Almarro A205A MkII
During the first wave of SET amps I acquired both a 300B and a 2A3 amp. When the worst SET fever got over, I quite soon settled for small power (10-20 W) push pull amps, EL84 and 6V6 especially, and been happy ever since. At their best, cleverly executed small power PP amps combine much of the delicacy of SETs (even if not quite reaching their tonal richness and sensitivity) and consistency of more powerful PP amps (40 to 200 W range). What I've got with the small power PP amps, but didn't get with the SETs, was lack of somewhat uneven and unpredictable performance. So it was with curiosity that I returned to the realm of SE amps in the form of Almarro A205A.
Prior this review I've reviewed two pentode SE amps, one with a KT88 and the other with a EL519. Apart from a few headphone amps, the Almarro A205A was the first single-ended EL84 amp I've tried, although they appear to be everyday food for DIY nuts. Of the commercial actors, at least Mastersound makes a similar amp: a review of their Piccolo is forthcoming.
The Almarro A205A's compact size (11.4" W x 5.2" H x 9.6" D) and the fact that it has only 2 line level inputs and a toggle switch for the input selection, suggests that Almarro has designed this amp as much for a computer table than for the hifi rack. The fact that it has a headphone output speaks for the conclusion.
The input/driver tube is EH's 12AX7. But is the EL84 (6BQ5) pentode or triode trapped? The fact that Almarro names the amp as a pentode integrated and specs the output power as 5wpc, points to pentode operation: in a triode mode one EL84 should give only 2-3 Class A watts for some acceptable level of distortion. The OP transformers are fairly moderately sized but as far as I can judge, sufficient for the purpose. The frequency response is not given. The total weight is 16 lb, ie. 7,3 kg. The amp is available in flat black and flat grey finishes. It looks military and elementary, and I liked that.
But what sort of amp the A205A is? Almarro says it's a single-ended pentode integrated amplifier. What makes it an 'integrated' amp is, presumably, the headphone output and a basic preamp section with a passive pot. However, in my head the A205A falls in the category of power amps with a pot rather than an integrated. I did try the A205A as an integrated, and although it provided quite a satisfactory musical performance with the Audio Space LS3/5A monitor, if the best sound refinement is searched for, then, I think, the A205A should be married with a quality active tube preamp. I'm sure it would also help the A205A driving an insensitive loudspeaker, no reason or not.
So I'd say that the A205A functions best when employed as a power amp, and with rather sensitive loudspeakers. That doesn't render the pot superfluous: it's fine for adjusting the noise level, if any, and it's fine for minor EQing if used in an active multi-way system. During the review, the A205A spent most of its time as a high pass amp (>500Hz) for my AGA/Lansing eight cell HF horns, certainly sensitive enough for the 5 watts of the A205A. The horns are so sensitive and the Behringer crossover is so noisy that I kept the pot in the clock 12-13 position.
The A205A has both 8 and 16 ohm outputs for the loudspeakers, and even though the horns are 20 ohm designs, I liked the 8 ohm setting best. Above all, better control. In that capacity as a high pass amp the A205A did great work sonically, more or less equalling to what I've been able to obtain with the small power EL84 and 6V6 PP amps, and in some respects even exceeding their level, reminding me of my earlier observations regarding the differences between Class A single-ended amps and Class AB or even Class A push-pull amps.
However, I don't want to do detailed verbal analysis of the sonic performance of the A2025 - so much been written of the subject before. I just want to mention this: when I replaced the default (Sovtek) tubes with NOS Mullard EL84s, what a great difference there was and for the better, especially in terms of sophistication and airyness of the sound. The originals weren't bad but the Mullards were really superb in the A205A. So much so that after the experiment I became very keen on comparing the A205A/Mullard combo with any 2A3 or 300B amp I could get hold of, not so much to know which is the best but to learn more about the major sonic differences.
Well documented is also that the A205A provides a suitable platform for various mods thereby increasing the possibilities to finetune its sonic character. A very promising tiny amp indeed.
Almarro A205A MkII, 1650 euro