My favorite in the Golden Gate 2 is still the Western Electric 422a. It loses to the Acme 274b in scale and soundstaging though. I've been eyeing the Western Electric 274B as it's supposed to have a bigger expansive soundstage.
AD1s haven't surfaced yet. And yes, I got a set of 274A incoming as well as an adapter. Unfortunately, the adapter is coming in from China so the long wait begins anew.
I find myself using valves with B4 or P8A (AD1) bases almost exclusively these days.
Just saying. I'd actually prefer a B4 base in the Lampi as the default! Not sure I'll bother but I did swap out the original for an Audio Note UX4 silver base.
New rectifier, and I think these are tricky to get hold of, first impressions are very good. I believe this is Mullard, it's a UK one and made for the military. This is a very high quality rectifier. I will try and review later. I've had no luck WHATSOEVER with cheap rectifiers, of which I have loads now. I also got the later version of this and it wasn't good either. Potato masher etc. are nowhere near ACME 274b, this valve and GZ34 metal base. My current advice is to avoid cheap valves. I've tried a lot and all are way behind. Running with the KR242 in a GG2, in case you are interested.
Still interested in opinions around U52 brown and black base. Anyone run these older valves?
Ah should have been clearer on the adapters sorry, UX4 (4 pin) rectifiers to octal.
So first impressions of the UK military KV378! I've not done extensive comparisons with the ACME in a long listening session but here's what I've found. I also picked up the new version of this, which is terrible and not worth bothering with, so if you're looking for one be careful to get it right.
Soundstage
Expansive and not lacking at all. On the cheaper valves I find they sound smaller and more compressed. None of those issues here. Sound is diffused properly making the speakers disappear. This appears to be the equivalent of the ACME 274b which is the best one I have in this regard. The GZ34 which I reviewed earlier is flat in comparison to the ACME and this.
Sound
The biggest difference with this valve compared to the ACME is the sound in the range of the vocals, snare drums and cymbals. It has tremendous clarity and is the most real sounding I've heard. I find a lot of valves can warm up the sound (just like the GZ34) i.e. distort. This can be good but often results in vocals sounding really good, but drums sounding a little washed out and not as real. The valve gives the most accurate sound I've heard with tremendous separation and decay. There is no blur whatsoever. Reverb on vocals becomes highly accurate and noticeable. This is like a window into the original recording. The valve isn't bright per se but this is it's stand out quality.
Bass
Deep bass is the equivalent of the ACME. Upper bass is more accurate but you lose some of the valve magic. I actually like the soft kick drum sound, which isn't exactly accurate but is a personal preference.
Summary
This is a stunningly good tube. I have heard that some of the older Mullards are warm but this is anything but that. The ACME is also superb so this is not a criticism. The GZ34 is entirely a different type of sound trading soundstage and clarity for warmth. As with all these things it will come down to personal taste.
Thanks Adam, I think I must have about 50 to 100 hours on it by now and the sound hasn't been changing much. How long are you talking? What changes did you see with the sound when it was complete?