2. amps-preamps
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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
alexberger
863 posts
 

Hi @donsachs ,

Thank you for good words and help.

My next project will be a phonostage. I have a DIY phonostage I built in 2011 based on EAR834p schematics. In my phonostage I used better parts (air capacitors) and power supply (with LCLC power filter and 0A2 shunt stabilizers).
In my next phonostage I want to make an external power supply with a separate filament transformer. But I haven't decided which RIAA schematics to use. There are basically two types of tube phonostages. In one type RIAA is implemented in feedback and another type is passive RIAA. What are the advantages and disadvantages of these two approaches?

donsachs's avatar
donsachs
245 posts
 

My only experience is two builds with passive RIAA.  They sounded good, but I have not experimented with the other type, sorry.

donsachs's avatar
donsachs
245 posts
 

Also, I am considering a build of Thomas Mayer's octal phono schematic with my own power supply choices.  One of those things I may eventually get around to....  You have probably looked at that schematic, but if not, perhaps google it

atmasphere's avatar
atmasphere
11,615 posts
 

In my next phonostage I want to make an external power supply with a separate filament transformer. But I haven't decided which RIAA schematics to use. There are basically two types of tube phonostages. In one type RIAA is implemented in feedback and another type is passive RIAA.

@alexberger You might consider that since the cartridge is a balanced source that you could have a balanced phono section too, or at least a balanced input. If you run EQ via feedback, you run into the same problem that Norman Crowhurst wrote about nearly 70 years ago. You could avoid it by applying the feedback to the grid of the tube rather than the cathode (you'll need a series resistor with the input to allow the mixing to occur, similar to an opamp circuit). You'll have to recalculate all the EQ values since feedback to the grid behaves quite differently (higher impedance).

Passive feedback can work quite well. Just because you have passive EQ does not mean that you can't run feedback in the associated gain stages. H/K did this with their Citation 1 back in 1958.

The advantage tubes have over solid state in a phono section has to do with the fact that most cartridges are inductors; when in parallel with the capacitance of the tonearm cable, an electrical resonance is formed. That resonance can overload the input of the phono section causing ticks and pops that sound like they are on the LP surface. If your tube phono section is properly designed (easier because the operating voltages are higher), this won't happen; you may discover that LP surfaces are actually a lot quieter than the digital crowd would have you believe.

donsachs's avatar
donsachs
245 posts
 

I rebuilt a number citation 1 preamps over the years for customers.  I didn't care much for the line stage section with the anode follower, and miles of wire and switches, but the phono section was among the best of the vintage gear.  

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