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. 




@downtheline  The Raven has a headphone jack, yes, but as Lynn noted, it will only drive the typical old style phones.  It will not drive planars.  Sounds great with my old Sennheisers and phones of that type with 300 ohm impedance.  

As an overview, the Raven is a 1-stage amplifier with a 4.5:1 step-down transformer, and is output-limited by what both sections of a 6SN7 can crank out. The Blackbird is a 3-stage amplifier with a 28.7:1 step-down transformer, and is output-limited by what a pair of 300B’s can crank out.

The ideal solution for planar headphones is a 2-stage amplifier. For example, in the xDuoo TA-10R headphone amp sitting right next to me, a 12AU7 followed by a pair of Class A emitter-followers for each channel. Simple and inexpensive. Or, small power amplifiers in the 2 to 5 watt range ... all transistor, hybrid, or all-tube. The all-tube solutions ideally use step-down (output) transformers to match the load to the capabilities of the output tube.

Vacuum tubes can swing lots (hundreds) of volts, but are current-limited by peak cathode emission, typically measured in tens of milliamps, not amps. Bipolar and MOSFET transistors, in contrast, can pass not just milliamperes, but several amps, which is why they can be direct-connected to low-impedance devices like 8-ohm speakers and 20-ohm headphones.

A quick note on transformers: the voltage/current transformation ratio is the same as the turns ratio, but the impedance ratio is the square of the turns ratio. For example, the output transformer of the Blackbird, and many other other push-pull amplifiers, has a primary impedance of 6600 ohms, and a secondary impedance of 8 ohms. 6600/8 = 825, and the square root of 825 is 28.7228, which is close to the physical turns ratio. In a well-designed transformer, total losses are less than 5%, so can be neglected for this calculation.

So the output transformer of the Blackbird multiplies the peak current of the 300B pair by 28.7 times, offering peak currents of several amps to the loudspeaker. Similarly, the output transformer of the Raven multiplies the peak current of the 6SN7 by 4.5 times, which is plenty for driving a cable, but not really enough for planar headphones which mimic loudspeakers in terms of current draw.

Sounds like the next project for your collaboration is a headphone amp for a wide impedance range of headphones!

@downtheline Actually, next up is a two stage amp with another lovely DHT in push pull for a whopping 3-4 watts at very low distortion.  Not a 300b so not for this thread!  You could hang a custom transformer off it for phones.  You would want a REALLY good custom little transformer for headphones.  Not some off the shelf average quality solution.  Anything worth doing is worth doing to excess.  It would work and drive darn near any cans you would want to plug in.  You could even have multiple windings and perhaps a switch or two output jacks.  One for 300-600 ohm cans and one for the planar crowd.   Maybe in a few months..  First we get the Blackbirds and Raven off the ground (pun intended).  We have just built the first ones in Utah and I expect sales in Feb.  Then I can focus on other projects....