With the Ear+ amp settling down very well, I decided it was time to swap the driver tube. Currently, it had a cheap and cheerful Sovtek 5751. When I initially bought the amp, I also purchased a single RCA Command Series 5751 from Audio Tubes. This tube could be described as having black plates, double Mica with a halo getter. This tube has probably 40 to 50 hours on it when it was last used with this amp.
A caveat, I loosely call this a review. I only have two 5751 tubes, and my comments are based on a single session where I listen to the same set on the same equipment. The only difference being the tube. The Sovtek has the date code 01 07. The testing conditions are:
- Music: (Small set) Missy Higgins, Coldplay and Jason Mraz.
- Source: Mac Pro with Apple Lossless format created with MaxCD.
- Maple Tree Audio Ear+ with Tantalum, Blackgate, Auricap and Caddock MK132 upgrades.
- Output tubes RCA 12B4A.
- Headphones: Beyerdynamic DT880 (600 ohm).
Vocals are a little darker and more recessed on the Sovtek. The overall balance seems to be more bass heavy, and the midrange is somewhat smaller and 'behind' the rest of the music somewhat. The sound is more engaging and warm. There is a real tactility to the guitar strumming and female vocals with the RCA compared with the Sovtek. With the RCA is is really a wonderful balance as it is more forward and present centre stage, where it should be. This also applies for the strings line on the track 'In My Place', much more delicate and what strings (synthesised or real) should sound like.
The bass seems to be much firmer, balanced and better controlled on the RCA. On the Sovtek, though the balance favours the bass more, it just feels like it is a little lazy. The guitar licks have more precision about the sound, and seems to be better controlled with the RCA. The very soft guitar plucking on 'Hardest Part' seems far more refined with the RCA and defined. With the Sovtek, you could hear it, but it just sounds more like a metal wire being plucked, rather than a guitar string.
Overall the Sovtek doesn't have the life or energy that the RCA does. It sounds a little flat and a little boring. The Sovtek brings the impression that the music is just music, whereas the RCA brings a dimension that is missing with the Sovtek that draws you into the music, where it is no longer just music.
The Sovtek currently retails for $19.95 at Tube Depot and the RCA Command at $94.00 at Audio Tubes. Is the RCA tube more than four times better? Do I hear four times more detail? Well, I am not sure it is four times better. It is definitely better, but the quality of improvement is very subjective. The pre-disposition that a more expensive product must be a better product, always comes into mind, and with such a price premium and associated folk-lore an, it is sometimes difficult to clearly define what it is that is better, and by how much. That is, to put a price on the improvement.
For me, the differences between the Sovtek and the RCA comes down to me wanting to continue listening and not stopping. The Sovtek doesn't really give me a compelling reason to continue listening. It is just not that engaging. I could compare the change in tube as the same as the HD650 on the Crack to the DT880 on the Ear (Sovtek). The RCA tube brings the Ear+ setup to a similar level of addiction as the Crack/Speedball with the HD650.
Would I pay the difference again? Yes. As far as tube life, ageing and the frequency that one needs to change tubes, I think that $94 is a wholly worthwhile upgrade. Would another tube cheaper perform better? Quite possibly. But until I obtain a few other samples, that question will remain unanswered. But for now, I will keep the Command in the Ear. It just sounds better.