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

@debjit_g 

I have been using these mono's with Liberty Audio X-VOX, which is a parent company of PBN Audio but they are being replaced with Qualio IQ which will arrive next week 😁

Wig

@wig well, I have been meaning to try the Qualio IQ. Both Cube and Qualio comes from the same designer Grzegorz. They have a YT channel (Virtual Hifi) and the performance has been stellar. However, I was under the assumption the Qualio would need some amount of power to perform better. Have you spoken to the Qualio folks to see if low wattage 300b amps are a good match ? It would also depend on listening room and how loud you hear but I can't wait to hear your feedback on the Qualios with the Otomon amps.

@debjit_g 

Follow Greg YT channel on a regular basis 😊

No problem with Mono's driving Qualio and they are more powerful than my 100 Watts Class A/B KT88 Amp 😁

Wig

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.