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. 




Coming back to Earth, I heard the Purifi Class D amplifier at the show. Quite good, and free of the usual transistor Class AB metallic coloration. The Raven preamp would make an excellent match for the Purify, since it is very transparent, has plenty of drive current, and is also an ultra-quality ground and RFI isolator. It might seem like an odd pairing, but for somebody that needs cool-running Class D power, the combo would probably work really well.

However ... the way the Raven is configured now, it can only drive one output at a time, either XLR or RCA. Well, technically it can drive both at once ... no harm is done to the circuit or any parts ... but the load is then unbalanced, with more cable capacitance on one side than the other. So the amp with the balanced inputs will receive a signal that doesn’t quite match at high frequencies.

This is probably true of other preamps with XLR and RCA outputs ... unless the literature comes out and says it has independent and isolated output sections for each set of outputs, you should assume the RCA is simply connected to one side of the XLR output. If that is so, then the added capacitance of the RCA cabling, plus the input capacitance of the RCA power amp, will unbalance the XLR output.

I should also mention when a transistor power amp is turned off, the input section of that amp is not isolated from the cabling, and the turned-off input transistors can create a nonlinear load for the preamp. Once it’s on again, feedback and power is restored, and the amp operates as specified. But when it’s off, best not to have another amp connected in parallel.

This is an important difference between tube power amps and transistor power amps. The input grid of a turned-off tube amp just sits there with a few pF of capacitance from the tube socket. Nothing else happens. It would take hundreds of volts to arc-over the tube, or break something in the input section.

By contrast, the base or gate of the bipolar or JFET transistor has a nonlinear input capacitance that remains when the power is off, and there is serious risk of damage if a 20 volt transient comes by ... this is a real hazard with conventional cap-coupled tube preamps and their associated turn-on thump. (The Raven is transformer-coupled and cannot pass DC transients, but there’s a small click when the VR tubes snap on, but small enough that even the most delicate Lowthers would not be harmed.)


"However ... the way the Raven is configured now, it can only drive one output at a time, either XLR or RCA. Well, technically it can drive both at once ... no harm is done to the circuit or any parts ... but the load is then unbalanced, with more cable capacitance on one side than the other. So the amp with the balanced inputs will receive a signal that doesn’t quite match at high frequencies."


I wonder if this is an issue since the XLR’s are just driving the bass, however this happens with in the internal crossover in the speaker. I spoke with Don on the phone today, getting clarification from Legacy how this works with RCA and XLR together in bi-amp.

Lynn makes note of hearing Purifi Class D amps at the show in a favorable way.   I did hear Atma-Sphere's new GaN mono amps driving the the Tekton Moabs and I thought they sounded excellent.  I could easily see a synergy between the Raven and Ralph's mono amps and I personally would require a tube preamp with any amp I might choose to use.  That Ralph has made such a move to Class D technology after decades of being a tube designer/manufacturer ought to make the audio community sit up and take notice.  What I heard of his $5500 amps was very impressive.  Of course, let your ears be the judge.

I am luxuriating with Don's DS2 preamp and his new 300b monos driving my now run-in Cube Audio Jazzon speakers.   I am enjoying the sound in my room to a degree that I have never experienced before.  From morning to night...   


The Raven is particularly well-suited to driving transistor amps because:

1) The transformers prohibit the transmission of DC pulses to RCA and XLR outputs, under all conditions, including total failure.

2) Unlike solid-state preamps, there are no DC servos to fail. There are no coupling caps on the output to store turn-on pulses, unlike cathode-follower designs. No muting relays are needed, or used, so the signal path is direct from transformer secondary to output.

3) All internal circuitry is fully balanced. The faint click when the VR tubes light up is only due to small residual imbalance (no more than 2%) in the 6SN7’s. Balanced operation alone reduces noise by 30 to 35 dB, then the VR tubes another 20 dB, and then 130 dB from the regulated power supply.

4) In addition to internal balanced operation, phase splitting at the input and output is entirely passive, not using discrete transistors, op-amp inverters, or split-load tube inverters. The custom transformers are precision balanced through 30 kHz, ensuring accurate phase balance for the power amplifier, whether it is solid-state or vacuum tube.

5) The input connections are floating, breaking any potential ground loops from the DAC or phono preamp. The transformers only respond to differences between signal pairs, with 80 dB or better common-mode noise rejection. The transformers also reject radio-frequency interference (RFI), passing only audio-band signals.

My personal award show notes from PAF, including the room with the amp in this thread:

*Most intensely rich yet detailed tubey midrange: LTA prototype DAC,  LTA Pre, LTA Ultralinear+ monoblocks, and Daedalus Argos V3 speakers

*Most delicate and intricately revealing top end with too much mid-bass: VAC components and Von Schweikert Ultra 7 speakers

*Second place for best top end and also clear midrange but garbled bass: Songer + Whammerdyne

*Most gossamer presentation: Don Sachs' Raven/Blackbird + Spatial Audio Lab X series speakers

*Largest sounding very small, yet full range speakers: Gershman

*Most humongously oversized images and stage and most impressive driver tech: Aavik/Ansus and Borreson M6

*Most resonant enclosures: Black Ocean Audio

*Most disappointing tonality: Joseph Audio Pearl Graphene speakers

*Biggest surprise: Vanatoo's little office stereo sized powered speakers

*Friendliest exhibitor reps: Tie between Furutech and ASC

*Most advantaged by vibration control: Millercarbon

*Most classic solid state sounding room: Infigo Audio

*Most inoffensive yet not all that unique sounding room: Bella Sound