Quote:Steve,
Have you thought about an EL84/6P15P tube amp with ZMA type power supplies? Or applying any new insights from Torii Jr? What about a 6SN7 or 6SL7 input tube? Or limited runs of a special edition? Just curious about where this amp can go next. Until then, I will keep enjoying what I have. Happy listening.
Easily I could hop up a zen amplifier with more power... but the price would be the amps ability to drive nearly a dead short... which is what is at the heart of it's bass performance. Not to mention the clipping would change from wonderfully forgiving to ugly and the midrange would get harder. You can apply the ZMA power supply approach, albeit properly tuned for the 2 watt amp, with good results, but then you loose the ability to voice the signature with different rectifier tubes not to mention that the rectifier tube protects your amp from basically anything serious enough to hurt it, like nearby lightening strikes, etc. That means that your amp will likely never fail since you can replace the rectifier tubes as needed yourself.
If you compare the ZKIT1 circuit board version which uses two UN4007 fast recovery diodes in place of the rectifier tube, the sound is still good but different. The highs are more sparkly, and the amp has more power due to less voltage drop, and no issues with the bass. Probably more consistent since you can't change it like you can with rectifier tubes. Still, the midrange potential in a good rectifier tube is priceless. I can remember many occasions when auditioning headphones for example, where the choice of rectifier tube was profound enough to be the make it or break it factor that determined if I liked a particular set of phones or not. Put better, it determined how good I perceived a particular set of phones, changing some phones from a 4 to 8.5... you get the idea.
With the UFO transformers which have scary flat and ridiculously wide frequency response, there is little else that could be done to improve the sound. Replacing the 6.8K 2 watt resistor feeding the input stage with a vacuum diode such as the VR75 would probably improve things a bit, as it did with the Zen Triode Mono's that we sold for a period of time. So we'll see, maybe I'll revisit this on the SE84UFO2 someday and see if it's worth the effort. As I'm sure many can relate to... when things sound this good, the motivation or drive to make it better is barely there. If someone came in here with a competitors 2 watt amp that
spanked our Zen Triode for a similar price... that would certainly create the drive, but it just hasn't happened... and it's been 20 years and counting.
Hell, it took 20 years to push myself into the UFO territory (which is competitive with the most expensive boutique
transformers ) because I thought we were at that point of diminishing returns already. Clearly I was wrong, and when being wrong sounds this good, you have to wonder what happens when you're right?
Despite what the world loves to say about the octal input tubes, there is an advantage to the 9 pin dual triode. The advantage is having a relatively exactly matched signature on each channel when the circuit uses each triode section for the left & right channels as is the case with the Zen Triode SE84UFO and UFO2. A single tube does both channels so it is impossible to ruin the precision of the Zen's imaging with miss matched tubes. Instead the certainly of a single tube doing both channels make tube rolling a very productive and cost effective experience. The output stage can not be improved upon with different tubes... just make sure they match. There is nothing better than the military top grade 6P15P-EB with plated pins and gold grids. I would rather have one of those than a WE300B in the wood box for the same price as a Zen amp... and that's the beauty of this hobby, getting more from less.