tubes really are random, but they are really cool and fun to mess around with.
Yes tube designs changed over their lifetimes even for the same tubes from the same manufacturer, in some cases that changed the “name” 6SN7 became 6SN7GT later in production which just has a higher maximum plate voltage and current. But even within a single manufacturers 6SN7 there can be many different designs, and they sometimes changed frequently, it was a commonly used tube that was around for many years, so manufacturers did what they could to improve costs and reliability.
Then you have the weird “marketing” things that happened, LOctal was introduced as a base I think by Silvania, it was never popular outside applications where reliability was a concern (Loctal have pins through the glass and standard Octal sockets do not, so the solder joint can’t fail), but there are LOctal versions of a lot of common tubes. But for example the 7N7 which is just a 6SN7 with an LOctal base (which requires slightly different construction) and to differentiate the OG datasheets claim it has a 7V heater, though they later amended that to be the same 6.3V as the 6SN7’s. It was less common so there are less versions, though I received a matched pair of Silvania made 7F7’s (6SL7) that I picked up from Ebay that have very different construction to each other.
Have you listened to the Mysphere on your new Allnic amp yet? I’m listening to the Mysphere 3.2 right now after a week of listening to the DCA Stealth and the Mysphere 3.2 is blowing my mind of how next level it is. Right now, I am really gushing over imaging because it’s crazy freaking perfect with the 2A3 tubes I am using. It really reminds me of speakers where vocals are perfectly center stage, then stage left comes in, and then stage right comes in appearing from nothingness making the music come together so beautifully. On my setup, 45 tubes max out the Mysphere 3.2 timbre and midrange. My current 2A3 tubes take soundstage to another level for my Mysphere 3.2. I know we have a completely different audio chain, but I am pretty curious about how the Mysphere reacts to your Allnic HPA 300B amp.
In honor of @M0N 's very brief article, let me add another stellar option to pair with the mysphere…
Allnic HPA-300B - Balance, Smoothness, Control
Preferred Version: 3.1
What about the other?: Good, but 3.1 was better
Preferred Cushions: Standard
Listening Experience: In House
Favorite Tested DAC Pairing: LinnenberG Satie (only DAC used)
Confidence in Evaluation?: Very High
Overall Value?: Solid – worth my money new, used pricing unknown
3.2 (T frames)
Very good, but it’s missing that something. It’s obvious that the Allnic prefers the 3.1 more, although the performance on the 3.2 is pretty darn good. Restrained is the word I’d use to describe the experience.
3.1 (S frames)
Fantastique! Very well balanced, natural, and controlled with a dab of smoothness. Hard to put a finger on what’s missing really, very solid in all areas. Really great synergy, and smooth without lacking energy.
For anyone interested, Allnic is also making a 2a3 version of their HPA integrated to replace the 5000xl. Price wise, sits below the 300b and 10000xl so around $9k maybe.
