Hi @lynn_olson @donsachs
When did you play with the driver tube to your amplifier? Which tubes did you try except 6v6 and kt88?
Did you try 5881, KT66, 6L6, EL34?
If yes can you compare the sound of these drivers?
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.
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I left the driver tuning up to Don Sachs, who’s been building PP pentode amps for decades ... and started out by restoring Citation I and II’s, which are notorious as the most complex amps and preamps of the Golden Age. By contrast, the Marantz amps and preamps were much simpler. Don’s a big fan of the 6V6, 6L6, and KT88 (in triode mode). Kind of hard to argue with that ... some of the most famous amps ever made used those tubes. Anyway ... he tried about every well-known tube under the sun as drivers. I kind of thought something as petite as a 6V6 (which is equivalent to a 45 in ratings) would be optimal, but the KT88, running at fairly high bias, sounded best of all. Part of the reason this is relevant is the 300B is very, very sensitive to the driver tube, much more so than most tubes. The 300B has a difficult combination of very low inherent distortion (bested only by a 45 triode), and a grid-drive requirement of 80 volts peak at very low distortion. In most commercial 300B amplifiers, all you hear is the distortion of the driver, especially if it is RC-connected. You never hear the 300B as it really is. All the usual complaints of dull, soggy sound are the result of a not-good-enough driver. Get a powerful enough driver with enough current (30 mA or more) and transformer couple it to the 300B grid, and you hear a very different sound ... very fast thanks to the high slew rate, and very wide-open thanks to low inherent distortion. Yes, I know about the Sakuma-san 300B - 300B amplifier ... I met him and heard it at one the last VSAC shows in Silverdale. The Sakuma sound is mostly about the Tamura interstage transformers he favors, along with unique tube combinations. Surprisingly, my own Amity and Karna amps sound nothing at all like Sakuma designs ... if anything, our designs kind of echo the Citation I and II ... a big, fast, American sound, like a track-ready V8 Corvette. Sakuma would be more like a Morgan, very vintage. Sakuma is 100% right about interstage transformer coupling. All the flavor comes through ... this is the unique hallmark of any interstage coupled amplifier. You hear it instantly, as soon as you walk in the demo room. Other methods subtly degrade tone colors, and all capacitors have an annoying tone color that is always there. I wish I knew what causes it, but it is not there in the cap measurements, unfortunately. But is very obvious when it is gone, especially after you get the last cap out of the signal chain. Don and I valiantly tried to use various types of RC coupling between the input section and driver, some better than others, but the cap coloration was always there, no matter how fancy the cap was. They were all colored sounding, in various degrees, and a little dynamically flattened. So we had our transformer designer come up with a one-of-a-kind interstage to couple the input to the driver tube, and boom, problem solved. Simpler circuit, too. No caps in the signal path any more, and all the tone colors coming through ... which is the whole point of any vacuum tube amplifier. |
The takeaway is that is impossible to "overdrive" the 300B. By contrast, a charmer like an EL84 can be driven with a whisper ... even a 12AX7 biased at 1 mA will sound good as a driver (which doesn’t work with any other power tube). A classic Mullard circuit is ideal for a pair of EL84’s since they are so easy to drive. 6L6's take a bit more muscle, so 6SN7's are a better choice. The 300B is the opposite. A high voltage, high current, and ultra low distortion driver is mandatory, otherwise you never hear the 300B. You just get murk. 45’s and 2A3’s are a bit less temperamental, thankfully, with the 45 shining through with extremely low distortion. |
Diar @lynn_olson Thanks for the informative answer. I used a 6f6 driver in my single-ended amplifier, which I have been improving for many years. For some reason, Shindo used this tube in the driver of his 300V amplifier, and the person who made the first version of my amplifier followed in his footsteps. That guy (who built my amplifier) also tried to compensate for 300b 2nd order distortions by 6f6 driver distortions. But I don't think it worked. In the end I increased 6f6 current to make it work in a more linear range.
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@lynn_olson how could Don Sachs have been building pp amps for decades when he first owned a tube amp in 2004? |
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