300b lovers
I have been an owner of Don Sachs gear since he began, and he modified all my HK Citation gear before he came out with his own creations. I bought a Willsenton 300b integrated amp and was smitten with the sound of it, inexpensive as it is. Don told me that he was designing a 300b amp with the legendary Lynn Olson and lo and behold, I got one of his early pair of pre-production mono-blocks recently, driving Spatial Audio M5 Triode Masters.
Now with a week on the amp, I am eager to say that these 300b amps are simply sensational, creating a sound that brings the musicians right into my listening room with a palpable presence. They create the most open vidid presentation to the music -- they are neither warm nor cool, just uncannily true to the source of the music. They replace his excellent Kootai KT88 which I was dubious about being bettered by anything, but these amps are just outstanding. Don is nearing production of a successor to his highly regard DS2 preamp, which also will have a unique circuitry to mate with his 300b monos via XLR connections. Don explained the sonic benefits of this design and it went over my head, but clearly these designs are well though out.. my ears confirm it.
I have been an audiophile for nearly 50 years having had a boatload of electronics during that time, but I personally have never heard such a realistic presentation to my music as I am hearing with these 300b monos in my system. 300b tubes lend themselves to realistic music reproduction as my Willsenton 300b integrated amps informed me, but Don's 300b amps are in a entirely different realm. Of course, 300b amps favor efficient speakers so carefully component matching is paramount.
Don is working out a business arrangement to have his electronics built by an American audio firm so they will soon be more widely available to the public. Don will be attending the Seattle Audio Show in June in the Spatial Audio room where the speakers will be driven by his 300b monos and his preamp, with digital conversion with the outstanding Lampizator Pacific tube DAC. I will be there to hear what I expect to be an outstanding sonic presentation.
To allay any questions about the cost of Don's 300b mono, I do not have an answer.
@charles1dad Such is the nature of the internet I suppose, where fact and opinion freely co-mingle. The physical nature of SET transformers are governed by physical law FWIW and that law isn't interested or caring about opinion. It simply is. |
Since the 300B fits into the KT88 ecosystem, the same choices for power and output transformer apply, except you’re not messing with ultralinear connections, and some thought (well, a lot of thought) needs to be applied to the filament circuit, which is a very critical node sonically. I agree about the output transformer. That’s the make-or-break part. Fortunately, we have many good PP output transformers, going back to the Partridge in 1948. Lots of good ones today, too, as long as they are PP and you specify the allowable offset current. The SE world has not quite as many choices, but there are still lots of vendors making good parts these days. Many more than the Nineties. The interstage is tougher. There are fewer choices, and it is a more difficult design assignment, since impedances are higher than the output transformer. Don’s industry connections came in very handy here, so we had a custom unit designed for us, with outstanding performance. The original Karna had two interstages, which was frankly over-the-top. Requirements for the first one bordered on impossible, since impedance from the first tube was much higher than the driver. When I switched over to the 6SN7, I decided enough was enough, and went with simpler inductor loading instead. |
I love the candor. Charles |
My PP 845 Mono's are produced with a optimised performance for the 845, they are Low Wattage approx' 25 Watts when the VU Metre at Biasing is set to 12.5, I have been informed I can push the Watt Output Up if I increase the Bias, but the Trade Off is a reduction in the Head Room, in the past I played with Bias, but the Headroom when perceived is quite addictive as a trait of the Amp. These Amps have Hand Wound Output and Power Tranx's, the designer/builder has informed me recently, that even though there are increased options for Tranx's since this Amp' was designed, there is not an off the shelf winding that they are aware of, that is readily available to suit the Amp's design. |
I’m not surprised. The great enemy of transformers are high impedance, which decreases bandwidth on both ends of the spectrum, and increased insulation resistance, which takes up room on the winding stack. Both act to increase the size of the core, the winding stack, and the entire transformer. When transformers get bigger, inter-winding capacitance goes up, and HF bandwidth decreases. Yes, little transformers are better, at least at high frequencies. To get the lows, though, you need more inductance, and that makes it bigger and heavier. The technique to increase HF bandwidth are more complex interleaving schemes between primary and secondary, but this can cause ultrasonic resonances and poor square wave performance. The art of interleaving has fortunately been somewhat simplified by computer modeling, but there’s still plenty of art involved. You want a skilled builder with plenty of experience with audio transformers. There ain’t no free lunch with transformers. They solve problems, but you really have to keep impedances low, and work closely with the transformer designer. They’ll tell you what they want, and you tell them what you want, and you work together to meet your goals. In my case, I wanted matched capacitances on the primaries, good phase match at 20 kHz, and the ability to tolerate a certain amount of imbalance current. With SE, of course, it’s all imbalance current, so a (very) large gapped core is required. A problem with using old transformers is corona discharge where the enamel on the wire has thinned or cracked. Once a point of breakdown occurs, those windings are shorted to each other, and the problem cannot be solved unless the transformer is disassembled and completely rewound using the same interleaving scheme. New transformers are commonly tested with HIPOT, a test fixture that generates 5 kV between the windings and the core. |
