300B Tube Amps with 15/16 Watts Per Channel?

my speakers Cube Audio Nenuphar is a single wide band driver. The manufacturer recommends amps with 0 or low feedback design, which will also have low damping factor.

@debjit_g Here are some more things to think about.

I’ve worked a lot with such drivers. Here’s a tip: supplement the driver with a subwoofer. If you can, also do something to prevent bass from getting to the driver! You’ll find the mids and highs to be a lot more coherent, especially at higher volume levels (this is due to the very audible effects of Doppler Effect distortion).

If the amp you use is an SET, it will benefit quite a lot from not having to reproduce bass as well. SETs really have troubles making bass anyway due to the requirements of the output transformer; it gets technical but in a nutshell this problem stems from the need to prevent distortion caused by the output transformer itself (BTW a PP amp does not have this problem). As a result no SET can make full rated power at 20Hz; if they did the output transformer would be the size of a small refrigerator!

This bit could be easily taken care of by the use of a smaller value coupling capacitor in the SET prior to the output section, with the intention of rolling it off at 60Hz or so. We’ve done things like that for our customers before (although we make an entirely different kind of amp known as an OTL)- so it might be worth it to talk to whomever makes the amp you settle on about that.

Since your thread title doesn’t seem like you are limiting yourself to an SET, IMO/IME your amplifier investment dollar will be a lot better served by a PP amp and there are PP 300b amps like the excellent Spatial Audio amp designed by Don Sachs.

I’ve been investigating SETs since the early 90s; they have quite a few problems which really limit how they can be best used. If you are in a normal room for example, unless your Cube driver is horn loaded, it does not have the efficiency to really show off what an SET can do with the power you ask about in the thread title. Typically high efficiency extended range drivers like the Cube might be 99dB at best (unless horn loaded) and since SETs only have 20-25% usable power, you really only have about 4 Watts to play with.

To give that some perspective, my speakers at home are 98dB and 16 Ohms (nearly the same as yours), so very easy to drive, and I’ve found that they need a good 50-100 Watts in an average size room. In this way the amp doesn’t have to work hard at all and due to the extra cleanliness of the sound, its very natural to use more amplifier power. If I put in a lower powered amp like 15 Watts, the fact that it is more strained is immediately apparent compared to the more power amp.

@atmasphere thanks for all the info. That’s helpful and appreciate taking the time to educate some of us. I don’t think the Cube drivers are horn loaded but they do have a whizzer cone. In EU they are typically paired with Tektron 211 PSET amps at shows and the sound is sublime. I have seen them powered with 3/4 watts 2A3 SET in small rooms but I don’t think that will work in my situation as my room is a open configuration with lot of volume. Have gone through some amps, like FW SIT3, Pass X25, LTA UL and some other Class D but in all cases it seemed to lack dynamics until I paired it with a LM 805IA. This integrated is also heavy modified and it sounded very good but the only issue is this amp is easily prone to noise and ground loop issues. So in my experience, this speaker needs some bit of power depending on the room situation. I am now trying to see where can I go next. I know for sure getting a Tektron PSET would be an end game for this speakers, so I am trying to explore other options like Otomon which apparently seems very nice as well.

@debjit_g  There is an old customer of mine who has a prototype pair of the design used for the Blackbird amps that Spatial audio is producing.  PP300b and they produce about 24 watts/ch.   He has one of the Cube speakers as I recall and the amps drive them with ease.  So I am sure a well designed and preferably fully balanced PP 300b would have no problem.