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.
Hi @lynn_olson , Thank you for the detailed lecture about tubes! Here is Shishido version with 300B. No DC on secondary of IT. 300B is in a regular cathode bias. http://www.vestnikara.spb.ru/vestn/n4/shishido1.gif What do you think about SRPP is this schematics? |
Investigated in some depth in this 1997 Glass Audio article by Matt Kamna (designer of the Whammerdyne 2A3 amplifier) and myself: We found that transformer coupling had the most favorable distribution of harmonics ... by that, the smoothest and fastest drop off. Other forms had more harmonics, with more uneven distribution. Test conditions: 6SN7, single section, 50V rms out, with several different circuits, with and without cathode bypass capacitors. Noise floor with this setup was -118 dB, and harmonics out to the 11th were investigated. To my knowledge, this was the most thorough examination of vacuum tube harmonic generation at the time, using direct measurement instead of reliance on tube models. Standard assumptions about local feedback from cathode degeneration, and SRPP distortion cancellation, were proven wrong. RC coupling, in particular, was shown to have quite high distortion, while transformer coupling was the lowest. |
Direct coupling would have no effect on tube loading, which is responsible for the spectra shown. If we were to re-do the article, we’d try a MOSFET cascode current source load, as well as transformer coupling, SRPP, and RC coupling. We were surprised that cathode degeneration doesn’t work, and creates some nasty high-order terms instead. Separating the data into even and odd-order terms was essential to unscrambling the chaotic results of the spreadsheet ... a legitimate way of looking at the data, since the underlying transfer curves of odd-order (S-shaped) and even-order (C-shaped) distortion are fundamentally different. Nowadays, we have the computer power to discover the actual shape of the input/output transfer curve, and exaggerate it enough to be visible. The regrettable drawback of FFT spectral information is that phase is usually discarded, so the underlying transfer shape cannot be found (although it can be inferred). (What I mean by this is the phase of the distortion harmonics is important. For example, a square wave and a triangle wave look exactly the same on an FFT spectral display; the only difference is the phase of the harmonics. The magnitudes are the same. In real circuits, square waves and triangle waves are created by entirely different mechanisms, so this is important data.) |
Which is why, on my highly resolving system, I could clearly hear the differences between CCS loaded RC coupled, choke loaded RC coupled, and interstage coupled versions of essentially the exact same amplifier. IT coupling won hands down in all areas and is the way these amps are built. The preamp too. No RC coupling anywhere in the signal path.... Of course you need really good transformers.....which has taken a year. |
