I agree with Lynn in that I won’t work with power supplies over 550-600V. The teflon mil spec wire is all rated at 600-630V so you would have to source 1200V wire for headroom. All normal parts are rated at 630V so you would have to source special caps, resistors, etc... You don’t mess around with 1000V or you will have a fire. Also the transformer set in these mono amps including the custom interstage transformers and choke would eat up most of your budget. I like some Lundahl iron, but I found that their IT started ringing above 15KHz in my circuit, so you would most likely have to get custom iron to do your project as I did. So yes, you could certainly build the project you discuss, but it isn’t simple, there are lots of issues and sourcing of custom parts rated for 1kV and if you use Edcor or Hammond iron you or something else of that ilk you will get medium grade amp, not one that has incredible detail and sounds alive. So if you build that amp with $2000 worth of parts you may be able to do it, but if you spend a lot more you will get a much better amplifier. You will still have a fire risk if you don’t make sure every single part in there that sees high voltage is running at no more that 70-75% of its rating. Easy to do at 500V, but a lot harder at 1000V.
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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I use Tubes that also run quite hot, the Amp's these tunes are utilised in are positioned in free space away from other Structures within the room. I have in the past owned a Portable Air Conditioner Unit, that produced Icy Cold Air, this has been reserved for use when the External Temp's are getting up to the +25 Centigrade to help with sleeping. When using the room the system is set up in during these periods of high Temp's, I have never felt there was a need to run the Portable AC Unit during a listening session. If increasing Room Temp's are a concern, as a result of a Tube Amp' being used, and a Cooling Device is at hand, cooling the Room in advance of the listening session is certainly going to cool the room and not impact on the Sound being produced. My cautionary advice to an individual interested in using Tube Devices is no different to the advisories I was given many years past, which is to make sure there is always 'eyes on' the devices in use for the bulk of the time they are Powered On, and have a revisit shortly after being Powered Off. After approx' 30 Years of using Tube Devices, I have not had a concerning experience, only the oddity of a electrical glitch, a spent Valve or a blown fuse. |
Hi @donsachs @lynn_olson ,
I have 300B SET with 6f6 driver in triode mode. I did 2nd harmonic distortion calculation using 3 point method and 6f6 plate characteristic graph. So with RC coupling that I have right now I get more than 2% distortions with voltage swing 140v pick to pick and when I go to interstage transformer coupling I can get around 0.7% distortions with 160v pick to pick. The difference is huge! I have a couple of question about using transformer. Do you use load a resistor after the interstage transformer? What kind resistors do you use? I'm going to use Hashimoto A-305 transformers. As I understand Hashimoto recommends 100K load resistor for this transformer. Regards, Alex. |
Hi I am sorry, but I am not giving anything about the design of the amp away. I had ITs custom wound for the project. My amp is PP, but if you need a load resistor with your circuit then I would try two kinds. A good quality wirewound of sufficient rating, and a good old Kiwame 2W or 5W depending on what you need. I usually use wirewounds, and not cheap ones, but Ohmite or Vishay or something else of quality. Which you prefer will depend on the circuit, your ear, and the Hashimoto iron. The resistors are cheap so try both kinds and see what you think. |
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