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. 

 

 

whitestix

OK, I didn’t know how much Don was keeping under wraps, so I was a little vague about our continued progress.

The new full-size chassis of the Blackbird (compared to the models at the show) gives us the freedom to "open up" the Blackbird ... ultra performance caps in critical locations, a bit of Raven tech in the front end, and more rigorous isolation between the high-voltage power supply and the audio circuitry. All of these need more room, which is why the production chassis will be 18" wide. Sonically ... well, I haven’t heard it yet, but they’re all good things that move in the same direction as the past year of collaboration.

One the things about the Raven/Karna/Blackbird that is frustrating, but also very gratifying, is the circuit is extremely transparent and revealing. The frustrating part is that parts quality is revealed in a relentless glare, at least in the critical nodes of the circuit. This is the downside of any zero-feedback design; there is no clean-up crew of servo feedback to tidy up afterward. You hear things as they are.

But the transparency is also a gift, because "minor" substitutions are immediately apparent in the first minute of listening. I think Don, Cloud, and the rest of the Spatial team will agree on that point. I feel we are fairly close to the upper bound of what the circuit can do, but I keep being surprised.

The Raven, which I had never heard before, took me aback ... that was not what I was expecting. It is super fast and resolved, with sounds flying out of dead-black space. You can practically see the shapes of the notes as they fly by. No exaggeration, no tipped-up HiFi sound, no artificial edge sharpening, but boy, it’s all there. If it was on the recording, you will hear it.

I find it kind of shocking that a late-Twenties Bell Labs/Western Electric telephone repeater, built with modern ultra-wideband parts and quiet MOSFET cascode power supplies, sounds like that. There ain’t nuthin’ retro about the sound at all.

These pictures give me a bit of a chill. It isn’t a Raven, not quite, but it’s pretty dog-gone close. Both date from the Twenties, and they come out of Bell Labs. In the first, note the archaic nomenclature for the direct-heated tubes and the weird little capacitor ... and what the heck is it doing, dragging the lower grid off-center?

Western Electric 7A Repeater Amplifier

This might look familiar - the WE 42A amplifier

Build either with modern parts, and it sounds like it’s from outer space. It’s like discovering a working spaceship under a long-forgotten tomb.

On a more technical level, here’s the relevant discussion, a deep dive into audio archeology:

Western Electric, the Rosetta Stone of Audio

Oh, that wasn’t technical enough for you? Well, chew on this, the way I got my first job at Audionics, by inventing this little gizmo:

Shadow Vector Quadraphonic Decoder

Sadly, only one prototype was ever built, but it did get demonstrated at EMI and the BBC in 1975. After that, loudspeakers, Tektronix, and various magazines.

Believe it or not, there’s a programmer in the UK who actually built this in software a couple of years ago. Now, that’s impressive. The 1975 hardware prototype took nine circuit boards plugged into a backplane ... the UK programming genius took it to the next level, and made it into an eight-band decoder, all working in parallel, thanks to the wonder of modern DSP.

Yes, it is quite surprising how sensitive these two circuits are to parts choices.  Much more so than any I have ever worked with.  I am used to coupling cap differences, and I have my favourite types, but there are several film caps in here that make as much or more difference.  Also, I have been through several versions of anode loading, and it is clear in this circuit that a custom designed interstage transformer walked all over the other choices in the amps.  We developed a new twist on the regulated supplies for the preamp, and now we will extend that idea to the power amp and then we are done.  As Lynn said, I think we are reaching the limits of what the circuits can do.  Also, I am trying the excellent Monolith Magnetics transformers as soon as they arrive.  I will see if this pushes the amps over the top!  As I believe I said earlier in the thread, this is pretty much a cost no object project to see what is possible with these circuits.   They sound unlike anything I have ever heard or worked with.   The better you make them, the less they sound like anything at all, which is about the highest compliment I can give an amp or preamp.