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. 




As Lynn mentioned above, we chose the 6SN7 and the 6V6 because both are in current production and there are very good modern versions of each being built.  Obviously there are lots of 300b choices as well.  I favour the Linlai E-6SN7 beause it sounds wonderful and is reasonably priced.  The JJ 6V6 sounds quite good.   I love the old stock Russian black bottle 6V6 in here and you can still get them for reasonable prices out of Ukraine, Romania, and other places without sending money to Russian vendors at this time.  You do need pairs that are within maybe 2 mV of each other for full bass performance in the amp.  Matched pairs of 300b for the same reason.   They are all readily available, and the amp runs tubes at sane operating points so they will last a long time.   We didn't want to produce an amp that required really expensive tubes that could be unobatinium  in a few years.

It has been well debated 20 years ago during golden years of  direct heated power triodes.


Based on tests on ALTEC/JBL horn systems:

300B is middle of the road of all those small/medium signal direct heated tubes.

It has good/mellow middles, lose/weak lows and not very sweet highs. 300B has longest life among those DH tube.

PX25 has best low end quality among all < 8W tubes.

VT25A/10 has best high end, I built and love the sweet sound.  However, the tube is very fragile, did not last.


if you want to best balanced sound, push/pull 45/50 can give you what you need.

For small signal (pre-amp) tubes, 26 sounds the best, and same time is hardest to build the amp due to sensitive to hum and very low heater voltage.

I run 46 tubes in my Lampi Pacific DAC and they are wonderful.   You can still find some.  The 45 is now really scarce unless you want to spend a fortune for new production.   I have some 26 I collected for a potential preamp project.  So many tubes, so little time:)

As mentioned above, the Mark I Karna used a quartet of 45 tubes, but new production is limited at this time, with future availability an open question. Five years from now? Maybe, maybe not. Ten years? Maybe, maybe not. I can only go by popularity in the market and how many different vendors, in different parts of the world, are currently making them. Not just one factory in one country.

For a DIY hobby amp, availability of tubes not a real concern. But if people are buying a commercial product and expect service (warrantees are a legal requirement in the USA and Canada), availability of new-production matched pairs is a major concern. Don and I looked at the market and we both decided, nope, not yet, still a pretty specialized niche product, and NOS and old-stock supplies have all disappeared into the collector market. When the Mark I Karna was built, they were scarce, but could still be found. Now they are very scarce indeed.

As for sonics, for anyone that’s designed an amplifier from scratch, as I have, the sonics of the 300B are largely determined by the linearity and current delivery of the driver stage. Most of the commercial 300B amps I see at hifi shows have driver stages that are under-designed by a factor of 2 or 3, which results in not enough current to drive the Miller capacitance of the 300B grid. They aren’t as hard to drive as an 845, which is nearly impossible, but they are only second to an 845. A good driver needs high current, high linearity, high speed, and enough headroom to drive the grid 20 volts positive and then recover in microseconds.

Most drivers can’t do that, so the driver and output both clip at the same time, and then both have different recovery times, which can last an appreciable fraction of a second for RC-coupled amps. A typical SET will have RC isolation for the B+ supply between stages, and that RC filter has a characteristic recovery time once a stage saturates. So four things have to recover after saturation: the RC coupling between stages, the RC isolation B+ filter between stages, and cathode bypass caps for each of the cathodes. Typically, they all have different recovery times. Then we get into the subtler issues of capacitor coloration, which can overshadow tube coloration if the caps are not well-chosen.

Most of the "sound" of a conventional SET amp is simply a driver that has run out of linearity. The same is true of preamps, by the way. They run out of linear current to drive the interconnect cable capacitance and then the power supply folds down as it is saturated.