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 Don,

I have always wanted a 300B system. Two quick questions. I currently have a pair of KEF Reference 5 speakers @91db. How well will your 300b power them? And can you give me a ballpark price so I can start groveling to She Who Must be obeyed?😁

Thanks in advance.


A good way to visualize the difference between even and odd-order distortion harmonics is to imagine a sine wave ... a perfect, happy little sine wave. That's the original signal.

* Now, use a single diode to clip one side of it ... say, the positive side. In addition to generating a DC offset, if you run a spectral analysis of it, you'll see a series of harmonics ... 2nd, 4th, 6th, etc. etc. If you look at the "transfer curve" ... a curve mapping the input/ratio at different levels ... you'll see a diagonal line that is perfectly straight (the linear portion) that also has a sharp bend in it at the top, with a flat-topped region beyond the bend. The transfer curve is actually the true distortion mechanism; the spectral analysis of it is an indirect indicator that is (relatively) easy to measure.

* Let's use two diodes to clip the top and bottom sides, both positive and negative. This is known as symmetric clipping. If the flat-topping is at exactly matched levels, there will no DC offset. Similarly, if the clipping is precisely symmetric, the spectral analysis now shows no even-order terms (2nd, 4th, 6th, etc) but only odd-order (3rd, 5th, 7th, etc.). The transfer curve now has TWO kinks in it, at matching plus and minus signal levels. If the levels precisely match, there will be no even-order terms, but odd-order terms are abundant.

The diodes create hard clipping. Vacuum tubes, properly biased, create a softer "knee" region, but rest assured distortion is still there, just not as much, and with less high-order content. The property of symmetric circuits is they cancel transfer curves that are precisely opposite in shape ... a "C" shape that is inverted in the other phase of the circuit. But that depends on symmetry and precise phasing that tracks as levels go up and down.


The speakers appear to be 8 ohm 90 dB from a stereophile review.  They dip to 3.2 ohms, which isn't bad.  The amps would drive them with no trouble in any reasonable sized room.  I cannot comment on pricing until Spatial Audio figures out all of their costs.  I would expect $15,000 - 20,000 per pair with premium tubes, but that might be off a bit.  There will be an announcement after the Seattle show in the spatial audio lab website once it is all figured out.

Hi, CuriousJim!

I am kind of dubious about any KEF speaker being really 91 dB/meter/watt. That’s almost 1% conversion efficiency, and believe it or not, that’s quite high for the mainstream market, and especially KEF. True efficiencies between 85 and 88 dB are much more common. Efficiencies in that range need 100 to 200 watt amplifiers, which is very large for tube amps. When people say XYZ speaker needs 200 watts to "come alive", they are not joking.

1% efficiency is 92 dB/meter/watt. 0.5% is 89 dB/meter/watt. 0.25% is 86 dB/meter/watt. This raises the question ... where does all that power go, if not making sound?

It heats the voice coil, which eventually radiates its heat to the magnet structure, which radiates its heat into the cabinet. Copper increases its resistance with temperature, which leads to a type of dynamic compression as the voice coil heats and cools. In addition, voice coil heating eventually damages the cylindrical former it is wound on, leading to driver failure over time. That’s why Nomex and other fire-resistant materials are commonly used for VC formers.

This is the charm of high efficiency speakers: for a given SPL, much less power is wasted in heating the voice coil. More is turned into sound, which is the goal.

P.S. I agree, it is somewhat annoying to realize that 99%, or more, of the expensive watts we buy do nothing more than heat a voice coil, but that’s what’s really happening. It’s kind of shocking: hundreds of watts from the AC wall socket end up as milliwatts of acoustic power. The rest ends up as heat, and not in a great place, either.


I have to admit that the conclusion about SE+PP leads to emphasis on 5th harmonic is a bit counter-intuitive to me from pure math perspective, but I haven’t read his paper and perhaps there are certain situations that contribute to that conclusion (?).


Many report excellent result using a tube pre with a solid state or push-pull tube power amp though. In many cases, such combination includes some SE stages with at least one PP stage. So, SE+PP is not necessarily bad empirically :-)