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. 




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.

Yup. Wires, transformers, and 1930's vintage tubes. That's the entire signal path, from preamp input to speakers.

Typo above, choke loaded is clearly not RC coupled, but rather LC coupled, sorry.  At any rate, full interstage transformer coupling was easily the best sounding.

Which returned the Blackbird to the original Karna topology, with far superior power supplies, and the luxury of interstage transformers specifically designed for the Blackbird amplifier.

I give Don full credit for doggedly trying every possible form of coupling, optimizing each circuit with the most favorable operating point, and giving it a serious, I’d even say exhaustive, evaluation. While I sat back with original 20-year-old Karna circuit and criticized from afar. I’m sure I annoyed the hell out of Don more than once.

The selection of an IT for the output section is obvious. The driver, which has to swing a lot of volts at very low distortion, gets to transfer all of its power to the DHT grids. If the DHT grid swings into Class A2 and starts drawing current, no big deal. The power is there, and there are no caps to charge or discharge. Recovery time is instantaneous, unlike RC or LC coupling, and there no risk of DC-coupled failure propagating from driver to output, as there is in solid-state equipment. It really is ideal.

The input tube was another question. In principle, at the lower working voltages, there shouldn’t be much difference between any of the methods, with RC coupling as the obvious and cheapest method. Unfortunately, that’s exactly what it sounds like.

The more serious auditioning over the last year was between current-source + cap coupling, inductor loading + cap coupling (LC), and straight transformer coupling, with no coupling caps or grid resistors involved. And that sounded the best.

Also the simplest. Six parts ... two custom inductors, two good-sized and quite expensive caps, and two grid resistors ... are replaced by one reasonably compact, purpose-designed transformer. The folks who own the "shoebox" format amps, as demonstrated at the show, can be upgraded to the new circuit, which actually opens up space under the chassis. All new amps will have the new circuit, of course.

Charles1dad, thanks for the compliment ... much appreciated. Don and I put a lot of work into these seemingly simple amplifiers.

DHT’s had a rather short reign in audio (much longer in transmitting tubes). It was only from the early Twenties ... the dawn of radio ... to the late Thirties. Once the 6L6 and 6V6 came out (they were designed by the same team), that wiped out the 45, 50, 2A3, 300B, 211, and 845. Even Western Electric abandoned the 300B by 1940 when they designed their new generation of amplifiers around push-pull 6L6’s (WE350). Since the 300B first came out in 1935, it wasn’t in favor all that long.

300B’s have now been in production longer than they were in the Thirties and Forties, rather odd when you think about it. It was the vogue in Japan, Europe, and finally the USA in the Nineties that created the continuing demand for the type and DHT’s in general. It’s been thirty years now, so I think it’s safe to say they are here to stay, along with their pentode cousins.

Class D GaN amplifiers will continue to erode Class AB transistor amplifiers, but I think vacuum-tube amps have an enduring appeal that continues to grow. They now dominate high-end audio, which was not true thirty years ago. I remember going to some CES shows with hardly any tube amps at all, never mind DHT’s, and now they are everywhere.

Now you see quality record players, and tube amps, in movies as a marker of good taste. The movie viewer gets a little buzz when the tonearm descends into the groove, making that distinctive vinyl "click" sound, then you see a tube amp quietly glowing in the background, and wonderful music comes out. The camera pulls back, and you see the protagonist, looking contemplative, and out-of-focus city lights in the background. That alone sets a mood.

I’m really pleased about this. In an era of superb all-digital, all-solid-state 4K HDR video, tube amps continue to make new friends because they sound so good, on all types of music.