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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
jaytor's avatar
jaytor
765 posts
 

@lynn_olson @donsachs @atmasphere - Thanks for your responses. My system is bi-amped with a SS amp driving the lower three octaves, so I'm primarily concerned about upper bass on up. I'm pretty happy with my current DIY 300B PSET monoblocks, but I like to tinker.

I've primarily been building electronics based on other's designs (at least at the module level), but I've recently been trying my own designs (heavily influenced by others). I think I want to build a PP amp as my next amp, using either 300Bs or 2A3s. My main speakers are pretty sensitive (98db/w line arrays) so I don't need a ton of power. I'm still thinking about what approach I want to take. 

alexberger
904 posts
 

I have a question about the first 6sn7 stage in my 300B SET. What is the best way to make load and coupling?
1. The drawback of the interstage transformers is a narrow bandwidth in combination with 6sn7 that has high internal impedance. But low distortions.
2. RC - coupling has wide bandwidth but higher distortions.
3. LC - coupling looks good, but what is the optimal inductance for 6sn7? The issue can be not deep enough low frequency bandwidth and high LC resonance Q.
4. What are the drawbacks of SRPP with C or direct coupling? What is for and against it?

byang12's avatar
byang12
39 posts
 

@alexberger 

your choice of 6sn7 as driving tube is not good (high output Z, low max plate current...)

Now, your choice 1 of implementation is the better one, only your concern is invalid.

High output Z does not automatically leads to narrow bandwidth.  Bad Interstage transformer causes it.  High Z tube can't drive 300B into deep A2 so you never get 8W  class A output from 300B that way. However, you can use Western electric's classic Ultra path design pattern, combining a CCS with a 0 DC current nickel 1:0.75 interstage transformer and achieve pretty good result if you bi-amp the speaker.

 

atmasphere's avatar
atmasphere
11,794 posts
 

@alexberger The 6SN7 can support fairly high current which is why it can make a good driver tube if used properly. It can also make an excellent voltage amplifier (1st stage of gain) since it is quite linear if used correctly.

SETs usually do not need much gain since the speaker used with the amplifier should be high sensitivity (if a 300b power tube, +100dB is a good value). The 6SN7 will allow plenty of gain for this. One section can be used as the voltage amplifier and the other section the driver.

You should be able to get plenty of bandwidth using a 6SN7 and an interstage transformer! The issue will come down to the quality of the transformer itself.

 

alexberger
904 posts
 

I use 1/2 of 6sn7 in the input stage. The driver stage is the 6f6 tube drives the 300b though interstage transformer. The coupling between 6sn7 and 6f6 is RC with Vcup Cutf capacitors.

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