From Don Sachs:
"First pair of production Blackbirds in walnut... running and sounding really good for only 10 minutes on them :)
Tomorrow we start the first pair of production Ravens...."
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.
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@alexberger I can confirm everything @lynn_olson mentioned regarding your post in his above. Pay attention to all those issues! Regarding this question which has to do with grounding. You’ll want to ground your chassis if its metal (and if you’re running single-ended, ferrous materials will provide audio-frequency shielding). So the ground connection of the power cord should be tied to the chassis. The audio circuit, if tied directly to chassis, leaves you open to ground loops. To avoid this, lay out your amplifier circuit so all the points that go to ground do so to the power supply (star grounding is nice) without touching the chassis. Grid and cathode connections for each tube section (the ground side of the grid resistor and ground side of the cathode resistor) should be common and use a single wire going to the star ground. This forces noise imposed in that wire to be common mode and so will reduce noise. The spot in the power supply to which you tie your grounds can be a buss tying all the filter cap grounds together. Once you have all the grounds starred together, at that point you need to reference the chassis ground. That can be done several ways: you can use a simple resistor from the audio ground to chassis ground. You can use a pair of rectifiers in parallel, each opposite of the other, with a resistor in parallel with that. This higher impedance is presented to ground currents between chassis and the audio grounds which otherwise set up the ground loop. Be sure to have the input connectors also isolated from ground. Most RCA connectors are supplied with shoulder washers for this purpose. In this way, the chassis can be a relatively quiet shield for the audio circuit. You’ll find the audio circuit to be quieter with this practice. |
Hi @lynn_olson @atmasphere , Thank you for useful information. Does aluminum provides any shielding? I will use an aluminum chassis. There is a beautiful picture of Blackbirds. But I don't see inter-stage transformers. Are they under the hood?
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@alexberger Yes, but only at radio frequencies. No shielding at audio frequencies, and for that reason steel is likely a better choice if you're running single-ended. We use aluminum chassis in most of our stuff, but its balanced and so does not need shielding to be quiet. |
Alexberger, the Cinemag input and interstage transformers are under the top plate. These are the third generation of the custom Cinemag transformers we started with. The two Monolith transformers are visible on the rear of the top plate. The other things under the top plate (right side) are the B+ and filament regulators, and the master soft-start circuit, with an external 12V trigger. The point-to-point and turret-board wiring under the audio side (left) is very simple, with only transformers, tube sockets, cathode resistors and bypass caps. No current sources or other gizmos. |
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